Supporting mobile devices with wireless LAN/MAN in large controlled environments
IEEE Communications Magazine
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This paper discusses a link layer protocol that enhances performance of the Transmission Control Protocol (TCP) over a last-hop wireless network (LHWN) to make it more suitable for delivery of a live video with a short play out deadline. The presented protocol provides preference control of the transmission of video data within the network and it maximizes network goodput (the successfully transmitted amount of useful video data) by maximizing reliability of transmission for a given playout deadline and a varying digital bandwidth. The protocol makes use of the skip function in the TCP receiver to maximize end-to-end throughput of the connection at the expense of reducing full reliability. It can be implemented in a wireless access point to improve quality of the received live video over an Internet connection to an office or home. The main ideas of the protocol are: hide packet losses from the sender by performing local retransmissions based on the information from the video application and according to a certain scheduling policy, drop stale segments before they arrive at the receiver and prevent end-to-end retransmissions of segments received by the access point. The performance of the TCP Reno protocol in combination with both the presented protocol and the skip function in the receiver is compared against the performance of TCP Reno, the TCP-Real-Time Mode (RTM) protocol, TCP Reno in combination with the Snoop protocol and TCP-RTM in combination with Snoop. The results of simulations show improvement of network goodput across a wide range of packet-error rates.