A Novel Grouping Mechanism for Performance Enhancement of Sub-1 GHz Wireless Networks

IEEE 802.11ah is a new wireless LAN technology proposed mainly for IoT (Internet of Things). Operating at frequency band under 1 GHz, 802.11ah WLAN can provide much extended coverage range and support around 8,000 nodes to be associated with a single AP. Such a dense environment may cause hidden terminal problems which can severely degrade the performance of the network. Thus, the 802.11ah standard adopts a group based MAC protocol such that the nodes are divided randomly into several groups and members of a group contend to access channel within their allocated RAWs (Restricted Access Windows). However, the random grouping method cannot solve the hidden terminal problem sufficiently. In this paper, we propose a novel grouping mechanism that groups the nodes by their hidden-terminal relationship: i.e., any two nodes hidden to each other are assigned to different groups, and thus access the channel using different RAWs. Mathematic analysis and simulations show that our proposed scheme remarkably improve the performance of Sub-1 GHz WLAN.