Currently, the most popular model for designing wireless systems is to flood a large area from a central site. This is what the bulk of mobile telephone systems do. But as higher data rates are demanded, this model ceases to remain economical. It takes too much infrastructure and spectrum to provide a multitude of users quality communications in the downstream direction. And, in the upstream direction, user to base, with user transmitter power and antenna size limited to that of portable devices it ceases to even be possible.

An example of this trend can be seen in 3G smart phones. For example, the 3G standard used on my new Treo 700P is called EV-DO. However, in order to achieve a 3G downstream data rate to a user located anywhere within an existing voice coverage footprint, EV-DO requires that the entire output of the cell sector's transmitter be used.

So, rather than allowing up to ~60 voice users to simultaneously share (and pay for) the hardware, as for a voice call, for high speed downstream data, it has to commit all the transmitter resources to a single user. This means that as additional EV-DO users come into that coverage area, the average data rate is divided down by the number of users who are sharing it.

This over-subscription rapidly makes the 3G services, like rapid Web surfing, streaming audio or video that the user was expecting to experience, impossible. Adding more transmitter carriers can help to a degree, but spectrum is scarce and hardware is not free so this flood-from-a-central-site eventually hits a dead end.

The same general problem shows up with any and every higher speed standard and technique, whether it's mobile phone, WiFi, WiMax or another standard not yet invented. Longer radio paths in typical environments simply have too much waste to provide economic high speed data.

The only possible solution requires shortening the length of the wireless path. This achieves coverage of a smaller area, thus limiting the data-rate dilution produced by sharing and over-subscription and it reduces the waste and allows a much greater amount of energy to be transferred across the wireless link. Both of these improvements have the result of enabling much greater information rates as well as requiring lower transmitter power, smaller antennas and having longer battery life.

I believe that Corridor's technology provides a compelling solution to the last mile problem. It can provide very high capacity transport between a fiber termination and a multitude of "emitters" located quite near the end users. These emitters can be located at every power pole if desired, thereby allowing the final radio hop to a portable information device to be both very short and very high capacity.

The characteristics of the suburban radio path shown in the sidebar article assume antennas 20 meters from the ground on one end and 2 meters at the other, which is representative of typical cell bases and users. The attenuation associated with wireless propagation is a very strong function of antenna heights. This is because the heights strongly influence how much foliage and and how many obstacles lie in the path.