 different regions of the world, related primarily to power and bandwidth. In North America, the FCC limits the reader antenna power to 3 watts, while European regulations allow for 4 watts. HF is also the basis of numerous standards, such as ISO 14443, 15693, and 18000-3. With HF, the signal travels well through most materials, including liquid and body tissue. However, it is more affected by surrounding metals than LF. In com- parison to LF, the benefits of HF are lower tag costs, better communication speed, and the ability to read multiple tags at once. The higher the frequency, the higher the data throughput and the faster the communications between the tags and the reader, and at HF, a reader can read up to 50 tags per second. The increase in speed also allows for the reader to communicate with multiple tags at the same time. HF RFID tags are used in book tracking for libraries and bookstores, pallet tracking, building access control, airline baggage tracking, apparel item tracking, and identification badges. UHF RFID Whereas HF and LF work fairly well in the presence of liquids, today's UHF systems do not work in such environments. Metal poses a serious Chapter 15 WMANs, WLANs, and WPANs challenge for any RFID implementation, but especially in the UHF range. More- over, the longer read distance of UHF is a disadvantage in applications such as banking and access control. However, its high data throughput facilitates higher read rates, with 800 reads per second possible in theory, although 200 reads per second is closer to reality. UHF RFID tags are commonly used commercially to track pallets and containers as well as trucks and trailers in shipping yards, and UHF vendors are targeting the supply-chain market, where longer read distances are required. UHF tags can be used globally when they are specially tailored according to regional regulations because there are no globally unified regulations for radio fre- quencies in this ISM band range. However, one of the biggest challenges that has impeded the widespr