Experimental Evaluation of Uplink Communication Performance in IEEE 802.11ax Wireless Local Area Network: OFDM vs. OFDMA

Abstract

Although Orthogonal Frequency-Division Multiple Access (OFDMA), recently adopted in IEEE 802.11ax, allows an Access Point (AP) to simultaneously communicate with multiple stations (STAs), 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 (CSMA/CA), to dominate the entire bandwidth. However, the latency before packet transmission increases with the number of STAs. In OFDMA, trigger frames (control messages) must be exchanged between an AP and an STA before uplink communication. Therefore, the overhead for control frames could affect throughput, especially in a high-density environment. This study experimentally compares OFDM and OFDMA in terms of uplink communication performance. The results are used to determine suitable environments in terms of the number of STAs and bonding width for OFDM and OFDMA.