ABSTRACT
We study the impact of multiple amplify-and-forward relays on the achievable rate of wireless multiple-input multiple-output (MIMO) channels. For wireless networks with one source/destination pair (equipped with multiple antennas) and several single antenna amplify-and-forward relays (AF) we determine the compound (over two time slots) channel matrix of the relay-assisted MIMO channel. We show that with two-hop relaying, one can shape the channel matrix to be better conditioned and therefore increase the capacity of rank-deficient MIMO channels. We propose to use AF relays that act as active scatterers and assist the communication between the source and the destination terminal. We consider two cases: First, the relay antennas are connected through a wired backbone (distributed relay array) and the linear signal processing is done in a central unit also connected to this backbone. Second, we look at the case where the relays operate stand-alone, i.e, without a backbone connection. The goal of relaying, in both cases, is
to increase the rank of the compound (two time slots) channel matrix and to shape the eigenvalue distribution such that the channel matrix becomes well-conditioned and the capacity of the MIMO channel increases.
