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I think that you should learn Spread Spectrum first, since it is the basic theory for CDMA. You should say CDMA is only a kind of Communication protocol, like GSM which ultilizing TDMA method, also AMPS.
In Spread Spectrum, there are so many method to spread your carrier into wide bandwidth carrier, which almost embedded under noise floor.
1. Psuedo Code Spreading, e.g. BW of Carrier = 1/ T data rate, then if multiply very high data rate orthgonal code with data rate tc, then BW is spread
2. Frequency Hopping, which means your carrier is randomly appearing in particular Wide BW, making it like Spreading
3. Time Hopping, just randomly appears and disappears in time domain.
In Code Division Multiple Access (CDMA) systems all users transmit in the same bandwidth
simultaneously. Communication systems following this concept are "spread spectrum systems''. In this
transmission technique, the frequency spectrum of a data-signal is spread using a code uncorrelated
with that signal. As a result the bandwidth occupancy is much higher then required. The codes used for
spreading have low cross-correlation values and are unique to every user. This is the reason that a
receiver which has knowledge about the code of the intended transmitter, is capable of selecting the
desired signal.
A number of advantages are:
· Low power spectral density. As the signal is spread over a large frequency-band, the Power
Spectral Density is getting very small, so other communications systems do not suffer from this
kind of communications. However the Gaussian Noise level is increasing.
· Interference limited operation. In all situations the whole frequency-spectrum is used.
· Privacy due to unknown random codes. The applied codes are - in principle - unknown to a
hostile user. This means that it is hardly possible to detect the message of an other user.
· Applying spread spectrum implies the reduction of multi-path effects.
· Random access possibilities. Users can start their transmission at any arbitrary time.
· Good anti-jam performance.
i found this site very useful especially the thesis
**broken link removed**
A DS-CDMA demodulator prototype chip has been fabricated to demonstrate a passive analog integration technique that makes it possible to perform a high-speed correlation with minimal power. The prototype chip dissipates 75mW when operating at 128MHz.
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