Influence of the Limited Retransmission on the Performance of WLANs Using Error-Prone Channel

Abstract

In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have been done either under assumption of idealistic channel condition or with unlimited retransmitting number. This paper is devoted to investigate influence of limited retransmissions and error level in the utilizing channel on the network throughput, probability of packet dropping and time to drop a packet. The results show that for networks using basic access mechanism the throughput is suppressed with increasing amount of errors in the transmitting channel over all the range of the retry limit. It is also quite sensitive to the size of the network. On the other side, the networks using four-way handshaking mechanism has a good immunity against the error over the available range of retry limits. Also the throughput is unchangeable with size of the network over the range of retransmission limits. However, the throughput does not change with retry limits when it exceeds the maximum number of the backoff stage in both DCF’s mechanisms. In both mechanisms the probability of dropping a packet is a decreasing function with number of retransmissions and the time to drop a packet in the queue of a station is a strong function to the number of retry limit, size of the network, the utilizing medium access mechanism and amount of errors in the channel

Evaluating Cross-Layer Cooperation of Congestion and Flow Control in IEEE 802.11s Networks

“…Especially the latter is a main focus of our work. Authors in [11] conduct model-based studies on the 802.11 DCF. They confirm that packet drop decreases with a higher number of frame retransmissions whereas delay increases.…”

“…Values for CW init and CW max depend on the applied 802. 11 To have an administrative control over ARQ, an upper retry limit can be set for a WLAN network interface. Based on the parameters described, maximum duration of a successful EDCA-based single-hop single-frame transmission, needing a certain number of ARQ retries R, can be approximated as the sum off time (T Sum ) needed for successful transmission of the frame (T F ) and its ACK (T ACK ), and the delay imposed by ARQ retransmissions (T ARQ ) [12]:…”

“…Nevertheless, corresponding mechanisms for flow control at both TCP and 802.11 level need to be tuned carefully to prevent interference [10], [11]. On the one hand, ARQ is beneficial to hide wireless loss from TCP and avoid unnecessary segment retransmissions, which are costly due to inherent reduction of the sending window.…”