DocumentCode :
960498
Title :
Diversity–Multiplexing Tradeoff of Asynchronous Cooperative Diversity in Wireless Networks
Author :
Wei, Shuangqing
Author_Institution :
Louisiana State Univ., Baton Rouge
Volume :
53
Issue :
11
fYear :
2007
Firstpage :
4150
Lastpage :
4172
Abstract :
Synchronization of relay nodes is an important and critical issue in exploiting cooperative diversity in wireless networks. In this paper, two asynchronous cooperative diversity schemes are proposed, namely, distributed delay diversity and asynchronous space-time coded cooperative diversity schemes. In terms of the overall diversity-multiplexing (DM) tradeoff function, we show that the proposed independent coding based distributed delay diversity and asynchronous space-time coded cooperative diversity schemes achieve the same performance as the synchronous space-time coded approach which requires an accurate symbol-level timing synchronization to ensure signals arriving at the destination from different relay nodes are perfectly synchronized. This demonstrates diversity order is maintained even at the presence of asynchronism between relay node. Moreover, when all relay nodes succeed in decoding the source information, the asynchronous space-time coded approach is capable of achieving better DM tradeoff than synchronous schemes and performs equivalently to transmitting information through a parallel fading channel as far as the DM tradeoff is concerned. Our results suggest the benefits of fully exploiting the space-time degrees of freedom in multiple antenna systems by employing asynchronous space-time codes even in a frequency-flat-fading channel. In addition, it is shown asynchronous space-time coded systems are able to achieve higher mutual information than synchronous space-time coded systems for any finite signal-to-noise ratio (SNR) when properly selected baseband waveforms are employed.
Keywords :
antenna arrays; diversity reception; fading channels; multiplexing; radio networks; space-time codes; synchronisation; asynchronous space-time coded cooperative diversity schemes; baseband waveforms; distributed delay diversity; diversity-multiplexing tradeoff; frequency-flat-fading channel; multiple antenna systems; parallel fading channel; relay nodes; symbol-level timing synchronization; wireless networks; Decoding; Delay; Delta modulation; Fading; Frequency synchronization; Mutual information; Relays; Space time codes; Timing; Wireless networks; Asynchronous space–time codes; cooperative diversity; distributed delay diversity; diversity–multiplexing (DM) tradeoff; relay channels;
fLanguage :
English
Journal_Title :
Information Theory, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9448
Type :
jour
DOI :
10.1109/TIT.2007.907439
Filename :
4373438
Link To Document :
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