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Chen, Lei
Publications (10 of 20) Show all publications
Chen, L. & Yuan, D. (2013). Mathematical Modeling for Optimal Design of In-Building Distributed Antenna Systems. Computer Networks, 57(17), 3428-3445
Open this publication in new window or tab >>Mathematical Modeling for Optimal Design of In-Building Distributed Antenna Systems
2013 (English)In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 57, no 17, p. 3428-3445Article in journal (Refereed) Published
Abstract [en]

In-building Distributed Antenna System (IB-DAS) has proven to be one of the most promising In-Building Solutions (IBS) to provide coverage and capacity for indoor users. We consider optimal deployment of the passive IB-DAS, focusing on mathematical optimization models based on integer programming, for the topology design and optimal equipment selection of IB-DAS. The models minimize the cable cost and keep the transmit power at each antenna within a pre-defined interval, thus guaranteeing the quality of service. The models can deliver optimal solutions to systems of which the size is of practical relevance. To improve the time efficiency, we develop preprocessing techniques that integrate the building layout data into the system modeling. Application of the models to realistic IB-DAS deployment demonstrates the effectiveness of the models.

Place, publisher, year, edition, pages
Elsevier, 2013
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89716 (URN)10.1016/j.comnet.2013.07.027 (DOI)000328295600012 ()
Available from: 2013-03-04 Created: 2013-03-04 Last updated: 2017-12-06
Yuan, D., Angelakis, V., Chen, L., Karipidis, E. & Larsson, E. G. (2013). On Optimal Link Activation with Interference Cancelation in Wireless Networking. IEEE Transactions on Vehicular Technology, 62(2), 939-945
Open this publication in new window or tab >>On Optimal Link Activation with Interference Cancelation in Wireless Networking
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2013 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 62, no 2, p. 939-945Article in journal (Refereed) Published
Abstract [en]

A fundamental aspect in performance engineering of wireless networks is optimizing the set of links that can be concurrently activated to meet given signal-to-interference-and-noise ratio (SINR) thresholds. The solution of this combinatorial problem is the key element in scheduling and cross-layer resource management. In this paper, we assume multiuser decoding receivers, which can cancel strongly interfering signals. As a result, in contrast to classical spatial reuse, links being close to each other are more likely to be active concurrently. Our focus is to gauge the gain of successive interference cancellation (SIC), as well as the simpler, yet instructive, case of parallel interference cancellation (PIC), in the context of optimal link activation. We show that both problems are NP-hard and develop compact integer linear programming formulations that enable to approach global optimality. We provide an extensive numerical performance evaluation, indicating that for low to medium SINR thresholds the improvement is quite substantial, especially with SIC, whereas for high SINR thresholds the improvement diminishes and both schemes perform equally well.

Keywords
Integer linear programming, interference cancellation, link activation, multiuser decoding, optimization, wireless networks
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-81933 (URN)10.1109/TVT.2012.2222683 (DOI)000318515100045 ()
Available from: 2012-09-25 Created: 2012-09-25 Last updated: 2017-12-07
Chen, L. (2013). Performance Engineering of Mobile Broadband: Capacity Analysis, Cellular Network Optimization, and Design of In-Building Solutions. (Doctoral dissertation). Linköping: Linköping University Electronic Press
Open this publication in new window or tab >>Performance Engineering of Mobile Broadband: Capacity Analysis, Cellular Network Optimization, and Design of In-Building Solutions
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The rapid evolution of mobile communication technologies is making mobile broadband a reality. With over 6 billion cellular connections and the booming of mobile data, mobile broadband leads the technology and service innovation within the domain of information and communication technologies. The thesis deals with performance engineering of mobile broadband. The problems investigated range from fundamental capacity analysis, resource planning and optimization of broadband cellular networks, to design of in-building solutions based on distributed antenna systems. Mathematical modeling and optimization methods have been used to approach the problems.

The first three papers address capacity analysis in wireless communications, where the establishment of any communication link is subject to the Signal to Interference plus Noise Ratio (SINR) threshold. Paper I addresses the maximum link activation problem. The paper introduces a new exact algorithm by reformulating the SINR constraints with equivalent but numerically more effective inequalities, leading to an approach performing significantly better in proving optimality in comparison to the conventional algorithm. Paper II explores the notion of collaborative rate selection for Interference Cancellation (IC) to maximize the transmission rate in wireless networks. The paper analyzes the problem complexity and develops integer programming models for both single stage single-link IC and single stage parallel IC. Paper III studies the performance gain of single-stage and multi-stage IC to optimal link activation. Compact integer programming formulations have been developed and a thorough numerical study is performed.

The next three papers are devoted to planning and optimization of radio resources in cellular mobile broadband networks. Paper IV considers a minimum-power coverage problem with overlap requirements between cell pairs. The paper develops two integer programming models and compares their strength in approaching global optimality. A tabu search algorithm has been developed for large-scale networks. Paper V deals with transmission power planning and optimization in High Speed Downlink Packet Access (HSDPA) networks. A method for enhancing the HSDPA performance by minimizing the power for coverage and reallocating the power to data transmission has been considered. A mathematical model targeting cell-edge HDSPA performance and accounting for soft handover in Universal Mobile Telecommunications System (UMTS) has been developed. In addition, heuristic algorithms based on local search and repeated local search are developed. Paper VI focuses on frequency planning for inter-cell interference mitigation in Orthogonal Frequency Division Multiple Access (OFDMA) networks. The paper generalizes the standard Fractional Frequency Reuse (FFR) concept and addresses its performance for networks with irregular topology. Optimization algorithms using local search have been proposed to find the frequency reuse pattern of generalized FFR for maximizing the edge-user performance. The investigations in Papers IV-VI base the experiments on data sets representing realistic planning scenarios to demonstrate the effectiveness of the proposed approaches.

To face the challenge of in-building mobile broadband service, In-Building Distributed Antennas Systems (IB-DAS) has been proposed. Paper VII tackles the problem of optimal topology design of IB-DAS systems, where a number of in-building distributed antennas are connected to a base station via coaxial cables and power equipments. The paper develops efficient mathematical models for topology design as well as equipment selection, and presents case studies of realistic IB-DAS deployment scenarios.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. p. 40
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1504
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89715 (URN)978-91-7519-675-6 (ISBN)
Public defence
2013-04-09, K3, K°akenhus, Campus Norrköping, Linköpings universitet, Norrköping, 14:15 (English)
Supervisors
Available from: 2013-03-04 Created: 2013-03-04 Last updated: 2013-03-04Bibliographically approved
Chen, L. & Yuan, D. (2012). Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover. Telecommunications Systems, 51(1), 53-64
Open this publication in new window or tab >>Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover
2012 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 51, no 1, p. 53-64Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-62761 (URN)10.1007/s11235-010-9414-z (DOI)000311517300006 ()
Note

funding agencies|CENIIT||Linkoping Institute of Technology, Sweden||Swedish Research Council (Vetenskapsradet)||ELLIIT network||

Available from: 2010-12-03 Created: 2010-12-03 Last updated: 2017-12-12
Chen, L. & Yuan, D. (2012). Generalizing and Optimizing Fractional Frequency Reuse in Broadband Cellular Radio Access Networks. EURASIP Journal on Wireless Communications and Networking, 230
Open this publication in new window or tab >>Generalizing and Optimizing Fractional Frequency Reuse in Broadband Cellular Radio Access Networks
2012 (English)In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 230Article in journal (Refereed) Published
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.

Keywords
orthogonal frequency division multiple access; fractional frequency reuse; optimization; local search.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-62762 (URN)10.1186/1687-1499-2012-230 (DOI)000315038300001 ()
Available from: 2010-12-03 Created: 2010-12-03 Last updated: 2017-12-12Bibliographically approved
Chen, L., Song, H., Yuan, D. & Zhang, J. (2012). Mathematical Modeling for Optimal Deployment of In-Building Distributed Antenna Systems. In: Communications in China (ICCC), 2012: . Paper presented at 1st IEEE International Conference on Communications in China (ICCC 2012), 15-17 August 2012, Beijing, China (pp. 786-791). IEEE
Open this publication in new window or tab >>Mathematical Modeling for Optimal Deployment of In-Building Distributed Antenna Systems
2012 (English)In: Communications in China (ICCC), 2012, IEEE , 2012, p. 786-791Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
IEEE, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-89605 (URN)10.1109/ICCChina.2012.6356992 (DOI)978-1-4673-2814-2 (ISBN)e-978-1-4673-2813-5 (ISBN)
Conference
1st IEEE International Conference on Communications in China (ICCC 2012), 15-17 August 2012, Beijing, China
Available from: 2013-02-27 Created: 2013-02-27 Last updated: 2013-09-16
Angelakis, V., Chen, L. & Yuan, D. (2011). A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme. In: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on: . Paper presented at 19th Annual IEEE/ACM International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems, MASCOTS 2011; Singapore; Singapore (pp. 425-428).
Open this publication in new window or tab >>A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme
2011 (English)In: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, p. 425-428Conference paper, Published paper (Refereed)
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%.

National Category
Telecommunications
Identifiers
urn:nbn:se:liu:diva-75786 (URN)10.1109/MASCOTS.2011.42 (DOI)978-1-4577-0468-0 (ISBN)
Conference
19th Annual IEEE/ACM International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems, MASCOTS 2011; Singapore; Singapore
Available from: 2012-03-11 Created: 2012-03-11 Last updated: 2014-10-17
Capone, A., Chen, L., Gualandi, S. & Yuan, D. (2011). A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model. IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, 10(5), 1368-1372
Open this publication in new window or tab >>A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model
2011 (English)In: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, ISSN 1536-1276, Vol. 10, no 5, p. 1368-1372Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers, 2011
Keywords
Wireless networks, optimization, link activation, SINR, integer programming
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-68909 (URN)10.1109/TWC.2011.030311.100777 (DOI)000290992300005 ()
Note
©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Antonio Capone, Lei Chen, Stefano Gualandi and Di Yuan, A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model, 2011, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, (10), 5, 1368-1372. http://dx.doi.org/10.1109/TWC.2011.030311.100777Available from: 2011-06-10 Created: 2011-06-10 Last updated: 2013-03-04
Angelakis, V., Chen, L. & Yuan, D. (2011). Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks. IEEE Communications Letters, 15(8), 819-821
Open this publication in new window or tab >>Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks
2011 (English)In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 15, no 8, p. 819-821Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2011
Keywords
Interference cancellation, rate selection, optimization, wireless communications
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-70529 (URN)10.1109/LCOMM.2011.062711.110561 (DOI)000294133000012 ()
Available from: 2011-09-12 Created: 2011-09-12 Last updated: 2017-12-08
Chen, L. & Yuan, D. (2010). Beyond Conventional Fractional Frequency Reuse for Networks with Irregular Cell Layout: An Optimization Approach and Performance Evaluation. In: Proceedings of the 5th Annual International Wireless Internet Conference (WICON): . Paper presented at 5th Annual International Wireless Internet Conference (WICON), Mars 1-3, 2010, Singapore. IEEE
Open this publication in new window or tab >>Beyond Conventional Fractional Frequency Reuse for Networks with Irregular Cell Layout: An Optimization Approach and Performance Evaluation
2010 (English)In: Proceedings of the 5th Annual International Wireless Internet Conference (WICON), IEEE , 2010Conference paper, Oral presentation only (Refereed)
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.

Place, publisher, year, edition, pages
IEEE, 2010
National Category
Telecommunications
Identifiers
urn:nbn:se:liu:diva-77310 (URN)10.4108/ICST.WICON2010.8616 (DOI)978-963979986-8 (ISBN)
Conference
5th Annual International Wireless Internet Conference (WICON), Mars 1-3, 2010, Singapore
Available from: 2012-05-11 Created: 2012-05-11 Last updated: 2014-10-02
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