This paper investigates a multiuser MIMO relay downlink system with imperfect channel estimation and limited feedback. Compared with the system using perfect channel state information (CSI), we analyze the achievable rate loss due to CSI mismatch arising from both channel estimation and CSI quantization feedback. An upper bound to the rate loss is firstly derived to characterize the effect of imperfect CSI. Given the rate loss bound, we then present a limited feedback strategy for both two-hop channels in the relay system to guarantee a bounded rate loss for growing SNRs. This newly presented strategy reveals the relationship between CSI quantization level and other system parameters, including the transmit power and the pilots for channel estimation, on the entire two-hop system. Finally, computer simulations are carried out for verifying the correctness of our derived results.
{"title":"Achievable rate analysis and feedback design for multiuser relay with imperfect CSI","authors":"Zhangjie Peng, Wei Xu, Li-Chun Wang, Chunming Zhao","doi":"10.1109/TWC.2013.120313.130355","DOIUrl":"https://doi.org/10.1109/TWC.2013.120313.130355","url":null,"abstract":"This paper investigates a multiuser MIMO relay downlink system with imperfect channel estimation and limited feedback. Compared with the system using perfect channel state information (CSI), we analyze the achievable rate loss due to CSI mismatch arising from both channel estimation and CSI quantization feedback. An upper bound to the rate loss is firstly derived to characterize the effect of imperfect CSI. Given the rate loss bound, we then present a limited feedback strategy for both two-hop channels in the relay system to guarantee a bounded rate loss for growing SNRs. This newly presented strategy reveals the relationship between CSI quantization level and other system parameters, including the transmit power and the pilots for channel estimation, on the entire two-hop system. Finally, computer simulations are carried out for verifying the correctness of our derived results.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131503851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-06-10DOI: 10.1109/TCOMM.2013.053013.130031
Jinho Choi, J. Ha, Hyoungsuk Jeon
Energy delay tradeoff (EDT) is a fundamental tradeoff that can play a crucial role in understanding the energy efficiency of various transmission schemes. For hybrid automatic repeat request (HARQ) protocols, EDT can be well defined. In this paper, in order to understand the EDT for wireless multiuser systems, we consider downlink channels where the HARQ with incremental redundancy (HARQ-IR) protocol is employed for reliable transmissions to users. For a given total power, the power allocation is studied and its impact on EDT is investigated. It is shown that the multiuser diversity (MD)-based power allocation becomes preferable when a long effective delay is allowed.
{"title":"On the energy delay tradeoff of HARQ-IR in wireless multiuser systems","authors":"Jinho Choi, J. Ha, Hyoungsuk Jeon","doi":"10.1109/TCOMM.2013.053013.130031","DOIUrl":"https://doi.org/10.1109/TCOMM.2013.053013.130031","url":null,"abstract":"Energy delay tradeoff (EDT) is a fundamental tradeoff that can play a crucial role in understanding the energy efficiency of various transmission schemes. For hybrid automatic repeat request (HARQ) protocols, EDT can be well defined. In this paper, in order to understand the EDT for wireless multiuser systems, we consider downlink channels where the HARQ with incremental redundancy (HARQ-IR) protocol is employed for reliable transmissions to users. For a given total power, the power allocation is studied and its impact on EDT is investigated. It is shown that the multiuser diversity (MD)-based power allocation becomes preferable when a long effective delay is allowed.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126826834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6363663
Weiliang Zeng, Chengshan Xiao, Jianhua Lu
This paper investigates the interference-aware linear precoder design with finite-alphabet inputs. It maximizes the mutual information between the transmitter and intended receiver while controlling the interference power caused to unintended receivers. For this nonconcave problem, this work proposes a global optimization approach, which is based on two key observations: 1) the interference-aware precoding problem can be reformulated to the problem minimizing a function with bilinear terms over the intersection of multiple co-centered ellipsoids; 2) these bilinear terms can be relaxed by their convex and concave envelopes. In this way, the global optimal solution is obtained by solving a sequence of relaxed problems over shrinking feasible regions. The proposed algorithm calculates the optimal precoder and the theoretical limit of the transmission rate with interference constraints. Thus, it offers an important benchmark for performance evaluation of interference constrained networks.
{"title":"On interference-aware precoding for multi-antenna channels with finite-alphabet inputs","authors":"Weiliang Zeng, Chengshan Xiao, Jianhua Lu","doi":"10.1109/ICC.2012.6363663","DOIUrl":"https://doi.org/10.1109/ICC.2012.6363663","url":null,"abstract":"This paper investigates the interference-aware linear precoder design with finite-alphabet inputs. It maximizes the mutual information between the transmitter and intended receiver while controlling the interference power caused to unintended receivers. For this nonconcave problem, this work proposes a global optimization approach, which is based on two key observations: 1) the interference-aware precoding problem can be reformulated to the problem minimizing a function with bilinear terms over the intersection of multiple co-centered ellipsoids; 2) these bilinear terms can be relaxed by their convex and concave envelopes. In this way, the global optimal solution is obtained by solving a sequence of relaxed problems over shrinking feasible regions. The proposed algorithm calculates the optimal precoder and the theoretical limit of the transmission rate with interference constraints. Thus, it offers an important benchmark for performance evaluation of interference constrained networks.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125136559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364918
Hong Li, G. Koudouridis, G. Hedby, Tao Wu
The effect of relaying in terms of energy efficiency is an important and interesting issue in cellular communications. In this paper, two relaying schemes for uplink are analyzed and compared in the context of cellular systems: Simple relaying (SR), where a user is served either by a relay node or the base station, and Cooperative Relaying (CR), where a user is served by the relay node, the base station or both in a cooperative manner. For the relaying a specific relay network topology is proposed where the relay nodes are deployed at the edge of each cell. The two schemes are analyzed in terms of cell capacity, provided through bit error analysis, and energy efficiency, and are compared to a baseline scheme that is based on a macro network topology with no relays. Based on the proposed relay network topology and the Decode-and-Forward relaying mechanism, this study focuses on finding out the optimal access path between a user and its serving base station. The optimization is performed according to a utility function which targets to maximizing cell capacity and energy efficiency. By choosing the optimal access path while decreasing the energy consumption per user, both cell capacity and energy efficiency of the wireless network are improved. By means of numerical simulations, it is shown that the relay schemes fully outperform the baseline wireless network without relays in both cell capacity and energy efficiency. In all simulation scenarios the CR scheme is the best performing scheme showing a gain around 33% in terms of cell capacity and a gain around 190% in terms of energy efficiency on average over the baseline. Further improvements are expected by utilizing more efficient cooperative relay schemes which will be exploited in the future work.
{"title":"Cooperative relay design for energy efficient cell capacity improvements","authors":"Hong Li, G. Koudouridis, G. Hedby, Tao Wu","doi":"10.1109/ICC.2012.6364918","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364918","url":null,"abstract":"The effect of relaying in terms of energy efficiency is an important and interesting issue in cellular communications. In this paper, two relaying schemes for uplink are analyzed and compared in the context of cellular systems: Simple relaying (SR), where a user is served either by a relay node or the base station, and Cooperative Relaying (CR), where a user is served by the relay node, the base station or both in a cooperative manner. For the relaying a specific relay network topology is proposed where the relay nodes are deployed at the edge of each cell. The two schemes are analyzed in terms of cell capacity, provided through bit error analysis, and energy efficiency, and are compared to a baseline scheme that is based on a macro network topology with no relays. Based on the proposed relay network topology and the Decode-and-Forward relaying mechanism, this study focuses on finding out the optimal access path between a user and its serving base station. The optimization is performed according to a utility function which targets to maximizing cell capacity and energy efficiency. By choosing the optimal access path while decreasing the energy consumption per user, both cell capacity and energy efficiency of the wireless network are improved. By means of numerical simulations, it is shown that the relay schemes fully outperform the baseline wireless network without relays in both cell capacity and energy efficiency. In all simulation scenarios the CR scheme is the best performing scheme showing a gain around 33% in terms of cell capacity and a gain around 190% in terms of energy efficiency on average over the baseline. Further improvements are expected by utilizing more efficient cooperative relay schemes which will be exploited in the future work.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125383340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364371
K. Oikonomou, Giorgos Tsioutsiouliklis, S. Aïssa
Wireless network nodes, recently powerful enough to assume sophisticated roles, have changed the angle of studying service communication costs in modern, typically large-scale and inherently dynamic, network environments. Communication cost minimization for using a certain service, is one of the challenging issues in these environments. Its ensuing optimization problem is not only difficult (NP-hard and requires global information), but also its centralized solution is non-scalable. The approach followed in this paper is a distributed one based on local information. First, a facility replication method ensuring overall communication cost reduction is proposed and analyzed. No additional overhead is introduced and the cost of hosting a new facility is also taken into account. Second, and aiming at reducing the communication cost for using a service, a policy that employs facility replication in conjunction with facility migration, is introduced. This policy is easy to implement since it relies on information locally available at the facility node, and its efficiency and limitations are also analyzed and discussed here. Simulation results are presented, supporting the analytical findings and demonstrating a significant overall cost reduction when the proposed policy is implemented.
{"title":"Scalable facility placement for communication cost reduction in wireless networks","authors":"K. Oikonomou, Giorgos Tsioutsiouliklis, S. Aïssa","doi":"10.1109/ICC.2012.6364371","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364371","url":null,"abstract":"Wireless network nodes, recently powerful enough to assume sophisticated roles, have changed the angle of studying service communication costs in modern, typically large-scale and inherently dynamic, network environments. Communication cost minimization for using a certain service, is one of the challenging issues in these environments. Its ensuing optimization problem is not only difficult (NP-hard and requires global information), but also its centralized solution is non-scalable. The approach followed in this paper is a distributed one based on local information. First, a facility replication method ensuring overall communication cost reduction is proposed and analyzed. No additional overhead is introduced and the cost of hosting a new facility is also taken into account. Second, and aiming at reducing the communication cost for using a service, a policy that employs facility replication in conjunction with facility migration, is introduced. This policy is easy to implement since it relies on information locally available at the facility node, and its efficiency and limitations are also analyzed and discussed here. Simulation results are presented, supporting the analytical findings and demonstrating a significant overall cost reduction when the proposed policy is implemented.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129240660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364535
Mingxin Zhou, Leiming Zhang, Lingyang Song, M. Debbah, B. Jiao
Interference alignment (IA) has been well recognized as an efficient approach to reduce interference at high signal to noise ratio (SNR). However, it demands global channel state information (CSI) at both transmitters and receivers for preceder design in order to maximize the multiplexing gain. In this paper, we discuss IA with delayed differential CSI feedback for time-correlated multiple input multiple output (MIMO) block fading channels. We consider the impact of distortion caused by channel estimation errors and quantized CSI feedback delay, and thus, find an optimal feedback interval to minimize this distortion, as well as the sum rate performance. Specifically, we derive the minimum differential feedback rate. And with the feedback-channel capacity constraint, we further study the relationship between the average sum rate and the feedback interval. Analytical results are verified by simulations.
{"title":"Interference alignment with delayed differential feedback for time-correlated MIMO channels","authors":"Mingxin Zhou, Leiming Zhang, Lingyang Song, M. Debbah, B. Jiao","doi":"10.1109/ICC.2012.6364535","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364535","url":null,"abstract":"Interference alignment (IA) has been well recognized as an efficient approach to reduce interference at high signal to noise ratio (SNR). However, it demands global channel state information (CSI) at both transmitters and receivers for preceder design in order to maximize the multiplexing gain. In this paper, we discuss IA with delayed differential CSI feedback for time-correlated multiple input multiple output (MIMO) block fading channels. We consider the impact of distortion caused by channel estimation errors and quantized CSI feedback delay, and thus, find an optimal feedback interval to minimize this distortion, as well as the sum rate performance. Specifically, we derive the minimum differential feedback rate. And with the feedback-channel capacity constraint, we further study the relationship between the average sum rate and the feedback interval. Analytical results are verified by simulations.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114865917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364673
Daniel Turull, M. Hidell, Peter Sjödin
Network virtualization has been an important research topic for many years but still suffers from the lack of an abstraction level like the one present in virtualization of computing and storage. Our work in progress presented here proposes an architecture for such a network virtualization abstraction. It is deployed as a library, similar to libvirt in computer virtualization, with a unified interface towards the underlying network specific drivers. The architecture will allow management tools to be independent of the underlying technologies. In addition, it will enable programmatic and on-demand creation of virtual networks. A common set of calls is defined to instantiate different virtual networks, using a single node view to provide the user with a suitable abstraction of the network. We describe a prototype of our proposed architecture on top of an OpenFlow-enabled network. We demonstrate its feasibility for creating isolated virtual networks in a programmatic and on demand fashion.
{"title":"libNetVirt: The network virtualization library","authors":"Daniel Turull, M. Hidell, Peter Sjödin","doi":"10.1109/ICC.2012.6364673","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364673","url":null,"abstract":"Network virtualization has been an important research topic for many years but still suffers from the lack of an abstraction level like the one present in virtualization of computing and storage. Our work in progress presented here proposes an architecture for such a network virtualization abstraction. It is deployed as a library, similar to libvirt in computer virtualization, with a unified interface towards the underlying network specific drivers. The architecture will allow management tools to be independent of the underlying technologies. In addition, it will enable programmatic and on-demand creation of virtual networks. A common set of calls is defined to instantiate different virtual networks, using a single node view to provide the user with a suitable abstraction of the network. We describe a prototype of our proposed architecture on top of an OpenFlow-enabled network. We demonstrate its feasibility for creating isolated virtual networks in a programmatic and on demand fashion.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123222954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6363981
I. Qazi, T. Znati, D. Mossé
Many promising congestion control protocols use explicit feedback from the network to achieve high performance. These protocols often use congestion signals whose computation requires an estimate of link capacity. Such estimates are not available in networks where capacity varies over time. This paper studies the impact of inaccurate capacity estimates on the performance of congestion control protocols over variable capacity links. As a case study, we focus on 802.11 WLANs. We show that such estimates can lead to either under-utilization or unfairness and network overload. Using a model, we characterize the available capacity of a node in a 802.11 WLAN and then study a method for capacity estimation. Using simulations, we show that the method leads to high utilization and fairness over shared, multi-access networks.
{"title":"Improving performance of router-assisted transport protocols over variable capacity links","authors":"I. Qazi, T. Znati, D. Mossé","doi":"10.1109/ICC.2012.6363981","DOIUrl":"https://doi.org/10.1109/ICC.2012.6363981","url":null,"abstract":"Many promising congestion control protocols use explicit feedback from the network to achieve high performance. These protocols often use congestion signals whose computation requires an estimate of link capacity. Such estimates are not available in networks where capacity varies over time. This paper studies the impact of inaccurate capacity estimates on the performance of congestion control protocols over variable capacity links. As a case study, we focus on 802.11 WLANs. We show that such estimates can lead to either under-utilization or unfairness and network overload. Using a model, we characterize the available capacity of a node in a 802.11 WLAN and then study a method for capacity estimation. Using simulations, we show that the method leads to high utilization and fairness over shared, multi-access networks.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114955143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364037
Junghun Ryu, E. Noel, K. Tang
In this paper, we explore the use of a pseudo-random graph family, Borel Cayley graph family, as the network topology in an NGN (Next Generation Network) with thousands of nodes operated in a packet switching environment asynchronously. BCGs are known to be an efficient topology in interconnection networks because of its small diameters, short average path lengths, and low-degree connections. However, the application of BCGs in NGN are hindered by a lack of size flexibility and fault tolerant routing. We propose a fault-tolerant routing algorithm for BCGs. Our algorithm exploits the vertex-transitivity property of Borel Cayley graphs and relies on extra information to reflect topology change. Our results show that the proposed method supports good reachability and short average hop count.
{"title":"Fault-tolerant routing on Borel Cayley graph","authors":"Junghun Ryu, E. Noel, K. Tang","doi":"10.1109/ICC.2012.6364037","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364037","url":null,"abstract":"In this paper, we explore the use of a pseudo-random graph family, Borel Cayley graph family, as the network topology in an NGN (Next Generation Network) with thousands of nodes operated in a packet switching environment asynchronously. BCGs are known to be an efficient topology in interconnection networks because of its small diameters, short average path lengths, and low-degree connections. However, the application of BCGs in NGN are hindered by a lack of size flexibility and fault tolerant routing. We propose a fault-tolerant routing algorithm for BCGs. Our algorithm exploits the vertex-transitivity property of Borel Cayley graphs and relies on extra information to reflect topology change. Our results show that the proposed method supports good reachability and short average hop count.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132232549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-29DOI: 10.1109/ICC.2012.6364454
R. Vahidnia, S. Shahbazpanahi
We consider an asynchronous two-way relay network where the signal paths, going through different relays, are subject to different propagation and/or processing delays. Such a relay channel can be viewed as an artificial multi-path channel which causes inter-symbol-interference (ISI). To combat such an ISI, orthogonal frequency division multiplexing (OFDM) is deployed at the two transceivers while the relays are to use simple amplify-and-forward (AF) relaying protocol, thereby realizing a beamformer in a distributed manner. For such a communication scheme, we present two max-min design approaches to obtain jointly optimal subcarrier power loading at the transceivers and distributed beamforming weights at the relays. Numerical examples are presented to compare the performance of the two algorithms.
{"title":"Distributed beamforming and subcarrier power allocation for OFDM-based asynchronous two-way relay networks","authors":"R. Vahidnia, S. Shahbazpanahi","doi":"10.1109/ICC.2012.6364454","DOIUrl":"https://doi.org/10.1109/ICC.2012.6364454","url":null,"abstract":"We consider an asynchronous two-way relay network where the signal paths, going through different relays, are subject to different propagation and/or processing delays. Such a relay channel can be viewed as an artificial multi-path channel which causes inter-symbol-interference (ISI). To combat such an ISI, orthogonal frequency division multiplexing (OFDM) is deployed at the two transceivers while the relays are to use simple amplify-and-forward (AF) relaying protocol, thereby realizing a beamformer in a distributed manner. For such a communication scheme, we present two max-min design approaches to obtain jointly optimal subcarrier power loading at the transceivers and distributed beamforming weights at the relays. Numerical examples are presented to compare the performance of the two algorithms.","PeriodicalId":331080,"journal":{"name":"2012 IEEE International Conference on Communications (ICC)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114073155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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