Impact of IEEE 802.16 ARQ mechanism on the performance of TCP-NewReno

Abstract

IEEE 802.16 supports Automatic Repeat request ARQ at the link layer to provide reliable service. ARQ retries sending a data-unit until the transmission is successful or maximum retries has reached. For applications which require reliability, the dropped data-unit is to be recovered at the transport layer level by TCP, which operates over ARQ. While TCP's retransmission policy continuously adjusts retransmission-timeout RTO based on the current round-trip-time, ARQ uses the static parameters set during the connection set-up procedure. This paper uses simulations to study the impact of one such static ARQ parameter, ARQ_BLOCK_LIFETIME on the performance of TCP-NewReno over IEEE 802.16 for Best Effort BE up-link traffic. Simulations were carried out using modified version of NS-2 WiMAX Simulator Release 2.6. The performance metric considered is TCP goodput. The results from the simulations show that the optimal value for ARQ_BLOCK_LIFETIME is influenced by Round Trip Time RTT, the network-load, and error-rate.