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  • 1.
    Adjiashvili, David
    et al.
    ETH, Switzerland.
    Bosio, Sandro
    ETH, Switzerland.
    Li, Yuan
    Lund University, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Exact and Approximation Algorithms for Optimal Equipment Selection in Deploying In-Building Distributed Antenna Systems2015Ingår i: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 14, nr 4, s. 702-713Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a combinatorial optimization problemin passive In-Building Distributed Antenna Systems (IB-DAS) deployment for indoor mobile broadband service. These systems have a tree topology, in which a central base station is connected to a number of antennas located at tree leaves via cables represented by the tree edges. Each inner node corresponds to a power equipment, of which the available types differ in the number of output ports and/or by power gain at the ports. This paper focuses on the equipment selection problemthat amounts to, for a given passive DAS tree topology, selecting a power equipment type for each inner node and assigning the outgoing edges of the node to the equipment ports. The performance metric is the power deviation at the antennas from the target values. We consider as objective function the minimization of either the total or the largest power deviation over all antennas. Our contributions are the development of exact pseudo-polynomial time algorithms and (additive) fully-polynomial time approximation schemes for both objectives. Numerical results are provided to illustrate the algorithms. We also extend some results to account for equipment cost.

  • 2.
    Ahani, Ghafour
    et al.
    Komar University of Science and Technology, Iraq.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Ding, Wei
    Ranplan Wireless Network Design Ltd, England.
    On SC-FDMA Resource Allocation with Power Control2016Ingår i: 2016 IEEE 21ST INTERNATIONAL WORKSHOP ON COMPUTER AIDED MODELLING AND DESIGN OF COMMUNICATION LINKS AND NETWORKS (CAMAD), IEEE , 2016, s. 112-116Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, single-carrier frequency division multiple accesses (SC-FDMA) is discussed. In particular, minimum stun power, subject to meeting users demand is considered. There are two channel allocation schemes, localized and interleaved. In localized scheme, a block of convective channels in the spectrum is allocated to each user. In interleaved scheme, channels will be spread out over the spectrum and will be distributed equidistantly. It has been previously assumed that when a block of channels is assigned to a user, the same amount of power will be allocated to each channel. However, the power could be used more efficiently without this assumption We show that the resulting power allocation problem can be solved in linear time and propose an optimal power allocation procedure. Next, the effect of this new power optimization procedure is investigated numerically. In the next part of paper, we prove that for the interleaved scheme, Minimum sum power problem with or without this new power optimization is polynomial solvable. Finally, we numerically compare localized and interleaved SC-FDMA with and without power optimization The results show that the localized scheme with the new power optimization yields the best performance

  • 3.
    Amaldi, E.
    et al.
    University of Milan.
    Bosio, S.
    University of Milan.
    Malucelli, F.
    University of Milan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    On a new class of set covering problems arising in WLAN design2005Ingår i: Proceedings of the International Network Optimization Conference INOC,2005, Lisbon. Portugal: University of Lisbon , 2005, s. 470-Konferensbidrag (Refereegranskat)
  • 4.
    Amaldi, Edoardo
    et al.
    Politecn Milan.
    Bosio, Sandro
    ETH.
    Malucelli, Federico
    Politecn Milan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Solving Nonlinear Covering Problems Arising in WLAN Design2011Ingår i: OPERATIONS RESEARCH, ISSN 0030-364X, Vol. 59, nr 1, s. 173-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wireless local area networks (WLANs) are widely used for cable replacement and wireless Internet access. Because the medium access control (MAC) scheme of WLANs has a strong influence on network performance, it should be accounted for in WLAN design. This paper presents AP location models that optimize a network performance measure specifically for the MAC scheme of WLANs that represents the efficiency in sharing the wireless medium. For these models, we propose a solution framework based on an effective integer-linear programming Dantzig-Wolfe reformulation. This framework is applicable to any nonlinear covering problem where the objective function is a sum of contributions over the groundset elements (users in WLANs). Extensive computational results show that our solution strategy quickly yields optimal or near-optimal solutions for WLAN design instances of realistic size.

  • 5.
    Andersson Granberg, Tobias
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Norin, Anna
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Värbrand, Peter
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Integrating optimization and simulation to gain more efficient airport logistics2009Ingår i: Eighth USA/Europe Air Traffic Management Research and Development Seminar (ATM2009), 2009, s. 1-10Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present airport logistics, which is a framework of resource management in the air transportation system. Focus is on the processes supporting turn-around. A detailed simulation model of various processes involved in turn-around is developed, by which the interaction between these processes are analyzed. We show that integrating optimization and simulation is a powerful tool to demonstrate efficiency improvements in airport logistics, using scheduling de-icing trucks as an example. An optimization algorithm for scheduling de-icing trucks is developed and simulations are performed comparing different schedules. The schedule obtained when considering total airport performance in the optimization algorithm gives minimum flight delay and waiting times in the simulations.

  • 6.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Askoxylakis, Ioannis
    FORTH, Institute of Computer Science, Greece.
    Fowler, Scott
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Gundlegård, David
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Traganitis, Apostolos
    FORTH, Institute of Computer Science, Greece.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Security and Resilience in Cognitive Radio Networks2011Ingår i: European Research Consortium for Informatics and Mathematics Magazine, ISSN 0926-4981, nr 85, s. 48-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    After more than a decade of research, system securityand resilience is now the major technological barrier forthe Cognitive Radio (CR) to be adopted by the telecommunication industry. New ideas are required tomake CR networks secure and robust against attacks taking advantage the inherent characteristics of the CR functionality. This work explores key points that urgentlyneed to be addressed.

  • 7.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Fitzgerald, Emma
    Lund University, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. University of Maryland, MD 20742 USA.
    Allocation of Heterogeneous Resources of an IoT Device to Flexible Services2016Ingår i: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 3, nr 5, s. 691-700Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.

  • 8.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Avgouleas, Ioannis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Flexible allocation of heterogeneous resources to services on an IoT device2015Ingår i: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 99-100Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.

  • 9.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme2011Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, s. 425-428Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.

  • 10.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks2011Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, nr 8, s. 819-821Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Analysis of wireless systems commonly assumes single-user detection at the receivers. Interference is typically treated as noise. On the other hand, multiuser detection has long been taking advantage of interference cancellation (IC) to increase capacity. We exploit IC by optimal rate selection. Transmission rates are collaboratively optimized to maximize the benefit of IC. A link reduces its rate, if that enables IC to significantly boost the SINR on other links. We provide a complexity analysis and an integer programming model to find the optimal IC pattern. Simulation results indicate that throughput improvement is over 30% in low SINR regimes.

  • 11.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    He, Qing
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework2014Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, nr 2, s. 1083-1100Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Ephremides, Anthony
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    He, Qing
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    On Emptying a Wireless Network in Minimum Time2012Ingår i: 2012 IEEE International Symposium on Information Theory Proceedings (ISIT), Piscataway, NJ, USA: IEEE , 2012, s. 2671-2675Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider N transmitter-receiver pairs that share a wireless channel and we address the problem of obtaining a schedule for activating subsets of these links so as to empty the transmitter queues in minimum time. Our aim is to provide theoretical insights for the optimality characterization of the problem, using both a cross-layer model formulation, which takes into account the effect of interference on achievable transmission rates, as well as a collision-based model, which does not incorporate the physical layer realities into the problem. We present the basic linear programming formulation of the problem and establish that the optimal schedule need not consist of more than N subset activation frames. We then prove that the problem is NP-hard for all reasonable continuous rate functions. Finally, we obtain sufficient and/or necessary conditions for optimality in a number of special cases.

  • 13.
    Angelakis, Vangelis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Sajid, Muhammad
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Siddiqui, Imran
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012Ingår i: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), Piscataway, NJ, USA: IEEE , 2012, s. 6525-6529Konferensbidrag (Refereegranskat)
    Abstract [en]

    A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.

  • 14.
    Avgouleas, Ioannis
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Angelakis, Vangelis
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks2017Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 5, s. 7394-7404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

  • 15.
    Bauer, J.
    et al.
    Department of Informatics, University of Bergen, N-5020 Bergen, Norway.
    Haugland, D.
    Department of Informatics, University of Bergen, N-5020 Bergen, Norway.
    Yuan, D.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Analysis and computational study of several integer programming formulations for minimum-energy multicasting in wireless ad hoc networks2008Ingår i: Networks, ISSN 0028-3045, E-ISSN 1097-0037, Vol. 52, nr 2, s. 57-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multicast session in a wireless ad hoc network concerns routing messages from a source to a set of destination devices. Transmitting messages consumes energy at the source and intermediate devices of the session. Since a battery is the only energy source in many applications of wireless ad hoc networks, energy efficiency is an important performance measure of multicasting. In this paper, we present and analyze integer programming models for the problem of minimizing the total energy required by multicasting. We start from a straightforward multicommodity flow model, which is strengthened by a more efficient representation of transmission power. Further strengthening is accomplished by lifting the capacity constraints of the model. We then present cut-based models for the problem, and prove, from a bounding standpoint, the equivalence in strength between these models and their flow-based counterparts. By expanding the underlying graph, we show that the problem can be transformed into finding a minimum Steiner arborescence. The expanded graph arises also in the separation procedure for solving one of the cut-based models. In addition to a theoretical analysis of the relation between various models, we perform extensive computational experiments to study the numerical strengths of these models and their efficiency in solving the problem. © 2008 Wiley Periodicals, Inc.

  • 16.
    Bauer, Joanna
    et al.
    University of Bergen.
    Haugland, Dag
    University of Bergen.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    A fast local search method for minimum energy broadcast in wireless ad hoc networks2009Ingår i: OPERATIONS RESEARCH LETTERS, ISSN 0167-6377, Vol. 37, nr 2, s. 75-79Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Bauer, Joanna
    et al.
    University of Bergen.
    Haugland, Dag
    University of Bergen.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    New results on the time complexity and approximation ratio of the Broadcast Incremental Power algorithm2009Ingår i: INFORMATION PROCESSING LETTERS, ISSN 0020-0190, Vol. 109, nr 12, s. 615-619Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Broadcast Incremental Power (BIP) algorithm is the most frequently cited method for the minimum energy broadcast routing problem. A recent survey concluded that BIP has O(|V|(3)) time complexity, and that its approximation ratio is at least 4.33. We strengthen these results to O(|V|(2)) and 4.598, respectively.

  • 18.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    A Column Generation Method for Spatial TDMA Scheduling in Ad Hoc Networks2004Ingår i: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 2, nr Issue 4, s. 405-418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An ad hoc network can be set up by a number of units without the need of any permanent infrastructure. Two units establish a communication link if the channel quality is sufficiently high. As not all pairs of units can establish direct links, traffic between two units may have to be relayed through other units. This is known as the multi-hop functionality. In military command and control systems, ad hoc networks are also referred to as multi-hop radio networks. Spatial TDMA (STDMA) is a scheme for access control in ad hoc networks. STDMA improves TDMA by allowing simultaneous transmission of multiple units. In this paper, we study the optimization problem of STDMA scheduling, where the objective is to find minimum-length schedules. Previous work for this problem has focused on heuristics, whose performance is difficult to analyze when optimal solutions are not known. We develop novel mathematical programming formulations for this problem, and present a column generation solution method. Our numerical experiments show that the method generates a very tight bound to the optimal schedule length, and thereby enables optimal or near-optimal solutions. The column generation method can be used to provide benchmarks when evaluating STDMA scheduling algorithms. In particular, we use the bound obtained in the column generation method to evaluate a simple greedy algorithm that is suitable for distributed implementations.

  • 19.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    A Dynamic Programming Method for Optimal Scheduling in High Speed Downlink Packet Access2006Ingår i: The 3rd International Conference on Mobile Technologies,Applications and Systems Mobility 2006,2006, 2006Konferensbidrag (Refereegranskat)
  • 20.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    A dynamic programming technique for downlink bandwidth allocation in WCDMA networks2004Ingår i: Vehicle Technology Conference,2004, New York, NY, USA: IEEE , 2004Konferensbidrag (Refereegranskat)
  • 21.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    A Simulated Annealing Algorithm for Frequency Assignment in Frequency Hopping GSM Networks2003Ingår i: International Conference on Computer, Communication and Control Technolgies CCCT 03,2003, Orlando: IIIS , 2003, s. 155-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider the frequency assignment problem in frequency hopping GSM networks, where the task is to construct and assign lists of frequencies to blocks of transceivers, such that the total interference is minimized. We present a mathematical model and describe a simulated annealing algorithm. The algorithm explores the solution space by solving an integer program in each iteration. Computational experiments for real-life and synthesized networks show that considerable interference reduction can be achieved using the algorithm.

  • 22.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Optimized planning of frequency hopping in cellular networks2005Ingår i: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 32, nr 1, s. 169-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a generalization of the classical frequency assignment problem. The generalization arises when frequency hopping is used in a cellular network. The planning problem concerns assigning lists of frequencies to blocks of transceivers, such that the total interference is minimized. This problem is considerably more difficult than the classical frequency assignment problem, because of the large number of possible frequency lists. We provide the technical background that motivates our study, and present a mathematical model which includes the classical frequency assignment problem as a special case. We describe a simulated annealing algorithm. The algorithm explores the solution space by solving an integer program in each iteration. We report computational results for real-life and synthesized networks. © 2003 Elsevier Ltd. All rights reserved.

  • 23.
    Björklund, Patrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Värbrand, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Resource Optimization of Spatial TDMA in Ad Hoc Radio networks : A Column Generation Approach2003Ingår i: IEEE INFOCOM 2003,2003, San Francisco: IEEE , 2003, s. 818-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless communications using ad hoc networks are receiving an increasing interest. The most attractive feature of ad hoc networks is the flexibility. The network is set up by a number of units in an ad hoc manner, without the need of any fixed infrastructure. Communication links are established between two units if the signal strength is sufficiently high. As not all pairs of nodes can establish direct links, the traffic between two units may have to be relayed through other units. This is known as the multihop functionality. Design of ad hoc networks is a challenging task. In this paper we study the problem of resource allocation with spatial TDMA (STDMA) as the access control scheme. Previous work for this problem has mainly focused on heuristics, whose performance is difficult to analyze when optimal solutions are not known. We develop, for both node-oriented and link-oriented allocation strategies, mathematical programming formulations for resource optimization. We further present a column generation approach, which, in our numerical experiments, constantly yields optimal or near-optimal solutions. Our results provide important benchmarks when evaluating heuristic on-line algorithms for resource optimization using STDMA.

  • 24.
    Boonphoka, Terut
    et al.
    Huazhong Univ Sci and Technol, Peoples R China.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhong, Yi
    Huazhong Univ Sci and Technol, Peoples R China.
    Ge, Xiaohu
    Huazhong Univ Sci and Technol, Peoples R China.
    Uthansakul, Peerapong
    Suranaree Univ Technol, Thailand.
    Quek, Tony Q. S.
    Singapore Univ Technol and Design, Singapore.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Performance Analysis of Full-Duplex Relay Channel with Random Access2017Ingår i: 2017 IEEE GLOBECOM WORKSHOPS (GC WKSHPS), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 25.
    Bosio, Sandro
    et al.
    Politecnico di Milano.
    Eisenblätter, Andreas
    Zuse Institute Berlin.
    Geerdes, Hans-Florian
    Zuse Institute Berlin.
    Siomina, Iana
    Ericsson Research.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Mathematical optimization models for WLAN planning2009Ingår i: Graphs and Algorithms in Communication Networks, Berlin: Springer , 2009, 1, s. 454-Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Algorithmic discrete mathematics plays a key role in the development of information and communication technologies, and methods that arise in computer science, mathematics and operations research – in particular in algorithms, computational complexity, distributed computing and optimization – are vital to modern services such as mobile telephony, online banking and VoIP. This book examines communication networking from a mathematical viewpoint. The contributing authors took part in the European COST action 293 – a four-year program of multidisciplinary research on this subject. In this book they offer introductory overviews and state-of-the-art assessments of current and future research in the fields of broadband, optical, wireless and ad hoc networks. Particular topics of interest are design, optimization, robustness and energy consumption. The book will be of interest to graduate students, researchers and practitioners in the areas of networking, theoretical computer science, operations research, distributed computing and mathematics.

  • 26.
    Bosio, Sandro
    et al.
    Otto-von-Guericke Universität.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Modeling and Solving AP Location and Frequency Assignment for Maximizing Access Efficiency in Wi-Fi Networks2009Ingår i: Proceedings of International Network Optimization Conference (INOC), 2009Konferensbidrag (Refereegranskat)
  • 27.
    Capone, Antonio
    et al.
    Politecn Milan.
    Chen, Lei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Gualandi, Stefano
    Politecn Milan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model2011Ingår i: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, ISSN 1536-1276, Vol. 10, nr 5, s. 1368-1372Artikel i tidskrift (Refereegranskat)
    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.

  • 28.
    Capone, Antonio
    et al.
    Politecn Milan.
    Gualandi, Stefano
    Politecn Milan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Joint routing and scheduling optimization in arbitrary ad hoc networks: Comparison of cooperative and hop-by-hop forwarding2011Ingår i: Ad hoc networks, ISSN 1570-8705, E-ISSN 1570-8713, Vol. 9, nr 7, s. 1256-1269Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cooperation schemes form a key aspect of infrastructure-less wireless networks that allow nodes that cannot directly communicate to exchange information through the help of intermediate nodes. The most widely adopted approach is based on hop-by-hop forwarding at the network layer along a path to destination. Cooperative relaying brings cooperation to the physical layer in order to fully exploit wireless resources. The concept exploits channel diversity by using multiple radio units to transmit the same message. The underlying fundamentals of cooperative relaying have been quite well-studied from a transmission efficiency point of view, in particular with a single pair of source and destination. Results of its performance gain in a multi-hop networking context with multiple sources and destinations are, however, less available. In this paper, we provide an optimization approach to assess the performance gain of cooperative relaying vis-a-vis conventional multi-hop forwarding under arbitrary network topology. The approach joint optimizes packet routing and transmission scheduling, and generalizes classical optimization schemes for non-cooperative networks. We provide numerical results demonstrating that the gain of cooperative relaying in networking scenarios is in general rather small and decreases when network connectivity and the number of traffic flows increase, due to interference and resource reuse limitations. In addition to quantifying the performance gain, our approach leads to a new framework for optimizing routing and scheduling in cooperative networks under a generalized Spacial Time Division Multiple Access (STDMA) scheme.

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

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

    Publikationen är tillgänglig i fulltext från 2021-02-08 13:25
  • 30.
    Chen, Bolin
    et al.
    Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.
    Chen, Zheng
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.
    Modeling and Analysis of MPTCP Proxy-based LTE-WLAN Path Aggregation2017Ingår i: 2017 IEEE Global Communications Conference (GLOBECOM), Proceedings Singapore 4 – 8 December 2017, IEEE Communications Society, 2017, s. 1-7Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 31.
    Chen, Bolin
    et al.
    Univ Sheffield, England.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Chen, Zheng
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Univ Sheffield, England.
    Throughput and Delay Analysis of LWA With Bursty Traffic and Randomized Flow Splitting2019Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 7, s. 24667-24678Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the effect of bursty traffic in a long term evolution (LTE) and Wi-Fi aggregation (LWA)-enabled network. The LTE base station routes packets of the same IP flow through the LIE and Wi-Fi links independently. We motivate the use of superposition coding at the LWA-mode Wi-Fi access point (AP) so that it can serve LWA users and Wi-Fi users simultaneously. A random access protocol is applied in such system, which allows the native-mode AP to access the channel with probabilities that depend on the queue size of the LWA-mode AP to avoid impeding the performance of the LWA-enabled network. We analyze the throughput of the native Wi-Fi network and the delay experienced by the LWA users, accounting for the native-mode AP access probability, the traffic flow splitting between LTE and Wi-Fi, and the operating mode of the LWA user with both LIE and Wi-Fi interfaces. Our results show some fundamental tradeoffs in the throughput and delay behavior of LWA-enabled networks, which provide meaningful insight into the operation of such aggregated systems.

  • 32.
    Chen, Bolin
    et al.
    Univ Sheffield, England.
    You, Lei
    Uppsala Univ, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Zhang, Jie
    Univ Sheffield, England.
    Resource Optimization for Joint LWA and LTE-U in Load-Coupled and Multi-Cell Networks2019Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 2, s. 330-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the performance optimization of multi-cell networks with LTE and Wi-Fi aggregation (LWA) and LTE-unlicensed (LTE-U) with sharing of the unlicensed band. Theoretical results are derived to enable an algorithm to approach the optimum. Numerical results show the algorithms effectiveness and benefits of joint use of LWA and LTE-U.

  • 33.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Song, Hui
    Ranplan Wireless Network Design, Ltd, UK.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Zhang, Jie
    University of Sheffield, UK.
    Mathematical Modeling for Optimal Deployment of In-Building Distributed Antenna Systems2012Ingår i: Communications in China (ICCC), 2012, IEEE , 2012, s. 786-791Konferensbidrag (Refereegranskat)
    Abstract [en]

    In-building Distributed Antenna System (IB-DAS) has been proved to be one of the most efficient methods to provide sufficient coverage and capacity for indoor users. The target of a successful IB-DAS deployment is to guarantee the coverage as well as the capacity of the in-building areas with minimum deployment cost. We consider the optimaldeployment of the IB-DAS based on passive DAS in this paper. Mixed Integer Programming model has been developed forthe topology design of IB-DAS through the optimal installation of power splitters in order to connect all the antennas with minimum cable cost, meanwhile, the transmit power at each antenna are kept within the satisfied level for the service guarantee. The model can deliver optimal solutions to systems with a practical size where passive DAS is commonly deployed. To improve the time efficiency, preprocessing has been done to integrate the building layout data into themodeling. Application of the model over realistic IB-DAS deployment has been conducted, which demonstrates the effectiveness of the model.

  • 34.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Achieving higher HSDPA performance and preserving R99 soft handover control by large scale optimization in CPICH coverage planning2009Ingår i: Proceedings of IEEE Wireless Telecommunications Symposium (WTS) 2009, Piscataway, NJ, USA: IEEE , 2009, s. 39-44Konferensbidrag (Refereegranskat)
    Abstract [en]

    Common Pilot Channel (CPICH) power is a crucial parameter in coverage planning of todays UMTS networks that implement both HSDPA and R99 services. Adopting a non-uniform allocation of cell CPICH power and minimizing its amount necessary for coverage, the resulting power saving significantly improves HSDPA performance. At the same time, it is vital to have the desired level R99 soft handover which is heavily influenced by CPICH. In this paper, we demonstrate how large scale optimization can deal with both tasks. Our approach focuses on enhancing cell-edge HSDPA data rate, subject to requirements of CPICH coverage and the level of R99 soft(-er) handover We present a solution algorithm that optimizes CPICH allocation for HSDPA performance, and, in parallel, offers accurate control of R99 soft handover Experimental results for large and realistic network planning scenarios demonstrate the benefit of our optimization approach.

  • 35.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Automated Planning of CPICH Power for enhancing HSDPA Performance at Cell Edges with Preserved Control of R99 Soft Handover2008Ingår i: IEEE International Conference on Communications, 2008. ICC '08., Piscataway, NJ, USA: IEEE , 2008, s. 2936-2940Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present and demonstrate a novel approach for automated planning of common pilot channel (CPICH) power in mobile networks with co-existing HSDPA and R99 services. CPICH power allocation greatly influences the cell coverage pattern. A conventional strategy is to uniformly allocate a constant proportion of the total power to CPICH. We study non-uniform CPICH and optimize its allocation for enhancing HSDPA performance. We focus on HSDPA performance at cell edges, where user throughput is typically very low. Our approach is based on a linear-integer mathematical model; solving the model results in a power allocation that both ensures CPICH coverage and optimizes HSDPA performance at cell edges. Moreover, the model allows for precise control of soft handover (SHO) regions for R99 service. Experimental results show that our approach yields significant enhancement of HSDPA performance at cell edges with preserved R99 SHO control.

  • 36.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Beyond Conventional Fractional Frequency Reuse for Networks with Irregular Cell Layout: An Optimization Approach and Performance Evaluation2010Ingår i: Proceedings of the 5th Annual International Wireless Internet Conference (WICON), IEEE , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fractional frequency reuse (FFR) is one of the key concepts for interference mitigation in OFDMA networks. Previous work on FFR has focused on networks of relatively small size and standard hexagon-shaped cell layout. For real-life networks with very irregular cell layout and high variation in radio propagation, standard reuse schemes (e.g., reuse with a factor three) are inadequate; applying a standard scheme, if possible at all, is far from optimal due to the irregularity. We present an approach based on large-scale optimization to study FFR in networks with irregular cell layout. The approach goes beyond the conventional reuse schemes by optimizing the allocation of the cell-edge sub-band of every cell, taking into account the interference caused by the sub-band allocation of all other cells. What's more, whereas the conventional FFR scheme uses three sub-bands, our optimization process allows for considering the number of subbands as a parameter, and enables the analysis of the impact of this parameter on FFR performance. Performance evaluation for networks with realistic radio propagation conditions shows that the approach enables significant throughput improvement at cell-edge zones, and sometimes it is optimal to split the cell-edge band into more than the standard three sub-bands. These results along with the analysis demonstrate the potential benefits of the proposed approach in practicing FFR for large-scale networks, and illustrate the performance trade-off between the cell-edge and cell-center zones.

  • 37.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover2012Ingår i: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 51, nr 1, s. 53-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coverage planning is an important engineering task in deploying UMTSnetworks implementing both high speed downlink packet access (HSDPA)and Release 99 (R99) services.  Coverage planning amounts todetermining the cell coverage pattern by means of setting the commonpilot channel (CPICH) power of the cells. A conventional strategy isto uniformly allocate a proportion of the total power to CPICH. Inthis paper, we develop mathematical modeling and optimizationapproaches to bring the benefit of power saving enabled by optimizingnon-uniform CPICH to enhance HSDPA performance, while preserving adesired degree of soft handover (SHO) for R99.  The studyfocuses on HSDPA performance at cell edges, where data throughput istypically low.  An integer linear programming model is developed forthe resulting optimization problem.  The model admits optimal ornear-optimal planning solutions for relatively small networks.Solution algorithms based on local search and repeated localsearch are developed.  These algorithms are able to perform theoptimization for large-scale networks time-efficiently.  Experimentalresults for both synthesized networks as well as instances originatingfrom real planning scenarios demonstrate the benefit of ouroptimization approach.

  • 38.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    CPICH Power Planning for Optimizing HSDPA and R99 SHO Performance: Mathematical Modelling and Solution Approach2008Ingår i: 1st IFIP Wireless Days, 2008. WD '08., Piscataway, NJ, USA: IEEE , 2008, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present and demonstrate mathematical modelling and optimization algorithm for enhancing HSDPA performance by automatically linking Common Pilot Channel (CPICH) power to HSDPA transmit power. Our approach uses non-uniformly allocated CPICH power and focuses on HSDPA performance with the side constraint of R99 soft handover. Solving the mathematical model gives the optimal CPICH allocation for small networks. The optimization algorithm demonstrates itself very time efficient in dealing with large scale networks which might have hundreds of cells and tens of thousands of users. A case study of realistic network planning scenario for Berlin shows significant CPICH power saving and HSDPA performance improvement.

  • 39.
    Chen, Lei
    et al.
    Viktoria Swedish ICT, Sweden.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Design of in-building distributed antenna systems: mathematical models and efficient algorithms2015Ingår i: 2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATION WORKSHOP, IEEE , 2015, s. 1497-1502Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 40.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Enhanced Fractional Frequency Reuse for large-scale OFDMA networks with heterogeneous cell layout: Optimization and performance evaluation2010Ingår i: Communication Systems (ICCS), 2010, IEEE , 2010, s. 279-283Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fractional Frequency Reuse (FFR) is one of the key concepts for mitigating inter-cell interference and improving cell-edge performance in OFDMA networks. The standard FFR scheme is intuitive and optimal for the hexagon-shaped cell pattern. In contrast, real-life OFDMA systems have very irregular cell layout, thus the number of surrounding cells and their respective interference vary significantly over the network. For such scenarios, the standard scheme, if applicable at all, is inadequate because the number of sub-bands and the reuse factor are fixed. To overcome the limitations, we present enhanced FFR (EFFR) that allows for high flexibility in the total number of sub-bands as well as the allocation of sub-bands in edge zones. An optimization algorithm is developed to determine sub-band allocation to maximize the cell-edge throughput. Hence EFFR adapts the allocation and reuse pattern to the irregularity of each individual network. Evaluations based on networks with realistic radio propagation conditions show the high performance of EFFR in improving cell-edge throughput. The improvement allows for better trade-off between cell-center and cell-edge throughput. These results along with the analysis demonstrate the benefits of EFFR to performance engineering of OFDMA networks.

  • 41.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Fast Algorithm for Large-scale UMTS Coverage Planning with Soft Handover Consideration2009Ingår i: Proceedings of the 2009 International Conference on Wireless Communications and Mobile Computing: Connecting the World Wirelessly, New York, NY, USA: ACM , 2009, s. 1488-1492Konferensbidrag (Refereegranskat)
    Abstract [en]

    Coverage planning by means of controlling cell Common Pilot Channel (CPICH) power is an important task in deploying UMTS networks. In addition to determining coverage, CPICH power heavily influences the amount of Soft Handover (SHO). Non-uniform cell CPICH power allows for significant power saving and thereby higher capacity for traffic channels. However, optimizing non-uniform CPICH is challenging in terms of computational effort, if the resulting coverage pattern is required to satisfy a desired level of SHO. We present a very fast algorithm for this planning problem. The algorithm has utilized the fact that SHO is strongly correlated with cell overlap. Using overlap as a very good approximation of SHO, the algorithm can compute a near optimal coverage pattern within a few seconds even for large networks. Next, the solution is further polished to deal with SHO accurately. Simulation results show that our solution strategy is able to perform non-uniform CPICH optimization very time-efficiently, making it possible to tackle large scale UMTS coverage planning under SHO consideration.

  • 42.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Generalized Frequency Reuse Schemes for OFDMA Networks: Optimization and Comparison2010Ingår i: IEEE 71st Vehicular Technology Conference (VTC 2010-Spring), 2010, Piscataway, NJ, USA: IEEE , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Frequency reuse is a key concept for interference mitigation and thereby enhancing cell-edge performance in OFDMA networks. Two representative strategies are Fractional Frequency Reuse (FFR) and Soft Frequency Reuse (SFR). Both divide a cell into a center zone and an edge zone, and differentiate their levels of frequency reuse. Previous work on FFR and SFR has focused on networks of relatively small size with standard hexagon-shaped cells. And dividing the cell edge frequency band into three parts has been a common practice so far. However, for real-life networks, this is inadequate because of the irregular cell layout. We consider generalized FFR and SFR schemes, where the number of sub-bands is not restricted to three, and for SFR the power ratio is variable. To find optimal sub- band allocation for the generalized schemes, we present an approach based on large-scale optimization to deal with networks with irregular cell layout. The optimization process allows us to analyze the impact of the number of sub-bands and the SFR power ratio on cell-edge performance, and thereby compare the reuse schemes. We conduct experiments on large networks with realistic radio propagations and present a thorough numerical comparison.

  • 43.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Generalizing and Optimizing Fractional Frequency Reuse in Broadband Cellular Radio Access Networks2012Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 230Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For broadband cellular access based on orthogonal frequency divisionmultiple access (OFDMA), fractional frequency reuse (FFR) is one ofthe key concepts for mitigating inter-cell interference and therebyoptimizing cell-edge performance. In standard FFR, the number of OFDMAsub-bands and the reuse factor are both fixed. Whereas this works wellfor an idealized cell pattern, it is neither directly applicable noradequate for real-life networks with very irregular cell layouts. Inthis paper, we generalize the standard FFR to allow for flexibilities inthe total number of sub-bands as well as the number of sub-bands ineach cell-edge zone, enabling network-adaptive FFR. Two powerassignment strategies that use fixed power per sub-band prior tosub-band allocation and apply cell-specific power derived from thenumber of sub-bands allocated to each cell-edge zone, respectively,are investigated. Optimization algorithms based on local search aredeveloped for sub-band allocation to maximize the cell-edgethroughput. Evaluations using networks with realistic radiopropagation conditions demonstrate the applicability of the generalizedand optimized FFR in performance engineering of OFDMA networks.

  • 44.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Generalizing FFR by Flexible Sub-Band Allocation in OFDMA Networks with Irregular Cell Layout2010Ingår i: IEEE Wireless Communications and Networking Conference Workshops (WCNCW), 2010, IEEE , 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fractional Frequency Reuse (FFR) is one of the key concepts for enhancing cell-edge performance of OFDMA networks. Standard FFR allows one sub-band to be allocated for each cell. This limits the performance improvement of cell edge users, especially those bandwidth-sensitive users. With flexible sub-band allocation, cell edge can be allocated more than one sub-band, thereby performance can be improved largely. Furthermore, previous work on FFR has focused on networks of relatively small size and with standard hexagon- shaped cells.For real-life networks with a very irregular cell layout, these results are inadequate. In this paper, we present the idea of Flexible FFR (FFR-F) which allows more than one sub-band to be allocated to cell edges. Meanwhile, an optimization algorithm based on local search is present for FFR-F planning in large-scale networks with irregular cell layout. Sub-band allocation scheme which maximizes the cell-edge throughput can be found time efficiently. Results from networks with realistic radio propagation conditions show that FFR-F enables significant throughput improvement at cell edges. These results along with the analysis demonstrate the potential benefits of FFR-F and the proposed approach for planning of real-life OFDMA networks.

  • 45.
    Chen, Lei
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Performance Evaluation of Soft Frequency Reuse in Large Networks with  Irregular Cell Pattern: How Much Gain To Expect?2009Ingår i: Proceedings of IEEE PIMRC 2009, 2009Konferensbidrag (Refereegranskat)
  • 46.
    Chen, Lei
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem.
    Solving a minimum-power covering problem with overlap constraint for cellular network design2010Ingår i: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 203, nr 3, s. 714-723Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider a type of covering problem in cellular networks. Given the locations of base stations, the problem amounts to determining cell coverage at minimum cost in terms of the power usage. Overlap between adjacent cells is required in order to support handover. The problem we consider is NP-hard. We present integer linear models and study the strengths of their continuous relaxations. Preprocessing is used to reduce problem size and tighten the models. Moreover, we design a tabu search algorithm for finding near-optimal solutions effectively and time-efficiently. We report computational results for both synthesized instances and networks originating from real planning scenarios. The results show that one of the integer models leads to tight bounds, and the tabu search algorithm generates high-quality solutions for large instances in short computing time.

  • 47.
    Datsika, Eftychia
    et al.
    IQUADRAT Informat SL, Spain.
    Antonopoulos, Angelos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Verikoukis, Christos
    Telecommun Technol Ctr Catalonia CTTC CERCA, Spain.
    Matching Theory for Over-the-Top Service Provision in 5G Networks2018Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, nr 8, s. 5452-5464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 48.
    Ecker, Grit
    et al.
    INFORM GmbH, Germany.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten. Uppsala Univ, Sweden.
    Koster, Arie M. C. A.
    Rhein Westfal TH Aachen, Germany.
    Schmeink, Anke
    Rhein Westfal TH Aachen, Germany.
    Accurate optimization models for interference constrained bandwidth allocation in cellular networks2019Ingår i: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In cellular networks, the signal-to-interference-plus-noise ratio (SINR) is a key metric for link availability and quality. For network planning purposes, a straightforward modeling unfortunately yields numerically difficult optimization models. Further, given a required data rate of a link, its bandwidth consumption depends nonlinearly on the SINR. In this paper, we develop two novel approaches to jointly model SINR-based link availability and bandwidth requirements accurately. The first approach is a set-wise formulation from a users point of view, while the second one exploits discrete channel quality indicators. We compare these formulations with three known approximate approaches numerically, revealing the clear outperformance of our approaches in terms of exactness. Moreover, since the exact models comprise an exponential number of either variables or constraints, we discuss their pros and cons in a further computational study and develop a more efficient algorithm dealing implicitly with the involved constraints. (C) 2018 Elsevier Ltd. All rights reserved.

    Publikationen är tillgänglig i fulltext från 2021-08-22 11:09
  • 49.
    Fountoulakis, Emmanouil
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Pappas, Nikolaos
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Liao, Qi
    Nokia Bell Labs, Germany.
    Suryaprakash, Vinay
    Nokia Bell Labs, Germany.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    An Examination of the Benefits of Scalable TTI for Heterogeneous Traffic Management in 5G Networks2017Ingår i: 2017 15TH INTERNATIONAL SYMPOSIUM ON MODELING AND OPTIMIZATION IN MOBILE, AD HOC, AND WIRELESS NETWORKS (WIOPT), IEEE , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapid growth in the number and variety of connected devices requires 5G wireless systems to cope with a very heterogeneous traffic mix. As a consequence, the use of a fixed transmission time interval (TTI) during transmission is not necessarily the most efficacious method when heterogeneous traffic types need to be simultaneously serviced. This work analyzes the benefits of scheduling based on exploiting scalable TTI, where the channel assignment and the TTI duration are adapted to the deadlines and requirements of different services. We formulate an optimization problem by taking individual service requirements into consideration. We then prove that the optimization problem is NP-hard and provide a heuristic algorithm, which provides an effective solution to the problem. Numerical results show that our proposed algorithm is capable of finding near-optimal solutions to meet the latency requirements of mission critical communication services, while providing a good throughput performance for mobile broadband services.

  • 50.
    Fowler, Scott
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Baravdish, George
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Yuan, Di
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska högskolan.
    Numerical analysis of an industrial power saving mechanism in LTE2014Ingår i: Communications (ICC), 2014 IEEE International Conference on, IEEE conference proceedings, 2014, s. 1748-1753Konferensbidrag (Refereegranskat)
    Abstract [en]

    The 4G standard Long Term Evolution (LTE) utilizes discontinuous reception (DRX) to extend the user equipments battery lifetime. DRX permits an idle UE to power off the radio receiver for two predefined sleep period and then wake up to receive the next paging message. Two major basic power saving models proposed to data are the 3GPP ETSI model and industrial DRX model proposed by Nokia. While previous studies have investigated power saving with the 3GPP ETSI models, the industrial DRX model has not been considered for analytical studies to date. Thus, there is a need to optimize the DRX parameters in the industrial model so as to maximize power saving without incurring network reentry and packet delays. In this paper, we take an overview of various static DRX cycles of the LTE/LTE-Advanced power saving mechanisms by modelling the system with bursty packet data traffic using a semi-Markov process. Using this analytical model, we will show the tradeoff relationship between the power saving and wake-up delay performance in the industrial model.

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