Power allocation for Gaussian multiple access channel with noisy cooperative links

In this paper, a new coding scheme for the multiple access channel (MAC) with noisy cooperative links is proposed. The cooperation cost is modelled by powers spent on exchanging common information at transmitters. The optimal power allocation policy is derived to explore the tradeoff between cooperation and transmission. For some important cases, optimal power allocation that maximizes weighted sum rate, is found analytically. The sufficient and necessary condition for which the sum and the individual rates are simultaneously maximized, is identified. Analytical and numerical results suggest that the transmitter, whose power budget is dominated by that of the other, acts purely as a relay. The cooperation gain becomes more significant when the difference between the power budgets is smaller.