Performance Analysis and Energy Efficiency of MU- (OFDMA & MIMO) Based Hybrid MAC Protocol of IEEE 802.11ax WLANs

Future wireless networks are characterized by densely populated stations (STAs) with limited battery capacity. These networks demand high aggregate throughput, increased energy efficiency, and high Random Access (RA) capability, i.e., the system's ability to allow new STAs to join the network quickly. WiFi-6 (also known as IEEE 802.11 ax) is the new generation WLAN standard proposed to meet these diverse system requirements. In this paper, we analyze the effect of Multi-User Multi-Input Multi-Output (MU-MIMO)
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MU-Orthogonal Frequency Division Multiple Access (MU-OFDMA)-based Hybrid Access (HA) mechanism of WiFi-6 systems. We propose a fixed Point model for analyzing this HA mechanism. By solving the system model, we investigate the impact on critical system metrics such as throughput, energy efficiency, Random Access capability, and delay due to a variation in (i) the number of resource units (RUs), (ii) the channel sounding interval, and (iii) the Target Wake-Up time interval. We have studied the effect of the non-saturated traffic model driven by the Poisson and Pareto arrival processes. Further, we have modeled the buffer status-based dynamic scheduling of RUs for the MU-OFDMA-based HA mechanism. We have also analyzed the novel Multi-Traffic Identifier-based frame aggregation feature. Further, we have analyzed the hand-off mechanism for a multi-BSS (Basic Service Set) scenario using the Stochastic geometry-based mathematical tool. We have used Matlab-based simulations for our study and found that the simulation results closely match the analytical results. Our study sheds light on the trade-off that exists between different performance metrics of the 802.11ax HA mechanism.