Cooperative communications with partial channel state information: When to cooperate?

Ibrahim, Ahmed S.; Sadek, Ahmed K.; Su, Weifeng; Liu, K.J.R.

doi:10.1109/glocom.2005.1578321

Cited by 52 publications

(39 citation statements)

References 8 publications

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“…Symbol error rate (SER) for single-and multi-node DAF protocol was analyzed in [4] and [5], respectively. In [6] and [7], various relay selection schemes have been proposed that achieve high bandwidth efficiency and full diversity order. Finally, distributed space time codes for DAF and AAF protocols have been proposed and analyzed in [8].…”

Section: Introductionmentioning

confidence: 99%

Wireless network cocast: location-aware cooperative communications with linear network coding

Lai

Ibrahim

Liu

2009

IEEE Trans. Wireless Commun.

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Abstract-In wireless networks, reducing aggregate transmit power and in many cases, having even power distribution increase the network lifetime. Conventional direct transmission (DTX) scheme results in high aggregate transmit power and uneven power distribution. In this paper, we consider location-aware cooperation-based schemes namely immediate-neighbor cooperation (INC), maximal cooperation (MAX), and wireless network cocast (WNC) that achieve spatial diversity to reduce aggregate transmit power and even power distribution. INC utilizes twouser cooperative communication, resulting in good reduction of aggregate transmit power and low transmission delay; however, power distribution is still uneven. MAX utilizes multi-node cooperative communication, providing incremental diversity to achieve even power distribution and substantial reduction in aggregate transmit power. Transmission delay in MAX, however, grows quadratically with network sizes. As a result, the novel WNC is proposed to achieve incremental diversity as in MAX and low transmission delay as in INC. In WNC, mobile units acting as relays form unique linearly-coded signals from overheard signals and transmit them to the destination, where a multiuser detector jointly detects the symbols from all received signals. Performance evaluation in uniformly distributed networks shows that INC, MAX, and WNC substantially reduce aggregate transmit power while MAX and WNC also provide even power distribution.

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Section: Introductionmentioning

confidence: 99%

Wireless network cocast: location-aware cooperative communications with linear network coding

Lai

Ibrahim

Liu

2009

IEEE Trans. Wireless Commun.

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“…Cooperative communication protocols make use of the broadcast nature of wireless channels, where a number of relay nodes are assigned to help a source in forwarding its information to its destination, hence forming a virtual antenna array. Various cooperative diversity protocols were proposed and analyzed in [1], [2], [3], [4], [5], [6], [7], [8].…”

Section: Introductionmentioning

confidence: 99%

“…However, the bandwidth efficiency drops to 1/(N + 1) symbols per channel use (SPCU). In [5], [6] various relay selection cooperative schemes, in which only one relay forwards the source's information, have been proposed. It was illustrated that relay-selection cooperative schemes achieve high bandwidth efficiency while guaranteeing full diversity order.…”

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confidence: 99%

Mitigating channel estimation error via cooperative communications

Ibrahim

Liu

2009

2009 IEEE International Conference on Communications

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Abstract-Channel estimation error problem is among the main causes of performance degradation in wireless networks. In this paper, we investigate the impact of cooperative communications on mitigating the effect of channel estimation error. Two main performance criteria, namely, the traditional outage probability and the proposed signal-to-noise ratio (SNR) gap ratio, are utilized to characterize such impact. The SNR gap ratio measures the reduction in the SNR due to channel estimation error. Taking into consideration the channel estimation error, we show that the outage probability is reduced by utilizing cooperative transmission. We also show that cooperative transmission results in lower SNR gap ratio compared to that of the direct transmission. Thus, cooperative transmission is less susceptible to the effect of channel estimation error compared to direct transmission. Finally, we illustrate that increasing the number of cooperating relays reduces the effect of the channel estimation error more. I. INTRODUCTIONRecently, cooperative communications for wireless networks have gained much interest due to its ability to mitigate fading in wireless networks through achieving spatial diversity, while resolving the difficulties of installing multiple antennas on small communication terminals. Cooperative communication protocols make use of the broadcast nature of wireless channels, where a number of relay nodes are assigned to help a source in forwarding its information to its destination, hence forming a virtual antenna array. Various cooperative diversity protocols were proposed and analyzed in [4]. It was shown that the conventional cooperative communication scenario, in which each of the available N relays forwards the source's information over an orthogonal channel (e.g. time or frequency slot), achieves full diversity order equal to N +1. However, the bandwidth efficiency drops to 1/(N + 1) symbols per channel use (SPCU). In [5], [6] various relay selection cooperative schemes, in which only one relay forwards the source's information, have been proposed. It was illustrated that relay-selection cooperative schemes achieve high bandwidth efficiency while guaranteeing full diversity order. Distributed space-time cooperative schemes, in which the helping relays simultaneously forward modified version of the source's information, have been proposed and analyzed in [7], [8]. It was shown that distributed cooperative schemes, under certain conditions, can achieve full diversity order.Channel estimation error, caused possibly by Doppler shift or noise on the pilot signals, can cause dramatic performance degradation in wireless networks. In [9], it was examined that

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Section: ⅰ Introductionmentioning

confidence: 99%

“…This may waste bandwidth and power allocated for the relaying strategy if the relay fails to decode the source's information or if the direct channel is inadequate for the destination detecting the data. Previous work by others [5] and also by our group [6], which investigated the adaptive cooperative scheme with one R, showed some benefits regarding the data rate and the reliability of transmission when compared with other published alternatives.In this paper, we focus on the adaptive cooperation scheme with multiple relays in which the time and bandwidth can be saved, which has a higher reliability performance than conventional multi-relay schemes. First, by using the instantaneous SNR as the performance measure, D checks which of the direct path or the relay path is better, and then chooses the path having the higher SNR for the transmission.…”

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confidence: 99%

Adaptive Decode-and-Forward Cooperative Networks with Multiple Relay Nodes

Kong²

2011

Journal of electromagnetic engineering and science

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We propose an adaptive cooperative scheme with a multi-relay node that achieves high bandwidth efficiency and achieves better SEP performance. In the proposed protocol, if the quality of the direct channel is better than that of the all channels from relays to destination, the source will transmit directly to the destination. Otherwise, the source broadcasts the signal and then a potential relay will be chosen to help the source. A re-transmission will also occur if the potential relay cannot be detected. The spectral efficiency is first derived by calculating the probability of each mode, i.e., direct and cooperation transmission. Subsequently, the SEP performance of M-PSK modulation for the scheme is analyzed by considering each event where the source transmits data to the destination. Finally, the obtained analytical results are verified through computer simulations. Ⅰ. IntroductionCooperative diversity techniques have attracted considerable and increasing attention over the past several years [1]～ [3]. In cooperative communication, relays are assigned to help a source (S) forward its information to a destination (D); hence, a virtual antenna array can be formed, thereby achieving diversity. Various cooperative diversity protocols have been previously proposed and analyzed [1～4]. However, cooperation almost always occurs in these literature schemes. This may waste bandwidth and power allocated for the relaying strategy if the relay fails to decode the source's information or if the direct channel is inadequate for the destination detecting the data. Previous work by others [5] and also by our group [6], which investigated the adaptive cooperative scheme with one R, showed some benefits regarding the data rate and the reliability of transmission when compared with other published alternatives.In this paper, we focus on the adaptive cooperation scheme with multiple relays in which the time and bandwidth can be saved, which has a higher reliability performance than conventional multi-relay schemes. First, by using the instantaneous SNR as the performance measure, D checks which of the direct path or the relay path is better, and then chooses the path having the higher SNR for the transmission. If the direct channel is better than all other relay channels, then the source will directly transmit data to the destination with all power consumption. In contrast, if the direct link is not the best one, then the selection of the DF strategy will occur with the help of the relays that correctly decode the received signal. In this case, the source broadcasts the signal with a lower power in the first time slot. Afterward, the relay having the highest instantaneous SNR to the destination is chosen to retransmit the re-encoded signal. We also apply the re-transmission at S when a potential relay cannot be defined.Through mathematical analysis, we have studied the proposed scheme by investigating the spectral efficiency and the symbol error probability (SEP) performance. We obtain the spectral efficiency by derivin...

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Cooperative communications with partial channel state information: When to cooperate?

Cited by 52 publications

References 8 publications

Wireless network cocast: location-aware cooperative communications with linear network coding

Wireless network cocast: location-aware cooperative communications with linear network coding

Mitigating channel estimation error via cooperative communications

Adaptive Decode-and-Forward Cooperative Networks with Multiple Relay Nodes

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