Influence of adaptive RTS/CTS retransmissions on TCP in wireless and ad-hoc networks

Abstract

The trend of wireless networking is growing. This is due to the success of IEEE 802.11 WLAN technology which allows the extension of local area networks by mobile stations and establishing of ad-hoc networks. The latter does not need any pre-installed infrastructure. Nodes communicate directly or the traffic is relayed over intermediate wireless nodes.While there are only few nodes the performance of the network is acceptable, but with increasing number of nodes the performance of the network decreases. If TCP is used additional performance degradation is expected. However, TCP is necessary since most applications and application level protocols are based on it. The poor performance of TCP in wireless networks has several reasons, especially the communication medium with high bit error rates (BER) and TCP's optimization on fixed networks.In this paper, we present an analysis of TCP's performance in wireless and ad-hoc networks. We emphasize the role of MAC layer retransmissions without breaking the end-to-end semantic of TCP. For this, we introduce the dynamic short retry limit which allows the adaptation of RT-S/CTS retransmissions. IntroductionThe trend of wireless networking is growing more and more. Since this networks provides the flexibility users wish. At this time wireless networks according to IEEE 802.11 and its successor 802.11b are widespread. In most of the cases wireless networks are used to enhance existing wired local area networks (LAN). However, applications which demand for a wireless network without any infrastructure arise. The latter case is also known as ad-hoc network and is also supported by IEEE 802.11.If we focus on applications we observe that most of them do not have any interest in what kind of network is used. The reason for this is, that applications use a transport service which is provided by the operating system. In the internet and in nearly all intranets the transmission control protocol (TCP) is used for this service. As an extension to existing wired networks the wireless networks have to support the same protocols. From the application point of view, the wireless networks have to provide TCP, since most applications and application level protocols are based on it. Unfortunately, TCP performs very poor in wireless networks which is caused by its inability to distinguish between congestion and lost packets [GV02, LS01, JKK00, AASS00, HV99, GTea99, WL99].According to ISO/OSI and the TCP/IP reference models a communication stack consists of several layers which are responsible for a certain job. Each of the layer should work independent from others. Unfortunately, this results in poor network performance when the foundation of the communication changes, i.e. the communication medium, which is true in the case of wireless network and TCP, hence TCP is optimized for fixed networks which communicate over cables.In this paper we consider the transport layer and the data link layer and their cooperation. From some point of view both have a similar task. The transport layer is respon...

A Power-Efficient Clustering Protocol for Coal Mine Face Monitoring with Wireless Sensor Networks Under Channel Fading Conditions

“…When the maximum value of the counter is reached, it gives up the transmission and discards the frame, with the counter reset to 0. Experiments prove that it is most ideal when the maximum value of is set to 6 [ 36 , 37 ].…”

Node Movement Detection to Overcome False Route Failures in Mobile Ad Hoc Networks

“…Recently, mechanisms to prevent unnecessary route reestablishments due to false route failures have been proposed [5][6][7][8][9][10]. [5][6][7][8] prevent unnecessary route reestablishments by controlling the traffic rate via a congestion control algorithm.…”

“…Because both mechanisms rely on the transport layer, they are not able to handle incorrect operations of network and MAC layers. [9] proposes an adaptive RTS/CTS retransmission scheme that reduces unnecessary route reestablishments by adaptively changing the retry limit of the MAC layer, but this mechanism operates depending on TCP and does not consider wireless link collisions. In [10], the delayed retransmission (DR) mechanism is proposed to overcome false route failures by retransmitting a packet once if its original delivery is turned out to be a failure.…”

CogMAC: a cognitive link layer for wireless local area networks

“…However, this metric is difficult to derive. Therefore, the adaptability of RTS/CTS is proposed as a function of the packet delivery ratio [14] or as a process based on the history of previous packets [9].…”