quency hopping is a way to use a given frequency spectrum more efficiently. It makes the interference spread on the whole network instead of being localised in the case of fixed frequency allocation. This solution is especially adequate in urban areas. The rural environment is noise limited; this means that a tight frequency re-use is not needed. The re-use distance is large, SO there is no interference. Uplink and Downlink Power Control Power control in the uplink and downlink is the mechanism where the powers of the mobile station and the base station are monitored. Depending on the distance between the two stations, they are asked to increase or decrease their power. This also helps to reduce the overall interference in the network. Smart Antenna This is a switched beam system where MS hand-offs are between antenna beams rather than sectors. Network Physical Extension Instead of adding new sites, it is possible to increase the capacity of existing sites by adding other transceivers. Dual Band Network Using another frequency band is also an efficient way to separate traffic load. The majority of handsets can use GSM900 or DCS1800 bands. The traffic management between the two bands is done like a multilayer handling in GSM. Thresholds and decision parameters move the hand-offs from one band to another. Half Rate In a normal case, one communication requires one timeslot in the TDMA frame at 13 kbps speech coding. One timeslot can be used to carry two traffic channels at lower bit rates. This allocation is called a half rate. The idea is to remove user data in order to fit two parallel communications in the same physical channel. This has an impact on audio quality, which in the worst case is a matter of a half-rate mobile to half-rate mobile communication. Radio Network Planning and Optimisation Channel coding Speech coding Error Protection (FER) Speech Quality (MOS) AMR codec mode Figure 2.65 AMR tradeoff Radio Performance Increase Sectorisation and cell splitting are methods to enhance capacity for the macro ce