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.

Key HSPA features and parameters

All High-Speed Packet Access (HSPA) -related features and parameters are 

described in detail in WCDMA RAN Parameter Dictionary.

The most important features and parameters from network planning point of view are 

presented here. For detailed information about features, see HSDPA-related feature 

documentation.

Table 5 HSDPA resource management functionality

HSDPA Basic functionality
In HSDPA Basic functionality, the features consist of QPSK and 5 HS-PDSCH codes, 
basic characteristics of the feature are listed below:
 • Maximum number of HSDPA users per BTS is 16
 • Maximum HS-SCCH codes per cell is 1
 • Maximum HS-PDSCH codes per cell is 5
 • Up to 3 cells per BTS can be enabled for HSDPA
In HSDPA Basic functionality the maximum allowed HSDPA power can be limited with 
PtxMaxHSDPA parameter. The recommended value for PtxmaxHSDPA depends on the 
HSDPA implementation strategy, HSDPA throughput targets, and Dedicated Traffic 
Channel (DCH) traffic load. For a shared HSDPA+DCH carrier the recommended 
HSDPA power is 4 - 7 W. For a dedicated HSDPA carrier the HSDPA power can be 10 
- 12 W when the maximum power of the Base Transceiver Station (BTS) is 20 W. 
Nokia Siemens Networks BTS utilises dynamic power allocation for HSDPA power, 
meaning that all available power is allocated to HSDPA when it is active until the 
maximum limited by PtxMaxHSDPA parameter.





The maximum HSDPA power should be selected so that the interference due to the 
HSDPA power does not cause severe degradation to the Real Time (RT) DCH and Nonreal Time (NRT) performance. The dynamic HSDPA power control makes the use of 
higher HSDPA power possible when the DCH traffic load is low. If the DCH load 
increases, the HSDPA power reduces dynamically. 
Figure HSDPA power allocation and load control thresholds with HSDPAPriority=1
shows the load and power control actions in case of HSDPAPriority=1. The 
PtxMaxHSDPA parameter defines the maximum power the BTS can allocate for the 
HSDPA. The HSDPA power is reduced when the required power for non-HSDPA connections increases and the total transmission power of the BTS reaches the maximum 
allowed Txpower. Preventive load control actions are started when the non-HSDPA 
power exceeds the PtxTargetHSDPA threshold. Overload control actions are started 
when the non-HSDPA power exceeds the PtxTargetHSDPA+PtxOffsetHSDPA
threshold. In case of HSDPAPriority=1, the overload actions are first targeted to the 
DCH NRT data bearers.

BTS maximum TX power is the cell maximum output power defined as minimum of the 
management parameter PtxCellMax and the BTS capability (indicated by 
MaxDLPowerCapability). 
In case of HSDPAPriority=2, the overload actions are first targeted to HSDPA power, 
as Figure HSDPA power allocation and load control thresholds with HSDPAPriority=2
shows.

Figure 12 HSDPA power allocation and load control thresholds with HSDPAPriority=2

A fixed number of five HS-PDSCH codes is reserved for HSDPA when it is enabled in 

cell.

Optional enhanced functionality

RNC applies HSDPA dynamic resource allocation if parameter 

HSDPADynamicResourceAllocation is set to ‘Enabled’. This enables the usage of 

dynamic NRT DCH scheduling and dynamic allocation of HS-DSCH codes. 

One option is that the HSDPA power is not limited by PtxMaxHSDPA, but BTS allocates 

all available power until BTS maximum TX power, which is the power defined as 

minimum of the management parameter PtxCellMax and the BTS capability (indicated 

by MaxDLPowerCapability). PtxCellMax can be used to limit the total power of the 

base station which limits also the downlink noise rise and enhances performance at cell 

edge areas. Another option is that PtxMaxHSDPA is used to limit the HSDPA power, 

which then avoids sudden power peaks already from one HSDPA user.

With dynamic NRT DCH scheduling the RNC uses an internal dynamic target 

PtxTargetPS for NRT DCH scheduling instead of fixed target like 

PtxTarget/PtxTargetHSDPA. This dynamic target is adjusted based on relative 

number and priority of HSDPA and NRT DCH users. The priority is defined by network 

planner separately for HSDPA (WeightHSDPA parameter) and NRT DCH (WeightDCH

parameter) users and also based on the bearer traffic class. 

The dynamic target PtxTargetPS is limited by minimum and maximum limits set by the 

network planner with PtxTargetPSMin and PtxTargetPSMax parameters. These 

can be used directly to limit the NRT DCH power and guarantee wanted power to 

HSDPA.

Nokia Siemens Networks RAN Optional feature set includes also HSDPA Dynamic 
Resource Allocation feature which is required to enable the usage of more than 5 HSPDSCH codes in a cell. HSDPA Dynamic Resource Allocation applied if:
 • HSDPA Dynamic Resource Allocation is activated/enabled 
(HSDPADynamicResourceAllocation management parameter)
 • Either HSDPA 10 Codes (HSDPA10Codes) or HSDPA 15 Codes (HSDPA15Codes) 
is activated/enabled
BTS must also be capable of 10/15 codes to dynamically adjust HS-PDSCH codes.
Maximum bit rate of HS-DSCH MAC-d flow
The maximum user bit rate of the HS-DSCH MAC-d flow used in the resource reservation for the HS-DSCH MAC-d flow is limited by the maximum bit rate based on User 
Equipment (UE) capability, the value of management parameter 
MaxBitRateNRTMACDFlow and by the maximum bit rate in RAB QoS parameters. 
The value of MaxBitRateNRTMACDFlow does not limit the maximum instantaneous bit 
rate on the air interface. The value of the parameter is compared to the user bit rate of 
the HS-DSCH MAC-d flow, excluding MAC-hs header, RLC header and padding. 
The maximum bit rate in RAB QoS parameters is checked only if management parameter HSDPAPeakRateLimitRABMax is set to value 1 (limitation is active). 
In RU10, one user L1 throughput can go up to 14.4 Mbps, which is possible with HSDPA 
UE category 10. Thus, it means that maximum bit rate of HS-DSCH MAC-d flow is 
around 14 Mbps. Notice that this is achieved with coding rate 1 which means that it 
requires error free transition and reception.