Soft handover refers to the intra-frequency handover, but not all intra-frequency handovers are soft handovers. If the target cell and the former cell have the intra-frequency but belong to different RNC, and there is no Iur interface between RNCs, the intra-frequency hard handover will occur. Besides, the internal code handover in the same cell is also hard handover. Inter-system hard handover consists of the handover between FDD mode and TDD mode, the handover between WCDMA system and GSM system in R99, and the handover between WCDMA and cdma2000 in R4.
The startup compress mode is required to measure inter-frequency and inter-system for inter-frequency hard handover and inter-system hard handover.
- Intra-frequency neighbors can be measured simultaneously with normal transmission by UE using a RAKE receiver.
- Inter-frequency or inter-system neighbors measurements require the UE measuring on a different frequency, this has either to be done with multiple receivers in the UE or in the compressed mode.
- CM is to stop the normal transmission and reception for a certain period of time, enable the UE to measure on the other frequency.