On ZigBee coexistence in the ISM band: Measurements and simulations

Wireless Sensor Network (WSN) technology enables design and implementation of novel applications that can be used to address numerous industrial, environmental, social and economical challenges. The IEEE 802.15.4 standard specifies WSN as a personal unlicensed network that operates in the Industrial, Scientific and Medical (ISM) unlicensed band. Unfortunately, this band is also available for many other wireless technologies like Bluetooth/ IEEE 802.15.1 and Wireless Local Area Networks (WLANs)/IEEE 802.11b/g. The blind coexistence between wireless technologies in the ISM band can lead to severe performance degradation due to undesired interference. This paper provides an overview on the performance of ZigBee WSNs/IEEE 802.15.4 coexisting with IEEE 802.11b/g WLANs. Through extensive measurements for packet error rate (PER), link quality indication (LQI) and received signal strength indication (RSSI) performance metrics, we were able to clarify the performance degradation due to the blind coexistence between IEEE 802.15.4 and IEEE 802.11b/g networks. We support the measurement results by extensive simulations using OPNET V.16 for large scale ZigBee WSNs coexisting with WLANs. We show that for robust operation in unlicensed bands, WSNs should be equipped with cognitive radio capability.