Abstract
IEEE 802.11ax Wireless Local Area Networks (WLANs) introduce Orthogonal Frequency Division Multiple Access (OFDMA) physical layer technology to improve throughput in dense scenarios. In order to save power of battery operated stations (STAs), a novel broadcast Target Wake Time (TWT) operation for negotiating wake time between an access point (AP) and a group of STAs is also proposed by making full use of the new capability of uplink OFDMA-based multiuser transmissions. However, if the wake time of each STA which is determined by the offset and wake interval (listen interval) is not properly scheduled, deteriorated throughput and high power consumption occur because of collisions. In this paper, we take the advantage of uplink multiuser transmission with the novel TWT scheduling to maximize throughput. We first investigate the fundamental relationship between throughput and energy efficiency with several key aspects, such as the number of simultaneously active STAs, the number of eligible random access resource units, and the contention window size. We further derive the formulations of throughput and energy efficiency on the listen interval of each STA. Based on the relationship, a TWT-based sleep/wake-up scheduling scheme (TSS) is proposed to improve the throughput by reducing or even cancelling collisions. Simulation results demonstrate the effectiveness in terms of average throughput and energy efficiency. The TSS also makes a practical step towards a collision-free and deterministic access in future WLANs when cooperating with TWT service period scheduling.
Highlights
Wireless Local Area Networks (WLANs) based on IEEE 802.11 standards [1] have become one of the most popular solutions for wireless internet accessing because of their mobility, flexibility of deployment, and cost efficiency as wireless access requirements increase [2], [3]
The STAs are usually equipped with power limited batteries to support mobility and portability, and they can power down the transceivers to save power which is called power save mode (PSM), otherwise they will consume a substantial portion of available power [9], [10]
Considering the new technologies introduced in IEEE 802.11ax, we have investigated the broadcast Target Wake Time (TWT) operation with Orthogonal Frequency Division Multiple Access (OFDMA) based multiuser transmission
Summary
Wireless Local Area Networks (WLANs) based on IEEE 802.11 standards [1] have become one of the most popular solutions for wireless internet accessing because of their mobility, flexibility of deployment, and cost efficiency as wireless access requirements increase [2], [3]. Transmissions now is introduced in IEEE 802.11ax It keeps STAs staying in PSM for a long time to save power by negotiating wake periods. In order to achieve higher throughput and efficient power consumption in infrastructure basic service sets (IBSSs), we propose a TWT based sleep/wake-up scheduling scheme (TSS) which takes the OFDMA based MU transmission capability into consideration by minimizing contention between STAs in each beacon slot. In the TSS, the AP is able to negotiate tuples by tending to use adaptive LIs according to network density and the number of available RA-RU and avoiding alignment of first TBTTs. Aiming at an efficient media access, the TSS equalizes the number of simultaneously active STAs and alleviates average contention in each beacon slot.
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