The Enhancement of B-MAC Protocol to Minimize Coexistence Interference Between ZigBee and Wi-Fi in Dynamic Environment

ZigBee is one of Low Rate Wireless Personal Area Network (LR-WPAN) is a wireless protocol that targeted on toward automation, real-time monitoring and remote control applications. ZigBee protocol goal is to provide reliable communication with low-cost, low power consumption, simple implementation for low-data rate monitoring applications. ZigBee implemented hardware is deployed in a large-scale number of sensor nodes to track and monitor the physical environments and also to collect variety of data to process the data locally and to deliver the information over a multi-hop link. However, ZigBee-based devices suffered from coexistence interference problem when deployed in area crowded with another network. ZigBee normally got heavy interference from Wi-Fi (IEEE 802.11) network due to its high transmission power that can greatly affect ZigBee devices transmission performance. This event was called coexistence interference when two different wireless technology had overlapped channel. The coexistence interference issue was very critical for ZigBee devices when implemented in applications where real time information delivery was required. Therefore, the aim of this thesis is to minimize the coexistence interference effect between ZigBee and Wi-Fi (IEEE 802.11) technology by improving the existing ZigBee Carrier Sense Multiple Access / Collision Avoidance (CSMA-CA) protocol by reducing the back-off period range. Thus, reduced period based on reduction percentage which is between 5% to 50%. The reduction percentage is selected based on the Channel Congestion Indicator (CCI) value which measured from Clear Channel Assessment (CCA) fail counts. The CCI is used to indicate congestion level in current channel and also used in decision making for assigning reduction percentage that grouped from range 10% to 100% that selected randomly by the CSMA-CA protocol. This allows the CSMA-CA protocol to randomly select back-off period within reduced range that generate lower delay. Its allows ZigBee radio module to reassess the channel as fast as possible with minimum number of packet loss. Moreover, number of packet loss can be minimized when the back-off period range reduced. It can increase accuracy of radio module to select back-off period that match the timing of securing channel during lowest channel utilization at that time. Thus, radio module can start sending packet during the channel is not utilized by Wi-Fi and reduce chance of packet collision between ZigBee and Wi-Fi. By reducing the back-off period range, it decreases the overall average round trip time by 52.81% and overall packet loss by 57.83%. By minimizing the effect of Wi-Fi interference, its improve the ZigBee transmission reliability which critically required for developing reliable applications for real-time