ink and Downlink Spreading Both uplink and downlink spreading are based on channelisation codes. The dedicated channel spreading factor variation is on a frame-by-frame basis in the uplink, while in the downlink it is not SO except for the DSCH (downlink shared channel) that may use the variable spreading factor on a frame-by-frame basis. Uplink scrambling uses complex sequences of spreading codes. In the uplink there are two spreading codes, long and short, while in the downlink only long spreading codes are used. Long codes have a frame length of 10 ms, which means that a chip rate of 3.84 Mcps will result in 38 400 chips, whereas short codes have a length of 256 chips. As there are many spreading codes, a network planning tool should be used. Usually, only one scrambling code is used per sector in the downlink direction, as orthogonality between the channels (and users) needs to be maintained. Bad code planning will lead to less orthogonality and thus more interference, resulting in less coverage and capacity. 7.5.5 Code Planning Owing to the spreading phenomenon, scrambling and channelisation code assignment be- comes necessary. Uplink code allocation for both scrambling and channelisation is done by the system. As there are 64 code groups used in the downlink direction, having 8 codes each (i.e. a total of 64 X 8 = 512 codes), each cell that the user equipment has connectivity to should be assigned a different code. This brings a re-use factor of 64, which is quite high, making the cell search process less complicated. The high re-use factor also means that the code planning can be done manually. 7.5.6 Power Control Fast power control tied with a high level of accuracy is an essential feature of WCDMA radio networks. As the frequency re-use factor is 1, SO fast and accurate power control becomes even more essential. The reason is that, in the absence of a power control feature, the mobile station that is nearest to the base station can easily 'overshout' the other mobiles that are handled by the cell, thereb