Experimental evaluation of downlink communication performance of IEEE 802.11ax wireless LAN: OFDM vs. OFDMA

Although Orthogonal Frequency Division Multiple Access (OFDMA), adopted in IEEE 802.11ax, allows an Access Point (AP) to communicate with multiple stations (STAs) simultaneously, the bandwidth of the Resource Unit allocated to each STA is inversely proportional to the number of STAs. In contrast, Orthogonal Frequency Division Multiplexing (OFDM) allows an AP/STA pair, determined by carrier-sense multiple access with collision avoidance, to dominate the entire bandwidth. However, the latency before packet transmission increases with the number of STAs. The number of STAs that want to communicate with an AP thus significantly impacts throughput under OFDM and OFDMA. Therefore, this study evaluates the communication performance for rich content and voice data when multiple STAs (up to five) are connected to an AP with OFDM or OFDMA by lab experiments. Through experimental results, we clarified which is more suitable, either OFDM or OFDMA, to improve the Quality of Experience (QoE) and throughput with the change in the number of STAs and application types of traffic.