Performance analysis of multiple reject ARQ theme at RLC layer in 3G

In this paper, we analyze the ARQ mechanism at RLC (radio link control) layer in a UMTS WCDMA system in detail and get good throughput and waiting time approximations. The ARQ method proposed in WCDMA belongs to multiple reject (MR) ARQ methods that outperforms the normal Go-back-N and selective repeat methods especially under inferior conditions of wireless communications. According to 3GPP specifications, the traffic rate varies from 3.4 kbit/s to 2 Mbit/s, and may be asymmetrical between uplink and downlink. To reach the peak or near-peak throughput, different parameters should be used with different traffic types and different directions. The main purpose of this paper is to analyze the performance of MR and study how the parameters affect the performance. We have also implemented the whole protocol stack on a hardware platform and done many experiments under different SNR channels. Based on the analysis and experiments, we can give good advice on timer control and buffer control of RLC layer in 3G.