分类： 系统运维
2010-06-01 10:51:17
自己想弄明白的，在网上找到了:
复用和多址的联系和区别在Glossory of Telecommunication Terms中的解释
multiplexing (MUXing): The combining of two or more information channels onto a common transmission medium.
multipoint(multiple) access: Access in which more than one terminal is supported by a single network termination.(比如一个基站支持多个移动台的情况)。
duplex operation: Operating method in which transmission is possible simultaneously, in both directions of a telecommunication channel.
由此可见，multiplexing翻译为“复用”较好；deplexing翻译为“双工”较好；multiple access翻译为“多址”不是很好，其实准确地讲应当是“多点接入”。
Medium与Resource也是应当区分的。
A typical characteristic of wireless communications is that the medium, that is, the air interface, must be shared among different applications (e.g., radio and television, mobile cellular systems, LANs), and within a certain application between different users (radio and television stations, subscribers).
Generally, a medium offers a number of resources each of which or a combination of which can be subdivided into several channels by the process of multiplexing.
在无线通信中，the medium is the air interfaces,the resource is SPACE，TIME，FREQUENCY，and CODE。
目前主要遇到的双工方式为：FDD与TDD.
主要的复用方式有：SDM,TDM,FDM,CDM.
主要的多址方式有：SDMA,TDMA,FDMA,CDMA.还有CSMA,ALOTHA。预约多址。
注意：SDM与SDMA中的M完全是不同的意思。看注一。
复用处理的是将媒介划分成子信道。在无线通信中，无线信道的划分可以从时间，空间，频率，码四个域进行。
The earlier analog cellular systems used pure FDM to separate different users, which was then called Frequency Division Multiple Access (FDMA).
TDM is often used to coordinate multiple access and is then denoted as Time Division Multiple Access (TDMA)
This principle can be utilized to coordinate the transmissions of
different senders, where each sender is assigned a particular code channel. This method is then called Code Division Multiple Access (CDMA).
某种程度上，SDMA,TDMA,FDMA,CDMA可以看作是SDM,TDM,FDM,CDM的应用。
在《Location Based Service Fundamentals and Operation》中关于复用与多址的解释
Multiplexing refers to the subdivision of a single medium into a number of channels that can be used independent of each other without interferences in data transmission. From the entire capacity of the medium, each channel is assigned a certain portion, which for digital data corresponds to the data rate the channel is able to realize and which must be carefully dimensioned in order to fulfill the requirements of the application using the channel. Multiple access, on the other hand, deals with the dynamic assignment of channels to users. It is necessary for all applications where users make use of channels only temporarily, as it is generally the case for all mobile communication systems. On the other hand, multiple access is not required for applications where channels are permanently assigned to users,like for radio and television broadcast stations.
复用与多址是两个完全不同的概念，复用是将单一媒介(medium)划分成很多子信道(subchannel)，这些子信道之间相互独立，互不干扰。从媒介的整体容量上看，每个子信道只占用该媒介容量的一部分。多址（exactly,多点接入）处理的是动态分配信道给用户。这在用户仅仅暂时性地占用信道的应用中是必须的，而所有的移动通信系统基本上都属于这种情况。同时，在信道永久性地分配给用户的应用中，多址是不需要的（对于无线或者电视广播站就是这样）。
归结起来：复用是将medium划分成channel(subdivision)，而多址处理的是channel的动态分配(dynamic assignment)，这里动态很重要。
PCM系统就是一个时分复用系统，但之中却没有时分多址的概念。
关于双工总结如下：
FDD方式：simultaneous but need a duplexing unit(expensive & cannot be integrated).
TDD方式：quasi-simultaneous no duplexing unit is required.
在GSM系统中，系统包含了FDD（上下行分离）和TDD(上行比下行滞后3 time slots)，因此GSM手机不需要自己的高频双工单元，这降低了成本和能耗。
复用是对资源来说的，复用分时分、频分、码分等，复用是把资源分割供用户使用的方式
多址的对象是用户，是区分用户和用户的方式，每个用户使用不同的‘址’来区分
简单来说，多址肯定要复用，不同用户必须占用不同的资源才能区分开来；但复用不一定多址，单个用户可以同时占用多个资源进行接收，比如在GSM或3G中一个用户占用多个频道、多个码道或多个时隙来提高传输速率就还是复用的概念
自己的想法：
复用，汉语词典意思是重复运用。把multiplex翻译成复用，感觉有点不妥。multiplex并不是真正的重复使用。比如说FDM，并不是重复使用同一个频率段，而是每个用户占据一定的带宽，带宽是不重叠的。可以说是复用了整个带宽。但并不是频率复用。
真正的频率复用，比如说蜂窝系统，这个就是频率的重复使用了~干扰足够小的2个小区是使用相同的频率段的~
可以把这种译法当做是约定俗成。
就像Pulse Code Modulation（脉冲编码调制），其实并不是一种调制方式，而是一种模拟到数字的转换方法。
欢迎补充。 ^_^
注一：
空分复用(SDM，Space Division Multiplexing)即多对电线或光纤共用1条缆的复用方式。比如5类线就是4对双绞线共用1条缆，还有市话电缆(几十对)也是如此。能够实现空分复用的前提条件是光纤或电线的直径很小，可以将多条光纤或多对电线做在一条缆内，既节省外护套的材料又
本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/faicker/archive/2007/12/13/1933731.aspx
