Performance tradeoffs between maximum ratio transmission and switched-transmit diversity

Implementation of maximum ratio transmission (MRT) systems is not a trivial task. Alternatively, switched-transmitter diversity (STD) systems are less difficult to implement, but their performance is suboptimal when compared to MRT systems. If the difference is not significant, implementation advantages of STD systems outweigh the minor performance loss so that these systems are desirable for practical implementations. This paper compares the performances between MRT and STD systems under Rayleigh-fading conditions for 2×1, 2×2 and 4× (transmit antennas×receive antennas) configurations. It is found that the differences are only about 1 dB for the 2×1 and 2×2 configurations, indicating that implementation simplicity of a STD system can be utilized without sacrificing too much performance. However, the difference is around 3 dB for the 4× configuration. The considerably larger loss prompts system designers to consider more critically on the tradeoffs between implementation aspects and performances of STD and MRT systems