Nigel Ballard, Wi-Fi guru on his Web site and wireless director for Matrix Networks of Portland Oregon, had a nuanced message for attendees at ISPCON. Drawing on his experience with the WiMAX Forum, he described his hopes for a technology that he feels can solve the well-known flaws in Wi-Fi.
Ballard admitted that the standards process is ongoing, as 802.16d, now called 802.16-2004 (see the article, And Now, 802.16-2004), continues. He said that the standards process is a contest in which each company has an interest, and that competition slows the development of standards.
Nevertheless, there are some encouraging features of 802.16-2004. The standard’s use of OFDM
“If you’re setting up an antenna, and you can see the antenna you’re pointing at, you don’t necessarily have a connection if you don’t understand the fresnel zone,” noted Ballard. He said that in one case he worked on, a building with reflective glass proved helpful as he was able to bounce the signal off the building to the other antenna. OFDM technology handles reflected signals particularly well, and WISPs are more likely to have to deal with reflected signals in urban areas (and in any place where the signal travels over water).
He pointed to two key flaws in the Wi-Fi standard that he hopes will be fixed by WiMAX. One flaw is the number of usable channels in the 2.4 GHz spectrum. “Currently, of 11 channels, we have only three non-competing channels,” he said. WiMAX, he said, can deliver 50 channels or more, a significant advance.
He added that a single WiMAX base station radio can simultaneously serve 3Mb of secure and QoS managed data to many clients.
This flaw is highlighted, he said, by the Vivato product, a multi-radio antenna that can swamp a single channel. If there were more channels, this would not be a problem. The 802.11g Vivato switch can only operate on a single channel and can only pass traffic to a single client at any one time, but in achieving that, its beam steering technology puts out such a potent carrier beam that it stomps on anything in its path. Ballard believes it is an inelegant way of achieving coverage.
He also said that the spectrum the standard uses is important. 2.4 GHz is not as useful as other parts of RF spectrum because 2.4 GHz is blocked by water, especially by trees, which contain a lot of water.
A new version of the Motorola CANOPY product, he noted, uses 900 MHz spectrum, which penetrates through trees. “700 MHz WiMAX would be ideal,” Ballard claimed. “With 700 MHz, you could go to any town, put 60 degree sector antennas on a tower, and light up the town.”
If WiMAX can do all of this and also provide better security and a higher link budget, it could deliver on the hype. (Ballard says WiMAX could provide a link budget of 150 to 160 dB, whereas Wi-Fi is about 60 to 80 dB. The difference of about 80 dB means WiMAX could be 80 times better, not just twice as good.)
Questions remain for WiMAX. Can the companies involved complete the standards process? Will WiMAX complete effectively with an installed Wi-Fi base in real world applications? Whatever transpires, Ballard is eager to convey the message that WiMAX is not just hot air, that there is a real potential in this new, much talked about standard.
Reprinted from ISP Planet.
