Novel transmit diversity techniques for broadcast services in cellular networks

In this paper, we investigate transmit diversity techniques, which can be easily applied to OFDM-based broadcast and multicast systems. The focus is to provide diversity schemes, which can be implemented in existing OFDM-based systems with minimum changes in system operations. It is also possible to combine these techniques in a suitable manner. The broadcast service provides the ability to transmit the same information stream to multiple users simultaneously. Transmitting the same signal to multiple users, however, may not be an efficient technique in cellular network since it cannot provide sufficient diversity gain. Here we propose OFDM-based efficient transmission techniques utilizing cyclic delay diversity which maximizes the macrodiversity gain from multiple base stations and enhances system performance of broadcast and multicast services in cellular networks. Computer simulation results show that the introduced cyclic delay diversity techniques increase the diversity order greatly, and also by combining existing transmit diversity scheme such as ´Alamouti´ method, we can further increase the diversity.