Performance Evaluation of IEEE 802.11 DCF Networks

Abstract

Abstract. The paper presents a new analytical saturation throughput model of IEEE 802.11 DCF (Distributed Coordination Function) with basic access in adhoc mode. The model takes into account freezing of the backoff timer when a station senses a busy channel. It is shown that taking into account this feature of DCF is important in modeling saturation throughput -yields more accurate results than models known from literature. The proposed analytical model also takes into account the effect of transmission errors.

A performance analysis of HICCUPS—a steganographic system for WLAN

“…The analysis is similar to effort done for the 802.11 CSMA/CA networks in [2][3][4][5]7]. Figure 1 illustrates four states of the channel that could occur during the corrupted frame mode.…”

“…In this mode all 802.11 frames have incorrect value of CRC-32 code deliberately set in the FCS field (Frame Checksum Control). Thus, there are no positive acknowledgments through ACK (ACKnowledgment) frames, and therefore "ACK error" state is omitted [2][3][4][5]7]. The "success" of the transmission in the HICCUPS, not defined in the same way as for the 802.11 network, means that during transmission there were no collisions and no data errors.…”

“…Let τ H be a probability of frame transmission in the corrupted frame mode, p e_data a probability of data frame error (see the formula (22) in [3]). These are related to channel state probabilities as follows (see (12) in [3]):…”

“…2.2 Probability of frame transmission in the corrupted frame mode-τ H Based on the model presented and evaluated in [2][3][4][5]7] let us consider a model of the 802.11 CSMA/CA backoff procedure in corrupted frame mode. From a WLAN perspective of the HICCUPS, communication always fails, because of absence of proper checksums.…”

“…For the purpose of this analysis the Markov chain-based model was used which is dedicated for 802.11 CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance; [2][3][4][5]7]). The cost of system usage (κ) is defined as a decline of WLAN throughput that results from the HICCUPS operating in the corrupted frame mode [6].…”