Positioning techniques in 3 g networks (1)


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Positioning techniques in 3 g networks (1)

  1. 1. Independent Study PresentationPositioning Techniques in 3G Networks Pushpika Wijesinghe Supervisor: Prof (Mrs.) Dileeka Dias
  2. 2. Outline• 3G mobile Networks – 3G Standards – Basic Network Architecture• Positioning Parameters in 3G networks• Positioning Techniques in 3G networks
  3. 3. 3G Mobile Networks• Intended to provide Global Mobility Source: http:// www.ccpu.com
  4. 4. 3G standardsPaired spectrum IMT-2000Unpaired spectrum WCDMA TD-CDMA Cdma2000 UWC 136 DECT (UTRA (UTRA (multi- (Single- (Frequen FDD) TDD) carrier) carrier) cy Time) E SI T 3GPP 3GP 2 P UWCC DECT UM S T
  5. 5. Basic Network Architecture Source: http:// www.ccpu.com
  6. 6. Core Network .. Core Network P Domain S SGSN GGSN To Packet NetworkTo AccessNetwork AuC HR L EIR MSC GMSC To PSTN Network CS Domain
  7. 7. Positioning Parameters
  8. 8. Received Signal Code Power (RSCP)• Received power on one code measured on the Common Pilot Channel (CPICH)• A downlink measurement, carried out by the UE• Can be obtained in idle mode and active mode
  9. 9. Received Signal Strength (RSS)• The received wide band power, including thermal noise and noise generated in the receiver• RSSI describes the downlink interference level at the UE side• Measurable by the UE• Can be measured in active mode only
  10. 10. SFN-SFN observed time difference• Time Difference of System Frame Numbers (SFN) between Two cells TCPICHRxj – TCPICHRxi TCPICHRxj - Time when the UE receives one Primary CPICH slot from cell j TCPICHRxi - 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
  11. 11. 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 UE TRX - 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 NodeB• Measured in active mode only
  12. 12. Angle of Arrival (AoA)• Arrival angle of the signals from the mobile station at several NodeBs• Special antenna arrays should be equipped at the NodeBs NodeB with directional antenna
  13. 13. Positioning Techniques
  14. 14. Positioning TechniquesPositioning Techniques Cell ID Based Methods OTDOA with Enhancements Database Correlation Method Pilot Correlation Method
  15. 15. Cell ID Based Method• Simplest method• MS position is estimated with the knowledge of serving NodeB• Position can be indicated as: • Cell Identity of the serving cell • Service Area Identity • Location co-ordinates the serving cell• Accuracy of the estimation depends on the coverage area of the cells
  16. 16. Enhancements to Cell ID• Wide range of enhancements for the Cell ID based method – Cell ID + RTT (Round Trip Time) – Cell ID + Reference Signal Power Budget – Cell ID + RSCP (Received Signal Code Power)
  17. 17. Cell ID + RTT (Round Trip Time)• Identical to Cell ID+TA (Timing Advance) method in GSM• Accuracy of RTT measurements in UMTS is significantly higher (36m)• RTT is used to calculate the distance from the NodeB to MS using propagation models• Performance can be enhanced by incorporating the RTT measurements from all Node Bs in the Active Set• Accurate RTT measurements through Forced Hand Over (FHO)
  18. 18. 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) −1 N  1  N F ( x ) = ∑f i ( x ) − P ∑ 2   i=1 i=  1 gi ( x)  g i ( x) = − f i ( x) f i ( x ) = d i − ( xi − x ) 2 +( yi − y ) 2 ≥ 0 x = co lumn matrix co nsisting the co o rdinate s o f the M (x, y). S P = APo sitive Scalar
  19. 19. Cell ID + RTT (Round Trip Time)Location Estimation: - Location estimation is done according to the following recursion xk +1 = xk − µ∇ x F ( xk ) - Continue until the following condition is fulfilled, for a defined threshold ∇ x F ( xk ) ≤ t
  20. 20. Cell ID + RTT (Round Trip Time)• Some simulation results for urban & suburban areas (by Jakub Borkowski & Jukka Lempiainen) Topology Urban Suburban 67% 95% 67% 95% 6-sector / 650 75 m 200 m 50 m 150 m 6-sector / 330 60 m 220 m 55m 170 m
  21. 21. 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
  22. 22. OTDOA method with EnhancementsStandard OTDOA Method• Relative timing offset of the CPICH associated with different Node Bs are used• Each OTDOA measurement describes a line of constant difference (a hyperbola) along which the MS may be located• MSs position isdetermined by theintersection of hyperbolas forat least three pairs of NodeBs Source: [3] 3GPP TS 25.215:
  23. 23. Standard OTDOA methodFeatures• The accuracy depends on the precision of the timing measurements• Timing synchronizations of different NodeBs is essential• Best results are when the Node Bs equally around the MSDrawbacks• Hearability Problem  Serving NodeB drowns the signals from distant NodeBsSolution• Get the assistance of secondary services  OTDOA method with Enhancements
  24. 24. OTDOA method with EnhancementsUse of Idle Periods in Down Link (IPDL) • In UMTS NodeB transmissions are synchronously ceased for a short period of time - Idle Period • Terminal can measure neighbor NodeBs during Idle Periods • Maximizes the hearability of distant pilots • Two techniques – Standard IPDL – Time Aligned IPDL (TA-IPDL)
  25. 25. 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
  26. 26. 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
  27. 27. Time Aligned IPDL (TA-IPDL) Method - Simulation Results (TSG-RAN Working Group 1) Area 67 % error 90 % rms error Rural 8m 6m Sub urban 6m 5m Urban-B 44 m 39 m Urban -A 95 m 83 m Bad Urban 218 m 193 m
  28. 28. OTDOA method with EnhancementsUse of Cumulative Virtual blanking (CVB)• Uses virtual blanking of the Node B downlink signals in the software domain based on the principles of interference cancellation• Significantly enhances hearability than in IPDL, using signal processing techniques Source: [12] http://www.3gpp.org/ftp/tsg_ran/TSG_RAN/RP-020372.pdf
  29. 29. Use of Cumulative Virtual blanking (CVB)• Downlink signal are measured simultaneously at the handset and at Node Bs • Handset – Received signal snapshots • NodeB - Time co-incident snapshots of the transmitted signals• Measurements are transferred to the location server• Location server extracts the OTD of weaker NodeBs’ signals by attenuating the interfering signals one by one• Multiple Node B signals are blanked allowing weaker ones to be measured• Positioning is done using standard OTDOA algorithm
  30. 30. Use of Cumulative Virtual blanking (CVB)Features • No impact on downlink capacity • Median number of hearable Node Bs for CVB is roughly double that for IPDL • Much more robust in the presence of multipath • Operational complexity is reduced compared with IPDL
  31. 31. Use of Cumulative Virtual blanking (CVB)Some preliminary results obtained through trials inseveral sites of a UMTS network (TSG-RAN Group) Site Time Error 1 16:26 22.8 m 2 16:43 27.6 m 3 17:11 16.9 m 4 17:13 5.7 m 5 17:16 26.2 m
  32. 32. Database Correlation Method (DCM)• Based on a pre-measured database of location dependent variable• DCM 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 ID – Power delay profile from that Node
  33. 33. Database Correlation Method (DCM) • In location estimation PDP from the serving NodeB is correlated with the PDPs stored in the database • The 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”
  34. 34. Database Correlation Method (DCM)• Advantages – Avoids problems related to Multipath Propagation• Drawbacks – Delay 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
  35. 35. Database Correlation Method (DCM)• Some simulation results in urban UMTS network in comparison with OTDOA method -(by Suvi Ahonen & Heikiki Laitinen) 67 % 95% DCM 25 m 140 mOTDOA 97 m 620 m
  36. 36. Pilot Correlation Method• Based on a database with pre-measured samples of Received Signal Code Power (RSCP) Measurements of visible Pilots• Database Preparation – Area is divided into small regions (positioning regions) – Size of the region depends on the desired accuracy – For each positioning region, the most probable Common Pilot Channels’ RSCP measurements are stored.
  37. 37. Pilot Correlation MethodDatabase Preparation• An entry of the database contains: – The positioning region – Visible Common Pilot Channels – RSCP of each pilot• Can be created automatically from log files of the measurement tool
  38. 38. Pilot Correlation MethodLocation Estimation• Measured RSCP of visible pilots are compared with all samples stored in the database• Least Square Method is applied for comparison S LMS = ∑ ( Si − mi ) 2 = ∑ ∆ i i∈ N i∈ N Si – Value of the ith field of the stored sample mi – Value of the ith field of the measurement N - Number of fields in the vector• Estimated location  coordinates of the middle point of the position region having smallest S LMS
  39. 39. Pilot Correlation MethodAdvantages• An entirely network-based approach and doesn’t require any hardware or software modifications in the MS• Deployment costs are minimized by the use of standardized measurements and procedures• Since the database can be created automatically using the log files of the measurement tool, no additional effort is needed in database formation
  40. 40. Pilot Correlation Method• Some results obtained in real network conditions in an urban UMTS network in Finland…. T Route est 67 % 95 % Route -1 70 m 130 m Route -2 90 m 195 m Route -3 90 m 180 m - By Jakub Borkowski & Jukka Lempiainen
  41. 41. Other Positioning Techniques• Positioning Element OTDOA method• Angle of Arrival Method• Uplink Time Difference of Arrival Method
  42. 42. Summary• 3G Mobile Networks• Positioning Parameters in 3G Networks• Positioning Techniques – Enhancements to Cell ID based methods – Time based methods • OTDOA methods and enhancements – Database Correlation method – Pilot Correlation method
  43. 43. 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 Lempi¨ainen, “Practical Network-Based Techniques for Mobile Positioning in UMTS”, Institute of Communications Engineering, Tampere University of Technology, Finland.
  44. 44. References[7] J. Borkowski, J. Niemel¨a, and J. Lempi¨ainen, “Performance of Cell ID+RTT hybrid positioning method for UMTS radio networks,” in Proceedings of the 5th European Wireless Conference, pp. 487–492, 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. 2696–2700, Jeju, South Korea, April 2003.[9] J. Borkowski and J. Lempi¨ainen, “Pilot correlation method for urban UMTS networks,” in Proceedings of the 11th European Wireless Conference, vol. 2, pp. 465–469, 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/R1-00-11 .
  45. 45. 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 Lempiäinen, “Novel mobile-based location techniques for UMTS”, Institute of Communications Engineering, Tampere University of Technology, Tampere, Finland.
  46. 46. Questions?
  47. 47. Thank You