Barely on topic -- new kinds of cell phones --
Scrapps wonders, "Digital cellular equals "PCS" doesn't it? I just got a PCS cell phone from PAC BELL and they really talk up the security of the PCS digital technology over the regular Cellular phones. My GTE cell phone had it's number snagged a couple years...."
I'll never get to a thousand posts like Moonray, much less to seven or eight thousand, if I just write these long explainations, but (I admit) I'm a techie, and explainations are good for everyone.... So.
That old GTE phone was almost certainly AMPS, which is the popular system in North America. It's also found in South America, but not much elsewhere, althogh there is a variant in Britain that's now disappearing. It's easy to intercept, since the voice is just FM radio, and all the control messages are unencrypted. The hacker's favorite phone is the OKI-900 series, which will dump control messages continuously to a serial port if you put it in debug mode!
I carry an AMPS phone, because it's cheap, and roams everywhere on this continent, even Mexico City. AMPS operates in the 900MHz band. There are two AMPS frequency ranges, so there is competition in most markets.
There are also digital systems which coexist with AMPS at 900 MHz. These are mostly sold with dual-mode phones, so that the phone can switch to AMPS where there is no digital coverage. The two systems are TDMA and CDMA. TDMA is somewhat simpler, and is a bit more widely deployed. In Chicago, Cellular One offers TDMA, but they've started promoting their PCS instead; I'm not sure why, but I suspect that the frequencies are less crowded.
PCS uses a new set of frequencies, at 1800 MHz, which were auctioned off by the FCC over the last several years. There are both "narrowband" frequencies (which seem to have been bought mostly by paging companies) and "wideband" frequencies (which seem to have been bought by cellular companies). There isn't any requirement for how these frequencies are used, but cellular is booming, and....
What's being used in the PCS frequencies as a mixture, which makes roaming a problem for the moment. Most of the systems I'm aware of either use the CDMA system at higher frequency, or the GSM system (which is European-developed, and the most popular system for the rest of the world) at higher frequency. In Chicago, Primeco has come out with a CDMA system, for instance.
Both CDMA and GSM are digital, and both work just fine. Your new PAC BELL phone could be one of either, but I did some hunting, and their web page shows GSM:
pacbell.com
Roaming is currently a problem for PCS users, because there's no guarantee that the system you use at home will be deployed elsewhere. Some dual-frequency phones are available.
As investors, every time you hear CDMA, you should think of Qualcomm, which owns the patents.
There are several (I think 3 per market, but I can't remember) PCS frequencies for every market, so there should be competition, but it's starting up slow. However, companies (often consortia of companies) paid big money for the licenses, so they will use them.
There are also some "cellular-like" systems which use business-to-business ("land mobile radio") frequencies, but offer cellular-style features. They often promote their conferencing features. Traditionally, these frequencies were used for truck dispatch, and every truck heard everything the dispatcher said!
Relevant COMS product for wireless telephone providers (which makes this on topic, not that we have any topic):
For AMPS providers: usr.com
And also: usr.com
For CDMA: usr.com |
