WSEAS Transactions on Communications
Print ISSN: 1109-2742, E-ISSN: 2224-2864
Volume 11, 2012
TCP-WLAware: Wireless Loss-Aware TCP for IEEE 802.16 Networks
Authors: ,
Abstract: The performance degradation of TCP in wireless and wired-wireless hybrid networks is mostly due to lack of its ability to differentiate the packet losses caused by network congestions from the wireless transmission losses [17]. In IEEE 802.16 networks, wireless loss can occur due to wireless link errors and when the number of bandwidth requests exceeds the maximum. ARQ retransmits the blocks in these two cases repeatedly for a specified number of times till the expiry of block life time and drops the block if the transmission is not successful. Block life time and Request Retries for bandwidth requests are static parameters which are set by the service provider irrespective of the current Round Trip Time, wireless nature and network load. TCP has to retransmit the segment when the retransmission timer expires for such losses if the current window is small. This paper shows that TCP’s throughput gets affected by the static parameters and proposes a cross layer feedback approach to enhance TCP-NewReno over IEEE 802.16 networks which can recover from such wireless packet losses and react without entering slow-start. The proposed scheme identifies the MAC block loss and informs the TCP sender about the loss which in turn resends the lost segment to which the block belongs before a time-out. This paper describes the design of the new proposed scheme, TCP-WLAware and presents results from experiments carried out using the NS-2 network simulator. The results from the simulations show that in a wireless congestion free environment, TCP-WLAware is able to apply TCP-NewReno’s fast recovery at more number of instances than that of the TCP-NewReno without the enhancement and hence, recover more number of segments.
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Keywords: Transmission Control protocol, TCP-NewReno, MAC, ARQ, Bandwidth requests, ARQ_BLOCK_LIFETIME, MAC layer feedback