White Paper
Toward the future with much accurate
positioning, navigation and timing technology

Presented by SDR-SAT technology teamKozo Keikaku Engineering, Inc., Tokyo, Japan
http://www.kke.co.jp/en/solution/theme/sdr-sat.html

2018Required Accuracy and theReality
Once the infrastructure is deployed, dozens ofapplications will be invented and become dependingon the system. Additionally, most of the newly
developed applications require much accurate PNTsolution to serve. Automatic driving system is thetypical one. To support such demanding
applications and GNSS generally has someproblems, the most serious one is caused by‘multipath’ radio propagation.

Multipath Radio Propagation

GNSS Constellation in 2018
The human society evolves with technology andthe importance of positioning, navigation andtiming (PNT) systems has been increased
significantly in the recent decades. PNT is now, oneof the most important infrastructure as well as thelegacy ones, such as road, railroad, power grid.
Since the launch of the first generation of GPS inearly 80s, US (Global Positioning System:GPS),
Russia(GLObalNAvigation
Satellite
System:GLONASS) and China (北斗:BeiDou) arecompeting launch of their own satellite system andnow, they seem to have already constructed theirown independent global PNT systems, followed byEU (Galilleo). They are called ‘Global Navigation
Satellite System:GNSS’. Other than that, India has
their own satellite system (Indian Regional
Navigational Satellite System:IRNSS). It covers alimited region and called a regional navigation
satellite system (RNSS). Japan’s Quasi-Zenith
Satellite System (QZSS) is intended to complement
GPS and Galileo to enhance the accuracy ofpositioning in the region.
Until 2020, it is said that GNSS constellation overthe globe will be up to 150 satellites and most of thepopulated area in the middle latitude may becovered with more than 20~25 satellites in 24 hours,
365 days a year. With GNSS receiver which iscapable of multi-GNSS reception, it is expected tohave very precise positioning and timing, except forpolar region where relatively less constellation
covers.

In the urban area, especially in newly developed
countries in Asia region, most of the deployment ofPNT applications are located in urban area, wheremany tall buildings with concrete and iron cover thedense populated area. In that situation, even if they
have more than 20 satellites at the same time on thesky, it would be many chances to have only a few
satellites with direct-path. To locate a receiver as 3D
position, it requires at least four satellite at the sametime. In this urban situation, no precise positioning
can be expected. Actually, the receiver also utilize
no direct-path satellite for positioning in some case,even though it contains multipath delay, caused byreflection on the building’s wall or diffraction on theedge. The delay on the path causes significant error
on the calculation of pseudo-range, which is given
by dividing arrival time duration with the speed oflight (c).

Improve GNSS Receivers
All the GNSS receivers are based on the same
theory and mechanisms. They calculate the range
from each visible satellite through detecting ‘code
phase’. Radio signal from a satellite is coded with asequence of peculiar pseudo random number, whichis called ‘code’. Using correlators to detect the ‘code
phase’ of each satellite, and then, solve the pseudo
range to fix the location using the pseudo range
values of more than four satellites withtrigonometry. This method is called, ‘codepositioning’ or ‘standalone positioning’. The
maximum accuracy could be less than 1 meterunless there is no accuracy decreasing factor, suchas multipath radio propagation.

More Accurate, More Precise, …
As described above, the multipath causes a great
problem in terms of accuracy of PNT system. It may
sometime results tens of meters of positioning error
within an urban canyon district, such as New York,Shanghai, Singapore, Seoul and Tokyo metropolitanarea. This may have serious impact on PNTapplications not just transportations, but also
telecommunication infrastructure, which relies on
precise timing.

The Role of GNSS Signal Generator andGNSS Software Receiver
To achieve much accurate positioning and much
precise timing, universities, national institutes andcorporate research institutes all over the world are

Figure 1 TME’s 2-channel SDR board
tackling with multipath, interference and others.
Depending on the case, sometimes it’s not easy toreproduce the same situation every time it requires.
For example, a specific mix of multipath signals are
merely reproduced again. In this case, record andreplay is the popular tool to help spiral improvement
approach.
On the other hand, in the case when trying toproduce some specific situation on its own, recordand replay is no use. Assume you are in thelaboratory in Beijing, thinking of reproducing somesituation at some place of southern hemisphere. In
this case, GNSS signal generator is the tool for you.

SDR GNSS Signal Generator
Software defined radio (SDR) is a greattechnology, which brings us various benefits. SDR
enables to develop inherently very complex radiosystem with very low cost. Most of the recent
complex radio systems, including GNSS, arecomplex enough and almost impossible toimplement without the help of any software
approach. SDR-SAT accommodates a general
purpose SDR board(s) with two radio channels. Thehardware does nothing with GNSS. It’s just ageneric radio transceiver. Current version of SDRSAT does not use receiver portion of the SDR board.
The SDR board is from TME (TamagawaElectronics Co. Ltd.) and it is composed of two SDR
transceiver chips, AD9364, from Analog Devices,
Inc. SDR-SAT also accommodates GPGPU, which
accelerates the baseband signal processing
significantly and it enables multipath signal
generation with more than 100 paths for eachsatellite.

Comprehensive User Interface
SDR-SAT has an ‘easy-to-use’ intuitive GUI. The
simple, online map-based scenario editor enables tocreate any receiver’s motion with mouse clicks.
With internet connection, the online ‘Open Street
Map (OSM)’ displays any place on the globe whenplaying GNSS signal. It also capable of importing
external comma separated (CSV) format of time,latitude, longitude and height list. User may use
Google Maps to create any route with KML format
and import it as a SDR-SAT scenario.

Figure 4 'Sky Plot' for GNSS Constellation

GUI provides various kind of graphs and charts
including satellites’ Sky-Map, antenna patterns andso on. When generating GNSS signal, a dialog
allows to configure various parameters. They
includes multipath signal environments, noise andor CW jamming synthesis, type of antenna, logging
on/off, and so on.

Current date/time in
GPS time

Current receiver’s position
Progress bar

Figure 3 Signal Generation with 2D MAP Display
Specify the number ofrepetition

Scenario start
time offset (sec)Choose the signal
output mode

Switch On/Off
specific feature orcorrections

Multipath scenario
controls

Additional attenuation
to each satellite’ssignalSelect SDR board
for each channel(SS02T4)
Select DSP hardware
processor (option)

Specify the SDR
device(option)

Push to start signal
outputLog output control

Figure 2 Various Parameters for Signal Generation

Solving Problems in the Real-WorldHardware-in-the-Loop (HIL)
In the automotive world, not just the top
companies in the automotive industry, but also newcomers such as IT giants, are competing tosupremacy of so-called automated driving car. In
these years, many of the mid-range or high-classcars tend to be equipped with certain level of ADAS
(Advanced driver-assistance systems). Companies
have been spending a large amount of budget on
developing those systems every year.
For the development of those systems, simulation
environment is the key component.

Positioning under Jamming /Interference
The infrastructure is becoming more importantand the threat of terrorist attack to PNT
infrastructure is becoming more serious. Once it
happens, many urban functions will be paralyzed
instantly.

Precise Time Synchronization
Recent LTE or 5G base stations are migratingfrom using FDD to TDD for duplexing downlink
and uplink channels, because of the shortage ofbandwidth. With TDD, it’s easier to acquire afrequency which has certain amount of continuous
bandwidth than FDD. However, it requires precise
synchronization of timing among adjacent basestations to avoid unnecessary interference among
them and user equipment. The amount of precision
is 1 microsecond or less than 1 microsecond andthey are now, relying on GNSS. It is known that insome cases in urban environment, multipath GNSS
signal degrade the precision down to 100 nsec.
To mitigate the influence of multipath in urban
canyon environment, researchers are investigating
the method to exclude satellite signals whichcontain more than certain level of multipath signal.
SDR-SAT is used for generating GNSS signals at
any multipath condition.

Protecting the infrastructure from the attacks, oneof the effective way is to detect the attacks and alert
them. Generally, there is no easy way to distinguishinterfered GNSS signal from the non-interfered one.
Nonetheless, researchers are making effort to findthe way of detecting them and preventing or
mitigating the damage. GNSS signal generator is
one of the essential tools. It is capable of generating
any fake navigation message with any waveform, at
any timing, just like terrorists or some crimes
committed for fun. In many cases they should also
use the same kind of technology, based on SDR.

Table 1 SDR-SAT Hardware SpecificationSS02T2

SS02T4

SS02T2OX

Peak Power Range-99dBm~-10dBm (at L1=1575.42MHz)

Frequency Range

GPS L1(1575.42MHz)*1 GLONASS L1(1602.0MHz)*1

SS02T4OX*1 SDR H/W covers all the L band frequency and it’s fully controlled by software.
Number of RF Output

12

External Clock Input-External Sync Output-110MHz, 1pps, GNSS*2*2 Turn on/off DC power supply w/software
10MHz, 1pps

Sampling Frequency

16MHz

Signal Bandwidth

8MHz

Quantization bit

12bit

Reference oscillator

2

TCXO (<0.5ppm)

OCXO (< ±10ppb)

Long Time Stability> 72hours

Power Supply

100V~220V AC(50Hz, 60Hz)

Size (WHD)

W430mm x D522mm x H176

Weight32kg

Processor / FPGAIntel Core i7-6700 (8M Cache 3.40GHz) / Xillinx ZYNQ SoC

DAC

AD9364 x2 with common reference oscillator

Memory8GBStorage

SSD 450GB

Graphic (GPGPU)ELSA GeForce GTX 1080 8GB GLADIAC

OS

Windows 10 Enterprise LTSB 2016 High End 64bit Edition

Table 2 SDR-SAT Interface to External Devices/Equipment
Connector

SS02T2

SS02T4

SS02T2OX

SS02T4OX

RF-OUT1(SMA-J)

SDR RF output 1

SDR RF output 1

SDR RF output 1

SDR RF output 1

RF-OUT2(SMA-J)-

SDR RF output 2-

SDR RF output 2

ANT IN(SMA-J)--

10M OUT(SMA-J)--

Reference Clock 10MHz Output

1PPS OUT(SMA-J)--

Reference Clock 1pps Output

10MHz IN(SMA-J)--

Reference Clock 10MHz Input

1PPS IN(SMA-J)--

Reference Clock 1pps Input

GNSS Signal Input for GPSDO(w/ DC 5V for active antenna)

PWR

100V~220V AC(50Hz, 60Hz)

USB

Hi-Speed(2.0) x2 Super-Speed(3.0) x2

LANGbE x2 * SDR-SAT has to be connected to the Internet

DISPLAY

DVI-D,VGA, HDMI, DisplayPort

AC Power Unit

HDMI/VGA/DVI-D(100V~240VAC)

interfaces

Audio I/FGPS ANT, Ref. Clk. I/O
and GNSS RF out I/F

1GB Ethernet I/Fx2,GPU I/F

USB2.0, USB3.0(usually not used)

Figure 5 SDR-SAT Rear Panel Layout (SDR-SAT SS02T2OX)

Receiver-GNSS Software Receiver for L5/L5S Signaldecoded bits

decoded bits

Figure 8 Tracking Result of GNSS Software Receiver forFigure 7 Decoded signal of L5/L5S Signal with GNSS

L5/L5S signal

Software Receiver

GNSS Software Receiver
Accompanying with GNSS Signal Generator andGNSS multipath radio propagation Simulators,
GNSS Software Receiver is one of the most usefultools for research and development purpose at PNT
community. In addition to the major L1CA signal,
there are some minor radio signals, such as L5,
L5S and L6 signals are broadcasted from some ofthe GNSS satellites.
However, it’s not easy to find a receiver which iscapable of receiving those minor signals. In thiscase, the combination of SDR front-end andSoftware Receiver is the useful tool forresearchers. KKE provides GNSS Software
Receiver for L5/L5S signals written in
MATLABTM, which is based on a free L1CA
receiver program[1] provided with a famous bookby Kai Borre et.al. and the portion of the MATLAB
source code is available under GPL[4]. Current
version is a ‘post-processing’ receiver and supports
various SDR front-end, including Nuand’s
bladeRF[2]andAmungo
Navigation’s
NUT4NT[3]. We’re planning to support NSL’s
STEREO, as well.

Related URLs:[1] https://github.com/gnss-sdr/gnss-sdr[2] https://www.nuand.com/[3] https://www.amungo-navigation.com/nut4nt[4] Under preparation in March 2018. Email tosdrsat@kke.co.jp

Figure 6 Four Channel GNSS Receiver Front
End ‘NUT4NT’ from Amungohttp://www.kke.co.jp