Abstract:
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This paper deals with the design of nonregenerative
relaying transceivers in cooperative systems where channel state
information (CSI) is available at the relay station. The conventional
nonregenerative approach is the amplify and forward
(A&F) approach, where the signal received at the relay is simply
amplified and retransmitted. In this paper, we propose an alternative
linear transceiver design for nonregenerative relaying
(including pure relaying and the cooperative transmission cases),
making proper use of CSI at the relay station. Specifically, we
design the optimum linear filtering performed on the data to be
forwarded at the relay. As optimization criteria, we have considered
the maximization of mutual information (that provides an
information rate for which reliable communication is possible) for
a given available transmission power at the relay station. Three
different levels of CSI can be considered at the relay station: only
first hop channel information (between the source and relay);
first hop channel and second hop channel (between relay and
destination) information, or a third situation where the relay
may have complete cooperative channel information including
all the links: first and second hop channels and also the direct
channel between source and destination. Despite the latter being
a more unrealistic situation, since it requires the destination to
inform the relay station about the direct channel, it is useful as an
upper benchmark. In this paper, we consider the last two cases
relating to CSI.We compare the performance so obtained with the
performance for the conventional A&F approach, and also with
the performance of regenerative relays and direct noncooperative
transmission for two particular cases: narrowband multiple-input
multiple-output transceivers and wideband single input single
output orthogonal frequency division multiplex transmissions. |