15 WMANs, WLANs, and WPANs RFID Tag Antenna Reader Computer System Figure 15.8 An example of an RFID system 4. When an RFID tag receives a query, it responds by transmitting its unique ID code and other data back to the reader. The data transmitted from the tags can provide identification or location information about the object or specifics such as date of purchase or price. 5. The reader receives the tag responses and processes them accordingly, send- ing the information to a host computer or external devices through its con- trol lines. No contact or even line of sight is needed to read data from a product that con- tains an RFID tag. RFID technology works in rain, snow, and other environments where barcode or optical scanning technology is useless. RFID Tags Different types of RFID tags address different applications requirements: Read-only-A read-only tag is preprogrammed with a unique identification. Read/write-A read/write tag is used for applications that require data to be stored in the tag SO the information can be dynamically updated. Write once, read many times (WORM)-WORM tags allow for an ID number to be written to the tag once, and it can't be changed, but the infor- mation can be read many times. In addition, RFID tags can be either active or passive. Active RFID tags must have a power source but have longer ranges of operation and larger memories than passive tags, providing the ability to store additional information sent by reader. Active tags, about the size of a dime and designed for communications up to 100 feet (30 m) from the RFID reader, are powered by a battery and are always WPANs on. They are larger and more expensive than passive RFID tags but can hold more data about the tagged object and are commonly used for high-value asset tracking. Active RFID tags can be read/write. Many active tags have practical ranges of tens of meters and a battery life of up to 10 years. One of the most common applications for active tags is in the transportation sector (e.g., for highway tolls). Passive R