Pub Date : 2011-06-26DOI: 10.1109/SPAWC.2011.5990449
Daniel Romero, Roberto López-Valcarce
Detection of unknown signals with constant modulus (CM) using multiple antennas in additive white Gaussian noise of unknown variance is considered. The channels from the source to each antenna are assumed frequency-flat and unknown. This problem is of interest for spectrum sensing in cognitive radio systems in which primary signals are known to have the CM property. Examples include analog frequency modulated signals such as those transmitted by wireless microphones in the TV bands and Gaussian Minimum Shift Keying modulated signals as in the GSM cellular standard. The proposed detector, derived from a Generalized Likelihood Ratio (GLR) approach, exploits both the CM property and the spatial independence of noise, outperforming the GLR test for Gaussian signals as shown by simulation.
{"title":"Multiantenna detection of constant-envelope signals in noise of unknown variance","authors":"Daniel Romero, Roberto López-Valcarce","doi":"10.1109/SPAWC.2011.5990449","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990449","url":null,"abstract":"Detection of unknown signals with constant modulus (CM) using multiple antennas in additive white Gaussian noise of unknown variance is considered. The channels from the source to each antenna are assumed frequency-flat and unknown. This problem is of interest for spectrum sensing in cognitive radio systems in which primary signals are known to have the CM property. Examples include analog frequency modulated signals such as those transmitted by wireless microphones in the TV bands and Gaussian Minimum Shift Keying modulated signals as in the GSM cellular standard. The proposed detector, derived from a Generalized Likelihood Ratio (GLR) approach, exploits both the CM property and the spatial independence of noise, outperforming the GLR test for Gaussian signals as shown by simulation.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127274251","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990443
Ankit Bhamri, F. Kaltenberger, R. Knopp, J. Hamalainen
The work described in this paper proposes two Smart Hybrid-Automatic Repeat Request (SHARQ) schemes with incremental redundancy, that are developed for a dual-hop network of two relays implementing cooperative communication. In a dual-hop network consisting of multiple relays, one of the most challenging tasks is to determine an appropriate trade-off point between the end-to-end block-error rate (BLER) and an additional delay caused due to HARQ retransmissions in two hops. The retransmissions can either be initiated at the relay nodes or at the source node. HARQ protocol for such a network, should therefore be capable of dynamically deciding the node-of-retransmission. The SHARQ schemes proposed here are designed intelligent in a way that they take into account the presence of two relays and the benefit of using cooperative schemes. Basically the system developed here, intends to provide the combined benefits of diversity gain from cooperative schemes and the throughput improvement from SHARQ in a best possible way. This paper explicitly compares the most basic case of single relay system without HARQ and cooperation with the most advanced scenarios of cooperative communication with SHARQ schemes. It is observed that the latter of the two above scenarios results in throughput improvement of almost 4dB in terms of SNR.
{"title":"Smart Hybrid-ARQ (SHARQ) for cooperative communication via distributed relays in LTE-advanced","authors":"Ankit Bhamri, F. Kaltenberger, R. Knopp, J. Hamalainen","doi":"10.1109/SPAWC.2011.5990443","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990443","url":null,"abstract":"The work described in this paper proposes two Smart Hybrid-Automatic Repeat Request (SHARQ) schemes with incremental redundancy, that are developed for a dual-hop network of two relays implementing cooperative communication. In a dual-hop network consisting of multiple relays, one of the most challenging tasks is to determine an appropriate trade-off point between the end-to-end block-error rate (BLER) and an additional delay caused due to HARQ retransmissions in two hops. The retransmissions can either be initiated at the relay nodes or at the source node. HARQ protocol for such a network, should therefore be capable of dynamically deciding the node-of-retransmission. The SHARQ schemes proposed here are designed intelligent in a way that they take into account the presence of two relays and the benefit of using cooperative schemes. Basically the system developed here, intends to provide the combined benefits of diversity gain from cooperative schemes and the throughput improvement from SHARQ in a best possible way. This paper explicitly compares the most basic case of single relay system without HARQ and cooperation with the most advanced scenarios of cooperative communication with SHARQ schemes. It is observed that the latter of the two above scenarios results in throughput improvement of almost 4dB in terms of SNR.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125048515","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990382
M. H. Chaudhary, L. Vandendorpe
We propose a power allocation scheme for estimation in hierarchical wireless sensor networks. The sensors in the network are divided into disjoint clusters and each cluster observes a random source which is correlated with the sources being observed by other clusters. The estimation is performed in two steps: in the first step, the sensors in each cluster send a scaled version of their noisy measurements to their respective cluster-head (CH) which forms a preliminary estimate of the underlying source; and in the second step, the CHs send their partial estimates to a remote fusion center (FC) for final estimation. The estimates are based on LMMSE estimation rule. The communication between the sensors and the CHs, and between the CHs and the FC takes place on orthogonal channels. The proposed power allocation scheme minimizes the estimation distortion subject to constraints on the network power consumption. Effectiveness of the scheme is illustrated with simulation examples.
{"title":"Power constrained linear estimation of correlated sources in hierarchical wireless sensor networks","authors":"M. H. Chaudhary, L. Vandendorpe","doi":"10.1109/SPAWC.2011.5990382","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990382","url":null,"abstract":"We propose a power allocation scheme for estimation in hierarchical wireless sensor networks. The sensors in the network are divided into disjoint clusters and each cluster observes a random source which is correlated with the sources being observed by other clusters. The estimation is performed in two steps: in the first step, the sensors in each cluster send a scaled version of their noisy measurements to their respective cluster-head (CH) which forms a preliminary estimate of the underlying source; and in the second step, the CHs send their partial estimates to a remote fusion center (FC) for final estimation. The estimates are based on LMMSE estimation rule. The communication between the sensors and the CHs, and between the CHs and the FC takes place on orthogonal channels. The proposed power allocation scheme minimizes the estimation distortion subject to constraints on the network power consumption. Effectiveness of the scheme is illustrated with simulation examples.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122223807","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990473
A. Osmane, Sheng Yang, J. Belfiore
In wireless cooperative systems, the outage probability is a relevant performance measure from the information theoretic point of view. Deriving its exact value with respect to the relaying protocol parameters and for all the range of the Signal to Noise Ratio is in general a hard task. Instead, one can extract the outage gain in order to approximate the outage probability as the SNR goes to infinity at a fixed rate R. In this paper, we consider the layered two-hop relay channel, operating under the linear Rotate-and-Forward (RF) protocol, where each relay rotates its received signal and forwards it towards the destination. We consider two network configurations for which we derive exact outage gain values. We use the outage gain to compare the performance of the RF scheme to that of other schemes having the same diversity order. The derived outage gain values are verified through numerical simulations.
{"title":"On the performance of the Rotate-and-Forward protocol in the two-hop relay channels","authors":"A. Osmane, Sheng Yang, J. Belfiore","doi":"10.1109/SPAWC.2011.5990473","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990473","url":null,"abstract":"In wireless cooperative systems, the outage probability is a relevant performance measure from the information theoretic point of view. Deriving its exact value with respect to the relaying protocol parameters and for all the range of the Signal to Noise Ratio is in general a hard task. Instead, one can extract the outage gain in order to approximate the outage probability as the SNR goes to infinity at a fixed rate R. In this paper, we consider the layered two-hop relay channel, operating under the linear Rotate-and-Forward (RF) protocol, where each relay rotates its received signal and forwards it towards the destination. We consider two network configurations for which we derive exact outage gain values. We use the outage gain to compare the performance of the RF scheme to that of other schemes having the same diversity order. The derived outage gain values are verified through numerical simulations.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130360507","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990420
Stefan Schwarz, M. Rupp
Currently evolving wireless communication systems (e.g. LTE-A, WiMAX) are based on linearly precoded MIMO OFDM and utilize adaptive modulation and coding to adjust the code rate and modulation alphabet to the current channel conditions. For this purpose the transmitter requires channel knowledge, which is provided by means of receiver feedback, utilizing the rank, precoding matrix and channel quality indicators. This work presents algorithms for computing these feedback values. Our algorithms choose the rank and precoding matrix indicators to maximize the estimated user throughput, whereas the channel quality indicator is chosenmore conservatively to satisfy a given upper bound on the block error ratio. We demonstrate the performance of the proposed algorithms by means of link level simulations and comparison to theoretical bounds on the achievable throughput.
{"title":"Throughput maximizing feedback for MIMO OFDM based wireless communication systems","authors":"Stefan Schwarz, M. Rupp","doi":"10.1109/SPAWC.2011.5990420","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990420","url":null,"abstract":"Currently evolving wireless communication systems (e.g. LTE-A, WiMAX) are based on linearly precoded MIMO OFDM and utilize adaptive modulation and coding to adjust the code rate and modulation alphabet to the current channel conditions. For this purpose the transmitter requires channel knowledge, which is provided by means of receiver feedback, utilizing the rank, precoding matrix and channel quality indicators. This work presents algorithms for computing these feedback values. Our algorithms choose the rank and precoding matrix indicators to maximize the estimated user throughput, whereas the channel quality indicator is chosenmore conservatively to satisfy a given upper bound on the block error ratio. We demonstrate the performance of the proposed algorithms by means of link level simulations and comparison to theoretical bounds on the achievable throughput.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116564901","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990450
Eduard Axel Jorswieck, Jing Lv
This work considers the coexistence of a cognitive multiple-input multiple-output (MIMO)multiple access channel (MAC) system with a single-antenna legacy link which has a rate requirement. The legacy rate constraint is transformed into an interference constraint profile with individual interference temperature constraints (ITC) for the cognitive users. By spatial shaping (transmit covariance matrix optimization, linear precoding), an iterative algorithm is proposed to optimize the sum capacity of the cognitive MIMO MAC system, in which each user updates its transmit strategy with the transmit strategies of the other users fixed. The optimal single-user transmit strategy is obtained by comparing the achievable rate of two iterative algorithms, where transmit covariance matrix with either rank-one or rank-larger-than-one is optimized.
{"title":"Spatial shaping in cognitive MIMO MAC with coded legacy transmission","authors":"Eduard Axel Jorswieck, Jing Lv","doi":"10.1109/SPAWC.2011.5990450","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990450","url":null,"abstract":"This work considers the coexistence of a cognitive multiple-input multiple-output (MIMO)multiple access channel (MAC) system with a single-antenna legacy link which has a rate requirement. The legacy rate constraint is transformed into an interference constraint profile with individual interference temperature constraints (ITC) for the cognitive users. By spatial shaping (transmit covariance matrix optimization, linear precoding), an iterative algorithm is proposed to optimize the sum capacity of the cognitive MIMO MAC system, in which each user updates its transmit strategy with the transmit strategies of the other users fixed. The optimal single-user transmit strategy is obtained by comparing the achievable rate of two iterative algorithms, where transmit covariance matrix with either rank-one or rank-larger-than-one is optimized.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"448 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134277729","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990484
U. Salim
We study the simplest version of Gaussian fading Cognitive Radio (CR) interference channel which comprises of two transmitter-receiver pairs. The primary transmitter (PTx) and primary receiver (PRx) are equipped with single antenna each whereas the cognitive transmitter (CTx) and the cognitive receiver (CRx) may be equipped with multiple antennas in our setting although this pair is also restricted to single stream transmission. The channel state information is partial such that each transmitter knows its channel to the PRx but has no information about its channel to the CRx. This contribution proposes two simple transmission strategies focusing the CR channels in the so-called “overlay paradigm” where the CTx not only transmits its own message but helps as well transmitting the primary message. In the first strategy, the primary message is independently encoded at the two transmitters whereas the same primary message encoding is used in the second strategy which not only allows the coherent signal combining at the PRx but also the possibility of complete interference cancellation at the CRx even in the limiting case when the CRx is equipped only with two antennas. The simulation results demonstrate that the proposed strategy with same primary message encoding shows considerable performance benefit over the strategy where the primary message is independently encoded at the two transmitters.
{"title":"Achievable rate regions for cognitive radio Gaussian fading channels with partial CSIT","authors":"U. Salim","doi":"10.1109/SPAWC.2011.5990484","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990484","url":null,"abstract":"We study the simplest version of Gaussian fading Cognitive Radio (CR) interference channel which comprises of two transmitter-receiver pairs. The primary transmitter (PTx) and primary receiver (PRx) are equipped with single antenna each whereas the cognitive transmitter (CTx) and the cognitive receiver (CRx) may be equipped with multiple antennas in our setting although this pair is also restricted to single stream transmission. The channel state information is partial such that each transmitter knows its channel to the PRx but has no information about its channel to the CRx. This contribution proposes two simple transmission strategies focusing the CR channels in the so-called “overlay paradigm” where the CTx not only transmits its own message but helps as well transmitting the primary message. In the first strategy, the primary message is independently encoded at the two transmitters whereas the same primary message encoding is used in the second strategy which not only allows the coherent signal combining at the PRx but also the possibility of complete interference cancellation at the CRx even in the limiting case when the CRx is equipped only with two antennas. The simulation results demonstrate that the proposed strategy with same primary message encoding shows considerable performance benefit over the strategy where the primary message is independently encoded at the two transmitters.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116214426","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990406
Yaning Zou, M. Valkama, N. Ermolova, O. Tirkkonen
In this paper, we study the impact of an important RF impairment inside direct-conversion receiver, namely the I/Q imbalance, on the performance of OFDM radio link over frequency-selective Rayleigh fading channel. Closed-form expressions for link performance, in terms of detection error rate, ergodic capacity and outage capacity, under both frequency-selective RX I/Q imbalance and noisy frequency-selective fading channel are obtained as functions of image rejection ratios (IRRs) of the receiver front-end, average channel power delay profile as well as received SNR. The analysis results are then verified using extensive computer simulations. In general, the analysis shows that the performance of OFDM radio link under RX I/Q imbalance not only depends on the property of impairment itself but also depends on the correlation property of transmission channel. In this context, the proposed analysis provides fundamental understanding and very efficient tools for both circuit and system designers to accurately evaluate the I/Q imbalance effects in the OFDM radio link.
{"title":"Analytical performance of OFDM radio link under RX I/Q imbalance and frequency-selective Rayleigh fading channel","authors":"Yaning Zou, M. Valkama, N. Ermolova, O. Tirkkonen","doi":"10.1109/SPAWC.2011.5990406","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990406","url":null,"abstract":"In this paper, we study the impact of an important RF impairment inside direct-conversion receiver, namely the I/Q imbalance, on the performance of OFDM radio link over frequency-selective Rayleigh fading channel. Closed-form expressions for link performance, in terms of detection error rate, ergodic capacity and outage capacity, under both frequency-selective RX I/Q imbalance and noisy frequency-selective fading channel are obtained as functions of image rejection ratios (IRRs) of the receiver front-end, average channel power delay profile as well as received SNR. The analysis results are then verified using extensive computer simulations. In general, the analysis shows that the performance of OFDM radio link under RX I/Q imbalance not only depends on the property of impairment itself but also depends on the correlation property of transmission channel. In this context, the proposed analysis provides fundamental understanding and very efficient tools for both circuit and system designers to accurately evaluate the I/Q imbalance effects in the OFDM radio link.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114978629","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990387
B. Ellingsaeter, T. Maseng
In this paper we consider an OFDM multiuser system with K orthogonal subcarriers. We assume each user uses M-QAM modulation in each subcarrier. The modulation must be adaptive to cope with propagation changes and to meet the bit error rate requirement of the user. We maximize the sum of information bits per user selfishly, and compare the performance with other power allocation algorithms. Surprisingly, measuring rate by constellation size instead of Shannon's capacity yields a power allocation algorithm that differ widely from previously known power allocation algorithms, such as the iterative water filling algorithm (IWFA). This is because we only accept bit error rates better than 10−3 and the rate achieved with modulation can only be discrete values, whereas other algorithms based on Shannon's capacity can achieve any rate.
{"title":"Adaptive M-QAM signaling for dynamic spectrum access","authors":"B. Ellingsaeter, T. Maseng","doi":"10.1109/SPAWC.2011.5990387","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990387","url":null,"abstract":"In this paper we consider an OFDM multiuser system with K orthogonal subcarriers. We assume each user uses M-QAM modulation in each subcarrier. The modulation must be adaptive to cope with propagation changes and to meet the bit error rate requirement of the user. We maximize the sum of information bits per user selfishly, and compare the performance with other power allocation algorithms. Surprisingly, measuring rate by constellation size instead of Shannon's capacity yields a power allocation algorithm that differ widely from previously known power allocation algorithms, such as the iterative water filling algorithm (IWFA). This is because we only accept bit error rates better than 10−3 and the rate achieved with modulation can only be discrete values, whereas other algorithms based on Shannon's capacity can achieve any rate.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128266921","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 : 2011-06-26DOI: 10.1109/SPAWC.2011.5990447
M. Castañeda, J. Nossek
In a frequency division duplex system with a base station equipped with multiple antennas, the base station relies on feedback of the channel state information of the users in order to perform user selection and transmit beamforming in the downlink. Nonetheless, it is usually assumed that the feedback link is noise-free, i.e. the base station has access to error-free feedback. In practice, however, the feedback link is the uplink of the system and is subject to fading, possible multiuser interference and noise. In this work, with a given amount of resources reserved for the feedback of all the users, we tackle the system feedback design considering feedback errors. We take into account that the base station can detect the feedback of several users simultaneously by employing receive beamforming. In addition, we propose to exploit multiuser diversity in the feedback link in order to minimize the feedback error probability. We also present an orthogonal pilot design which enables the base station to estimate the feedback (uplink) channels of the users.
{"title":"Multiuser feedback design with multiple receive antennas","authors":"M. Castañeda, J. Nossek","doi":"10.1109/SPAWC.2011.5990447","DOIUrl":"https://doi.org/10.1109/SPAWC.2011.5990447","url":null,"abstract":"In a frequency division duplex system with a base station equipped with multiple antennas, the base station relies on feedback of the channel state information of the users in order to perform user selection and transmit beamforming in the downlink. Nonetheless, it is usually assumed that the feedback link is noise-free, i.e. the base station has access to error-free feedback. In practice, however, the feedback link is the uplink of the system and is subject to fading, possible multiuser interference and noise. In this work, with a given amount of resources reserved for the feedback of all the users, we tackle the system feedback design considering feedback errors. We take into account that the base station can detect the feedback of several users simultaneously by employing receive beamforming. In addition, we propose to exploit multiuser diversity in the feedback link in order to minimize the feedback error probability. We also present an orthogonal pilot design which enables the base station to estimate the feedback (uplink) channels of the users.","PeriodicalId":102244,"journal":{"name":"2011 IEEE 12th International Workshop on Signal Processing Advances in Wireless Communications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130546360","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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