ding, and the parameter to describe this is the loading factor. Owing to this loading, degradation in the link budget takes place, also known as interference degradation. If the loading factor is a, then the interference degradation margin can be calculated as: L=10log(1-a) (7.1) Theoretically, the parameter a may vary from zero to 100%, but practically it is in the range 40-50%. The principle of the load factor is similar for uplink and downlink power budgets, but the parameters are different. In the downlink power budget, an orthogonality factor needs 3G RADIO NETWORK PLANNING AND OPTIMISATION to be considered as well. As we saw at the beginning of this chapter, mobile subscribers are assigned codes and each of these codes is orthogonal to each other. Orthogonality of the codes is maintained only in direct propagation conditions, which is usually not experienced as there will always be some degree of multipath propagation. This will cause a delay in the signal and the mobile will treat some part of the incoming signal as an interference source. A perfect orthogonality would mean unity, while practically it may vary anywhere between 0.4 and 1.0. Propagation Model The propagation models described in Chapter 2, such as Okumara-Hata, - Walfish-Ikegami etc., are valid for WCDMA radio networks too. As in GSM networks, the correction factor procedure also needs to be followed. Link Budget Anexample of an uplink and downlink power budget is shown in Table 7.5. The fundamental principle remains the same as described in Chapter 2. However, in WCDMA radio networks the link budget calculations need to be done individually for voice and various data rates (e.g. 64 kbps, 144 kbps, 384 kbps) for a certain load (50% in this example) and for different applications. 7.5.9 Capacity Planning Compared with GSM radio networks, capacity analysis finds itself more than ever dependent upon the coverage. The uplink and downlink coverages are quite different in a WCDMA radio network. The downlink coverage decreases with an increase in th