Independent Study Presentation
Positioning Techniques in 3G
Networks
Pushpika Wijesinghe
Supervisor:
Prof (Mrs.) Dileeka Dias
Outline
• 3G mobile Networks
– 3G Standards
– Basic Network Architecture
• Positioning Parameters in 3G networks
• Positioning Techniques in 3G networks
3G Mobile Networks
• Intended to provide Global Mobility
Source: http:// www.ccpu.com
3G standards
IMT-2000
Paired spectrum
Unpaired spectrum
WCDMA
(UTRA
FDD)
TD-CDMA
(UTRA
TDD)
3GPP
UMTS
Cdma2000
(multicarrier)
3GPP2
UWC 136
(Singlecarrier)
DECT
(Frequen
cy Time)
UWCC
ETSI
DECT
Basic Network Architecture
Source: http:// www.ccpu.com
Core Network ..
Core
Network
PS Domain
SGSN
To Access
Network
AuC
MSC
GGSN
HLR
To Packet
Network
EIR
GMSC
CS Domain
To PSTN
Network
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
UE
• Can 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
receiver
• RSSI describes the downlink interference
level at the UE side
• Measurable by the UE
• Can be measured in active mode only
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
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
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
Positioning Techniques
Positioning Techniques
Positioning Techniques
Cell ID Based Methods
OTDOA with Enhancements
Database Correlation Method
Pilot Correlation Method
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
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)
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)
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)
F ( x) 
N

i 1
 1 
f i ( x)  P  

g
(
x
)
i 1 
i

N
1
2
g i ( x)   f i ( x)
f i ( x)  d i 
( xi  x)2  ( yi  y) 2  0
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
xk 1  xk   x F ( xk )
- Continue until the following condition is fulfilled, for a
defined threshold
 x F ( xk )  t
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
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 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:
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
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)
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
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
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
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
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
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
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
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
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”
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
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
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.
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
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 SLMS
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
Pilot Correlation Method
• Some results obtained in real network conditions in an
urban UMTS network in Finland….
Test Route
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
Other Positioning Techniques
• Positioning Element OTDOA method
• Angle of Arrival Method
• Uplink Time Difference of Arrival Method
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
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.
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/R100-1186.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 Lempiäinen, “Novel mobile-based location
techniques for UMTS”, Institute of Communications Engineering,
Tampere University of Technology, Tampere, Finland.
Questions?
Thank You