?????????? ?????????? ??????? ??????? (?)

???????? ????????????? ???????????? ????????? ?????????? Digital communication ?????????? ?????????????? ??? ??????????? ???????? ???????? ??????? ????????? ?????????????? ?????? ?????? ???????????? ??????? ?????????????? Analog - ?????????????????? ?????????? ????????????????? ??????????? ???????? ???????????????? ????????????? ???????? ???????? ??????????????????? ??????? ?????????????????? ???????????????? ???? ??????? ?????????????????? ???????? ?????????? ??????????? ??????????????? ???????? ????????????(distortion) ? ?????????? ?????? ???????? ??????????????? (interference) ?????? ???????????? ??????????????? ?????????? ??????????? ?????????? ?????????????? ????????? ???????????????? ????? ?????????????? ???????????????????? ?????????????????????? ???????? ?????? ?????????? ????????????????????????? ??????????? ???????????????

DCS ??? ????????? ????????? ????? ????????? (imformation) ??? ?????????????????? (bits) ????????????????????????? process ??? formatting ????????????????? process ????????? bits ?????? ????????????????? digital messages (????) message symbols ????????? ????????????? ????? ?????? message symbol m_i(i=1..M)?????????? M member ?????????????? ??????? alphabet ??????????? ??????????? ??????????????????[????? m-i ???????????????????????? ?????????????????????????????????????????????? ?????????????? ??????????????? ???????????????????????????] ???????????? M ? ? ???????????????? message symbol ?? ???????????????? (????????????? ???? message symbol ??? bit ??????????????????????????? ???????? M ?? ? ???????????????????? symbol ????? bit ???????? ? ??????? ????????????????????? channel code (error correction code) ?????????????? ????????????????? ?????? ????? message symbols ?????? sequence ??? channel symbols ?????? sequence ????? ?????????????? ???????????? ???????????????? ????????? bits ?????????? ???????????? ?????????? transmission channel ????????????????????? ??????????? transmission channel ???????????????? modulation ??????????? pulse modulation ????? ??????????????? ( voltage level 0 or 1) ??? ???????? ??????? baseband waveform ???????????????????????? baseband waveform ????? spectrum ??????? frequency 0 Hz ????????? ???????????MHz ????????? signal ??????????????????? RF transmision ?????????????? ?????????????? bandpass modulation ?????????????? transmission medium (channel,etc) ? pulse-like waveform??? ???????????????? ?????????????????????????? bandpass modulation ??????????? ?????????????medium( channel ) ?? bandpass waveform ????????????????? bandpass ??? frequency spectrum ?? baseband frequency spectrum ????????????? source coding ????? ???????????? ?????????? (A/D) ??? ?????????????????? ?????????? ????????????????? ??? ??????????????? Encrypt ????? ????????????????? ??????????????? ???????????????? ???????? ???????????????????? ?????????????????? ????????? ?????????????????? channel coding ?????????????? ???? rate ????????? ?????????????????? ????? (probability of error) ??? ?????????????? multiplexing ??? multiple-access ????? ???????? source ?????? ?????????????????? signals ?????? ??????????????? ???????????? ?? communications resource (spectrum,time ) ??? ?????????????? ???????????????????? frequency spread ????? ???? ???????????????? ??????? ??????????????????? ????????????? signal ??? ???????????? ?????????? ??????? ??????????? ??????????????? ?????????????? source coding , encrypt, channel coding, multiplexing and multiple-access ???????? ?????????????????????????? ??????????
Reciver ?????????????? transmitter ?????????? ?????????????????? bandpass waveform ??? demodulator ??? baseband waveform ?????????????????????????detection ????? ?????? baseband waveform ??? binary bit ?????? ??????? ????????????? ?????????????????????????????????????? DCS ????????????????????????????????? DCS ??????????????? ?????? ?????????? ?????????????? ????????????????????????