Enabling globally unique sensor ID with dual-interface RF tag

In any sensor information system, unique identification (ID) of each sensor is indispensable. Usual practices to secure uniqueness of sensor ID is to use MAC or network address or to use a proprietary ID in application layer. In pervasive computing era, it is desirable to uniquely identify a sensor with a URN regardless of types of network to which the sensor is connected. This paper proposes to embed a dual interface RF tag, which records a globally unique ID, EPC (Electronic Product Code), used in business transactions, to sensor microcontroller(MCU). The dual interface RF tag allows us to access its tag data either via RF interface and a baseband interface. This enables a sensor MCU to use EPC to uniquely identify the sensor for its whole product lifecycle. Since EPC have been only accessed through the RF interface, we developed a modified UPnP to automatically discover EPC enabled sensors through the baseband interface for various access networks. Taking advantage of the existing network RFID architecture, we can search services related to an EPC in a form of URL and also can publish and subscribe sensor data service with a standardized web service interface. This paper reports a hardware implementation of dual interface RF tag with a ZigBee transceiver. Timing requirement of RFID protocol to access RF tag's memory can be met by a software control of off-the-shelf MCU GPIO. A 96 bits EPC stored in an dual interface RF tag can be retrieved in 12.3 msec. For the automatic device discovery of an EPC enabled sensor attached to a ZigBee network, a modified UPnP is also developed. The proposal is implemented in a working prototype with 49 sensors which geographically dispersed in 3 locations which can continuously collect 181 sensor data for various applications. We also evaluated the minimum time interval to publish sensor data to find 300 msec is the shortest interval in our implementation. This interval is dominated by the communications capacity between sensor MCU and on-board transceiver chip.