Pulse-code modulation

脉冲编码调制(Pulse Code Modulation,PCM)，由A.里弗斯于1937年提出的，这一概念为数字通信奠定了基础，60年代它开始应用于市内电话网以扩充容量，使已有音频电缆的大部分芯线的传输容量扩大24～48倍。到70年代中、末期，各国相继把脉码调制成功地应用于同轴电缆通信、微波接力通信、卫星通信和光纤通信等中、大容量传输系统。80年代初，脉冲编码调制已用于市话中继传输和大容量干线传输以及数字程控交换机，并在用户话机中采用。

在光纤通信系统中，光纤中传输的是二进制光脉冲“0”码和“1”码，它由二进制数字信号对光源进行通断调制而产生。而数字信号是对连续变化的模拟信号进行抽样、量化和编码产生的，称为PCM（Pulse-code modulation），即脉冲编码调制。这种电的数字信号称为数字基带信号，由PCM电端机产生。现在的数字传输系统都是采用脉码调制（Pulse-code modulation）体制。PCM最初并非传输计算机数据用的，而是使交换机之间有一条中继线不是只传送一条电话信号。PCM有两个标准（表现形式）即E1和T1。

中国采用的是欧洲的E1标准。T1的速率是1.544Mbit/s，E1的速率是2.048Mbit/s。

脉冲编码调制可以向用户提供多种业务，既可以提供从2M到155M速率的数字数据专线业务，也可以提供话音、图象传送、远程教学等其他业务。特别适用于对数据传输速率要求较高，需要更高带宽的用户使用。

 

中文名

脉冲编码调制

外文名

Pulse Code Modulation

简    称

PCM

发现者

A.里弗斯

发现时间

1937年

用    于

市话中继传输等 

PCM（脉冲编码调制）_百度百科 https://baike.baidu.com/item/PCM/1568054

Pulse-code modulation - Wikipedia https://en.wikipedia.org/wiki/Pulse-code_modulation

Modulation

 

Sampling and quantization of a signal (red) for 4-bit LPCM

In the diagram, a sine wave (red curve) is sampled and quantized for PCM. The sine wave is sampled at regular intervals, shown as vertical lines. For each sample, one of the available values (on the y-axis) is chosen by some algorithm. This produces a fully discrete representation of the input signal (blue points) that can be easily encoded as digital data for storage or manipulation. For the sine wave example at right, we can verify that the quantized values at the sampling moments are 8, 9, 11, 13, 14, 15, 15, 15, 14, etc. Encoding these values as binary numbers would result in the following set of nibbles: 1000 (= 2³×1+2²×0+2¹×0+2⁰×0 = 8+0+0+0 = 8), 1001, 1011, 1101, 1110, 1111, 1111, 1111, 1110, etc. These digital values could then be further processed or analyzed by a digital signal processor. Several PCM streams could also be multiplexed into a larger aggregate data stream, generally for transmission of multiple streams over a single physical link. One technique is called time-division multiplexing (TDM) and is widely used, notably in the modern public telephone system.

The PCM process is commonly implemented on a single integrated circuit generally referred to as an analog-to-digital converter (ADC).