Gary:
I don't have much to add to Frank's commentary; I think he has a handle on the space far better then his modesty allows (g).
From 50,000 feet a couple of thoughts, all IMHO:
In the near term last mile connectivity will be provided by a mosaic of technologies - deployed where either there is an absolute cost advantage or where there is a strategic imperative which trumps the cost factor. Consequently, I have no doubt that cable modems, xDSL, fiber, wireless and satellites will all have success.
Focusing just on terrestrial wireless, one has to distinguish first between mobile and fixed. Mobile wireless (cellular, PCS) is developing 3rd generation technology which is promising burst rates up to 5 mb/sec. Due to the placement of the cellular and PCS bands on the frequency spectrum, the opportunity exists for ubiquitous coverage, i.e., anyone/anywhere can get it. However, I don't believe it will become a viable last mile contender in all but the most rural locations because the cost per bit will always be too high due to the small frequency allocations per company at these frequencies and because transmission efficiency (commonly expressed in bits/hertz) is low due to the mobility requirement.
That leaves the fixed environment. Generally, the proponents of wireless last mile connectivity are using spectrum above 2 Ghz. MMDS at 2.5 Ghz, recently in the news with the MCIWorldcom and Sprint acquisitions, is the frequency being used by WLGS. The most prominent broadband wireless companies, Teligent, Nextlink, and Winstar are or will be using spectrum in the 24, 28 and 38 Ghz bands. Service at these frequencies is limited by line-of- sight (LOS) considerations, i.e., if one cannot see the transmitting tower from the receive location, you probably cannot get service. (For example, trees block the signal quite effectively ) Consequently, the aforementioned companies are primarily focused on provding service to business - where the monthly recurring revenues are higher and hence the engineering cost associated with insuring an adequate signal can be predictively recovered.
Last mile - broadband - connectivity to residences is a tough nut because of the LOS issue. I've read many a PR which implied service availability for consumers - but it still will be a hit or miss proposition.
One last note on WLGS. While there is adequate spectrum for broadband wireless in the MMDS band, it is not allocated in a contiguous block to any one company. Notwithstanding that there is 200 MHz available, it is subdivided into blocks of various sizes - most commonly 4, 6 MHz channels - as well as being divided between commercial and non-commercial (most educational) interests. Consequently, acquiring sufficient spectrum in any particular city to provide a robust, high speed service capable of delivering a minimum of 256-512 kbps (using Frank's number) to a sufficient number of subscribers to reach operating breakeven has to be looked at on a case by case basis. I have not looked at WLGS' spectrum holdings so I cannot comment further. For information of the structure of the MMDS spectrum allocation a lot of good technical and historical background information can be found here #Subject-9526
Current information on the broadband wireless players in the millimeter wave bands can be found here: #Subject-27423
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