3.1 Introduction

A WPAN is a networked collection of devices situated within a short range (10 meters is often a reference radius) [1 118]. The attribute "personal" stems from the fact that this collection of devices presumably belongs to an individual, forming his or her WPAN. Thus, the WPAN forms a wireless "bubble" around the person, referred to as the personal operating space (POS). Besides the connection among the personal devices that form the bubble, the WPAN should provide the user with a seamless, ad hoc connection to the compatible resources and APs that enter her POS. The WPAN bubble can expand and contract dynamically, depending on need; it may connect to the wall repeaters to access to the Internet or it can be dynamically stretched to include access to sensors and actuators.

The main design objectives of WPAN technology are low power consumption, operation in the unlicensed spectrum, low cost, and small package size. Low power consumption is a critical issue since the rate at which battery performance improves is fairly slow, compared to the explosive overall growth in wireless communications. Therefore, the wireless protocol itself should employ economic usage of battery energy. The WPAN systems use license-free wireless links because this is the only way to achieve ubiquitous connectivity without adverse impact on an existing wireless infrastructure. Finally, the low-cost single-chip solution sets the economic and ergonomic conditions for the wide spread of the WPAN technology.