We propose three iterative superimposed-pilot based channel estimators for Orthogonal Frequency Division Multiplexing (OFDM) systems. Two are approximate maximum-likelihood, derived by using a Taylor expansion of the conditional probability density function of the received signal or by approximating the OFDM time signal as Gaussian, and one is minimum-mean square error. The complexity per iteration of these estimators is given by approximately O(NL^2), O(N^3) and O(NL), where N is the number of OFDM subcarriers and L is the channel length (time). Two direct (non-iterative) data detectors are also derived by averaging the log likelihood function over the channel statistics. These detectors require minimising the cost metric in an integer space, and we suggest the use of the sphere decoder for them. The Cramer–Rao bound for superimposed pilot based channel estimation is derived, and this bound is achieved by the proposed estimators. The optimal pilot placement is shown to be the equally spaced distribution of pilots. The bit error rate of the proposed estimators is simulated for N = 32 OFDM system. Our estimators perform fairly close to a separated training scheme, but without any loss of spectral efficiency.
{"title":"OFDM channel estimation and data detection with superimposed pilots","authors":"T. Cui, C. Tellambura","doi":"10.1002/ett.1461","DOIUrl":"https://doi.org/10.1002/ett.1461","url":null,"abstract":"We propose three iterative superimposed-pilot based channel estimators for Orthogonal Frequency Division Multiplexing (OFDM) systems. Two are approximate maximum-likelihood, derived by using a Taylor expansion of the conditional probability density function of the received signal or by approximating the OFDM time signal as Gaussian, and one is minimum-mean square error. The complexity per iteration of these estimators is given by approximately O(NL^2), O(N^3) and O(NL), where N is the number of OFDM subcarriers and L is the channel length (time). Two direct (non-iterative) data detectors are also derived by averaging the log likelihood function over the channel statistics. These detectors require minimising the cost metric in an integer space, and we suggest the use of the sphere decoder for them. The Cramer–Rao bound for superimposed pilot based channel estimation is derived, and this bound is achieved by the proposed estimators. The optimal pilot placement is shown to be the equally spaced distribution of pilots. The bit error rate of the proposed estimators is simulated for N = 32 OFDM system. Our estimators perform fairly close to a separated training scheme, but without any loss of spectral efficiency.","PeriodicalId":50473,"journal":{"name":"European Transactions on Telecommunications","volume":"14 1","pages":"125-136"},"PeriodicalIF":0.0,"publicationDate":"2011-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85379453","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}
This European Transactions on Communication is a special issue devoted to the European Wireless 2009 Conference. The technical contributions, originally selected for their quality and significance, where extended and reviewed before being included in this journal. Cooperation in wireless networks, a highly explored research area in recent years, is here present basically in all included papers. Research communities from academia and industry have spent countless efforts in investigating and developing cooperative networking concepts, due to the high potential of such technology. Indeed, benefits include significant performance improvements at link, network and system level. Moreover, efficiency in resource utilisation can also be enhanced by these techniques. Quite often, cooperation and cognition are used together, as in the cases of cognitive radio and networking. The application area of cooperation and cognition is wide, and in this issue the focus is mostly on exploiting these principles in the lower layers of the OSI stack, particularly PHY and MAC layers. The included papers cover a variety of important and highly relevant research issues, including cognitive radio, relaying techniques, network coding, dynamic resource allocation techniques, and in general, cooperative techniques applied to multicarrier systems. The first paper on this issue discusses methodological aspects of spectrum occupancy evaluation in cognitive radios. Dynamic spectrum allocation for cellular networks is considered in the second paper. An approach is proposed to derive the optimal allocation policies in terms of operator reward following optimal, heuristic and Qlearning methodologies. The third paper on this issue studies soft frequency reuse and dynamic subcarrier assignments in cellular OFDMA networks. The performance of the soft frequency reuse technique is investigated as a function of the power profiles of the frequency reuse patterns. The fourth paper proposes the use of cooperative feedback in multiuser diversity systems to improve both capacity and error rate. The considered approach efficiently avoids resource allocation errors, resulting in improved link and network performance. The fifth paper investigates the use of network coding in wireless cooperative local clusters for filesharing applications. The sixth paper shows for the very first time a practical implementation of network coding on commercial mobile phones together with practical measurements on supported data rate and energy consumption. The seventh paper on this special issue deals with persistent resource allocations for VoIP traffic in packetswitching mobile cellular networks. This paper studies the problem of efficient transmission of VoIP in a packetswitched network with dominant data traffic. An opensource system level simulation platform for IMTAdvanced systems is presented on the eighth paper. The platform allows studying dynamic protocol behaviour in multicellular mobile radio network
{"title":"Special Issue on European Wireless 2009 Conference","authors":"F. Fitzek, M. Katz","doi":"10.1002/ett.1457","DOIUrl":"https://doi.org/10.1002/ett.1457","url":null,"abstract":"This European Transactions on Communication is a special issue devoted to the European Wireless 2009 Conference. The technical contributions, originally selected for their quality and significance, where extended and reviewed before being included in this journal. Cooperation in wireless networks, a highly explored research area in recent years, is here present basically in all included papers. Research communities from academia and industry have spent countless efforts in investigating and developing cooperative networking concepts, due to the high potential of such technology. Indeed, benefits include significant performance improvements at link, network and system level. Moreover, efficiency in resource utilisation can also be enhanced by these techniques. Quite often, cooperation and cognition are used together, as in the cases of cognitive radio and networking. The application area of cooperation and cognition is wide, and in this issue the focus is mostly on exploiting these principles in the lower layers of the OSI stack, particularly PHY and MAC layers. The included papers cover a variety of important and highly relevant research issues, including cognitive radio, relaying techniques, network coding, dynamic resource allocation techniques, and in general, cooperative techniques applied to multicarrier systems. The first paper on this issue discusses methodological aspects of spectrum occupancy evaluation in cognitive radios. Dynamic spectrum allocation for cellular networks is considered in the second paper. An approach is proposed to derive the optimal allocation policies in terms of operator reward following optimal, heuristic and Qlearning methodologies. The third paper on this issue studies soft frequency reuse and dynamic subcarrier assignments in cellular OFDMA networks. The performance of the soft frequency reuse technique is investigated as a function of the power profiles of the frequency reuse patterns. The fourth paper proposes the use of cooperative feedback in multiuser diversity systems to improve both capacity and error rate. The considered approach efficiently avoids resource allocation errors, resulting in improved link and network performance. The fifth paper investigates the use of network coding in wireless cooperative local clusters for filesharing applications. The sixth paper shows for the very first time a practical implementation of network coding on commercial mobile phones together with practical measurements on supported data rate and energy consumption. The seventh paper on this special issue deals with persistent resource allocations for VoIP traffic in packetswitching mobile cellular networks. This paper studies the problem of efficient transmission of VoIP in a packetswitched network with dominant data traffic. An opensource system level simulation platform for IMTAdvanced systems is presented on the eighth paper. The platform allows studying dynamic protocol behaviour in multicellular mobile radio network ","PeriodicalId":50473,"journal":{"name":"European Transactions on Telecommunications","volume":"126 3 1","pages":"679"},"PeriodicalIF":0.0,"publicationDate":"2010-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83994050","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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