2 research outputs found
Cooperative Algorithms for MIMO Amplify-and-Forward Relay Networks
Interference alignment is a signaling technique that provides high
multiplexing gain in the interference channel. It can be extended to multi-hop
interference channels, where relays aid transmission between sources and
destinations. In addition to coverage extension and capacity enhancement,
relays increase the multiplexing gain in the interference channel. In this
paper, three cooperative algorithms are proposed for a multiple-antenna
amplify-and-forward (AF) relay interference channel. The algorithms design the
transmitters and relays so that interference at the receivers can be aligned
and canceled. The first algorithm minimizes the sum power of enhanced noise
from the relays and interference at the receivers. The second and third
algorithms rely on a connection between mean square error and mutual
information to solve the end-to-end sum-rate maximization problem with either
equality or inequality power constraints via matrix-weighted sum mean square
error minimization. The resulting iterative algorithms converge to stationary
points of the corresponding optimization problems. Simulations show that the
proposed algorithms achieve higher end-to-end sum-rates and multiplexing gains
that existing strategies for AF relays, decode-and-forward relays, and direct
transmission. The first algorithm outperforms the other algorithms at high
signal-to-noise ratio (SNR) but performs worse than them at low SNR. Thanks to
power control, the third algorithm outperforms the second algorithm at the cost
of overhead.Comment: submitted to IEEE Transactions on Signal Processing in December 2011,
revised in April 2012 and in September 201