Ilir F. Progri

Wireless-enabled GPS indoor geolocation system

In this paper we discuss a wireless-enabled GPS indoor geolocation system which will provide centimeter level position level accuracy 99.999% of the time and meet the integrity requirements in the tough areas such as indoors, undergrounds, and in tunnels in direct response to President Obamas call for building nations best E911 infrastructure emergency response system in the world.

An Anti-Jam GPS Receiver, using Markov Chain, Monte Carlo Integration

An adaptive array algorithm is proposed to mit- igate against the presence of co-channel interference or hos- tile jammers for a GPS receiver. The unknown time and frequency offset estimation for the receiver, employs Markov Chain Monte Carlo (MCMC) integration, utilizing a novel, multi- dimensional, Bayesian, global optimization strategy for initializ- ing a Metropolis-Hastings proposal distribution. The technique enables the design of a high performance multi-user receiver, capable of overcoming the near-far problem, mitigates multipath and interference and provides significantly improved time and frequency estimation performance over standard matched filter algorithm approaches.

An investigation of a DSSS-OFDM-CDMA-FDMA indoor geolocation system

The navigation performance evaluation of a direct sequence spread spectrum (DSSS) orthogonal frequency division multiplexing (OFDM), code division multiple access (CDMA), frequency division multiple access (FDMA) indoor geolocation system is discussed in this paper. This system is an enhancement of a DSSS-CDMA-FDMA indoor geolocation system discussed previously. The OFDM aspect enables the system to achieve high data rate and the FDMA aspect enables the system to achieve higher signal separation; thus, mitigating multipath and eliminating the near-far effect and achieving high data rates. The system theoretical performance and simulations in terms of phase error vs. ideal signal-to-noise ratio (SNR), channel impairments, synchronization time and frequency misalignments are presented in the paper. Based on this preliminary investigation it appears that a DSSS-OFDM-CDMA-FDMA indoor geolocation system can operate with data rate up to 5 MBPS and achieve mm phase errors in an indoor environment with up to 32 transmitters which makes this system very attractive to both indoor communication and navigation applications.

Theoretical Data on Support of a Unified Indoor Geolocation Channel Model

In this paper we present theoretical data in support of the unified indoor geolocation channel model namely (1) path loss and (2) multipath distribution models. First, the path loss model is currently accepted to be a function of the transmitter and receiver geometry and frequency of operation. Second, the most widely used and accepted indoor channel multipath distribution models are Nakagami with m degrees of freedom, Rayleigh, Rician, and lognormal. The purpose of this paper is two fold: (1) to provide a better interpretation of the sets of theoretical data for the indoor channel model and (2) to be able to explain the lack of fit of the well-known multipath distribution models from the previous measurement data sets reported in the literature; thus, providing support for the unified indoor channel model theory. The unified path loss model consists of an approach for linking together the path loss models of the three geolocation systems (macrocellular, microcellular, and indoor) with the distance between the transmitter and receiver, R, and the frequency of operation, f. The path loss caused by increase of the transmitter receiver distance is much more severe than the path loss caused by the path loss caused by increase of the frequency of operation. The bottom line here is that we need to design future receivers or propose a signal structure that will account for 40 to 80 dB of signal degradation indoors. The unified multipath distribution consists of a linear transformation of the well-known multipath distribution models such as Nakagami with m degrees of freedom, Rayleigh, Rician, and lognormal. While it is rather straight forward to prove the unified geolocation multipath distribution model when only the contributing individual distributions are Rayleigh, Rician, and lognormal, if we assume that we have a fourth distribution such as Nakagami with m degrees then the process is not straight forward any more. We will investigate this and report the results in the future. The main purpose of the unified multipath distribution model is to enable the calculations of reflections’ gain. Assuming that the channel is composed of individual distributions such as Rayleigh, Rician, and Lognormal we have perform reflection gain calculations. From the theoretical data it appears that reflections with gain 3dB or higher than the LOS gain are on the order of 1 out of 6.2 days. On the other hand, reflections with gain 5dB greater than the LOS gain are of the order of 1 out of ~6072 years. And this is the most important conclusion of this work that for simulation or implementation purposes we should never consider reflections with gains greater than equal to 5 dB greater than the LOS gain.

Accurate synchronization using a full duplex DSSS channel

In the future, geolocation systems will incorporate the characteristics of communications networks with positioning technologies to create systems capable of performing location aware computing. Such systems have wide applications in troop movements, field hospitals and homeland defense, as well as dual-use areas such as firefighter safety and wireless healthcare systems. Of particular interest are systems which may be deployed in an ad hoc manner. By their very nature, these systems cannot make use of pre-existing infrastructure everything necessary to create a functional system must be self-contained, allowing a complete system to be deployed anywhere, at any time. In many of these applications, there are sub-meter accuracy requirements for indoor positioning. For example, it Is important to differentiate which side of a wall a firefighter is on. To achieve this level of accuracy, work is ongoing which exploits the properties of Orthogonal Frequency Division Multiplexing (OFDM) signals and signal coding to mitigate errors associated with multipath interference. However, even if multipath is eliminated, the ability of a system to provide accurate positioning is also critically related to the ability of the transmitters and receivers in the system to establish a reference time. Current simulations indicate that local synchronization must be within few hundred picoseconds. This paper describes a synchronization mechanism, which employs a duplex Direct Sequence Spread Spectrum (DSSS) signal on a single carrier frequency. Recent results indicate that a Maximum Likelihood Estimator (MLE)-based receiver for DSSS signals yields a significant improvement in receiver dynamic range. By using this increased headroom, and knowledge of the signal being transmitted by a node, it becomes possible to extract other DSSS signals on the same carrier frequency. Once a duplex channel is established, local synchronization can be established to an arbitrary accuracy using coding techniques.

A Unified Geolocation Channel Model--Part II (Multi-path Distribution)

For pt.1 see ibid., p.1148-1161 (2005). In this paper we present a unified channel model which consists of a unified path loss model and a unified multipath distribution model. There are three important components that constitute an indoor geolocation system: (1) transmitter, (2) receiver, and (3) indoor channel model. The unified path loss model consists of an approach for linking together the path loss models of the three geolocation systems (macro, micro, and indoor) with the distance between the transmitter and receiver, R, and the frequency of operation, f. The frequency of these systems varies; hence, the path loss factor varies as well

A MC-CDMA indoor geolocation system

A direct sequence spread spectrum (DSSS), orthogonal frequency division multiple access (OFDM), code division multiple access (CDMA) and frequency division multiple access (FDMA) (or MC-CDMA) indoor geolocation system is presented and discussed in this paper. The data sequence on the transmitter is spread in time using two spreading sequences and then is modulated employing a quadrature phase shift keying (QPSK) scheme. The channel is modeled as a slowly varying frequency-selective, Rayleigh fading channel typical of an indoor office building or factory. The receiver utilizes a non-coherent data demodulator to minimize the sensitivity of the receiver to the Rayleigh fading channel. The bit-error-probability (BEP) performance of this system is compared to that of a DSSS-CDMA-FDMA (or C-CDMA) system when operating in a Rayleigh fading channel with additive white Gaussian noise, range and Doppler shift. Performance results indicate superior performance of the coded MC-CDMA systems of roughly equal transmitter and post RF receiver complexity

A combined GPS satellite/pseudolite system for Category III precision landing

This paper presents the results of a computer simulation, which models a combined GPS, satellite/pseudolite navigation system for precision landing. The goal of this system is to meet the CAT III requirements exploiting a combined system of satellites/pseudolites under severe geometry, weather, and jamming conditions. The simulation includes the aircraft position/velocity estimation and probability of false alarm and misdetection utilizing the satellite and/or the pseudolite navigation system. Aircraft trajectory, GPS satellite constellation, pseudolite location, and the system noise input parameters form the system inputs. The system output is given in terms of the position/velocity estimation error vs. simulation time. Performance measure of the system integrity are also computed and presented. The overall system performance is the combination of the system navigation accuracy and integrity. It is well known that the GPS satellite navigation system lacks vertical information, which results in poor vertical accuracy. On the other hand a pseudolite navigation system provides very good vertical information thus improving the vertical accuracy which is crucial for CAT III precision landing. Both satellite and pseudolite systems are all weather navigation systems, which guarantees optimal performance under any weather conditions. The pseudolite system can perform navigation in the S band or bands different from the L band; therefore, enabling the aircraft landing under severe jamming conditions of the L band.

Performance evaluation of Category III precision landing using airport pseudolites

Further improvements are needed to fulfill the growing demand requirements for a Category III precision landing system architecture, which is completely contained on the airport property. The integrity of an on-airport local area augmentation system can be seriously threatened by failures of the DGPS systems even for a very short time. A pair of airport pseudolites (APLs) will be unable to maintain phase lock and provide navigation solution, if a satellite failure occurs during the navigation solution process. An autonomous system of five airport pseudolites can be used to perform Category III precision landing. The differential carrier phase among them can provide four pairs of independent observable measurements, which are sufficient to solve for integer ambiguity and thus they are able to provide a navigation solution. To insure integrity with a probability of misdetection of 0.001 a system of six airport pseudolites is analyzed and simulated in this paper.

On generalized multidimensional geolocation modulation waveforms

In this paper we discuss generalized multidimensional geolocation modulation waveforms which include: A) State of the Art Geolocation Waveforms: 1. Code Division Multiple Access (CDMA); 2. Frequency Division Multiple Access (FDMA); 3. Orthogonal Frequency Division Multiplexing (OFDM); 4. Frequency Code Division Multiple Access (FCDMA); 5. Multicarrier Code Division Multiple Access (MCCDMA); 6. Orthogonal Frequency Division Multiple Access (OFDMA); 7. Binary Offset Carrier (BOC); 8. Alternate Binary Offset Carrier (AltBOC); 9. Time Modulated/Composite Binary Offset Carrier (TM/C-BOC). B) Giftet Inc Beyond State of the Art Multidimensional Geolocation Waveforms: 10. Variable Binary Offset Carrier (VBOC); 11. Frequency-Binary Offset Carrier-Code Division Multiple Access (F-BOC-CDMA); 12. Frequency-Alternate Binary Offset Carrier-Code Division Multiple Access (F-AltBOC-CDMA); 13. Frequency-Time Modulated/Composite Binary Offset Carrier-Code Division Multiple Access (F-TM/C-BOC-CDMA); 14. Frequency-Variable Binary Offset Carrier-Code Division Multiple Access (F-VBOC-CDMA); 15. Multicarrier- Binary Offset Carrier-Code Division Multiple Access (MC-BOC-CDMA); 16. Multicarrier- Binary Offset Carrier Code Division Multiple Access (MC-AltBOC-CDMA); 17. Multicarrier-Time Modulated/Composite Binary Offset Carrier-Code Division Multiple Access (MC-TM/C-BOC-CDMA); 18. Multicarrier-Variable Binary Offset Carrier-Code Division Multiple Access (MC-VBOC-CDMA); 19. Variable OFDMA or VOFDMA; and finally 20. Dr. Progris generalized multidimensional geolocation waveform GMVBOCW. in direct response to United States DoD GPS, European Galileo, Russian GLONASS, Chinese Compass, Indian IRNSS in the L-band (1-2 GHz), in direct response to the United Nations International telecommunications Union (ITU) for a standardization of GNSS or geolocation waveforms in the S-band (2-4 GHz), C-band (4-8 GHz) and X-band (8-12 GHz).On generalized multidimensional geolocation modulation waveforms.