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This paper considers a Gaussian two-user multiple-input multiple-output (MIMO) multiple access channel (MAC) with cooperating encoders. After defining a form of cooperation strategy, we derive achievable rate bounds by applying the results obtained by Willems for the MAC with generalised feedback. Then, we characterise an achievable rate region and also provide a lower bound for this region, which are very close. Although the achievable rate bounds are described by non-concave functions, the boundary of the achievable rate region could be generated by maximising a weighted sum of the rates. Numerical results obtained generally exceed the capacity region of a MIMO MAC without cooperation. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, we investigate the sum capacity of a noisy multiple access channel (MAC): the T-user N-frequency noiseless MAC in cascade with a noisy channel. The noisy channel includes frequency-selective Rayleigh fading and Additive White Gaussian Noise (AWGN). The receiver may use multiuser detection (MUD) or single user detection (SUD). We show that when using SUD, the uniform distribution achieves sum capacity. Considering MUD and assuming that all users have the same input distribution, we show through numerical optimisation, that, for most relevant values of T and N, a product of uniform input distributions maximises a tight upper bound on sum capacity. Numerical results were obtained and it was observed that, for fixed N, there is a value of T which maximises sum capacity. As expected, the results also show that there is a significant gain in sum capacity when MUD is used. Copyright © 2009 John Wiley & Sons, Ltd.