Performance analysis of IEEE 802.11n CSMA/CA 4×4 multi-user MIMO in erroneous channel

Multi-user multiple-input multiple-output (MU-MIMO) aware carrier sense multiple access with collision avoidance (CSMA/CA) is a simple MAC-layer approach toward MIMO adaptability in next generation IEEE 802.11n to boost the overall network performance. However, it is hypothetically that, the performance in terms of MAC throughput and delay of CSMA/CA-adopted MU-MIMO WLANs significantly degrade as the number of active stations increases, especially in scenarios where each station's load approaches its saturated condition as well as in environments where channels experience faded. In this paper, we propose modified MAC-layer control frames including request-to-send and control-to-send frames for CSMA/CA 4×4 MU-MIMO transmission. We then numerically model a system adapted Markovian chain to characterize the exponential backoff distribution of CSMA/CA process in 4× 4 MU-MIMO WLAN scenario, taking the erroneous channel into account. Based on the probability model, the network performance in terms of MAC saturation throughput and average access delay are analyzed. The numerical results clearly demonstrate the substantial impacts of the number of active stations involved in transmission as well as erroneous channel on the performance.