Let's see what we really mean by multiple access. The multiple access implies that a common facility is required to be accessed by a large number of users. They could be broadcast transmission media, a large number of users want to transmit through that medium, for example a satellite. Many people want to use the satellite for communication needs, and therefore they want to access the satellite.
In case of the cellular mobile communication all the users in a particular cell, they want to access a particular base station. And, similarly, you can take the example of telephone exchanges, telephone central offices where a large number of users they first access the exchange, then dial and get the destination and start communication. Thus many users want to access, and if that is so then we have to think about the resources which are available at our command. And these resources in case of electrical signals happen to be: of course, space, where you can lay cables; you have frequency, that is the spectrum, and the third is a time, or a time-frame, or a time-interval. But if you want to make the best use of the resources, because they are limited always in nature, and the number of users always keep on increasing, you have to make an efficient use of these resources, for which naturally you require control algorithms.
Of course objectives of those algorithms controls should be to give you maximum throughput, a large number of users communicating large volume of information, and secondly the minimum waiting time, not that a particular user has to wait for a long time to get access to the common facility. Once again the local area networks use multiple access techniques, base stations in cellular mobile telecommunications require multiple access techniques, then communication satellites require multiple access techniques and, similarly, the telephone centres and telecommunication centres require the multiple access techniques.
