In Depth: 3G Wireless Networks
By Leora Harling and Liz Garone
(8/31/00) As wireless digital communications have taken off during the last five years, carriers have filled the bandwidth available for digital technology with a complement of incompatible standards--CDMA, GSM, and TDMA.
This means that users must buy phones that work with a specific standard, and often can't change carriers easily. What's worse, these protocols carry data at speeds of up to only 19.2 kbps, far too slow for the rich media applications of today, let alone tomorrow.
Fortunately, the third generation of wireless communications (the first was analog cellular, the second the existing digital standards), has been in development in research labs around the world since the early '90s.
Although there are at least 10 3G standards under consideration by international standards bodies, the one most likely to succeed is built on a combination of EDGE (Enhanced Data Rates for Global Evolution) technology and GSM and TDMA. With 150 million cellular service subscribers using it in Europe, Asia, and the rest of the world, GSM (Groupe Speciale Mobile, or Global System for Mobile Communications) is the world's most widely used standard. TDMA (Time Division Multiple Access) comes in second, with more than 11 million cell-phone users, mostly in the Americas. (All the existing cellular communications protocols support application protocols such as WAP [Wireless Application Protocol]).
Over the EDGE
EDGE networks will add a new radio interface to the TDMA/GSM backbone, which will allow them to use the existing spectrum to send packet data at speeds of up to 384 kbps. Backing the EDGE standard is the Universal Wireless Communications Consortium (UWCC), an international association of companies including AT&T, Ericsson, Lucent, Motorola, Nokia, and Sony.
EDGE allows TDMA and GSM carriers to migrate to 3G services using their existing spectrums and portions of their existing infrastructures. (CDMA, on the other hand, requires building new infrastructures, which may delay implementation.) EDGE can be used by both TDMA and GSM services, which, according to AT&T, serve more than 300 million subscribers in nearly every world population center.
AT&T and Nokia Corp. have agreed to develop and test enhancements to EDGE that will enable simultaneous delivery of voice and data, as well as advanced multimedia applications such as real-time streaming media, voice over IP, and wireless video conferencing by the first quarter of next year. Commercial availability is planned for 2002.
The push for 3G has been "driven by skyrocketing demand for wireless Internet applications," according to a recent study by Cahners In-Stat Group, titled "3G Technology as a Fixed Wireless Solution." The study predicts that nearly 25 million people in the United States will be using mobile wireless Internet services by 2003.
According to the report, 3G represents "a form of sophisticated broadband transmission that, in addition to handling vast amounts of voice capacity, is optimized for transmission of data and multimedia."
The combination of protocols will solve one of the most common bugbears of mobile communications: the need to switch or rent phones when traveling abroad. "We're talking about global connectivity, where it's not going to matter if you're an AT&T customer in San Francisco," says Ken Woo, director of communications for AT&T Wireless. "If you go to Hong Kong, Beijing, London, or Paris, your phone will work and will follow you everywhere. All it will do is dial your Bay Area number. It really is ubiquitous service."
Beyond 384 kbps
In addition to global compatibility, 3G EDGE networks promise high-speed data transport beyond the 384 kbps they can achieve today. Specs call for data speeds of up to 2 mbps.
Woo says that people shouldn't get their hopes up too high, however. These numbers "are accurate with one person standing under a cell site with no one else on the system. But there will continue to be some days where you are faster, some days where you are slower. It depends on when you call and what you connect at."
With our need for speed constantly outstripping reality, it's no surprise that right on 3G's back is 4G, the fourth generation of wireless, which will use an optical technology called wideband OFDM (Orthogonal Frequency Division Multiplexing). OFDM uses light waves to transport IP packets from point to point.
"Fourth generation will provide total end-to-end IP capabilities," Woo says. "It's not going to matter how your calls get transported, whether it's from your home or your wireless phone or what-have-you. It's going to be all-encompassing [and] IP-based. Your networks are going to be wireless, your phones are going to be wireless, even cable TV and entertainment are going to be wireless."
Fourth-generation networks conceivably could transmit data at speeds of 5 to 10 mbps and may be on the scene by 2005. <<