The Wireless Edge: Wide-Area Wireless--The Next Five Years

Recently, I concluded the research phase of a large project to assess the future direction of all the major wide-area wireless technologies, including 3G and WiMAX. There is so much going on that it has left my head spinning. But at the same time I'm quite excited, because the future of mobile data just keeps getting brighter. As an IT manager, you won't be able to immediately take advantage of many of these enhanced technologies, but it may be helpful to know what will be available in what timeframe. It's also interesting to see how the 3G vs. WiMAX battle is shaping up.

3G today consists of the GSM/UMTS technology family and the CDMA2000 family of technologies. The version of UMTS (Universal Mobile Telecommunications System) that Cingular and other operators around the world are deploying is based on 3GPP (Third Generation Partnership Project) specifications release 5. This release includes a service called HSDPA (High Speed Downlink Packet Access). HSDPA has theoretical rates to 3.6 Mbps with today's devices, increasing to 7.2 Mbps in 2007. Real-world limitations, however, limit the peak rates you will experience to just over 1 Mbps. With multiple users active in a cell, speeds may drop to the 500 kbps range. Cingular is quoting typical rates of 400 kbps to 700 kbps. Interesting, it's only in the United States that operators quote "typical" rates. These are actually very slippery numbers, as they are based on backhaul architecture and capacity, cell site spacing, voice load and data load. Beyond HSDPA, 3GPP Release 6 specifications include a new service called HSUPA (High Speed Uplink Packet Access), which boosts peak uplink speeds to just over 1 Mbps, with theoretical peak rates of 5.76 Mbps. HSUPA will be available next year. People are calling the combination of HSDPA and HSUPA simply HSPA (High Speed Packet Access).

However, with UMTS/HSPA, it doesn't end there. A series of improvements are planned for HSPA in a combination of efforts. The first will come in the context of Release 7 functionality, and the next will come in an effort called HSPA Evolution or "HSPA+." Through a combination of radio techniques including channel equalization, mobile receive diversity and MIMO (Multiple Input Multiple Output), HSPA+ takes CDMA close to maximum theoretical efficiency. Peak rates could exceed 25 Mbps in a 5-MHz downlink/5-MHz uplink spectrum allocation and users could experience two to four times the rates they can with HSDPA today. This technology, which could be ready by 2008, could match mobile WiMAX in the same amount of spectrum.

Finally, to round out their offensive strategy, 3GPP is also busily defining an OFDM-based system called 3GPP Long Term Evolution, slated for initial deployment in the 2009 timeframe, with peak rates of 100 MHz in a 20-MHz radio channel. The combination of HSPA+ and LTE will competitively squeeze WiMAX. Mobile WiMAX on paper exceeds HSPA performance, but it won't necessarily exceed HSPA+ by very much. Meanwhile, LTE is designed to be more efficient than Mobile WiMAX. With respect to timing, initial Mobile WiMAX networks could start appearing by the end of 2007 but are more likely in the 2007 timeframe, assuming operators embrace the technology and find spectrum to deploy it in.

If WiMAX doesn't have enough competition, it also has to watch the aggressive development moves of the CDMA2000 camp, as represented by 3GPP2 (Third Generation Partnership Project 2). The first improvement to today's EVDO (Evolution Data Optimized) Rev 0 technology will appear next year with Rev A, which boosts peak downlink throughputs from today's 2.4 Mbps to 3.1 Mbps, and boosts uplink throughputs from today's 153 kbps to 1.8 Mbps. Like HSPA, peak rates that users experience in either direction will likely be around 1 Mbps, with lower average rates. For Rev A, Sprint has indicated 450 kbps to 800 kbps average for downloads and 300 kbps to 400 kbps average for uploads. Beyond this, and available by 2007 for deployment though no operators have yet committed to this, EVDO Rev B can combine up to 15 1.25-MHz radio channels in 20 MHz of spectrum for peak rates of 73.5 Mbps. More likely, an operator would combine three channels in 5 MHz of spectrum for peak theoretical rates of 14.7 Mbps on the downlink, matching HSPA peak throughputs. 3GPP2 is also working on Rev C, which is likely to be an OFDM-based approach. One avenue here is the possible convergence of Rev C with the IEEE mobile broadband standard, IEEE 802.20. 802.20 is currently on hold because of allegations of impropriety in the standards process, but this won't necessarily affect the long-term outcome.WiMAX proponents will have to try and prove that their technology is sufficiently better, and sufficiently less expensive, than alternatives to gain acceptance. Large companies like Intel, Motorola and Nortel are all betting heavily that they can do this. My view is that the massive investment involved in R&D and deployment--and the competitive pressures from other approaches like metro Wi-Fi--makes it likely that only two wide-area technologies can survive long term. I don't see GSM/UMTS/HSPA/LTE going away because of its dominant global market share today, meaning that five to 10 years from now, people may be trying to remember what the acronyms EVDO and WiMAX stood for.

Peter Rysavy is the president of Rysavy Research ( http://www.rysavy.com/ ), a consulting firm that specializes in wireless technology assessment and integration.