1.时分多址(TDMA):
TDMA是信道化协议,其中,信道的带宽在时间的基础上被划分为多个站。每个站都有一个时隙,该站只能在该时隙内发送数据,如下所示:
每个站必须知道其时隙的开始和时隙的位置。 TDMA需要不同站之间的同步。它是数据链路层中访问方法的类型。在每个站点,数据链路层会通知站点使用分配的时隙。
2.码分多址(CDMA):
在CDMA中,所有站都可以同时发送数据。它允许每个站点始终在整个频率上传输数据。多个同时传输被唯一的代码序列分隔。每个用户都分配有唯一的代码序列。
在上图中,有4个标记为1、2、3和4的站。分配给各个站的数据分别为d 1 ,d 2 ,d 3和d 4 ,分配给各个站的代码为c 1 ,c 2 , c 3和c 4 。
TDMA和CDMA之间的区别:
S. No. | TDMA | CDMA |
---|---|---|
1. | TDMA stands for Time Division Multiple Access. | CDMA stands for Code Division Multiple Access. |
2. | In this, only the sharing of time of satellite transponder takes place. | In this, there is sharing of both i.e. bandwidth and time among different stations takes place. |
3. | There is no need of any codeword. | There is no need of any codeword. |
4. | In this, guard time of the adjacent slots are necessary. | In this, both guard bands and guard time are necessary. |
5. | Synchronization is required. | No need of synchronization. |
6. | There is average capacity of the system. | There is large capacity of the system. |
7. | It is less flexible than CDMA. | Flexibility is high. |
8. | In this, there is no Near-far problem. | There is existence of Near-far problem. |
9. | Rate of data is average. | Rate of data is high. |