| Collaborative communication systems are wireless communication systems designed to exploit cooperation among users to mitigate the effects of multipath fading. These systems consist of several nodes jointly communicating to a common destination node. In fairly general conditions, it has been shown that these systems can achieve the diversity order of an equivalent MIMO channel and, if the node geometry permits, virtually the same outage probability can be achieved as that of the equivalent MIMO channel for a wide range of applicable SNR. However, much of the prior analysis has been performed under the assumption of perfect timing and frequency offset synchronization. We derive the estimation bounds and associated maximum a posteriori estimators for frequency offset estimation in a collaborative communication system. We show the benefit of adaptively tuning the frequency of the relay node in order to reduce estimation error at the destination.; We next derive an algorithm that designs training sequences that minimize the Cramer-Rao Bound for frequency estimation in a frequency-selective environment for a multiple node collaborative communication system. These algorithms design the best training sequence given the worst case propagation channel. We also derive computationally efficient estimation algorithms, which have mean squared error close to the Cramer-Rao Bound for some range of SNR.; We conclude the thesis by considering a cooperative system which shares only the channel state information among all users. With this information at each transmitter, the high signal-to-noise ratio capacity of the symmetric MIMO interference channel is characterized as a function of the interference-to-noise ratio. This work is a multiple antenna extension of the degrees of freedom expressions derived by Etkin et al. (2006) for the single antenna case. This characterization considers the case where the number of receive antennas is greater than or equal to the number of transmit antennas and shows the number of degrees of freedom available for communication as a function of log(INR)/log(SNR). |
