Scheduled Rendezvous and RFID Wakeup in Embedded Wireless Networks

Scheduled rendezvous is a common technique for reducing power consumption in embedded wireless networks [1] [2]. In scheduled rendezvous, nodes remain in a low power sleep mode whenever possible and periodically awaken to rendezvous with other nodes. Unfortunately, in many embedded wireless systems node power consumption may be unnecessarily dominated by this rendezvous activity [3]. In this paper we study the use of radio frequency identification (RFID) technology, as a low power wakeup mechanism for embedded radio networks. RFID radios are very low cost and can currently be operated at power consumptions of over three orders of magnitude lower than that of typical commercial radios operating in the Mbps range [4]. We first compare the regions of operation where RFID wakeup and scheduled rendezvous are preferred. A protocol is proposed which allows the basestation to block transmissions that may interfere with the wakeup process. In addition, a hybrid low power rendezvous wakeup protocol is proposed which attains very low power consumption. We find that in low utilization situations where a high level of responsiveness is needed, low power wakeup can achieve much lower levels of power consumption than scheduled rendezvous. The results also suggest that adaptive schemes are possible where the mode used is selected dynamically by the basestation.