Recent Advances in Wireless Networking

A fter discussing advances in wired networking in a previous column (" Recent Advances in Wired Networking, " Computer , April 2000, pp. 107-109), I now turn to advances in wireless networking. Wireless networks can include everything from cellular, personal communications system (PCS), and Group System for Mobile communications (GSM) networks to wireless LANs, satellite-based networks, and fixed wireless networks. Many of these technologies have experienced significant growth lately because of an increasingly mobile workforce and accelerating user acceptance. Although voice and short messaging drove the early successes of wireless networks , data and more sophisticated applications are driving advancements today. Significant progress has also been made in middleware development and standardization. These factors—along with demand for higher bandwidth and global roaming—will continue to push the standardization and the near-future deployment of third-generation wireless networks using terrestrial and satellite components. Mobile users do not necessarily need to use wireless interfaces, and wireless interfaces do not necessarily support mobility. Therefore, mobile and wireless systems are not the same even if they overlap considerably. Mobile networks provide support for routing functions (to maintain communication with mobility) and location management functions (to keep track of the location). Wireless networks provide wireless interfaces to users (both mobile and stationary) by supporting bandwidth allocation and error-control functions. Several issues can arise when they are put together, including optimal use of low bandwidth channels, management of large bit error rates, application-level quality-of-service support , increased security concerns, and equipment failure. With 300 million worldwide in 1999, the total number of cellular and PCS subscribers is expected to reach one billion by 2004. Two percent of the US population uses a cell phone as the primary telephone access, and 10 percent of all calls in the US involve cellular, PCS, or GSM phones. Because of the roaming agreements among carriers, nationwide roaming already exists in the US. In many European countries , the use of GSM has allowed crosscountry roaming. However, the dream of global roaming hasn't yet been realized because there are too many of these incompatible standards. For example, US standards use Frequency Division Multiple Access (in Advanced Mobile Phone System, the ana-log cellular standard), Time Division Multiple Access (in PCS), and Code Division Multiple Access (IS-95), while GSM uses TDMA/FDMA over different frequencies. These differences (listed in Table 1) have made agreeing on third-generation standards a difficult task. Once the industry deploys third-generation networks …