An Efficient Backoff Procedure for IEEE 802.11ax Uplink OFDMA-Based Random Access

Abstract

IEEE 802.11ax stations can use multi-user (MU) uplink OFDMA-based random access (UORA) to improve per-station throughput in dense deployments in comparison to legacy IEEE 802.11 single-user access. Unfortunately, UORA suffers from a high collision probability and low efficiency under high contention. In this paper, we address this problem by modifying the UORA backoff selection method. The proposed solution allows an access point to adjust the OFDMA random access backoff (OBO) countdown rate to decrease the probability of uplink transmission failures. The implemented changes considerably improve UORA performance. We show through extensive simulations, that the proposed efficient OFDMA random access backoff (E-OBO) ensures throughput, efficiency, and collision probability close to optimal and outperforms state-of-the-art solutions.INDEX TERMS IEEE 802.11ax, uplink OFDMA random access, UORA, efficiency.

Wi-Fi Meets ML: A Survey on Improving IEEE 802.11 Performance With Machine Learning

“…For OFDMA, in the case of AP-initiated transmissions, either in downlink or uplink, the AP must determine the group of stations scheduled at each TXOP, and which is the best RU allocation to them. Alternatively, in the case of uplink transmissions, stations may be allowed to select the RU that they will use for transmission [172]. These problems are considered using DRL techniques [138], [140], [141].…”

Improving IEEE 802.11ax UORA Performance: Comparison of Reinforcement Learning and Heuristic Approaches

“…Recently, we proposed an UORA improvement called efficient OBO (E-OBO), which exhibits good performance [2]. We briefly explain the operation of E-OBO in this section to compare it later with RL-OBO in Section V-F.…”

“…Stations can transmit simultaneously, which improves efficiency compared to singleuser transmissions. OFDMA has two modes of operation: scheduled access (SA) [1] and random access (RA) [2]. In the former, all decisions are made centrally at the 802.11ax AP.…”

“…The OCW range can be configured by the AP in the UORA parameter set element, distributed through beacon frames. Unfortunately, this basic operation (which we refer to as legacy UORA) is highly inefficient under saturation [2].…”

“…Table 1). The efficiency of UORA can be improved by adaptive grouping [6], [7], spatial clustering [8], sub- channel hopping [9], complementary probability instead of backoff [10], additional carrier sensing [11], retransmission awareness [12], OBO modifications [2], [13], grouping-based channel access [14], and considering adjacent channel interference [15] 1 . None of the above research uses ML methods, although the application of reinforcement learning (RL) to improve UORA operation is suggested as future work by Kim et al [13].…”