Performance comparison of 802.11 DCF in fading with OFDM and diversity

Abstract

Performance of IEEE 802.11 distributed co-ordination function (DCF) Medium Access Control (MAC) significantly degrades in fading channel conditions because of both collisions and fading. In order to enhance the system performance in these circumstances, multiple antenna systems and Orthogonal Frequency Division Multiplexing (OFDM) are used at physical layer. In this paper an interlayer analysis is performed between physical layer and MAC layer to investigate the throughput performance of WLAN. The system is simulated using Orthogonal Frequency Division Multiplexing (OFDM) without diversity, OFDM with Selection Combining (SC) and Maximal Ratio Combining (MRC). At physical layer Bit Error Rate (BER) for different physical (PHY) layers is simulated and calculated Packet Error Rate (PER) plotted as a function of bit energy to noise power (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> ). DCF is simulated taking account of channel fading and performance of MAC layer is evaluated in terms of throughput. Results find that OFDM with diversity gives better performance in terms of PER and throughput, as compared to physical layers without diversity. These outcomes can be used to select a particular PHY layer technique for WLAN under fading channel conditions.