Even though the rollout of 3G networks such as UMTS, HSDPA and EV-DO is only now gaining momentum and service is not expected to be widely available until the end of next year, there is already a lot of discussion about 4G as well as a considerable amount of confusion about what 4G really is. This is an area I've been looking at closely over the last year, including publishing a new public report on Oct. 24, 2005, titled "Hard Numbers and Experts' Insights on Migration to Evolved 3G and 4G Wireless Technology," presenting at the WiMAX World Conference on Oct. 26, 2005, on "Evolution of Mobile Broadband Wireless" and publishing a paper via 3G Americas in September 2005 called "Data Capabilities: GPRS to HSDPA and Beyond." These projects, among others, have given me the opportunity to collect facts and viewpoints on the current situation going from 3G to 4G wireless.

So it was with interest that I read on Oct. 19, 2004, that T-Mobile in Europe was deploying a new wireless service in the Czech Republic called "Internet 4G." Since everything else I had learned about 4G pointed to deployment after 2010, I was quite excited to think that somebody had leapt into the future, grabbed some great wireless technology to deploy today, and obsoleted global 3G deployments. But that was not the case. In fact, T-Mobile's deployment is based on UMTS-TDD (Universal Mobile Telecommunications Network-Time Division Duplex), an official 3G technology specified by 3GPP (Third Generation Partnership Project). The vendor is IP Wireless, one of the world's leading UMTS-TDD equipment manufacturers.

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When I questioned IP Wireless about the use of the term "4G" for this service, the company said it was the operator's decision to convey the sense that the service would provide greater capability than existing 3G networks such as UMTS. In fact, UMTS-TDD as implemented by IP Wireless is very similar to the HSDPA (High Speed Downlink Packet Data) version of UMTS operators like Cingular are beginning to roll out. The key difference is that most cellular operators are deploying UMTS/HSDPA in paired spectrum, with separate transmit and receive frequencies, whereas UMTS- TDD operates in a time division duplex mode. Since UMTS-TDD and HSDPA significantly outperform original data capabilities of UMTS, which is an official 3G technology, there is a desire among marketing types to differentiate the new services. But referring them to 4G is inaccurate. Here's the current roadmap to 4G.

First, operators are busy deploying HSDPA as well as CDMA2000 EV-DO (CDMA2000 Evolution Data Optimized). These highly capable services will offer throughput rates in the 500 to 1 Mbps range and should be widely available in most major U.S. metropolitan areas by the end of 2006. Then there are a series of enhancements planned for these technologies, including higher speed uplinks, advanced antenna architectures to boost speeds and improve network capacity and, eventually, VoIP in conjunction with quality of service control. Those items will happen over the next two to three years.

After that, 3GPP (representing GSM/UMTS companies) has an effort called LTE (long term evolution), which has goals of supporting flexible channelization (1.25 MHz to 20 MHz), peak throughput rates of 100 Mbps on the downlink and 50 Mbps on the uplink, extremely low latency and equipment ready for deployment by 2008-- a somewhat ambitious time frame. It is likely, but not definite, that LTE will use an OFDM radio interface.

3GPP2 (representing CDMA2000 companies) also has an aggressive evolution path, including EV-DO Revision B, which combines up to 15 radio carriers (each 1.25-Mhz wide) for a peak downlink speed of 46.5 Mbps), and a longer term project called 3GPP2 Evolution. The intent of both 3GPP and 3GPP2 efforts is to counter the competitive threat of Mobile WiMAX, which is much further along in terms of standardization but has little mobile operator commitment so far.

It is only after we get through this evolved set of technologies, which some have referred to as "Super 3G," that we start approaching 4G. There is no official 4G standardization yet, but early "industry consensus" indicates 1-Gbps peak rates, typical throughputs of 100 Mbps, network agility and best-of-breed radio techniques. The current 3GPP timeline for 4G deployment is around 2012, although I consider that a best case given all the interim steps.

Where does Mobile WiMAX fit in? Some have mused about WiMAX being a 4G technology, but that also is inaccurate. Mobile WiMAX does, however, embody many of the capabilities planned for evolved 3G systems. Hence, from a technology point, it is on an unofficial "roadmap" moving toward 4G.

Bottom line, other than companies co-opting the term "4G" for marketing purposes, we're a long way from 4G.

Peter Rysavy is the president of Rysavy Research, a consulting firm that specializes in wireless technology assessment and integration.