●CDMA for cellular systems can be described as follows.AS with FDMA,ech cell is allocated a frequency（71）,which 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 uses both reverse and forward channels.Transmission is in the form of direct-sequence spread(74),which uses a chipping code to increase the data rate of the transmission,resulting in an increated 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 transmission.

      （71）A.wave

      B.signal

      C.bandwidth

      D.domain

      （72）A.forward

      B.reverse

      C.backward

      D.ahead

      （73）A.connection

      B.transmission

      C.compromise

      D.communication

      （74）A.structure

      B.spectrun

      C.stream

      D.strategy

      （75）A.concurrent

      B.orthogonal

      C.higher

      D.lower

      【参考答案】C A D B A