This thesis investigates multi-antenna techniques within the context of distributed antenna and fixed relay networks. Such antenna and network architectures result in significant performance enhancements even in networks where the wireless terminals have only a single antenna.; Relaying, the use of intermediate nodes to help transmission from source to destination, has emerged as one paradigm shift in system deployment. Infrastructure-based relays are usually deployed by the service providers for coverage extension. The thesis investigates cooperative relaying to extend this paradigm even further. By exploiting the broadcast nature of wireless channels, fixed relay nodes are engaged in two-hop cooperative protocols as means for removing the burden of multiple antennas on wireless terminals, thus, providing end-to-end (E2E) spatial diversity and network multiplexing benefits to terminals that are otherwise antenna-limited.; The deployment of a small number of antennas on infrastructure-based fixed relays is feasible, in contrast to mobile terminals; therefore, the thesis examines the impact of multi-antenna on the distributed cooperative fixed relays. Maximal ratio combining and selection combining of these multiple antenna signals in threshold-based decode-and-forward relays are studied and analyzed. It is found that the multi-antenna multi-relay scheme could be used to improve the E2E system performance, or for a given performance merit the multi-antenna component can significantly reduce the number of relays required in a service area. In addition, selection combining at the relays represents an excellent performance-cost tradeoff compared to single antenna relaying and maximal ratio combining based relaying.; Furthermore, relay-enabled user cooperation which exploits the infrastructure-based fixed relays is proposed. The explicit user cooperation diversity schemes studied in the literature require two willing users to form partnership. To sustain such a cooperative scheme, coercion or incentives for the cooperating partners might be needed, in addition to security concerns (as terminals have to detect partner's signals), which could present implementation challenges. Since the proposed cooperation schemes are transparent to the users, they present practical realizations for explicit user cooperation.; In all studied scenarios, simulations have been used to corroborate the system analyses conducted in the thesis. Mostly, the versatile Nakagami fading channel model has been used.
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