Research On Interference-aware MAC Protocols In Heterogeneous Wireless Sensor Networks

The coexistence of heterogeneous wireless networks has long been a problem especially with the explosive development of wireless networks in recent years.In Wireless sensor networks,ZigBee based on IEEE 802.15.4 get widely used with the superior characteristic of low-cost,low energy consumption and high reliability.These heterogeneous,such as Wi-Fi,ZigBee and Bluetooth operating in the crowded 2.4GHz ISM band,have to compete with each other for scarce spectrum resources,generating cross-technology interference(CTI)inevitably.Nearly ubiquitous Wi-Fi based on IEEE 802.11 has been regarded as enormous threat to ZigBee in terms of data integrity,timeliness and network reliability.Spectrum sharing among the same network of devices can be arbitrated by MAC protocols,but the coexistence between heterogeneous networks will severely degrade the effectiveness of traditional MAC due to their disparate power levels,asynchronous time slots,and incompatible PHY layers and communication mechanism.Based on the pre-analysis of such coexistence of ZigBee-Wi-Fi,first,we find the distribution of Wi-Fi traffic has the obvious characteristic of heavy tail,the channel idle state can be up to 60% during its life period.Motivated by the observation,in this paper,we will help ZigBee device to guarantee its data integrity,timeliness and especially the real-time transmission of emergency message by taking full advantage of the channel idle time without modification of Wi-Fi devices and normal activities.Second,we propose a new metric called channel idle state indicator(CISI)to quantify current channel quality.Third,based on CISI and the pre-analysis,we build a channel state prediction model and Adaptive packet delivery algorithm(APD)to enhance the channel utilization of ZigBee by adjusting its packet rate.Besides,APD is a software-level and lightweight algorithm which can be easily to existing legacy wireless sensor networks without any modification on the hardware devices of coexisted system.Extensive experimental results show that,under the coverage of different Wi-Fi traffic,our lightweight mechanism can achieve 4x and 1.5x performance gains over WISE and CII.Particularly,when Wi-Fi traffic is 4Mbps,we can still obtain over 90%.Furthermore,the energy consumption efficiency can be improved markedly with compared protocols.