TDMA or CDMA, 800, or 1900--Which is BEST?

[wirelessfan2]

I was just wanting to know if anyone could explain to me the difference in an 800 or 1900 system and which is better, and also the pros and cons of TDMA VS. CDMA. Thanks a lot.

[WirelessBeachBum]

800 or 1900 system refers to the frequency range 800 MHz or 1900 MHz. The original A/B band carriers were 800 MHz Analog, the 1900 Mhz (or 1.9 Ghz, same thing) were a result of the Telco Act of 1996 which was intended to increase competition not only for wireless, but for Long Distance, and Local telco services also. The 1900 Mhz carriers are commonly called PCS carriers (Personal Communications Services).

Primary Differences:

800 Mhz, carriers are usually more established in their markets and most offer an analog system with a digital overlay, however in many rural areas of the country Analog may be the only signal available.

1900 Mhz carriers are the newer carriers in town, when these carriers won their licenses from the FCC they had a certain amount of time to cover a certain percentage of their markets, many have built out very quickly...however one thing going against the build out of these carriers is the fact it takes about three PCS cellsites to cover the area one site will with an 800 Mhz tower...Primary reason is the fact that the higher a frequency is the more "line of sight" it's signal...Obstacles and the natural curve of the earth greatly affect your signal in the 1900 MHz band. In some markets (such as mine) the incumbant wireless carriers have actually not kept up with the build out of the new carriers, most of the 800 MHz carriers were designed for use with three watt phones and in some areas these network have not been upgraded properly to operate with even a 6/10 of a watt portable phone This is the primary reason you hear such horror stories of poor analog roaming.

CDMA & TDMA-

code division multiple access (CDMA)
A spread spectrum approach to digital transmission. Each conversation is digitized and tagged with a code.The mobile phone is programmed to decipher a specific code to pluck the right conversation off the air. The process can be compared to an English-speaking person picking out the only other English-speaking person in a room full of people speaking other languages.

time division multiple access (TDMA)
The first generation of TDMA offers three-to-one gain in capacity for cellular systems with more to follow. The technique involves dividing discreet amounts of time on a radio frequency into blocks, then assigning different phone conversations to each block. In other words, each second might be divided into thirds, and portions of three phone conversations transmitted each second. The caller cannot notice the gaps because they are so short.

Cdma was developed by qualcomm corp. it allows higher capacity per channel and is generally less expensive to build than a TDMA network, however CDMA was developed after TDMA so some carriers not wanting to launch an untried technology chose to launch TDMA...some carriers use TDMA because of affiliations and for marketing reasons, for example US Cellular (a 800 MHZ carrier) when it came time for them to choose which technology to use, they went with CDMA in many markets, but in areas next to AT&T markets they went with TDMA, they are currently changing those TDMA markets over to CDMA. AT&T and it's affiliates (SunCom in the south) are TDMA, however AT&T and it's affiliates are in the process of switching their networks over to GSM (another digital method) GSM is very closely related to TDMA, but that's another story.

[wirelessfan2]

Thanks alot. That answers everything. I appreciate it.

[ILUVSOCAL]

AT&T and it's affiliates (SunCom in the south) are TDMA, however AT&T and it's affiliates are in the process of switching their networks over to GSM (another digital method) GSM is very closely related to TDMA, but that's another story.



Edge Wireless is their affiliate in the west.

[bobolito]

Very good explanation, WirelessBeachBum.