| dc.description.abstract | In this dissertation, we study MIMO two-way relay networks consisting of singleantenna users which wish to exchange information with the help of multiple multiantenna relays. The problem we aim to solve is to minimize the total transmit power consumed in the entire network while certain quality-of-service constraints are satisfied at the transceivers. To do so, we optimize jointly the relays’ beamforming matrices and the transceivers’ transmit powers. We assume that networks use the multiple access broadcast (MABC) relaying scheme where each round of information exchange between the transceivers takes place in two time-slots. In Chapter 3, the network is assumed to be synchronous while in Chapter 4, we study asynchronous networks. In asynchronous networks, the data transmitted from transceivers will arrive with different delays at relays and the data forwarded from relays will arrive with different delays at each transceiver. In Chapter 5, we use a massive number of relay antennas in a two-way relay network with multiple peer-to-peer communications established with the help of multi-antenna relays. We observe that under the assumption that the relay beamforming matrices are symmetric, the total power minimization problems in synchronous and asynchronous networks are amenable to semi-closed-form solutions. Considering asynchronous networks, we prove rigorously that at the optimum, only those relays corresponding to the power-optimal synchronous sub-network of relays must contribute to the data exchange between transceivers. Equipping relays in the multipair two-way relay networks with massive number of antennas, we study performance of linear relaying techniques such as the maximum ratio transmitting/combining (MRT/MRC) and the zero-forcing (ZF) schemes. Exploiting the approximate orthogonality among relaytransceiver channel vectors when number of relay antennas are very large, we show that the total power minimization problem for networks with a massive number of relay antennas will be amenable to a semi-closed form solution. | en |
