Modeling Nonsaturated IEEE 802.11ax Networks with the Coexistence of UORA and UONRA in Imperfect Channels

This study introduces an analytical model for a nonsaturated IEEE 802.11ax network, designed to capture the coexistence characteristics of uplink orthogonal frequency division multiple access (OFDMA)-based random access (UORA) and non-random access (UONRA) mechanisms under imperfect channels. Existing models fail to assess this realistic network due to three issues: 1. When accounting for frame aggregation, imperfect channels, and queue buffer, the network exhibits an overwhelming number of states, which renders the evaluation of its performance infeasible. 2. Existing bulk-service queue models fail to evaluate these queue characteristics influenced by imperfect channels. 3. The coexistence characteristics of the two mechanisms remain unexplored due to their complex interactions. To address Issue 1, we propose two designs: device updates and hardware implementation, which reduce the massive states and facilitate the network evaluation. To address Issue 2, we have developed a feedback-driven bulk-service queue model that captures the joint effects of imperfect channels and queue characteristics. To address Issue 3, we comprehensively analyzed the joint impact of the two mechanisms from a probabilistic perspective. Extensive simulations demonstrate that the proposed model accurately captures network performance (throughput, delay, and collision probability) and reduces the mean estimation error by a factor of 30 compared to existing studies.