Enhanced Pulse Shaping Filters For IEEE 802.11 OFDM WLANs

Abstract

Several communication systems such as the IEEE 802.11 Wireless LAN standards use Orthogonal Frequency Division Multiplexing along with pulse shaping filters to mitigate the effect of Inter Symbol Interference (ISI).  Although several pulse shaping filters such as Raised Cosine (RC), Square Root Raised Cosine, Flipped Exponential Pulse (FEXP) and Parametric Exponential Pulse (PEXP) have been proposed, it is still possible to improve the performance of these filters. In this paper two enhanced pulse shaping filters have been proposed. The first one is a Modified FEXP (MFEXP) filter which uses a different transfer function that can be implemented at both the transmitter and receiver. The second one is a Hybrid FEXP and PEXP filter (HFPEXP) which is obtained by modifying the transfer function of the FEXP pulse and combining it with the PEXP pulse. Both proposed filters have been incorporated and tested in the IEEE 802.11 WLAN system with Additive White Gaussian (AWGN). Results show that the proposed filters provide superior Bit Error Rate (BER) performance than the conventional ones such as RC, SRCC, FEXP and PEXP for different ISI levels and their impulse response also result in smaller side lobes.