HSPA+ Throughput Improvement Solution and Implementation

Loredana Burgard

HSPA+ Throughput Improvement Solution and Implementation

Loredana Burgard

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Abstract：This article presents a solution to improve HSPA+ throughput which is consisted of RTWP optimization, Radio Resource Allocation and Adoption of New Features. Compared with the historical optimization practice, the solution herein outruns the improvement by more than 10 times for UL throughput and doubles the DL throughput at the same time. The solution in this article already applied in the other project and it is worthy of transplanting into more mobile networks for similar optimization purpose.

HSPA+ Throughput Improvement Solution and Implementation Abstract：This article presents a solution to improve HSPA+ throughput which is consisted of RTWP optimization, Radio Resource Allocation and Adoption of New Features. Compared with the historical optimization practice, the solution herein outruns the improvement by more than 10 times for UL throughput and doubles the DL throughput at the same time. The solution in this article already applied in the other project and it is worthy of transplanting into more mobile networks for similar optimization purpose. Keywords：HSPA+, Throughput Improvement, RTWP, Radio Resource Allocation 1. Preface HSPA+ supports UL 5.76Mbps/ DL 21Mbps and above throughput theoretically which is rather high for the actual application requirement currently. But the throughput in field test in many countries is far below the theoretical peak throughput, esp. for HSUPA. For instance, UL HSPA+ throughput remains at 70kbps or so in I country, similar as the performance in TD network in China Mobile. In the past there’re few optimization cases in this field in our company. One case in country M achieved 15% improvement for UL throughput to reach about 100kbps or so. In summary, HSPA+ throughput field test result is only close to 1% of the theoretical peak throughput. It makes the operator undervalue the investment for HSPA+; and the end user expect to enjoy better perception for HSPA+ service. The author combines many technical methods to improve the UL throughput by 2 times to even more than 10 times, and doubles the DL throughput during optimization solution bidding for a large scale network. Finally we get the PO and implement the solution in whole network. The solution also transplanted into the other network in country P. I am honored to share my ideas herein first and expect everyone share better ideas to all. 2. Ideas of HSPA+ Throughput Improvement The solution is consisted of three parts: RTWP Optimization Radio Resource Allocation Adoption of New Features RTWP is consisted of UL payload, UL Signal and various of UL interference. In UMTS, RTWP is tightly impacted the network KPI and UL/DL throughput: the lower RTWP, the lower interference to network, and accordingly the higher throughput. After reduces the RTWP, it provides the space to relieve the negative impact upon KPI accompanied by the throughput. For the operator, the higher UL Payload, the more income for them in most of the cases; and it’s hard to eliminate various of interference esp. for a large network. So it seems only one relatively simple way to decrease the RTWP through decreasing the UL signal traffic. We integrate some methods with this idea based on the practice in other UMTS networks. Radio Resource Allocation is to optimize the associated threshold and priority of radio resource allocation between HSPA+ and other services to enable HSPA+ subscriber utilize more radio resource and own high priority than R99 PS under the prerequisite that the user of other service perception maintains including KPIs. Considered HSPA+ is of higher efficiency to consume the radio resource than that of R99 PS, it is therefore reasonable and profitable. Some new features have positive gains for both UL and DL throughput theoretically. Considered the request of presales team to package the solution to make it complex and valuable, we introduce some new features into the solution: TTI Switch on BE Service Based on Coverage License Adaptive Configuration of Traffic Channel Power Offset for HSUPA CQI Adjustment Based on Dynamic BLER Target CE Overbooking HSDPA Scheduling Based on UE Location HSDPA Scheduling Based on UE Location During field test, after activates the new features above, UL throughput slightly degrades, but UL throughput is more stable than ever before; and DL throughput improves. Two new features are available starting from RAN 14. Considers the network will upgrade to RAN14 in the near future, we integrate them into the solution: 3．Implementation of HSPA+ Throughput Improvement 3．1 Solution Details[1],[2] RTWP Optimization[1],[5] RTWP Optimization herein is to modify CQIFbCk, CQIFbCkforSHO, CONSTANTVALUE,PREAMBLERETRANSMAX and POWERRAMPSTEP to decrease the UL signal traffic but not produce negative impact upon network performance. These methods are verified in other two large scale network in the past with positive results, esp. for the cells in hot spot: MOD UCELLHSDPCCH: CELLID=xxx,CQIFbCk=D8,CQIFbCkforSHO=D8; MOD UPRACHUUPARAS: CELLID=xxx, PHYCHID=4,CONSTANTVALUE=-30,PREAMBLERETRANSMAX=30, POWERRAMPSTEP=1; Several reserved parameters below are profitable to maintain the KPI[5] hence we integrate them into the solution as well: SET UCORRMALGOSWITCH:ReservedSwitch0=RESERVED_SWITCH_0_BIT3-1; SET UCORRMALGOSWITCH:ReservedSwitch0=RESERVED_SWITCH_0_BIT23-1; SET URRCTRLSWITCH: RsvdPara1=RsvdBit1_BIT25-0; SET UCORRMALGOSWITCH: PcSwitch=PC_HSUPA_DATA_CH_PO_ADAPTIVE_ADJ_SWITCH-1; Radio Resource Allocation[1],[3],[4] Radio Resource Allocation is dedicated to change the thresholds associated with resource allocation to enable HSPA+ subscriber utilize more radio resource when in use; and use the resource with a higher priority than that of the R99 PS user. Considered HSPA+ is of higher efficiency to consume the radio resource than that of R99 PS, it is reasonable and profitable to bear the data payload with HSPA+, instead of R99. After HSPA+ subscriber completes the transmission, the resource is free for use by other services. So the negative impact is acceptable in general which is supported by the stable evolution of RNC level KPI. Associated settings are listed below: SET FRCCHLTYPEPARA: SrbChlType=HSUPA, SrbChlTypeRrcEffectFlag=FALSE; ADD USPG:SPGID=2, PRIORITYSERVICEFORR99RT=1, PRIORITYSERVICEFORR99NRT=2, PRIORITYSERVICEFOREXTRAB=1, PRIORITYSERVICEFORHSDPA=1, PRIORITYSERVICEFORHSUPA=1; MOD UCELLSETUP:CELLID=xx, SPGID=2; SET UEDCHRATEADJUSTSET:EDCHRATEADJUSTSET= RATE_8KBPS-0&RATE_16KBPS-0&RATE_32KBPS-0&RATE_64KBPS-1&RATE_128KBPS-0&RATE_144KBPS-0&RATE_256KBPS-0&RATE_384KBPS-1&RATE_608KBPS-1&RATE_1280KBPS-1&RATE_2048KBPS-1&RATE_2720KBPS-0&RATE_5440KBPS-1&RATE_11480KBPS-0; ADD UCELLALGOSWITCH: CellId=xxx, NBMLdcAlgoSwitch=UL_UU_LDR-1; MOD UCELLLDM: CellId=xxx, UlLdrTrigThd=50, UlLdrRelThd=45; MOD UCELLLDR: CellId=xxx, UlLdrFirstAction=BERateRed; MOD UCELLCAC: CELLID=xxxx, ULCELLTOTALTHD=83; DEA UCELLHSUPA: CELLID=xxx; MOD UCELLHSUPA:CELLID=xxx, EAGCHCODENUM=2, ERGCHEHICHCODENUM=2, MAXTARGETULLOADFACTOR=85; ACT UCELLHSUPA: CELLID=xxx; When transplanting the solution, we can retune the above settings to adapt the requirement and condition of each network, and not force to strictly follow the settings listed above. All associated parameters are summarized below： Description Parameters Basic Requirement for HS SrbChlTy`pe SrbChlTypeRrcEffectFlag Radio resource allocation PRIORITYSERVICEFORR99NRT PRIORITYSERVICEFORR99RT PRIORITYSERVICEFORHSDPA PRIORITYSERVICEFORHSUPA Decrease RTWP EDCHRATEADJUSTSET CQIFbCk CQIFbCkforSHO CONSTANTVALUE PREAMBLERETRANSMAX Traffic Balance NBMLdcAlgoSwitch UlLdrTrigThd UlLdrRelThd UlLdrFirstAction Assign more resource for HS Service to improve HS throughput ULCELLTOTALTHD EAGCHCODENUM ERGCHEHICHCODENUM MAXTARGETULLOADFACTOR DraSwitch Maintain KPI RetryCapability ReservedSwitch0:RESERVED_SWITCH_0_BIT5 ReservedSwitch0:RESERVED_SWITCH_0_BIT7 ReservedSwitch0:RESERVED_SWITCH_0_BIT3 ReservedSwitch0:RESERVED_SWITCH_0_BIT23 RsvdPara1 PcSwitch Adoption of New Features[1],[2],[3] E2D is applied in the current network and produces slightly negative impact to throughput. After activates TTI Switch for BE Services Based on Coverage License, we can deactivate E2D solution because the two solutions cannot co-exist in an RNC and the gains of E2D can be achieved by the previous feature: SET UFRC: RetryCapability=TTI_2MS-0; SET UCORRMALGOSWITCH: ReservedSwitch0=RESERVED_SWITCH_0_BIT5-0; SET UCORRMALGOSWITCH: ReservedSwitch0=RESERVED_SWITCH_0_BIT7-0; The detailed configuration of these features are documented in [3] SingleRAN Features Activation Guideline (V900R013C00_09)(PDF)-EN, [4] SingleRAN Configuration Guideline(V900R013C00_04)(PDF)-EN。 3．2 Impact upon Network During implementation of the solution, KPI doesn’t degrade that is worried by team previously because usually throughput increment will produce negative impacts to KPI. It shows the adoption of RTWP and other KPI optimization methods is profitable in the solution. CS Call Drop Rate evolution can partially explain it that is given below: Unfortunately some cells emerges high UL power congestion appears in hot spot. After compares the parameter settings, an RNC-level parameter differs from the settings of normal functioned RNC: BEHSUPA2MSTTIRATETHS. After unified it (SET UFRC: BEHSUPA2MSTTIRATETHS=D1280；), UL power congestion recovers to normal case. As for the slight UL power congestion, CE congestion and Code congestion in few cells in hot spot, we can take it for granted considers the HSPA+ throughput improves tremendously. Some other actions can be applied to relieve the congestion issue such as adding a new micro site, decreasing the power of PCPICH, CE expansion, etc.

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