Positioning Techniques in 3G NetworksPushpika WijesingheIndependent Study PresentationSupervisor:Prof (Mrs.) Dileeka Dias

Outline3G mobile Networks3G StandardsBasic Network ArchitecturePositioning Parameters in 3G networksPositioning Techniques in 3G networks

3G Mobile NetworksIntended to provide Global MobilitySource: http:// www.ccpu.com

3G standards

Basic Network ArchitectureSource: http:// www.ccpu.com

Core Network ..To Access NetworkCore NetworkTo PSTN NetworkTo Packet NetworkSGSNGGSNMSCGMSCEIRPS DomainCS Domain

Positioning Parameters

Received Signal Code Power (RSCP)Received power on one code measured on the Common Pilot Channel (CPICH)A downlink measurement, carried out by the UECan be obtained in idle mode and active mode

Received Signal Strength (RSS)The received wide band power, including thermal noise and noise generated in the receiverRSSI describes the downlink interference level at the UE side Measurable by the UECan be measured in active mode only

SFN-SFN observed time differenceTime Difference of System Frame Numbers (SFN) between Two cellsTCPICHRxj TCPICHRxi

TCPICHRxj - Time when the UE receives one Primary CPICH slot from cell jTCPICHRxi - Time when the UE receives the Primary CPICH slot from cell i that is closest in time to TCPICHRxj

Measured in idle mode or active mode by the UE

Round Trip Time (RTT)Corresponds to the Timing Advance Parameter in GSM RTT = TRX TTX

TTX - Time of transmission of the beginning of a downlink DPCH frame to a UETRX - Time of reception of the beginning (the first detected path, in time) of the corresponding uplink DPCCH frame from the UE

Measurements are possible on Downlink DPCH transmitted from NodeB and Uplink DPDCH received in the same NodeBMeasured in active mode only

Angle of Arrival (AoA)Arrival angle of the signals from the mobile station at several NodeBsSpecial antenna arrays should be equipped at the NodeBs

Positioning Techniques

Positioning Techniques

Cell ID Based MethodSimplest methodMS position is estimated with the knowledge of serving NodeB Position can be indicated as:Cell Identity of the serving cellService Area Identity Location co-ordinates the serving cellAccuracy of the estimation depends on the coverage area of the cells

Enhancements to Cell IDWide range of enhancements for the Cell ID based methodCell ID + RTT (Round Trip Time)Cell ID + Reference Signal Power BudgetCell ID + RSCP (Received Signal Code Power)

Identical to Cell ID+TA (Timing Advance) method in GSMAccuracy of RTT measurements in UMTS is significantly higher (36m)RTT is used to calculate the distance from the NodeB to MS using propagation modelsPerformance can be enhanced by incorporating the RTT measurements from all Node Bs in the Active SetAccurate RTT measurements through Forced Hand Over (FHO)Cell ID + RTT (Round Trip Time)

Cell ID + RTT (Round Trip Time)Location Estimation:Constrained least-square (LS) optimization for estimating the position (by Jakub Borkowski & Jukka Lempiainen)Assume an initial position (Geographical mean of hearable NodeBs)Minimize the function F(x)

x = column matrix consisting the coordinates of the MS (x,y).P = A Positive Scalar

Cell ID + RTT (Round Trip Time)Location Estimation:- Location estimation is done according to the following recursion

- Continue until the following condition is fulfilled, for a defined threshold

Cell ID + RTT (Round Trip Time)Some simulation results for urban & suburban areas (by Jakub Borkowski & Jukka Lempiainen)

TopologyUrbanSuburban67%95%67%95%6-sector / 65075 m200 m50 m150 m6-sector / 33060 m220 m55m170 m

Cell ID + Reference Signal Power Budget (RSPB)Coverage area of a cell can be determined by using RSPB RSPB gives information about- Node B transmitted power- Isotropic path loss- Coverage threshold at coverage area border for a given location probability- Cell radius for indoor and outdoor coverage SRNC may compare the received power levels with the power budget to accurately position the UE

OTDOA method with EnhancementsRelative timing offset of the CPICH associated with different Node Bs are usedEach OTDOA measurement describes a line of constant difference (a hyperbola) along which the MS may be located MS's position is determined by the intersection of hyperbolas for at least three pairs of Node Bs Standard OTDOA Method Source: [3] 3GPP TS 25.215:

Standard OTDOA methodFeaturesThe accuracy depends on the precision of the timing measurements Timing synchronizations of different NodeBs is essentialBest results are when the Node Bs equally around the MSDrawbacksHearability Problem Serving NodeB drowns the signals from distant NodeBsSolutionGet the assistance of secondary services OTDOA method with Enhancements

OTDOA method with EnhancementsIn UMTS NodeB transmissions are synchronously ceased for a short period of time - Idle PeriodTerminal can measure neighbor NodeBs during Idle PeriodsMaximizes the hearability of distant pilots Two techniquesStandard IPDLTime Aligned IPDL (TA-IPDL)Use of Idle Periods in Down Link (IPDL)

OTDOA method with EnhancementsUse of Idle Periods in Down Link (IPDL)Standard IPDL- Pseudo random idle slotsTime Aligned IPDL (TA_IPDL)- Time Aligned Idle Slots Source: [10] 3GPP TSG-RAN WG1 doc

OTDOA method with EnhancementsTime Aligned IPDL (TA-IPDL) Method During the common idle period each node B transmits a signal ONLY useful for location estimation, randomly, pseudo-randomly or periodically OTDOA of these common pilots is measured in the MS for different Node Bs Positioning is done as in the standard OTDOA algorithm Drawbacks added complexity to the network operation reduced communication efficiency

Time Aligned IPDL (TA-IPDL) Method- Simulation Results (TSG-RAN Working Group 1)

Area67 % error 90 % rms error Rural8 m 6 mSub urban6 m5 mUrban-B44 m39 mUrban -A95 m83 mBad Urban218 m193 m

OTDOA method with EnhancementsUses virtual blanking of the Node B downlink signals in the software domain based on the principles of interference cancellationSignificantly enhances hearability than in IPDL, using signal processing techniques

Use of Cumulative Virtual blanking (CVB) Source: [12] http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/RP-020372.pdf

Use of Cumulative Virtual blanking (CVB)Downlink signal are measured simultaneously at the handset and at Node Bs Handset Received signal snapshotsNodeB - Time co-incident snapshots of the transmitted signalsMeasurements are transferred to the location serverLocation server extracts the OTD of weaker NodeBs signals by attenuating the interfering signals one by oneMultiple Node B signals are blanked allowing weaker ones to be measuredPositioning is done using standard OTDOA algorithm

Use of Cumulative Virtual blanking (CVB)No impact on downlink capacityMedian number of hearable Node Bs for CVB is roughly double that for IPDLMuch more robust in the presence of multipathOperational complexity is reduced compared with IPDLFeatures

Use of Cumulative Virtual blanking (CVB)Some preliminary results obtained through trials in several sites of a UMTS network (TSG-RAN Group)

Database Correlation Method (DCM) Based on a pre-measured database of location dependent variableDCM in UMTS utilizes Power Delay Profile (PDP) of locations (GSM used RSSI)An entry of the database consists of:location coordinates (Lat, Lon)serving Node IDPower delay profile from that Node

Database Correlation Method (DCM)In location estimation PDP from the serving NodeB is correlated with the PDPs stored in the databaseThe point with the highest correlation coefficient is chosen as the location estimate RTT measurement from same NodeB is used to limit the number of correlation pointsSource: [8]. Database correlation method for UMTS location

Database Correlation Method (DCM)AdvantagesAvoids problems related to Multipath PropagationDrawbacksDelay Profile Measurements are not standardized in 3GPP, thus requiring software changes at the MS Reporting of such measurements to the location server in the network is also not standardized Higher cost in creating database

Database Correlation Method (DCM)Some simulation results in urban UMTS network in comparison with OTDOA method -(by Suvi Ahonen & Heikiki Laitinen)

67 %95%DCM25 m140 mOTDOA97 m620 m

Pilot Correlation MethodBased on a database with pre-measured samples of Received Signal Code Power (RSCP) Measurements of visible Pilots Database PreparationArea is divided into small regions (positioning regions)Size of the region depends on the desired accuracyFor each positioning region, the most probable Common Pilot Channels RSCP measurements are stored.

Pilot Correlation MethodDatabase PreparationAn entry of the database contains:The positioning region Visible Common Pilot ChannelsRSCP of each pilotCan be created automatically from log files of the measurement tool

Pilot Correlation MethodLocation EstimationMeasured RSCP of visible pilots are compared with all samples stored in the database Least Square Method is applied for comparison

Si Value of the ith field of the stored samplemi Value of the ith field of the measurementN - Number of fields in the vectorEstimated location coordinates of the middle point of the position region having smallest SLMS

Pilot Correlation MethodAdvantagesAn entirely network-based approach and doesnt require any hardware or software modifications in the MS Deployment costs are minimized by the use of standardized measurements and proceduresSince the database can be created automatically using the log files of the measurement tool, no additional effort is needed in database formation

Pilot Correlation MethodSome results obtained in real network conditions in an urban UMTS network in Finland.- By Jakub Borkowski & Jukka Lempiainen

Test Route67 %95 %Route -170 m130 mRoute -290 m195 mRoute -390 m180 m

Other Positioning TechniquesPositioning Element OTDOA methodAngle of Arrival MethodUplink Time Difference of Arrival Method

Summary3G Mobile NetworksPositioning Parameters in 3G NetworksPositioning TechniquesEnhancements to Cell ID based methodsTime based methodsOTDOA methods and enhancementsDatabase Correlation methodPilot Correlation method

References[1] http://www.three-g.net/3g_standards.html (accessed on 15.05.2007 10.30 a.m)[2] Sumit Kasera, Nishit Narang, 3G Networks Architecture, Protocols and Procedures, Tata McGraw-Hill Professional Networking Series.[3] 3GPP TS 25.215: Universal Mobile Telecommunications System (UMTS); Physical layer; Measurements (FDD), version 7.1.0 Release 7.[4] WCDMA RNP and RNO Training material, Part I and Part II, Huawei Technologies Company limited.[5] 3GPP TS 25.305, UMTS; UE positioning in Universal Terrestrial Radio Access Network (UTRAN); Stage 2, ver. 7.1.0, Rel. 7, http://www.3gpp.org.[6] Jakub Borkowski , Jukka Lempiainen, Practical Network-Based Techniques for Mobile Positioning in UMTS, Institute of Communications Engineering, Tampere University of Technology, Finland.

References[7] J. Borkowski, J. Niemela, and J. Lempiainen, Performance of Cell ID+RTT hybrid positioning method for UMTS radio networks, in Proceedings of the 5th European Wireless Conference, pp. 487492, Barcelona, Spain, February 2004.[8] S. Ahonen and H. Laitinen, Database correlation method for UMTS location, in Proceedings of the 57th IEEE Vehicular Technology Conference, vol. 4, pp. 26962700, Jeju, South Korea, April 2003.[9] J. Borkowski and J. Lempiainen, Pilot correlation method for urban UMTS networks, in Proceedings of the 11th European Wireless Conference, vol. 2, pp. 465469, Nicosia, Cyprus, April 2005.[10] 3GPP TSG-RAN WG1 doc. No R1-99b79, Time Aligned IP-DL positioning technique, 1999, http://www.3gpp.org/ftp/ tsg ran/WG1 RL1/TSGR1 07/Docs/Pdfs/R1-99b79.pdf.[11] 3GPP TSG-RAN WG1 doc. No R1-00-1186, Initial Simulation Results of the OTDOA-PE positioning method, 2000, http://www.3gpp.org/ftp/tsg ran/WG1 RL1/TSGR1 16/Docs/ PDFs/R1-00-1186.pdf.

References[12] 3GPP TSG-RAN Meeting No. 16, TSG RP-020372, Software blanking for OTDOA positioning, June 2002, Marco Island, Florida, USA, [13] P. J. Duffett-Smith, M. D. Macnaughtan, Precise UE Positioning in UMTS Using Cumulative Virtual Blanking,, 3G Mobile Communication Technologies, May 2002, Conference Publication No.489.[14] Lames J, Caffery Jr, Gordon L.Stuber, Georgia lnstitute of Technology, Overview of Radiolocation in CDMA Cellular Systems, IEEE Communications Magazine, April 1998.[15] Jakub Borkowski, Jarno Niemelia, Jukka Lempiainen, Location Techniques for UMTS Radio Netwroks, Presentation of Reasearch Activities, Institute of Coommunications Engineering, Tampere university of Technology, Tampere, Finland.[16] Jakub Borkowski , Jukka Lempiinen, Novel mobile-based location techniques for UMTS, Institute of Communications Engineering, Tampere University of Technology, Tampere, Finland.

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