A Basic Explanation of PCS

If you are unfamiliar with the basics of wireless communications, it may be helpful to read my Conceptual Introduction To Wireless Communications (With A Short History Of Wireless). That is, it may be helpful to read after I get around to writing it. (I wanted to write this first, sorry.)

PCS stands for Personal Communications Services. However, the term is rather general in meaning; it is roughly equivalent to saying 2G (i.e. Second Generation mobile communications). There are, however, a few specifics that can be assigned to the term PCS.

• PCS is a term used for wireless communications.
• PCS implies digital communications.
• PCS implies capability beyond voice communications, including services such as mobile email and wireless Web access.
• PCS radio spectrum licenses in the U.S. cover 140Mhz of spectrum, from 1850Mhz to 1990Mhz*, but in any given geographic area, only 120Mhz of that range is licensed for use by wireless service providers.†
• PCS service is implemented in a wireless device using one of three technologies: GSM, CDMA, and TDMA.‡ Devices built to use one of these technologies generally can't make use of the other two.**
• Like traditional cellular technology, PCS requires an infrastructure of radio towers, but PCS towers must be more densely packed than analog cellular towers.

* The range of spectrum detailed above is for Broadband PCS. There is an additional 3Mhz of spectrum licensed in 1Mhz chunks for Narrowband PCS. These chunks lie in the radio spectrum at 901Mhz, 930Mhz, and 940Mhz. The expected use of these licenses is two-way paging, voice and text messaging, and wireless email.

† The unlicensed chunk of spectrum is for use in low power local applications (e.g. wireless office LANs).

‡ I don't know really understand the differences between these technologies yet. The primary difference seems to be the method for dividing messages among chunks of bandwidth. CDMA divides radio channels based on usage while TDMA and GSM divide based on time slots. Also, I am not sure if these are the only three technologies in use or merely the dominant three.

** In the U.S., most major PCS carriers use CDMA. They are dependent on infrastructure that supports CDMA. Outside the U.S., GSM predominates. Voicestream is the only major PCS carrier in the U.S. that uses GSM, making it the only PCS carrier in the U.S. that can offer international roaming.

Questions I would like to answer to finish this page:

Are there satellites used in PCS infrastructure?
Do two-way pagers and devices like the Blackberry use GSM, CDMA, and TDMA technologies?
Who uses the Narrowband licenses?
Which providers use what bandwidth and what technologies?
What companies and what countries use what technologies?
How do the competing PCS technologies work? What distinguishes them?
Do PCS devices support WAP (and i-mode), or is WAP a 3G thing?
If PCS supports WAP (I figure it probably does), does WAP work independently from the underlying PCS technology? (Again, I figure it probably does.)