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Nokia Siemens Networks – 3G Uplink OptimizationNSN response to Annex 6, Chapter 5 in T-Mobile Netherlands Single RAN RfQ
NSN response to Annex 6, Chapter 5 in T-Mobile Netherlands Single RAN RfQSeptember 2011
Introduction
TargetTarget
This presentation is intended to provide response to Annex 6 Chapter 5 in T-Mobile Netherlands Single RAN RfQ where the Supplier is requested to provide an overview of measures taken to reduce the radio and baseband/RNC resource allocation in a high smartphone penetration environment with extremely high signaling load.
All information related to the Nokia Siemens Networks 3G Uplink Optimization features, functionality’s and roadmaps presented in this document are strictly Nokia Siemens Networks Customer confidential.
No information shall be disclosed to any third party without permission from Nokia Siemens Networks.
Uplink vs Downlink Traffic in Live 3G Networks (1)
Europe 2
South America
Europe 1
0.25
0.20
0.15
HSUPA / HSDPA daily volume ratio at selected operators
• It is possible to improve the situation because we are not hitting any fundamental theoretical limit. The limit is ”only” system protocol design and configuration. There are already promising indications since RU20 ontop releases have stabilized the uplink in many networks.
• NSN uses interference based uplink RRM while some RAN vendors use throughput based solution (number of users). The interference based solution has the benefit that cell breathing can be controlled. But interference based solution requires also careful control of the uplink interference sources to provide optimal performance.
NSN Solutions for Uplink Interference Control – Summary
• Candidate prioritization and bit rate selection in PBS
• R99 Overload Control procedure
• Downgrading the PS NRT DCH for the soft handover branch addition congestion handling
• PRFILE parameter control for triggering the channel type switching from the SIR error
• Limited value of UL DPCCH power offset for the first RL setup in the RTWP spiking cell
• Power based Admission Control for the HSUPA call setups
• Correction in updating the the MIN and MAX PRXTOTAL counters of the Received Rel99 wideband power measurement
Dynamic Initial Bit Rate Allocation
• Allows more PS NRT users admitted at initial and minimum bit rates in and keep the existing PS NRT users longer in the CELL_DCH state.
• High bit rate PS DCH users are selected first for downgrade, the QoS priority is applied only when the PS calls of the cell are not using higher than the initial DCH bit rates
• PBS candidates will be prioritized in all congestion cases as follows:
• PS NRT DCHs users having higher bit rate than initial bit rate users, in the QoS priority order.
• PS NRT DCHs users having higher bit rate than minimum bit rate users, in the QoS priority order.
• PS NRT DCHs users having higher bit rate than minimum bit rate users, in the QoS priority order.
• Finally the minimum bit rate users, in the QoS priority order.
• Initial/minimum DCH bit rate selection of the PS call triggered the PBS:
• New functionality applies to the UL interference, DL power and UL load congestion.
• If BRM detects congestion and the PBS triggers, then:
• If high bit rate (higher than initial) PBS candidates are available, then the incoming user gets the initial bit rate
• If only low bit rate (lower or initial) PBS candidates are available, then the incoming user gets the minimum bit rate.
Downgrading NRT DCH in Soft Handover Congestion
• Present implementation does not allow the downgrading of the DCH bit rates of the PS bearers if a congestion occurs in the soft handover branch addition. If the target cell is better than the ones in the active set, the failed soft handover may cause significant spiking of the RTWP, unless the PS DCH is removed.
• In the new implementation, the PS DCH is downgraded to the minimum bit rate and then attempted the branch addition once more.
• If the congestion occurs still, the UE is switched to CELL_FACH state without applying the management parameter EnableRRCRelease. If the UE has also the AMR, the PS bearers are
management parameter EnableRRCRelease. If the UE has also the AMR, the PS bearers are downgraded to DCH 0/0 as it is done already in the original implementation.
• Function is similar if the congestion occurs in the soft handover branch addition over the Iur.
• DPCCH overhead included in load factor estimation has too conservative value based on initial UL SIR target. This modification multiplies the initial SIR target value with the activity factor of the signaling link DCH.
• Estimate the physical channel data after channel (Turbo) decoding. The physical channel data is generated by encoding the decoded data. Large gain from channel decoding
• The access classes [0,…9] which are barred are actually rotated by specified intervals.
• If during first time interval, the access classes [1,2,3] were barred, in the next time interval [4,5,6] would be barred covering access classes 0,…,9, i.e. rotation by mod 10. Rotation time needs to be long enough.
• High interference cases can be solved by using suitable timer and other parameters during mass events. Some of those parameters are not good for the non-congested cells. Therefore, the parameters should be automatically tuned according to the instantaneous load.
• Channel Quality Information (CQI) frequency is 4 ms currently
• CQI frequency could be lowered during high uplink load to minimize the interference in the same way as DPCCH offset values are optimized
• Current CQI interference contribution with 4 ms period = 0.41 x DPCCH. If we would lower CQI frequency to 10 ms or 20 ms, the interference would reduce to 0.08..0.16 x DPCCH.
• The total uplink interference from HSDPA users without any uplink activity would be reduced be 1-(1+0.08)/(1+0.41) = 23%
• HS-RACH allows carrying medium size data packets without allocation of dedicated resources
kB per DCH or HS-DSCH Allocation315
199
160180200220240260280300320
• The avarage data volume per allocation is typically 10-60 kB for the smartphones. The median value is even smaller: 60% of allocations are below 1 kB ⇒ largepart of smartphone traffic could becarried by HS-RACH
• Immediate stop of controlchannel transmission compared to DCH with >1 second timer
Summary
• 3G networks have turned to be uplink limited due to interference limited nature of CDMA uplink. The main problems come from the control channel and signalling overhead which is driven by increased smartphone traffic and HSUPA high data rates
• NSN has introduced a large number of features in RU20 and RU30 to improve the uplink performance. The features have already shown to be highly useful in the practical networks.