Comparison of power and combining gains on an ARQ-aided downlink time switched transmit diversity in a WCDMA LCR-TDD system

In this article, we investigate the impacts of power and combining gains on the performance of a Type I hybrid automatic repeat request (H-ARQ) aided downlink time-switched transmit diversity (TSTD) in a wideband code division multiple access low chip rate-time division duplex system, when a power ramping method is applied on the transmitter side and a chase combing scheme is employed on the receiver side. The power ramping scheme ramps up the transmission power and then retransmits the data, when the receiver sends a negative acknowledgment response signal to the transmitter. The performance is then compared to that of the conventional ARQ-aided TSTD. The simulation results demonstrate that the power ramping and the combining schemes in the ARQ-aided TSTD yield about a 6-dB performance gain in terms of the average Eb/N0, compared to the conventional ARQ-aided TSTD, when the mobile speed is 3 km/h and the frame error rate is 1%. In addition, a 3% throughput gain is achieved when the average Eb/N0 is equal to 0 dB.