Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Final Report
Deliverable: D7.2
GNSS and UMTS Technology
Demonstrator
Name
Written
Title
Teresa Ferreira (SKY)
Signature
Date
22-06-2007
Paulo Fernandes
(SKY)
Written
Franck BENGHOUZI
(M3S)
11-06-2007
Verified
Willy VIGNAU (M3S)
11-06-2007
Verified
Jaume RIBA (UPC)
22-06-2007
Verified
Ingo WILLIMOWSKI
(IMST)
22-06-2007
Verified
Luis Nunes (SKY)
22-06-2007
Approved
Luis Nunes (SKY)
22-06-2007
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 1
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Document Change Log
Issue
Date
Description or reason for change
1.A
22-Jun-2007
First Release
Signature
Author
Teresa Ferreira
Paulo Fernandes
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 2
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Table of Contents
1
2
Introduction ............................................................................................................................................................ 9
1.1
Purpose and Scope......................................................................................................................................................... 9
1.2
Document Outline .......................................................................................................................................................... 9
Documents .......................................................................................................................................................... 10
2.1
Applicable Documents ................................................................................................................................................. 10
2.2
Reference Documents .................................................................................................................................................. 10
2.3
Abbreviations ............................................................................................................................................................... 11
3
GUTD Objectives................................................................................................................................................. 12
4
Description of the Work Performed and Results obtained .................................................................................. 13
4.1
WP 0000 – Project Management ................................................................................................................................. 13
4.2
WP 1000 – Technical and Bibliographical Review ..................................................................................................... 15
4.3
WP 2000 – Requirements Definition ............................................................................................................................ 16
4.4
WP 3000 – Detailed Design ......................................................................................................................................... 16
4.5
WP 4000 – Verification and Test Plan Definition ....................................................................................................... 17
4.6
WP 5000 – Implementation .......................................................................................................................................... 18
4.7
WP 6000 – Test Execution and Review of Design ....................................................................................................... 19
4.7.1
Test Results for the Signal Processing Implementation ....................................................................................... 19
4.7.2
Test Results for the VHDL Implementation ........................................................................................................ 20
4.7.3
Test Results for the Hybridization Algorithm Implementation ............................................................................ 21
4.8
5
WP 7000 – Technology Transfer and Dissemination .................................................................................................. 23
Overall Conclusions and Future Work................................................................................................................. 25
List of Figures
Figure 3-1: GUTD Objectives ..................................................................................................................................... 12
Figure 4-1: Development Plan .................................................................................................................................... 13
Figure 4-2: Work Breakdown Structure ...................................................................................................................... 14
Figure 4-3: State-of-the-Art Study Logic ..................................................................................................................... 15
Figure 4-4: Overall testing sequence .......................................................................................................................... 18
Figure 4-5: Doppler error [Hz] SNR = 3dB a) left: GNSS E1B, b) right: UMTS downlink ........................................... 19
Figure 4-6: Testing Results for GNSS (left), UMTS scrambling (middle), UMTS Synchronization (right) ................. 21
Figure 4-7: Absolute user position error [m]: a) left: Hybrid rural scenario, b) right: Hybrid urban scenario .............. 22
List of Tables
Table 2-1: Applicable Documents ............................................................................................................................... 10
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 3
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Table 2-2: Reference Documents............................................................................................................................... 10
Table 2-3: Abbreviations ............................................................................................................................................. 11
Table 4-1: FPGA mapping .......................................................................................................................................... 20
Table 4-2: Test Results for the Hybridization Algorithm ............................................................................................. 22
Table 4-3: Dissemination Plan .................................................................................................................................... 24
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 4
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Executive Summary
The diffusion of personal navigation is much conditioned to the capability of merging different positioning
techniques into a single device. This need is driven by the fact that, separately, the current available
technologies might fail to give a self-sufficient service in terms of accuracy, availability and integrity.
GNSS and UMTS
Satellite navigation signals, both from GPS and Galileo (hereafter, jointly referred as GNSS), guarantee
full-earth coverage and an accuracy of a few meters. But the latter only applies to outdoor users with a
clear view of the sky. In cities, the availability and accuracy of the system is greatly degraded due to poor
satellite visibility and signal attenuation from building structures, apart from other effects such as multipath.
Positioning based on a mobile radio network (at present typically GSM - in Europe -, but in a near future
UMTS) has very high levels of availability in urban environments. The received signal by the mobile
terminal is very strong (when compared to that received from GNSS satellites), can easily penetrate walls
and reach inside buildings. However the accuracy is usually very poor (constrained to some tenths of
meters). Typically, GNSS positioning provides an accuracy between 10-50 times higher than mobile phone
positioning.
Thus, it is clear that by merging both systems in an efficient way, one could take advantage from the
strengths of each individual system, overcoming their respective deficiencies.
The GUTD conducts the feasibility analysis of the hybridization between GALILEO and UMTS systems with
the goal of assessing the increase of position availability. The synergies between both systems are studied
at two critical levels: signal processing and navigation.
Signal Processing
At signal processing level, the objective for this project was to study the synergies in terms of baseband
receiver architectures. This approach is driven by the fact that both systems employ CDMA scheme and i)
use PN codes to spread the signal spectrum and ii) rely on correlation processes to track the incoming
signal and recover data. The analysis of the receiver architectures shows that both receivers implement
acquisition and tracking blocks at baseband level. For the GNSS receiver, the acquisition block performs a
single acquisition and, once the signal from a given satellite has been acquired, switches to tracking. As for
the UMTS receiver, it attempts to acquire multipath components of the signal with the purpose of
increasing the signal power. Regarding the tracking block, through the analysis of the receiver architecture
it is concluded that the low level blocks are the same in the sense that each signal is tracked by matching a
local code to the incoming signal. Then the correlation operation is performed on an Early, Prompt and
Late replicas and the results are fed to the DLL and PLL which estimate the code delay and the carrier
phase of the incoming signal respectively. This whole process is iterative allowing the receiver to track the
signal in the presence of noise (AWGN).
The acquisition and tracking blocks are implemented in a MATLAB tool which purpose it to provide
means for the integration of specific blocks of the GNSS and UMTS receiver. Indeed, this synergy is
demonstrated by using the same software components to track the signal accurately. To support the
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 5
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
baseband blocks, two signal generators are also developed in MATLAB in order to generate baseband
data that can be fed to the hybridized receiver.
In the GUTD context, the GALILEO E1B signal is considered as a good representative candidate of GNSS
signal processing analysis considering that this signal is due to to be used in mass market receivers.
Regarding UMTS, only the primary synchronization and the scrambling codes are considered. Although
both systems convey other channels in the band at hand, only the channels with the utmost importance at
baseband level are chosen to demonstrate the GUTD concept. In fact, the channels considered allow the
analysis of the acquisition and tracking blocks and it is considered that the use of more channels would
increase software complexity without bringing added value to the analysis of the critical operations within
the receiver blocks.
The results shows that the simulator is able to track the code delay and carrier phase of the signals using
different signal to noise ratios; hence proving the synergies between the GNSS and UMTS receiver
architectures.
In parallel to the implementation of the signal processing under MATLAB®, the development of the highrate signal processing functions in a hardware description language (VHDL) has been performed. In
addition to the low-rate signal processing functions commonly computed into processors (software), this
hardware implementation constitutes the core of a receiver on which the GNSS/UMTS synergy has been
applied.
VHDL implementation
This prototype was successfully tested using a VHDL test-bench with the baseband data provided by the
software signal generators. The implementation of this prototype brings an added-value to the project in
terms of proof of feasibility, since the VHDL language is a first step to the integration into a single chip,
following the SoC (System-on-Chip) philosophy. With the overall system in a single chip, the integration
into mobile devices is dramatically increased.
The strategy adopted is to use the GNSS/ UMTS synergy in order to reduce the complexity of the receiver,
to optimise components of the receiver and to verify the feasibility in the merging process of these
architectures. The VHDL coding has also been optimised to fit with real constraints (frequency, timing,
complexity), while designing a common receiver. The VHDL implementation has followed rules in order to
optimise the size of the receiver, to be compliant with synthesizer tools and then to be integrated into a
FPGA. The synthesis of the VHDL code has also been performed to determine the feasibility to implement
such receiver into a FPGA. Using a FPGA Virtex 2 XCV2-8000, it is possible to integrate 8 channels which
can be programmed either in GNSS or UMTS.
In addition, compared to a GNSS receiver, the additional logic to integrate the UMTS hardware receiver
corresponds to 20% of the receiver. So, the capability of merging different positioning techniques (UMTS &
GNSS) into a single device is real. Today, the Xilinx FPGA family has been extended to Virtex 4 and Virtex
5 families on which it is possible to integrate more channels (e.g. 16 channels are possible on a Virtex 4
LX200).
The VHDL development and results allows to conclude that a future receiver (based on FPGA or ASIC)
using both GNSS and UMTS signal processing to improve the positioning with a limited increasing of logic
is feasible.
Hybridisation of GNSS and UMTS measurement
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 6
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Finally, the GUTD analyzes the GNSS/ UMTS synergy at navigation level using a tight partial hybridization
algorithm. The tight partial approach is chosen from a trade off between performance and complexity. In
fact, the tight coupling hybridizes information from each system at measurement level, whereas the loose
coupling approach hybridizes the information at position level. The tight coupling is clearly more suitable for
the GUTD concept since it allows obtaining a position using measurements from each system even when
the measurements do not allow any of the systems to obtain individual solutions. This advantage is
fundamental to the GUTD since its objective is to increase availability.
The main idea in the proposed algorithm is generalizing the explicit closed-form estimator used in the Fang
estimator for the generic case of independent TDOA measurements. This becomes possible thanks to a
transformation of the maximum likelihood (ML) non-convex function, which allows estimating the position
as a linear combination of partial estimates. These partial estimates (to be combined later on) are obtained
by applying the original Fang’s estimator to a subset of the original TDOA measurements. The proposed
estimator has the property of being asymptotically (in the size of data window) equal to the ML estimator. It
is assumed that the variance of the measurements is known, and that these variances are inferred through
the use of models for the specification of quality factors. Finally, bi-dimensional positioning is considered
without loss of generality in order to prove the GUTD concept.
A generator of TDOAs is also developed in MATLAB so as to support the implementation of the
hybridization algorithm. The signal fades that occur during the time window in which the TDOA are
estimated, are taken into account in the hybrid generator through the variances associated to the TDOAs.
The sources of errors included in the TDOA variances are additive noise, diffuse multipath, not-perfect
Doppler estimation by the receiver, cross-correlation among codes, which occurs when the powers of the
received signals are very dissimilar (a problem known as near-far effect).
The hybridization between GNSS and UMTS at navigation level is demonstrated by running simulations on
three different scenarios: i) both GNSS and UMTS have enough TDOAs to compute position, ii) there are
more measurements from one system than the other and iii) only two TDOAs are available for each system
and, although neither system is able to provide position, the combination of their measurements allows
obtaining a navigation solution using the tight partial coupling algorithm. This approach has proven the
increase of availability of the position at the receiver by using both GNSS and UMTS systems following a
hybrid approach.
Results on synergy
As a conclusion, the GUTD concept has studied and demonstrated the synergies at signal processing and
navigation level between GNSS and UMTS hence proving the feasibility of merging these two systems in a
mass market receiver, guarantying an increase of availability of the position.
In parallel, dissemination of the GUTD and its findings has taken place by means of workshops and
presentations, as well as the development of a dedicated web site.
Future Work
As future work, the GUTD concept can evolve in different aspects, as explored in the following paragraphs,
although not being a comprehensive list of possible evolutions.
One aspect is the application of the GUTD concept to pure GNSS indoor positioning using assisted data
delivered from the UMTS data link such as satellite/ user Doppler and satellite ephemeredes. This
information can be used by the GNSS receiver to acquire satellites and obtain pseudo-range
measurements even in indoor conditions where the signal to noise ration is very low. This can be
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 7
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
performed using large integration times, and dedicated algorithms as single shot acquisition. The
improvements brought by the Assisted GNSS data can be analysed in terms of accuracy and Time To First
Fix (TTFF).
Another aspect relies in the use of UMTS positioning capabilities, i.e. availability of TDOAs in order to
increase availability in transition conditions such as shadowed to/from clear sky scenarios. This approach
has wide applications in urban environments such as tunnels and long urban canyons where transitions
between environments are very likely to occur and therefore need to be assessed extensively.
Another aspect focuses on further analysis and implementation of both Hardware and Software parts. This
analysis has to take into account trade offs between speed and power consumption but also size and
performance. The validation of such implementation (which is already done for GNSS under ORUS
environment, a tool developed by M3 SYSTEMS for modelling and simulating any signal processing chain)
could be performed under ORUS environment in order to make an easy comparison of results with/without
UMTS. Finally, the result of such hardware/software implementation is a modular tool to assess the
GNSS/UMTS future architectures and easily implement and validate any standard update or assumptions
verification.
Finally, one of the findings of the GUTD is that there is room for development of closed form algorithms for
hybridization following the tight coupling philosophy. The advantage of closed form algorithms is that they
do not have to cope with convergence challenges and therefore are potentially more robust in practical
applications. The performance of the hybridization algorithms can be further analyzed using Monte Carlo
simulations to assess robustness and performance. Furthermore, field tests campaigns could be organized
to gather real data in urban environments and further validate the hybridization algorithms.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 8
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
1
Introduction
1.1
Purpose and Scope
This document is the final report of the project named GNSS and UMTS Technology Demonstrator, GUTD.
It is elaborated in the scope of WP 7000 as described in [PMP]. The final report contains the executive
summary of the whole project and the detailed description of the project objectives, work performed, results
obtained, conclusions drawn and future work proposal.
1.2
Document Outline
The document is outlined as follows:
Chapter 1 – This chapter, an introduction to the theme and organisation of this document
Chapter 2 – Lists the reference and applicable documents
Chapter 3 – Exposes the objectives of the GUTD project
Chapter 4 – Describes the work performed in the scope of the GUTD project
Chapter 5 – Provides the conclusions and the future work
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 9
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
2
Documents
2.1
Applicable Documents
The applicable documents are listed in Table 2-1.
Reference
Document Title
Version
Classification
[TECHTDR]
GNSS and UMTS Technology Demonstrator Technical Tender,
SKY/SPC/NAV-GJU-GUTD-0001 VOL.1, 22-12-2005
1.2
Restricted
[PMP]
Project Management Plan, GUTD-INT-SKS-PL-0001
D
Public
Table 2-1: Applicable Documents
2.2
Reference Documents
The reference documents are listed in Table 2-2.
Reference
Document Title
Version
Distribution
[D1.1]
GNSS and UMTS Core Technology Summary and State-of-the-art
Synergy Techniques, GUTD-INT-SKS-TN-0003, 05-06-2006
B
Restricted
[D2.1]
GNSS, UMTS And Interface Requirements, GUTD-INT-SKS-TN-0004,
14-06-2006
A
Restricted
[D2.2]
GNSS UMTS Generator Requirements, GUTD-INT-SKS-TN-0005
A
Restricted
[D2.3]
VHDL Requirements, GUTD-INT-M3S-TN-0005
A
Restricted
[D3.1]
System, GNSS and UMTS Detailed Design, GUTD-INT-SKS-TN-0007
A
Restricted
[D3.2]
Hybridization Generator and Receiver Detailed design, GUTD-INT-SKSTN-0008
A
Restricted
[D3.3]
Hybridization Algorithms Specification, GUTD-INT-SKS-TN-0010
A
Restricted
[D3.4]
VHDL Preliminary Design GUTD-INT-M3S-TN-0011
A
Restricted
[D4.1]
Test Plan, GUTD-INT-SKS-TN-0011
A
Restricted
[D5.3]
Unit Report Testing of the Matlab Code, GUTD-INT-SKS-TN-0007
D
Restricted
[D6.1]
MATLAB Code Testing, GUTD-INT-SKY-TN-0014
A
Restricted
[D6.2]
Test Plan Results of the VHDL Implementation, GUTD-INT-M3S-D6 2
A
Restricted
[D7.1]
Dissemination And Technology Transfer Plan, GUTD-INT-SKS-PL-0013
A
Public
Table 2-2: Reference Documents
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 10
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
2.3
Abbreviations
The abbreviations used in this document are listed in Table 2-3.
Abbreviation
Description
AWGN
Additive White Gaussian Noise
BOC
Binary Offset Carrier
BPSK
Binary Phase Shift Keying
CDMA
Code Division Multiple Access
DLL
Delay Lock Loop
FFT
Fast Fourier Transform
FPGA
Field Programmable Gate Array
GNSS
Global Navigation Satellite Systems
GPS
Global Positioning System
GSM
Global System for Mobile Communications
GUTD
GNSS and UMTS Technology Demonstrator
I&D
Integrate and Dump
LOS
Line of Sight
ML
Maximum Likelihood
NLOS
Non Line of Sight
PLL
Phase Lock Loop
PN
Pseudo-Noise
SoC
System on Chip
TDOA
Time Difference of Arrival
TTFF
Time To First Fix
UMTS
Universal Mobile Telecommunications System
WP
Work Package
Table 2-3: Abbreviations
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 11
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
3
GUTD Objectives
The integration of the new navigation systems in portable personal devices as well as in vehicles is a
critical issue, since most of the GNSS applications are supposed to be in the mass market segment. Only
portable devices account for almost ¾ of the total GNSS market, and added to the car navigation segment,
this means targeting 96% of the total market size. The penetration of satellite navigation into these two
markets is very much dependent upon the ability to combine it together with other existent systems so that
the end user sees an improvement in the quality of the offered service.
The GUTD concept is a processing system which allows to study the synergies at signal processing level
and navigation level, due to the fact that these are the enabler of the combination of UMTS technology into
a mass-market receiver. The GUTD concept is depicted in Figure 3-1 below.
Simulated Code and
Doppler Values
Generation
- Simulated code phase
,
- Simulated Doppler frequency
Data, noise
Generate Data and
noise
G122
G125
GUTD Concept
Galileo E1B Baseband Signal
GNSS Signal
Generation Manager
- Simulated code phase
,
- Simulated Doppler frequency
Configuration parameters
G121
Modulated code and data,
noise, Doppler Frequency
data
Galileo E1B PRN
code for
Satellite 1
BOC modulator
Modulated
code and
data
Baseband Signal
G124
G123
NODE:
GNSS Signal
Generator
Signal Sampling
TITLE:
GNSS Signal Generation
NO.:
G12
Hybridisation
Data
Generator
GNSS Rx
VHDL
Rx
+++
...+++
Hybridisation
Receiver
UMTS Rx
UMTS Data
Generator
Typical Receiver Architecture
Fr
on
t
En
d
Signal Proc. Dem
odula
tion
Navig
Figure 3-1: GUTD Objectives
The signal processing study involves generation of GNSS and UMTS representative signals, in base band,
which are tracked for code and phase. This is the technical processing level which allows stating whether
the processing chain of a mass market receiver could process both GNSS and UMTS signals. The VHDL
implementation provides the means to prove the feasibility of such implementation in a receiver. Finally, the
hybridization of TDOA measurements from each of the systems at navigation level is assessed using a
data generator to stimulate the tight partial coupling algorithm.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 12
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
4
Description of the Work Performed and Results obtained
This section describes the work performed on each of the WP as well as the presentation of the results
obtained and the lessons learnt.
4.1
WP 0000 – Project Management
A waterfall cycle is adopted for the development of the GUTD concept, [PMP]. The development plan is
provided in Figure 4-1.
Verification and
Test Planning
WP5000
Bibliographic
Review
WP1000
Requirements
Definition
WP2000
Detailed Design
WP3000
Implementation
WP5000
Test Execution
WP6000
Figure 4-1: Development Plan
The work breakdown structure of the GUTD as discussed in [PMP] is presented in Figure 4-2.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 13
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
GUTD - GNSS and
UMTS Technology
Demonstrator
WP 0000
Project
Management
WP 1000
Technical and
Bibliographical
Review
WP 2000
Requirements
Definition
WP 3000
Detailed
Design
WP 4000
Verification
and Test Plan
Definition
WP 5000
Implementation
WP 6000
Test Execution
& Review of
Design
WP 0100
Project
Management
WI 1100
GNSS core
technology
WI 2100
GNSS, UMTS and
Interface
Requirements
WI 3100
System, GNSS and
UMTS SW Detailed
Design
WI 4100
Test Plan
WI 5100
GNSS, UMTS,
Synergy, HL and
UMTS SigGen
Implementation
WI 6100
Matlab Code
Testing
WP 0200
Quality
Management
WI 1200
UMTS core
technology
WI 2200
UMTS Signal
Generator
Requirements
WI 3200
Hybridization
Generator and
Receiver Detailed
Design
WI 4200
Test Support Tools
WI 5200
VHDL
Implementation
WI 6200
VHDL Code Testing
WI 1300
State-of-the-art of
Telecom GNSS
positioning synergy
WI 2300
VHDL
Requirements
WI 3300
Hybridization
Algorithms
Definition
WI 5300
Unit Testing
Integration and
Optimisation of the
Matlab Code
WI 3400
VHDL Preliminary
Design
WI 5400
Unit Testing
Integration and
Optimisation of the
VHDL Code
WP 7000
Technology
Transfer and
Dissemination
Figure 4-2: Work Breakdown Structure
The project management main activities, within the GUTD, includes the following:-

Monitoring of the development progress though delivery of progress reports, action items and risk
management

Coordination between partners through project meetings and milestones tracking as well as
implementation of the payment plan

Review of the technical documentation
The WBS was defined in a way that thematic subjects to be studied and worked upon provide a smooth
work flow. Also, the assignment of tasks within each work package was defined in a way that coresponsibility did not create grey areas of responsibility. A closed monitoring and discussion of these grey
areas was easily identified and discussed around the table.
The partners involved in this project have a different profile and slightly distributed technological know-how
focus. All in all, the assignment and cooperation was quite balanced, which allowed to bring into the project
the best of each partner experience and contribution.
Another positive issue to refer is the size of the Consortium, which was appropriate to the volume of work
to be performed and timescale of the project.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 14
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
4.2
WP 1000 – Technical and Bibliographical Review
The first step to the GUTD concept development is to carry out a technical and bibliographical review. This
review includes GNSS and UMTS core technology overview as well as the identification of the hybridization
algorithms state of the art. The findings are documented in [D1.1], which also contains recommendations
drawn from the bibliographical reviews.
The approach adopted is depicted in Figure 4-3.
GNSS Core Technology
GPS Signals
GNSS Signals
UMTS Core Technology
Recommendations 3GPP Standards
Recommendations
GNSS Signal
Processing
GNSS Data
Extraction
Navigation
Algorithms
Assisted
GNSS
UMTS system
architecture
UMTS Signal
Description
UMTS Based
Position
Techniques
Software
Approach
Recommendations
Hybridisation
Overview
Loose Coupling
Tight Coupling
Others
Figure 4-3: State-of-the-Art Study Logic
For each of these subjects a number of recommendations is outlined which serve as a basis for the
understanding of the GUTD concept to be proposed and hence defined at the level of system
requirements.
In general, both GNSS and UMTS signals employ the Code Division Multiplexing Scheme (CDMA) and
therefore it is expected that the receiver architectures would be similar. This signal receiver analysis covers
an overview of the signals modulation, codes constitution and the relevant features that could be
addressed at a processing level for GNSS and for UMTS.
Given that the objective of the GUTD is to study the possible synergies between GNSS and UMTS, the
recommendations point to the segmentation of this study into signal processing and hybridization.
It should be noted that the existing hybridization techniques could be applied to any system. The reason
why it is introduced in the scope of the GUTD concept is that it was noted that the UMTS was able to
provide TDOAs and thus measurements accounting for the distance from the base station to the receiver,
as does the GNSS. Furthermore, it is assumed in this approach that the UMTS receiver supports UEbased mode for positioning, i.e. the receiver has the information on the location of the base stations.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 15
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
4.3
WP 2000 – Requirements Definition
The GUTD concept defines the minimal required capabilities to be implemented such that one can
ascertain whether UMTS positioning is actually possible and that similarities with GNSS are identified and
explored. It is clear that GUTD will not implement a full GNSS or UMTS system and hence one must
propose a sensible set of supporting capabilities of the GUTD concept. The first cut into this challenge is
supported by the identification of the GNSS and UMTS positioning techniques as documented within
[D1.1]. However, the identification of the actual state-of-the-art does not lead to an explicit proposal of the
GUTD concept whereas it defines the overall picture of the involved techniques, or functions, to be
deployed in a full system. The GUTD concept is hence a judicious subset of GNSS, UMTS and
hybridisation positioning techniques, expressed as a set of requirements which are enumerated in [D2.1],
[D2.2] and [D2.3].
At baseband level, it is proposed that the signal processing simulator supports a single emitter (either
satellite or base station), single signal and signal channel approach which allows assessing the synergies
of both systems. Surely that increasing the number of emitters would not bring any other conclusion, apart
from additional computational load required to acquire and track these additional satellites. In addition,
since the GUTD focuses on mass market receivers, only the GALILEO E1B signal is considered in GNSS
whereas only the primary synchronization and scrambling codes are taken into account for UMTS.
As far as the VHDL development is concerned, only the high data rate processing functions are covered
since the low data rate processing functions are usually implemented in software in commercial receivers.
At navigation level, the hybridization between the two systems consists in computing receiver position by
using measurements received from both UMTS and GNSS systems. The tight coupling approach is
proposed, which uses the measurements provided by both systems and provides more accuracy when
compared to the loose coupling approach that merges positions of two different systems. Not only this
technique allows having position when neither GNSS nor UMTS stand alone would be able to provide it,
but also it allows taking the highest profit of the similarities between both systems.
4.4
WP 3000 – Detailed Design
The detailed design of the signal processing tool implemented in MATLAB is presented in [D3.1]. At
baseband level, GNSS and UMTS generators have the same overall processing logic. The difference is
that the UMTS (as implemented in the GUTD concept) carries two PN codes: primary synchronization code
and scrambling code whereas the generated GNSS signal only carries one PN code corresponding to a
single satellite.
The GNSS and UMTS receivers implemented in the GUTD have the same architectures as both
encompass acquisition and tracking blocks.
The acquisition block has a different implementation: while the GNSS acquisition uses FFT and Tong
detection, the UMTS uses the match filter technique. This is due to the fact that the acquisition concept is
different for both systems: for GNSS it consists in finding satellites in view whereas for UMTS, acquisition
also encompasses the multipath components and not only the LOS component, so as to increase the
signal power at the receiver.
The tracking blocks are nearly identical: a DLL and PLL are used to track the code delay and the carrier
phase respectively of the incoming signal by analyzing the early, prompt and late correlators output. Two
differences are identified. Firstly, the GNSS uses two additional correlators to implement the bump jumping
technique and hence to guarantee that it is the main peak of the BOC auto-correlation function that is being
tracked and not any of the side peaks. Secondly, the UMTS has a data rate which is higher than the
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 16
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
duration of the scrambling code and therefore a data strip step needs to be included in the baseband
processing before correlating the incoming signal with the locally generated replica.
The tight partial coupling hybridization algorithm is specified in [D3.3] and its detailed design is provided in
[D3.2]. The algorithm works by grouping the overall available TDOA measurements in subsets. Each
subset contains a pair of TDOAs. These subsets can overlap if necessary. In that case, the variance of the
TDOA used K times (in different subsets) has to be amplified (that is, the quality factor that has to be
assumed for the data fusion) just the number of times K times.
Two basic algorithms are described for the computation of the intersection between two hyperbolas. The
first one is closed-form and it is valid only for TDOA pairs of the same type (non-hybrid). The second one is
iterative and it has to be used only in the case of a hybrid pair. To avoid convergence problems, a
procedure for the initialization of the second basic algorithm has been proposed.
Once the basic algorithms have been applied to each subset, one has K partial position estimates to be
fused. Before the data fusion, some of the partial position estimates are systematically removed and not
used any more. This provides robustness to the NLOS propagation, but still preserving the capability of
computing the position estimates using more measurements than unknowns in the case that this is
possible (which provides accuracy apart form availability). The removal of a certain number of position
estimates is made on the basis of a coherence criterion applied to these position estimates as a whole, and
it is based on the concept of median filtering. The surviving partial position estimates are combined using
weighing matrices that are computed at the receiver. These matrices depend on the TDOA variances
assumed and, also, on the partial mobile position estimate.
Finally, for the models used for the determination of the TDOA variances (for the data fusion) assumed at
the receiver (quality factors) are defined, either for the case of base-stations and for the case of satellites.
The proposed models depend in a simple manner on those parameters that are more relevant, such as the
received power of the signals, the available information about the distance from the base stations and the
serving base-station, and the elevation angle (in the case of satellites).
The VHDL design is presented in [D3.4], where the UMTS proposed architecture is very similar to the
GNSS one.
The synergy with GNSS processing functions is assessed to conclude that the synchronization and the
Doppler correction modules are exactly the same.
The differences appear for the processing of the UMTS code due to the different structure of UMTS
signals. The correlation module (complex correlators and I&D) follows the same architecture as for GNSS
but is only based on 3 correlators for I and Q components (Early, Late, Prompt), those resources can thus
be shared with the GNSS processing. The I&D modules are also common to the GNSS processing ones
but they are configured to consider the different codes length (and particularly the two different codes for
UMTS signal acquisition and tracking). The local code generator is obviously completely different from the
GNSS ones. Those GNSS and UMTS code generation modules thus can not be shared to optimise the
resources.
4.5
WP 4000 – Verification and Test Plan Definition
The test plan presented in [D4.1] aims at verifying the requirements derived in WP 2000.
The principle of the GUTD verification approach is based on three steps that are processed in the first of
two phases during a simulation under MATLAB: (a) running the signal generator in order to generate the
required signal, (b) storing the baseband signal from the generator in a file, and (c) using this file by feeding
it into the signal receiver, as depicted in Figure 4-4.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 17
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
1 GNSS
set up GNSS
signal
generator
set up GNSS
signal
processor
Generate GNSS
signal
Run test
Analise and
record results
2 UMTS
set up UMTS
signal
generator
set up UMTS
signal
processor
3
Generate UMTS
signal
Analise and
record results
Hybridisation
set up Hybrid
signal
generator
set up Hybrid
signal
processor
4
Run test
Generate
Hybrid signal
Run test
Analise and
record results
VHDL
Vhdl_0110
GNSS HW
Receiver
Inputs
Vhdl_0210
UMTS HW
Receiver
Inputs
standalone
Vhdl_0120
GNSS HW
Receiver
Outputs
NCO
commands
correlators
Vhdl_0230
UMTS HW
Receiver
Outputs
VHDL Test Bench
Figure 4-4: Overall testing sequence
The overall testing approach involves the generation of signal in baseband in accordance with testing
conditions. Then, this signal is used for stimulus at the level of receiver in which the results are analysed.
Once this is performed for GNSS - as one of the configurations of the GUTD - it follows through UMTS and
Hybridisation. The second phase in MATLAB consists of the hybridization, and therefore the GUTD
software consists of two parts, one is the GUTDSignalProcessing and the other is GUTDHybrid.
Prior to the calculation step, real values need to be generated and stored in a file that contains the
baseband signal. This process is strictly sequential and therefore the stored file is left available at the end
of the simulation.
4.6
WP 5000 – Implementation
The implementation phase covers two parallel developments: VHDL and MATLAB.
The VHDL implementation follows rules in order to optimise the size of the receiver, to be compliant with
synthesizer tools and then to be integrated into a FPGA.
The MATLAB software includes the baseband and hybridization algorithms. Furthermore, the unit tests
are documented in [D5.3].
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 18
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
4.7
WP 6000 – Test Execution and Review of Design
This WP contains the results of the tests defined in [D4.1]; and hence the validation of the GUTD concept
with respect to the requirements derived in WP 2000. The test results obtained for [D4.1] are available in
[D6.1].
4.7.1 Test Results for the Signal Processing Implementation
In the previous work packages WP1000, WP2000 and WP3000 the synergies of the GNSS and UMTS
systems have been identified. The end point of the study lead to the implementation of a signal processing
MatLab® softwarem which purpose is to verify that the synergies identified at the signal processing level
are verified in a software implementation. This means that the software receiver resulting from the study
(see [D3.1]) must be able to track GNSS and UMTS signals and to recover the symbols conveyed in the
message.
GNSS and UMTS signals were generated using the implemented software with a SNR of 3dB. The signals
were then fed to the receiver that acquired and tracked them. Figure 4-5 shows the tracking results of the
signals over 1 second of simulation. Moreover, the software was able to recover 100% of the transmitted
symbols in both cases.
Figure 4-5: Doppler error [Hz] SNR = 3dB a) left: GNSS E1B, b) right: UMTS downlink
From Figure 4-5 it can be seen that the Doppler frequency estimation is stable throughout the entire
simulation in both cases. The Doppler stability illustrated denotes that the local code replicas and the
incoming signals are correctly aligned. In fact, the correct alignment, which is the goal of tracking in CDMA
systems, allowed the complete recovery of the conveyed messages. This means that the hybrid software
receiver was able to track GNSS and UMTS signals. Considering that both signals are being track and that
the receiver is able to completely recover the conveyed symbols, it can be stated that the Synergy
considerations from WP1000, WP2000 and WP3000 are met.
The synergy considerations resulting from the results obtained at the signal processing show that signal
processing do allow to use of same hardware and software modules for both systems. Otherwise, if there
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 19
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
weren’t synergies at the signal processing level there still could be hybridization at the navigational level.
However, it would be necessary for the receiver to have two separate receivers incorporated within (one for
GNSS and another for the UMTS system). In a hardware receiver point of view this would mean that the
systems would be physically separated from the reception till the measurements level. The synergy
approach proposed in the GUTD concept, shows that a considerable and important piece of equipment can
merges both systems at the signal processing level. The proposed synergy takes advantage of the fact that
both systems are CDMA systems which means that the tracking and acquisition operations are based on
the correlation operation. In fact, the receiver designed in [D3.1] proposes acquisition methods that are
both based on the same principle of correlating the local replica with the incoming signal and a tracking
method that is nearly identical for both systems. This synergy reduces significantly the hardware necessary
for a receiver with hybrid navigation capabilities and therefore significantly reduces its cost which is one of
the priorities in a mass market receiver.
4.7.2 Test Results for the VHDL Implementation
The validation of the VHDL implementation has been performed in two steps, [D6.2]: at unit and functional
levels using the signals provided by Skysoft on both UMTS and GNSS.
The synthesis of the VHDL code has also been performed to determine the feasibility to implement such
receiver into a FPGA. Using a FPGA Virtex 2 XCV2-8000, it is possible to integrate 8 channels which can
be programmed either in GNSS or UMTS.
In addition, compared to a GNSS receiver, the additional logic to integrate the UMTS hardware receiver
corresponds to 20% of the receiver. So, the capability of merging different positioning techniques (UMTS &
GNSS) into a single device is real. Today, the Xilinx FPGA family has been extended to Virtex 4 and Virtex
5 families on which it is possible to integrate more channels (e.g. 16 channels are possible on a Virtex 4
LX200) as illustrated in Table 4-1.
4 channel
GNSS/ UMTS
Receiver
FPGA Virtex 2
XCV2-8000
(available cells)
FPGA Virtex 4
LX200
(available cells)
Nb Slices
19910
46592
89068
Nb Flip Flop
17266
93184
178136
Nb block RAM
20
168
336
Nb Multi 18x18
16
168
96
-
8
16
Number of managed
GNSS/ UMTS channels
Table 4-1: FPGA mapping
The baseband signals output by the GNSS and UMTS generators have been used to validate the
implementation of the high data rate processing functions developed in VHDL.
The results are presented in Figure 4-6.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 20
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
Figure 4-6: Testing Results for GNSS (left), UMTS scrambling (middle), UMTS Synchronization
(right)
The correlators’ outputs for several delays were plotted in order to confirm the VHDL implementation. The
results show the BOC auto-correlation functions for the five correlators used (including the bump jumping
algorithm): Early, Prompt, Late and Very Early, Very Late. In addition, the correlators outputs for the UMTS
scrambling codes and the primary synchronization codes are also shown.
As a conclusion, the VHDL implementation is validated, as well as its match to the software baseband
generators.
4.7.3 Test Results for the Hybridization Algorithm Implementation
In GUTD, Hybridization - at navigational level - is implemented through the tight-partial coupling method. It
consists on hybridizing the two systems at the measurements level which is the TDOA. The purpose of this
navigation analysis is to prove feasibility of hybrid positioning and increase of availability in a GNSS/UMTS
hybrid navigation system.
In order to fulfil the purpose of this analysis the set of scenarios defined in Table 4-2 is proposed. Urban
and rural navigation situations are studied in both hybrid and GNSS only systems. The results were
obtained through 300 seconds simulations with a user moving at the constant speed of 11.1m/s.
For the urban scenario it was considered that the user would be in a dense area with 40º mask angle. In
this situation an average of 2-4 satellites are commonly visible and it was defined that only 2 would be
available to represent a tall and narrow urban canyon. Moreover, it was considered that 6 base stations
would be visible during the simulation in an urban environment.
The rural scenario is a nearly open sky situation in which it is known that the average number of visible
GNSS satellites is around 6-8 (more for the GALILEO than the GLONASS and GPS system). The density
of base stations in a rural scenario is lower than in an urban situation and in the proposed scenario it was
decided that 3 would be a good estimate of a typical situation.
The number of GNSS satellites and UMTS base stations defined in the scenarios don’t represent exact
situations but rather representative ones which allow studying typical situations for hybrid and GNSS only
receivers.
Scenario ID
Environment
Number of
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Number of
Error Standard
Page 21
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
type
available
satellites
available base
stations
Deviation [m]
(300sec
simulation)
urban
2
6
35.9
Hybrid_only
extreme urban
2
2
40-80 (10
seconds only)
Hybrid_rural
rural
6
3
4.2
GNSS_rural
rural
6
0
8.1
Hybrid_urban
Table 4-2: Test Results for the Hybridization Algorithm
From Table 4-2 and Figure 4-7 it can be stated, first of all, that hybridization at navigation level is possible.
Moreover, it can be concluded that not only is it possible but it also increases positioning availability. In
fact, when considering a very high density urban scenario, the GNSS positioning system by itself may not
able to provide a position due to high signal degradation, multipath, signal shadowing or simply by lack of
available visible satellites, whereas the Hybrid GNSS/UMTS positioning system successfully locks the
position with reasonable accuracy (see Hybrid_urban). This is a very important advantage for the hybrid
positioning system. In fact, in high density urban areas, where the GNSS system is weaker, the UMTS
system is stronger. This is due to the fact that in urban areas the density of the base stations is higher
which leads to more emitters and therefore more measurements. Also, higher density means smaller userbase station distances which in is turn means higher signal power and more accurate measurements.
Furthermore, in extreme urban conditions, scenarios like Hybrid_only may happen when only two emitters
of both systems are available. In this case neither a GNSS only nor a UMTS only receiver may calculate
the position by itself contrary to the hybrid receiver which is able to merge the measurements from both
systems and to lock an approximate position clearly increasing availability. The downside of the position
calculated in this situation is that it is obtained using only a single couple of TDOA measurements. The
reduced number of measurements drastically reduces the integrity of the obtained position lock.
Figure 4-7: Absolute user position error [m]: a) left: Hybrid rural scenario, b) right: Hybrid urban
scenario
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 22
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
In a rural scenario, the GNSS system is less degraded and obstructed. Consequently it is able to determine
the user position with good accuracy as can be seen in Table 4-2 and as it is commonly known. The
contribution of the UMTS system to the hybrid system is not as fundamental in this scenario as in the high
density urban one; nevertheless it can potentially provide better overall accuracy, as can be seen in Table
4-2. In rural environments the base station density is lower so lesser base stations are visible to the user,
yet the few that are still provide more measurements which leads to higher resistance to errors.
One important factor is that in either environment the UMTS system may always assist the GNSS system
with fundamental navigation data such as, ephemeris, identification of satellites in view, precise local
atmospheric correction, clock correction data and others which can greatly contribute to the system overall
accuracy and integrity. This particular factor was not analysed in the GUTD project since it would
potentially involve a more complex and expensive receiver which may not be adequate for the target mass
market.
To summarize, the hybridization at navigation level of the GNSS and UMTS systems is especially interest
in high density urban areas, where the GNSS system is weaker and the UMTS is stronger, by providing
increase availability. It can also potentially improve accuracy in both low and high density areas not only by
providing more measurements to the positioning algorithms but also by assisting with crucial accuracy and
integrity data.
4.8
WP 7000 – Technology Transfer and Dissemination
The technology transfer and dissemination plan is presented in [D7.1].
Activities that have been conducted include the participation in the GJU workshop which included the
distribution of leaflets and short presentations of the GUTD and the development of a web site. The web
site targets the final user, mobile communications operators, GNSS receiver equipment manufacturer,
GSM/UMTS receiver equipment manufacturer, scientific community and any cyber user. Not only does it
describe the GUTD objectives and conducted work and achievements, but it also provides information and
areas of interest of the consortium partners. The web page allows any reader to contact the GUTD
consortium through mail and provides the public deliverables of the project for download.
In addition, the time plan for the implementation of identified potential methods for dissemination is
presented in Table 4-3.
Dissemination
Method
Conference
Conference
When
Who
Specifics
Submission of Workshop
Proposal: 28 February 2007
Notification of Acceptance:
31 March 2007
Submission of the Final
Program: 15 May 2007
Summit date: 1-5 July 2007
Full papers due: March
3rd, 2007
Acceptance notice: May
All
16th IST Mobile & Wireless Communications
Summit
http://www.mobilesummit2007.org/call_for_wor
kshops
All
18th Annual IEEE International Personal,
Indoor, and Mobile Radio Communications
Symposiums
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 23
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
SKY
-
Leaflet
Industry
31st, 2007
Final manuscript due: June
16th, 2007
Construction: January 2007
Online: February 2007
Same as website
March 2007
SKY
All
Standardisation
2007
IMST
To announce to the contacted persons the
following:
- Progeny website
- GUTD website and leaflet
- any publication generated within GUTD
Consider the following manufacturers:
- Siemens AG
- Nokia
- Sony/Ericsson
- Garmin
- TomTom
- Sagem
Please vide
http://www.3gpp.org/Meetings/meetings.htm#c
alendar.
Tracking of standardization activities in
relevant bodies (e.g. ETSI, 3GPP, Car-to-Car
Communication Consortium) and feeding
results of GUTD to this bodies
Website
http://www.pimrc2007.org/
IEEE sponsored
Table 4-3: Dissemination Plan
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 24
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
5
Overall Conclusions and Future Work
From the GUTD development it is concluded that UMTS is actually an additional source for radio-location
positioning in a mass-market receiver. At signal processing level, GNSS and UMTS similarities have been
identified and it is possible, at a logical level, to share almost identical tracking processing blocks for both
systems and use the same concept to perform signal acquisition. This synergy is possible just because
both systems are CDMA systems.
Considering, by chance, that synergies would not be possible at the signal processing level, it could still be
possible to implement hybridization at the navigational level. However, it would be necessary -- for the
receiver -- to have two separate receivers incorporated within the receiver: one for GNSS and another for
the UMTS system. The synergy approach proposed for the GUTD concept -- at the acquisition and tracking
level -- bring considerable merges of the two systems. This merge allows having a single hybrid receiver
instead of two distinct receivers.
At a physical level, in VHDL, it was proved that it is possible to implement hybridised signal processing by
re-using the low level hardware tracking blocks for both systems with a limited increased logic of 20%. This
synergy significantly reduces the hardware necessary for a receiver with hybrid navigation capabilities and
therefore significantly reduces its cost which is one of the priorities in a mass market receiver.
At a navigational level, combined measurements can be used for hybrid positioning. The hybridization of
the GNSS and UMTS systems is of special interest in high density urban areas, where the GNSS system is
weaker and the UMTS is stronger, by providing increase availability comparing to the GNSS system.
Furthermore, in extreme urban conditions, it may happen that only two emitters of both systems are
available. In this case, neither a GNSS only nor a UMTS only receiver may calculate the position by itself
contrary to the hybrid receiver which is able to merge the measurements from both systems and to lock an
approximate position clearly increasing availability. It can also potentially improve accuracy in both low and
high density areas by providing more measurements to the positioning algorithms and therefore by
increasing resistance to positioning errors.
As a future work, the GUTD concept could evolve in different aspects.
The first aspect is the application of the GUTD concept to pure GNSS indoor positioning using assisted
data delivered from the UMTS data link such as satellite/ user Doppler and satellite ephemeredes. This
information can be used by the GNSS receiver to acquire satellites and obtain pseudo-range
measurements even in indoor conditions where the signal to noise ratio is very low. This can be performed
using large integration times, and dedicated algorithms as single shot acquisition. The improvements
brought by the Assisted GNSS data can be analysed in terms of accuracy and Time To First Fix (TTFF).
The second aspect relies in using the UMTS positioning capabilities, i.e. availability of TDOAs in order to
increase availability in transition conditions such as shadowed/ clear sky scenarios. This approach has
wide applications in urban environments such as tunnels and long urban canyons where transitions
between environments are very likely to occur and therefore need to be assessed extensively.
The third aspect focuses on furthering the analysis, and implementation, of both Hardware and Software
parts. This analysis has to take into account trade offs between speed and power consumption but also
size and performance. The validation of such implementation (which is already done for GNSS under
ORUS environment, a tool for modelling and simulating any signal processing chain) could be performed
under ORUS environment in order to make an easy comparison of results with/without UMTS. Finally, the
result of such hardware/software implementation would provide a modular tool to assess the GNSS/UMTS
future architectures and easily implement and validate any standard update or assumptions verification.
The last aspect is related to one of the findings of the GUTD that there is room for development of closed
form algorithms for hybridization following the tight coupling philosophy. The advantage of closed form
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 25
Final Report
Ref: GUTD-INT-SKS-PL-0015
Edition: A
Date: 13/02/2016
algorithms is that they do not have to cope with convergence problems and therefore are potentially more
robust in practical applications. The performance of the hybridization algorithms can be further analyzed
using Monte Carlo simulations to assess robustness, performance. Furthermore, field tests campaigns
could be organized to gather real data in urban environments and further validate the hybridization
algorithms.
This document was prepared under the GJU Contract Number
GJU/06/2423/CTR/GUTD.
© Skysoft Portugal, 2007. All Rights Reserved.
Page 26