CLAIM OF PRIORITY

This application claims the benefit of priority of Australia Patent Application No. 2018902520, filed on 12 Jul. 2018, the benefit of priority of which is claimed hereby, and which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

Aspects of the present invention relate to methods and systems for estimating the range between and/or position of objects using a wireless communication system.

BACKGROUND

An accurate position of an object such as a vehicle is required in many applications. Global Navigation Satellite System (GNSS) is an example of a positioning system which uses satellites orbiting around the earth to determine the position of an object at any given time. The GNSS positioning system suffers from multi-path extensions caused by urban canyons. Multi-path extensions are the multiple paths taken by GNSS signals as they bounce off buildings and other infrastructural elements. In addition, GNSS based systems do not work in undercover scenarios, for example in car parks, homes, and tunnels. This is because objects located in undercover scenarios may not be able to connect with enough number of satellites to calculate the object's position. Therefore, the GNSS system is generally augmented with inertial sensors to provide a dead reckoning solution in these challenging scenarios. However, these augmentations, unless corrected, can accumulate errors over time and will lead to increase in measurement errors.

A new generation of terrestrial positioning systems has recently been introduced to determine the position of objects. In particular, these systems determine the distance (referred to as range hereinafter) between an object such as a moving vehicle (whose position is unknown) and one or more infrastructure devices (whose positions are known) and use this measurement to determine the position of the object. The accuracy of the determined range or position depends on the ranging information to these infrastructure devices. The infrastructure devices could be wireless base stations (e.g. LTE eNB, V2X Road Side Units (RSUs), WiFi Access Points (APs) or ultra-wide band (UWB) anchors, Radio broadcast units (RBS), or Video Broadcast Units (VBS)). Different active and passive mechanisms can be used to calculate range to these infrastructure elements (IE). E.g. IEEE Fine timing Measurement (FTM) based active mechanisms can be used to get ranging information for WiFi based devices. Passive mechanisms such as time difference of arrival based ranging estimates can be used in hyperbolic positioning solutions. In a first example, a Wi-Fi station such as a mobile phone sends out periodic broadcast short packets (like IEEE 802.11 Null frames) which are received by different AP's in its vicinity, then the time difference of arrival based positioning solutions can be employed to determine the position of the device. This example assumes that the positioning engine is running in the cloud. In another example of passive mechanism, a station is employed to passively listen to ranging information contained in the IEEE FTM messages between multiple AP's, and utilize this information to determine its position without active participation.

The multi-paths in the wireless communications channel between a transmitter (Tx) and a receiver (Rx) caused by obstructions in the environment severely degrade the ranging performance of such terrestrial systems. Ideally, a ranging solution should know very accurately when it sent a packet (e.g. at antenna port) and when it received a packet in response (e.g. Data and ACK mechanism in IEEE 802.11 systems). In addition, ranging solutions need to remove any standard based delay (e.g. 16 microsecond SIFS time gap (Short Interframe Space time) between a unicast IEEE 802.11 Data and ACK frames). These delays could either be estimated or sent in the configuration or setup messages. Each path delay is proportional to distance the signal has traveled from the Tx to the Rx. If the main line of sight (LOS) path component of the signal is extremely weak because of obstruction, then some other path could be identified as the first path. If ranging is then based on a non-LOS path, then it would cause over-ranging or range extension. This over-ranging can cause position estimation error.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

SUMMARY

In accordance with a first aspect there is provided a method for estimating range between a first device and a second device using at least one wireless communication channel defined between the first and second devices, the method comprising: obtaining a set of range, wherein the range measurements include measurements associated with multiple paths taken by signals between the first and second devices; discarding over-ranges caused by multiple signal paths using a variable threshold; and processing the remaining range measurements to obtain an estimated range.

In accordance with a second aspect there is provided a system for estimating range between a first and a second device using at least one wireless communication channel defined between the first and second devices, the system comprising: a receiver for obtaining the set of range measurements from the first device using the wireless communication channel, wherein the range measurements include measurements associated with multiple paths taken by signals of the wireless communication channel to travel between the first and second devices, and a processor comprising; a module for discarding over-ranges caused by multiple paths using a variable threshold, and a module for processing the remaining range measurements to obtain an estimated range.

In accordance with a third aspect there is provided a computer readable program for estimating range between a first device and a second device using at least one wireless communication channel defined between the first and second devices, the computer readable program including instructions to carry out the method of the first aspect.

In accordance with a fourth aspect there is provided method for estimating position of a first device by estimating range between the first device and a plurality of second devices using wireless communication channels defined between the first and the plurality of second devices, the method comprising: obtaining multiple sets of range measurements corresponding to the plurality of second devices, wherein each of the multiple sets of range measurements include measurements associated with multiple paths taken by signals between the first device and a corresponding second device; discarding, for each set of range measurements, over-ranges caused by multiple signal paths using a variable threshold; processing, for each set of range measurements, the remaining range measurements to obtain estimated ranges corresponding to the plurality of second devices, and processing the estimated ranges corresponding to the plurality of second devices to obtain an estimated position of the first device.

In an embodiment, the discarding of over-ranges is an iterative process and the variable threshold is updated at the end of each iteration.

In an embodiment, the iterative process of discarding over-ranges is stopped when a threshold number of range measurements from the set of range measurements are left below a profile of the estimated range obtained from a previous iteration.

In an embodiment, the threshold number of range measurements is a fixed percentile value of total number of measurements in the set of range measurements.

In an embodiment, a pre-processing step is performed prior to the step of discarding over-ranges.

In an embodiment, the pre-processing step is performed to define a preliminary range profile.

In an embodiment, the pre-processing step comprises filtering over-ranges using a median filter.

In an embodiment, the median filter is configured to filter over-ranges using a window length K and a percentile threshold P_thr.

In an embodiment, the pre-processing step comprises the step of using line or quadratic or spline fit on the set of range measurements to obtain the preliminary range profile.

In an embodiment, the method is used for estimating range when at least one of the devices has a known position to determine the position of the other device.

In an embodiment, the pre-processing step comprises the use of speed measurements to obtain a preliminary range profile, wherein the speed measurements correspond to that one of the first and second devices which is moving.

In an embodiment, a pre-filter is used to filter the set of range measurements to minimize over-ranges caused by multi-path extensions.

In an embodiment, a post-filter is used to filter the estimated range based on standard deviation/variance of the estimated range.

In an embodiment, a post-filter is used to filter the infrastructure elements to be used for positioning.

In an embodiment, the second device is configured to obtain the set of range measurements from the first device.

In an embodiment, the second device is an infrastructure device of the system configured to transmit/receive signals to/from other devices, and the first device is fitted to a vehicle.

In an embodiment, the receiver for obtaining the set of ranges measurements from the first device comprises a range module.

In an embodiment, the module for discarding over-ranges caused by multiple paths is implemented in a range tracker module.

In an embodiment, the module for processing the remaining range measurements to obtain an estimated range is implemented in a position fusion engine.

In an embodiment, the range tracker module is configured to discard over-ranges using an iterative process and the variable threshold is updated at the end of each iteration.

In an embodiment, the range tracker module is configured to stop the iterative process when a threshold number of range measurements from the set of range measurements are left below a profile of the estimated range obtained from a previous iteration.

In an embodiment, the threshold number of range measurements is a fixed percentile value of total number of measurements in the set of range measurements.

In an embodiment, the range tracker module is configured to perform pre-processing of the set of range measurements prior to performing the step of discarding over-ranges.

In an embodiment, the range tracker module is configured to perform pre-processing of the set of range measurements to define a preliminary range profile.

In an embodiment, the range tracker module is configured to perform pre-processing for filtering over-ranges using a median filter.

In an embodiment, the range tracker module is configured to perform pre-processing step using line or quadratic or spline fit on the set of range measurements to obtain the preliminary range profile.

In an embodiment, the range tracker module is configured to perform pre-processing using line or quadratic or spline fit on the median filtered range measurements to obtain the preliminary range profile.

In an embodiment, the system is configured to estimate range either when both the first and second devices are stationary or when one of the devices is moving and the remaining device is stationary.

In an embodiment, the range tracker module is configured to perform pre-processing using speed measurements to obtain a preliminary range profile, wherein the speed measurements correspond to that one of the first and second devices which is moving.

In an embodiment, the system includes a speed module for obtaining the speed measurements of the moving device.

In an embodiment, the system includes a pre-filter module to filter the set of range measurements to minimize over-ranges caused by multi-path extensions.

In an embodiment, the system includes a post-filter module to filter the estimated range based on standard deviation/variance of the estimated range.

In an embodiment, the system includes a post-filter to filter the infrastructure elements to be used for positioning.

