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Yayın Power control for fading cooperative multiple access channels(IEEE, 2007-08) Kaya, Onur; Ulukuş, ŞennurFor a fading Gaussian multiple access channel with user cooperation, we obtain the power allocation policies that maximize the average rates achievable by block Markov superposition coding, subject to average power constraints. The optimal policies result in a coding scheme that is simpler than the one for a general multiple access channel with generalized feedback. This simpler coding scheme also leads to the possibility of formulating an otherwise non-concave optimization problem as a concave one. Using the perfect channel state information available at the transmitters to adapt the powers, we demonstrate gains over the achievable rates for existing cooperative systems.Yayın Achieving the capacity region boundary of fading CDMA channels via generalized iterative waterfilling(IEEE, 2006-11) Kaya, Onur; Ulukuş, ŞennurWe characterize the optimum power control policies that achieve arbitrary rate tuples on the boundary of the, capacity region of a power controlled, code division multiple access (CDMA) system in a fading channel with perfect channel state information (CSI). We propose a "generalized" waterfilling approach, and provide an iterative algorithm that solves for the optimum power allocation policy, for A given arbitrary rate tuple on the boundary of the capacity region. We then investigate the effects of limited feedback on the capacity region, and demonstrate that a good power control policy may require only a very low rate feedback.
