WANs, LANs, and PANs
One way to segment wireless communication technologies is by the geographic area that they cover. A common approach is to partition technologies into wide-area, local-area, and personal-area networks (or WANs, LANs, and PANs, respectively).
The coverage of a WAN is typically measured in kilometers, or at least in hundreds of meters. Communication over such distances requires relatively high-power transmissions, so it requires a license to a specific frequency band. Typically, carriers pay a fee for a license to transmit at certain power levels in a particular frequency spectrum. High-power transmission also leads to tradeoffs between power consumption and data rates in wireless WANs. Typical data rates for today's cellular networks are relatively slow, owing largely to the transmission power necessary to reach the cellular tower from a handset. Significantly faster data rates at these same levels of power transmission are impractical with today's battery technologies.
In our book, Bluetooth Revealed, my coauthor, Chatschik Bisdikian, and I observe that third-generation, or 3G, cellular systems will have significantly faster data rates. However, to maintain power consumption at reasonable levels, 3G systems will require cellular towers to be much closer togetheron the order of hundreds of metersapproaching the coverage of WLANs (discussed next). WWAN technologies include those in common use for cellular communications, such as GSM, TDMA, CDMA, and others.
WLANs typically cover distances of 10 to a few hundred meters. This smaller coverage distance allows lower power transmissions that in turn often permit the use of unlicensed frequency bands. Because LANs often are used for relatively high-capacity data communications, they often have fairly high data rates. IEEE 802.11, for example, has a nominal range of 100 meters and data rates up to 11Mbps. This combination of coverage and data rate leads to moderate-to-high power consumption; thus, the types of devices usually used with WLANs are ones that have a robust computing platform and power supply; notebook computers, in particular.
WPANs cover distances on the order of 10 meters, and typically are used to connect various personal portable devices without using cables. This peer-to-peer device communication doesn't usually require exceedingly fast data rates. Bluetooth wireless technology, for example, has a nominal range of 10 meters with raw data rates up to 1Mbps. The short range and relatively low data rates result in low power consumption, making WPAN technologies suitable for use with small, mobile, battery-powered devices such as PDAs, mobile phones, pagers, digital cameras, and so on. In addition, low-power transmission allows for the use of unlicensed frequency bands. Bluetooth technology operates in the unlicensed 2.4GHz spectrum.
Figure 1 illustrates these characteristics of WWANs, WLANs, and WPANs.
Figure 1 WWANs, WLANs, and WPANs compared.