An Improvement of TCP Downstream Between Heterogeneous Terminals in an Infrastructure Network

Abstract

We measured a performance of data transmission between a desktop PC and a PDA in an infrastructure network based on IEEE 802.11x wireless LAN. Assuming that a PDA is mainly used for downloading data from its stationary server, i.e., a desktop PC, a PC and a PDA acts as a fast sender and a slow receiver, respectively, due to substantial differences in their computational capabilities. With data transmission between these heterogeneous terminals a transmission time during downstream is slower than that during upstream by 20% at maximum. To mitigate this, we present two distinct approaches. First, by increasing the size of a receive buffer for a PDA the congestion window size of TCP becomes more stable. Thus, an approximate 32% increase in throughput can be obtained by increasing its size from 512 bytes to 32768 bytes. Second, a pre-determined delay between packets to be transmitted at the sender should be given. By assigning the inter-packet delay of 5 ms during downstream achieves a best performance which improves by 7% compared to that without such a delay. Besides, such a delay reduces the number of erroneous packets remarkably.