Auxiliary timeout and selective packet discard schemes to improve TCP performance in PCN environment

We consider how to improve the performance of the TCP connections over personal communication networks by introducing the auxiliary timeout and selective packet discard schemes. Because TCP is a reliable transport protocol tuned to reliable wired networks, we need a data link protocol to supplement the TCP to overcome unreliable error environment in wireless networks. In this case, however, the data link protocol can interact with the TCP and thus influence the TCP performance. According to computer simulations, when the selective repeat ARQ is used as the data link protocol in the fading channel, the throughput decreases as the fading frequency increases; and when the fading frequency is low, TCP retransmission occurs spuriously and the throughput decreases due to delay variation and the misunderstanding of congestion. In order to solve these problems we introduce the auxiliary timeout and selective packet discard schemes. The auxiliary timeout keeps the rule of the congestion control in traditional networks and avoids spurious retransmissions and misbehaved congestion controls by acknowledging the delayed ACK. The selective packet discard is designed to avoid retransmitting data packets that the mobile station has acknowledged or will acknowledge soon at the base station, thus saving the wireless bandwidth. Therefore the proposed schemes can help to improve the TCP performance in wireless networks by increasing throughput and reducing spurious retransmissions.