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  • 51.
    Björnson, Emil
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Debbah, Merouane
    CentraleSupelec, France.
    Ottersten, Björn
    KTH Royal Institute of Technology.
    Multi-Objective Signal Processing Optimization: The Way to Balance Conflicting Metrics in 5G Systems2014Ingår i: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 31, nr 6, s. 14-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evolution of cellular networks is driven by the dream of ubiquitous wireless connectivity: any data service is instantly accessible everywhere. With each generation of cellular networks, we have moved closer to this wireless dream; first by delivering wireless access to voice communications, then by providing wireless data services, and recently by delivering a Wi-Fi-like experience with wide-area coverage and user mobility management. The support for high data rates has been the main objective in recent years [1], as seen from the academic focus on sum-rate optimization and the efforts from standardization bodies to meet the peak rate requirements specified in IMT-Advanced. In contrast, a variety of metrics/objectives are put forward in the technological preparations for fifth-generation (5G) networks: higher peak rates, improved coverage with uniform user experience, higher reliability and lower latency, better energy efficiency (EE), lower-cost user devices and services, better scalability with number of devices, etc. These multiple objectives are coupled, often in a conflicting manner such that improvements in one objective lead to degradation in the other objectives. Hence, the design of future networks calls for new optimization tools that properly handle the existence of multiple objectives and tradeoffs between them.

  • 52.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    Random Access Protocol for Massive MIMO: Strongest-User Collision Resolution (SUCR)2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2016, s. 820-825Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless networks with many antennas at the base stations and multiplexing of many users, known as Massive MIMO systems, are key to handle the rapid growth of data traffic. As the number of users increases, the random access in contemporary networks will be flooded by user collisions. In this paper, we propose a reengineered random access protocol, coined strongest-user collision resolution (SUCR). It exploits the channel hardening feature of Massive MIMO channels to enable each user to detect collisions, determine how strong the contenders channels are, and only keep transmitting if it has the strongest channel gain. The proposed SUCR protocol can quickly and distributively resolve the vast majority of all pilot collisions.

  • 53.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    A Random Access Protocol for Pilot Allocation in Crowded Massive MIMO Systems2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 4, s. 2220-2234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The massive multiple-input multiple-output (MIMO) technology has great potential to manage the rapid growth of wireless data traffic. Massive MIMO achieves tremendous spectral efficiency by spatial multiplexing many tens of user equipments (UEs). These gains are only achieved in practice if many more UEs can connect efficiently to the network than today. As the number of UEs increases, while each UE intermittently accesses the network, the random access functionality becomes essential to share the limited number of pilots among the UEs. In this paper, we revisit the random access problem in the Massive MIMO context and develop a reengineered protocol, termed strongest-user collision resolution (SUCRe). An accessing UE asks for a dedicated pilot by sending an uncoordinated random access pilot, with a risk that other UEs send the same pilot. The favorable propagation of massive MIMO channels is utilized to enable distributed collision detection at each UE, thereby determining the strength of the contenders signals and deciding to repeat the pilot if the UE judges that its signal at the receiver is the strongest. The SUCRe protocol resolves the vast majority of all pilot collisions in crowded urban scenarios and continues to admit UEs efficiently in overloaded networks.

  • 54.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Hoydis, Jakob
    Nokia Bell Labs, France.
    Sanguinetti, Luca
    University of Pisa, Italy / CentraleSupelec, France.
    Massive MIMO Networks: spectral, energy, and hardware efficiency2018Bok (Refereegranskat)
    Abstract [en]

    Massive multiple-input multiple-output (Massive MIMO) is the latest technology that will improve the speed and throughput of wireless communication systems for years to come. Whilst there may be some debate over the origins of the term Massive MIMO and what it precisely means, this monograph describes in detail how the research conducted in the past decades lead to a scalable multiantenna technology that offers great throughput and energy efficiency under practical conditions. Written for students, practicing engineers and researchers who want to learn the conceptual and analytical foundations of Massive MIMO, in terms of spectral, energy, and/or hardware efficiency, as well as channel estimation and practical considerations, it provides a clear and tutorial like exposition of all the major topics. It also connects the dots of the research literature covering numerous topics not easily found therein. Massive MIMO Networks is the first monograph on the subject to cover the spatial chan el correlation and consider rigorous signal processing design essential for the complete understanding by its target audience.

  • 55.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    How Energy-Efficient Can a Wireless Communication System Become?2018Ingår i: 2018 CONFERENCE RECORD OF 52ND ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS, AND COMPUTERS, IEEE , 2018, s. 1252-1256Konferensbidrag (Refereegranskat)
    Abstract [en]

    The data traffic in wireless networks is steadily growing. The long-term trend follows Coopers law, where the traffic is doubled every Two-and-a-half year, and it will likely continue for decades to come. The data transmission is tightly connected with the energy consumption in the power amplifiers, transceiver hardware, and baseband processing. The relation is captured by the energy efficiency metric, measured in bit/Joule, which describes how much energy is consumed per correctly received information hit. While the data rate is fundamentally limited by the channel capacity, there is currently no clear understanding of how energy-efficient a communication system can become. Current research papers typically present values on the order of 10Mbit/Joule, while previous network generations seem to operate at energy efficiencies on the order of 10 kbit/Joule. Is this roughly as energy-efficient future systems (5G and beyond) can become, or are we still far from the physical limits? These questions are answered in this paper. We analyze a different cases representing potential future deployment and hardware characteristics.

  • 56.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Three Practical Aspects of Massive MIMO: Intermittent User Activity, Pilot Synchronism, and Asymmetric Deployment2015Ingår i: 2015 IEEE Globecom Workshops (GC Wkshps), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers three aspects of Massive MIMO (multiple- input multiple-output) communication networks that have received little attention in previous works, but are important to understand when designing and implementing this promising wireless technology. First, we analyze how bursty data traffic behaviors affect the system. Using a probabilistic model for intermittent user activity, we show that the spectral efficiency (SE) scales gracefully with reduced user activity. Then, we make an analytic comparison between synchronous and asynchronous pilot signaling, and prove that the choice between these has no impact on the SE. Finally, we provide an analytical and numerical study of the SE achieved with random network deployment.

  • 57.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Debbah, Merouane
    CentraleSupelec, France.
    Optimizing Multi-Cell Massive MIMO for Spectral Efficiency: How Many Users Should Be Scheduled?2014Ingår i: 2014 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2014, Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 612-616Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive MIMO is a promising technique to increase the spectral efficiency of cellular networks, by deploying antenna arrays with hundreds or thousands of active elements at the base stations and performing coherent beamforming. A common rule-of-thumb is that these systems should have an order of magnitude more antennas, N, than scheduled users, K, because the users' channels are then likely to be quasi-orthogonal. However, it has not been proved that this rule-of-thumb actually maximizes the spectral efficiency. In this paper, we analyze how the optimal number of scheduled users, K*, depends on N and other system parameters. The value of K* in the large-N regime is derived in closed form, while simulations are used to show what happens at finite N, in different interference scenarios, and for different beamforming.

  • 58.
    Björnson, Emil
    et al.
    KTH Royal Institute Technology, Sweden; Supelec, France.
    Matthaiou, Michail
    Chalmers, Sweden; Queens University of Belfast, North Ireland.
    Debbah, Merouane
    CentraleSupelec, France.
    Massive MIMO with Non-Ideal Arbitrary Arrays: Hardware Scaling Laws and Circuit-Aware Design2015Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, nr 8, s. 4353-4368Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Massive multiple-input multiple-output (MIMO) systems are cellular networks where the base stations (BSs) are equipped with unconventionally many antennas, deployed on co-located or distributed arrays. Huge spatial degrees-of-freedom are achieved by coherent processing over these massive arrays, which provide strong signal gains, resilience to imperfect channel knowledge, and low interference. This comes at the price of more infrastructure; the hardware cost and circuit power consumption scale linearly/affinely with the number of BS antennas N  . Hence, the key to cost-efficient deployment of large arrays is low-cost antenna branches with low circuit power, in contrast to today's conventional expensive and power-hungry BS antenna branches. Such low-cost transceivers are prone to hardware imperfections, but it has been conjectured that the huge degrees-of-freedom would bring robustness to such imperfections. We prove this claim for a generalized uplink system with multiplicative phase-drifts, additive distortion noise, and noise amplification. Specifically, we derive closed-form expressions for the user rates and a scaling law that shows how fast the hardware imperfections can increase with N  while maintaining high rates. The connection between this scaling law and the power consumption of different transceiver circuits is rigorously exemplified. This reveals that one can make the circuit power increase as N − −  √   , instead of linearly, by careful circuit-aware system design

  • 59.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Matthaiou, Michail
    Chalmers, Sweden; Queens University of Belfast, North Ireland.
    Pitarokoilis, Antonios
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Distributed Massive MIMO in Cellular Networks: Impact of Imperfect Hardware and Number of Oscillators2015Ingår i: 23rd European Signal Processing Conference, EUSIPCO 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 2436-2440Konferensbidrag (Refereegranskat)
    Abstract [en]

    Distributed massive multiple-input multiple-output (MIMO) combines the array gain of coherent MIMO processing with the proximity gains of distributed antenna setups. In this paper, we analyze how transceiver hardware impairments affect the downlink with maximum ratio transmission. We derive closed-form spectral efficiencies expressions and study their asymptotic behavior as the number of the antennas increases. We prove a scaling law on the hardware quality, which reveals that massive MIMO is resilient to additive distortions, while multiplicative phase noise is a limiting factor. It is also better to have separate oscillators at each antenna than one per BS

  • 60.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. KTH Royal Institute Technology, Sweden; Supelec, France.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Hoydis, Jakob
    Bell Labs, Germany.
    Debbah, Merouane
    CentraleSupelec, France.
    Optimal Design of Energy-Efficient Multi-User MIMO Systems: Is Massive MIMO the Answer?2015Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 14, nr 6, s. 3059-3075Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Assume that a multi-user multiple-input multiple-output (MIMO) system is designed from scratch to uniformly cover a given area with maximal energy efficiency (EE). What are the optimal number of antennas, active users, and transmit power? The aim of this paper is to answer this fundamental question. We consider jointly the uplink and downlink with different processing schemes at the base station and propose a new realistic power consumption model that reveals how the above parameters affect the EE. Closed-form expressions for the EE-optimal value of each parameter, when the other two are fixed, are provided for zero-forcing (ZF) processing in single-cell scenarios. These expressions prove how the parameters interact. For example, in sharp contrast to common belief, the transmit power is found to increase (not to decrease) with the number of antennas. This implies that energy-efficient systems can operate in high signal-to-noise ratio regimes in which interference-suppressing signal processing is mandatory. Numerical and analytical results show that the maximal EE is achieved by a massive MIMO setup wherein hundreds of antennas are deployed to serve a relatively large number of users using ZF processing. The numerical results show the same behavior under imperfect channel state information and in symmetric multi-cell scenarios.

  • 61.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; University of Paris Saclay, France.
    Kountouris, Marios
    Huawei Technology Co Ltd, France.
    Deploying Dense Networks for Maximal Energy Efficiency: Small Cells Meet Massive MIMO2016Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 34, nr 4, s. 832-847Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    What would a cellular network designed for maximal energy efficiency look like? To answer this fundamental question, tools from stochastic geometry are used in this paper to model future cellular networks and obtain a new lower bound on the average uplink spectral efficiency. This enables us to formulate a tractable uplink energy efficiency (EE) maximization problem and solve it analytically with respect to the density of base stations (BSs), the transmit power levels, the number of BS antennas and users per cell, and the pilot reuse factor. The closed-form expressions obtained from this general EE maximization framework provide valuable insights on the interplay between the optimization variables, hardware characteristics, and propagation environment. Small cells are proved to give high EE, but the EE improvement saturates quickly with the BS density. Interestingly, the maximal EE is achieved by also equipping the BSs with multiple antennas and operate in a "massive MIMO" fashion, where the array gain from coherent detection mitigates interference and the multiplexing of many users reduces the energy cost per user.

  • 62.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Kountouris, Marios
    CentraleSupelec, France.
    Designing Wireless Broadband Access for Energy Efficiency: Are Small Cells the Only Answer?2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 136-141Konferensbidrag (Refereegranskat)
  • 63.
    Björnson, Emil
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sanguinetti, Luca
    University of Pisa, Italy; Central Supelec, France.
    Kountouris, Marios
    Huawei Technology Co Ltd, Peoples R China.
    Energy-Efficient Future Wireless Networks: A Marriage between Massive MIMO and Small Cells2015Ingår i: 2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE , 2015, s. 211-215Konferensbidrag (Refereegranskat)
    Abstract [en]

    How would a cellular network designed for high energy efficiency look like? To answer this fundamental question, we model cellular networks using stochastic geometry and optimize the energy efficiency with respect to the density of base stations, the number of antennas and users per cell, the transmit power levels, and the pilot reuse. The highest efficiency is neither achieved by a pure small-cell approach, nor by a pure massive MIMO solution. Interestingly, it is the combination of these approaches that provides the highest energy efficiency; small cells contributes by reducing the propagation losses while massive MIMO enables multiplexing of users with controlled interference.

  • 64.
    Blad, Anton
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Axell, Erik
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Spectrum Sensing of OFDM Signals in the Presence of CFO: New Algorithms and Empirical Evaluation Using USRP2012Ingår i: Proceedings of the 13th IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), IEEE , 2012, s. 159-163Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we consider spectrum sensing of OFDM signals. We deal withthe inevitable problem of a carrier frequency offset, and propose modificationsto some state-of-the-art detectors to cope with that. Moreover, the (modified)detectors are implemented using GNU radio and USRP, and evaluated over aphysical radio channel. Measurements show that all of the evaluated detectorsperform quite well, and the preferred choice of detector depends on thedetection requirements and the radio environment.

  • 65.
    Blom, Rolf
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    An Upper Bound on the Key Equivocation for Pure Ciphers1979Rapport (Övrigt vetenskapligt)
    Abstract [en]

    An upper bound on key equivocation for a pure cipher applied on a memoryless message source is derived.

  • 66.
    Blom, Rolf
    et al.
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Fåk, Viiveke
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Ingemarsson, Ingemar
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Data Network Security: Part I Problem Survey and Model1977Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Data encryption and related methods may be used to preserve information security i n a data network. Here information security is defined as the degree to which the destruction, change or loss of information is presented. Information is defined as the content of the message represented by the data. The information in a block of data is unchanged if the intended result of the transmission of the block is obtained. This means for example that the original message reaches the correct destination where it is interpreted as intended. Undisturbed information does not, in general, require un disturbed data.

    The network is supposed to be a public network, accessed by many different users. We are interested in a well defined group of users who are communicating mainly among themselves. Different groups, however, are also allowed to communicate in a well defined manner. The logical structure of the communication within a group is star-shaped. The information communicated within the groups hall be protected against threats from other users of the network, from illegitimate users (wiretappers etc) and from members in the group. The structure of the threats is described in section 3 of this paper.

    The network itself and the requirement it imposes are supposed to be unchanged. Encryption and decryption are taking place outside the network. The encrypted data shall comply with the requirements of the network. The communication process in the group consists of time-limited messages which are essentially transmitted from one point to another in the network. This is the basis for the model of the communication which is described in section 4. The model, although simple, enables us to structure the problems in connection with encryption/decryption. This is done in section 5 and 6. The purpose of the paper is to form a basis for synthesis of security measures by means on cryptological methods. The analysis is general enough to be applied to any data network and any type of user group.

  • 67.
    Bondarevs, Andrejs
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Huss, Patrik
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Ye, Qin-Zhong
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Gong, Shaofang
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Universal Internet of Things Solution: Protocol Independent2017Ingår i: 2017 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT), IEEE , 2017, s. 1313-1318Konferensbidrag (Refereegranskat)
    Abstract [en]

    The diversity of wireless networks and protocols used by Internet of Things makes solutions non-interoperable. Moreover, some Things are not always able to communicate due to resource constrains or environmental factors. In this paper, those issues are addressed by introducing the concept of virtual Things. It means that each real Thing is virtualized in a local server or in the cloud, enabling communication with the user through a common protocol, i.e., the Internet Protocol. The virtual Thing has its own Internet Protocol address and authentication measure to control the access.

  • 68.
    Boonphoka, Terut
    et al.
    Huazhong Univ Sci and Technol, Peoples R China.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhong, Yi
    Huazhong Univ Sci and Technol, Peoples R China.
    Ge, Xiaohu
    Huazhong Univ Sci and Technol, Peoples R China.
    Uthansakul, Peerapong
    Suranaree Univ Technol, Thailand.
    Quek, Tony Q. S.
    Singapore Univ Technol and Design, Singapore.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Performance Analysis of Full-Duplex Relay Channel with Random Access2017Ingår i: 2017 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Relay is useful in wireless networks to assist the sources to deliver packets to the destinations. In this paper, the effect of full-duplex relay with random access is evaluated. Based on the model of two sources, two destinations, and one full-duplex relay with two queues, we obtain the analytical expressions for significant parameters, such as the arrival rate and the service rate for queues at the relay. Then, we evaluate the per-user throughput and the per-user average delay as functions of the signal-to-interference-plus-noise ratio (SINR) threshold and the self-interference cancelation coefficient through both analysis and simulation. We also consider the case where the two queues at the relay have different priorities and evaluate the effect of different transmit probabilities on the system performance. Our results reveal that the transmit probabilities and the transmit powers have an enormous impact on the self-interference, the average size and the empty probability of the queues. Specially, the queues tend to be stable when increasing the transmit probabilities and the transmit powers.

  • 69.
    Breyer, Nils
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Analysis of Travel Patterns from Cellular Network Data2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Traffic planners are facing a big challenge with an increasing demand for mobility and a need to drastically reduce the environmental impacts of the transportation system at the same time. The transportation system therefore needs to become more efficient, which requires a good understanding about the actual travel patterns. Data from travel surveys and traffic counts is expensive to collect and gives only limited insights on travel patterns. Cellular network data collected in the mobile operators infrastructure is a promising data source which can provide new ways of obtaining information relevant for traffic analysis. It can provide large-scale observations of travel patterns independent of the travel mode used and can be updated easier than other data sources. In order to use cellular network data for traffic analysis it needs to be filtered and processed in a way that preserves privacy of individuals and takes the low resolution of the data in space and time into account. The research of finding appropriate algorithms is ongoing and while substantial progress has been achieved, there is a still a large potential for better algorithms and ways to evaluate them.

    The aim of this thesis is to analyse the potential and limitations of using cellular network data for traffic analysis. In the three papers included in the thesis, contributions are made to the trip extraction, travel demand and route inference steps part of a data-driven traffic analysis processing chain. To analyse the performance of the proposed algorithms, a number of datasets from different cellular network operators are used. The results obtained using different algorithms are compared to each other as well as to other available data sources.

    A main finding presented in this thesis is that large-scale cellular network data can be used in particular to infer travel demand. In a study of data for the municipality of Norrköping, the results from cellular network data resemble the travel demand model currently used by the municipality, while adding more details such as time profiles which are currently not available to traffic planners. However, it is found that all later traffic analysis results from cellular network data can differ to a large extend based on the choice of algorithm used for the first steps of data filtering and trip extraction. Particular difficulties occur with the detection of short trips (less than 2km) with a possible under-representation of these trips affecting the subsequent traffic analysis.

    Delarbeten
    1. Trip extraction for traffic analysis using cellular network data
    Öppna denna publikation i ny flik eller fönster >>Trip extraction for traffic analysis using cellular network data
    2017 (Engelska)Ingår i: 5th IEEE International Conference on Models and Technologies for Intelligent Transportation Systems (MT-ITS) / [ed] IEEE Italy Section, Naples: IEEE Press, 2017, s. 321-326Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    To get a better understanding of people’s mobility, cellular network signalling data including location information, is a promising large-scale data source. In order to estimate travel demand and infrastructure usage from the data, it is necessary to identify the trips users make. We present two trip extraction methods and compare their performance using a small dataset collected in Sweden. The trips extracted are compared with GPS tracks collected on the same mobiles. Despite the much lower location sampling rate in the cellular network signalling data, we are able to detect most of the trips found from GPS data. This is promising, given the relative simplicity of the algorithms. However, further investigation is necessary using a larger dataset and more types of algorithms. By applying the same methods to a second dataset for Senegal with much lower sampling rate than the Sweden dataset, we show that the choice of the trip extraction method tends to be even more important when the sampling rate is low. 

    Ort, förlag, år, upplaga, sidor
    Naples: IEEE Press, 2017
    Nyckelord
    Global Positioning System, cellular radio, data communication, telecommunication traffic, Sweden, cellular network data, signalling data, traffic analysis, trip extraction, Antennas, Cellular networks, Data mining, Global Positioning System, Google, History, Spatial resolution
    Nationell ämneskategori
    Transportteknik och logistik
    Identifikatorer
    urn:nbn:se:liu:diva-140906 (URN)10.1109/MTITS.2017.8005688 (DOI)000426813700055 ()978-1-5090-6484-7 (ISBN)
    Konferens
    Models and Technologies for Intelligent Transportation Systems (MT-ITS), 26-28 June 2017, Naples, Italy
    Projekt
    MOFT
    Forskningsfinansiär
    Vinnova
    Tillgänglig från: 2017-09-15 Skapad: 2017-09-15 Senast uppdaterad: 2019-07-15Bibliografiskt granskad
    2. Cellpath Routing and Route Traffic Flow Estimation Based on Cellular Network Data
    Öppna denna publikation i ny flik eller fönster >>Cellpath Routing and Route Traffic Flow Estimation Based on Cellular Network Data
    2018 (Engelska)Ingår i: The Journal of urban technology, ISSN 1063-0732, E-ISSN 1466-1853, nr 2, s. 85-104Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The signaling data in cellular networks provide means for analyzing the use of transportation systems. We propose methods that aim to reconstruct the used route through a transportation network from call detail records (CDRs) which are spatially and temporally sparse. The route estimation methods are compared based on the individual routes estimated. We also investigate the effect of different route estimation methods when employed in a complete network assignment for a larger city. Using an available CDR dataset for Dakar, Senegal, we show that the choice of the route estimation method can have a significant impact on resulting link flows.

    Ort, förlag, år, upplaga, sidor
    Taylor & Francis, 2018
    Nyckelord
    Cellular network data, route estimation, network assignment
    Nationell ämneskategori
    Transportteknik och logistik
    Identifikatorer
    urn:nbn:se:liu:diva-144541 (URN)10.1080/10630732.2017.1386939 (DOI)000437198100006 ()
    Anmärkning

    Funding agencies: Swedish Governmental Agency for Innovation Systems (VINNOVA)

    Tillgänglig från: 2018-01-26 Skapad: 2018-01-26 Senast uppdaterad: 2019-05-29
  • 70.
    Capone, Antonio
    et al.
    Tech Univ Milan, Italy.
    Li, Yuan
    Natl Innovat Inst Def Technol, Peoples R China.
    Pioro, Michal
    Warsaw Univ Technol, Poland.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Minimizing end-to-end delay in multi-hop wireless networks with optimized transmission scheduling2019Ingår i: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 89, s. 236-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of transmission scheduling in single hop and multi-hop wireless networks has been extensively studied. The focus has been on optimizing the efficiency of transmission parallelization, through a minimum-length schedule that meets a given set of traffic demands using the smallest possible number of time slots. Each time slot is associated with a set of transmissions that are compatible with each other according to the considered interference model. The minimum-length approach maximizes the resource reuse, but it does not ensure minimum end-to-end packet delay for multiple source-destination pairs, due to its inherent assumption of frame periodicity. In the paper we study the problem of transmission scheduling and routing aiming at minimizing the end-to-end delay under the signal-to-interference-and-noise-ratio (SINR) model for multi-hop networks. Two schemes are investigated. The first scheme departs from the conventional scheduling approach, by addressing explicitly end-to-end delay and removing the restriction of frame periodicity. The second scheme extends the first one by featuring cooperative forwarding and forward interference cancellation. We study the properties of the two schemes, and propose novel mixed-integer programming models and solution algorithms. Extensive results are provided to gain insights on how the schemes perform in end-to-end delay. (C) 2019 Elsevier B.V. All rights reserved.

    Publikationen är tillgänglig i fulltext från 2021-02-08 13:25
  • 71.
    Carlsson, Erik
    Linköpings universitet, Institutionen för systemteknik, Datorteknik.
    Synchronization of Distributed Units without Access to GPS2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Tidssynkronisering mellan två system som saknar externa referenser kan bli ett problem i små nodbaserade system. I det här arbetet har en sändtagare designats och implementerats i två system. Sedan valdes algoritmen "TwoWay Time Transfer"för att rätta till de timing fel som uppstår mellan systemens separata klockor.I sammanfattningen så jämnförs uppkommna resultat med att ha systemens tid från GPS.

  • 72.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Optimized eeeBond: Energy Efficiency with non-Proportional Router Network Interfaces2016Ingår i: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), ACM Digital Library, 2016, s. 215-223Konferensbidrag (Refereegranskat)
    Abstract [en]

    The recent Energy Efficient Ethernet (EEE) standard and the eBond protocol provide two orthogonal approaches that allow significant energy savings on routers. In this paper we present the modeling and performance evaluation of these two protocols and a hybrid protocol. We first present eeeBond, pronounced ``triple-e bond'', which combines the eBond capability to switch between multiple redundant interfaces with EEE's active/idle toggling capability implemented in each interface. Second, we present an analytic model of the protocol performance, and derive closed-form expressions for the optimized parameter settings of both eBond and eeeBond. Third, we present a performance evaluation that characterizes the relative performance gains possible with the optimized protocols, as well as a trace-based evaluation that validates the insights from the analytic model. Our results show that there are significant advantages to combine eBond and EEE. The eBond capability provides good savings when interfaces only offer small energy savings when in short-term sleep states, and the EEE capability is important as short-term sleep savings improve.

  • 73.
    Carlsson, Niklas
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Eager, Derek
    Univ Saskatchewan, Canada.
    Worst-case bounds and optimized cache on Mth request cache insertion policies under elastic conditions2018Ingår i: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 127, s. 70-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cloud services and other shared third-party infrastructures allow individual content providers to easily scale their services based on current resource demands. In this paper, we consider an individual content provider that wants to minimize its delivery costs under the assumptions that the storage and bandwidth resources it requires are elastic, the content provider only pays for the resources that it consumes, and costs are proportional to the resource usage. Within this context, we (i) derive worst-case bounds for the optimal cost and competitive cost ratios of different classes of cache on Mth request cache insertion policies, (ii) derive explicit average cost expressions and bounds under arbitrary inter request distributions, (iii) derive explicit average cost expressions and bounds for short tailed (deterministic, Erlang, and exponential) and heavy-tailed (Pareto) inter-request distributions, and (iv) present numeric and trace-based evaluations that reveal insights into the relative cost performance of the policies. Our results show that a window-based cache on 2nd request policy using a single threshold optimized to minimize worst-case costs provides good average performance across the different distributions and the full parameter ranges of each considered distribution, making it an attractive choice for a wide range of practical conditions where request rates of individual file objects typically are not known and can change quickly. (C) 2018 Elsevier B.V. All rights reserved.

  • 74.
    Carlsson, Robin
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Investigation and Implementation of Coexistence Tool for Antennas2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With the increase of the number of radios and antennas on today’s systems, the risk of co-site interference is very high. Intermodulation product and antenna coupling are two common sources of interference. The thesis investigates some features of a radio system, like antenna types, receiver parameters, intermodulation products and isolation, and suggests how this knowledge can be used to minimize the risk of co-site interference. The goal is to maximize the isolation between the antennas, by good frequency planning, the use of filters and taking great care in antenna placement. A first version of an analysis software was developed where transmitters and receivers can be paired and evaluated. An intermodulation product calculator was also implemented, to easily find which products are an issue and where they originate. The goal of the software is to be simple to use and easy to adapt to different setups and situations. It should also be easy to upgrade with new features.

  • 75.
    Cen, Song
    et al.
    Xi An Jiao Tong Univ, Peoples R China.
    Zhang, Xingjun
    Xi An Jiao Tong Univ, Peoples R China.
    Lei, Ming
    Xi An Jiao Tong Univ, Peoples R China.
    Fowler, Scott
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Dong, Xiaoshe
    Xi An Jiao Tong Univ, Peoples R China.
    Stochastic geometry modeling and energy efficiency analysis of millimeter wave cellular networks2018Ingår i: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 24, nr 7, s. 2565-2578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current wireless networks face unprecedented challenges because of the exponentially increasing demand for mobile data and the rapid growth in infrastructure and power consumption. This study investigates the optimal energy efficiency of millimeter wave (mmWave) cellular networks, given that these networks are some of the most promising 5G-enabling technologies. Based on the stochastic geometry, a mathematical framework of coverage probability is proposed and the optimal energy efficiency is obtained with coverage performance constraints. Numerical results show that increasing the base station density damages coverage performance exceeding the threshold. This work demonstrates an essential understanding of the deployment and dynamic control of energy-efficient mmWave cellular networks.

  • 76.
    Chandhar, Prabhu
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Danev, Danyo
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Massive MIMO as Enabler for Communications with Drone Swarms2016Ingår i: 2016 INTERNATIONAL CONFERENCE ON UNMANNED AIRCRAFT SYSTEMS (ICUAS), IEEE , 2016, s. 347-354Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive multiple-input multiple-output (MIMO) is an emerging technology for mobile communications, where a large number of antennas are employed at the base station to simultaneously serve multiple single-antenna terminals with very high capacity. In this paper, we study the potentials and challenges of utilizing massive MIMO for unmanned aerial vehicles (UAVs) communication. We consider a scenario where multiple single-antenna UAVs simultaneously communicate with a ground station (GS) equipped with a large number of antennas. Speci[1]cally, we discuss the achievable uplink (UAV to GS) capacity performance in the case of line-of-sight (LoS) conditions. We also study the type of antenna polarization that should be used in order to maintain a reliable communication link between the GS and the UAVs. The results obtained using a realistic geometric model show that massive MIMO is a potential enabler for high-capacity UAV network

  • 77.
    Chandhar, Prabhu
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Danev, Danyo
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    On Ergodic Rates and Optimal Array Geometry in Line-of-Sight Massive MIMO2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the achievable ergodic rate of Massive multi-input-multi-output (MIMO) system in environments with high mobility and line-of-sight (LoS). A 3-dimensional geometric model with uniform rectangular array at the basestation (BS) is used for the investigation. We derive a closed formexpression for a lower bound on the uplink ergodic rate takinginto account imperfections of the channel state information,number of BS antennas, antenna spacing, and spatial distributionof user terminals. The results show that, in LoS Massive MIMO, when the terminals are spherically uniformly distributed around the BS, the ergodic rate is maximized for antenna spacing equal to integer multiples of one-half wavelength.

  • 78.
    Chandhar, Prabhu
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Danev, Danyo
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    On the Zero-Forcing Receiver Performance for Massive MIMO Drone Communications2018Ingår i: 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Institute of Electrical and Electronics Engineers (IEEE), 2018, s. 930-934Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the uplink ergodic rate performance of the zero-forcing (ZF) receiver in a Massive multiple-input and multiple-output (MIMO) enabled drone communication system. Considering a 3D geometric model for line-of-sight (LoS) propagation, approximate but accurate analyses of lower and upper bounds on the uplink ergodic rate with estimated channel state information (CSI) are provided.

  • 79.
    Chen, Bolin
    et al.
    Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.
    Chen, Zheng
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.
    Modeling and Analysis of MPTCP Proxy-based LTE-WLAN Path Aggregation2017Ingår i: 2017 IEEE Global Communications Conference (GLOBECOM), Proceedings Singapore 4 – 8 December 2017, IEEE Communications Society, 2017, s. 1-7Konferensbidrag (Refereegranskat)
    Abstract [en]

    Long Term Evolution (LTE)-Wireless Local Area Network (WLAN) Path Aggregation (LWPA) based on Multi- path Transmission Control Protocol (MPTCP) has been under standardization procedure as a promising and cost-efficient solution to boost Downlink (DL) data rate and handle the rapidly increasing data traffic. This paper aims at providing tractable analysis for the DL performance evaluation of large-scale LWPA networks with the help of tools from stochastic geometry. We consider a simple yet practical model to determine under which conditions a native WLAN Access Point (AP) will work under LWPA mode to help increasing the received data rate. Using stochastic spatial models for the distribution of WLAN APs and LTE Base Stations (BSs), we analyze the density of active LWPA- mode WiFi APs in the considered network model, which further leads to closed-form expressions on the DL data rate and area spectral efficiency (ASE) improvement. Our numerical results illustrate the impact of different network parameters on the performance of LWPA networks, which can be useful for further performance optimization. 

  • 80.
    Chen, Bolin
    et al.
    Univ Sheffield, England.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Chen, Zheng
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Univ Sheffield, England.
    LTE-WLAN Aggregation with Bursty Data Traffic and Randomized Flow Splitting2019Ingår i: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    We investigate the effect of bursty traffic in an LTE and Wi-Fi aggregation (LWA)-enabled network, where part of the LTE traffic is offloaded to Wi-Fi access points (APs) to boost the performance of LTE networks. A Wi-Fi AP maintains two queues containing data intended for the LWA-mode user and the native Wi-Fi user, and it is allowed to serve them simultaneously by using superposition coding (SC). With respect to the existing works on LWA, the novelty of our study consists of a random access protocol allowing the Wi-Fi AP to serve the native Wi-Fi user with probabilities that depend on the queue size of the LWA-mode data. We analyze the throughput of the native Wi-Fi network, accounting for different transmitting probabilities of the queues, the traffic flow splitting between LTE and Wi-Fi, and the operating mode of the LWA user with both LTE and Wi-Fi interfaces. Our results provide fundamental insights in the throughput behavior of such aggregated systems, which are essential for further investigation in larger topologies.

  • 81.
    Chen, Kairang
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Energy-Efficient Data Converters for Low-Power Sensors2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Wireless sensor networks (WSNs) are employed in many applications, such as for monitoring bio-potential signals and environmental information. These applications require high-resolution (> 12-bit) analog-to-digital converters (ADCs) at low-sampling rates (several kS/s). Such sensor nodes are usually powered by batteries or energy-harvesting sources hence low power consumption is primary for such ADCs. Normally, tens or hundreds of autonomously powered sensor nodes are utilized to capture and transmit data to the central processor. Hence it is profitable to fabricate the relevant electronics, such as the ADCs, in a low-cost standard complementary metal-oxide-semiconductor (CMOS) process. The two-stage pipelined successive approximation register (SAR) ADC has shown to be an energy-efficient architecture for high resolution. This thesis further studies and explores the design limitations of the pipelined SAR ADC for high-resolution and low-speed applications.

    The first work is a 15-bit, 1 kS/s two-stage pipelined SAR ADC that has been implemented in 0.35-μm CMOS process. The use of aggressive gain reduction in the residue amplifier combined with a suitable capacitive array digital-to-analog converter (DAC) topology in the second-stage simplifies the design of the operational transconductance amplifier (OTA) while eliminating excessive capacitive load and consequent power consumption. A comprehensive power consumption analysis of the entire ADC is performed to determine the number of bits in each stage of the pipeline. Choice of a segmented capacitive array DAC and attenuation capacitorbased DAC for the first and second stages respectively enable significant reduction in power consumption and area. Fabricated in a low-cost 0.35-μm CMOS process, the prototype ADC achieves a peak signal-to-noise-and-distortion ratio (SNDR) of 78.9 dB corresponding to an effective number of bits (ENOB) of 12.8-bit at a sampling frequency of 1 kS/s and provides a Schreier figure-of-merit (FoM) of 157.6 dB. Without any form of calibration, the ADC maintains an ENOB > 12.1-bit up to the Nyquist bandwidth of 500 Hz while consuming 6.7 μW. Core area of the ADC is 0.679 mm2.

    The second work is a 14-bit, tunable bandwidth two-stage pipelined SAR ADC which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high open-loop DC gain requirement of the OTA in the gain-stage, a 3-stage capacitive charge pump (CCP) is utilized to achieve the gain-stage instead of using the switch capacitor (SC) amplifier. Unity-gain OTAs have been used as the analog buffers to prevent the charge sharing between the CCP stages. The detailed design considerations are given in this work. The prototype ADC, designed and fabricated in a low-cost 0.35-μm CMOS process, achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 μW and 96 μW, respectively. The corresponding Schreier FoM are 166.7 dB and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR > 75 dB up

    to 260 kHz. The core area occupied by the ADC is 0.589 mm2.

    As the low-power sensors might be active only for very short time triggered by an external pulse to acquire the data, the third work is a 14-bit asynchronous two-stage pipelined SAR ADC which has been designed and simulated in 0.18-μm CMOS process. A self-synchronous loop based on an edge detector is utilized to generate an internal clock with variable phase. A tunable delay element enables to allocate the available time for the switch capacitor DACs and the gain-stage. Three separate asynchronous clock generators are implemented to create the control signals for two sub-ADCs and the gain-stage between. Aiming to reduce the power consumption of the gain-stage, simple source followers as the analog buffers are implemented in the 3-stage CCP gain-stage. Post-layout simulation results show that the ADC achieves a SNDR of 83.5 dB while consuming 2.39 μW with a sampling rate of 10 kS/s. The corresponding Schreier FoM is 176.7 dB.

    Delarbeten
    1. Design of a 12.8 ENOB, 1 kS/s pipelined SAR ADC in 0.35-μm CMOS
    Öppna denna publikation i ny flik eller fönster >>Design of a 12.8 ENOB, 1 kS/s pipelined SAR ADC in 0.35-μm CMOS
    2016 (Engelska)Ingår i: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 86, nr 1, s. 87-98Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents a 15-bit, two-stage pipelined successive approximation register analog-to-digital converter (ADC) suitable for low-power, cost-effective sensor readout circuits. The use of aggressive gain reduction in the residue amplifier combined with a suitable capacitive array DAC topology in the second stage simplifies the design of the operational transconductance amplifier while eliminating excessive capacitive load and consequent power consumption. An elaborate power consumption analysis of the entire ADC was performed to determine the number of bits in each stage of the pipeline. Choice of a segmented capacitive array DAC and attenuation capacitor-based DAC for the first and second stages respectively enable significant reduction in power consumption and area. Fabricated in a low-cost 0.35-μm CMOS process, the prototype ADC achieves a peak SNDR of 78.9 dB corresponding to an effective number of bits (ENOB) of 12.8 bits at a sampling frequency of 1 kS/s and provides an FoM of 157.6 dB. Without any form of calibration, the ADC maintains an ENOB >12.1 bits upto the Nyquist bandwidth of 500 Hz while consuming 6.7 μW. Core area of the ADC is 0.679 mm2.

    Ort, förlag, år, upplaga, sidor
    Springer, 2016
    Nyckelord
    Pipelined SAR ADC; High resolution; OTA; Capacitive DAC
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-124472 (URN)10.1007/s10470-015-0648-2 (DOI)000367750900011 ()
    Tillgänglig från: 2016-02-02 Skapad: 2016-02-01 Senast uppdaterad: 2019-09-05Bibliografiskt granskad
    2. A pipelined SAR ADC with gain-stage based on capacitive charge pump
    Öppna denna publikation i ny flik eller fönster >>A pipelined SAR ADC with gain-stage based on capacitive charge pump
    2017 (Engelska)Ingår i: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 90, nr 1, s. 43-53Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents a 14-bit, tunable bandwidth two-stage pipelined successive approximation analog to digital converter which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high DC gain requirement of operational transconductance amplifier in the gain-stage, the multi-stage capacitive charge pump (CCP) was utilized to achieve the gain-stage instead of using the switch capacitor integrator. The detailed design considerations are given in this work. Thereafter, the 14-bit ADC was designed and fabricated in a low-cost 0.35-µm CMOS process. The prototype ADC achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 and 96 µW, respectively. The corresponding FoM are 166.7 and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR >75 dB upto 260 kHz. The core area occupied by the ADC is 0.589 mm2.

    Ort, förlag, år, upplaga, sidor
    New York: Springer, 2017
    Nyckelord
    Capacitive charge pump, OTA, Switch capacitor integrator, Two-stage pipelined SAR ADC
    Nationell ämneskategori
    Elektroteknik och elektronik Signalbehandling Datorteknik Programvaruteknik
    Identifikatorer
    urn:nbn:se:liu:diva-133228 (URN)10.1007/s10470-016-0872-4 (DOI)000391922200005 ()
    Tillgänglig från: 2016-12-15 Skapad: 2016-12-15 Senast uppdaterad: 2019-09-05Bibliografiskt granskad
    3. Power Analysis for Two-Stage High Resolution Pipeline SAR ADC
    Öppna denna publikation i ny flik eller fönster >>Power Analysis for Two-Stage High Resolution Pipeline SAR ADC
    2015 (Engelska)Ingår i: Proceedings of the22 International Conference “Mixed Design of Integrated Circuits and Systems”, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 496-499Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this paper, we provide a detailed analysis on the power consumption of two-stage pipeline successive approximation analog-to-digital converter (SAR ADC) and also show the relationship between stage resolution and the total power consumption in 65 nm technology. Thereafter, we evaluate the analysis results with designing a 15-bit pipeline SAR ADC in 65 nm technology and also a power comparison between two-stage pipeline SAR ADC and single SAR ADC is analyzed with the parameters from same technology. The finally results demonstrate that for high resolution ADC design, a particular range is obtained, in which the total power consumption of two-stage pipeline SAR ADC is much lower than single SAR ADC.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2015
    Nyckelord
    High resolution; pipeline; power consumption; successive approximation analog-to-digital; converter; two-stage
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-122623 (URN)10.1109/MIXDES.2015.7208570 (DOI)000364071600094 ()978-8-3635-7806-0 (ISBN)
    Konferens
    The22 International Conference “Mixed Design of Integrated Circuits and Systems”(MIXDES), Toruń, Poland, 25-27 June 2015
    Tillgänglig från: 2015-11-16 Skapad: 2015-11-12 Senast uppdaterad: 2019-09-05Bibliografiskt granskad
    4. Design of a Gain-stage for Pipelined SAR ADC Using Capacitive Charge Pump
    Öppna denna publikation i ny flik eller fönster >>Design of a Gain-stage for Pipelined SAR ADC Using Capacitive Charge Pump
    2016 (Engelska)Ingår i: PROCEEDINGS OF THE 23RD INTERNATIONAL CONFERENCE ON MIXED DESIGN OF INTEGRATED CIRCUITS AND SYSTEMS (MIXDES 2016), IEEE , 2016, s. 187-190Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper presents the design of a multi-stage capacitive charge pump (CCP) as a gain-stage which is used in the two-stage pipelined successive approximation analog-to-digital converter (SAR ADC). The topology of multi-stage CCP and the design considerations are provided. Thereafter, the power comparison between switch capacitor (SC) integrator and multi-stage CCP is analyzed with the parameters from 0.35-mu m CMOS process. The comparison results show that the proposed gain-stage is more power efficient than SC integrator. To verify the analysis, two types of gain-stage, SC integrator and multi-stage CCP, were simulated in 0.35-mu m CMOS process. Simulation results show that the three-stage CCP achieves a gain of 7.9 while only consuming 1.1 mu W with the gain bandwidth of 178.7 kHz. But the SC integrator consumes 1.58 times more power than CCPs to reach the similar gain and gain bandwidth.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2016
    Nyckelord
    Capacitive charge pump; successive approximation analog-to-digital converter; power consumption; pipeline; two-stage
    Nationell ämneskategori
    Annan elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-132104 (URN)10.1109/MIXDES.2016.7529729 (DOI)000383221700035 ()978-8-3635-7808-4 (ISBN)
    Konferens
    23rd International Conference on Mixed Design of Integrated Circuits and Systems (MIXDES)
    Tillgänglig från: 2016-10-18 Skapad: 2016-10-17 Senast uppdaterad: 2019-09-05
  • 82.
    Chen, Lei
    et al.
    Viktoria Swedish ICT, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Design of in-building distributed antenna systems: mathematical models and efficient algorithms2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, IEEE , 2015, s. 1497-1502Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to provide sufficient coverage and capacity for indoor users, in-building distributed antenna system (IB-DAS) has been considered. A passive IB-DAS deploys distributed antennas inside the building and connects the antennas to a base station (BS) through coaxial cables and power equipment. Power is distributed from the BS to each of the antennas. We consider an optimal design of passive IB-DAS with the target to minimize the cable usage, together with the consideration of power distribution. We decompose the problem into two sub-problems, namely the topological design and the equipment selection. Mixed integer linear models are developed for solving the sub-problems. Local search is designed to combine the sub-problems and balance their objectives. Application over realistic IB-DAS deployment and comparison with previous studies demonstrate the effectiveness of the algorithm.

  • 83.
    Chen, Zheng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Can We Rely on Channel Hardening in Cell-Free Massive MIMO?2017Ingår i: 2017 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Channel hardening makes fading multi-antenna channels behave as deterministic when there are many antennas. Massive MIMO systems utilize this phenomenon to deliver high and reliable performance from cellular access points. Recently, an alternative form of Massive MIMO has appeared: Cell-Free (CF) Massive MIMO. It is based on having many access points (APs) distributed over a large geographical area and these jointly serve all the users. Since the AP antennas are distributed, instead of co-located, it is not clear if these systems will inherit the channel hardening. In this paper, we use stochastic geometry to investigate this problem. Our results show that the amount of channel hardening is strongly affected by the number of antennas per AP and the propagation environment. To achieve channel hardening in CF Massive MIMO, it is beneficial to have multiple antennas per AP and a small path-loss exponent.

  • 84.
    Chen, Zheng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    Huawei Technol Co Ltd, France.
    Decentralized Opportunistic Access for D2D Underlaid Cellular Networks2018Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 66, nr 10, s. 4842-4853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we propose a decentralized access control scheme for interference management in device-to-device (D2D) underlaid cellular networks. Our method combines signal-to-interference ratio (SIR)-aware link activation with cellular guard zones in a system, where D2D links opportunistically access the licensed cellular spectrum when the activation conditions are satisfied. Analytical expressions for the success/coverage probability of both cellular and D2D links are derived. We characterize the impact of the guard zone radius and the SIR threshold on the D2D potential throughput and cellular coverage. A tractable approach is proposed to find the SIR threshold and guard zone radius that maximize the potential throughput of the D2D communication while ensuring sufficient coverage probability for the cellular uplink users. Simulations validate the accuracy of our analytical results and show the performance gain of the proposed scheme compared to prior state-of-the-art solutions.

  • 85.
    Chen, Zheng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten. University of Paris Sud, France.
    Lee, Jemin
    Daegu Gyeongbuk Institute Science and Technology, South Korea.
    Quek, Tony Q. S.
    Singapore University of Technology and Design, Singapore.
    Kountouris, Marios
    Huawei Technology France SASU, France.
    Cooperative Caching and Transmission Design in Cluster-Centric Small Cell Networks2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 5, s. 3401-3415Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless content caching in small cell networks (SCNs) has recently been considered as an efficient way to reduce the data traffic and the energy consumption of the backhaul in emerging heterogeneous cellular networks. In this paper, we consider a cluster-centric SCN with combined design of cooperative caching and transmission policy. Small base stations (SBSs) are grouped into disjoint clusters, in which in-cluster cache space is utilized as an entity. We propose a combined caching scheme, where part of the cache space in each cluster is reserved for caching the most popular content in every SBS, while the remaining is used for cooperatively caching different partitions of the less popular content in different SBSs, as a means to increase local content diversity. Depending on the availability and placement of the requested content, coordinated multi-point technique with either joint transmission or parallel transmission is used to deliver content to the served user. Using Poisson point process for the SBS location distribution and a hexagonal grid model for the clusters, we provide analytical results on the successful content delivery probability of both transmission schemes for a user located at the cluster center. Our analysis shows an inherent tradeoff between transmission diversity and content diversity in our cooperation design. We also study the optimal cache space assignment for two objective functions: maximization of the cache service performance and the energy efficiency. Simulation results show that the proposed scheme achieves performance gain by leveraging cache-level and signal-level cooperation and adapting to the network environment and user quality-of-service requirements.

  • 86.
    Chen, Zheng
    et al.
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    Mathematical and Algorithmic Sciences Lab, France Research Center, Huawei Technologies France SASU, Boulogne-Billancourt, France.
    Energy Harvesting in Delay-Aware Cognitive Shared Access Networks2017Ingår i: IEEE Workshop on Emerging Energy Harvesting Solutions for 5G Networks (5G-NRG): May 2017, Paris, France., IEEE Press, 2017, s. 168-173Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we study the effect of energy harvesting in a cognitive shared access network with delay constraints on the primary user. We model the distribution of secondary nodes by a homogeneous Poisson point process (PPP), while the primary user is located at fixed location. The secondary users are assumed to have always packets to transmit whilst the primary transmitter has bursty traffic. We assume an energy harvesting zone around the primary transmitter and a guard zone around the primary receiver. The secondary users are transmitting in a random access manner, however, transmissions of secondary nodes are restricted by their battery status and location. Targeting at achieving the maximum secondary throughput under primary delay constraints, we analyze the impact of various parameters on the performance of the considered network. Our results provide insights into the optimization of access protocol parameters for the energy harvesting-based cognitive shared access network with delay constraints.

  • 87.
    Chen, Zheng
    et al.
    University of Paris Sud, France.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Kountouris, Marios
    Huawei Technology Co Ltd, Peoples R China.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Throughput Analysis of Smart Objects with Delay Constraints2016Ingår i: 2016 IEEE 17TH INTERNATIONAL SYMPOSIUM ON A WORLD OF WIRELESS, MOBILE AND MULTIMEDIA NETWORKS (WOWMOM), IEEE , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we analyze a shared access network with one primary device and randomly distributed smart objects with secondary priority. Assuming random traffic at the primary device and saturated queues at the smart objects with secondary priority, an access protocol is employed to adjust the random access probabilities of the smart objects depending on the congestion level of the primary. We characterize the maximum throughput of the secondary network with respect to delay constraints on the primary. Our results highlight the impact of system design parameters on the delay and throughput behavior of the shared access network with massive number of connected objects.

  • 88.
    Cheng, Hei Victor
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Aspects of Power Allocation in Massive MIMO2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The past decades have seen a rapid growth of mobile data trac, both in terms of connected devices and data rate. To satisfy the ever growing data trac demand in wireless communication systems, the current cellular systems have to be redesigned to increase both spectral eciency and energy eciency. Massive MIMO (Multiple-Input-Multiple-Output) is one solution that satisfy both requirements. In massive MIMO systems, hundreds of antennas are employed at the base station to provide service to many users at the same time and frequency. This enables the system to serve the users with uniformly good quality of service simultaneously, with low-cost hardware and without using extra bandwidth and energy. To achieve this, proper resource allocation is needed. Among the available resources, transmit power is one of the most important degree of freedom to control the spectral eciency and energy eciency. Due to the use of excessive number of antennas and low-end hardware at the base station, new aspects of power allocation compared to current systems arises. In the rst part of the thesis, a new uplink power allocation schemes that based on long term channel statistics is proposed. Since quality of the channel estimates is crucial in massive MIMO, in addition to data power allocation, joint power allocation that includes the pilot power as additional variable should be considered. Therefore a new framework for power allocation that matches practical systems is developed, as the methods developed in the literature cannot be applied directly to massive MIMO systems. Simulation results conrm the advantages brought by the the proposed new framework. In the second part of the thesis, we investigate the eects of using low-end ampliers at the base stations. The non-linear behavior of power consumption in these ampliers changes the power consumption model at the base station, thereby changes the power allocation. Two dierent scenarios are investigated and both results show that a certain number of antennas can be turned o in low load scenarios.

    Delarbeten
    1. MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints
    Öppna denna publikation i ny flik eller fönster >>MIMO Capacity under Power Amplifiers Consumed Power and Per-Antenna Radiated Power Constraints
    2014 (Engelska)Ingår i: 2014 IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Institute of Electrical and Electronics Engineers (IEEE), 2014, s. 179-183Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    We investigate the capacity of the multiple-input-multiple-output channel taking into account the consumed power in the power amplifiers. The mutual information is optimized with a limitation of total consumed power and per-antenna radiated power for a fixed channel with full channel state information at both the transmitter and receiver. The capacity is thus obtained by optimizing the input distribution to maximize the mutual information. Since the optimization problem is non-convex, direct computation of the capacity suffers from high computational complexity. Hence upper and lower bounds on the capacity are given as benchmarks for different ad-hoc schemes. An efficient suboptimal algorithm is also presented. Numerical results show that the suboptimal algorithm performs close to the capacity.

    Ort, förlag, år, upplaga, sidor
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Serie
    IEEE International Workshop on Signal Processing Advances in Wireless Communications, ISSN 2325-3789
    Nyckelord
    MIMO capacity; power amplifier; consumed power constraint; per-antenna power constraint
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-114602 (URN)10.1109/SPAWC.2014.6941397 (DOI)000348859000037 ()9781479949038 (ISBN)9781479939121 (ISBN)9781479949021 (ISBN)
    Konferens
    IEEE 15th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC),June 22-25, Toronto, Canada
    Tillgänglig från: 2015-02-26 Skapad: 2015-02-26 Senast uppdaterad: 2016-11-24Bibliografiskt granskad
    2. Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
    Öppna denna publikation i ny flik eller fönster >>Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
    2015 (Engelska)Ingår i: 2015 IEEE International Conference on Communications (ICC), IEEE , 2015, s. 1697-1702Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    For both maximum ratio transmission (MRT) and zero forcing (ZF) precoding schemes and given any specific rate requirement the optimal transmit power, number of antennas to be used, number of users to be served and number of pilots spent on channel training are found with the objective to minimize the total consumed power at the base station. The optimization problem is solved by finding closed form expressions of the optimal transmit power and then search over the remaining discrete variables. The analysis consists of two parts, the first part investigates the situation when only power consumed in the RF amplifiers is considered. The second part includes both the power consumed in the RF amplifiers and in other transceiver circuits. In the former case having all antennas active while reducing the transmit power is optimal. Adaptive scheme to switch off some of the antennas at the base stations is found to be optimal in the latter case.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2015
    Serie
    IEEE International Conference on Communications, ISSN 1550-3607, E-ISSN 1938-1883
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-127290 (URN)10.1109/ICC.2015.7248569 (DOI)000371708101150 ()9781467364324 (ISBN)9781467364317 (ISBN)9781467364300 (ISBN)
    Konferens
    IEEE International Conference on Communications (ICC), 8-12 June, London, UK
    Tillgänglig från: 2016-04-20 Skapad: 2016-04-19 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
  • 89.
    Cheng, Hei Victor
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Optimizing Massive MIMO: Precoder Design and Power Allocation2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The past decades have seen a rapid growth of mobile data traffic,both in terms of connected devices and data rate. To satisfy the evergrowing data traffic demand in wireless communication systems, thecurrent cellular systems have to be redesigned to increase both spectralefficiency and energy efficiency. Massive MIMO(Multiple-Input-Multiple-Output) is one solution that satisfy bothrequirements. In massive MIMO systems, hundreds of antennas areemployed at the base station to provide service to many users at thesame time and frequency. This enables the system to serve the userswith uniformly good quality of service simultaneously, with low-costhardware and without using extra bandwidth and energy. To achievethis, proper resource allocation is needed. Among the availableresources, transmit power beamforming are the most important degrees offreedom to control the spectral efficiency and energy efficiency. Dueto the use of excessive number of antennas and low-end hardware at thebase station, new aspects of power allocation and beamforming compared to currentsystems arises.

    In the first part of the thesis, new uplink power allocation schemes that based on long term channel statistics isproposed. Since quality of the channel estimates is crucial in massive MIMO, in addition to data power allocation, joint power allocationthat includes the pilot power as additional variable should be considered. Therefore a new framework for power allocation thatmatches practical systems is developed, as the methods developed in the literature cannot be applied directly to massive MIMO systems. Simulation results confirm the advantages brought by the the proposed new framework.

    In the second part, we introduces a new approach to solve the joint precoding and power allocation for different objective in downlink scenarios by a combination of random matrix theory and optimization theory. The new approach results in a simplified problem that, though non-convex, obeys a simple separable structure. Simulation results showed that the proposed scheme provides large gains over heuristic solutions when the number of users in the cell is large, which is suitable for applying in massive MIMO systems.

    In the third part we investigate the effects of using low-end amplifiers at the basestations. The non-linear behavior of power consumption in these amplifiers changes the power consumption model at the basestation, thereby changes the power allocation and beamforming design. Different scenarios are investigated and resultsshow that a certain number of antennas can be turned off in some scenarios.

    In the last part we consider the use of non-orthogonal-multiple-access (NOMA) inside massive MIMO systems in practical scenarios where channel state information (CSI) is acquired through pilot signaling. Achievable rate analysis is carried out for different pilot signaling schemes including both uplink and downlink pilots. Numerical results show that when downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. However with more groups of users present in the cell, it is preferable to use multi-user beamforming in stead of NOMA.

    Delarbeten
    1. Optimal Pilot and Payload Power Control in Single-Cell Massive MIMO Systems
    Öppna denna publikation i ny flik eller fönster >>Optimal Pilot and Payload Power Control in Single-Cell Massive MIMO Systems
    2017 (Engelska)Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 65, nr 9, s. 2363-2378Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper considers the jointly optimal pilot and data power allocation in single-cell uplink massive multiple-input-multiple- output systems. Using the spectral efficiency (SE) as performance metric and setting a total energy budget per coherence interval, the power control is formulated as optimization problems for two different objective functions: the weighted minimum SE among the users and the weighted sum SE. A closed form solution for the optimal length of the pilot sequence is derived. The optimal power control policy for the former problem is found by solving a simple equation with a single variable. Utilizing the special structure arising from imperfect channel estimation, a convex reformulation is found to solve the latter problem to global optimality in polynomial time. The gain of the optimal joint power control is theoretically justified, and is proved to be large in the low-SNR regime. Simulation results also show the advantage of optimizing the power control over both pilot and data power, as compared to the cases of using full power and of only optimizing the data powers as done in previous work.

    Ort, förlag, år, upplaga, sidor
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Nyckelord
    Massive MIMO; power control; power allocation; convex optimization
    Nationell ämneskategori
    Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-136034 (URN)10.1109/TSP.2016.2641381 (DOI)000395877600013 ()
    Anmärkning

    Funding Agencies|EU [ICT-619086]; ELLIIT; CENIIT

    Tillgänglig från: 2017-03-27 Skapad: 2017-03-27 Senast uppdaterad: 2019-06-28
    2. Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
    Öppna denna publikation i ny flik eller fönster >>Massive MIMO at Night: On the Operation of Massive MIMO in Low Traffic Scenarios
    2015 (Engelska)Ingår i: 2015 IEEE International Conference on Communications (ICC), IEEE , 2015, s. 1697-1702Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    For both maximum ratio transmission (MRT) and zero forcing (ZF) precoding schemes and given any specific rate requirement the optimal transmit power, number of antennas to be used, number of users to be served and number of pilots spent on channel training are found with the objective to minimize the total consumed power at the base station. The optimization problem is solved by finding closed form expressions of the optimal transmit power and then search over the remaining discrete variables. The analysis consists of two parts, the first part investigates the situation when only power consumed in the RF amplifiers is considered. The second part includes both the power consumed in the RF amplifiers and in other transceiver circuits. In the former case having all antennas active while reducing the transmit power is optimal. Adaptive scheme to switch off some of the antennas at the base stations is found to be optimal in the latter case.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2015
    Serie
    IEEE International Conference on Communications, ISSN 1550-3607, E-ISSN 1938-1883
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:liu:diva-127290 (URN)10.1109/ICC.2015.7248569 (DOI)000371708101150 ()9781467364324 (ISBN)9781467364317 (ISBN)9781467364300 (ISBN)
    Konferens
    IEEE International Conference on Communications (ICC), 8-12 June, London, UK
    Tillgänglig från: 2016-04-20 Skapad: 2016-04-19 Senast uppdaterad: 2019-06-28Bibliografiskt granskad
    3. Performance Analysis of NOMA in Training-Based Multiuser MIMO Systems
    Öppna denna publikation i ny flik eller fönster >>Performance Analysis of NOMA in Training-Based Multiuser MIMO Systems
    2018 (Engelska)Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 1, s. 372-385Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper considers the use of non-orthogonal-multiple-access (NOMA) in multiuser MIMO systems in practical scenarios where channel state information (CSI) is acquired through pilot signaling. A new NOMA scheme that uses shared pilots is proposed. Achievable rate analysis is carried out for different pilot signaling schemes, including both uplink and downlink pilots. The achievable rate performance of the proposed NOMA scheme with shared pilot within each group is compared with the traditional orthogonal access scheme with orthogonal pilots. Our proposed scheme is a generalization of the orthogonal scheme, and can be reduced to the orthogonal scheme when appropriate power allocation parameters are chosen. Numerical results show that when downlink CSI is available at the users, our proposed NOMA scheme outperforms orthogonal schemes. However with more groups of users present in the cell, it is preferable to use multi-user beamforming instead of NOMA.

    Ort, förlag, år, upplaga, sidor
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
    Nyckelord
    Multiuser MIMO; NOMA; channel estimation; training; performance analysis
    Nationell ämneskategori
    Telekommunikation
    Identifikatorer
    urn:nbn:se:liu:diva-145161 (URN)10.1109/TWC.2017.2767030 (DOI)000422945400028 ()
    Konferens
    18th IEEE International Workshop on Signal Processing Advances for Wireless Communications (SPAWC)
    Anmärkning

    Funding Agencies|Swedish Research Council; Linkoping University Center for Industrial Information Technology; ELLIIT

    Tillgänglig från: 2018-02-13 Skapad: 2018-02-13 Senast uppdaterad: 2019-06-28
  • 90.
    Chiesa, Marco
    et al.
    Catholic University of Louvain, Belgium.
    Nikolaevskiy, Ilya
    Aalto University, Finland.
    Mitrovic, Slobodan
    Ecole Polytech Federal Lausanne, Switzerland.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten. ITMO University, Russia.
    Madry, Aleksander
    MIT, MA 02139 USA.
    Schapira, Michael
    Hebrew University of Jerusalem, Israel.
    Shenker, Scott
    University of Calif Berkeley, CA 94720 USA; Int Comp Science Institute, CA 94704 USA.
    On the Resiliency of Static Forwarding Tables2017Ingår i: IEEE/ACM Transactions on Networking, ISSN 1063-6692, E-ISSN 1558-2566, Vol. 25, nr 2, s. 1133-1146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fast reroute and other forms of immediate failover have long been used to recover from certain classes of failures without invoking the network control plane. While the set of such techniques is growing, the level of resiliency to failures that this approach can provide is not adequately understood. In this paper, we embarked upon a systematic algorithmic study of the resiliency of forwarding tables in a variety of models (i.e., deterministic/probabilistic routing, with packet-headerrewriting, with packet-duplication). Our results show that the resiliency of a routing scheme depends on the "connectivity" k of a network, i.e., the minimum number of link deletions that partition a network. We complement our theoretical result with extensive simulations. We show that resiliency to four simultaneous link failures, with limited path stretch, can be achieved without any packet modification/duplication or randomization. Furthermore, our routing schemes provide resiliency against k - 1 failures, with limited path stretch, by storing log(k) bits in the packet header, with limited packet duplication, or with randomized forwarding technique.

  • 91.
    Chuasomboon, Sasit
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    A comparison of ranging and localization techniques in indoor, urban, and tunnel environments2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Localization in wireless network sensors is an attractive research area nowadays. It is widely used in many applications e.g., indoor/outdoor asset tracking, intrusion detection, search-and-rescue, road traffic monitoring, and water quality monitoring. An accuracy and robustness to noise are important issues for localization which is needed to study and research to find the best solution. This thesis compares a ranging and localization techniques in indoor, urban and tunnel through a high performance ray-tracing simulator, Wireless InSiteR . Ranging techniques are based on two standard distance related measurement schemes e.g., RSS and TOA. A linearized least squares technique with reference node selection approach is chosen to estimate unknown nodes positions. Indoor and urban area are built-in floor plan and terrain available in simulator program, while tunnel is designed. In general, localization accuracy suffers from multipath and NLOS condition. This thesis also observes characteristic of them from ray-tracing method perspective. Firstly, important simulation parameters such as number ofreflections/diffractions, types of waveform, and types of antenna are analyzed oneach environments. Then, the models for distance estimation based on RSS and TOA measurements are created using measurements in simulated environments. The thesis proposes four scenarios for distance estimation model. They are line-of-sight (LOS), non-line-of-sight (NLOS), combination of LOS and NLOS, and NLOS with obstacle. All four scenarios models are derived along with model error distribution to observe characteristic of noise due to multipath and NLOS condition. Finally, the localization using only LOS condition measurements, is tested on each environment and compared results in term of accuracy.

  • 92.
    Cipriano, Antonio
    et al.
    Thales Communications and Security, Colombes, France.
    Agostini, Philippe
    Thales Communications and Security, Colombes, France.
    Blad, Anton
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska högskolan.
    Knopp, Raymond
    Institut Eurecom, Sophia Antipolis, France.
    Cooperative Communications with HARQ in a Wireless Mesh Network Based on 3GPP LTE2012Ingår i: Signal Processing Conference (EUSIPCO), 2012, IEEE , 2012, s. 1004-1008Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents some results from of the FP7 ICT-LOLA (achieving LOw LAtency in wireless communications) project on the design of clusterized wireless mesh network based on 3GPP LTE. First, we focus on the general MAC/PHY structure of the clusterized mesh network based on 3GPP LTE. Then, the concept of virtual link is presented for inter-cluster communications combining MAC layer forwarding, hybrid automatic repeat request (HARQ) and cooperative communications with Decode and Forward (DF). The goal of a virtual link is to enable low latency data transfer in inter-cluster communications. The virtual link solution is studied by simulations thanks to OpenAirInterface which integrates LTE MAC and PHY layer procedures, as well as adaptations needed for the LOLA wireless mesh network. Simulation results show that the proposed distributed solution smoothly adapts to the link conditions. A loss in throughput efficiency is the price to be paid in certain configurations for the distributed operation of the virtual link. Nevertheless, the technique helps in reducing the average number of transmissions thus contributing to improve the latency of the system.

  • 93.
    Daneshfar, Nader
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Resource Allocation with Service Availability & QoS Constraints in Mobile Fog Networks2017Ingår i: 2017 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS WORKSHOPS (INFOCOM WKSHPS), IEEE , 2017, s. 1018-1019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The evolution of the Internet of Things (IoT) is bringing Cloud services closer to the networks edge. Thus, fog networking presents itself as an approach aiming to utilize more and more resources in network edge devices to provide various networking tasks. This work presents an optimization formulation that minimizes the cost of executing a set of services, taking into account the availability of resources in mobile edge devices.

  • 94.
    Daneshfar, Nader
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Polishchuk, Valentin
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Service Allocation in a Mobile Fog Infrastructure under Availability and QoS Constraints2018Ingår i: 2018 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The next generation of mobile networks, namely SG, together with the Internet of Things (IoT) come with a large number of delay sensitive services. To meet their requirements, cloud services are migrating to the edge of the networks to reduce latency. The notion of fog computing, where the edge plays an active role in the execution of services, comes to meet the needs for the stringent requirements. Thus, it becomes of a high importance to address the problem of mapping services demands to infrastructure resources supply. This work addresses it taking into account the randomness of resource availability in a fog infrastructure. We introduce an integer optimization formulation to minimize the total cost under a guarantee of service execution despite the uncertainty of resources availability. Our results illustrate the effect of various system parameters, such as the diversity of the infrastructure server set, the availability of different infrastructure servers in the set, and the probability of service completion required by each service.

  • 95.
    Datsika, Eftychia
    et al.
    IQUADRAT Informat SL, Spain.
    Antonopoulos, Angelos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Verikoukis, Christos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Matching Theory for Over-the-Top Service Provision in 5G Networks2018Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 8, s. 5452-5464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern over-the-top (OTT) applications can be accessed via Internet connections over cellular networks, possibly shared and managed by multiple mobile network operators (MNOs). The OTT service providers (OSPs) need to interact with MNOs, requesting resources for serving users of different categories and with different quality-of-service requirements. For this purpose, OSPs need OTT application flow prioritization in resource allocation, while the network resource scheduling should respect network neutrality that forbids OSP prioritization. OSPs also need to request resources periodically, according to their performance goals, i.e., grade-of-service (GoS) level (blocking probability), causing delay in flows accommodation due to: 1) the time required for information exchange between OSPs and MNOs, affected by network congestion, and 2) the time required for flows to receive resources, affected by the number of concurrently active flows. Acknowledging the lack of OSP-oriented resource management approaches, we: 1) introduce a novel matching theoretic flow prioritization (MTFP) algorithm that respects network neutrality and 2) design analytical models that enable the thorough investigation of the GoS and delay performance in various scenarios. Our results (analytical and simulation) show that MTFP improves both metrics compared to the best effort approach, whereas its performance is affected by the number of flows and the resource allocation frequency.

  • 96.
    de Carvalho, Elisabeth
    et al.
    Aalborg University, Denmark.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Popovski, Petar
    Aalborg University, Denmark.
    RANDOM ACCESS FOR MASSIVE MIMO SYSTEMS WITH INTRA-CELL PILOT CONTAMINATION2016Ingår i: 2016 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING PROCEEDINGS, IEEE , 2016, s. 3361-3365Konferensbidrag (Refereegranskat)
    Abstract [en]

    Massive MIMO systems, where the base stations are equipped with hundreds of antenna elements, are an attractive way to attain unprecedented spectral efficiency in future wireless networks. In the "classical" massive MIMO setting, the terminals are assumed fully loaded and a main impairment to the performance comes from the inter-cell pilot contamination, i.e., interference from terminals in neighboring cells using the same pilots as in the home cell. However, when the terminals are active intermittently, it is viable to avoid inter-cell contamination by pre-allocation of pilots, while same-cell terminals use random access to select the allocated pilot sequences. This leads to the problem of intra-cell pilot contamination. We propose a framework for random access in massive MIMO networks and derive new uplink sum rate expressions that take intra-cell pilot collisions, intermittent terminal activity, and interference into account. We use these expressions to optimize the terminal activation probability and pilot length.

  • 97.
    de Carvalho, Elisabeth
    et al.
    Aalborg University, Denmark.
    Björnson, Emil
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Popovski, Petar
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Random Access Protocols for Massive MIMO2017Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 55, nr 5, s. 216-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    5G wireless networks are expected to support new services with stringent requirements on data rates, latency and reliability. One novel feature is the ability to serve a dense crowd of devices, calling for radically new ways of accessing the network. This is the case in machine-type communications, but also in urban environments and hotspots. In those use cases, the high number of devices and the relatively short channel coherence interval do not allow per-device allocation of orthogonal pilot sequences. This article addresses the need for random access by the devices to pilot sequences used for channel estimation, and shows that Massive MIMO is a main enabler to achieve fast access with high data rates, and delay-tolerant access with different data rate levels. Three pilot access protocols along with data transmission protocols are described, fulfilling different requirements of 5G services.

  • 98.
    De, Swades
    et al.
    Department of Electrical Engineering and Bharti School of Telecom, Indian Institute of Technology Delhi, India.
    Kaushik, K.
    Department of Electrical Engineering and Bharti School of Telecom, Indian Institute of Technology Delhi, India.
    Mishra, Deepak
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Stochastic Solar Harvesting Characterization for Sustainable Sensor Node Operation2019Ingår i: IET Wireless Sensor Systems, ISSN 2043-6386, s. 1-11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-sustainability of low power wireless sensor nodes is the need of the hour to realize ubiquitous wireless networks. To address this requirement we investigate the practical feasibility of sustainable green sensor network with solar-powered nodes. We propose simple yet efficient (i) analytical circuit model for solar panel assisted supercapacitor charging and (ii) statistical model for characterizing the solar intensity distribution. Combining these circuit and statistical models, we derive a novel solar charging rate distribution for the solar-powered supercapacitor. To gain analytical insights, we also propose an ideal diode based tight approximation for the practical supercapacitor charging circuit model. The accuracy of these proposed analytical models have been validated by extensive numerical simulations based on the real-world data, i.e., solar intensity profile and solar panel characteristics. The derived solar charging rate distribution is used to investigate the supported sampling rate of the node with different varying number of on-board sensors for a given energy outage probability. Results suggest that for an energy outage probability of 0.1, at New Delhi, a 40 F supercapacitor and a 3 W solar panel can support the operation of Waspmote with 6 on-board toxic gas sensors with a sampling rate of 65 samples per day. Further, we use the proposed models to estimate the practical supercapacitor and solar panel sizes required to ensure sustainability of sensor node operation at different geographical locations with varying sensing rate.

  • 99.
    Dimitriou, Ioannis
    et al.
    Department of Mathematics, University of Patras, 26500, Patras, Greece.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Performance Analysis of an Adaptive Queue-Aware Random Access Scheme with Random Traffic2018Ingår i: 2018 IEEE International Conference on Communications (ICC) Proceedings Kansas City, MO, USA 20–24 May 2018, IEEE Communications Society, 2018, s. 1-6Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this work, we consider an adaptive two-user random access scheme with multipacket reception (MPR) ca- pabilities. A user adapts its transmission characteristics based on the status of the other user. The users have external random traffic stored in their queues. We derive the stable throughput region of the system and the convexity conditions of this region. We derive analytically the queueing delay by formulating and solving a Riemann-Hilbert boundary value problem. Finally, we evaluate numerically the presented theoretical results. 

  • 100.
    Dimitriou, Ioannis
    et al.
    Department of Mathematics, University of Patras, Greece.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Stable Throughput and Delay Analysis of a Random Access Network With Queue-Aware Transmission2018Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 5, s. 3170-3184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we consider a two-user and a three-user slotted ALOHA network with multi-packet reception (MPR) capabilities and a queue-aware transmission control. In this setting, the nodes can adapt their transmission probabilities and their transmission parameters based on the status of the other nodes. Each user has external bursty arrivals that are stored in their infinite capacity queues. We focus on the fundamental problem of characterizing the stable throughput region, as well as of investigating the queueing delay. For the two- and the three-user cases we obtain the exact stability region, whereas in the former case we also provide the conditions under which the stability region is a convex set. We perform a detailed mathematical analysis to study the queueing delay in the two-user case by formulating two boundary value problems, the solution of which provide the generating function of the joint stationary probability distribution of the queue size at user nodes. Furthermore, for the two-user symmetric case with MPR we obtain a lower and an upper bound for the average delay without the need of solving a boundary value problem. In addition, we provide a closed form expression for the gap between the lower and the upper bound. The bounds as it is seen in the numerical results appear to be tight. Explicit expressions for the average delay are obtained for the symmetrical model with capture effect. We also provide a closed form expression for the optimal transmission probability that minimizes the average delay in the symmetric capture case. Finally, we evaluate numerically the presented theoretical results.

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