TABLE OF CONTENTS In the 1980s, the co-founder of the American firm Qualcomm, Andrew Viterbi, revealed that the capacity of a CDMA ( Code Division Multiple Access) system was up to 20 times greater than that obtained in analog mobile communication systems. This announcement surprised the scientific community as well as the telecommunication manufacturers: they believed that a new and revolutionary age in the mobile communication arena had just begun. At first they were disappointed since in theory that was proved to be true but in real-life networks the performance of CDMA was quite limited - the first commercial mobile communications network based on CDMA was deployed in 1995, i.e. five years after the first deployment of GSM in Europe.
Despite its late entrance in the mobile communications scene, CDMA technology seduced numerous operators and manufacturers. Supported by the USA, Europe and Japan, CDMA was adopted by most 3G systems in the IMT-2000 framework, including UTRA technology. This chapter studies the key ideas behind CDMA as well as the technical background of the spreading techniques for use in direct sequence CDMA cellular networks.
CDMA can be seen as an application of spread spectrum, enabling multiple access communication within the same frequency band - the users are divided by different spreading codes. Spread spectrum is defined as a transmission technique in which a code sequence, independent of the information data, is employed as a modulation waveform to "spread" the signal energy over a bandwidth much greater...
