1. Independent Study Presentation
Positioning Techniques in 3G
Networks
Pushpika Wijesinghe
Supervisor:
Prof (Mrs.) Dileeka Dias

2. Outline
• 3G mobile Networks
– 3G Standards
– Basic Network Architecture
• Positioning Parameters in 3G networks
• Positioning Techniques in 3G networks

3. 3G Mobile Networks
• Intended to provide Global Mobility
Source: http:// www.ccpu.com

4. 3G standards
Paired spectrum
IMT-2000
Unpaired 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. Basic Network Architecture
Source: http:// www.ccpu.com

6. Core Network ..
Core
Network
P Domain
S
SGSN GGSN To Packet
Network
To Access
Network AuC HR
L EIR
MSC
GMSC To PSTN
Network
CS Domain

7. Positioning Parameters

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. 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. 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. 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. 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. Positioning Techniques

14. Positioning Techniques
Positioning Techniques
Cell ID Based Methods
OTDOA with Enhancements
Database Correlation Method
Pilot Correlation Method

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. 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. 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. 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. 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. 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. 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. OTDOA method with Enhancements
Standard 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
• MS's position is
determined by the
intersection of hyperbolas for
at least three pairs of Node
Bs
Source:
[3] 3GPP TS 25.215:

23. Standard OTDOA method
Features
• 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 MS
Drawbacks
• Hearability Problem  Serving NodeB drowns the signals
from distant NodeBs
Solution
• Get the assistance of secondary services
 OTDOA method with Enhancements

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

26. OTDOA method with Enhancements
Time 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. 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. OTDOA method with Enhancements
Use 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. 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. 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. Use of Cumulative Virtual blanking (CVB)
Some preliminary results obtained through trials in
several 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. 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. 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
points
Source: [8]. “Database correlation method for UMTS location”

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. 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 m
OTDOA 97 m 620 m

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. Pilot Correlation Method
Database 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. Pilot Correlation Method
Location 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. Pilot Correlation Method
Advantages
• 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. 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. Other Positioning Techniques
• Positioning Element OTDOA method
• Angle of Arrival Method
• Uplink Time Difference of Arrival Method

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. 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. 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. 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. Questions?

47. Thank You