Space-Frequency Diversity based MAC protocol for IEEE 802.11 ah networks

IEEE 802.11ah is a sub-GHz communication technology to offer longer range and low power connectivity for the Internet of Things (IoT) applications. A Restricted Access Window (RAW) is specified to decrease the collision probability. Stations are divided into groups and stations from each group attempt to access the channel by employing the Distributed Coordination Function during their assigned RAW slots. However, the network throughput is limited by a single channel MAC protocol. In this paper, Space-Frequency Diversity-based MAC protocol for the IEEE 802.11ah network (SF-MAC protocol) is proposed to allow stations of different sectors to transmit packets on different channels with the help of Forwarders. The proposed SF-MAC protocol improves the packet delivery ratio and aggregate throughput of the network.

I. Introduction

IEEE 802.11 ah [1], marketed as WiFi Halow, provides network connectivity up to 8192 stations from 150 kbps to 78 Mbps over a transmission range up to 1 km. IEEE 802.11 ah operates in unlicensed sub-GHz frequency bands, i.e. 863–868 MHz in Europe, 755–787 MHz in China, and 902–928 MHz in North America (Fig. 1). It features fast association and authen-tication, restricted access window (RAW), traffic indication map (TIM), and target wakeup time (TWT) to provide access service to a large number of stations, energy efficiency, and extended network coverage.