st, because they, as everyone else, know that there needs to be 'field' to be able to make a connection. They cannot monitor the transmission network in the same way. This last part means that the radio interface has had a lot of publicity, partly perhaps because it is now the new 'thing' in cellular networks compared to fixed line services. It does not mean that the general public would know much about radio propagation, not at all, but since everyone carries a device capable of measuring the field strength, it is quite human for many people to act as if they were experts. On the other hand, radio propagation is SO complex, three-dimensional and literally in the air that even real experts can have only an estimate about the reality. Therefore everyone is qualified to have an opinion. However, the same does not apply to transmission. The main causes of accessibility problems in transmission are congestion in signalling links or congestion in the user traffic channel. Transmission Signalling Congestion in 2G signalling links has now been in focus from the very end of the 1990s because the number of different types of services that use those signalling links has exploded and transmission network planning, which was done in many cases in the mid-1990s, was definitely not done for such a scenario. As 6 kbps signalling links have been widely used they are now in danger of becoming congested. Therefore around the world operators have lately been changing signalling links from 16 kbps to 64 kbps for most critical base stations. In 3G there is already much more uncertainty in the first place since no one yet has a firm idea of how these networks will evolve or what services will break through in addition to traditional 2G services. That is why dimensioning the signalling links is a very challenging task. Simulations have been made, but depending on the selected services very different kinds of results can be achieved. As a rough guideline 10% of user traffic for signalling is frequently seen. That maps quite well to 16 k