Low-cost and high performance wireless technologies make it a reality to develop a wireless HVAC control system for multi-zone environmental control in residential houses to improve individual comfort and reduce energy consumption. The lack of understanding on signal transmission performance of wireless sensor network in residential houses limited the application of wireless sensor networks, especially the new ZigBee protocol. This paper is to establish path loss models for predicting wireless data transmission performance in residential houses for ZigBee protocol. Factors affecting the wireless data transmission in residential indoor environment include free space separation, walls, floors, and wireless device inteference. Effects of these factors on the path loss in residential indoor environment were evaluated through empirical testing using received signal strength indicator (RSSI) value measured by commercial ZigBee modules and an embedded microcontroller-based data acquisition system. The model for the effects of walls on the same floor was able to predict 73.6% of the system variability. The measured RSSI data were made versus 1mW transmission source and therefore the RSSI-based path loss models were able to accurately predict the performance of wireless signal of stronger or weaker power transmission systems.
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