Что является CDMA (Разделение Кодекса Многократный Доступ) ? (WinWord 97)

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What is CDMA (Code Division Multiple Access?
One of the most important concepts to any cellular telephone system is that of "multiple access", meaning that multiple,
simultaneous users can be supported. In other words, a large number of users share a common pool of radio channels and any
user can gain access to any channel (each user is not always assigned to the same channel. A channel can be thought of as
merely a portion of the limited radio resource which is temporarily allocated for a specific purpose, such as someone's phone call.
A multiple access method is a definition of how the radio spectrum is divided into channels and how channels are allocated to the
many users of the system.
Current Cellular Standards
Different types of cellular systems employ various methods of multiple access. The traditional analog cellular systems, such as
those based on the Advanced Mobile Phone Service (AMPS) and Total Access Communications System (TACS) standards,
use Frequency Division Multiple Access (FDMA. FDMA channels are defined by a range of radio frequencies, usually
expressed in a number of kilohertz (kHz), out of the radio spectrum. For example, AMPS systems use 30 kHz "slices" of
spectrum for each channel. Narrowband AMPS (NAMPS) requires only 10 kHz per channel. TACS channels are 25 kHz wide.
With FDMA, only one subscriber at a time is assigned to a channel. No other conversations can access this channel until the
subscriber's call is finished, or until that original call is handed off to a different channel by the system. A common multiple access
method employed in new digital cellular systems is the Time Division Multiple Access (TDMA. TDMA digital standards include
North American Digital Cellular (know by its standard number IS-54), Global System for Mobile Communications (GSM), and
Personal Digital Cellular (PDC. TDMA systems commonly start with a slice of spectrum, referred to as one "carrier". Each
carrier is then divided into time slots. Only one subscrib

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