Spectral Efficient Protocols for Nonregenerative Half-duplex Relaying


Boris Rankov and Armin Wittneben


Allerton Conference on Communication, Control, and Computing, Monticello, IL, Sept. 2005.

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We study two-hop transmission schemes where relays assist the communication between one source/destination pair or multiple source/destination pairs. The relays operate in half-duplex mode, i.e., may not receive and transmit simultaneously at the same time and frequency. This leads to a loss in spectral efficiency due to the pre-log factor 1/2. We propose and study two nonregenerative relaying protocols that avoid the pre-log factor 1/2 but still operate in half-duplex mode. Firstly, we consider a relaying protocol where two half-duplex amplify-and-forward (AF) relays alternately forward messages from a source to a destination. The destination employs successive decoding with partial or full cancelation of the inter-relay interference. It is shown that the protocol can recover a significant portion of the half-duplex loss when the inter-relay channel is not too strong. Secondly, we propose a relaying protocol where a synchronous bidirectional connection between two nodes is established using one half-duplex relay and show that the sum rate achieves the rate of a full-duplex AF relay channel. We further extend this protocol to realize a bidirectional communication between multiple node pairs assisted by multiple nonregenerative zero-forcing relays.

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Copyright Notice: © 2005 B. Rankov and A. Wittneben.

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