Priority-Considered Channel Access for Registration-Backoff-Time (RBT) -based IEEE 802.11ah IOT Network

This work devises a High Priority Reservation - centric Registered Backoff Time -based (HPR-RBT) channel access method to enhance the performance of IEEE 802.11ah IoT network. The proposed HPR-RBT method allows the STAs that have high priority’s uplinked data to reserve, which is through the claiming action, the privilege of channel access. HPR-RBT adopts the Trigger RAW mode of IEEE 802.11ah and the RBT mechanism. In HPR-RBT, the Restricted Access Window (RAW) of IEEE 802.11ah is divided into (1) a claiming RAW that contains multiple claiming slots and (2) a data RAW that contains multiple data slots. Each claiming slot is further divided into many tiny slots, each of which is for one STA to claim its channel access’s reservation for its high priority’s uplinked data. Each data slot is further divided into a scheduled sub-slot, in which the channel access of the high priority’s uplinked data is scheduled, and an unscheduled sub-slot, in which the channel access of the regular priority’s uplinked data is allowed. Furthermore, this work proposes a grouping mechanism to balance the load of high priority’s uplinked data across RAW’s data slots to prevent excessive high priority’s uplinked data in any particular RAW’s data slot. Through the grouping mechanism, the IEEE 802.11ah Access Point (AP) can assign the data slot that has the lowest load of high priority’s uplinked data to a newly associated STA of the AP. Comparing with the legacy 802.11ah method, the experiment result shows that the proposed HPR-RBT method has (i) the shorter transmission latency and (ii) the better throughput when the number of STA becomes bigger.