CDMA for cellular system can be described as follows. As with FDMA, each cell is allocated a frequency （71） , when is split into two parts, half for reverse (mobile unit to base station) and half for （72） (base station to mobile unit). For full-duplex （73） , a mobile unit both reverse and forward channels. Transmission is in the form. of direct-sequence spread （74） , which used a chipping code to increase the data rate of the transmission, resulting is an increased signal bandwidth. Multiple access is provided by assigning （75） chipping codes to multiple users, so that the receiver can recover the transmission of an individual unit from multiple transmissions.