I. Introduction
With the success of wireless local area networks (WLANs), the wireless networking community has been looking for new avenues to enable wireless connectivity to existing and new applications [6]. The emerging of short-transmission-range wireless devices with low transmission rates further boosts the development of wireless personal area networks (WPANs), where a WPAN is a wireless network centered around an individual person's workspace for device inter-connection. Among the well-known WPAN specifications, ultra wideband (i.e., IEEE 802.15.3) is designed for high-rate WPANs [2]. Bluetooth (i.e., IEEE 802.15.1) supports various applications, such as wireless headsets of home appliances and computer peripherals, and provides quality of service (QoS) transmissions, especially for audio traffics [16]. As low cost and low-power consumption are considered, ZigBee (i.e., IEEE 802.15.4) emerges as a good alternative for WPANS [3].