CDMAforcellularsystemscanbedescribedasfollows.AswithFDM A，eachcellisallocatedafrequency()，whichissplitintotwoparts,halfforreverse(mobileunittobasestation)andhalffor()(basestationtomobileunit).Forfull-duplex().amobileunitusesbothreverseandforwardchannels.Transmissionisintheformofdirect-sequencespread(本题),whichusesachippingcodetoincreasethedatarateofthetransmission,resultinginanincreasedsignalbandwidth.Multipleaccessisprovidedbyassigning()chippingcodestomultipleusers,sothatthereceivercanrecoverthetransmissionofanindividualunitfrommultipletransmissions.
A.structure B.spectrum C.stream D.strategy正确答案B
