Analysis of cooperative relaying in an urban scenario

For tactical military communication independence of a fixed infrastructure, base stations or central node is an advantage. Multihop routing in ad hoc networks have these benefits, it is, however, highly dependent on accurate link status in the network to find routes which can be problematic in mobile scenarios. A relatively new concept of cooperative relaying, in which several relay nodes simultaneously retransmits identical copies of the message on the same channel, is promising as it eliminates the need of routing. In this paper, we analyze the performance of an OFDM based cooperative simultaneous relaying scheme in a city scenario with relay nodes located at the same street. The performance is evaluated on measured channels for the individual links and compared with the performance of a traditional single relay technique. The results show that in the investigated scenario, cooperative relaying can increase the median path gain several dB compared to a single relay. However, even if the median path gain is higher there are occurrences of lower path gain with cooperation than with a single relay. The number of occurrences are decreased with more cooperating nodes and can be further decreased by specific cooperative relay techniques, such as phase dithering or delay diversity.