CDMA channels

In a North American CDMA (Code Division Multiple Access) system, voice and data are transmitted in a 1.23 MHz wide channel. This bandwidth results from the bit rate chosen for the pseudo-random spectrum broadening sequence. As shown in figure 2 , if the CDMA system is adjacent to another radiocommunication system, it is necessary to provide a guardband between the CDMA system and the other system. This guardband is defined as the minimum frequency band required so that the interference level created by a user of the neighboring system is less than the thermal noise of each CDMA receiver. The guardband depends on the type of neighboring system. For example, the proximity of an analog AMPS system requires a guardband of 0.54 MHz (i.e. 0.27 MHz at each end of the CDMA channel). A TACS system adjacent to a...