CII: A Light-Weight Mechanism for ZigBee Performance Assurance under WiFi Interference

Recently, the low-power, low-cost and reliable ZigBee technology have received significant research attention with the increasing popularity of applications such as smart home system, patient monitor in hospitals. Coexisiting with the WiFi devices on the crowded unlicensed ISM band, such as hotspots and mobile phones, ZigBee will receive significant performance influence. The throughput and Packet Reception Rate (PRR) of ZigBee will decrease with the increasing number of WiFi devices. Because of the incompatible PHY/MAC layer, ZigBee devices will suffer near 50% packet loss when coexisting with WiFi devices. The existing mechanism such as CSMA/CA is surprisingly inadequate for solving this problem. As the WiFi traffic typically appears bursty, the channel will be free for more than 60% of the time. In this paper, we propose a new metric called channel idle indicator (CII) which can quantify the channel quality. Based on the CII and logistic regression, we build a channel idle state prediction model which can help ZigBee devices to use the white space of WiFi channel efficiently. Particularly, our approach is light-weight, which can be easily implemented on the ability-limited commercial off-the-shelf (COTS) ZigBee devices. Extensive experiments show that our scheme can achieve over 91% of the PRR, which is near 40% higher than the B-MAC protocol. When the WiFi throughput is 3Mbps, our scheme achieves near 1.5x throughput over B-MAC. Carrying on further, our scheme consumes less energy via degrading packet loss rate in the energy consumption part.