CDMA versus TDMA? Analog versus digital? Sprint versus Verizon versus
AT&T?
If you’ve ever shopped for one, you know that mobile phones are available in a
wide and often baffling array of standards and technologies, with many confusing
technical terms. But once you understand what a mobile phone really is — a device
for sending voice and data through radio signals — it becomes much easier to
understand how mobile phones work and how all the different technologies make a
difference to you.
According to guidelines set by the Federal Communications Commission (FCC), mobile phones may send
signals at 800 MHz and/or 1900 MHz in the U.S. Other countries allow mobile phone frequencies at 900 MHz
and 1800 MHz.
Mobile phone frequencies are more than a hundred thousand times higher than the human voice, which ranges
from 300 to 3300 Hz (whereas 1 MHz = 1 million Hz). Mobile phone frequencies are also higher than signals
used by some common household devices, such as TVs and cordless phones
While some mobile phones, known as single band, work at only one of these frequencies, others, known as
dualband or triband, work at two or three frequencies. To everyday users, it is important to remember that the
different digital mobile phone frequencies work virtually the same.
Some mobile phones, known as dualmode or trimode, can handle two or three different mobile technologies.
Some of these multiple-mode phones feature both analog and digital technologies, while others incorporate
different digital technologies or different frequencies.
Digital technologies compress large amounts of sound information into smaller codes that are faster and easier
to send. While analog networks (e.g., AMPS, NAMPS) can send only one phone call per radio channel at a
time, digital networks can simultaneously send the codes for several calls over each radio
CDMA, TDMA, GSM, iDEN, and CDPD coding standards !!!!
Basically, CDMA and TDMA are the two main digital technologies for mobile phones, and GSM and iDEN are important forms of TDMA. CDPD is something you can combine with TDMA to make data calls, such as for email or web browsing.
AT&T?
If you’ve ever shopped for one, you know that mobile phones are available in a
wide and often baffling array of standards and technologies, with many confusing
technical terms. But once you understand what a mobile phone really is — a device
for sending voice and data through radio signals — it becomes much easier to
understand how mobile phones work and how all the different technologies make a
difference to you.
According to guidelines set by the Federal Communications Commission (FCC), mobile phones may send
signals at 800 MHz and/or 1900 MHz in the U.S. Other countries allow mobile phone frequencies at 900 MHz
and 1800 MHz.
Mobile phone frequencies are more than a hundred thousand times higher than the human voice, which ranges
from 300 to 3300 Hz (whereas 1 MHz = 1 million Hz). Mobile phone frequencies are also higher than signals
used by some common household devices, such as TVs and cordless phones
While some mobile phones, known as single band, work at only one of these frequencies, others, known as
dualband or triband, work at two or three frequencies. To everyday users, it is important to remember that the
different digital mobile phone frequencies work virtually the same.
Some mobile phones, known as dualmode or trimode, can handle two or three different mobile technologies.
Some of these multiple-mode phones feature both analog and digital technologies, while others incorporate
different digital technologies or different frequencies.
Digital technologies compress large amounts of sound information into smaller codes that are faster and easier
to send. While analog networks (e.g., AMPS, NAMPS) can send only one phone call per radio channel at a
time, digital networks can simultaneously send the codes for several calls over each radio
CDMA, TDMA, GSM, iDEN, and CDPD coding standards !!!!
Basically, CDMA and TDMA are the two main digital technologies for mobile phones, and GSM and iDEN are important forms of TDMA. CDPD is something you can combine with TDMA to make data calls, such as for email or web browsing.
How does CDMA work?
CDMA, or Code Division Multiple Access, is known as “spread spectrum” technology, because it does not send
radio signals purely intact. Instead, CDMA divides up a radio signal over a range of different channels. Then, as
the signal is being received, it is recombined into one channel that can be understood.
CDMA is predominantly used in the U.S. (e.g., Verizon Wireless and Sprint PCS), Canada, and South Korea.
CDMA is also expected to be popular in emerging markets in mainland China.
How does TDMA work?
As discussed earlier, digital codes are methods for compressing information. TDMA, or Time Division Multiple
Access, primarily used in the U.S. and Canada, takes each call one short sound burst at a time and sends it out as
computer code. Each TDMA channel can carry code for snippets of several conversations simultaneously.
Currently, except for GSM and iDEN, TDMA can handle only voice calls, no data. In the U.S., a major TDMA
carrier is AT&T Wireless.
What is GSM?
GSM, or Global System for Mobile Communications, is the world’s most common digital technology for
mobile phones, especially in Europe (where it is the standard), Asia, and Africa. It is a form of TDMA that can
handle data. GSM carriers in the U.S. include Pacific Bell and Voicestream Wireless.
What is PCS?
PCS, which stands for Personal Communications Services, is a completely digital, wireless system that works in
the 1900 MHz frequency band. PCS protocols include CDMA, TDMA, and GSM.
What does it mean to be cellular?
Cellular technologies are named after the “cells” they use to distribute signal space within a specific coverage
area. In cellular networks, the entire coverage area is divided into multiple cells, and each cell is assigned a set
amount of signal space at any given time, usually about 1,000 frequencies. This space can be filled with analog
and/or digital messages, depending on what equipment is available.
Cellular networks are designed for voice transmission and typically charge according to the lapsed time of each
call, rather than the amount of information transferred. The term “cellular” especially refers to AMPS, an
analog protocol, but can also denote CDMA or GSM.
What is iDEN?
iDEN, or Integrated Dispatch Enhanced Network, is an enhanced version of TDMA used in the U.S., Canada,
Mexico, Israel, and parts of Asia and South America. In the U.S., the main iDEN carriers are Nextel and
Southern Linc.
What is CDPD?
CDPD, or Cellular Digital Packet Data, is something that can be added to a TDMA phone to allow data calls, so
you can perform computer-related applications like email, file transfers, or Internet browsing. Using CDPD
involves working with a CDPD account in addition to other accounts you may already have (e.g., email).
Without CDPD, a regular TDMA phone can handle only voice calls.
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