When the FCC offered licenses in the PCS band new companies, like Sprint and T-Mobile purchased licenses in the PCS Band and deployed systems only in this frequency band. In the case of providers like T-Mobile, they chose and continue to offer handsets that operate only in PCS and only one type of transmission (GSM). This means that this handset will only work in an area where PCS signal, operating in GSM is available; even if there is strong Cellular Band signal or PCS signal that is not GSM present, this type of handset is incapable of transmitting and receiving.

Other PCS providers, like Sprint, decided to provide dual band handsets that would operate on the Sprint PCS Band network and if they are out of their home service area these handsets will operate on other service provider’s Cellular Band systems, albeit, usually at a higher cost called a roaming charge.

The other exceptions are Nextel, Southern Linc and Mike. These providers use a frequency in the 800 Mhz range called the trunking band which is unique to the type of handsets used by these service providers and the handsets they offer are incapable of using any other cellular providers Cellular Band or PCS Band networks, in other words, when you are out of their service area signal is absent until you re-enter this network. As such this network has the smallest geographic footprint in the land.

It is noteworthy to mention that some countries in Latin and South America and Jamaica have deployed GSM1800. This frequency band

has traditionally been the higher frequency used in Europe, Asia and Africa and is not licensed for use in USA or Canada, but is deployed in mexico for example. So far it has only been deployed by cellular providers that use GSM signal.

Systems: 

Analog (AMPS)- Originally all cellular communications was done in the Cellular Band and the all signal was an analog modulation called AMPS. This means that a certain piece of frequency was open and devoted to a particular handset when a conversation was taking place, one can think of this as one lane on a multi lane highway on which only you drive while on this road. Analog systems still exist in many rural areas and most cell phones have analog capability except GSM phones. This type of modulated signal uses much more electrical energy to produce the same amount of power and is a much a less efficient use of frequency spectrum than digitally modulated signals. AMPS analog signal is only permitted in the 800 Mhz cellular band.

Types of Digital:

Digital signals operate in the PCS and Cellular band. There several types of digital systems using digitally modulated signals in use at this time. Digital systems and phones use less electrical power (battery) because they only use power to transmit when the coded bits of information that represent the spoken word or data being transmitted are actually sent, a burst as opposed to a constant stream. The same channel or frequency can be also used to accommodate multiple users therefore more information (data or calls) can be made without the need for more spectrum.

TDMA- The oldest type of digital system is known as TDMA (time division multiple access). This type of system was widely deployed and currently exists in urban and rural areas by many cellular providers including Cingular, AT&T and the majority of the smaller rural cellular providers, however, TDMA is not capable of the high speed data transfer capabilities of competing digital systems. Wireless high speed data transfer like pictures from your phone and many more applications have become popular enough to make TDMA cellular providers begin to change their systems.

GSM- this type of digital system is the most widely used worldwide because all of the European and most of the Asian service providers agreed to use it in the early days of digital in order to achieve interoperability. GSM is also the type of system that has recently been chosen by Cingular and AT&T and most of the existing small rural cellular providers that used to or still have TDMA systems. GSM is currently being added to existing TDMA networks throughout the land and cellular providers are replacing TDMA phones with GSM phones when the customers need a new phone. The cellular network providers are offering lower priced cellular plans and other incentives to encourage people to change to new GSM phones.

CDMA- this type of digital system has the highest capability for high speed data transfer and is deployed by large and small cellular providers. Most service providers that use CDMA systems have been using this type of system for several years and they have worked the bugs out for the most part.