With a typical range of less than 10 meters, wireless personal area networks (WPANs) have become the popular choice for hands-free access to mobile handsets as well as linking desktop peripherals and personal devices, such as PDAs and smartphones.
The next-generation of WPANs that are in development aim to significantly boost performance, increasing data rates, for example, in order to accommodate streaming video. For these next-generation WPANs, the specifications of note will be throughput, power consumption, and interference.
Characterized by low power consumption and high throughput, which is unaffected by nearby wireless systems operating in band, WiMediai ultrawideband (UWB) technology is a good fit for next-generation WPANs.
WPANs and WLANs
It is important to distinguish WPANs from wireless local area networks (WLANs) as these two technologies are separately defined and governed by different technical specifications, standards, and industry alliances. For instance, WPAN standards have been developed by the IEEE 802.15 working group.ii The Bluetooth SIGiii and the USB-IFiv are the industry organizations that promote WPAN technologies, such as Bluetooth and Certified Wireless USB (C-WUSB).
WLAN standards, on the other hand, have been developed by the IEEE 802.11 working group,v and the WiFi Alliancevi is the industry consortium with the mission to drive the adoption of a single worldwide-accepted standard for high-speed WLAN.
Typically, WLANs require long range while WPANs require higher throughput and lower power. Figure 1 lays out the range and data rate requirements typically associated with WPANs and WLANs.
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Figure 1: WLANs and WPANs differ in terms of data rates and range.
Boosting data rates
New functionalities and storage capabilities are regularly being added to portable devices, which is driving the need for faster wireless connectivity. In response, next-generation WPANs (such as Bluetooth's Seattle Release) need to increase data rates. The main application for new WPANs is file transfer, but streaming video is emerging as an interesting application.
In order to provide a good user experience, streaming video requires fairly long periods of high bandwidth consumption. Any compromise on throughput or bandwidth would likely make this new application unusable. The maximum throughput required for compressed video is shown in the following table:
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Table 1: Max throughput for H.264 high 4:2:2 and high 4:4:4 Predictive Profiles at 30 frames per sec (Source: WiMedia).
The required throughput is dependent on content type. For example, a sporting event requires higher throughput than a typical television program, because of sports' fast changing images. The wireless system needs to support the maximum required throughput, however, because of the varying needs of different types of video, the requirements for file transfer can be relaxed.
For example, average file transfer requirements for HDTV are 5 to 6Mbpsvii. This means that a system capable of supporting 80Mbps will be able to transfer a file containing a two hour movie in only nine minutes; this is certainly a highly desirable feature for consumers.