Methods for determining a LOB of one or more user equipment (UE) in a wireless system employing Time Difference of Arrival (TDOA) is described. TDOA techniques are based 051 estimating the difference in the arrival times of reference signals from multiple receivers or from multiple emitters to a receiver. A particular value of the time difference estimate defines a hyperbola between the two receivers on which the handset may exist When the distance between the receiving antennas is small relative to the distance of the emitter source (the handset) being located, then the TDOA is equivalent to the angle between the baseline of the sensors (receivers antennas) and the incident RF energy from the emitter. If the angle between the baseline and true North is known, then the line of bearing (LOB) and/ or angle of arrival (AoA), can be utilised to determine the location of the UE.

Multi-Path Mitigation in Rangefinding and Tracking Objects Using Reduced Attenuation RF Technology

A system and method for managing the provisioning of location information on a mobile communications unit (e.g., a cellular phone) is disclosed. When a request for location information on a particular mobile communications unit is received, the general location of the mobile communications unit may be determined. This general location information may then be used to determine if any position determination equipment site would be able to provide the desired location information. Therefore, a request for location information on a given mobile communications unit is not invoked to a particular position determination equipment site until it has been first determined that the position determination equipment site would in fact be able to provide the desired location information.

Location information management system and method for mobile communications unit

We address the issue of autonomous navigation, that is, the ability for a navigation system to provide information about the states of a vehicle without the need for a priori infrastructure such as GPS, beacons, or a map. The algorithm is known as simultaneous localisation and mapping (SLAM) and it is a terrain aided navigation system (TANS) which has the capability for online map building, and simultaneously utilising the generated map to bound the errors in the navigation solution. Since the algorithm does not require any a priori terrain information or initial knowledge of the vehicle location, it presents a powerful navigation augmentation system or more importantly, it can be implemented as an independent navigation system. Results are first provided using computer simulation which analyses the effect of the spatial density of landmarks as well as the quality of observation and inertial navigation data, and then finally the real time implementation of the algorithm on an unmanned aerial vehicle (UAV).

Autonomous airborne navigation in unknown terrain environments

This paper presents a new approach to GPS-based navigation which offers significant improvement in antijam capability over traditional designs. The algorithms may be implemented at low cost in software in existing and future GPS receivers using, as inputs, postcorrelation I and Q data and, optionally, raw data from other sensors. Traditional systems are not optimal at high jammer-to-signal (J/S) ratios as a consequence of modular design, use of traditional fixed-gain or gain-scheduled tracking loops, and use of artificial moding logic. The approach described here employs a nonlinear filter that operates efficiently at all J/S levels. Filter gains continuously adapt to changes in the J/S environment, and the error covariance propagation is driven directly by measurements to enhance robustness under high jamming and dynamics conditions. Extended-range correlation may be optionally included to increase the code tracking loss-of-lock threshold under high jamming scenarios. Computational complexity is comparable to an extended Kalman filter. Results of hardware-in-the-loop simulations are presented which demonstrate improvements of 15 dB or more in antijam capability relative to traditional designs.

A deeply integrated adaptive GPS-based navigator with extended range code tracking

A positioning and navigation method and system thereof can substantially solve the problems encountered in global positioning system-only and inertial navigation system-only, such as loss of global positioning satellite signal, sensibility to jamming and spoofing, and inertial solution's drift over time, in which the velocity and acceleration from an inertial navigation processor and an attitude and heading solution from an AHRS processor are used to aid the code and carrier phase tracking of the global positioning system satellite signals, so as to enhance the performance of the global positioning and inertial integration system, even in heavy jamming and high dynamic environments and when the GPS satellite signals are not available.

Positioning and navigation method and system thereof

A method for use in vehicle attitude determination includes generating GPS attitude solutions for a vehicle using three or more antennas receiving GPS signals from two or more space vehicles. An inertial navigation system is initialized by setting the attitude of the inertial navigation system to a GPS attitude solution generated for the vehicle and/or the attitude of the inertial navigation system is updated using the GPS attitude solutions generated for the vehicle or GPS estimated attitude error generated for the vehicle. A system for use in vehicle navigation is also provided. The system generally includes three or more GPS antenna/receiver sets associated with a vehicle, an inertial measurement unit that provides inertial measurements for the vehicle, a processing unit of the system having the capability for generating GPS attitude computations for the vehicle using the three or more GPS antenna/receiver sets and signals from two or more space vehicles; the GPS attitude computations include at least one of absolute attitudes and estimated attitude errors. The processing unit of the system also includes a filter for generating estimates of attitude for the vehicle using the inertial measurements from the inertial measurement unit and the attitude computations.

Attitude determination method and system

Multiple pulses of narrow band signals of varying frequency are detected by multiple spaced apart receivers such that average time difference of arrivals of the signals from an item to be located are determined. The average time differences are used to calculate a position of the item to be located with a desired accuracy, such as within one meter in one embodiment. One of multiple receivers or rangers initiates a location process by transmitting a sync pulse. The sync pulse is received by a scout and other rangers. The scout is a small robot which acts as a transponder, sending out its own narrow band return pulse in response to the sync pulse. Each ranger then determines a difference in time between the sync pulse it receives and the return pulse generated by the scout. The location process is then repeated again at different selected narrow band frequencies, and an average of the difference in time at each ranger is determined. Each ranger is networked together via a standard wireless network, and also obtains position information via standard GPS methods. An iterative calculation of the location of the scout is used to improve an estimated position solution. Time difference of arrival between two rangers is expressed as an equation with three unknown variables, x, y and z, which define a position of the scout in three dimensional space. The locus of a point that satisfies this equation is hyperbolic. The iterative calculation uses at least squares approach to improve the estimated position to within a required tolerance.

Narrowband based navigation scheme

A method and a system for providing a substituted timing signal for a missing satellite ephemeris in execution of a RAIM algorithm includes deriving a plurality of position, velocity, and time solutions from a GPS navigation system. The position, velocity and time solutions are derived from a plurality of satellite ephemerides. An atomic clock provides an atomic clock signal. The atomic clock signal is compared to the derived time solutions to arrive at a correction factor. The atomic clock signal is adjusted according to the correction factor to develop an adjusted atomic clock signal. The adjusted atomic clock signal is substituted for a missing satellite ephemeris to execute the RAIM algorithm.

GPS receiver RAIM with slaved precision clock

NASA-Langley has conducted a flight test program evaluating a differential GPS/inertial navigation system's (DGPS/INS) utility as an approach/landing aid. The DGPS/INS airborne and ground components are based on off-the-shelf transport aircraft avionics, namely a global positioning/inertial reference unit (GPIRU) and two GPS sensor units (GPSSUs). Systematic GPS errors are measured by the ground GPSSU and transmitted to the aircraft GPIRU, allowing the errors to be eliminated or greatly reduced in the airborne equipment. Over 120 landings were flown; 36 of these were fully automatic DGPS/INS landings.

Design and Flight Test of a Differential GPS/Inertial Navigation System for Approach/Landing Guidance

A multipath detection method for use in a GPS position determination system includes providing a code pseudorange measurement representative of a range of an antenna to a space vehicle and a carrier phase pseudorange measurement representative of the range of the antenna to the space vehicle. A code-carrier measurement difference is then generated between the code pseudorange measurement and the carrier phase pseudorange measurement. This code-carrier measurement difference is examined to determine if a multipath component is present. If the difference indicates that multipath is likely to be present, use of such measurements in computing position solutions, such as attitude solutions, is avoided. A multipath detection system for carrying out the method is also described.

Brian W. Schipper

Papers

Attitude determination method and system

Narrowband based navigation scheme

GPS receiver RAIM with slaved precision clock

Design and Flight Test of a Differential GPS/Inertial Navigation System for Approach/Landing Guidance

GPS multipath detection method and system