Capacity gain from transmit diversity methods in limited bandwidth GSM/EDGE networks

Diversity methods exploiting multiple transmit antennas can be used to enhance quality and capacity of GSM/EDGE radio access networks. This paper analyses the speech capacity improvement that can be obtained by using two transmit antennas and a combination of delay diversity and phase hopping. Capacity analysis is based on dynamic simulations of interference limited networks. Service quality against network load is measured for voice users on both BCCH and TCH frequencies. Results show that by applying transmit diversity on the BCCH layer its reuse can be tightened, which significantly improves system capacity by releasing frequencies to the TCH layer. Full capacity gains are achieved when transmit diversity is also applied on TCH carriers. It is seen that achievable gains are strongly dependent on the network bandwidth.