CN116243291B - A method for unilateral bidirectional distance measurement - Google Patents
A method for unilateral bidirectional distance measurementInfo
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- CN116243291B CN116243291B CN202211093662.9A CN202211093662A CN116243291B CN 116243291 B CN116243291 B CN 116243291B CN 202211093662 A CN202211093662 A CN 202211093662A CN 116243291 B CN116243291 B CN 116243291B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
- G01S11/02—Systems for determining distance or velocity not using reflection or reradiation using radio waves
- G01S11/08—Systems for determining distance or velocity not using reflection or reradiation using radio waves using synchronised clocks
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Mobile Radio Communication Systems (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The invention relates to a unilateral two-way ranging method, wherein a communication signal between an initiator and a responder is a wireless signal containing a preamble sequence, and the unilateral two-way ranging method comprises the following steps of sending a first message to the responder, recording the first message text sending time T A1, receiving a second message replied by the responder, recording the second message receiving time T A2, wherein the second message comprises the first message receiving time T B1 and the second message text sending time T B2, estimating the clock frequency difference between the initiator and the responder according to the preamble sequence of the second message, and calculating the distance between the initiator and the responder based on the first message text sending time T A1, the second message receiving time T A2, the first message receiving time T B1, the second message text sending time T B2 and the clock frequency difference. The invention can reduce the number of the system interaction messages and the complexity of the system under the condition of ensuring the ranging precision.
Description
Technical Field
The invention relates to the technical field of wireless ranging, in particular to a unilateral two-way ranging method.
Background
Wireless ranging systems are widely used in electromagnetic systems of various systems, typically Ultra Wideband (UWB) ranging systems. Because civil equipment generally does not adopt a high-precision atomic clock, a unified high-precision clock does not exist between the receiving end and the transmitting end and the ranging, and in addition, due to the difference of crystal oscillators, a certain frequency difference exists between the clocks at the receiving end and the transmitting end. In order to accurately estimate the time of flight T prop, the unknowns of the other two systems, namely the initial clock difference Δt and the system frequency difference, need to be considered, so that the system has three unknowns to solve.
Existing ranging methods include single-sided two-way ranging (SS-TWR) and double-sided two-way ranging (DS-TWR).
The SS-TWR realizes ranging by respectively sending a message at the receiving and transmitting ends, and the ranging formula is as follows:
Tprop＝(Tround-Treply)/2
The ranging method can solve the problem of initial clock difference, but does not consider the influence of system frequency difference on ranging, and the system frequency difference can cause the gradual change of the clock difference of the system in the ranging process due to the time required by message interaction, so the ranging error is larger. The ranging error of SS-TWR is proportional to both the relative crystal oscillator frequency difference between the devices and the duration of the ranging message response.
The DS-TWR is a ranging method widely applied at present, and the influence of initial clock difference and system frequency difference can be almost eliminated by exchanging three messages between the receiving end and the transmitting end. The ranging formula is:
the DS-TWR distance measurement error basically eliminates the influence caused by the system frequency difference, and can reach the relative error better than 1e-5, but DS-TWR needs to interact with messages back and forth three times, and the complexity of the system is increased.
Disclosure of Invention
The invention aims to solve the technical problem of providing a unilateral two-way ranging method which can reduce the number of system interaction messages and the complexity of a system under the condition of ensuring the ranging precision.
The technical scheme adopted by the invention for solving the technical problems is that a unilateral two-way ranging method is provided, a signal communicated between an initiator and a responder is a wireless signal containing a preamble sequence, and the method comprises the following steps:
Sending a first message to a response party, and recording the sending time T A1 of the first message;
Receiving a second message replied by a response party, and recording second message receiving time T A2, wherein the second message comprises first message receiving time T B1 and second message text sending time T B2;
Estimating a clock frequency difference between the initiator and the responder according to the preamble sequence of the second message;
Calculating the distance between the initiator and the responder based on the first text messaging time T A1, the second message receiving time T A2, the first message receiving time T B1, the second text messaging time T B2 and the clock frequency difference
The estimating the clock frequency difference between the initiator and the responder according to the preamble sequence of the second message specifically includes:
counting radian of local carrier ring rotation in preamble receiving stage
Counting the number N of the received preamble symbols;
Based on the duration T s, carrier period T c, and the radians of each preamble symbol And the number of preamble symbols N, estimating the clock frequency difference between the initiator and the responder.
The calculation formula for estimating the clock frequency difference Δf AB between the initiator and the responder is as follows:
Also included in the second message is a clock frequency difference Δf BA between the initiator and responder estimated by the responder.
Before calculating the distance between the initiator and the responder based on the first text sending time T A1, the second text receiving time T A2, the first text receiving time T B1, the second text sending time T B2 and the clock frequency difference, the method further includes:
And carrying out weighted average on the clock frequency difference Deltaf BA between the initiator and the responder estimated by the responder and the clock frequency difference between the initiator and the responder estimated according to the preamble sequence of the second message, and taking the result after weighted average as the clock frequency difference adopted when calculating the distance between the initiator and the responder.
The calculation formula for calculating the distance between the initiator and the responder based on the first text sending time T A1, the second text receiving time T A2, the first text receiving time T B1, the second text sending time T B2 and the clock frequency difference is as follows:
Wherein T prop is the estimated time of flight between the initiator and the corresponding party, Δf is the clock frequency difference, D is the distance between the initiator and the corresponding party, and c is the speed of light.
Advantageous effects
Compared with the prior art, the method has the advantages that the accuracy of SS-TWR ranging is improved optimally, the ranging accuracy which can be achieved by the DS-TWR ranging method for three times can be achieved through two times of message transmission, the receiving and transmitting clock frequency difference estimation obtained by carrier loop estimation is introduced into a ranging estimation algorithm by combining carrier loop estimation parameters and a ranging flow, the influence of clock frequency difference in the ranging process is removed, and the ranging accuracy of the SS-TWR is improved on the premise that the ranging message does not need to be additionally increased.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention;
Fig. 2 is a schematic diagram of a receiver carrier tracking loop configuration.
Detailed Description
The application will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application. Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the teachings of the present application, and such equivalents are intended to fall within the scope of the application as defined in the appended claims.
The embodiment of the invention relates to a unilateral two-way ranging method, wherein a communication signal between an initiator and a responder is a wireless signal containing a preamble sequence, as shown in fig. 1, the unilateral two-way ranging method comprises the steps of sending a first message to the responder, recording the sending time T A1 of the first message, receiving a second message replied by the responder, recording the receiving time T A2 of the second message, wherein the second message comprises the first message receiving time T B1 and the second message sending time T B2, estimating the clock frequency difference between the initiator and the responder according to the preamble sequence of the second message, and calculating the distance between the initiator and the responder based on the sending time T A1 of the first message, the receiving time T A2 of the second message, the first message receiving time T B1 of the second message, the sending time T B2 of the second message and the clock frequency difference. According to the method, the distance measurement accuracy almost consistent with that of the DS-TWR distance measurement method can be achieved only by exchanging the messages twice, the number of the system interaction messages is reduced, and the complexity of the system is reduced.
The inventor of the invention notices that the DS-TWR needs to perform three message interactions, namely, taking the flight time T prop, the initial clock difference delta T and the system clock frequency difference delta f as unknowns, three equations can be obtained by three message measurements, and therefore, the solution of all unknowns is realized.
In the wireless signal receiving process, the relative frequency difference between the receiving end and the transmitting end consists of two parts, namely, the relative frequency difference of signals caused by the crystal oscillator frequency of the receiving end and the transmitting end and the Doppler frequency shift caused by the relative motion of the receiving end and the transmitting end, and in a common civil environment, the relative speed is lower (generally less than 30 m/s), and the maximum relative Doppler frequency shift is less than 1e-7 and can be basically ignored. Therefore, the relative frequency difference between the receiving end and the transmitting end is mainly determined by the relative frequency difference of crystal oscillators of the receiving end and the transmitting end, and the clock signal and the radio frequency carrier signal of the receiver are obtained by carrying out a plurality of times of frequency multiplication on the reference frequency of the crystal oscillator, so that the relative frequency difference of the clock and the relative frequency difference of the radio frequency carrier are consistent.
In many communication systems, the header of a wireless signal contains a preamble, the preamble is a predetermined sequence, a receiving end can track a carrier and a code loop by tracking the preamble sequence, the carrier loop can track the carrier continuously and correct the phase of the signal, and the code loop mainly tracks the signal code synchronously and corrects the code offset.
For UWB systems, the preamble sequence is periodically repeated several times, each time called a preamble symbol.
Fig. 2 shows a basic carrier digital tracking loop structure of a receiver, which is composed of a carrier phase correction module, an accumulator, a carrier phase detector and a loop filter. The carrier phase correction module carries out phase rotation on the input signal according to the output of the loop filter, the accumulator stacks the results of different preamble symbols, the data of the current input symbol and the data of the accumulator are subjected to inner product, then the phase deflection angle can be obtained, and the phase deflection angle is sent into the loop filter for filtering. The carrier loop filter ensures that each symbol can be superimposed in phase by continuously modifying the phase of the input signal.
The receiving end receives the preamble from the beginning to the end of the preamble, and the local carrier ring rotates togetherThe radian, the number of a commonly received preamble symbol is N, the duration of each preamble symbol is T s, and the carrier period is T c, so that the relative frequency difference between the transmitting end and the receiving end can be accurately estimated as follows:
The relative frequency difference Δf is estimated using the preamble sequence only, and may be estimated during any one of the message receptions, or may be estimated separately for each of the message receptions, and then weighted average, it must be noted that if the frequency difference estimated by device a with respect to device B is Δf, then the expected value of the frequency difference estimated by device B with respect to device a should be- Δf, if Δf is greater than zero, indicating that the clock of device B is running faster than device a, and conversely if Δf is less than zero, indicating that the clock of device B is running slower than device a. The relative frequency differences in the present embodiment refer to the frequency difference measured from the device a with respect to the device B. Based on the actual experimental results, the relative frequency difference estimated from the preamble sequence is very accurate and generally does not require multiple averages.
After the estimation of the relative frequency difference is obtained, the ranging estimation formula can be improved on the basis of the SS-TWR ranging process:
Tprop＝(Tround*(1+Δf)-Treply)/2
The improved estimation formula basically removes errors caused by inconsistent clock frequencies between the device A and the device B, so that a ranging result almost consistent with DS-TWR three ranging can be obtained by transmitting messages only twice.
The whole ranging process is as follows:
1. ranging is performed between a device A and a device B, wherein the device A is an initiator, and the device B is a responder. The signal communicated between device a and device B is a wireless signal containing a preamble reference sequence.
2. The device A sends a message 1 to the device B, and records the local sending time as T A1, wherein the local sending time is the sending time of the first message.
3. The device B receives the message 1, and records the local receiving time as T B1, where the local receiving time is the first message receiving time.
4. Optionally, device B estimates the clock frequency difference between device a and device B from the preamble sequence in message 1. The estimation method comprises counting radian of local carrier ring rotation in preamble receiving stageCounting the number N of received preamble symbols, wherein the duration of each preamble symbol is known to be T s, the carrier period is T c, and the method is carried out byThe relative frequency difference between the transmitting end and the receiving end is estimated.
5. The device B sends the message 2 to the device a, where the message 2 carries a first message receiving time T B1 and a sending time T B2 of the message 2, that is, a sending time of the second message. Optionally, the message 2 may also carry the relative frequency difference Δf BA.
6. The device a receives the message 2, records the local receiving time as T A2, which is the second message receiving time, and obtains the first message receiving time T B1, the second message textually sending time T B2, and the optional relative frequency difference Δf BA.
7. Device a estimates the clock frequency difference Δf AB between device a and device B from the preamble sequence in message 2, the estimation method is consistent with step 4, and optionally, device a performs weighted average according to Δf AB and Δf BA:
If no weighted averaging is performed, Δf=Δf AB.
8. Device a estimates the distance between device a and device B as:
Where T prop is the estimated time of flight between the initiator and the corresponding party, D is the distance between the initiator and the corresponding party, and c is the speed of light.
It is not difficult to find that the invention optimizes and improves the accuracy of SS-TWR ranging, and can realize the ranging accuracy which can be achieved by the DS-TWR ranging method through twice message transmission and three times message, and the method provided by the invention combines carrier loop estimation parameters and ranging flow, the receiving and transmitting clock frequency difference estimation obtained by carrier loop estimation is introduced into a ranging estimation algorithm, so that the influence of the clock frequency difference in the ranging process is removed, and the ranging precision of the SS-TWR is improved on the premise that no additional ranging message is required.
Claims (5)
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101251594A (en) * | 2008-04-03 | 2008-08-27 | 北京航空航天大学 | Two-way ranging and time comparison processing terminal |
| CN107566070A (en) * | 2017-09-04 | 2018-01-09 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | The method of one-way synchronization transmission time frequency |
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| CN101313501B (en) * | 2005-12-09 | 2013-03-20 | 桥扬科技有限公司 | Frequency correction method in a multi-carrier communication system, mobile device and base station |
| US10177809B1 (en) * | 2016-12-12 | 2019-01-08 | DecaWave, Ltd | Receiver for use in an ultra-wideband communication system |
| CN108632105A (en) * | 2017-03-24 | 2018-10-09 | 中兴通讯股份有限公司 | A kind of frame time delay detecting method and system |
| CN110658498B (en) * | 2019-09-02 | 2022-05-24 | 中国航天系统科学与工程研究院 | Time-frequency synchronization method for networked radar system |
| CN113311384B (en) * | 2021-04-29 | 2023-11-10 | 中国人民解放军国防科技大学 | A method and device for unilateral and bidirectional distance measurement |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101251594A (en) * | 2008-04-03 | 2008-08-27 | 北京航空航天大学 | Two-way ranging and time comparison processing terminal |
| CN107566070A (en) * | 2017-09-04 | 2018-01-09 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | The method of one-way synchronization transmission time frequency |
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