Retransmission Number Aware Channel Access Scheme for IEEE 802.11ax Based WLAN

The IEEE 802.11ax amendment for the next generation of Wireless local area network (WLAN) provides the Orthogonal frequency division multiple access (OFDMA) mechanism. The Uplink OFDMAbased random access (UORA) supports multiple users to transmit uplink data simultaneously in different Resource units (RUs). With UORA, Access point (AP) uses trigger frame to dynamically announce eligible Random access RUs (RA-RUs) for the associated mobile stations (STAs), and a STA is allowed to select an RU to transmit when it picks an OFDMA-based random access backoff (OBO) counter no more than the number of the eligible RARUs. The UORA requires the STA with an unsuccessful transmission to double its OFDMA contention window (OCW) size for the followed retransmission, which causes the STA to endure a longer delay for retransmission(s). We propose the Retransmission number aware channel access (RNACA) scheme for IEEE 802.11ax-based WLAN. In the RNACA, a failed STA makes decision on whether to double its OCW size or not by using a probability that considers the number of retransmissions, number of RUs, and number of STAs. Simulation results show that the proposed RNACA can gain a higher throughput and a lower packet delay.