WiMAX Cell Phones Edge Closer to Reality

Power-saving chips are paving the way for super-broadband handheld devices.

WiMAX, the souped-up successor to the WiFi wireless standard, could greatly increase the amount of information that cell phones and other mobile devices can pull from the air. Until recently, however, the elaborate antenna technology needed for sending and receiving WiMAX signals has been a big drain on a mobile device's batteries.

Now that the telecommunications industry has settled on final specifications for WiMAX, though, including provisions for power efficiency, manufacturers are exploring ways to build the energy-efficient chips needed to make consumer WiMAX devices viable.

WiMAX-enabled handhelds would be able to access greater bandwidth than traditional cellular networks, allowing faster streaming media and Internet downloads. Moreover, WiMAX phones using Voice over Internet Protocol (VoIP) might drop fewer calls and keep working up to 50 kilometers away from base stations, compared with 16 kilometers for cellular networks and WiFi's mere 100 meters.

Some phones already come equipped with a WiFi chip and can access local WiFi hotspots in addition to cellular networks. But WiFi coverage is spotty -- while WiMAX signals beamed from central towers could blanket entire metropolitan areas. In addition, WiMAX signals can carry 70 megabits of data per second -- more than three times the roughly 20 megabits from WiFi, and far outperforming the 300 kilobits on cellular networks.

So far, only a handful of businesses in large U.S. cities are taking advantage of WiMAX technology, using equipment installed before the recent standards were finalized. In December 2005, the Institute of Electronics and Electrical Engineers (which created the WiFi (802.11) standard) agreed on technical specifications for mobile WiMAX. Now large companies, including Intel, Alcatel, and Qualcomm, are pushing to develop WiMAX-compliant base station and chipset technologies. Also, in the next few months, the WiMAX Forum, a consortium of companies making and deploying WiMAX equipment, will begin testing and approving mobile products, says Jeff Orr, the forum's director of marketing.

Like most chips for cell phones, WiMAX chipsets have two halves: one sends and receives radio signals, the other processes those signals. Sierra Monolithics of Redondo Beach, CA, specializes in making the radio-frequency portion of WiMAX chipset, which sends signals from the phone and receives them from a base station. By early 2007, the company expects to ship communications chipsets that extend the battery life of WiMAX handhelds into the same range as cellular devices, including the traditionally power-hungry dual-band phones used by international travelers.

Unlike cellular chipsets, which can access only a narrow band of the radio spectrum, often making downloads slower, WiMAX chipsets are designed to tune into and process broader swaths of the radio spectrum. Collecting and processing more of the radio spectrum requires more power, though, because more frequencies must be sorted through.

In addition, most WiMAX equipment uses antenna technology called MIMO (Multiple Input, Multiple Output), which uses more than one antenna to simultaneously collect and send more information greater distances, and power-hungry signal processing algorithms are needed to sort through the information collected via MIMO connections.

The power problem is even more formidable for manufacturers who want to build chips for multi-band WiMAX phone for use in different parts of the world. Each region, such as the United States and Asia, is setting aside a different portion of the spectrum for WiMAX, and accessing multiple bands usually requires a separate chip for each band.