ARQ-Aware Scheduling and Link Adaptation for Video Transmission over Mobile Broadband Networks

This paper studies the effect of ARQ retransmissions on packet error rate, delay, and jitter at the application layer for a real-time video transmission at 1.03 Mbps over a mobile broadband network. The effect of time-correlated channel errors for various Mobile Station (MS) velocities is evaluated. In the context of mobile WiMAX, the role of the ARQ Retry Timeout parameter and the maximum number of ARQ retransmissions is taken into account. ARQ-aware and channel-aware scheduling is assumed in order to allocate adequate resources according to the level of packet error rate and the number of ARQ retransmissions required. A novel metric, namely,goodput per frame, is proposed as a measure of transmission efficiency. Results show that to attain quasi error free transmission and low jitter (for real-time video QoS), only QPSK 1/2 can be used at mean channel SNR values between 12 dB and 16 dB, while 16QAM 1/2 can be used below 20 dB at walking speeds. However, these modes are shown to result in low transmission efficiency, attaining, for example, a total goodput of 3 Mbps at an SNR of 14 dB, for a block lifetime of 90 ms. It is shown that ARQ retransmissions are more effective at higher MS speeds.