Further results on the MIMO degraded relay channel undergoing keyhole effects (無線通信システム)

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A MIMO keyhole is a propagation environment such that the channel gain matrix has unit rank (single degree of freedom), irrespective of the number of deployed antennas or their correlations (spacing), thereby reducing the MIMO channel capacity to that of a SISO channel. Related literature seems to consider such degeneration hopeless. Contrarily to this general belief, in a previous work the authors demonstrated that cooperative diversity can mitigate keyhole effects. Precisely, the authors have provided a necessary and sufficient condition to mitigate the keyhole effect in wireless MIMO systems through cooperative diversity (relay deployment). Though the previous work efficiently mitigates the keyhole effect, it requires periodic update of the relay power level everytime the channel matrices change, which can be a hurdle in situations where channel state information (CSI) acquisition is difficult or unreliable. Thus, the authors provide in this work a sufficient condition for keyhole effect mitigation in wireless MIMO systems that does not require any channel state information. By investigating the ergodic capacity of the MIMO degraded relay channel, we determine a power threshold for the relay average transmit power that ensures keyhole effect mitigation, and we explicit this power threshold in closed form. Simulation results demonstrate a striking similarity of the average constraint provided in this work with the instantaneous constraint provided in our previous work.
2009-11-19

Further results on the MIMO degraded relay channel undergoing keyhole effects (無線通信システム)

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