Backers of WiMAX hope it could be used as a replacement for T1 lines for business, become a backhaul for 802.11 hotspots, provide Internet access for consumers and get integrated along with .11 into notebook computers some day. But it won’t be easy, as this EE Times article explains.
“It’s a big train wreck, and much more complicated than 802.11a design, especially in terms of dynamic range, spectral range and phase noise in RF,” said Colin Howlett, a senior RF engineer at VCom Inc. (Victoria, British Columbia). VCom is an RF subsystem maker that’s planning its first WiMAX system. To negotiate the RF divide, startup Redline Communications supports both direct-conversion and IF links in the ASICs and FPGAs in its latest system, which implements revision A of .16a. Redline is one of as many as 14 small OEMs in this arena currently evaluating the various WiMAX chip sets. “There are a lot of logistics concerns about bringing all this equipment in, setting it up, having the radio licenses you need and testing the stuff in front of a live audience,” said Gordon Antonello, senior technical adviser for Wi-LAN (Calgary, Alberta) and chairman of the WiMAX technical work group. “We are planning to have plug fests every quarter starting late this year so we can make changes in products, tests and standards as we need.” Other forum members aim to lobby governments and standards bodies to harmonize international spectrum rules governing wireless broadband, especially in the 2.5-, 3.5- and 5.8-GHz bands. “There are many, many issues that need to be resolved so we can make one product that can be sold around the world rather than 57 variants of it for each market,” said Senior of Airspan, who chairs the forum’s regulatory group. The forum plans to support mobility and roaming in 2006, based on a .16e standard. “We’re working with various participants to see what we can do to accelerate this,” said Sheldon Fisher, vice president of broadband wireless for Sprint, though he would not detail plans. He said that “2006 or 2007 is too late. By that time, 3G will have a strong foothold.” For its part, Nextel is conducting trials for a broadband wireless offering using an undisclosed technology over 2.5-GHz spectrum it purchased last year from Worldcom. The system could be used to deliver data as well as local voice and cablelike video services, said Barry West, Nextel’s chief technology officer in a keynote address here. “I am willing to go with a proprietary technology, but I need to see a path to a standard,” said West. He said Nextel could spend up to $2 billion building the network. Navini Networks is developing proprietary portability features. The company has tested the technology with all three carriers in South Korea as well as with Sprint. It plans to migrate its approach to .16e, though it will not support .16a, said Sai Subramanian, vice president of product management. As for price, West said Nextel needs to deliver a Gbyte of data for $20 or less, a capability it will sell for $30 or more. Sprint’s market research shows customers will spend no more than $50 a month for multimegabit wireless access. Despite the problems, some carriers are still bullish. “WiMAX is probably the best opportunity we’ve had in a long time” to get wireless broadband off the ground, said Fisher of Sprint.
One immediate puzzle is how to match at least four upcoming .16a chip sets with four RF companies. Some baseband chips will use direct conversion and others intermediate-frequency interfaces to RF. Intel and Fujitsu said they will design integrated basebands, but others are preparing separate physical-layer and media-access control chips.
The Forum plans to finish a .16a test suite for systems by October and hold its first plugfests in November or December. Final conformance testing could take about a month, at a lab yet to be set up.
