Exact BER analysis of distributed Alamouti's code for cooperative diversity networks
IEEE Transactions on Communications
Relay technologies for WiMAX and LTE-advanced mobile systems
IEEE Communications Magazine
End-to-end performance of transmission systems with relays over Rayleigh-fading channels
IEEE Transactions on Wireless Communications
Exact symbol error probability of a Cooperative network in a Rayleigh-fading environment
IEEE Transactions on Wireless Communications
On the performance of distributed space-time coding systems with one and two non-regenerative relays
IEEE Transactions on Wireless Communications
IEEE Transactions on Information Theory
Distributed space-time-coded protocols for exploiting cooperative diversity in wireless networks
IEEE Transactions on Information Theory
A simple transmit diversity technique for wireless communications
IEEE Journal on Selected Areas in Communications
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In this paper, we deal with two mode switching strategies for capacity-optimum transmission over a cooperative relay network. Both of them switch the transmission mode back and forth between a cooperative mode and a non-cooperative mode based on their corresponding spectral efficiencies. We use the distributed Alamouti code [1] for the cooperative mode transmission. The first strategy uses the same frame structure in both the cooperative and non-cooperative modes. In the cooperative mode, a source node S transmits two signals to a relay node R and a destination node D over two consecutive time slots during the 1st phase. During the 2nd phase, S and R transmit again cooperatively the same set of the above two signals to D over two consecutive time slots according to the Alamouti encoding rule, and then D detects jointly the two signals received over two consecutive phases. Sometimes a spectral efficiency of the S-D link might be higher than that of the S-R link. In such a case, cooperative transmission might not be better any longer and non-cooperative transmission in which D does not take any relayed replicas of the two signals would be recommended. We also introduce the 2nd disruptive strategy that changes disruptively the frame structure between the cooperative and non-cooperative modes in order to utilize best the radio resource in the non-cooperative mode. In the non-cooperative mode, one signal for every slot is transmitted only through the S-D link with no interruption for relaying. Numerical and simulation results show that the second one can provide almost twice the spectral efficiency than the first one does, though it may need a little forward signaling that S notifies the mode change status to D. The performance of the second strategy gets improved more significantly as the signal-to-noise ratio (SNR) of the S-R link is getting low and/or the SNR of the S -D link is getting high.