Coexistence Of Wpan_ZigBee And WiFi

IEEE 802.15.4 (ZigBee) is a kind of low rate wireless personal area network protocol. To provide the global availability, the ZigBee devices use unlicensed 2.4GHz ISM band. Because the ISM band is commonly used for the low cost radio devices such as IEEE 802.11b wireless local area network (WLAN), an unrestricted access to the ISM band exposes the ZigBee devices to a severe interference. Although WiFi and ZigBee have been designed for the different purposes, they might coexist in the proximity of each other. Since WiFi have been deployed earlier, newly deployed ZigBee devices can experience the EMC from WiFi. Therefore, the performance of ZigBee under the interference of WiFi needs to be evaluated.First part includes the introduction about IEEE 802.15.4 network topology, physical layer, MAC (Media Access Control) layer frame format, the composition of super-frame, CSMA/CA arithmetic, GTS mode, and detection mode during the start-up of PAN (Personal Area Nework).Then two kinds of physical layer spread spectrum methods are introduced. The comparision of two methods are given from the aspect of anti-interference capability, anti-multipath capability and anti-fading performance. At the mean time, the characteristic of DCF and PCF which are the MAC layer channel access mechanism, CSMA/CA protocol and RTS/CTS mechanism are introduced.In this paper, the PER of the IEEE 802.11b under the interference of the IEEE 802.15.4 is analyzed. The PER can be obtained by the BER and the collision time. The BER is obtained from the SNIR. The collision time is defined as the time that IEEE 802.15.4 packets overlap IEEE 802.11b packets. The safe distance ratio between the two systems can be obtained from the PER. This paper suggests an appropriate packet length to reduce the effect of the IEEE 802.15.4 interference and obtain a maximum throughput of the IEEE 802.11b.