Improving TCP and UDP performance over wireless networks using quality of delivery (QoD) aware wireless systems

Wireless networks are fast-growing technologies having the advantage of enabling mobility. TCP (transmission control protocol) and UDP (user datagram protocol) are the main transport protocols used in wired networks. TCP Reno is one of the most widely adopted algorithms today for TCP congestion control. TCP Reno assumes that network congestion is the main cause of packet loss (i.e. damage or drop). This assumption is based on the negligibility of bit error rate (BER) over wired networks. Actually, this is not true in wireless environments where the bit error rate is high and a lot of severe conditions exist, such as links cross interference, weather conditions, and urban obstacles. Furthermore, the used ARQ (automatic repeat request) may degrade the quality of delivery (QoD) significantly due to its poor recovery techniques and high number of retransmissions. On the other hand, UDP provides unreliable transport services. However, real-time video streaming over IP is a challenging UDP application due to its typical popularity period. Asymmetry in bandwidth between wired (high bandwidth) and wireless environments (low bandwidth) is a very serious problem while downloading any MPEG video over WiFi (wireless LAN or IEEE 802.11), which is very common today. This problem causes severe problems on those wireless backbone routers due to high-untolerated system flow and may also cause network congestion accordingly.; In this dissertation, powerful wireless systems are proposed that significantly improve the performance of TCP and UDP over wireless environments. The major goal of the proposed wireless systems is to maintain the QoD over wireless environments for TCP applications by maintaining an end-to-end error-free, complete, and as quick as possible delivery, and for UDP applications (e.g., real-time video streaming) by affording a delivery of as many good frames as possible for any compressed video, like MPEG video with high quality, while reducing network congestion. To improve TCP services over wireless links, a wireless system (like wireless access points, wireless routers, or wireless end points) is proposed with finite system capacity that basically employs Type 1 hybrid ARQ with powerful and adaptive link-layer error detecting and recovery techniques. Furthermore, the affect of these error recovery techniques is studied together with the incoming traffic on the wireless device's finite buffer. In addition, a wireless system is proposed with powerful and efficient methodologies to maintain the QoD. To improve UDP over wireless environments, a QoD-aware wireless hop system is proposed that is able to deliver to the wireless subscribers as many good frames as possible in an intelligent and efficient manner. To accomplish that, the frameput, reasonable system capacity, and peer-to-peer acknowledgments approaches are proposed.