ndards, this is unfortunate. The Bluetooth to replace a cable, not necessarily to integrate into a net- standard is now also endorsed by the IEEE as 802.15.1. work attached to that cable. WPANs seek to replace serial To make life simple for users, the Bluetooth PAN was and parallel printer cables, universal serial bus connections, intended to operate with essentially no user configura- and simple analog cables for speakers, microphones, and tion. Thus, Bluetooth networks are based on ad hoc dis- headphones with a single wireless digital data connection. covery of neighboring devices and formation of networks. Personal areas vary from person to person and culture to Simple modulation, low transmit power, low data rate, culture but are usually much smaller than a building, SO and modest sensitivity requirements all contribute to PANs do not need to have the same range expected of a standard that can be inexpensively implemented with WLANs. The cables being replaced are generally very in- minimal power requirements. Frequency hopping was expensive, SO even more than WLANs, WPAN products used to allow multiple independent collocated networks. must be inexpensive to build and use. Many WPAN The network is based on synchronized time slots allo- products are likely to be included in portable battery- cated by the master device, SO that resources could be powered devices and should use power sparingly. provided on a regular deterministic basis for voice and In this section we discuss three differing WPAN stan- other time-sensitive traffic. dards activities, all (at least today) taking place under the The architecture of Bluetooth networks is based on aegis of the 802.15 working group of IEEE. As is often the the piconet (Figure 5.1-22). In terminology also perhaps MASTER ACTIVE SLAVES (up to 7) PARKED slaves SNIFF / HOLD slaves (up to 255) piconet Figure 5.1-22 Bluetooth piconet. Wireless local area networks CHAPTER 5. 1 2.4835 1 MHz channels 1.5 MHz 3 MHz Figure 5.1-23 Bluetooth channelization. harkening back to the tim