{'fraction_non_alphanumeric': 0.02596439169139466, 'fraction_numerical': 0.01112759643916914, 'mean_word_length': 5.104072398190045, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Scheduling Channel Access Based on Target Wake Time Mechanism in 802.11ax WLANs

Trend of dense deployment of 802.11 WLANs makes it urgent to design effective and efficient channel access schemes. IEEE 802.11ax standard for the next generation WLAN introduces the orthogonal frequency division multiple access (OFDMA) mechanism that supports downlink and uplink multi-user transmissions over multiple resource units (RUs). In this paper, we, integrating the multi-user transmissions with the target wake time (TWT) mechanism, propose the Scheduling Channel Access with TWT (SCAT) scheme. The SCAT wakes up stations (STAs) no more than the number of RUs in each target beacon so that the channel can be accessed on schedule without contention. Additionally, we develop a mathematical model to derive the throughput and delay arising from sleeping (DAFS) under the SCAT, which are used to formulate the throughput maximization problem (TMP) subject to delay constraint. Then, the TMP is solved by the genetic algorithm in which a tree is chosen as a chromosome. The solution to the TMP enables the SCAT to assign the optimal listen intervals and the next target beacons to the STAs so that the maximum throughput is achieved. Simulation results show the SCAT outperforms the existing schemes in throughput, channel utilization, and energy efficiency.