llocation of resources, it knows simultaneously are disadvantageous is lower the larger the fraction of the channelization code tree not reserved the number of cells in the active set. for any user. Measurements in the NodeB provide the Uplink soft handover implies the transmission from RNC with information about the average amount of the UE are received in multiple cells. The cells can often available transmission power. belong to different NodeBs. Reception of data at multi- In the uplink, thanks to its non-orthogonal nature, ple locations is fundamentally beneficial as it provides there is no channelization code limitation. Instead, the diversity against fast fading. In case the cells receiving the resource consists of the amount of additional interference 1 Formally, the selection and duplicate removal mechanisms in case of inter-NodeB macro diversity are part of the physical layer. Hence, the physical layer spans both the NodeB and the RNC. WCDMA evolution: HSPA and MBMS CHAPTER 4.6 the cell can tolerate. To quantify this, the term noise rise or corresponding to the smallest spreading factor that may rise-over-thermal is often used when discussing uplink be required during the session. Similarly, in the uplink, operation. Noise rise, defined as (I0 + No)/No, where I the RNC must ensure that the maximum interference in and No are the power spectral densities due to uplink the cell is not exceeded even if the UE transmits at its transmissions and background noise, respectively, is highest data rate. a measure of the increase in interference in the cell due to During the packet-data call, the data rate of the the transmission activity. For example, 0 dB noise rise transmission may vary, depending on the traffic pattern. indicates an unloaded system (no interference from other As a consequence, the transmission power will vary users) and 3 dB noise rise implies a power spectral density depending on the instantaneous data rate. However, the due to uplink transmission equal to the noise spectral amount of the code