1.异步和同步传输 (1)异步传输 1)概念 In asynchronous transmission, each character of data is treated independently. Each character begins with a start bit that alerts the receiver that a character is arriving. The receiver samples each bit in the character and then looks for the beginning of the next character 2)方法 The strategy with this scheme is to avoid the timing problem by not sending long, uninterrupted streams of bits. Instead, data are transmitted one character at a time where each character is five to eight bits in length. Timing or synchronization must only be maintained within each character; the receiver has the opportunity to resynchronize at the beginning of each new character 3)工作过程 (Please see Figure 6. 1 in Page 176, E6, Next slide) 4)优缺点 优点:仅需一条信道,且传输距离较远 缺点:额外开销较大(约20侧络通信网络通信 3 1. 异步和同步传输 （1）异步传输 1) 概念 In asynchronous transmission, each character of data is treated independently. Each character begins with a start bit that alerts the receiver that a character is arriving. The receiver samples each bit in the character and then looks for the beginning of the next character. 2) 方法 The strategy with this scheme is to avoid the timing problem by not sending long, uninterrupted streams of bits. Instead, data are transmitted one character at a time, where each character is five to eight bits in length. Timing or synchronization must only be maintained within each character; the receiver has the opportunity to resynchronize at the beginning of each new character. 3）工作过程 （Please see Figure 6.1 in Page 176, E6, Next slide） 4) 优缺点 优点：仅需一条信道，且传输距离较远； 缺点：额外开销较大（约20%）