原文链接：http://www.cnblogs.com/nickchan/archive/2011/10/08/3104474.html

The naive digital communications layer: The first layer of the onion introduces the digital transmission of data, and discusses how bits of information may be coded into waveforms, sent across space to the receiver, and then decoded back into bits. Since there is no universal clock, issues of timing become important, and some of the most complex issues in digital receiver design involve the synchronization of the received signal. The system can be viewed as consisting of three parts: the transmitter,

digital message ->     coding ->    pulse shaping ->     frequency translation

the transmission channel, and the receiver

frequency translation -> sampling -> decision device -> decoding -> reconstructed message

转载于:https://www.cnblogs.com/nickchan/archive/2011/10/08/3104474.html