Will the US 700 MHz auction be remembered for dismembering wireless?

High spectrum price could lead to catastrophe

The next door base station is built so that the transmitter facing its neighbor uses adjacent, but not identical spectrum and should not interfere with it. It's the base station after that or the one after that where an excessive signal will create interference. So at any given point in history, based on how many people have mobile phones in a given area and how often they use them and what they use them for, which of course is different in every country, there may be an optimal piece of spectrum. If so, is that 700 MHz right now? Or perhaps after all this is not the case?

What we are after is spectrum which does the best job of traveling the natural distance that urban base stations need to be apart to support traffic, but which can also reach remote rural towns in as few hops as possible.

Obviously the radiated power used can be adjusted, high power for long distance, and lower power for shorter distance. Underlying modulations can also change and carry more data or less, depending on error correction requirements etc… Of course urban areas can’t really be too low power, because then signals won’t go through buildings. This is worse for shorter wavelengths, so worse for 2.5 GHz than for 700 MHz. But this makes a minor difference.

Things are very different in a one way network, like a mobile TV network. There it is straight forward, the optimal power is high. Actually even that’s not true, not where two different areas have different frequencies for the same TV channels, multi-frequency networks. But in this auction the FCC envisages a single frequency network for Block E, so the more power, the better the reach, the less transmitters, the cheaper the build – fairly straightforward.

But it all changes if the application involves two way communications, then base stations in a town needs power turned to the optimal level, which in 700 MHz will be low.

Spectrum economics is such that you have an increase in price at any point in history where this sweetspot appears, which right now people are saying is 700 MHz. In this instance because it is deemed to be so valuable it is sold in smaller chunks of 5, 6, 10 or 11 MHz not great big 90 MHz chunks like Sprint has.

Of course getting 10 MHz or 20 MHz may lead to a great network, but it may get saturated in urban areas or else it requires lots and lost of base stations, which must be tuned to avoid interference issues.

One way, single frequency networks can be set up with 25 kilometer diameters as cells. Two way is a function of battery, antenna, both at the base station and the handset, and the spectrum itself. How long is that? Again it depends on modulation scheme, FEC etc,, but in 700 MHz this can be anything from the 25 km distance, as long as you have flat ground, no obstructions like trees or open water, and no terrain or atmospheric issues but when these conditions are against you it can be a little as twice the urban distances and even in 700 MHz might go as low as 5km to 8 km.

One analyst reckoned that 700 MHz in rural locations could have as large a cell radius as 3.5 times larger than 2.5 GHz or instance, and obviously the cellular community understands this because they have networks in the neighboring 800 Mhz.

A cell differential like that can mean that urban areas can be covered with one 700 MHz base station for thirteen 2.5 GHz sites. So in the cites they are roughly the same, and in the country they are anything but.

Similar topics

Similar topics

Similar topics

TIP US OFF

Send us news


Other stories you might like