Influence of channel BER on IEEE 802.11 DCF

Abstract

A new performance model of the IEEE 802.11 protocol is introduced that calculates throughput, average packet delay, packet drop probability and average packet drop time. This model is validated with simulation results using the OPNET TM simulation package. The proposed model predicts 802.11 protocol performance very accurately since it considers both transmission errors and packet retry limits. The effect of errors and network size on the performance of the basic access scheme, in terms of throughput, packet delay, packet drop time and drop probability is explored.Introduction: The IEEE 802.11 protocol [1] is the dominating standard for Wireless Local Area Networks (WLANs) and employs distributed co-ordination function (DCF) as the essential medium access control method. In DCF, a station transmits if the medium is idle. If the medium is sensed busy, the station waits until the current transmission is over. The station then defers for a randomly selected time interval to minimise collisions before transmitting. Each station maintains a retry count that indicates the number of retransmission attempts of a data packet. If the retry count reaches the specified limit, the packet is dropped.Since the release of the IEEE 802.11 standard many research efforts have been conducted on modelling IEEE 802.11 DCF. Bianchi in [2] uses a Markov chain to model the idealistic assumption that packet retransmissions are unlimited and a packet is being transmitted continuously until its successful reception. Wu et al. in [3] extends Bianchi's analysis to include the finite packet retry limits as defined in the IEEE 802.11 standard.In this Letter we introduce a mathematical model which extends the approach in [3] by taking into account both channel bit errors and packet retry limits for the basic access scheme. Our new performance model allows the calculation of the throughput efficiency, the average packet delay, the packet drop probability and the average time to drop a packet for the IEEE 802.11 protocol. Using OPNET simulation results, we validate our mathematical model and show that our model predicts DCF performance more accurately than Bianchi's model [2] that does not consider packet retry limits. Analytical results utilising our proposed model study the dependence of the protocol performance on the bit error rate (BER) and the network size.

Linear Approximation Model Throughput Performance Analysis of IEEE 802.11 Distributed Coordinated Function in Wireless Lossy Channel

“…(15) and (17) into Eq. (18), becomes the following: (19) The error probability of transmitting an RTS frame is defined as the following: (20) The error probability of transmitting a CTS frame is defined as the following:…”

“…A model that calculates the throughput, average packet delay, and packet drop probability has been proposed in [19], [20]. The authors considered the channel bit errors and packet retry limits of the basic access method and assumed that an error exists in the data frame.…”

Available Bandwidth Estimation and Prediction in Ad hoc Networks

“…To relax the dependence on the second assumption in (Bianchi, 2000), authors in (Chatzimisios, Boucouvalas et al, 2003) deal with the extension of Bianchi's Markov model in order to account for channel errors. And in (Qiao, Choi et al, 2002), the authors look at the impact of channel errors and the received SNR (Signal-to-Noise Ratio) on the achievable throughput in a system with rate adaptation, where the transmission rate of the terminal is adapted based on the link quality.…”

Modelling and Analysis of the Distributed Coordination Function of IEEE 802.11 with Multirate Capability

“…A number of papers [3]- [5], after the seminal work by Bianchi, have addressed the problem of modelling the DCF in a variety of traffic load and channel transmission conditions. Most of them focuses on a scenario presenting N saturated stations that transmit toward a common access point (AP) under the hypotheses that the packet rates along with the probability of transmission in a randomly chosen slot time is common to all the involved stations, while error events on the transmitted packets are mainly due to collisions between packets belonging to different stations.…”