CDMAforcellularsystemscanbedescribedasfollows.AswithFDM A，eachcellisallocatedafrequency()，whichissplitintotwoparts,halfforreverse(mobileunittobasestation)andhalffor()(basestationtomobileunit).Forfull-duplex(本题).amobileunitusesbothreverseandforwardchannels.Transmissionisintheformofdirect-sequencespread(),whichusesachippingcodetoincreasethedatarateofthetransmission,resultinginanincreasedsignalbandwidth.Multipleaccessisprovidedbyassigning()chippingcodestomultipleusers,sothatthereceivercanrecoverthetransmissionofanindividualunitfrommultipletransmissions.
A.connection B.transmission C.compromise D.communication正确答案B
