CAPEL: A packet discard policy for real-time traffic over wireless networks

Real-time traffic has stringent delay requirement. However, bandwidth limited and error-prone wireless networks often show significant delay jitter. Traditional packet discarding schemes designed for high speed wired networks, such as Random Early Detection (RED), are inadequate for wireless networks with high latency and delay variability. This paper describes an analytical framework for designing lifetime packet discard policies and proposes the Channel State Aware Packet Discard on Expiration Likelihood (CAPEL) algorithm, which only admits packets with expiration likelihood below a pre-defined requirement. Its effectiveness for improving goodput is quantified under a time varying channel modeled by the Markov-Modulated Poisson Process (MMPP). In addition, we use Gamma Distribution to approximate the conditional system time distribution under the MMPP channel. It is verified to be accurate by simulation.