Capacity Scaling for MIMO Two-Way Relaying

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  • 19 July 2007
Abstract
This paper considers capacity scaling in a MIMO (multiple input multiple output) two-way relay channel where two nodes exchange data with each other through multiple relay nodes. The sources and relay nodes have multiple antennas and operate in half-duplex mode. The source nodes are assumed to have perfect receive channel state information for all the channels in the two-way relay network, while the relay nodes either know their own transmit and receive channel state information (the coherent case) or have no knowledge of the channel state (the non-coherent case). The main results in this paper are on capacity scaling of the two-way channel in independent and identically distributed Gaussian matrix channels for large numbers of relays. For both the coherent and non-coherent case, we characterize the capacity region of MIMO two-way relay channel, as the number of relays grow large. The coherent capacity region is shown to scale linearly with the number of source antennas and logarithmically with the number of relay nodes, while the non-coherent capacity is shown to scale linearly with the number of transmit antennas at the source nodes, and logarithmically with signal to noise ratio (SNR), exactly as in the point-to-point capacity for the independent and identically distributed MIMO Gaussian channel. A main conclusion is that MIMO two-way relay channels (both coherent and non-coherent) it is possible to asymptotically (in the number of relays) obtain unidirectional full-duplex performance while using only half-duplex nodes.

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