NBP: light-weight Narrow Band Protection for ZigBee and Wi-Fi coexistence

Abstract

The recent development of various wireless technologies in the 2.4GHz ISM band has led to the co-channel coexistence of heterogeneous wireless devices, such as Wi-Fi, Bluetooth, and ZigBee. This sharing of the common channel results in the challenging problem of cross-technology interference, since the wireless devices generally use diverse PHY/MAC specifications. In particular, the less capable ZigBee device may often experience unpredictably low throughput due to the interference from the powerful Wi-Fi. The ZigBee protector is an attractive solution, since it can reserve the channel on behalf of the weak ZigBee devices. The protector method, however, has a few limitations; (i) it may cause significant overhead to both ZigBee and Wi-Fi, and (ii) the ZigBee control packets are still vulnerable to the Wi-Fi interference. In this paper, we propose a novel time reservation scheme called Narrow Band Protection (NBP), that uses a protector to guard the ongoing ZigBee transmission. The key contributions are threefold: First, NBP autonomously detects any ongoing ZigBee transmissions by cross-correlating the ZigBee's packets with the pre-defined Pseudo-random Noise (PN) sequences. By using this cross-correlation, it significantly reduces the control overhead. Second, due to the reliable cross-correlation, NBP is robust from the control packet collisions, which typically wastes channel time for both ZigBee and Wi-Fi. Third, NBP protects the burst of ZigBee packets by estimating the size of the burst, in turn, giving a semantic to the PN codebook. This is important because ZigBee is typically battery-powered and thus the long burst is advantageous for the low duty cycle operations. We first show the feasibility of NBP by implementing it on the real USRP/GNURadio platform. Then, we evaluate the performance of NBP through mathematical analysis and NS-2 simulations. The results show that NBP enhances the ZigBee throughput by up to 1.77x compared to the existing scheme.