CDMA for cellular systems can be described as follows. As with
FDMA， each cell is allocated a frequency (本题) ，which is split into two parts, half for reverse (mobile unit to base station) and half for ( ) (base station to mobile unit). For full-duplex ( ) . a mobile unit uses both reverse and forwardchannels. Transmission is in the form of direct-sequence spread ( ) , which uses a chipping code to increase the data rate of the transmission, resulting inan increased signal bandwidth. Multiple access is provided by assigning ( ) chipping codes to multiple users, so that the receiver can recover the transmission of an individual unit from multiple transmissions.
