CDMA Means Code Division Multiple Access....
Though CDMA application in cellular telephony is relatively new, it is not a new technology. CDMA has been used in many military applications, such as anti- jamming (because of the spread signal, it is difficult to jam or interfere with a CDMA signal), ranging (measuring the distance of the transmission to know when it will be received), and secure communications (the spread spectrum signal is very hard to detect).
Spread Spectrum
CDMA is a “spread spectrum” technology, which means that it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal. The standard data rate of a CDMA call is 9600 bits per second (9.6 kilobits per second). This initial data is “spread,” including the application of digital codes to the data bits, up to the transmitted rate of about 1.23 megabits per second. The data bits of each call are then transmitted in combination with the data bits of all of the calls in the cell. At the receiving end, the digital codes are separated out, leaving only the original information which was to be communicated. At that point, each call is once again a unique data stream with a rate of 9600 bits per second. Traditional uses of spread spectrum are in military operations. Because of the Wide bandwidth of a spread spectrum signal, it is very difficult to jam, difficult to interfere with, and difficult to identify. This is in contrast to technologies using a narrower bandwidth of frequencies. Since a wideband spread spectrum signal is very hard to detect, it appears as nothing more than a slight rise in the “noise floor” or interference level. With other technologies, the power of the signal is concentrated in a narrower band, which makes it easier to detect.
Spread Spectrum
CDMA is a “spread spectrum” technology, which means that it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal. The standard data rate of a CDMA call is 9600 bits per second (9.6 kilobits per second). This initial data is “spread,” including the application of digital codes to the data bits, up to the transmitted rate of about 1.23 megabits per second. The data bits of each call are then transmitted in combination with the data bits of all of the calls in the cell. At the receiving end, the digital codes are separated out, leaving only the original information which was to be communicated. At that point, each call is once again a unique data stream with a rate of 9600 bits per second. Traditional uses of spread spectrum are in military operations. Because of the Wide bandwidth of a spread spectrum signal, it is very difficult to jam, difficult to interfere with, and difficult to identify. This is in contrast to technologies using a narrower bandwidth of frequencies. Since a wideband spread spectrum signal is very hard to detect, it appears as nothing more than a slight rise in the “noise floor” or interference level. With other technologies, the power of the signal is concentrated in a narrower band, which makes it easier to detect.
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