An IM-DD based ranging method and system

Abstract

The present invention discloses a ranging method and system based on IM-DD, which relates to the fields of optical communication and ranging. The method includes: both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock; each terminal calculates the ranging frame transmission time according to the number of transmission clock counts of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and sends it to the other terminal through the IM-DD data transmission channel along with the data stream; each terminal calculates the arrival time of the ranging frame according to the number of reception clock counts of the ranging frame and based on the arrival time of the second pulse of the reception clock and the data stream transmitted through the IM-DD data transmission channel; both terminals calculate their respective pseudorange values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudorange values calculated by the two terminals. The present invention can take into account both ranging accuracy and system cost at the same time.

Description

Technical Field

[0001] The present invention relates to the fields of optical communication and ranging, and particularly to a ranging method and system based on IM-DD. Background Art

[0002] An intensity modulation direct detection (IM-DD for short) optical communication system is one of the most commonly used ways in digital optical communication systems. Its basic structure includes an optical transmitter, a transmission medium (such as optical fiber or free-space optical communication), and an optical receiver. The optical transmitter modulates the baseband digital signal onto the optical carrier through an intensity modulation method by on-off keying (OOK) modulation, and represents information by the presence or absence of the optical signal within each bit time. After the optical signal passes through the transmission medium such as optical fiber or free-space transmission, it reaches the optical receiver. The optical receiver performs envelope detection on the intensity-modulated optical signal, that is, directly recovers the baseband digital signal through a photodetector. The IM-DD optical communication system has significant advantages in terms of cost, reliability, etc., and is widely used in traditional high-speed and long-distance optical communication systems.

[0003] With the development of mobile communication technology, the research on the sixth-generation mobile communication technology (6G) is currently ongoing. The 6G network will be a fully connected world integrating terrestrial wireless communication and satellite communication. By integrating satellite communication into 6G mobile communication, global seamless coverage can be achieved. In the field of satellite communication, the two optional communication methods are wireless communication and optical communication. Compared with each other, the transmission capacity of optical communication is several orders of magnitude larger than that of wireless communication. For the requirements of large-capacity satellite communication such as 6G, the preferred technical route for backbone communication between satellites and between satellites and the ground is optical communication technology. Due to the relatively harsh environment of the satellite operating orbit, the types of components on the satellite are limited, and it is difficult to select components. And due to commercial requirements, there are urgent requirements in terms of cost, service life, etc. Due to the significant advantages of IM-DD optical communication in terms of cost, reliability, etc., for application scenarios mainly deployed with low-earth orbit satellites and requiring large-capacity communication, IM-DD optical communication has become the preferred technical system.

[0004] Obtaining the relative position information between satellites is a prerequisite for ensuring the normal operation of the formation constellation. Therefore, satellites need to complete precise inter-satellite and satellite-ground ranging by themselves to determine the relative state between satellites or the satellite-ground state in the formation constellation. Combining optical communication technology with ranging technology to achieve mutual communication between satellites and between satellites and the ground, and accurately measure the satellite trajectory, has great potential benefits and broad application prospects. However, how to well balance ranging accuracy and system cost is a problem that needs to be solved. Summary of the Invention

[0005] In view of the defects existing in the prior art, the first aspect of the present invention provides a ranging method based on IM-DD, which can take into account both ranging accuracy and system cost.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A ranging method based on IM-DD, the method comprising the following steps:

[0008] Both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock;

[0009] Each terminal calculates the ranging frame transmission time according to the number of transmission clock cycles of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and sends it to the other terminal through the IM-DD data transmission channel along with the data stream;

[0010] Each terminal calculates the arrival time of the ranging frame according to the number of reception clock cycles of the ranging frame and based on the arrival time of the second pulse of the reception clock and the data stream transmitted through the IM-DD data transmission channel;

[0011] Both terminals calculate their respective pseudorange values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudorange values calculated by the two terminals.

[0012] In some embodiments, both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock, including:

[0013] Parallel sampling is respectively performed on multiple taps of the delay chain composed of the transmission clock and reception clock to determine the delay time T of each stage of the delay chain tap ;

[0014] Parallel sampling is performed on multiple taps of multiple delay chains with the number of N TAPS to obtain sampling values D tap [0:N TAPS -1];

[0015] Determine the position n pulse where the logical value jumps;

[0016] According to the formula: T pps =n pulse ×T tap calculate the arrival time T pps_s of the second pulse of the transmission clock and the arrival time T pps_r of the second pulse of the reception clock.

[0017] In some embodiments, when the rising edge of the second pulse is valid, a transition from 0 to 1 is searched for, or when the falling edge of the second pulse is valid, a transition from 1 to 0 is searched for to determine the position n of the logic value transition. pulse 。

[0018] In some embodiments, each terminal sends the clock number according to the ranging frame and calculates the ranging frame transmission time based on the arrival time of the second pulse of the transmission clock, including:

[0019] According to the formula: T s =(n send ×F s ) / (F s_norm ) 2 -T pps_s Calculate the ranging frame transmission time T s , where n send is the ranging frame transmission clock number, F s is the measured clock frequency value of the transmission clock, and F s_norm is the nominal frequency value of the transmission clock.

[0020] In some embodiments, when the arrival flag of the second pulse of the transmission clock is valid, the ranging frame transmission counter is started, and when the ranging frame transmission flag is valid, the ranging frame transmission counter is stopped to obtain the ranging frame transmission clock number n send 。

[0021] In some embodiments, each terminal calculates the ranging frame arrival time according to the ranging frame reception clock number and based on the arrival time of the second pulse of the reception clock and the data stream transmitted through the IM-DD data transmission channel, including:

[0022] According to the formula:

[0023] T r =[(n recv +N r / N BITS )×F r / (F r_norm ) 2 -T pps_r ≈(n recv ×F r ) / (F r_norm ) 2 +N r / N BITS / F r_norm -T pps_r

[0024] Calculate the ranging frame arrival time T r , where n recv is the ranging frame reception clock number, F r is the measured clock frequency value of the reception clock, and Fr_norm is the nominal frequency value of the received clock, N r is the parallel synchronous bit sliding value, N BITS is the parallel data width.

[0025] In some embodiments, when the second pulse arrival flag of the received clock is valid, start the ranging frame reception counter, and stop the ranging frame reception counter when the ranging frame reception flag is valid, so as to obtain the number of ranging frame reception clocks n recv .

[0026] In some embodiments, both of the two terminals calculate their respective pseudo-range values according to the ranging frame arrival time calculated by this terminal and the ranging frame transmission time sent by the other terminal, and calculate the ranging value according to the pseudo-range values calculated by the two terminals, including:

[0027] The first terminal among the two terminals calculates according to the formula: T d1 = T r1 - T s2 to calculate the first pseudo-range value T d1 , where T r1 is the ranging frame arrival time calculated by the first terminal, and T s2 is the ranging frame transmission time calculated by the second terminal;

[0028] The second terminal among the two terminals calculates according to the formula: T d2 = T r2 - T s1 to calculate the second pseudo-range value T d2 , where T r2 is the ranging frame arrival time calculated by the second terminal, and T s1 is the ranging frame transmission time calculated by the first terminal;

[0029] According to the formula: T dist = (T d1 + T d2 ) / 2 to calculate the ranging value T dist .

[0030] In some embodiments, the ranging method further includes:

[0031] Obtain the transmission and processing delays T diterm inside the two terminals;

[0032] According to the formula: T dist_correct = T dist - T diterm correct the ranging value T dist to obtain the ranging correction value T dist_correct .

[0033] The second aspect of the present invention provides a ranging system based on IM-DD, which can take into account both ranging accuracy and system cost.

[0034] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0035] A ranging system based on IM-DD includes at least two terminals, and each of the terminals is configured to:

[0036] Measure the frequencies of the local transmission clock and reception clock using second pulses, and obtain the arrival times of the second pulses of the transmission clock and reception clock;

[0037] Calculate the transmission time of the ranging frame according to the number of transmission clocks of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and send it to the other terminal along with the data stream;

[0038] Calculate the arrival time of the ranging frame according to the number of reception clocks of the ranging frame and based on the arrival time of the second pulse of the reception clock;

[0039] Calculate the respective pseudorange values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudorange values calculated by the two terminals.

[0040] Compared with the prior art, the advantages of the present invention are as follows:

[0041] In the present invention, a high-precision second pulse arrival time measurement method is used, and a data transmission channel of direct modulation and direct detection optical communication is used. A very small amount of ranging information is inserted into the normal data frame transmission. There is no need to interrupt the normal communication mode, nor is it necessary to synchronize the network clock frequency. The transmission period of the data frame does not need to be synchronized with the second pulse either. The two-way one-way ranging method can be used for ranging. In addition, the frequencies of the local clocks are measured using second pulses to correct the ranging process parameters. Therefore, only an ordinary crystal oscillator needs to be used as the local clock source, and the full network synchronous clock signal or high-stability clock source usually required for high-precision ranging can be cancelled, and the ranging accuracy and precision at the time scale of the direct modulation and direct detection communication symbol can be achieved. At the same time, the complexity of the time-frequency synchronization system, the requirements for components, and the cost of the entire communication ranging system are reduced, and the problem that it is difficult to balance the ranging accuracy and system cost in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flowchart of the ranging method based on IM-DD in an embodiment of the present invention;

[0043] Figure 2 It is a structural block diagram of the ranging system in an embodiment of the present invention;

[0044] Figure 3 It is a structural block diagram of the digital logic circuit of the ranging system in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some but not all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0046] See Figure 1 As shown, an IM-DD based ranging method is provided in an embodiment of the present invention. The method includes the following steps:

[0047] S1. Both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock.

[0048] It should be noted that in step S1, mainly the second pulse arrival time measurement method is adopted. Logic circuits with deterministic time delays inside the digital logic circuit are cascaded to form a delay chain. The clock is used to perform parallel sampling on multiple taps of the delay chain. According to the results of the digital logic circuit timing analysis, the delay time T of each stage of the delay chain is determined. tap , for a number of N TAPS parallel sampling of multiple taps of multiple stages of the delay chain to obtain the sampling value D tap [0:N TAPS -1], find the position n where the logic value jumps (if the rising edge of the second pulse is valid, find the jump from 0 to 1, or if the falling edge of the second pulse is valid, find the jump from 1 to 0). pulse , if there is a jump, the second pulse arrival flag FLAG_1PPS is valid. At the same time, it is calculated that the second pulse arrival time is T pps =n pulse ×T tap , where T pps is the arrival time of the second pulse of the clock. The transmission clock and reception clock respectively output the corresponding second pulse arrival times T pps_s and T pps_r , as well as the second pulse arrival flags FLAG_1PPS_S and FLAG_1PPS_R.

[0049] S2. Each terminal calculates the ranging frame transmission time according to the number of transmission clock counts of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and sends it to the other terminal through the IM-DD data transmission channel along with the data stream.

[0050] In this embodiment, the transmission clock uses the second pulse arrival flag FLAG_1PPS_S and outputs the clock frequency measurement value F sAmong them, whenever the arrival flag of a second pulse becomes valid, the previous frequency counting is ended, and the counted value at the end of the counting is output as the measured value F of the clock frequency of the transmission clock. s Meanwhile, the counter is reset and the counting starts again.

[0051] Meanwhile, when the arrival flag FLAG_1PPS_S of the second pulse of the transmission clock becomes valid, the ranging frame transmission counter is started, and when the ranging frame transmission flag becomes valid, the ranging frame transmission counter is stopped to obtain the number of transmission clocks n of the ranging frame. send 。

[0052] Then, according to the formula: T s =(n send ×F s ) / (F s_norm ) 2 -T pps_s the transmission time T of the ranging frame is calculated, where n s is the number of transmission clocks of the ranging frame, F send is the measured value of the clock frequency of the transmission clock, and F s is the nominal frequency value of the transmission clock. s_norm 。

[0053] S3. Each terminal calculates the arrival time of the ranging frame according to the number of received clocks of the ranging frame and based on the arrival time of the second pulse of the received clock and the data stream transmitted through the IM-DD data transmission channel.

[0054] In this embodiment, the received clock uses the arrival flag FLAG_1PPS_R of the second pulse and outputs the measured value F of the clock frequency. r Among them, whenever the arrival flag of a second pulse becomes valid, the previous frequency counting is ended, and the counted value at the end of the counting is output as the measured value F of the clock frequency of the received clock. r Meanwhile, the counter is reset and the counting starts again.

[0055] Meanwhile, when the arrival flag FLAG_1PPS_R of the second pulse of the received clock becomes valid, the ranging frame reception counter is started, and when the ranging frame reception flag becomes valid, the ranging frame reception counter is stopped to obtain the number of received clocks n of the ranging frame. recv 。

[0056] Combined with the parallel synchronous bit sliding value N r , the parallel data width N BITS and the nominal frequency value F of the received clock r_norm , where for the parallel data with random bit positions output by the high-speed serial reception interface, bit sliding adjustment is required to make it conform to the format definition of the data frame, so the parallel synchronous bit sliding value N r is considered in this embodiment.

[0057] Then we can use the formula:

[0058] T r =[(n recv +N r / N BITS )×F r ] / (F r_norm ) 2 -T pps_r ≈(n recv ×F r ) / (F r_norm ) 2 +N r / N BITS / F r_norm -T pps_r

[0059] Calculate the ranging frame arrival time T r , where n recv F is the number of ranging frame receiving clocks, r is the measured value of the clock frequency of the receiving clock, F r_norm is the nominal frequency of the receiving clock, N r is the parallel synchronization bit slip value, N BITS is the parallel data width.

[0060] S4. Both terminals calculate their own pseudorange values based on the ranging frame arrival time calculated by the terminal and the ranging frame sending time sent by the other terminal, and calculate the ranging value based on the pseudorange values calculated by the two terminals.

[0061] Specifically, the first terminal of the two terminals is based on the formula: d1 =T r1 -T s2 Calculate the first pseudorange value T d1 , where T r1 The ranging frame arrival time calculated for the first terminal, T s2 The ranging frame sending time calculated for the second terminal.

[0062] The second terminal of the two terminals is based on the formula: d2 =T r2 -T s1 Calculate the second pseudorange value T d2 , where T r2 The ranging frame arrival time calculated for the second terminal, T s1 The ranging frame sending time calculated by the first terminal. Then according to the formula: T dist =(T d1 +T d2 ) / 2 calculate the distance value T dist .

[0063] In addition, since the calculated ranging value includes the inherent transmission and processing delays T within the two terminals diterm , in the preferred embodiment, in order to obtain a more accurate measurement result, according to the formula: T dist_correct = T dist - T diterm the ranging value T dist is corrected to obtain the ranging correction value T dist_correct .

[0064] Considering that the speed of light in the transmission medium is c’, the ranging distance value D = T dist_correct × c’ can be calculated.

[0065] In summary, in the present invention, the high-precision second pulse arrival time measurement method is used, the data transmission channel of direct modulation and direct detection optical communication is used, a very small amount of ranging information is inserted during normal data frame transmission, without interrupting the normal communication mode, without network clock frequency synchronization, and the sending period of the data frame does not need to be synchronized with the second pulse, and the two-way one-way ranging method can be used for ranging. In addition, the second pulse is used to measure the frequency of the local clock and correct the ranging process parameters. Therefore, only an ordinary crystal oscillator needs to be used as the local clock source, and the full network synchronous clock signal or high-stability clock source usually required for high-precision ranging can be cancelled, and the ranging accuracy and precision at the order of the direct modulation and direct detection communication symbol time can be achieved, while reducing the complexity of the time-frequency synchronization system, the requirements for components, and the cost of the entire communication ranging system, and solving the problem that it is difficult to balance the ranging accuracy and system cost in the prior art.

[0066] At the same time, the present invention also provides a ranging system based on IM-DD, which includes at least two terminals, and the structures and functions of the two terminals are the same. Each terminal is used for:

[0067] Measuring the frequencies of the local sending clock and receiving clock using the second pulse to obtain the second pulse arrival times of the sending clock and receiving clock; calculating the ranging frame sending time according to the number of sending clocks of the ranging frame and based on the second pulse arrival time of the sending clock, and sending it to the other terminal along with the data stream; calculating the ranging frame arrival time according to the number of receiving clocks of the ranging frame and based on the second pulse arrival time of the receiving clock; calculating the respective pseudorange values according to the ranging frame arrival time calculated by this terminal and the ranging frame sending time sent by the other terminal, and calculating the ranging value according to the pseudorange values calculated by the two terminals.

[0068] The following further introduces the terminal in this embodiment:

[0069] See Figure 2As shown in the figure, the terminal 100 in this embodiment includes: a digital logic circuit 101, a directly modulated transmitting optical module 102, and a direct detection receiving optical module 103.

[0070] Among them, the directly modulated transmitting optical module 102 converts an electrical signal into an optical signal using the direct intensity modulation method. The direct detection receiving optical module 103 converts an optical signal into an electrical signal using the direct intensity detection method.

[0071] See Figure 3 As shown in the figure, it is a structural diagram of the digital logic circuit inside a terminal. The digital logic circuit 101 includes: a one-pulse-per-second arrival time measurement module 111, a clock frequency measurement module 112, a ranging frame transmission time calculation module 113, a data frame framing module 114, a high-speed serial transmission interface 115, a high-speed serial reception interface 116, a parallel data synchronization module 117, a data frame deframing module 118, a ranging frame arrival time calculation module 119, a pseudorange calculation module 120, and a ranging calculation module 121.

[0072] Among them, the one-pulse-per-second arrival time measurement module 111 adopts the one-pulse-per-second arrival time measurement method. It cascades logic circuits with deterministic time delays inside the digital logic circuit to form a delay chain, and uses a clock to perform parallel sampling on multiple taps of the delay chain. According to the result of the digital logic circuit timing analysis, the delay time T of each stage of the delay chain is determined tap , for the number of N TAPS parallel sampling is performed on multiple taps of multiple stages of the delay chain to obtain the sampling value D tap [0:N TAPS - 1], find the position n where the logical value jumps (if the rising edge of the one-pulse-per-second is valid, find the jump from 0 to 1, or if the falling edge of the one-pulse-per-second is valid, find the jump from 1 to 0) pulse , if there is a jump, the one-pulse-per-second arrival flag FLAG_1PPS is valid, and at the same time, the one-pulse-per-second arrival time is calculated as T pps = n pulse × T tap , where T pps is the arrival time of the one-pulse-per-second of the clock. The transmitting clock and the receiving clock respectively output the corresponding one-pulse-per-second arrival times T pps_s and T pps_r , as well as the one-pulse-per-second arrival flags FLAG_1PPS_S and FLAG_1PPS_R.

[0073] The clock frequency measurement module 112 adopts the clock frequency measurement method. Whenever a one-pulse-per-second arrival flag is valid, the previous frequency count is ended, and the count value at the end of the count is output as the clock frequency value F s or F r, and at the same time reset the counter and start counting again. The transmission clock and the reception clock each correspond to a clock frequency measurement module, and each uses the corresponding second pulse arrival flags FLAG_1PPS_S and FLAG_1PPS_R, and each outputs the corresponding clock frequency measurement values F s and F r .

[0074] The ranging frame transmission time calculation module 113 adopts a ranging frame transmission time calculation algorithm. When the second pulse arrival flag FLAG_1PPS_S is valid, it starts the ranging frame transmission counter, and stops the ranging frame transmission counter when the ranging frame transmission flag FLAG_S is valid, to obtain the number of ranging frame transmission clock counts n send , and then according to the second pulse arrival time T pps_s based on the transmission clock, the transmission clock frequency value F s and the nominal frequency value F s_norm of the transmission clock, calculate the corrected ranging frame transmission time T s =(n send ×F s ) / (F s_norm ) 2 -T pps_s .

[0075] The data frame framing module 114 forms the input data, the ranging frame transmission time T s , and the pseudorange value T d into a data frame in parallel form according to the data frame format, and when sending a data frame with valid ranging information, outputs the ranging frame transmission flag FLAG_S. This flag uses a certain fixed position of the data frame or other positions with a determined time delay as a reference. Without loss of generality, the frame header or frame tail position can be used as a reference.

[0076] The high-speed serial transmission interface 115 outputs the transmission clock of the parallel data as the working clock of the transmission part, and converts the parallel data into a high-speed serial data stream for output. The high-speed serial reception interface 116 converts the input serial data stream into parallel data, and at the same time outputs the reception clock of the parallel data as the working clock of the reception part.

[0077] The parallel data synchronization module 117 performs bit sliding adjustment on the parallel data with random bit positions output by the high-speed serial reception interface to make it conform to the format definition of the data frame, and outputs the synchronized parallel data and the parallel synchronization bit sliding value N r .

[0078] The data frame deframing module 118 parses out the output data, the ranging frame transmission time T s2 sent by the other terminal, and the pseudorange value T d2 sent by the other terminal according to the format definition of the data frame., when a data frame with valid ranging information is received, the ranging frame reception flag FLAG_R is output. This flag is based on a certain fixed position of the data frame or other positions with a determined time delay. Without loss of generality, it can be based on the frame header or frame tail position.

[0079] The ranging frame arrival time calculation module 119 adopts a ranging frame arrival time calculation algorithm. When the second pulse arrival flag FLAG_1PPS_R is valid, the ranging frame reception counter is started, and when the ranging frame reception flag FLAG_R is valid, the ranging frame reception counter is stopped to obtain the number of received clock cycles n of the ranging frame. recv , based on the arrival time T of the second pulse of the received clock pps_r , and according to the measured value F of the clock frequency of the received clock r , the parallel synchronous bit sliding value N r , the parallel data width N BITS and the nominal frequency value F of the received clock r_norm , calculate the corrected ranging frame arrival time:

[0080] T r = [(n recv + N r / N BITS ) × F r / (F r_norm ) 2 - T pps_r ≈ (n recv × F r ) / (F r_norm ) 2 + N r / N BITS / F r_norm - T pps_r , where T r is the ranging frame arrival time.

[0081] The pseudorange calculation module 120 calculates the pseudorange value based on the ranging frame arrival time calculated by this terminal and the ranging frame transmission time sent by the other terminal. The ranging calculation module 121 is based on the pseudorange value calculated by this terminal and the pseudorange value sent by the other terminal.

[0082] Specifically, the first terminal among the two terminals calculates the first pseudorange value T d1 according to the formula: T r1 = T s2 - T d1 , where T r1 is the ranging frame arrival time calculated by the first terminal, and T s2 is the ranging frame transmission time calculated by the second terminal.

[0083] The second terminal among the two terminals calculates according to the formula: Td2 = T r2 -T s1 Calculate the second pseudorange value T d2 , where T r2 is the arrival time of the ranging frame calculated by the second terminal, and T s1 is the transmission time of the ranging frame calculated by the first terminal. Then, according to the formula: T dist = (T d1 + T d2 ) / 2, calculate the ranging value T dist . And it can also be calculated according to the formula: T skew = (T d1 - T d2 ) / 2 to calculate the second pulse deviation value T skew .

[0084] In addition, since the calculated ranging value includes the inherent transmission and processing delays T diterm inside the two terminals, in the preferred embodiment, in order to obtain a more accurate measurement result, it is also calculated according to the formula: T dist_correct = T dist - T diterm to correct the ranging value T dist to obtain the ranging correction value T dist_correct .

[0085] Considering that the speed of light in the transmission medium is c', the ranging distance value D = T dist_correct × c' can be calculated.

[0086] It should be noted that the pseudorange calculation module 120 and the ranging calculation module 121 respectively implement one step of the two-way one-way ranging method. The resolution and accuracy of the above ranging value are the duration of one symbol of the direct modulation and direct detection communication.

[0087] In summary, the ranging system in the present invention uses a high-precision second pulse arrival time measurement method, uses the data transmission channel of direct modulation and direct detection optical communication, inserts a very small amount of ranging information during normal data frame transmission, without interrupting the normal communication mode, without network clock frequency synchronization, and the data frame transmission period does not need to be synchronized with the second pulse, and the two-way one-way ranging method can be used for ranging. In addition, the second pulse is used to measure the frequency of the local clock and correct the ranging process parameters. Therefore, only an ordinary crystal oscillator needs to be used as the local clock source, canceling the use of the full network synchronous clock signal or the high-stability clock source usually required for high-precision ranging, and the ranging accuracy and precision of the direct modulation and direct detection communication symbol time order can be achieved. At the same time, the complexity of the time-frequency synchronization system, the requirements for components, and the cost of the entire communication ranging system are reduced, and the problem that it is difficult to balance the ranging accuracy and system cost in the prior art is solved.

[0088] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0089] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A ranging method based on IM-DD, characterized in that, The method comprises the following steps: Both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock; Each terminal calculates the transmission time of the ranging frame according to the number of transmission clocks of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and sends it to the other terminal along with the data stream through the IM-DD data transmission channel; Each terminal calculates the arrival time of the ranging frame according to the number of reception clocks of the ranging frame and based on the arrival time of the second pulse of the reception clock and the data stream transmitted through the IM-DD data transmission channel; Both terminals calculate their respective pseudo-range values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudo-range values calculated by the two terminals; Each of the terminals calculates the transmission time of the ranging frame according to the number of transmission clocks of the ranging frame and based on the arrival time of the second pulse of the transmission clock, including: According to the formula: T s =(n send ×F s ) / (F s_norm ) 2 -T pps_s Calculate the ranging frame transmission time T s , where n send is the number of ranging frame transmission clocks, F s is the measured value of the clock frequency of the transmission clock, F s_norm is the nominal frequency value of the transmission clock, and T pps_s is the arrival time of the second pulse of the transmission clock; Each of the terminals calculates the arrival time of the ranging frame according to the number of reception clocks of the ranging frame and based on the arrival time of the second pulse of the reception clock and the data stream transmitted through the IM-DD data transmission channel, including: According to the formula: Calculate the arrival time T of the ranging frame r , where n recv is the number of ranging frame reception clock counts, F r is the measured clock frequency value of the reception clock, F rnorm is the nominal frequency value of the reception clock, N r is the parallel synchronization bit sliding value, N BITS is the parallel data width, T pps_r is the arrival time of the second pulse of the reception clock.

2. The ranging method based on IM-DD according to claim 1, characterized in that, Both terminals to be ranged use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock, including: Parallelly sample the multi-stage taps of the composed delay chain using the transmission clock and the reception clock respectively to determine the delay time T of each stage of the delay chain tap ; Parallel sampling is performed on the multi-stage taps of a multi-stage delay chain with a quantity of N TAPS to obtain a sampling value D tap [0:N TAPS -1]; Determine the position n where the logical value changes pulse ; According to the formula: T pps = n pulse × T tap Calculate the arrival time T pps_s of the second pulse of the transmission clock and the arrival time T pps_r of the second pulse of the reception clock, where T pps is the arrival time of the second pulse of the clock.

3. The ranging method based on IM-DD according to claim 2, wherein: When the second pulse rising edge is valid, look for the transition from 0 to 1, or when the second pulse falling edge is valid, look for the transition from 1 to 0, to determine the position n of the logical value transition pulse 。 4. The ranging method based on IM-DD according to claim 1, characterized in that: When the second pulse arrival flag of the transmission clock is valid, start the ranging frame transmission counter, and stop the ranging frame transmission counter when the ranging frame transmission flag is valid, so as to obtain the number of ranging frame transmission clocks n send .

5. The ranging method based on IM-DD according to claim 1, characterized in that When the arrival flag of the second pulse of the receiving clock is valid, start the ranging frame reception counter, and stop the ranging frame reception counter when the ranging frame reception flag is valid, so as to obtain the ranging frame reception clock count n recv .

6. The ranging method based on IM-DD according to claim 1, wherein Both terminals calculate their respective pseudo-range values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudo-range values calculated by the two terminals, including: The first terminal of the two terminals is based on the formula: d1 =T r1 -T s2 Calculate the first pseudorange value T d1 , where T r1 The ranging frame arrival time calculated for the first terminal, T s2 a ranging frame sending time calculated for the second terminal; The second terminal among the two terminals calculates the second pseudorange value T d2 = T r2 - T s1 according to the formula: T d2 , where T r2 is the arrival time of the ranging frame calculated by the second terminal, and T s1 is the transmission time of the ranging frame calculated by the first terminal; According to the formula: T dist =(T d1 +T d2 ) / 2, calculate the ranging value T dist .

7. The ranging method based on IM-DD according to claim 6, characterized in that The ranging method further comprises: Obtain the transmission and processing delay T inside the two terminals diterm ; According to the formula: T dist_correct = T dist - T diterm The ranging value T dist is corrected to obtain the ranging correction value T dist_correct .

8. A ranging system for implementing the IM-DD based ranging method as claimed in claim 1, characterized in that, Including at least two terminals, each of the terminals is configured to: Use second pulses to measure the frequencies of the local transmission clock and reception clock, and obtain the arrival times of the second pulses of the transmission clock and reception clock; Calculate the transmission time of the ranging frame according to the number of transmission clocks of the ranging frame and based on the arrival time of the second pulse of the transmission clock, and send it to the other terminal along with the data stream; Calculate the arrival time of the ranging frame according to the number of reception clocks of the ranging frame and based on the arrival time of the second pulse of the reception clock; Calculate their respective pseudo-range values according to the arrival time of the ranging frame calculated by this terminal and the transmission time of the ranging frame sent by the other terminal, and calculate the ranging value according to the pseudo-range values calculated by the two terminals.

Images