By: Diane Shired, CTM
Meaning of D-AMPS – "Digital Advanced Mobile Phone Service", is a second generation (2G) mobile phone system, it is also a term for digital cellular radio in North America. D-AMPS is a spin-off of AMPS which is a first generation (1G) analog mobile phone system developed in the 1980’s. D-AMPS mobile cellular uses digital radio transmission and is used all across the U. S. Three to six digital phone calls can be made with D-AMPS whereas; with AMPS only one phone call was available. The advantages of digital cellular technologies over analog cellular networks are the increased capacity and security.
In the 1990”s the digital cell technology was initiated. D-AMPS use TDMA to split each AMPS channel into 3 channels and literally compress voice data. Technology options such as TDMA offer more channels in the same analog cellular bandwidth and voice and data. Just like AMPS, D-AMPS uses between 800 to 900 MHz frequencies and is the digital version of AMPS the original standards for cellular phone. Because service providers have invested enormous amounts of money in AMPS, providers looked to migrate from AMPS to D-AMPS by overlaying their existing AMPS network with TDMA structure. It is easy to upgrade existing analog AMPS to D-AMPS.
Some of the characteristics of TDMA are:
Initial implementation triples the calling capacity of AMPS systems
Capacity improvements of 6 to 15 times that of AMPS are possible
All transmissions are digital
Many blocks of spectrum within 800 MHz and 1900 MHz are used
“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.” [ Informit,com - Digital and Analog Cellular Services, By Annabel Z. Dodd]
“Rather than invent a completely new technology, the existing AMPS standard was developed into a digital standard, which operates in the same area of spectrum in the 800 MHz band. The advantage of this approach is that the introduction of D-AMPS into an existing AMPS analogue network is easily accomplished. Dualmode analogue/ digital terminals have been developed, allowing operators to include both analogue and digital base transceivers in their networks, often sharing the same base station. Digital channels can easily be added to an existing AMPS network and any number of analogue channels can be made digital without disturbing the level of service. This smooth migration from analogue to digital allows a network operator to choose the speed and timing of his transition.” [ Global Personal Communications, By J P-W Huang]
“The FCC divided up the usable spectrum into hundreds of different sub-sectors. For example, cordless telephones got 43.69-50 MHz, FM radio broadcasting got 88-108 MHz, and so on. A fascinating list of what frequencies are used for can be found here. After dividing the spectrum by sectors the FCC divided it again by geography. There are two main sub-sectors allocated to digital phone service in the U.S: Digital Advanced Mobile Phone Service (D-AMPS) and Personal Communications Service (PCS). The majority of the wireless service providers in the U.S. operate on one of these two frequency bands. Other notable spectrum allocations are the analog systems, also known as Advanced Mobile Phone Service (AMPS) and Specialized Mobile Radio which is primarily used by Nextel Communications (Nasdaq: NXTL).
In order to promote competition, the FCC originally auctioned off two D-AMPS licenses in each sub-sector. Later, it split the PCS spectrum up to allow six competitors in each region. This was done to increase license revenues for the government and to lower prices by increasing competition. Suddenly, each geographic region could have as many as eight "wireless phone systems" in each market -- two D-AMPS and six PCS.
” [ The Motley Fool, By Todd N. Lebor]
