Design and Development of Novel Performance Improvement Techniques for ZigBee Packet Transmission Under Wi-Fi Interference

ZigBee based Wireless Sensor Networks (WSN) and Wireless Local Area Networks (WLAN) utilize the same un-licensed 2.4GHz frequency band. In our research, it is noticed that ZigBee could suffer serious performance degradation due to the collocated WLAN interference. After going through the available literature and combining with a thorough statistical analysis of our experimental results, several important factors that severely impact the ZigBee packet transmission performance have been identified. Motivated by these findings, novel techniques are designed to improve the performance of ZigBee packet transmission under WLAN interference. ACK with Interference Detection (ACK-ID) technique is developed to improve the delivery rate of ACK packets, and consequently reduce the number of redundant retransmissions. In order to improve the energy efficiency, Adaptive Transmit Power Adjustment (ATPA) is proposed to adaptively adjust the optimal transmit power while maintaining the predefined Packet Loss Rate (PLR) requirement. Time Aware Backoff and Transmission (TABTx) technique controls the time spent on each packet transmission attempt so as to avoid the Transmit First In First Out Byte Register (TXFIFO) overflow. Adaptive Preamble Padding with Retransmission Control (APPRC) is proposed to improve the transmission efficiency while satisfying the PLR requirement by determining the appropriate number of protective preamble padding bytes and whether or not to adopt packet retransmission. All these novel techniques have been implemented in the Crossbow MICAz motes and evaluated through extensive experimental measurements in the testbed