The New Last Mile Broadband: WiMAX - Page 2
April 30, 2004
It's more than that though. Chang explains, "Unlike 802.11, when you have one frequency and energy, WiMAX range and performance can vary quite a bit depending on the number of frequency bands supported, the frequency itself—the maximum range of the 2.5Ghz is much longer than 5.8GHz—and the power."
Generally speaking, WiMAX has a range of up to 31 miles, which can be used to provide both campus-level network connectivity and a wireless last-mile approach that can bring high-speed networking and Internet service directly to customers.
In practice, Rerisi expects WiMAX's base stations to cover areas with a radius of ten miles. "It really depends on the number of subscribers. To guarantee high speed to users, since the WiMAX pipe is only so big, and its bandwidth is shared with subscribers, the target is to have no more than 500 subscribers per base station. "
Once it's here though, many broadband users may want it. 802.16 can give users high capacity links on both the uplink and the downlink of up to 75 Mbits per second (Mbps) data-transfer rates on a single channel, compared with 802.11b's theoretical 11 Mbps.
802.16 obtains these speeds in the 2 to 11 GHz range by using Orthogonal Frequency Division Multiplexing (OFDM). OFDM is a spread-spectrum technology that bundles data over narrowband carriers transmitted in parallel at different frequencies.
"In practice," Chang continues, "the channels won't be able to deliver 75Mbps per channel because radio frequency licensing makes the channels narrower than the 802.16 standard allows. Channels can be bonded together to provide higher bandwidths. Thus, for example, six channels can be used to provide an effective bandwidth of 250 to 350 Mbps."
WiMAX may turn out to be more than just a broadband backbone though. Intel, in particular, hopes that WiMAX proponents will complement Wi-Fi. The company plans to create chipsets that can handle both the 802.11 and 802.16 technologies. Laptops with these chipsets would use whichever signal was strongest in a given area.
While Wi-Fi and WiMAX may end up complementing each other, another growing technology may give both competition in the years to come: IEEE 802.20. This standard, like 802.16 is aimed at wireless high-speed connectivity to mobile consumer devices—such as cellular phones, PDAs, and laptops.
802.20 will run in the 500 MHz to 3.5 GHz range and is being led by Flarion Technologies and ArrayComm. While officially, the two standards are not trying to do the same thing or compete for the same audience, not everyone agrees that that is the case. Rerisi says, "They do have some minor differences, but they both are aimed to serve similar users."
Mathias comments, "Both attempt to deal with mobile broadband. My feeling about it is 'may the best man win.'" That, he thinks will be, "Whoever does the best marketing job wins. The conventional wisdom is that 802.16 will win but I think it's too early to handicap this race."
With the strong support of Intel—with its considerable resources, marketing muscle, and influence—most analysts believe that WiMAX will become successful and popular. As Mathias observes, "the real question will be how effective will WiMAX be in the mobility end of things and for that we don't have an answer, but I wouldn't bet against it."