While spread spectrum techniques had been used for many years in military circles, and then primarily for covert communications systems, it was not until 1989 that the idea of using direct sequence spread spectrum techniques in the form of a code division multiple access scheme was proposed to the Telecommunications Industry Association in the USA. As there was already another second-generation technology being developed, the industry did not want competing technology to be introduced. Accordingly, the first CDMA networks were not launched in the USA, from where the idea had emanated. Instead the first network was launched in Hong Kong in 1994, with the first network in the USA being launched in 1996.

The idea of using direct sequence spread spectrum techniques to provide an access technology was quite revolutionary. It was a major leap in technology over the original FDMA schemes used for the first-generation networks, and also the TDMA systems being rolled out as GSM, initially in Europe, and the NA-TDMA system being rolled out in the USA. It relied heavily on the much greater levels of digital signal processing power that were coming and as such formed a significant development in the approach used for mobile communications.

As described in Chapter 3, CDMA relies on the use of different orthogonal spreading codes to differentiate between the different mobiles accessing the system. Although the signals all occupy the same frequency channel, the system is able to decipher each signal by applying the correct code to correlate the incoming...