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  • 1.
    Asghar, Rizwan
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Liu, Dake
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    2-D Realization of WiMAX Channel Interleaver for Efficient Hardware Implementation2009In: Proceedings of World Academy of Science, Engineering and Technology (ISSN: 2070-3740), 2009, 25-29 p.Conference paper (Refereed)
    Abstract [en]

    The direct implementation of interleaver functions in WiMAX is not hardware efficient due to presence of complex functions. Also the conventional method i.e. using memories for storing the permutation tables is silicon consuming. This work presents a 2-D transformation for WiMAX channel interleaver functions which reduces the overall hardware complexity to compute the interleaver addresses on the fly.  A fully re-configurable architecture for address generation in WiMAX channel interleaver is presented, which consume 1.1 k-gates in total. It can be configured for any block size and any modulation scheme in WiMAX. The presented architecture can run at a frequency of 200 MHz, thus fully supporting high bandwidth requirements for WiMAX.

  • 2.
    Sanjuan, Joseba
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    3G Energy-Efficient Packet Handling Kernel Module for Android2012Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    The use of mobile devices is increasing due to the constant development of more advanced and appealing applications and computing features. However, these new features are very power hungry leading to short battery lifetimes. Research shows that a major reason for fast battery depletion is the excessive and inefficient use of the wireless interfaces. This thesis studies how we can attempt to increase the battery lifetime of the devices without having to sacrifice the usage of these advanced features in some applications.

    The thesis focuses on adapting the traffic pattern characteristics of mobile communication using a widespread wireless communication technology like 3G. Traffic pattern adaptation is performed at packet level in kernel space in Android. The data transfers are scheduled with the knowledge of the energy consumption characteristics of 3G. The performed measurements indicate that our solution can provide energy savings ranging from 7% to 59%.

    This work confirms that 3G conscious scheduling of network traffic reduces energy consumption, and that, both applications and energy saving libraries are potential directions to be further studied.

  • 3.
    Al Faisal, Muhammad Saud
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    6-9 GHz UWB Antenna-Low-Noise Amplifier Co-design2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    6 - 9 GHz antenna-low-noise amplifier co-design is a demanding task. Higher frequency band has new techniques for circuit design and matching. The usual lumped component matching technique is not an appropriate solution for High Frequency (HF) broad band. The new broad band demands transmission line matching. The low-power and high-data rate Ultra Wide Band (UWB) uses large portion of the communication radio-spectrum and wireless communication. The principal axis of this thesis is co-design in the frequency band of 6 - 9 GHz. The thesis has been divided in two parts, where first part includes implementation and evaluation of individual RF-circuits of circular monopole antenna, a band pass (BP) filter and a low-noise amplifier (LNA), while second part unite all three RF circuits and presents the co-design.

    Microstrip monopole antennas get more and more popular due to rapid change in the wireless communication. Higher datarate and even higher bandwidth demands a simple and compact ultra-wideband (UWB) antenna. Two monopole antennas circular and rectangular monopole antennas were designed. Simulated and experimental results of modified design indicate that antenna was achieved a VSWR of 1.2, with input reflection less then - 10 dB in 4 - 12 GHz band. These characteristic make the designed antenna suitable for various UWB application.

     The broad band matching and the flat gain are the two important factors for the UWB circuits. The co-design of antenna-low-noise amplifier utilizes a inter stage matching technique with a simple band pass filter, a third-order passive Chebychev filter is proposed as an input matching network. The filter achieves forward transmission less the - 0.8 dB and a return loss - 20 dB in 6 - 9 GHz band.

    Low-noise amplifier is the key RF circuit; minimal Noise Figure (NF) and the lower power consumption are desired parameters. The implemented low-noise amplifier (LNA) is the combination of bias network and ultra-wide band radio frequency (RF) choke. AVAGO Technologies pseudmorphic-high-electron-mobility transistor (PHEMT) with (SC-70) plastic package with nominal 0.2 µm gate length is used in amplifier. Passive distributed components of microstrip transmission line were used for matching, simulated results demonstrate maximum power gain of 12.74 dB and minimum noise figure (NFmin) of 1 dB is obtained.

    Finally all three individual RF circuits antenna, filter and low-noise amplifier are integrated into co-design and analyzed for 6 - 9 GHz band. Later on two more new designs are added. This co-design has large potential in Direct-broadcast-satellite (DBS) TV system, X-band radar detector, automotive radar, remote sensors, and Multichannel-multipoint-distribution-systems (MMDS). 

  • 4.
    Harikumar, Prakash
    et al.
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    A 0.4 V, sub-nW, 8-bit 1 kS/s SAR ADC in 65 nm CMOS for Wireless Sensor Applications2016In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, no 8, 743-747 p.Article in journal (Refereed)
    Abstract [en]

    This brief presents an 8-bit 1-kS/s successive approximation register (SAR) analog-to-digital converter (ADC), which is targeted at distributed wireless sensor networks powered by energy harvesting. For such energy-constrained applications, it is imperative that the ADC employs ultralow supply voltages and minimizes power consumption. The 8-bit 1-kS/s ADC was designed and fabricated in 65-nm CMOS and uses a supply voltage of 0.4 V. In order to achieve sufficient linearity, a two-stage charge pump was implemented to boost the gate voltage of the sampling switches. A custom-designed unit capacitor of 1.9 fF was used to realize the capacitive digital-to-analog converters. The ADC achieves an effective number of bits of 7.81 bits while consuming 717 pW and attains a figure of merit of 3.19 fJ/conversion-step. The differential nonlinearity and the integral nonlinearity are 0.35 and 0.36 LSB, respectively. The core area occupied by the ADC is only 0.0126 mm2.

  • 5.
    Zhang, Dai
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering. Catena Wireless Elect AB, Sweden.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    A 12.5-ENOB 10-kS/s Redundant SAR ADC in 65-nm CMOS2016In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, no 3, 244-248 p.Article in journal (Refereed)
    Abstract [en]

    This brief describes a 14-b 10-kS/s successive approximation register analog-to-digital converter (ADC) for biomedical applications. In order to achieve enhanced linearity, a uniform-geometry nonbinary-weighted capacitive digital-to-analog converter is implemented. In addition, a secondary-bit approach to dynamically shift decision levels for error correction is employed. To reduce the power consumption, the ADC also features a power-optimized comparator with bias control. Prototyped in a 65-nm CMOS process, the ADC consumes 1.98 mu W and provides an effective number of bit (ENOB) of 12.5 b at 0.8 V while occupying an active area of 0.28 mm(2).

  • 6.
    Fritzin, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A 3.3 V 72.2 Mbit/s 802.11n WLAN transformer-based power amplifier in 65 nm CMOS2010In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 64, no 3, 241-247 p.Article in journal (Refereed)
    Abstract [en]

    This paper describes the design of a power amplifier (PA) for 802.11n WLAN fabricated in 65 nm CMOS technology. The PA utilizes 3.3 V thick gate oxide (5.2 nm) transistors and a two-stage differential configuration with integrated transformers for input and interstage matching. A methodology used to extract the layout parasitics from electromagnetic (EM) simulations is described. For a 72.2 Mbit/s, 64-QAM, 802.11n OFDM signal at an average and peak output power of 11.6 and 19.6 dBm, respectively, the measured EVM is 3.8%. The PA meets the spectral mask up to an average output power of 17 dBm.

  • 7.
    Ahmed, Tanvir
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Garrido, Mario
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A 512-point 8-parallel pipelined feedforward FFT for WPAN2011In: 2011 Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), IEEE , 2011, 981-984 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a 512-point feedforward FFT architecture for wireless personal area network (WPAN). The architecture processes a continuous flow of 8 samples in parallel, leading to a throughput of 2.64 GSamples/s. The FFT is computed in three stages that use radix-8 butterflies. This radix reduces significantly the number of rotators with respect to previous approaches based on radix-2. Besides, the proposed architecture uses the minimum memory that is required for a 512-point 8-parallel FFT. Experimental results show that besides its high throughput, the design is efficient in area and power consumption, improving the results of previous approaches. Specifically, for a wordlength of 16 bits, the proposed design consumes 61.5 mW and its area is 1.43 mm2.

  • 8.
    Fritzin, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A 72.2Mbit/s Transformer-Based Power Amplifier in 65nm CMOS for 2.4GHz 802.11n WLAN2008In: Proceedings of 26th IEEE NORCHIP Conference, IEEE , 2008, 54-56 p.Conference paper (Refereed)
    Abstract [en]

    This paper describes the design of a power amplifier (PA) for WLAN 802.11n fabricated in 65 nm CMOS technology. The PA utilizes 3.3 V thick-gate oxide (5.2 nm) transistors and a two-stage differential configuration with two integrated transformers for input and interstage matching. For a 72.2 Mbit/s, 64-QAM, 802.11n OFDM signal at an average and peak output power of 11.6 dBm and 19.6 dBm, respectively, the measured EVM is 3.8%. The PA meets the spectral mask up to an average output power of 17 dBm.

  • 9.
    Curescu, C.
    et al.
    Ericsson Research, Torshamnsgatan 23, Kista, 164 83 Stockholm, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory.
    A bidding algorithm for optimized utility-based resource allocation in ad hoc networks2008In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, Vol. 7, no 12, 1397-1414 p.Article in journal (Refereed)
    Abstract [en]

    This paper proposes a scheme for bandwidth allocation in wireless ad hoc networks. The quality-of-service (QoS) levels for each end-to-end flow are expressed using a resource-utility function, and our algorithms aim to maximize aggregated utility. The shared channel is modeled as a bandwidth resource defined by maximal cliques of mutual interfering links. We propose a novel resource allocation algorithm that employs an auction mechanism in which flows are bidding for resources. The bids depend both on the flow's utility function and the intrinsically derived shadow prices. We then combine the admission control scheme with a utility-aware on-demand shortest path routing algorithm where shadow prices are used as a natural distance metric. As a baseline for evaluation, we show that the problem can be formulated as a linear programming (LP) problem. Thus, we can compare the performance of our distributed scheme to the centralized LP solution, registering results very close to the optimum. Next, we isolate the performance of price-based routing and show its advantages in hotspot scenarios, and also propose an asynchronous version that is more feasible for ad hoc environments. Further experimental evaluation compares our scheme with the state of the art derived from Kelly's utility maximization framework and shows that our approach exhibits superior performance for networks with increased mobility or less frequent allocations. © 2008 IEEE.

  • 10.
    Zhang, Jingcheng
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Huynh, Allan
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Ye, Qin-zhong
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A Communication Reliability Enhancement Framework for Wireless Sensor Network Using the ZigBee Protocol2012In: Sensors & Transducers Journal, ISSN 1726-5479, Vol. 135, no 12, 42-56 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the methods for the ZigBee network reliability enhancement and the battery life time optimization. The paper begins with the introduction of the common communication problems due to the broken links between sensor module and message relay, or between different relays. Extra message hand shake mechanisms are added to solve different problem mentioned at the beginning. Finally, a general purpose reliability enhancement component is developed as a state machine which can be work together with ZigBee protocol to enhance ZigBee network communication reliability. Moreover, the battery life time of the sensor module during link broken is considerably increased after the enhancement.

  • 11.
    Östh, Joakim
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Karlsson, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Serban, Adriana
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A Comparative Study of Single-Ended vs. Differential Six-Port Modulators for Wireless Communications2015In: IEEE Transactions on Circuits and Systems Part 1: Regular Papers, ISSN 1549-8328, E-ISSN 1558-0806, Vol. 62, no 2, 564-570 p.Article in journal (Refereed)
    Abstract [en]

    If present, nonlinear effects in a six-port modulator cause distortion and degradation of the quality of the modulated output waveform. How nonlinear effects occur and their impact on system performance were derived in a mathematical model. The model shows that non-ideal performance of the passive six-port correlator is the main contributor to nonlinear distortion. Simulations and measurements on two manufactured six-port modulators were used to validate the theory and to give deeper insight on system performance. It is shown that by using a differentially signaled six-port modulator instead of a single-ended six-port modulator, better performance is achieved over a wide bandwidth. For an error vector magnitude of less than 10%, the relative bandwidth was measured to 12% for the single-ended but 30% for the differentially signaled modulator

  • 12.
    Al-Taie, Mahir Jabbar Rashid
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A Comparison of EDMOS and Cascode Structures for PA Design in 65 nm CMOS Technology2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis addresses the potential of implementing watt-level class-AB Power Amplifier (PA) for WLAN in 65 nm CMOS technology, at 2.4 GHz frequency. In total, five PAs have been compared, where the examined parameters were output power (Pout), linearity, power added efficiency (PAE), and area consumption. Four PAs were implemented using conventional cascode topology with different combination of transistors sizes in 65nm CMOS, and one PA using a high-voltage Extended Drain MOS (EDMOS) device, implemented in the same 65 nm CMOS with no process or mask changes. All schematics were created using Cadence Virtuoso CAD tools. The test benches were created using the Agilent's Advance Design System ( ADS) and simulated with the ADS-Cadence dynamic link.

    The simulation results show that the EDMOS PA (L=350 nm) has the smallest area, but has harder to reach the required Pout. Cascode no. 3 (L= 500,260 nm) has the best Pout (29.1 dBm) and PAE (49.5 %). Cascode no. 2 (L= 500,350 nm) has the best linearity (low EVM). Cascode no. 1 (L=500,500 nm) has low Pout (27.7 dBm). Cascode no.4 (L=500,60 nm) has very bad linearity.

    The thesis also gives an overview for CMOS technology, discusses the most important aspects in RF PAs design, such as Pout, PAE, gain, and matching networks. Different PA classes are also discussed in this thesis.

  • 13.
    Chuasomboon, Sasit
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    A comparison of ranging and localization techniques in indoor, urban, and tunnel environments2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    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.

  • 14.
    Öberg, Lasse
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Xu, Youzhi
    A Complete Energy Dissipation Model for Wireless Sensor Networks2007In: In Proceedings of the International Conference on Sensor Technologies and Applications, Valencia, Spain, October 14-20, IEEE , 2007, 531-540 p.Conference paper (Refereed)
    Abstract [en]

    Advances in both microelectronics and wireless commu- nication technology have made it possible to develop and manufacture low cost and energy efficient sensor nodes. To compare different designs and protocols with respect to both energy and delay constraints an energy dissipation model is needed that takes these aspects into account. In this paper we propose a complete energy dissipation model for wire- less sensor networks that uses four operation states. These states are based on the basic sensor nodes architecture and actual working conditions of a sensor node. It also takes into account the transition between the operation states, such that a decision to change operation state can be more accurately determined. In this paper we also present mea- sured values for both the power consumed in each operation state and the time it takes to complete a transition between two operation states.

  • 15.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A Comprehensive Analysis of Optimal Link Scheduling for Emptying a Wireless Network2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless communications have become an important part of modern life. The ubiquitous wireless networks and connectivities generate exponentially increasing data traffic. In view of this, wireless network optimization, which aims at utilizing the limited resource, especially spectrum and energy, as efficiently as possible from a network perspective, is essential for performance improvement and sustainable development of wireless communications.

    In the dissertation, we focus on a fundamental problem of wireless network optimization, link scheduling, as well as its subproblem, link activation. The problem type arises because of the nature of wireless media and hence it is of relevance to a wide range of networks with multiple access. We freshen these classic problems up by novel extensions incorporating new technologies of interference management or with new performance metrics. We also revisit the problems in their classic setup to gain new theoretical results and insights for problem-solving. Throughout the study, we consider the problems with a general setup, such that the insights presented in this dissertation are not constrained to a specific technology or network type. Since link activation and scheduling are key elements of access coordination in wireless communications, the study opens up new approaches that significantly improve network performance, and eventually benefit practical applications.

    The dissertation consists of five research papers. The first paper addresses maximum link activation with cooperative transmission and interference cancellation. Papers II and III investigate the minimum-time link scheduling problem in general and a particular class of networks, respectively. In Paper IV, we consider the scheduling problem of emptying a network in its broad form and provide a general optimality condition. In Paper V, we study the scheduling problem with respect to age of information.

    List of papers
    1. Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    Open this publication in new window or tab >>Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    2017 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, 408-421 p.Article in journal (Other academic) Published
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

    Place, publisher, year, edition, pages
    IEEE, 2017
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112447 (URN)10.1109/TMC.2016.2546906 (DOI)
    Conference
    2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), September 2-5, Washington DC, DC, USA
    Note

    Funding agencies: Swedish Research Council; EU FP7 Marie Curie [324515, 329313]; National Science Foundation [CCF-0728966, CCF-1420651]; ONR [N000141410107]

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2017-03-27Bibliographically approved
    2. Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    Open this publication in new window or tab >>Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    2014 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, Vol. 60, no 2, 1083-1100 p.Article in journal (Refereed) Published
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keyword
    Algorithm; optimality; scheduling; wireless networks
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-104836 (URN)10.1109/TIT.2013.2292065 (DOI)000330286100022 ()
    Available from: 2014-02-28 Created: 2014-02-28 Last updated: 2016-09-15
    3. Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    Open this publication in new window or tab >>Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    2015 (English)In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 3, no 3, 322-331 p.Article in journal (Other academic) Published
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2015
    Keyword
    algorithm, interference, optimality, scheduling, wireless networks
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112446 (URN)10.1109/TCNS.2015.2512678 (DOI)
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2016-11-25Bibliographically approved
    4. A general optimality condition of link scheduling for emptying a wireless network
    Open this publication in new window or tab >>A general optimality condition of link scheduling for emptying a wireless network
    2016 (English)In: 2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, IEEE , 2016, 1446-1450 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues of the source nodes, and provide a unified mathematical formulation that accommodates all meaningful settings of link transmission rates and network configurations. We prove that, any scheduling problem is equivalent to solving a convex problem defined over the convex hull of the rate region. Based on the fundamental insight, a general optimality condition is derived, that yields a unified treatment of optimal scheduling. Furthermore, we demonstrate the implications and usefulness of the result. Specifically, by applying the theoretical insight to optimality characterization and complexity analysis of scheduling problems, we can both unify and extend previously obtained results.

    Place, publisher, year, edition, pages
    IEEE, 2016
    Series
    IEEE International Symposium on Information Theory. Proceedings, ISSN 2157-8095, E-ISSN 2157-8117
    Keyword
    convex programming;radio links;radio networks;telecommunication scheduling;convex hull;convex problem;general optimality condition;link scheduling;link transmission rates;network configurations;optimal scheduling;source nodes;wireless network;Complexity theory;Information theory;Interference;Optimal scheduling;Processor scheduling;Scheduling;Wireless networks;complexity;optimality;scheduling;wireless networks
    National Category
    Computer Engineering Information Systems Software Engineering
    Identifiers
    urn:nbn:se:liu:diva-131357 (URN)10.1109/ISIT.2016.7541538 (DOI)000390098701102 ()
    Conference
    IEEE International Symposium on Information Theory (ISIT), 2016, Universitat Pompeu Fabra, Barcelona, Spain, July l0-l5, 2016
    Available from: 2016-09-15 Created: 2016-09-15 Last updated: 2017-01-30Bibliographically approved
  • 16.
    Gunnarsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Concept of Power Control in Cellular Radio Systems1999Report (Other academic)
    Abstract [en]

    Due to the rapid expansion of the cellular radio systems market, and the need for wireless multimedia services, the available resources have to be utilized efficently. A common strategy is to control the transmitter powers of the mobiles and base stations. However, when applying power control to real systems, a number of challenges are prevalent. The performance is limited by time delays, nonlinearities and the availability of measurements and adequate quality measures. In this paper we present a Power Regulator concept, which comprises an Unknown Input Observer, a Quality Mapper and a Power Control Algorithm. The applicability of the concept is exemplified using frequency hopping GSM, and simulations indicate benefits of employing the proposed concept.

  • 17.
    Gunnarsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Concept of Power Control in Cellular Radio Systems1999In: Proceedings of the 14th World Congress, 1999Conference paper (Refereed)
    Abstract [en]

    Due to the rapid expansion of the cellular radio systems market, and the need for wireless multimedia services, the available resources have to be utilized efficently. A common strategy is to control the transmitter powers of the mobiles and base stations. However, when applying power control to real systems, a number of challenges are prevalent. The performance is limited by time delays, nonlinearities and the availability of measurements and adequate quality measures. In this paper we present a Power Regulator concept, which comprises an Unknown Input Observer, a Quality Mapper and a Power Control Algorithm. The applicability of the concept is exemplified using frequency hopping GSM, and simulations indicate benefits of employing the proposed concept.

  • 18.
    Chhetri, Dhurv
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Manyam, Venkata Narasimha
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A Continuous-Time ADC and DSP for Smart Dust2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Recently, smart dust or wireless sensor networks are gaining more attention.These autonomous, ultra-low power sensor-based electronic devices sense and process burst-type environmental variations and pass the data from one node (mote) to another in an ad-hoc network. Subsystems for smart dust are typically the analog interface (AI), analog-to-digital converter (ADC), digital signal processor (DSP), digital-to-analog converter (DAC), power management, and transceiver for communication.

    This thesis project describes an event-driven (ED) digital signal processing system (ADC, DSP and DAC) operating in continuous-time (CT) with smart dust as the target application. The benefits of the CT system compared to its conventional counterpart are lower in-band quantization noise and no requirement of a clock generator and anti-aliasing filter, which makes it suitable for processing burst-type data signals.

    A clockless EDADC system based on a CT delta modulation (DM) technique is presented. The ADC output is digital data, continuous in time, known as “data token”. The ADC employs an unbuffered, area efficient, segmented resistor-string (R-string) feedback DAC. A study of different segmented R-string DAC architectures is presented. A comparison in component reduction with prior art shows nearly 87.5% reduction of resistors and switches in the DAC and the D flip-flops in the bidirectional shift registers for an 8-bit ADC, utilizing the proposed segmented DAC architecture. The obtained SNDR for the 3-bit, 4-bit and 8-bit ADC system is 22.696 dB, 30.435 dB and 55.73 dB, respectively, with the band of interest as 220.5 kHz.

    The CTDSP operates asynchronously and process the data token obtained from the EDADC. A clockless transversal direct-form finite impulse response (FIR) low-pass filter (LPF) is designed.

    Systematic top-down test-driven methodology is employed through out the project. Initially, MATLAB models are used to compare the CT systems with the sampled systems. The complete CTDSP system is implemented in Cadence design environment.

    The thesis has resulted in two conference contributions. One for the 20th European Conference on Circuit Theory and Design, ECCTD’11 and the other for the 19th IFIP/IEEE International Conference on Very Large Scale Integration, VLSI-SoC’11. We obtained the second-best student paper award at the ECCTD.

  • 19.
    Yuan, Di
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Communications and Transport Systems.
    A Distributed Hybrid Algorithm for Broadcasting through a Virtual Backbone in Wireless Ad Hoc Networks2006In: Proceedings of IEEE International Symposium on Wireless Pervasive Computing (ISWPC), 2006Conference paper (Refereed)
  • 20.
    Sajid, Muhammad
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Siddiqui, Imran
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis a distributed, dynamic, load aware, joint power and frequency allocation protocol for 4G networks along with system-level simulated results are presented. In all cellular networks, a key limiting factor for throughput is inter-cell interference, especially at the cell edges. Several methods have been proposed and adopted in each mobile network generation to cancel or suppress its effects, whereas each method has its drawbacks in terms of receiver complexity or additional control nodes. However, the proposed protocol presented here does not impose any architectural changes.  In 4G networks such as LTE, the choice of OFDMA for the air interface has paved the way for selective frequency and power allocation in the available spectrum. Taking advantage of this opportunity, fractional frequency reuse (FFR) has been proposed in OFDMA based mobile networks in order to reduce the throughput loss at the cell edges due to inter-cell interference. In FFR, center users lose part of available spectrum that is dedicated to the edge users.  Our protocol aims to minimize this loss of center users incurred by FFR, at the cost of minimal degradation at the edges.

    An eNodeB, only when overloaded, requests its neighbours’ edge band to be used for its center users at a reduced power level. This is done via small message exchange between the eNodeBs. The neighbors of the overloaded eNodeBs solve a small local knapsack problem to decide whether band lending is feasible or not. A distinguishing feature of this protocol is the power level adjustment for the borrowed band, which is mutually decided by the borrower and lender. The band is released when it is not needed or it is causing unacceptable loss to the lender. The implementation is done in a Matlab based LTE system level simulator. For the implementation of our protocol in the simulator, starting point was implementation of FFR-3 functionality, a prerequisite and a baseline for comparison with our protocol.

    Results are compared among three different setups of re-use1, FFR-3 and our protocol by varying number of overloaded eNodeBs for various numbers of scenarios and the comparison is made based on the center users’ throughput, edge users’ throughput. An estimation of time and protocol overhead is also presented. We have observed center users’ throughput gain up to 46%, at the cost of 9% edge users’ throughput loss, when compared to the classic FFR-3 scheme. The overall system throughput goes up to 26 % in heavily loaded scenario.

     

    The utility of the protocol for an LTE system is evident from the results, which is supported by the dynamic and decentralized nature of the protocol. This ensures better utilization of spectrum, by temporarily allocating more bandwidth where it is needed more.

  • 21.
    Korishe, Abdulah
    Linköping University, Department of Electrical Engineering, Electronics System.
    A Driver Circuit for Body-Coupled Communication2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main concept of Body-Coupled Communication (BCC) is to transmit the electrical information through the human body as a communication medium by means of capacitive coupling. Nowadays the current research of wireless body area network are expanding more with the new ideas and topologies for better result in respect to the low power and area, security, reliability and sensitivity since it is first introduced by the Zimmerman in 1995. In contrast with the other existing wireless communication technology such as WiFi, Bluetooth and Zigbee, the BCC is going to increase the number of applications as well as solves the problem with the cell based communication system depending upon the frequency allocation. In addition, this promising technology has been standardized by a task group named IEEE 802.15.6 addressing a reliable and feasible system for low power in-body and on-body nodes that serves a variety of medical and non medical applications.

    The entire BAN project is divided into three major parts consisting of application layer, digital baseband and analog front end (AFE) transceiver. In the thesis work a strong driver circuit for BCC is implemented as an analog front end transmitter (Tx). The primary purpose of the study is to transmit a strong signal as the signal is attenuated by the body around 60 dB. The Driver circuit is cascaded of two single-stage inverter and an identical inverter with drain resistor. The entire driver circuit is designed with ST65 nm CMOS technology with 1.2 V supply operated at 10 MHz frequency, has a driving capability of 6 mA which is the basic requirement. The performance of the transmitter is compared with the other architecture by integrating different analysis such as corner analysis, noise analysis and eye diagram. The cycle to cycle jitter is 0.87% which is well below to the maximum point and the power supply rejection ratio (PSRR) is 65 dB indicates the good emission of supply noise. In addition, the transmitter does not require a filter to emit the noise because the body acts like a low pass filter.

    In conclusion the findings of the thesis work is quite healthy compared to the previous work. Finally, there is some point to improve for the driver circuit in respect to the power consumption, propagation delay and leakage power in the future.   

  • 22.
    Liang, Kai
    et al.
    Xidian University, Peoples R China.
    Zhao, Liqiang
    Xidian University, Peoples R China.
    Yang, Kun
    University of Essex, England.
    Zheng, Gan
    University of Essex, England; University of Luxembourg, Luxembourg.
    Ding, Wei
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Fair Power Splitting Algorithm for Simultaneous Wireless Information and Energy Transfer in CoMP Downlink Transmission2015In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. 85, no 4, 2687-2710 p.Article in journal (Refereed)
    Abstract [en]

    A power splitting approach for simultaneous wireless information and energy transfer is provided in this paper. We consider coordinated multipiont downlink transmission with M base stations (BSs) and J mobile stations (MSs). The main goal of this paper is to maximize per-MS data rate and receiving energy by dynamically optimizing transmitting beamformer. To improve fairness, this problem can be formulated to maximize the minimum rate of all J MSs with per-BS transmitting power constraints and per-MS receiving energy constraints, which is NP-hard problem. Minimum mean square error receiver, affine approximation and alternative convex optimization (ACO) methods are introduced to decompose the original NP-hard problem to several convex subproblems which can be solved by second-order cone programming with low rank (which is equal to the number of data streams) solutions, and then a fast heuristic algorithm is provided to solve the original problem. Numerical results show that the proposed algorithm can achieve fairness, and outperforms sum rate scheme in terms of fairness and outage probability. The fast convergency also demonstrates the proposed algorithms good performance.

  • 23.
    Bauer, Joanna
    et al.
    University of Bergen.
    Haugland, Dag
    University of Bergen.
    Yuan, Di
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Communications and Transport Systems.
    A fast local search method for minimum energy broadcast in wireless ad hoc networks2009In: OPERATIONS RESEARCH LETTERS, ISSN 0167-6377, Vol. 37, no 2, 75-79 p.Article in journal (Refereed)
    Abstract [en]

    Local search methods are often used to reduce the power consumption of broadcast routing in wireless networks. For a classic method, sweep, the best available time complexity result is O(vertical bar V vertical bar(4)). We present an O(vertical bar V vertical bar(2))-time method, which exhaustively removes unnecessary transmissions yielding a solution comparable to that of sweep.

  • 24.
    Zappone, Alessio
    et al.
    TU Dresden, Dresden, Germany.
    Björnson, Emil
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Sanguinetti, Luca
    University of Pisa, Italy; CentraleSupelec, France.
    Jorswieck, Eduard
    TU Dresden, Dresden, Germany.
    A Framework for Globally Optimal Energy-Efficient Resource Allocation in Wireless Networks2016Conference paper (Refereed)
  • 25.
    Kuiper, Erik
    et al.
    Saab Aeronautical, Linkoping, Sweden .
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A framework for performance analysis of geographic delay-tolerant routing2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, no 184Article in journal (Refereed)
    Abstract [en]

    A major tool used for evaluating routing protocols in ad hoc and delay-tolerant networks is simulation. Whereas the results from simulations give good insights, they are limited to the specific scenario set-up that is used. If the scenario changes, new and often time-consuming simulations have to be run. Moreover, the simulation time in packet-level simulators with fairly realistic physical layer implementation, such as ns-2, generally grows rapidly in the number of nodes. This practically limits the number of nodes in a simulation, even if the limit can be extended by the use of simulation federations. Larger scenarios can also be facilitated by the use of more abstraction in the physical layer; abstractions that may impact the validity of the results. In this article, we present the forward-wait framework--a mathematical model describing the packet movements for opportunistic geographic delay-tolerant routing protocols. By describing packet movements as a sequence of alternating forwarding and waiting phases, the framework can accurately predict the routing performance. Key input parameters to the framework are random variables describing the forwarding and waiting phases. We show how the properties of the random variables can be derived, both via abstract modeling and small scale ns-2 simulation data. The model is then used to demonstrate the prediction capabilities of the framework in providing results that are close to the (much slower) packet-level simulations.

  • 26.
    Nilsson, Anders
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Tell, Eric
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Liu, Dake
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    A fully programmable Rake-receiver architecture for multi-standard baseband processors2005In: Proceedings of the Intl. conference on Networks and Communication systems, NCS2005, 2005, 292-297 p.Conference paper (Other academic)
    Abstract [en]

    Programmability will be increasingly important in future multi-standard radio systems. We are presenting a fully programmable and flexible DSP platform capable of efficiently performing channel estimation and Maximum Ratio Combining (MRC) based channel equalization for a large number of wireless transmission systems in software. Our processor is based on a programmable DSP processor with SIMD-computing clusters. We also map Rake receiver kernel functions supporting a large number of commonWireless LAN and 3G standards to this microarchitecture. The use of the inherit flexibility for future standards is also discussed. Benchmarking show that with the proposed instruction set architecture, our architecture can support channel estimation, equalization and decoding of: WCDMA (FDD/TDD-modes), TD-SCDMA and the higher data rates of IEEE 802.11b (CCK) at clock frequency not exceeding 76 MHz.

  • 27.
    Zhang, Jingcheng
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Huynh, Allan
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Ye, Qin-Zhong
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A Fully Wireless Monitoring and Control System for Protecting Cultural Heritage2011In: Proceedings of 2011 20th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises WETICE 2011, IEEE , 2011, 250-255 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a component based wireless monitoring and control system. The system is introduced from both the system architecture and function point of view. The paper begins with the introduction of the component design and the communication interaction between them. The system is composed by three components, the wireless sensor network, the local server and the main server. Wireless sensor networks are deployed in different locations for remote monitoring and control purpose. The monitoring results and control commands are synchronized between the main server and wireless sensor networks via local servers. The test results of the battery life time calculation and remote monitoring field test results are presented in the end of the paper.

  • 28.
    He, Qing
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Ephremides, Anthony
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A general optimality condition of link scheduling for emptying a wireless network2016In: 2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, IEEE , 2016, 1446-1450 p.Conference paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues of the source nodes, and provide a unified mathematical formulation that accommodates all meaningful settings of link transmission rates and network configurations. We prove that, any scheduling problem is equivalent to solving a convex problem defined over the convex hull of the rate region. Based on the fundamental insight, a general optimality condition is derived, that yields a unified treatment of optimal scheduling. Furthermore, we demonstrate the implications and usefulness of the result. Specifically, by applying the theoretical insight to optimality characterization and complexity analysis of scheduling problems, we can both unify and extend previously obtained results.

  • 29.
    Liu, Dake
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Computer Engineering.
    Tell, Eric
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Computer Engineering.
    A Hardware Architecture for a Multi Mode Block Interleaver2004In: International Conference on Circuits and Systems for Communications, ICCSC,2004, 2004Conference paper (Refereed)
    Abstract [en]

    We are interested in developing a programmable baseband processor for software defined radio and are trying to find configurable hardware blocks that can be used in multiple radio standards, including for example wireless LAN and 3G standards. This paper suggests an architecture for a multi mode block interleaver that is suitable e.g. for the IEEE 802.11a and 802.11g standards. Our implementation is based on a special matrix memory to which data is written as rows but read out as columns. To enable a comparison, an interleaver for theWireless LAN standard 802.11a has been implemented both using our suggested architecture and using a traditional interleaver implementation based on a bit memory. Our implementation reaches a significantly higher performance and a lower power consumption with no extra area. The price to pay is a small loss of generality.

  • 30.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Shahzad, Muhammad Adil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

  • 31.
    Tang, Weihua
    Linköping University, Department of Electrical Engineering.
    A Low-Power Implementation of Turbo Decoders2007Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    In the 3G standards, wireless communication system can support 2 Mb/s. With this data rate, multimedia communication is realized on handset. However, it is expected that new applications will require even higher data rates in future. In order to fulfil the growing requirement of high data rate, 100 Mb/s is considered as the aim of 4G standards. Such high data rate will result in very large power consumption, which is unacceptable considering the current battery capability. Therefore, reducing the power consumption of turbo decoders becomes a major issue to be solved. This report explores new techniques for implementing low power, small area and high throughput turbo decoders.

  • 32.
    Gustafsson, Per-Ola
    et al.
    Linköping University, Department of Science and Technology.
    Ohlsson, Marcus
    Linköping University, Department of Science and Technology.
    A Menu-based Universal Control Protocol2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    This thesis-project aims to research the possibilities of new wireless technologies in general control-situations. We have studied different existing control protocols, and developed a new protocol focusing on textbased menus. Our protocol is scaleable, easy to implement, and platform- and media independent. Since our protocol supports Plug and Play with dynamically allocated id’s, it does not require a unique id in the hardware.

    To test the protocol we have developed a prototype system, consisting of a mobile phone connected to a server, which in turn is connected to two slave units, controlling peripheral equipment on 220 Volt.

    The phone is an Ericsson T28, equipped with a Bluetooth unit. The server is runningthe real-time OS eCos on an ARM 7TDMI Evaluation Kit, and the slave units consist of two developer boards equipped with PIC-processors. Communication between the phone and the server is done over Bluetooth. However we did not find a working Bluetooth protocol stack ported to eCos, so a serial cable was used instead. Communication between the server and the slaves is done over a RS-485 serial network which simulates the traffic over a radio-network.

    The results show that our protocol is working, and that our system would be easy to implement, cheap to produce and very scalable.

  • 33.
    Andersson, Anders
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Östh, Joakim
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A MMIC GaAs up-converter from 350 MHz to 1835 MHz realized both in a HBT diode-mixer topology and pHEMT resistive FET-mixer topology2006Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Two mixers for up-conversion from an IF frequency of 350 MHz to a RF frequency of 1835 MHz have been designed and simulated to be used in Ericsson.s radio link system MINI-LINK. One mixer uses diodes in a balanced structure, and the other one use resistive FET-mixers, also in a balanced structure.

    Both implemented in a GaAs MMIC process; for the diode mixer TriQuint HBT2 and for the resistive FET-mixer TriQuint 0.25 um pHEMT. The mixers were designed to work with input LO-power of 0 dBm and an IF-power of -20 dBm. For the diode based mixer with an active LO balun the conversion gain is 5.7 dB, P-1dB 15 dBm and the LO-suppression -22 dB. For the resistive FET-mixer the conversion gain is 11 dB, IIP3 26 dBm, P-1dB 15 dBm and the LO-suppression -49 dB. The data given is based on simulations; no wafers have been processed at this time. The chip-area the final design will occupy is approximated to 1.8 mm^2 for the diode mixer and approximately 1.9 mm^2 for the resistive FET-mixer. For both of the mixer types an off-chip balun for the IF-frequency is the only external component needed.

  • 34.
    Qamar, Danial
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Rosenkrantz, Patrik
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A model for new employees in electrical system and automation2013Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Syftet med det här arbetet är att konstruera ett arbetsprov, för att kunna förenkla processen vid en arbetsintervju. Arbetsprovet kommer att användas som ett moment i en arbetsintervju där den sökande får lösa ett par uppgifter och sedan förklara hur den tänkt.

    Erbjudandet för att göra detta examensarbete kom från ett företag som heter IKG som startades 1990 och är ett entreprenörsdrivet teknik och IT-konsultföretag med extra kompetenser inom till exempel el/anläggningskonstruktion, elkraftsystem och automation.

    Resultatet av detta examensarbete blev tre stycken arbetsprov med inriktning på olika områden av elteknik och automation.

  • 35.
    Duong, Le
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A model to predict the coverage of VHF transmissions2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    VHF står för "Very High Frequency" och är ett frekvensband som ligger i området 30 - 300 MHz. Maritim VHF är standard för Sjöfartsverket och fungerar över hela världen. Det är ett kommunikationssystem som bidrar till ökad säkerhet och kan rädda liv på sjön. Andra vanliga kommunikationssystem som mobiltelefoni fungerar inte tillförlitligt. Idag fungerar mobiltelefoni i stora delar av skärgården och längs kusterna men när det gäller kommunikation mellan fartyg längre ut till havs är den maritima VHF-kommunikationen överlägsen. Sjöfartsverket driver för sitt eget och kunders behov ett mobilradionätverk kallat kustradionätverket. Radiotrafiken i nätet sker både på Very High Frequency (VHF) och Medium frequency (MF). VHF-systemet är ett internationellt system som bland annat används till att kommunicera till sjöss och den trafiken befinner sig i frekvensbandet 155.5 - 162.025 MHz. Inom VHF-bandet finns det 55 kanaler. Kanalerna vid kustradiostationen kallas för duplexkanaler och innebär att kustradiostationerna sänder och tar emot signaler på två olika frekvenser. Radioutbredningen hos antennen som är installerad på basstationen har riktverkan i vissa riktningar och dämpningar i andra. Detta kan ses i strålningsdiagrammet under kapitlet "Täckningsmodell" och avsnittet antennen. Andra faktorer som kan påverka radioutbredningen är förluster i basstationenssystemet, topologin hos området mellan sändare och mottagare samt väderberoende utbredningsegenskaper. Genom att hitta de tänkbara faktorer som påverkar signalutbredningen kan en täckningsmodell förutses. Det är förluster som finns i basstationen, radiolänken samt förluster vid mottagarantennen.

  • 36.
    Asghar, A.M.
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Malick, M
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Karlsson, M
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hussain, A
    Chalmers, Sweden .
    A multiwideband planar monopole antenna for 4G devices2013In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 55, no 3, 589-593 p.Article in journal (Refereed)
    Abstract [en]

    This article presents a compact multiband planar antenna designed for mobile phone applications.The antenna performance is achieved by designing a planar monopole antenna into distributed radiating elements. The proposed antenna is comprised of a chopped circular radiator appended with a meander line and an L-strip coupled element, which is an extension of the ground plane. The combination of a chopped circular patch and L-shaped coupling strip residing on the top side generates lower band while upper band resonances are attained separately by chopped circular resonator and meander line elements. The antenna shows a planar structure which occupies an area of 56 x 17.6 mm and can be directly printed onto a circuit board at low cost making it especially suitable for mobile phone applications. The manufactured antenna is experimentally verified and covers several wireless communication bands, such as LTE 750, GSM 850, GSM 900, DCS, UMTS-2110, Bluetooth, WLAN, WiMAX, and UWB. The high frequency structure simulation is used to design and analyze the antenna performance, and a practical structure was fabricated and tested. The measured and simulated return loss show good agreement.

  • 37.
    Seong, K
    et al.
    Korea Mil Acad, Dept Elect Engn, Seoul, South Korea Kwangju Inst Sci & Technol, Dept Informat & Commun, Kwangju, South Korea Swedish Def Res Agcy, Dept Comm, Div Command & Control Warfare Technol, Linkoping, Sweden.
    Choi, Y
    Korea Mil Acad, Dept Elect Engn, Seoul, South Korea Kwangju Inst Sci & Technol, Dept Informat & Commun, Kwangju, South Korea Swedish Def Res Agcy, Dept Comm, Div Command & Control Warfare Technol, Linkoping, Sweden.
    Kim, K
    Korea Mil Acad, Dept Elect Engn, Seoul, South Korea Kwangju Inst Sci & Technol, Dept Informat & Commun, Kwangju, South Korea Swedish Def Res Agcy, Dept Comm, Div Command & Control Warfare Technol, Linkoping, Sweden.
    Joensson, C
    Korea Mil Acad, Dept Elect Engn, Seoul, South Korea Kwangju Inst Sci & Technol, Dept Informat & Commun, Kwangju, South Korea Swedish Def Res Agcy, Dept Comm, Div Command & Control Warfare Technol, Linkoping, Sweden.
    A new adaptive transmission scheme for wireless communication systems utilizing frequency diversity2002In: Wireless personal communications, ISSN 0929-6212, Vol. 23, no 1, 45-53 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a new adaptive transmission scheme for wireless communication systems utilizing frequency diversity combining technique. The capacity of Rayleigh fading chanels under the proposed adaptive transmission scheme is analytically evaluated and compared with the capacity under the conventional adaptive transmission scheme. The results show that the channel capacity under the new adaptive scheme exceeds that under the conventional one, and this capacity increment becomes more apparent especially for lower average carrier-to-noise ratio (CNR) and larger number of diversity branches. Also, the capacity with the new scheme isshown to exceed even the capacity of AWGN channels for some small values of CNR and large number of diversity branches.

  • 38.
    Capone, Antonio
    et al.
    Politecn Milan.
    Chen, Lei
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gualandi, Stefano
    Politecn Milan.
    Yuan, Di
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Communications and Transport Systems.
    A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model2011In: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, ISSN 1536-1276, Vol. 10, no 5, 1368-1372 p.Article in journal (Refereed)
    Abstract [en]

    A fundamental and computationally challenging optimization task in wireless networks is to maximize the number of simultaneous transmissions, subject to signal-to-noise-and-interference ratio (SINR) requirements at the receivers. The conventional approach guaranteeing global optimality is to solve an integer programming model with explicit SINR constraints. These constraints are however numerically very difficult. We develop a new integer programming algorithm based on a much more effective representation of the SINR constraints. Computational experiments demonstrate that the new approach performs significantly better in proving optimality.

  • 39.
    Håkansson, Pär
    et al.
    Linköping University, Department of Science and Technology.
    Huynh, Allan
    Linköping University, Department of Science and Technology.
    Gong, Shaofang
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    A new concept of wireless data transmission of extremely high data rate over 10 Gbps2005Report (Other academic)
  • 40.
    Raza Khan, Hashim
    et al.
    NED University of Engn and Technology, Pakistan .
    Fritzin, Jonas
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    ul Wahab, Qamar
    NED University of Engn and Technology, Pakistan .
    A parallel circuit differential class-E power amplifier using series capacitance2013In: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 75, no 1, 31-40 p.Article in journal (Refereed)
    Abstract [en]

    Class-E amplifiers are attractive for wireless handsets because of their high efficiency and simple implementation. However, it requires inductors in its output matching network that are inherently low Q components affecting efficiency and may require significantly large area in fully integrated implementation. In this paper a novel approach of implementing parallel circuit differential class-E amplifier is presented. Instead of using an inductor parallel to the transistor drain of each amplifier, a single capacitor at the single ended side of the balun provides the parallel inductance effect to the switching transistors. As a result, number of inductors required for circuit implementation is reduced which means reduced losses, less area and better tuning of reactance can be achieved. A test circuit is implemented in 0.13 mu m CMOS process. Measurement results verify the validity of the concept. The Power Amplifier achieves 22 dBm output power at 2.4 GHz from a 2.5 V with an overall Power Added Efficiency of 38 %.

  • 41.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, RTSLAB - Real-Time Systems Laboratory. Linköping University, The Institute of Technology.
    A Partition-tolerant Manycast Algorithm for Disaster Area Networks2009In: 28TH IEEE INTERNATIONAL SYMPOSIUM ON RELIABLE DISTRIBUTED SYSTEMS, PROCEEDINGS, IEEE Computer Society, 2009, 156-165 p.Conference paper (Refereed)
    Abstract [en]

    Information dissemination in disaster scenarios requires timely and energy-efficient communication in intermittently connected networks. When the existing infrastructure is damaged or overloaded, we suggest the use of a manycast algorithm that runs over a wireless mobile ad hoc network, and overcomes partitions using a store-and-forward mechanism. This paper presents a random walk gossip protocol that uses an efficient data structure to keep track of already informed nodes with minimal signalling. Avoiding unnecessary transmissions also makes it less prone to overloads. Experimental evaluation shows higher delivery ratio, lower latency, and lower overhead compared to a recently published algorithm.

  • 42.
    Bergfeldt, Erik
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. Ericsson Research, Stockholm, Sweden.
    Ekelin, Svante
    Ericsson Research, Stockholm, Sweden.
    Karlsson, Johan M
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Performance Study of Bandwidth Measurement Tools over Mobile Connections2009In: 2009 IEEE 69th Vehicular Technology Conference Spring: Proceedings, IEEE , 2009, 2978-2982 p.Conference paper (Refereed)
    Abstract [en]

    The knowledge of the present available bandwidth on a network path is essential in numerous contexts, such as network management and streaming applications. A network path nowadays often contains at least one wireless link. This is obviously true for mobile users having a wireless connection to the Internet through a laptop or mobile terminal. The existing tools for measuring end-to-end available bandwidth are developed and optimized for paths with only guided media links. Since the characteristics for wired links and radio links differ in many aspects, such as fluctuations in capacity and stability, the network tools need to be evaluated also for network paths containing wireless links. In this investigation we have performed experiments over a high-speed downlink UMTS channel. This makes the present paper unique in the sense that it evaluates and analyzes the applicability of available-bandwidth measurement tools over a radio interface in a wide-area mobile communication network. For the experiments, a commercial mobile network has been used. The measurements show that it is feasible to achieve reliable estimates under certain circumstances. However, some cases pose challenges which motivate further studies.

  • 43.
    Husberg, Björn
    Linköping University, Department of Electrical Engineering.
    A Portable DARC Fax Service2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    DARC is a technique for data broadcasting over the FM radio network. Sectra Wireless Technologies AB has developed a handheld DARC receiver known as the Sectra CitySurfer. The CitySurfer is equipped with a high-resolution display along with buttons and a joystick that allows the user to view and navigate through various types of information received over DARC.

    Sectra Wireless Technologies AB has, among other services, also developed a paging system that enables personal message transmission over DARC. The background of this thesis is a wish to be able to send fax documents using the paging system and to be able to view received fax documents in the CitySurfer.

    The presented solution is a central PC-based fax server. The fax server is responsible for receiving standard fax transmissions and converting the fax documents before redirecting them to the right receiver in the DARC network. The topics discussed in this thesis are fax document routing, fax document conversion and fax server system design.

  • 44.
    Nilsson, Anders
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Tell, Eric
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    Liu, Dake
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, The Institute of Technology.
    A Programmable SIMD-based Multi-standard Rake Receiver Architecture2005In: European Signal Processing Conference, EUSIPCO, Antalya, Turkey, 2005Conference paper (Other academic)
    Abstract [en]

    Programmability with its associated flexibility will be increasingly important in future multi-standard radio systems. We are presenting a fully programmable and flexible DSP platform capable of efficiently performing channel estimation and MRC-based channel equalization for several CDMA-based wireless transmission systems in software. Our processor is based on a DSP core with SIMD-computing clusters. We have mapped Rake receiver kernel-functions supporting several 3G standards to this micro-architecture and benchmarking shows that with the proposed instruction set architecture, our architecture can support channel estimation, equalization and decoding of: WCDMA FDD/TDD-modes and HSDPA at clock rate not exceeding 76 MHz during soft handover conditions.

  • 45.
    Björnson, Emil
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    de Carvalho, Elisabeth
    Aalborg University, Denmark.
    Sorensen, Jesper H.
    Aalborg University, Denmark.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    Popovski, Petar
    Aalborg University, Denmark.
    A Random Access Protocol for Pilot Allocation in Crowded Massive MIMO Systems2017In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, no 4, 2220-2234 p.Article in journal (Refereed)
    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.

  • 46.
    Padma Prasad, Boopal
    Linköping University, Department of Electrical Engineering, Electronics System.
    A Reconfigurable FFT Architecture for Variable Length and Multi-Streaming WiMax Wireless OFDM Standards2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper presents a reconfigurable FFT architecture for variable length andmultistreaming WiMax wireless standard. The architecture processes 1 streamof 2048-pt FFT, up to 2 streams of 1024-pt FFT or up to 4 streams of 512-ptFFT. The architecture consists of 11 SDF pipelined stages and radix-2 butterflyis calculated in each stage. The sampling frequency of the system is varied inaccordance with FFT length. The wordlength and buffer length in each stage isconfigurable depending on the FFT length. Latch-free clock gating technique isused to reduce power consumption.The architecture is synthesized for Virtex-6 XCVLX760 FPGA. Experimentalresults show that the architecture achieves the throughput as required by theWiMax standard and the design has additional features compared to the previousapproaches. The design used 1% of the total available FPGA resources andmaximum clock frequency of 313.67 MHz was achieved.

  • 47.
    Boopal, Padma Prasad
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Garrido Gálvez, Mario
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A Reconfigurable FFT Architecture for Variable-Length and Multi-Streaming OFDM Standards2013In: IEEE International Symposium on Circuits and Systems (ISCAS), 2013, IEEE , 2013, 2066-2070 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a reconfigurable FFT architecture for variable-length and multi-streaming WiMax wireless standard. The architecture processes 1 stream of 2048-point FFT, up to 2 streams of 1024-point FFT or up to 4 streams of 512-point FFT. The architecture consists of a modified radix-2 single delay feedback (SDF) FFT. The sampling frequency of the system is varied in accordance with the FFT length. The latch-free clock gating technique is used to reduce power consumption. The proposed architecture has been synthesized for the Virtex-6 XCVLX760 FPGA. Experimental results show that the architecture achieves the throughput that is required by the WiMax standard and the design has additional features compared to the previous approaches. The design uses 1% of the total available FPGA resources and maximum clock frequency of 313.67 MHz is achieved. Furthermore, this architecture can be expanded to suit other wireless standards.

  • 48.
    Zhang, Jingcheng
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    A Remote Monitoring and Control System for Cultural Heritage Buildings Utilizing Wireless Sensor Networks2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation presents the study of a wireless remote monitoring and control system utilized for cultural heritage preservation purpose. The system uses wireless sensor networks to remotely monitor and control the indoor climate, i.e., temperature and relative humidity of the cultural buildings.

    The system mainly consists of three parts, i.e., the wireless sensor network part, the gateway part and the web service part. Wireless sensor networks are deployed in different cultural buildings. The ZigBee protocol is utilized for the wireless sensor network communication. Sensor nodes report the indoor climate periodically. By connecting with radiators and/or dehumidifiers, the wireless control nodes can control the indoor climate according to the remote configuration. A gateway maintains the communication between a wireless sensor network and the web service. In monitoring function, the gateway forwards sensor messages from the wireless sensor network to the web service. In control function, the gateway synchronizes the climate settings from the web service to the wireless sensor network. The gateway also sends control commands to the wireless control nodes in the wireless sensor network. The web service provides a web-based user interface for the system.

    Different from ordinary cable-connected sensor networks, a wireless sensor network that works for cultural heritage preservation should be a system with a large number of sensor nodes covering a large area in a building, high reliability in message transmission, low power consumption and low cost. In this study, the performance of the ZigBee wireless network is improved to meet such requirements base on the investigation of the ZigBee protocol limitation. Firstly, a method for enhancing the wireless sensor network communication reliability is developed. The reactive routing protocol defined by the ZigBee standard is improved so that the wireless nodes automatically detect and repair network communication problems. This method minimizes the message lost within the wireless sensor network by always reserving a route from the source node to the destination node. Secondly, a generic low power working method is developed for sensor devices. This method defines the general sensor module behavior which includes sensor data collecting, sensor message forwardingand wireless network rejoining upon communication failure. It allows sensor devices to maintain high message reliability with low power consumption. Especially, these methods are developed as a complementary infrastructure of the ZigBee wireless sensor network in order to increase the transmission reliability with low power consumption. Finally, methods and algorithms are developed to make it possible to power the ZigBee message relays (i.e., routers) with small batteries. In this system, the whole ZigBee network is synchronized. Wireless communications within the ZigBee network are scheduled so that every wireless transmission is collision-free. During the period when no communication is scheduled, the router can go into low power mode. This design improvement removes the original requirement of using mains power for ZigBee message relays. A truly battery-driven and low power consumption wireless sensor network is developed for monitoring cultural heritage buildings without (or with limited) mains power.

    The remote control function is developed to mainly prevent biological degradation by controlling indoor climate, i.e., temperature and relative humidity. After studying the requirements for heritage preservation, a high flexibility, high reliability and low cost wireless indoor climate control system is developed. Different control algorithms are implemented to achieve different control results.

    Till today, the remote monitoring and control system presented in this dissertation has been installed in 31 cultural heritage buildings both in Sweden and Norway.

    List of papers
    1. Remote Sensing System for Cultural Buildings Utilizing ZigBee Technology
    Open this publication in new window or tab >>Remote Sensing System for Cultural Buildings Utilizing ZigBee Technology
    2010 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    A wireless remote sensing system using the ZigBee standard ispresented in this paper. This system is a wireless solution formonitoring purpose in cultural buildings in order to protectcultural heritage. The concept of this system utilizes ZigBeenetworks to carry and transmit data collected by sensors andstore them into both local and remote databases. Thus, users canmonitor the measured data locally or remotely. Especially, thepower consumption is optimized to extend the lifetime of thebattery-driven devices. Moreover, since the system has amodular architecture, it is easy to add extra services into thissystem.

    Keyword
    Modular system, power consumption, wireless sensor network, ZigBee
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-61295 (URN)
    Conference
    8th. International Conference on Computing, Communications and Control Technologies (CCCT 2010), April 6 - 9, Orlando, FL, USA
    Projects
    CultureBee
    Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2013-12-16Bibliographically approved
    2. Design of the Remote Climate Control System for Cultural Buildings Utilizing ZigBee Technology
    Open this publication in new window or tab >>Design of the Remote Climate Control System for Cultural Buildings Utilizing ZigBee Technology
    2010 (English)In: Sensors & Transducers Journal, ISSN 1726-5479, Vol. 118, no 7, 13-27 p.Article in journal (Refereed) Published
    Abstract [en]

    A wireless solution of remote climate control for cultural buildings is presented in this paper. The system allows users to use web service to control climate in different cultural buildings, like churches. The wireless sensor networks deployed in churches receive the control commands and manage the indoor climate. The whole system is modularly designed, which makes possible an easy service extension, system reconfiguration and modification. This paper includes the system overview and the software design of each part within the system.

    Keyword
    ZigBee, Wireless sensor network, Remote control, Modular system design
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-61293 (URN)
    Projects
    CultureBee
    Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2013-12-16Bibliographically approved
    3. Reliability and Latency Enhancements in a ZigBee Remote Sensing System
    Open this publication in new window or tab >>Reliability and Latency Enhancements in a ZigBee Remote Sensing System
    2010 (English)Conference paper, Published paper (Other academic)
    Abstract [en]

    Methods to improve the reliability and optimize the system latency of our own-developed ZigBee remote sensing system are introduced in this paper. The concept of this system utilizes the ZigBee network to transmit sensor information and process them at both local and remote databases. The enhancement has been done in different parts in this system. In the ZigBee network part, the network topology is configured and controlled. The latency for message transmitting is also optimized. In the data processing part, the network status check function and data buffer function are introduced to improve the system reliability. Additionally, the system latency is measured to compare with the Ad-hoc On Demand Distance Vector algorithm used in the ZigBee standard.

    Keyword
    System reliability, system latency, ZigBee network topology configuration, data buffering
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-61294 (URN)10.1109/SENSORCOMM.2010.38 (DOI)978-1-4244-7538-4 (ISBN)
    Conference
    The Fourth International Conference on Sensor Technologies and Applications (SENSORCOMM 2010), July 18 - 25, Venice/Mestre, Italy
    Projects
    CultureBee
    Available from: 2010-11-10 Created: 2010-11-10 Last updated: 2014-09-25Bibliographically approved
    4. A Fully Wireless Monitoring and Control System for Protecting Cultural Heritage
    Open this publication in new window or tab >>A Fully Wireless Monitoring and Control System for Protecting Cultural Heritage
    2011 (English)In: Proceedings of 2011 20th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises WETICE 2011, IEEE , 2011, 250-255 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper presents a component based wireless monitoring and control system. The system is introduced from both the system architecture and function point of view. The paper begins with the introduction of the component design and the communication interaction between them. The system is composed by three components, the wireless sensor network, the local server and the main server. Wireless sensor networks are deployed in different locations for remote monitoring and control purpose. The monitoring results and control commands are synchronized between the main server and wireless sensor networks via local servers. The test results of the battery life time calculation and remote monitoring field test results are presented in the end of the paper.

    Place, publisher, year, edition, pages
    IEEE, 2011
    Series
    IEEE International Workshop on Enabling Technologies, ISSN 1524-4547
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-71523 (URN)10.1109/WETICE.2011.43 (DOI)978-1-4577-0134-4 (ISBN)
    Conference
    20th IEEE International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WETICE), 27-29 June, Paris, France
    Available from: 2011-10-20 Created: 2011-10-20 Last updated: 2013-12-16Bibliographically approved
    5. A Communication Reliability Enhancement Framework for Wireless Sensor Network Using the ZigBee Protocol
    Open this publication in new window or tab >>A Communication Reliability Enhancement Framework for Wireless Sensor Network Using the ZigBee Protocol
    2012 (English)In: Sensors & Transducers Journal, ISSN 1726-5479, Vol. 135, no 12, 42-56 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the methods for the ZigBee network reliability enhancement and the battery life time optimization. The paper begins with the introduction of the common communication problems due to the broken links between sensor module and message relay, or between different relays. Extra message hand shake mechanisms are added to solve different problem mentioned at the beginning. Finally, a general purpose reliability enhancement component is developed as a state machine which can be work together with ZigBee protocol to enhance ZigBee network communication reliability. Moreover, the battery life time of the sensor module during link broken is considerably increased after the enhancement.

    Keyword
    Communication reliability enhancement, ZigBee, Reusable, Reconfigurable
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-79896 (URN)
    Note

    On the day of the defence date the status of this article was "Manuscript" and the title was "A Communication Reliability Enhancement Framework for the ZigBee WirelessSensor Network".

    Available from: 2012-08-15 Created: 2012-08-15 Last updated: 2013-12-16Bibliographically approved
    6. A Web-based Remote Indoor Climate Control System Based on Wireless Sensor Network
    Open this publication in new window or tab >>A Web-based Remote Indoor Climate Control System Based on Wireless Sensor Network
    Show others...
    2013 (English)In: International Journal of Sensors and Sensor Networks, Vol. 1, no 3, 32-40 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents the design and implementation of a web-based wireless indoor climate control system. The user interface of the system is implemented as a web service. People can login to the website and remotely control the indoor climate of different locations. A wireless sensor network is deployed in each location to execute control commands. A gateway is implemented to synchronize the information between the wireless sensor network and the web service. The gateway software also includes scheduling function and different control algorithms to improve the control result. Additionally, the system security and availability are highly considered in this system. The gateway software implements a warning function which sends warning messages when emergency happens. Finally, the whole wireless control system architecture is modularly designed. It is easy to add different control applications or different control algorithms into the system.

    Place, publisher, year, edition, pages
    Science Publishing Group, 2013
    Keyword
    Remote Control, Indoor Climate, Wireless Sensor Network
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-102588 (URN)10.11648/j.ijssn.20130103.12 (DOI)
    Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2014-01-17Bibliographically approved
    7. Design and Implementation of a Truly Battery-Driven ZigBee Wireless Sensor Network
    Open this publication in new window or tab >>Design and Implementation of a Truly Battery-Driven ZigBee Wireless Sensor Network
    2013 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    As defined by the ZigBee standard, a router should be mains-powered in order to maintain the mesh feature of the ZigBee network. This study presents a method which allows the ZigBee router goes into sleep mode periodically and keeps the same mesh feature during the ZigBee communications. In this study, the standard ZigBee communication is separated into two synchronized clusters. The first cluster includes the communication between end devices and the associated router. The sensor message report time of different end devices are scheduled by the router in different collision-free time slots within a predefined time interval. The second cluster includes the mesh communication between routers and the concentrator. All routers are synchronized so that they wake up at the same time to maintain the mesh feature. In order to maximize the router battery lifetime, algorithms are developed so that the concentrator communicates with routers according to the network routing records. Additionally, in order to recover the broken communication, special logics are implemented in routers and end device so that they can rejoin the wireless sensor network with low power consumption. Finally, a battery lifetime model is presented which can be utilized to calculate battery lifetime of the ZigBee router under different network configurations.

    Keyword
    Low Power, ZigBee Router, Wireless Sensor Network, High Availability
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-102590 (URN)
    Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2013-12-16Bibliographically approved
  • 49.
    Bertilsson, Erik
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Computer Engineering. Linköping University, Faculty of Science & Engineering.
    Larsson, Erik G
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering.
    A Scalable Architecture for Massive MIMO Base Stations Using Distributed Processing2016In: 2016 50TH ASILOMAR CONFERENCE ON SIGNALS, SYSTEMS AND COMPUTERS, Washington: IEEE COMPUTER SOC , 2016, 864-868 p.Conference paper (Refereed)
    Abstract [en]

    Massive MIMO-systems have received considerable attention in recent years as an enabler in future wireless communication systems. As the idea is based on having a large number of antennas at the base station it is important to have both a scalable and distributed realization of such a system to ease deployment. Most work so far have focused on the theoretical aspects although a few demonstrators have been reported. In this work, we propose a base station architecture based on connecting the processing nodes in a K-ary tree, allowing simple scalability. Furthermore, it is shown that most of the processing can be performed locally in each node. Further analysis of the node processing shows that it should be enough that each node contains one or two complex multipliers and a few complex adders/subtracters operating at some hundred MHz. It is also shown that a communication link of some Gbps is required between the nodes, and, hence, it is fully feasible to have one or a few links between the nodes to cope with the communication requirements.

  • 50.
    Bertilsson, Erik
    Linköping University, Department of Electrical Engineering, Computer Engineering.
    A Scalable Architecture for Massive MIMO Base Stations Using Distributed Processing2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Massive MIMO is an emerging technology for future wireless systems that has received much attention from both academia and industry recently. The most prominent feature of Massive MIMO is that the base station is equiped with a large number of antennas. It is therefore important to create scalable architectures to enable simple deployment in different configurations.

    In this thesis, a distributed architecture for performing the baseband processing in a massive OFDM MU-MIMO system is proposed and analyzed. The proposed architecture is based on connecting several identical nodes in a K-ary tree. It is shown that, depending on the chosen algorithms, all or most computations can be performed in a distrbuted manner. Also, the computational load of each node does not depend on the number of nodes in the tree (except for some timing issues) which implies simple scalability of the system.

    It is shown that it should be enough that each node contains one or two complex multipliers and a few complex adders running at a couple of hundres MHz to support specifications similar to LTE. Additionally the nodes must communicate with each other over links with data rates in the order of some Gbps.

    Finally, a VHDL implementation of the system is proposed. The implementation is parameterized such that a system can be generated from a given specification.

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