Dynamic Optimal Fragmentation for Goodput Enhancement in WLANs

Abstract

To meet the demand for broadband wireless communication, wireless systems should work well in typical wireless environments, characterized by the path loss of the signals, multipath fading, interference to adjacent channels, and random errors. IEEE 802.11 VVLANs use the unlicensed 2.4 GHz industrial, scientific and medical (ISM) band, which is vulnerable to noise generated by TVs, microwaves, and cordless phones. This paper proposes an algorithm to enhance system goodput through the dynamic optimal fragmentation. The number of contending stations, packet collisions, packet error probabilities, and fragmentation overheads are modeled in the analysis. Using an adaptive SNR estimator, the sender estimates the SNR of the receiver, and chooses a fragmentation threshold to shape arbitrary sized packets into optimal length packets. Through the rigorous analysis and extensive experiments with implemented test-bed, we show that the dynamic optimal fragmentation enhances the goodput approximately 18% in a typical WLAN environment. The experiment results reinforce that the algorithm is a comprehensive analytical model applicable to any CSMA/CA based MAC protocol for next generation wireless networks, and a realistic approach that can be deployed without changing the IEEE802.11 MAC protocol.