A high capacity cell architecture based on Alamouti coded relay strategy and frequency allocation scheme

In this paper, we propose a new cell architecture for the orthogonal frequency division multiple access (OFDMA) systems by jointly taking frequency allocation scheme (FAS) and cooperative relay strategy into consideration. To serve the mobile stations (MSs) in the inner zone and relay stations (RSs) in the outer zone, a larger portion of frequency spectrum is allocated to the central base station (BS) such that the transmission from BS to RSs can never be a bottleneck during the two-hop relay process. Also, a pair of RSs are assigned the same frequency spectrum to carry out Alamouti coded relay using a half of transmission power (compared with the conventional non-cooperative relay). Depending on the received signal quality, an MS can be served by the central BS or a pair of RSs. Consequently, in addition to the lower interference level by using FAS and half transmission power, the selection and transmission diversity gains can also contribute to a higher capacity and a lower outage probability. The advantage of the proposed cell architecture is proved via simulation and analytical results by taking the intercell interference in the multicell environment and complete channel effects into consideration, including the small and large scale fading. The analytical framework fulfills the task of complete performance analysis in the literature. Some suggestions for future works have also been provided.