Performance Analysis of IEEE 802.11e EDCA with QoS Enhancements through TXOP based Frame-concatenation and Block-acknowledgement

Enhanced distributed channel access (EDCA) protocol of IEEE 802.11e wireless local area networks (WLAN) standard supports access category (AC) wise quality of service (QoS) differentiation. But the EDCA does not fulfill the very stringent QoS requirements of hard real-time applications like interactive multi-media, video-conferencing. Keeping this in mind, in this research article, we have enhanced the quality of service feature of EDCA by adding transmission opportunity (TXOP) based frame-concatenation with block-acknowledgement scheme. Together with these enhancements, we have proposed an analytical model for the performance analysis of EDCA using three-dimensional Markov chain. The contemporary models of EDCA support only a small subset of features. Our analytical model covers all salient features of EDCA like multiple numbers of simultaneously active access categories (ACs) per station, internal collision handling, back-off counter freezing, post-back-off and frame discarding. Also, the enhanced frame-concatenation with block-acknowledgement feature is included. The proposed model incorporates different parameters for each AC for service differentiation. The computed throughput and delay characteristics for both simple EDCA and EDCA with enhanced frame-concatenation with block-acknowledgement scheme are thoroughly studied and compared. The comparison affirms the superior performance of our proposed model. Analytical and simulation results match pretty well and validate our model.