Correction on GSM
Hope you all had a great weekend. On some pages at this site I've written incorrectly that GSM can use CDMA as a transmission technique. GSM, though, was built from the beginning to use TDMA, time division multiple access, and not another method. Please let me know if you find this mistake in any of my writing, I will be grateful. One reason for my mistake is that I haven't written anything on GSM, another is the term personal communication service.
PCS or personal communication service is an FCC term for the 1900Mhz band and a marketing phrase that causes much confusion. Some carriers like Pacific Bell operate the TDMA based GSM at 1900 Mhz. They call their service not GSM but PCS. Sprint uses a different technology, IS-95, to also provide cellular radio at 1900 Mhz. It's a CDMA based operating system. So, although different services within the PCS band may use one technique or the other, depending on what transmission technique they were designed to use, no system may use both. Confusing enough? I'll say. If you are really interested in GSM and PCS, download Professor Levine's file in .pdf, it's a great introduction to cellular radio.