Giftet President Appreciation

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

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. 2

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)


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 lectureIndoor geolocation system architecture—OFDMAOFDMA signals on S bandOFDMA receiver and measurementsCivil applicationsMeasurements and error sources


OFDMA Indoor Geolocation 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 andTransmitter Design Parameters

spacing between two adjacent tones

fk the frequency of the kth tone

K number of OFDM tones

fs sampling frequency

N number of samples

fRF(i) the ith RF frequency

OOFFDDMMAA SSiiggnnaall SSttrruuccttuurree

FFDDMMAA MMoodduullaattiioonn

OOFFDDMM MMoodduullaattiioonn

ff ((GGHHzz))

ff ((MMHHzz)) ff11 ff22 ff33 ffNN

11sstt TTXX 22nndd TTXX 33rrdd TTXX 44tthh TTXX

22 22..33 22..66 22..99

110000 110011 110022 110099


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 2/(NK)

The second relation is among fs fk, and N

fk/fs 2/N

The theoretical maximum detectable distance is among dmax and fs

dmax = (N–1)c/fs


Crosscorrelation Function

Given

K=10, fs = 500 MHz

= 1 MHz, N = 256

Get

dmax = 153 m

For

= – 435.2, 0, 435.2 nsCrosscorr. peak occursslightly earlier.

Relative distancesTX1 TX2 TX3


OFDMA Geolocation Channel

Rayleigh multipath fading

L number of paths, ah gain, h time delay, and h phase shift


OFDMA Indoor Geolocation Channel

Path lossWe use a free space path loss.A more realistic model is needed

MultipathPath gain distribution slow fading

Rayleigh (most severe)Rician (severe)Lognormal (least severe)

Inter-arrival timesExponential

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

K=10, fs = 500 MHz

= 1 MHz, f1 = 1 MHz

N = 256

1 receiver

Noise power =

10 dB above signalpower

• 1 D OFDMA PIGS• To define design parameters• Initial pseudorange position error assessment


Noiseless OFDMA RF Signal Spectrum

3 OFDMA noiseless signalsin the time domainrepresentation

3 OFDMA noiseless signals in the frequency domainrepresentation

Relative distances


Noisy OFDMA RF Signal Spectrum

3 OFDMA noisy signalsin the time domainrepresentation

3 OFDMA noisy signals in the frequency domainrepresentation

Relative distances


Time Delay Estimation

Actual oa = {434, 0, 436} ns

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

Relative distances

oa1 = 434 ns oa2 = 436 nsTX1

TX2 TX3


Time Delay Estimation cont.

No more than threeiterations are required to estimate the time delay!


Time Delay Estimation cont.

We have repeatedthe experiment1000 times.

= {435.53, 0.4435.03} ns

= {8.4, 0.8, 0.3} ns

TX1TX2 TX3

1= –130.6 m 2= 130.91 m


Pseudorange Estimation

The pseudo-range

= {–130.6, 0.12, 130.91} m

= {2.5, 0.24, 0.08} m

rot cccc

ccc


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, RDefine OFDMA transmitter locations in local x, y, z, tDefine true indoor user trajectory in x, y, z, tDefine OFDMA receiver parameters such as pseudorange or phase noise, filter type such as least squares, and processing typeRun 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 systemThe advantages:

There is a 7.5 GHz bandwidth available for such systemsThe 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.

DisadvantageThe 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

~ 5 min Lab Examples’ Specifications—Area 2 IGS Technologies

~ 5 min Lab Examples’ Specifications—Area 3IGS Service Architecture

~ 5 min Lab Examples’ Specifications—Area 4IGS Management and Information Assurance


Lab Examples’ Specifications—Area 1 RF Engineering, Antennas, and Propagation

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?


Lab Examples’ Specifications—Area 2 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.



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).



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.



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)?


Lab Examples’ Specifications—Area 2 IGS Service Architecture

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?


Lab Examples’ Specifications—Area 4 IGS Management and Information Assurance

Design an indoor geolocation system fault monitoring systemDesign an indoor geolocation system performance monitoring systemDevelop/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 geolocation systems?



Can you describe what are the most common types of information assurance (or security) attacks on indoor geolocation systems?What kind of protocols can be utilized to secure indoor geolocation systems?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 geolocation systems?


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.

Giftet President Appreciation

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