Wireless USB poised to cut the cable

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First off the range of Certified Wireless USB is pretty short. After 30 feet or so, radios can?t hear one another.

Second, all radios within range listen for ?beacons? from other radios. These beacons are used to announce when the device wants to use the airwaves. There is a distributed protocol whereby devices will divide up the time so that each can transmit without interfering with other devices. This mechanism is also used for battery savings. Devices know when they are expected to listen or transmit and can turn themselves off at other times.

Third there are many channels. If a channel looks too crowded, a group of devices can all switch to another channel.

Six computers in an office would be an easy load. Sixty would be more difficult. The point of the 480 Mbps is not that you will get that much throughput. I wouldn?t expect more than 100 Mbps for first or second generation radios. The aggregate rate of several radios in a confined space can approach 400 Mbps.

Radios in a beacon group all share microsecond accurate clocks. Actually the accuracy is 20 picoseconds. Channel time is allocated in 255 microsecond chunks. Since each radio knows exactly when it can transmit or receive, there is very little dead air time. The result is that a group of radios makes very efficient use of the spectrum resources.

Posted by: BillyBrack   Posted on: 10/17/06 You are currently: a Guest | Members login | Terms of Use

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