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Systems and methods for a high-precision time of arrival ultra-wideband positioning systemSystems and methods for a high-precision time of arrival ultra-wideband positioning system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070194987, Systems and methods for a high-precision time of arrival ultra-wideband positioning system. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND [0001] Current Ultra-Wideband (UWB) positioning systems typically generate range information using either a time of arrival (TOA) method or a time difference of arrival (TDOA) method. The TDOA method requires a mobile unit needing ranging information to contact one or more reference units, and receive a response from one or more reference units. The mobile unit then calculates each range measurement to generate its own position based on the round trip time required to send a request and receive a response. TDOA can obtain a high degree of accuracy, but has the disadvantage of requiring the mobile unit to possess a transmitter of sufficient power to contact the reference units in addition to being susceptible to severe accuracy latencies during the round trip. The disadvantage of TDOA is that the transmitter adds to the complexity, the weight, size, and power requirements of the mobile unit. [0002] TOA methods calculate position based only on the elapsed time required for a signal having a time tag to travel from the one or more reference units to the mobile unit. Thus, TOA methods eliminate the need for a transmitter in the mobile unit, allowing the mobile unit to be a purely passive receiving device. TOA methods considerably reduce the complexity, the weight, size, and power requirements of the mobile unit. To achieve a high degree of accuracy in arriving at a position solution, a mobile unit employing TOA methods is dependent upon the reference units' ability to accurately generate the time tag information which is transmitted to the mobile unit. High precision oscillators, such as atomic clocks, are expensive and thus not practical for installations deploying a significant number of reference units. Thus, other means must be implemented to mitigate this problem. [0003] For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for methods and systems for realizing affordable, high accuracy TOA based UWB positioning systems. SUMMARY [0004] The Embodiments of the present invention provide methods and systems for methods and systems for realizing affordable TOA based UWB positioning systems and will be understood by reading and studying the following specification. [0005] In one embodiment, a method for generating precision localizer messages for an ultra-wideband time-of-arrival positioning system is provided. The method comprises receiving a signal from an atomically accurate reference; generating a timing signal based on the atomically accurate reference signal; correcting a system time based on the timing signal; and transmitting an ultra-wideband signal having a localization message based on the system time. [0006] In another embodiment, a positioning system is provided. The system comprises one or more reference units each adapted to receive a time signal from at least one atomically accurate reference and maintain a system time based on the time signal, wherein each reference unit is further adapted to transmit a localizer message via an ultra-wideband signal, the localizer message including location information for the reference unit and time information indicating the system time when the localizer message was transmitted; and a mobile receiver unit adapted to calculate a distance to a first reference unit of the one or more reference units based on a first localizer message received from the first reference unit. [0007] In yet another embodiment, a reference unit for a positioning system is provided. The reference unit comprises means for receiving a time signal from an atomically accurate reference; means for generating a periodic timing signal based on the atomically accurate reference signal, the means for generating responsive to the means for receiving; means for maintaining a system time; means for transmitting an ultra-wideband signal having a localization message, wherein the localization message includes location information for the reference unit and time information indicating the system time when the localization message is transmitted; and means for correcting the system time based on a difference between the system time and a time embedded within the timing signal, the means for adjusting responsive to the means for generating a periodic timing signal and the means for maintaining a system time. [0008] In still another embodiment, a computer-readable medium having computer-executable program instructions for a method for generating precision localizer messages for an ultra-wideband time-of-arrival positioning system is provided. The method comprises receiving a signal from an atomically accurate reference; generating a periodic timing signal based on the global atomically accurate reference signal, wherein the timing signal includes a time message that indicates the time the periodic timing is generated; correcting a system time based on a difference between the system time and the time message included within the timing signal; and transmitting an ultra-wideband signal having a localization message based on the system time. DRAWINGS [0009] Embodiments of the present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which: [0010] FIG. 1 is a block diagram illustrating a UWB reference unit of one embodiment of the present invention; [0011] FIGS. 2A and 2B are block diagrams illustrating a UWB positioning system of one embodiment of the present invention; and [0012] FIG. 3 is a flow chart illustrating a method of one embodiment of the present invention. [0013] In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present invention. Reference characters denote like elements throughout figures and text. DETAILED DESCRIPTION [0014] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. [0015] UWB localizers possess the capability of producing centimeter (cm) accuracy positioning solution, however using the TOA method, accurate measurement of time is a necessity. Embodiments of the present invention mitigate the timing errors found in UWB reference units (commonly referred to as UWB localizers) that typically employ cheaper commercial grade oscillators or other low precision means of generating timing signals. [0016] Embodiments of the present invention benefit the users of UWB positioning systems by providing accurate atomic time signals to the UWB reference units from one or more atomically accurate references, so that the a mobile unit can measure and calculate its own position with high accuracy. Embodiments of the present invention provide centimeter-positioning accuracy, at a low cost, benefiting applications such as, but not limited to, personal tracking/positioning systems within buildings, unmanned vehicle localized positioning and automated vehicle guidance/positioning solutions. Other designs reduce the necessity of utilizing a high accuracy time base because they implement the TDOA method, which measures the time it takes to go roundtrip from a UWB reference unit the receiver. TDOA methods however, require timing coordination between the transmitters and receivers, and are influenced by relative clock drifts and processing delays between them. [0017] Embodiments of the present invention take advantage of atomically accurate references that broadcast highly accurate atomic clock based time signals. Examples of such atomically accurate references include global navigation satellite systems (GNSS), such as the Global Positioning System (GPS), for example. For example, the atomically accurate references provided by GPS satellites are achieved with a combination of cesium (Cs) and rubidium (Rb) atomic clocks. GPS satellites provide civilian access to these atomically accurate references through the GPS Standard Positioning Service (SPS), which maintains time transfer signals with an accuracy to coordinated universal time (UTC) within 340 nanoseconds. [0018] FIG. 1 illustrates a UWB reference unit 100 of one embodiment of the present invention. UWB reference unit 100 comprises a UWB-TOA localizer 110 and a UWB antenna 114, a GNSS receiver 120 and GNSS antenna 125, and a local clock 130. In one embodiment, GNSS receiver 120 comprises a chip size GPS receiver. In one embodiment, local clock 130 comprises a low cost crystal oscillator. [0019] In operation, GNSS receiver 120 generates an accurate timing signal based on signals received from at least one GNSS satellite 140, and outputs the timing signal to UWB-TOA localizer 110. In one embodiment, GNSS receiver 120 internally utilizes the timing signal from the GNSS satellites to accurately synchronize its internal time reference with the atomic clock based time signals provided by the GNSS. The timing signal from the GNSS satellite 140 provides the current time based on the GNSS satellite 140's atomic clock. In one embodiment, the timing signal output from GNSS receiver 120 comprises both a periodic timing pulse and a time message that provides the current time. In one embodiment, the periodic timing pulse is a 1 pulse-per-second signal. Although GNSS receiver 120 can generate a timing signal based on a signal received from a single GNSS satellite 140, in other embodiment, the accuracy of the timing signal is increased based on signals from additional GNSS satellites. For example, in one embodiment, where the at least one GNSS satellite 140 includes GPS satellites, an increased accuracy timing signal is generated by GNSS receiver 120 by receiving signals from four or more GPS satellites. As would be appreciated by one skilled in the art, by receiving signals from four or more GPS satellites, GNSS receiver 120 can accurately solve for its own position in three-dimensions and solve for a more accurate time solution than it can based on a signal from a single GPS satellite. [0020] Although FIG. 1 illustrates utilizing a time signal from a GNSS satellite, in other embodiments, other sources for atomically accurate references are used. For example, in one embodiment a UWB reference unit 100 obtains a timing signal via shortwave radio. The National Institute of Standards and Technology (NIST) provides such an atomically accurate reference via shortwave radio that continually broadcasts time signals accurate to within less than 1 microsecond of Coordinated Universal Time (UTC) at the transmitter site. Continue reading about Systems and methods for a high-precision time of arrival ultra-wideband positioning system... Full patent description for Systems and methods for a high-precision time of arrival ultra-wideband positioning system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Systems and methods for a high-precision time of arrival ultra-wideband positioning system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Systems and methods for a high-precision time of arrival ultra-wideband positioning system or other areas of interest. ### Previous Patent Application: Precise local positioning systems using ground-based transmitters Next Patent Application: Analog phase shifter Industry Class: Communications: directive radio wave systems and devices (e.g., radar, radio navigation) ### FreshPatents.com Support Thank you for viewing the Systems and methods for a high-precision time of arrival ultra-wideband positioning system patent info. IP-related news and info Results in 0.11334 seconds Other interesting Feshpatents.com categories: Qualcomm , Schering-Plough , Schlumberger , Seagate , Siemens , Texas Instruments , 174 |
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