Digital and Analog Cellular Service
- Types of Digital Wireless Service
- The Advantages of Digital Cellular
- Personal Communications Services
- Nextel
- Pricing
Analog cellular services in the United States were developed in the 1970s by AT&T and were widely deployed by the late 1980s. They were implemented in a standard format so that all telephones worked on all analog cellular networks in the United States. However, analog cellular services became so popular that capacity was not adequate for future growth, particularly in metropolitan areas.
As a result, digital cellular was developed to add capacity and advanced features. Digital cellular offers features such as caller ID, call forwarding, and three-way calling. In addition, many of the handsets have paging, long battery lives, and short messaging services integrated via a liquid crystal display. The advent of digital cellular and Personal Communications Service (PCS) led to price decreases and affordable cellular for residential consumers. In 1998, for the first time, the sale of digital handsets exceeded that of analog handsets.
Wireless Services
|
Service |
Frequencies |
Features |
Comments |
|
Analog Cellular |
824MHz to 893MHz |
Provides basic calling and voicemail, and low-cost phones. |
Each area has two providers, the local telco and a competitor. All telephones can be used on all analog service. |
|
Digital Cellular |
824MHz to 893MHz |
Provides advanced features such as caller ID and telephones with built-in pagers, and longer battery life. |
Verizon, Sprint, and AirTouch use CDMA. SBC, BellSouth, AT&T Wireless, and Bell Mobility use TDMA. |
|
Nextel |
800MHz to 900MHz |
Has all of the same features as digital cellular. |
Nextel is the only cellular provider that uses these frequencies. |
|
Global System for Mobile Communications (GSM) |
890MHz to 960MHz |
The same handsets can be used in all countries that use GSM multiplexing. |
This is the standard used in Europe, the Far East, Israel, New Zealand, and Australia. In the United States, GSM is used by VoiceStream. |
|
Personal Communications Service (PCS) |
1.8GHz to 1.9GHz |
Has the same features as digital cellular. Uses more closely spaced, smaller antennas than cellular. |
Sprint Cellular, AirTouch, PrimeCo, and Alltel use CDMA. AT&T Wireless uses TDMA, which is incompatible with CDMA. |
Digital cellular services are being implemented differently in the United States than in Europe. In 1987, the European Union chose a standard called Global System for Mobile Communications (GSM) for delivering new digital wireless telephony. In the United States, the Telecommunications Industry Association (TIA) settled on a similar standard using time-division multiple access. However, shortly thereafter, many of the Bell telephone companies decided to use a newer method of multiplexing, code-division multiple access (CDMA). CDMA has greater capacity than time-division multiple access. The previous table provides a comparison of the various wireless services available.
Types of Digital Wireless Service
There are two main types of digital wireless service in the United States. One is called the Personal Communications Service (PCS), and the other is known as Digital Advanced Mobile Phone Service (D-AMPS). They use different frequencies or portions of the airwaves to transmit signals.
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Both work with either code-division or time-division multiple access.
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Both provide the same telephone features.
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Both are more difficult to eavesdrop on because the multiplexing scrambles the voice signals.
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PCS towers are smaller and must be spaced closer together. PCS vendors call their towers antennas because of their small size.
Thus, the United States started down the road with two different standards, both different than Europe's standards. In addition, the Nextel service works on a different frequency than that of PCS or D-AMPS (Please spell our Digital Advanced Mobile Phone Service). Interestingly, there were seven different, incompatible analog types of cellular service in Europe before digital GSM was installed. Incompatibility is a problem because customers with digital telephones cannot use their telephones when they travel to places with incompatible cellular service.
The major challenge for digital cellular is that no one carrier has a complete nationwide network. PCS providers such as AT&T Wireless and Sprint PCS are still building out their networks, as is Verizon Wireless. Regional Bell Operating Companies such as SBC and BellSouth are merging to create networks throughout the country. Most importantly, there are pockets everywhere, particularly outside metropolitan areas, with poor service and holes in coverage.