HSDPA mobility


The HSDPA mobility handling takes care of the data connection mobility when the 
HSDPA is active for the connection. This functionality can be enhanced by optional 
enhanced functionality.

HSDPA Basic functionality
If the parameter HSDPAmobility has value disabled, the HSDPA mobility is handled 
by HSDPA cell reselection and DCH switching. 
HSDPA cell reselection is triggered by measurement event 1A, when the UE enters the 
SHO area. The reselection applies transitions to CELL_FACH, cell re-selection and reallocation of HSDPA. The measurement event 1A can be configured with the 
AdditionWindow parameter, defined in the FMCS parameter set that is selected by 
HSDPAFMCSidentifier or RTwithHSDPAFMCSidentifier parameters.
Switching to DCH is triggered by measurement events 1F and 6A. They also trigger 
directly the IFHO/ISHO measurements when HSDPA+AMR multi-RAB is used. Direct 
switching from HSDPA to DCH initial bit rate is used when possible.



Optional enhanced functionality
The optional enhanced functionality enables the usage of HSDPA Serving Cell Change 
and HSDPA Soft/Softer Handover for Associated DPCH. This feature is activated by 
setting the parameter HSDPAmobility to value Enabled. An active license is required 
for this feature. 
The HS-DSCH serving cell change feature is controlled with several planning parameters. There are feature-specific parameters to set thresholds for the Ec/No and UL SIR 
error triggering and the required level in a target cell. In addition to the feature-specific 
parameters, AdditionWindow and DropWindow parameters in the HSDPA FMCS 
parameter set are used to control the serving cell change and the SHO area for the 
associated UL channels. 
The HS-DSCH serving cell change feature can be triggered by the best server Ec/No, 
UL SIR error, and event 1B/1C. The most common triggering reason is the periodical 
Ec/No measurements. The HSDPAServCellWindow parameter determines the 
maximum allowed difference between the best cell Common Pilot Channel (CPICH) 
Ec/No and the serving HS-DSCH cell CPICH Ec/No. It is recommended to set the 
DropWindow parameter higher than the HSDPAServCellWindow, so that the serving 
cell change is normally triggered by the Ec/No measurements and not by the event 1B. 
The AdditionWindow in the HSDPA Intra-Frequency Measurement Control (FMCS) 
controls the active set size of the associated UL channels. It does not have direct impact 
on the serving cell change functionality and triggering. However, the used High-Speed 
Dedicated Physical Control Channel (HS-DPCCH) power offsets for the Channel Quality 
Indicator (CQI) and HARQ Ack/Nack are higher during the SHO of the associated channels. It is recommended currently to set a lower value for the AdditionWindow parameter in HSDPA FMCS than in the RT/NRT FMCS, to have a smaller SHO area for the 
HSDPA users. 
Switching to DCH is triggered by measurement events 1F and 6A also with enhanced 
functionality. They also trigger directly the IFHO/ISHO measurements when

HSDPA+AMR multi-RAB is used. Direct switching from HSDPA to DCH initial bit rate is 
used when possible. 
The measurement control and handover path parameter sets, which are dedicated to 
the UE having HS-DSCH transport channel allocated, are applied to the intra-, inter-frequency, and inter-RAT measurement types. The separate, HSDPA-specific and RT with 
HSDPA multi-RAB, measurement control and handover path parameter sets are determined for the following parameter object classes:
 • FMCS (intra-frequency measurement control)
 • FMCI (inter-frequency measurement control)
 • FMCG (inter-system measurement control)
 • HOPS (intra-frequency handover path)
A particular parameter set is associated with the HSDPA UE by the following identifiers: 
HsdpaFmcsIdentifier, HsdpaFmciIdentifier, HsdpaFmcgIdentifier, 
HsdpaHopsIdentifier. 
The Radio Network Planning (RNP) parameters can be adjusted by the operator.