or other places. This means that in cellular networks the interface between the ME and BTS involves transmission. Obviously when talking here about transmission optimisation that type of transmission is not meant. The optimising interface between ME and BTS is discussed in other chapters. That case is just one example to highlight where transmission optimisation might not be a very good expression to use because it is SO vague. Therefore an agreement is needed here to define the scope. Let the agreement be that what is meant by transmission in this context is the use of a data transport system between access network elements and core network elements. The data transport system can be dedicated to this purpose but it can also be used for several different purposes, data transport for the cellular network being only one of them. There is one important remark to be made concerning this agreement. It quite clearly shows that network services and data transport services should be considered as two separate systems, which are only part of a section. The section can be complete from the data transport network viewpoint if it has no other purpose than serving the 3G network, but the section can also be incomplete if the trans- port network is also used for some other purpose or purposes that have nothing to do with the 3G network. Transmission Network Optimisation The importance of this is that reference to the 3G network actually loses most of its significance in this context. The transmission optimisation in 2G networks or in some other type of network would actually have the very same principles. Of course, the 3G network has certain characteristics that specify what kind of transmission network can provide the data transport service for it, but that has relatively little effect on the main optimisation principles. It can also be said that the 3G network is specified SO that the expectation is for 'perfect enough' data transport between the network elements. In other words, the expectation is that from the 3G system v