No, 3G cell phones aren't available yet. But we're getting close. The first 3G phones will show up in Japan this year as NTT-DoCoMo initiates its WCDMA system in May. European countries will no doubt be next as they're already on the upgrade path from the current Groupe Speciale Mobile (GSM) systems to WCDMA. The U.S. is lagging due to the many competitive standards and the large number of carriers, manufacturers, and others with investments in specific technologies. Moreover, distractions caused by 2.5G standards further delay real 3G. Most carriers and equipment manufacturers believe that 3G won't hit the U.S. in full force until 2003 or 2004.
Today, the world is firmly in the midst of 2G cell phones or digital cell phones. Europe and most of the rest of the world supports GSM, a TDMA system. In the U.S., the older analog AMPS system is still widely used along with a variety of 2G digital systems. One of the most widely used systems here is the CDMA system invented by Qualcomm Inc. Formerly called CDMAOne, it's based on the IS-95A/B standards.
The IS-136 TDMA system also is popular throughout North America. But GSM is additionally used in the higher frequency, 1900-MHz PCS band in the U.S.
Characteristics of 3G phones were spelled out by the International Telecommunication Union's (ITU's) IMT2000 guidelines announced last year. In general, a 3G phone should permit global roaming and have packet-based rather than circuit-switched data-transmission capability. The data rate should be at least 144 kbits/s from a moving vehicle, 384 kbits/s at pedestrian speed, and 2 Mbits/s from a fixed location. This makes such applications as e-mail, Internet access, and even video transmissions possible.
Carriers have several options for migrating from 2G to 3G systems (Fig. 1). For GSM, it's best to go to GPRS and/or EDGE. GPRS is a 2.5G technology that works with GSM and steals time slots from voice to support data in the channel. It's essentially a software overlay in the basestation that works with GSM and provides a data rate of up to 115 kbits/s. GPRS isn't 3G, but it provides a high-speed packet-based system that speeds up available slow circuit-switched data approaches. While GPRS has yet to be deployed, several carriers have tested it, and some will implement it in 2001 as an interim solution until they decide on a firm 3G solution.
A Cutting EDGE Solution
The most promising TDMA/GSM data enhancement is termed EDGE for Enhanced Data Rates for Global Evolution. This system builds on the GPRS time-slot-stealing packet-data structure, but it adds 8PSK modulation for a data rate of up to 384 kbits/s. GSM/GPRS adopters can quickly and easily upgrade to EDGE with another software overlay and by adding new radios capable of demodulating the 8PSK signals. As far as IS-136 TDMA users are concerned, EDGE is their only hope for near-3G solutions. Motorola Inc. has an EDGE solution for IS-136 carriers with its Aspira product, which provides up to a 476-kbit/s data rate.
In Europe, the ETSI and ITU encouraged all GSM carriers to adopt the UMTS WCDMA system. This system uses frequency-division-duplexed (FDD) 5-MHz paired channels to provide a data rate of up to 2 Mbits/s. UMTS WCDMA requires lots of spectrum space, which may not be available.
Spectrum is a precious commodity in the U.S., where UMTS WCDMA might not be practical. Fortunately, a time-division-duplex (TDD) version of WCDMA has been developed. It maintains use of a single 5-MHz channel, and time-shares send and receive functions while maintaining compatibility with the FDD WCDMA. This permits widespread roaming.
In the U.S., 2G CDMA systems are being expanded to meet 3G specifications, via the cdma2000 upgrade path, which takes the IS-95A CDMA standard and enhances it to meet 3G goals. IS-95A supports 14.4-kbit/s circuit-switched data. Though IS-95B takes this to 64 kbits/s, it has never been widely adopted, nor will it probably ever be, given the other CDMA developments.
Cdma2000 supports 1X and 1XRTT packet data up to 153 kbits/s within one standard 1.25-MHz IS-95 channel. Up to 307 kbits/s is possible with a recently released upgrade version of 1X. A 3X version using three 1.25-MHz channels raises the data rate to about 460 kbits/s, which places it nearly in 3G territory. All of this is backwards-compatible with existing IS-95A systems, making the upgrade more affordable than going to a new WCDMA system. In the meantime, Motorola came up with an enhancement to 1X. Called 1X Plus, it has a data rate of up to 1.38 Mbits/s in a single 1.25-MHz channel.
Qualcomm recently an-nounced the 1XEV enhancement to cdma2000: one 1.25-MHz channel with a 2.4-Mbit/s data rate. This is clearly a 3G-level system that bears serious consideration in the U.S.
No, there won't be a single 3G standard here. We will continue to live with analog, 2G, and two or three variants of 2.5G and 3G. As a result, the real design challenge will be multimode, multiband cell phones as well as basestation solutions that support both the legacy and the newer standards.
The reasons for 3G are many and varied. But as always in business, the bottom line rules. Carriers expect to increase revenue and profits with 3G applications and expanded capacity. Users want and need the wireless data applications.
If 3G means broadband data rates, then what will be the primary applications of a 3G phone? Most believe that the 3G "killer app" will be...ta daa...voice. This should be no surprise. After all, a cell phone is first and foremost a telephone. Just because it can handle packet data doesn't mean that data applications will dominate its use.
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