Coexistence performance model for a large ZigBee lighting sensor network in the 2.4 GHz ISM band

A ZigBee (802.15.4) lighting network is potentially vulnerable to interference by other wireless technologies that operate in the same Industrial, Scientific and Medical (ISM) frequency band, such as Wi-Fi (802.11). In order to minimize the effect of external interference, nodes can dynamically adapt radio parameters, based on monitoring information about the current spectrum usage and relevant performance metrics. In this work, we provide an accurate model to evaluate the performance of a ZigBee lighting network with multiple nodes under the effect of combined interference (external interference, for example from Wi-Fi, and contention within the ZigBee network itself). The proposed model takes into consideration the ZigBee network size, the back off process and packet re-transmission attempts in the CSMA/CA mechanism, to provide performance metrics given the Wi-Fi interference pattern. We quantify external interference based on a Markov chain model. A detailed analytical model enables interference aware communication protocols to dynamically adjust the protocol parameters in order to achieve the required quality of service.