From The Labs: Clearwire WiMax

While it has yet to roll out a commercial WiMax network, Clearwire does offer broadband wireless services in 16 states based on Motorola's proprietary OFDM-based Expedience technology. Clearwire recently launched service in Syracuse, N.Y., the home of our Syracuse University Real-World Labs, so we grabbed an opportunity to try out the network.

Clearwire provided us with two access mediums, a PC card and a standalone modem designed to provide residential access. Both products delivered as-advertised average downstream performance, 1.9 Mbps. Upstream performance, advertised at 256 Kbps, came in at 200 Kbps in our testing. The norm for latency was 86 milliseconds. In comparison, our last round of EV-DO Rev A testing yielded average downstream results of 1.1 Mbps and upstream transfer rates of 511 Kbps.

Given that a Clearwire connection is shared medium with limited upstream bandwidth, those who want to use the connection for media applications, like videoconferencing, may be disappointed. However, our largest issue with Clearwire's service came down to coverage. The spectrum that Clearwire operates in, the 2.5-GHz band, doesn't propagate as well as the lower frequencies used by technologies such as EV-DO. Combine that with the limited number of cell towers currently in Syracuse, and coverage was decidedly spotty. We tried to test from two facilities located a half-mile mile apart but were able to receive service at only one site. Clearwire told us technologies such as multiple input, multiple output (MIMO) and beamforming will likely improve both coverage and performance by the time WiMax is rolled out across its entire network.

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