Channel State Dependent Packet Discard Policy for 3G Networks

Real-time packets are not useful to the receiver if they cannot arrive at the destination within their lifetimes. Discarding packets that are likely to expire after being delivered over the wireless link can increase network efficiency. However, due to delay and bit rate variability of 3G networks, a fixed threshold for packet lifetime discard is not adequate to achieve good throughput under dynamic channel conditions. This paper proposes a channel state dependent (CSD) lifetime packet discard policy. Considering ARQ retransmission as the dominant cause of delay variation and bit rate transitions, a four-state Markov model is used to study the performance of the CSD discard scheme. It is shown that the CSD approach yields better goodput than the channel state indifferent (CSI) approach. Since the scheme relies on accurate estimation of the channel state, impact of delayed knowledge of the channel state is also discussed