2.5G service deployments gather momentum

By Lisa Pierce
Network World, 02/04/02

Despite the marketing rhetoric around 3G, all major U.S. wireless service providers are in the process of deploying 2.5G mobile data networks.

I appreciate their reasoning - 2.5G data speeds are two to three times faster than 2G under real-life conditions.

All nonproprietary services already introduced in other parts of the world and being deployed in the U.S. now are part of the long-term movement by wireless services providers away from circuit-switched technology (1G and 2G services) toward packet-switched technology to support voice and data services (3G). Because 3G packetizes voice and data, it requires much faster bandwidth than can be supported by the services being introduced now. The International Telecommunications Union requires that 3G services deliver 2M bit/sec to a mobile device while stationary. In contrast, the maximum bandwidth supported by 2.5G Code Division Multiple Access (CDMA)-based 1xrtt service to a stationary device is 153K bit/sec.

Similarly, GSM-based 2.5G Global Package Radio Service (GPRS) tops out at 115K bit/sec. But both the GSM and CDMA versions of these technologies also support upgrades and overlays to support bandwidths between 2.5G services and 3G services. Bandwidth for Enhanced Data for GSM Evolution and CDMA-based 3xrtt services top out about at 512K bit/sec.

However, users should have modest expectations regarding phase one 2.5G throughput because the bandwidth experienced with these services under real-life conditions is significantly lower than the maximum. Although 1xrtt devices can support the maximum speed, the experienced bandwidth while stationary is less than half - currently averaging between 40K bit/sec and 64K bit/sec under real-life conditions. The peak speed of current generation GSM-based 2.5G devices is even less - about 25% of peak bandwidth. Relative bandwidth also degrades as the distance between a mobile device and transmitter increases. Application performance can be improved with the use of compression, but depending on the requirements of the application, may compensate only partially for the lack of higher bandwidth.

Various U.S. providers have different service introduction plans. Looking at those that currently have double-digit 2G market share, Verizon Wireless introduced its 1xrtt service last week and made it immediately available to about 20% of its network footprint.

Its plans are quite aggressive, as the company's CTO says he wants to have 1xrtt service deployed to 100% of its combined digital and analog footprint before the end of next year. Sprint PCS had intended to make 1xrtt service available to a limited number of serving areas by the end of last year, but now says it will make it available to 100% of its base this summer. AT&T Wireless began introducing GPRS last July and has deployed it in 20 U.S. states to date. It has gone on record on many occasions that it intends to get 2.5G service deployed to 100% of its digital base by year-end. And Cingular is deploying GPRS in Puerto Rico, its initial market, right now.

When considering current 2.5G services and future enhancements, important issues include service availability, device throughput, security, application design and price. With their introduction by multiple providers, companies finally can begin to evaluate their applicability and value to their businesses.

Whatever they may be called by providers, these services are indeed a welcome arrival in the U.S.