Restricted Access Window Based Hidden Node Problem Mitigating Algorithm in IEEE 802.11ah Networks

Ruoyu WANG  Min LIN  

IEICE TRANSACTIONS on Communications   Vol.E101-B   No.10   pp.2162-2171
Publication Date: 2018/10/01
Publicized: 2018/03/29
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2017EBP3462
Type of Manuscript: PAPER
Category: Network
IEEE 802.11ah,  restricted access window,  RAW,  hidden-node problem,  cross-slot boundary,  

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IEEE 802.11ah is a specification being developed for sub-1GHz license-exempt operation and is intended to provide Low Power Wide Area (LPWA) communication services and support Internet of Things (IoT) features such as large-scale networks and extended transmission range. However, these features also make the 802.11ah networks highly susceptible to channel contention and hidden node problem (HNP). To address the problems, the 11ah Task Group proposed a Restricted Access Window (RAW) mechanism. It shows outstanding performance in alleviating channel contention, but its effect on solving HNP is unsatisfactory. In this paper, we propose a simple and effective hidden node grouping algorithm (HNGA) based on IEEE 802.11ah RAW. The algorithm collects hidden node information by taking advantage of the 802.11 association process and then performs two-stage uniform grouping to prevent hidden node collisions (HNCs). Performance of the proposed algorithm is evaluated in comparison with other existing schemes in a hidden node situation. The results show that our proposed algorithm eliminates most of hidden node pairs inside a RAW group with low overhead penalty, thereby improving the performance of the network. Moreover, the algorithm is immune to HNCs caused by cross slot boundary transmissions.