he Eb/No values on adjacent macro- cells should not exceed 75% in the DL and about 55% in the UL. On the other hand, microcells can probably take 65% UL and 85% loading, respectively. This means we need to apply the appropriate orthogonality factors when utilizing the load equations described generically in Section 7.6.5. The number of orthogonal codes also has impact on DL capacity despite a good propa- gation environment and good load sharing. The maximum number of orthogonal codes depends on the Spreading Factor (SF). For example, in general only one scrambling code and thus only one code three gets used per sector in the BS, where common and dedicated channels share the same three. On the other hand, the number of orthogonal codes does not imply complete 16 limitation when enabling DL capacity, because we can apply a 2nd scrambling code. However, the 1st and 2nd codes will not remain orthogo- nal to one another, and channels with the 2nd code interfere more with the channels with the 1st code. DIMENSIONING RNC INTERFACES When dimensioning the RNC lub interface, i.e. the connection between the Node B and RNC, we also consider the traffic mix in order to determine the number of RNCs re- quired. Thus, RNC interface dimensioning will take into account the number of Node Bs and the projected type of services with the forecasted subscribers and their traffic profiles [7]. Figure 7.9 illustrates the UTRAN interface configuration. 7.7.1 Dimensioning the lub The average traffic per Node B provide the total traffic based on the service mix statis- tics, the soft handover traffic and overheads, signaling and O&M traffic. Node B to CN Node B source traffic Node B softer HO soft HO Figure 7.9 The UTRAN interface configuration. The UMTS Network and Radio Access Technology Thus, to determine the total traffic passing through the Iub we consider first, the peak aggregate traffic mix calculated analytically taking into account the service parameters, e.g. the number of subscribers (Si), subscriber bit rate (R), session time l