CDMAforcellularsystemscanbedescribedasfollows.AswithFDM A，eachcellisallocatedafrequency()，whichissplitintotwoparts,halfforreverse(mobileunittobasestation)andhalffor(本题)(basestationtomobileunit).Forfull-duplex().amobileunitusesbothreverseandforwardchannels.Transmissionisintheformofdirect-sequencespread(),whichusesachippingcodetoincreasethedatarateofthetransmission,resultinginanincreasedsignalbandwidth.Multipleaccessisprovidedbyassigning()chippingcodestomultipleusers,sothatthereceivercanrecoverthetransmissionofanindividualunitfrommultipletransmissions.
A.forward B.reverse C.backward D.ahead正确答案A
