Giftet President Appreciation

OFDMA INDOOR GEOLOCATION
SYSTEMS

Prepared and Presented by
Ilir F. Progri, Ph.D., President and CEO Giftet Inc
2180 Spencer Ave, Pomona, CA 91767
www.giftet.com
Presented at
IEEE BTS 2008, 7 November 2008
Cal Poly Pomona, Bronco Student Center, Ursa Major Suite
3801 W. Temple Ave., Pomona, CA 91768, Building 35

OFDMA Indoor Geolocation Systems--Copyright © 2008 by Giftet Inc. All rights reserved.

Overview

Introduction to indoor geolocation systems (Lecture ~5 min)
OFDMA indoor geolocation systems (Lecture ~30 min)
Lab example guidelines which cover realistic OFDMA
indoor geolocation systems. (Lab ~20 min)
Certificate and evaluation (~5 min)

OFDMA Indoor Geolocation Systems--Copyright © 2008 by Giftet Inc. All rights reserved. 2

Introduction to Indoor Geolocation
Systems
Objectives: Provide an introduction about the course, Giftet
Inc.
Duration ~5 min lecture
Obtain a quick overview of Giftet® Inc.
Discuss course set-up, materials, and logistics
Lecture ~30 min
Lab ~20 min
Administrative ~5 min
Provide a “big picture” view of the course ahead.


Giftet® Inc

Giftet® mission is to become the premier corporation for researching,
developing, marketing, and distributing global navigation, software,
and web solutions for Indoor Geolocation Systems, GPS, GLONASS,
Galileo, QZSS, and other Global Satellite and/or Pseudolite Navigation
(or Positioning and/or Timing) Systems based on customer’s needs
through innovation, leadership, strong collaboration and partnership.
Giftet philosophy is based on partnership!
Giftet welcomes partnership!
Building successful partnership one client at a time and one project at a
time!
Giftet was founded on December 26, 2006, Pomona, CA.
For more information please visit http://www.giftet.com/


The “Big Picture” View

The goal of this course is:
(1) to introduce pseudolite geolocation systems;
(2) to classify the state of the art geolocation systems;
(3) to identify the issues with the state of the art indoor geolocation systems;
and
(4) to propose and assess three Giftet Inc. pseudolite indoor geolocation
systems.
It was assessed that the classic GPS and GLONASS signal structures
were inadequate to overcome two main design concerns:
(1) the near-far effect and
(2) the multipath effect.


The “Big Picture” View Cont.

We propose Giftet Inc. indoor geolocation systems as
alternative solutions to near-far and multipath effects which
are:
(2) OFDMA pseudolite indoor geolocation systems
OFDMA system is researched, discussed, and analyzed
based on its principle of operation, its transmitter design, the
indoor geolocation channel, its receiver design, issues
associated with obtaining an observable to achieve indoor
navigation, and preliminary indoor simulation results.


The “Big Picture” View Cont.

Our simulation assessment of the system concludes the
following:
An OFDMA indoor geolocation system is another potential
candidate with a totally different signal structure than the C-
CDMA indoor geolocation systems and offer overall
centimeter level position and velocity accuracy 99.9 % of
the time.


Courtesy of GPS World

Introduction Cont.

The main engineering issue with building such a system is
the availability of a suitable infrastructure; thus, a portable
ad-hoc network would be desirable.
Such a network, would consist of ground-based transmitters
(or pseudolites) and portable (or handheld) receivers.
As a typical application of such as system, consider a
situation in which firefighters perform a rescue operation in
a building, which is on fire.


Introduction Cont.

Suppose that we can symbolically describe the rescue mission of
firefighters (or emergency personnel) either operating in the same floor
or operating in different floors.
In a severe fire, smoke, and/or interference environment it is imperative
that each of these firefighters must know the relative position of his
peers and be able to communicate with them.
Moreover there are people outside the building who conduct and
coordinate the mission who must know the same.
Therefore, we recognize three specific situations: (1) outdoor-indoor, (2)
the same floor, and (3) in between floors.


Same Floor Different Floor

Introduction Cont.

From the technical (or engineering point of view) in order to accomplish
these missions we propose a pseudolite based indoor geolocation system
(with navigation and untethered communication capabilities) which
consists of three segments:
the pseudolite segment
the control segment
the user segment.
The pseudolite segment consists of all pseudolites, which are positioned
on precise locations on the ground and continuously transmit a spread
spectrum geolocation signal modulated on a known carrier frequency.


Introduction Cont.

Suppose that the location of each pseudolite is known but each
pseudolite clock bias remains unknown.
Therefore, the problem of uploading the pseudolites’ clock biases from
the control segment or from neighboring pseudolites is relatively simple.
When the location of pseudolites is however unknown then an algorithm
to determine the location of pseudolites in place is required before
attempting to determine the location of the receiver (or firefighter).
Although the problem of relative synchronization between pseudolites is
a main concern to these systems and it will be addressed in another
tutorial.


Introduction Cont.

The control segment consists of one or more monitoring (or base)
stations on the ground, which continuously monitor the pseudolites and
keep track of the reference time. Presumably this is the segment under
the supervision of the commanding unit.
It is conceivable that the control segment must be synchronized to the
Global Positioning System (GPS) time or some other reference time.
The study and design of the control segment is not the objective of this
work.
When the position of each pseudolite is known then the control segment
(or base station) needs only to upload the clock corrections to each
pseudolite.


Introduction Cont.

When the location of each pseudolite is however unknown
then base-stations are required to determine the location of
each pseudolite first and then upload the pseudolite clock
corrections.
The user segment consists of all the receivers (at least one
receiver is mounted on one firefighter) every one of which
tracks and computes its 2-D or 3-D position and local time
based on the signals coming from at least three or more
neighboring pseudolites.


Issues

It is well known that when employing GPS for outdoor
applications only code separation is required to achieve the
desired channel separation on the receiver side because the
near-far effect is insignificant.
The near-far effect is known as the interference of one or
more pseudolite signals during the acquisition and tracking
of a particular pseudolite signal different from the
interfering pseudolite signals; i.e., the near-far effect is
directly linked with the multiple-access (or adjacent)
interference.


Issues

However, because of the GPS signal weakness (amplitude or code
design), the acquisition and tracking of GPS signals inside buildings are
uncertain.
Any of the state-of-the-art DSSS-CDMA indoor geolocation systems,
which are based only on multi-code techniques, cannot eliminate the
near-far effect without pulsing the transmitter’s signal.
Any of the state-of-the-art DSSS-CDMA pseudolite indoor geolocation
systems transmit the signal during a defined fraction of the pulsing
period. And to some extent, these systems cannot successfully exploit
the multipath for indoor applications.


There are four reflective surfaces (the
number of reflective surfaces is not
important), one receiver, and I
transmitters (or Tr).
The signal broadcast from one of the
transmitters can be received either
directly, through the line of sight path
(LOS) or indirectly through a
secondary path.
The receiver contains J channels and
one channel is designed to track only
one signal coming from a particular
transmitter.
For ease of analysis we have assumed
a one to one correspondence between
the receiver’s channels and the
transmitters; i.e., J = I.
Nevertheless, in general the number
of channels does not have to equal
the number of transmitters and vice
versa.


OFDMA Indoor Geolocation
Systems
Objective: This section introduces the main features of
OFDMA indoor geolocation systems. Many themes for the
course are established in this section, to be explored in detail
in later sections.
Duration ~30 min lecture
Indoor geolocation system architecture—OFDMA
OFDMA signals on S band
OFDMA receiver and measurements
Civil applications
Measurements and error sources


Systems
Examples
Position estimation with pseudoranges
Precise position with accumulated carrier phase
Examples using MATLAB


Introduction—OFDMA

FCC approval of Feb. 14, 2002
UWB systems are allowed
Below 960 MHz
Between 3.1 GHz and 10 GHz

OFDMA System Architecture

The OFDMA signal spectrum
OFDMA Transmitter receiver architecture (or configuration)


OFDMA Signals on S band

OFDMA transmitted signal is a superposition of sinusoids (tone
bandwidth < 40 kHz) equally spaced by D (MHz)
The OFDM tones must have the same initial phase!


OFDMA Signal Spectrum and
Transmitter Design Parameters
∆ spacing between two adjacent OFDMA Signal Structure
tones
fk the frequency of the kth tone FDMA Modulation
1st TX 2nd TX 3rd TX 4th TX
K number of OFDM tones
fs sampling frequency 2 2.3 2.6 2.9 f (GHz)
N number of samples OFDM Modulation
fRF(i) the ith RF frequency ∆

f1 f2 f3 fN f (MHz)
100 101 102 109


Design Parameters Relation

The design parameters for an OFDMA pseudolite indoor geolocation
system are: ∆, fs, fk, dmax, N, and K
The relationship among them is defined as follows:
The first relation is among ∆, fs, N, and K
∆/fs ≤ 2π/(NK)
The second relation is among fs, fk, and N
fk/fs ≅ 2π/N
The theoretical maximum detectable distance is among dmax and fs
dmax = (N–1)c/fs


Crosscorrelation Function
Given Relative distances
TX1 TX2 TX3
K=10, fs = 500 MHz
∆ = 1 MHz, N = 256
Get
dmax = 153 m
For
τ = – 435.2, 0, 435.2 ns
Crosscorr. peak occurs
slightly earlier.

OFDMA Geolocation Channel

Rayleigh multipath fading
L number of paths, ah gain, τh time delay, and θh phase shift


Channel
Path loss
We use a free space path loss.
A more realistic model is needed
Multipath
Path gain distribution slow fading
Rayleigh (most severe)
Rician (severe)
Lognormal (least severe)
Inter-arrival times
Exponential
Phase of multipath signals (uniform)


OFDMA Receiver Block Diagram

Position x, y, z, t
Velocity vx, vy, vz, t
Geospatial map
Digital terrestrial chart


Theoretical Performance

Receiver’s front end and IF sampling
Digital signal processing
Navigation performance evaluation

Receiver’s front end and IF sampling


Receiver Measurements and
Navigation Performance
Time delay estimation is a direct measurement of the
relative time between an OFDM transmitter and OFDM
receiver.
Pseudorange estimation is a direct measurement of the
relative time between an OFDM transmitter and OFDM
receiver.
Pseudorange error is a direct measurement error from
subtracting the true range from the pseudorange.
Phase error is a direct measurement error which results from
a fraction of the carrier phase cycle.


Civil Applications—OFDMA PIG
System Example
3 transmitters • 1 D OFDMA PIGS
K=10, fs = 500 MHz • To define design parameters
• Initial pseudorange position error
∆ = 1 MHz, f1 = 1 MHz assessment
N = 256
1 receiver
Noise power =
10 dB above signal
power

Noiseless OFDMA RF Signal
Spectrum
Relative distances
3 OFDMA
noiseless signals
in the time domain
representation

3 OFDMA
noiseless signals
in the frequency domain
representation


Noisy OFDMA RF Signal
Spectrum
Relative distances
3 OFDMA
noisy signals
in the time domain
representation

3 OFDMA
noisy signals
in the frequency domain
representation


Time Delay Estimation
Relative distances
TX TX2 TX
1 3
τoa1 = −434 ns τoa2 = 436 ns
Actual
τoa = {−434, 0, 436} ns

The crosscorrelation
function between
the received signal and
the locally generated
IF signal.


Time Delay Estimation cont.

No more than three
iterations are
required to estimate
the time delay!


Time Delay Estimation cont.
TX1 TX2 TX3
We have repeated
the experiment
1000 times.

µτ= {−435.53, 0.4 µρ1= –130.6 m µρ2= 130.91 m
435.03} ns

στ= {8.4, 0.8, 0.3} ns


Pseudorange Estimation

The pseudo-range
ρ = c ⋅ τ = c ⋅ τ t + c ⋅ τo + c ⋅ τ r
τ = µ τ ± στ
ρ = c ⋅ τ = c ⋅ µ τ ± c ⋅ σ τ = µ ρ ± σρ
µ ρ= {–130.6, 0.12, 130.91} m
σ ρ= {2.5, 0.24, 0.08} m


A scenario of four transmitter 3D OFDMA
pseudolite indoor geolocation system can
achieve 2.3 cm on x and y coordinates and 7.8
cm on z level positioning accuracy 99.9 % of the
time (or 3.1 sigma value) using carrier phase.


Examples using MATLAB

Simple simulation examples using MATLAB should include
the following:
Define design parameters from the maximum detectable range, R
Define OFDMA transmitter locations in local x, y, z, t
Define true indoor user trajectory in x, y, z, t
Define OFDMA receiver parameters such as pseudorange or phase
noise, filter type such as least squares, and processing type
Run the trajectory and estimate the user’s 3D position in x, y, z (m)
vs. time (s) and also the true user’s position error in x, y, z (m) vs. t
(s)
Plot simulation results and also compute simple statistical position
error parameters.


Conclusions

It is possible to design an OFDMA indoor geolocation system
The advantages:
There is a 7.5 GHz bandwidth available for such systems
The design of an OFDMA indoor geolocation system may appear
comparable to the design a GPS-like indoor geolocation system.
The pseudo-range error of an OFDMA indoor geolocation system is about
2.3 m (1 s) which is much better than the accuracy of a GPS like indoor
geolocation system.
A scenario of four transmitter 3D OFDMA pseudolite indoor geolocation
system can achieve 2.3 cm on x and y coordinates and 7.8 cm on z level
positioning accuracy 99.9 % of the time (or 3.1 sigma value) using carrier
phase.
Disadvantage
The theoretical maximum detectable range depends on the number of
OFDM tones (or frequencies) and on the sampling frequency.


Lab Examples

Objective: Lab example specifications include combining the above
practices in hands on examples, homework, and exercises to realistic
design problems of indoor geolocation systems.
Duration ~ 20 min = 10:35AM – 10:55AM.
~ 5 min Lab Examples’ Specifications—Area 1
RF Engineering, Antennas, and Propagation
IGS Technologies
IGS Service Architecture
IGS Management and Information Assurance


Lab Examples’ Specifications—Area 1

Calculate path loss for various RF transmission systems (examples
might include between isotropic or dipole reference antennas, base
station to mobile station, base station to repeater, LOS/NLOS paths, and
clutter losses) and under varying atmospheric conditions (examples
might include inversion layers, ducting, and variations in K factor).
Evaluate the effects of different fading models (examples might include
Rayleigh, Rician and lognormal) and empirical path loss models on the
received signal strength in various signal propagation environments
(examples might include flat terrain, rolling hills, urbanized areas, and
indoor environments [such as buildings or tunnels] with losses caused
by walls, ceilings, and other obstructions).



Calculate and evaluate the effects on the received signal of path-related
impairments, such as Fresnel Zone blockage, delay spread, and Doppler
shift of a signal received by a moving receiver.
Calculate the polarization mismatch loss for various antenna systems
(examples might include mobile radio systems).
Evaluate receive diversity gain for selection, equal gain, and maximal
ratio diversity system configurations.
Determine parameters related to antennas or antenna arrays (examples
might include pattern, beamwidth, gain, distance from an antenna or
array at which far field conditions apply, spacing, beam forming, tilt,
and sectorization) and analyze the effects of these parameters on
coverage.



Determine appropriate antenna spacing at base station sites
to prevent inter-system and intra-system interference effects,
taking into account required radiation patterns and mutual
coupling effects.
Generate and evaluate coverage and interference prediction
maps for indoor geolocation systems.
Develop a procedure to optimize the coverage of a radio
system using propagation modeling and “drive test”
measurements.



Develop a block diagram of an indoor geolocation system
employing standard modules (examples might include
filters, couplers, circulators, and mixers) and/or use lumped
or distributed matching networks, microstrips, and stripline.
Make RF system measurements (examples might include
swept return loss to determine antenna system performance,
transmitter output power [peak or average, as appropriate],
signal-to-noise ratio at a receiver front end, and co-channel
and adjacent channel interference for specific types of signal
spectra).



Can you differentiate between different types of losses? (examples
might include transmission line loss, antenna gain, connector losses, and
path loss)
Would you be able to follow procedures to calculate antenna gain and
free space path loss?
Can you explain statistical fading models such as Rayleigh, Rician, and
Lognormal and distance-power (path loss) relationships in different
propagation environments?
How do you take into account the effects of outdoor terrain and indoor
structures such as walls, floors, and ceilings on signal propagation?



What indoor and outdoor coverage calculation and
verification techniques are currently been used on indoor
geolocation systems?
Can you explain and take into account the following Es/N0,
Eb/N0, RSSI, NF, and other system parameters?
Can you assess the relationship between receiver noise
figure, noise temperature, and receiver sensitivity and the
relationship between sensitivity under static conditions and
the degradation of effective receiver sensitivity caused by
signal fading in different propagation conditions?



What other external noise sources and their impact on the S/
N ratios of received signals, and of techniques for measuring
the impact of external noise?
Would you explain basic antenna system design and use
including antenna types (examples might include
omnidirectional, panel, parabolic, dipole array, indoor
antennas), antenna patterns, gain and ERP, antenna size,
antenna polarization, receive and transmit diversity
(examples might include MIMO) antenna systems, and
proper antenna installation to provide for coverage,
interference mitigation, and frequency reuse?



What adaptive antenna methods and techniques are more suitable for
indoor geolocation systems? Why?
What is the purpose of subscriber unit, mobile, and device antennas and
their performance characteristics on indoor geolocation systems?
Can you illustrate the use of test equipment such as network analyzers,
spectrum analyzers, scopes, and TDRs on indoor geolocation systems?
How do you perform co-channel and adjacent channel interference
analysis and measurement methods and techniques?
Can you provide an example where filters, power dividers, combiners,
and directional couplers are used in the lab for testing an indoor
geolocation system transmitter or receiver?


IGS Technologies

Analyze multiple access schemes for various indoor
geolocaiton systems technologies.
Analyze spectrum implications in indoor geolocation
systems access system design (examples might include
applications, TDD/FDD, inter-modulation, LOS/NLOS,
coverage/capacity).
Analyze design considerations and perform system design to
eliminate coverage holes and to optimize capacity/coverage
in urban/indoor areas.


IGS Technologies

Design an indoor geolocation system (examples might
include pseudolite placements and channel selection)
according to given bandwidth requirements, coverage, and
other considerations.
Test indoor geolocation system devices with respect to
interference issues in various operating environments
(examples might include OFDMA).
Perform co-location interference analysis for indoor
geolocation systems (examples might include OFDMA).


IGS Technologies

Compute the required bandwidth for an indoor geolocation
system given certain network conditions (examples might
include BER, flow count, and protocols in use).
Analyze the tradeoffs between various indoor geolocation
systems technologies (examples might include bandwidth
versus BER) of various error detection and correction
techniques.
Analyze the tradeoffs between various indoor geolocation
systems technologies (examples might include bandwidth
versus power efficiency) and capacity implications of
various power control schemes.


IGS Technologies

Calculate frequency re-use factor.
Design fundamental elements/attributes of indoor
geolocation systems (examples might include OFDMA).
Can you explain the difference among multiple access and
multiplexing schemes (examples might include OFDMA)?
Is there a need for indoor geolocation systems technology
standards and their evolution (examples might include
OFDMA)?



What error detection and correction techniques are more
suitable for indoor geolocation systems?
What are the major components of an indoor geolocation
system topology?
How is mobility management handled on indoor geolocation
systems?



Analyze service platforms including service enablers
(examples might include messaging and positioning) and
service creation/delivery (examples might include Open
Service Access and Parlay).
Design and test quality of service (QoS) (examples might
include design and plan for adequate resources, selecting
priority schemes, queuing strategies, and call administration
control) for VoIP and IMS-based services.



Select and test a load-balancing scheme.
Analyze ad hoc routing and mesh protocols, and suitability for various
deployment scenarios.
Perform capacity planning using traffic engineering principles.
Perform error tracking and trace analysis on protocol control messages
for specific systems.
Analyze the evolution of indoor geolocation systems.
Can you explain different location and positioning techniques?
How do you compute error tracking and what kind of trace analysis
techniques do you perform?



Design an indoor geolocation system fault monitoring
system
Design an indoor geolocation system performance
monitoring system
Develop/specify types and methods of alarm reporting for
an installation.
Compute availability and reliability metrics from both the
“indoor geolocation system performance” and “indoor
geolocation system designer” perspectives (related to
equipment failure).



Assess the potential impacts of known information
assurance (or security) attacks on indoor geolocation
systems (examples might include virus, worm, DoS, and
impersonation).
Plan corresponding solutions to known information
assurance (or security) attacks.
Monitor, log, and audit information assurance (or security)-
related data.
Analyze information assurance (or security) vulnerabilities
and prepare/recommend corrective actions.



Can you qualitatively and quantitatively explain the
importance of quality of service (QoS) monitoring and
control?
Are you able to assess fault management in the context of an
indoor geolocation system?
Can you define configuration management?
How would you use authentication, authorization, and
accounting (AAA) principles and mechanisms on indoor



Can you describe what are the most common types of
information assurance (or security) attacks on indoor
What kind of protocols can be utilized to secure indoor
What are security-violation events logging and monitoring?
What would be a typical security issue management and
resolution?
What are some of the indoor geolocation systems
management protocols?



What performance metrics pertinent to various access
indoor geolocation systems can be utilized?
Are IP security, Encapsulation Security Payload (ESP),
Internet Key Exchange, and digital signature the only safety
measures to secure indoor geolocation systems?
How effective MIB, RMON, and Internet Control
Messaging Protocol (ICMP)?
Are Intrusion Detection Systems, DDoS Attacks, and
traceback techniques effective means for protecting indoor


Certificate and Course Evaluation

Objective: Also at the end of the course each student will
receive a certificate. This certificate can be used as part of
your OFDMA Indoor Geolocation Systems proficiency!
At the end of this course each student is essentially
achieving the OFDMA Indoor Geolocaiton Systems
proficiency level II (intermediate level).
At the end of this course each student is also asked to fill out
the course evaluation form.


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