CN103648161B - Code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging method, device and system - Google Patents
Code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging method, device and system Download PDFInfo
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Abstract
The invention discloses a code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging method, a code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging device and a code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging system which can reduce ranging errors so as to improve positioning accuracy. The method comprises the following steps that: positioning signals transmitted by upstream equipment are received, wherein the positioning signals simultaneously bear code division multiple access (CDMA) signals for positioning and orthogonal frequency-division multiplexing (OFDM) signals for positioning and are obtained in a manner that the upstream equipment couples the code division multiple access (CDMA) signals and the orthogonal frequency-division multiplexing (OFDM) signals; the positioning signals are parsed such that the code division multiple access (CDMA) signals are obtained; the positioning signals are parsed such that the orthogonal frequency-division multiplexing (OFDM) signals can be obtained; and ranging can be carried out according to the code division multiple access (CDMA) signals and the orthogonal frequency-division multiplexing (OFDM) signals. According to the code division multiple access and orthogonal frequency-division multiplexing signal coupling ranging method, device and system of the invention, the positioning signals simultaneously bear the code division multiple access (CDMA) signals for positioning and the orthogonal frequency-division multiplexing (OFDM) signals for positioning are received, such that the ranging can be carried out through simultaneous application of the code division multiple access (CDMA) signals and the orthogonal frequency-division multiplexing (OFDM) signals, and therefore, the ranging errors can be decreased, and the positioning accuracy can be improved.
Description
Technical Field
The invention relates to the field of computers, in particular to a method, a device and a system for coupling and ranging code division multiple access and orthogonal frequency division multiple access signals.
Background
Positioning services have widely entered people's lives and become an indispensable part in economic construction and social life. For example, indoor positioning technologies based on Wireless Fidelity (Wi-Fi), Ultra Wide Band (UWB), pseudolite, and other systems have been applied locally, and positioning can be achieved in an environment (generally within tens of meters) close to a node.
When positioning service is realized, distance measurement is often required, and the positioning accuracy is affected by the distance measurement error. Therefore, how to reduce the range error to improve the positioning accuracy is a problem to be solved currently.
Disclosure of Invention
The embodiment of the invention provides a method, a device and a system for distance measurement by coupling code division multiple access and orthogonal frequency division multiple access signals, which can reduce the distance measurement error and improve the positioning precision.
The embodiment of the invention adopts the following technical scheme:
a code division multiple access and orthogonal frequency division multiple access signal coupling ranging method comprises the following steps:
receiving a positioning signal sent by upstream equipment, wherein the positioning signal simultaneously carries a Code Division Multiple Access (CDMA) signal for positioning and an orthogonal frequency division multiple access (OFDM) signal for positioning, and the upstream equipment couples the CDMA signal and the OFDM signal to obtain the positioning signal;
analyzing the positioning signal to obtain the CDMA signal;
analyzing the positioning signal to obtain the OFDM signal;
performing ranging according to the CDMA signal and the OFDM signal;
performing ranging according to the CDMA signal and the OFDM signal includes:
the CDMA signal is used for capturing the first path and the multipath outside the chip, and the CDMA signal is used for tracking the first path and the multipath outside the chip to reproduce the first path and the multipath outside the chip;
calculating a multipath error correction term according to a multipath signal reproduction result;
according to the multipath error correction term, correcting a frequency domain code sequence obtained by FFT of a received signal;
performing pseudo-range calculation based on the corrected received signal;
calculating a multipath error correction term according to a multipath signal reproduction result includes: according to the multipath signal reproduction result, the following formula is applied to calculate the multipath error correction term,
wherein q is the number of off-chip multipaths obtained by CDMA tracking, diRepresenting a code adopted by an ith subcarrier of the OFDM signal; j represents an imaginary part; t is the time length of the OFDM ranging coincidence; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispDelay time of the p path signal;
according to the multipath error correction term, correcting the frequency domain code sequence obtained by FFT of the received signal comprises the following steps: according to the multipath error correction term, the frequency domain code sequence obtained by FFT of the received signal is corrected by applying the following formula,
Zi＝Yi(Xi-Δi)*；
wherein,is a complex sequence XiConjugation of (1); y isiIs a frequency domain code sequence on each subcarrier.
A code division multiple access and orthogonal frequency division multiple access signal coupling distance measuring device comprises:
a receiving module, configured to receive a positioning signal sent by an upstream device, where the positioning signal simultaneously carries a CDMA signal for positioning and an OFDM signal for positioning, and the positioning signal is obtained by coupling the CDMA signal and the OFDM signal with the upstream device;
the first analysis module is used for analyzing the positioning signal to obtain the CDMA signal;
the second analysis module is used for analyzing the positioning signal to obtain the OFDM signal;
the ranging module is used for ranging according to the CDMA signal and the OFDM signal;
the distance measurement module is used for capturing the first path and the multipath outside the chip by using the CDMA signal, tracking the first path and the multipath outside the chip by using the CDMA signal and reproducing the first path and the multipath outside the chip; calculating a multipath error correction term according to a multipath signal reproduction result; according to the multipath error correction term, correcting a frequency domain code sequence obtained by FFT of a received signal; performing pseudo-range calculation based on the corrected received signal;
the ranging module applies the following formula to calculate a multipath error correction term,
wherein q is the number of off-chip multipaths obtained by CDMA tracking, diRepresenting a code adopted by an ith subcarrier of the OFDM signal; j represents an imaginary part; t is the time length of the OFDM ranging coincidence; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispDelay time of the p path signal;
the ranging module is used for correcting the frequency domain code sequence obtained by FFT of the received signal according to the multipath error correction term by applying the following formula,
Zi＝Yi(Xi-Δi)*；
wherein,is a complex sequence XiConjugation of (1); y isiIs a frequency domain code sequence on each subcarrier.
A code division multiple access and orthogonal frequency division multiple access signal coupling ranging system comprises an upstream device and a ranging device, wherein:
the upstream device is used for coupling a CDMA signal for positioning and an OFDM signal for positioning to generate a positioning signal for simultaneously carrying the CDMA signal and the CDMA signal; transmitting the positioning signal to the ranging device;
the distance measuring device is the distance measuring device.
Based on the above technical solution, the distance measuring method, device and system of CDMA and ofdma signal coupling according to the embodiments of the present invention receive a positioning signal that is sent by an upstream device and simultaneously carries a CDMA signal for positioning and an OFDM signal for positioning; analyzing the positioning signal to obtain the CDMA signal; analyzing the positioning signal to obtain the OFDM signal; and performing ranging according to the CDMA signal and the OFDM signal. Therefore, by receiving the positioning signal which simultaneously bears the CDMA signal for positioning and the OFDM signal for positioning, the CDMA signal and the OFDM signal are simultaneously applied to carry out distance measurement, thereby reducing the distance measurement error and improving the positioning precision.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a flowchart of a ranging method for cdma and ofdma signal coupling according to embodiment 1 of the present invention;
fig. 2 is a schematic diagram of a cdma and ofdma signal coupling ranging apparatus according to embodiment 2 of the present invention;
fig. 3 is a flowchart of a ranging method for cdma and ofdma signal coupling according to embodiment 2 of the present invention;
fig. 4a is a schematic structural diagram of an OFDM signal data frame according to embodiment 2 of the present invention;
fig. 4b is a schematic structural diagram of a positioning signal provided in embodiment 2 of the present invention;
fig. 4c is a schematic diagram of an OFDM ranging signal multiplexing method according to embodiment 2 of the present invention;
fig. 5 is a schematic structural diagram of a cdma and ofdma signal coupling distance measuring apparatus according to embodiment 3 of the present invention;
fig. 6 is a flowchart of a positioning message transmission method according to embodiment 4 of the present invention;
fig. 7 is a schematic structural diagram of a positioning message transmission apparatus according to embodiment 5 of the present invention;
fig. 8 is a schematic structural diagram of a cdma and ofdma signal coupling ranging system according to embodiment 6 of the present invention;
FIG. 9 is a diagram illustrating a comparison of CDMA and OFDM multipath error envelopes in accordance with an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example 1
As shown in fig. 1, a cdma and ofdma signal coupling ranging method according to an embodiment of the present invention includes:
110. receiving a positioning signal sent by an upstream device, where the positioning signal simultaneously carries a CDMA (code division Multiple Access) signal for positioning and an OFDM (Orthogonal frequency division Multiple Access) signal for positioning, and the positioning signal is obtained by the upstream device coupling the CDMA signal and the OFDM signal.
120. The positioning signal is analyzed to obtain the CDMA signal.
130. And analyzing the positioning signal to obtain the OFDM signal.
140. And performing ranging according to the CDMA signal and the OFDM signal.
The execution body of the 110-140 may be a distance measuring device, which may include a plurality of modules or devices to implement the method.
The distance measuring method of the embodiment of the invention receives a positioning signal which is sent by upstream equipment and simultaneously bears a CDMA signal for positioning and an OFDM signal for positioning; analyzing the positioning signal to obtain a CDMA signal; analyzing the positioning signal to obtain an OFDM signal; and performing ranging according to the CDMA signal and the OFDM signal. Therefore, the CDMA signal and the OFDM signal are simultaneously applied to ranging by receiving the positioning signal which simultaneously bears the CDMA signal for positioning and the OFDM signal for positioning, so that the ranging error can be reduced, and the positioning precision is improved.
Example 2
In this embodiment, a specific implementation process of the ranging method according to the embodiment of the present invention is described in detail by taking the ranging device architecture coupled with cdma and ofdma signals shown in fig. 2 as an example, it should be understood that the application scenario shown in fig. 2 is only for facilitating understanding of the ranging method according to the embodiment of the present invention, and should not be construed as limiting the embodiment of the present invention.
The ranging apparatus architecture for cdma and ofdma signal coupling shown in fig. 2 comprises: a CDMA signal detection module 21, configured to detect and analyze a CDMA signal; a weak energy CDMA signal tracking module 22, configured to track a weak energy CDMA signal in the positioning signal; an OFDM symbol demodulation module 23, configured to demodulate an OFDM symbol; and an OFDM ranging signal detection module 24, configured to detect an OFDM ranging signal.
For CDMA signals, multipath does not affect ranging when the multipath delay exceeds (1+ d) chips, where d is the spacing of the CDMA correlators. For OFDM, short delay multipath has less effect on ranging, but long delay multipath, which has no effect on CDMA ranging, still has an effect on OFDM ranging. Therefore, the advantages of both can be coupled, and multipath error mitigation is performed.
As shown in fig. 3, the ranging method for cdma and ofdma signal coupling provided in this embodiment includes:
210. the distance measuring device receives a positioning signal sent by an upstream device, the positioning signal simultaneously carries a CDMA signal for positioning and an OFDM signal for positioning, and the positioning signal is obtained by coupling the CDMA signal and the OFDM signal by the upstream device.
In the embodiment of the invention, when a structure of a positioning signal (such as a TC-OFDM signal) is constructed, a CDMA navigation signal is added on the premise of not influencing the normal service of OFDM, the same-frequency common-load of the CDMA and OFDM signals is realized, the CDMA navigation signal is used as a distance measurement main channel, the OFDM signal is used as an auxiliary channel, and the wireless distance measurement precision under the environment of multipath and the like is improved through the coupling of the CDMA and OFDM signals.
As shown in fig. 4a, the OFDM traffic channel is composed of three systems, i.e., a frame, a slot, a beacon and an OFDM symbol, where one frame is composed of multiple slots, and each slot includes a beacon and multiple OFDM symbols, where the beacon is used for system synchronization and base station identity identification, and the traffic information is carried by the OFDM symbols. In the design of TC-OFDM signals, correct receiving of OFDM symbols cannot be influenced, so that normal operation of existing services is guaranteed.
Optionally, the CDMA signal includes a CDMA pilot and a CDMA navigation signal carrying a navigation message, the OFDM signal includes an OFDM ranging signal and at least one OFDM symbol, the positioning signal includes a beacon portion and a data carrying portion, and the CDMA signal for positioning and the OFDM signal for positioning are coupled in the above-mentioned 110, so that when the positioning signal is generated, the CDMA pilot and the OFDM ranging signal can be carried in the beacon portion, and the at least one OFDM symbol and the CDMA navigation signal can be carried in the data carrying portion, so as to generate the positioning signal.
For example, the signal structure per slot of the positioning signal in the embodiment of the present invention is shown in fig. 4 b.
The positioning signal (e.g., TC-OFDM signal) is newly designed for the existing beacon portion without changing the frame structure of the existing traffic system. Because the OFDM signal and the CDMA signal have complementary characteristics in multipath channel ranging, the beacon part adopts CDMA pilot frequency to carry out system synchronization and also reserves a period of time to carry the OFDM ranging signal for coupling ranging with the CDMA, thereby improving the ranging accuracy in multipath environment. And the rest part of the OFDM symbol is superposed with the CDMA navigation signal with low energy, time and frequency measurement can be carried out through long-time integration, and a navigation message is carried. The CDMA navigation signal and the OFDM symbol carrying normal service are simultaneously carried at the same frequency, and the normal receiving of the OFDM symbol is not influenced by the control of signal energy.
The signals of the various parts of the positioning structure shown in fig. 4b play a role as follows:
CDMA pilot frequency: and occupying part of time in the beacon, and adopting a short pseudo code sequence for quick time synchronization of the time slot signal. Different base stations are distinguished by different spreading codes. The CDMA pilot frequency can select Gold codes with good self-correlation and cross-correlation characteristics, and the code length can be designed according to the available time length of the beacon and the system bandwidth.
OFDM ranging signal: the method is used for carrying out decimal part time delay fine measurement and carrier frequency estimation in an OFDM ranging mode. The OFDM ranging signal is modulated with a specific code sequence in the frequency domain by IFFT (Inverse Fast Fourier Transform) and then transmitted in the time domain. Different base station signals are distinguished by different times, and each time slot can configure k base station signals according to the available time of the beacon, as shown in fig. 4 c. The OFDM ranging signal can be used for supplementing with a CDMA navigation signal, and the ranging precision of the system in a complex environment is improved. (in the embodiment, k is 3)
Weak energy CDMA navigation signal: can be used for fine synchronization of system carrier waves; CDMA long-time integration and fine tracking ranging; navigation messages are carried. The partial signals are transmitted at the same frequency with the OFDM symbols by adopting low energy, the energy does not influence the normal demodulation of the OFDM symbols, but high integral gain can be obtained by carrying out long-time integration on the CDMA signals, and the CDMA tracking distance measurement and the navigation message broadcasting are realized. (in the embodiment, the CDMA navigation signal is selected to be weak 18dB with the OFDM signal)
OFDM symbol: the modulation mode of OFDM service symbols of the existing system is not changed, and the compatibility of a service receiving part of the system is ensured.
The navigation message is carried by the weak energy CDMA navigation signal, and in order to ensure enough spread spectrum gain, 1 or more time slots can carry 1bit message information according to the time slot lengths of different OFDM service systems. Each frame of navigation message information comprises complete information necessary for navigation, and the navigation message frame and the OFDM service frame keep an integral multiple relation in time length in consideration of system consistency. The navigation message in the embodiment of the invention comprises at least one of the following:
the method comprises the following steps of base station number, base station coordinates, fixed time delay correction parameters, clock error compensation parameters, OFDM ranging signal parameters, barometric altimetry correction parameters, synchronization information and verification information.
Wherein, the base station number is used for identifying the identity of the base station; the base station coordinates are used for representing the position of a central phase point of a transmitting antenna of the base station; the fixed time delay correction parameter is used for giving time delay errors caused by factors such as different lengths of feeder lines of the base station and the like; the clock error compensation parameter is used for compensating the clock synchronization error of the base station; the OFDM ranging signal parameter, the time slot number where the OFDM ranging signal is located and the time period in the time slot; the air pressure height measurement correction parameter is used for correcting an air pressure height measurement error by the terminal; the synchronization and verification are used for frame synchronization and frame verification of the navigation message.
220. The ranging device determines the initial code phase and carrier frequency of the CDMA signal.
For example, the CDMA signal detection module 21 detects a CDMA pilot signal, achieves coarse synchronization of the system through time domain correlation, and provides an integrated initial code phase and carrier frequency for tracking a weak-energy CDMA navigation signal.
230. The ranging device obtains the transmission time delay of the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal.
For example, the CDMA signal detection module 21 obtains the transmission delay of the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal.
240. The distance measuring device tracks the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal to obtain the time and frequency synchronous information and demodulates the navigation message.
For example, the weak energy CDMA signal tracking module 22 integrates and tracks the weak energy CDMA navigation signal for a long time, obtains finer time and frequency synchronization information, and demodulates the navigation message.
Preferably, in the tracking process, multipath outside the chip can be reproduced and provided to the OFDM ranging signal detection unit, so as to improve the ranging capability of the OFDM ranging signal detection unit in a multipath environment.
250. The distance measuring device determines the time slot of the OFDM signal according to the navigation message, and performs time delay measurement on the time slot of the OFDM signal according to the time and frequency synchronization information to obtain the transmission time delay of the OFDM signal.
For example, the OFDM ranging signal detection module 24 determines the corresponding time in the slot number of the slot number machine in which the OFDM ranging signal is located according to the navigation message, and performs fine delay measurement on the OFDM ranging signal at the specified slot and frequency position based on the time and frequency synchronization information acquired by the CDMA navigation signal. In the measuring process, multipath interference can be relieved through multipath information obtained by a CDMA navigation signal tracking unit.
Optionally, when the ranging device analyzes the positioning signal to obtain the OFDM signal, the ranging device may analyze and obtain OFDM service information according to the time and frequency synchronization information.
For example, the OFDM symbol demodulation module 23 performs OFDM symbol demodulation based on the time and frequency synchronization information acquired by the CDMA navigation signal, and acquires OFDM service information.
Further, in this embodiment, the fine delay measurement information obtained by the OFDM ranging signal detection module 24 is fed back to the weak signal CDMA navigation signal tracking module, so as to improve the CDMA navigation signal ranging accuracy.
260. The distance measuring device measures the distance according to the CDMA signal and the OFDM signal.
Firstly, using CDMA pilot frequency in positioning signal (such as TC-OFDM signal) to make first path and external chip multipath capture, and using CDMA pilot frequency signal to make first path and external chip multipath signal tracking, reproducing first path and external chip multipath signal, making amplitude A of reproduced first path signal0Time delay tau0Carrier frequency omega0And phase theta0Amplitude of the pth path signal ApTime delay taup. In indoor positioning, the carrier frequencies of the respective paths are considered to be the same.
Will omega0And theta0Carrier mixing for TC-OFDM reception signals0And performing Fast Fourier Transform (FFT) on the OFDM ranging signal by combining the time slot position and the frequency segment of the OFDM ranging signal given in the navigation message to obtain a frequency domain signal as shown in the formula (1-1).
Wherein A is0Is the amplitude of the first path signal; diCode used to indicate the i-th subcarrier of the OFDM ranging signal, diPreferably 1 or-1; j represents an imaginary part; t is time of OFDM ranging coincidenceA length; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispIs the p-th path signal time delay.
According to the existing OFDM ranging method, the local signal sequence y is subjected tokK ∈ (0, N-1) is processed by N-point FFT to obtain the frequency domain code sequence Y on each subcarrieri. τ' can be calculated by the formulas (1-2) to (1-5).
Wherein Z isiIs an intermediate value obtained according to the definition of (1-2); xiIs a complex sequence XiConjugation of (1); y isiA frequency domain code sequence on each subcarrier; l is a frequency domain correlation interval, and the parameter is adjustable; n is the number of subcarriers. The final available pseudoranges are:
r＝c(τ′+τ0)
(1-6)
where c is the speed of light and τ' is the time delay calculated from (1-5).
According to the reproduction result of the multipath signal, the invention reduces the influence of the multipath signal in the formula (1-1) and calculates the multipath error correction term
Wherein q is the number of off-chip multipaths obtained by CDMA tracking. For received signalFrequency domain code sequence X obtained by FFTiCorrecting to rewrite (1-2) to
Zi＝Yi(Xi-Δi)*(1-8)
And Z obtained from the formula (1-8)iThe pseudo-range calculation is performed by substituting (1-3) to the equation (1-6). By the correction, the interference of multipath outside the chip to the OFDM ranging signal is eliminated by utilizing the characteristic of strong resolving power of multipath outside the chip of the CDMA signal, so that the advantage of small ranging error of the OFDM ranging in a short-delay multipath environment is utilized, and the comprehensive ranging capability in the multipath environment is improved.
The distance measuring method of the embodiment of the invention receives a positioning signal which is sent by upstream equipment and simultaneously bears a CDMA signal for positioning and an OFDM signal for positioning; analyzing the positioning signal to obtain a CDMA signal; analyzing the positioning signal to obtain an OFDM signal; and performing ranging according to the CDMA signal and the OFDM signal. Therefore, the CDMA signal and the OFDM signal are simultaneously applied to ranging by receiving the positioning signal which simultaneously bears the CDMA signal for positioning and the OFDM signal for positioning, so that the ranging error can be reduced, and the positioning precision is improved.
Example 3
As shown in fig. 5, the cdma and ofdma signal coupling ranging apparatus provided in this embodiment includes:
a receiving module 41, configured to receive a positioning signal sent by an upstream device, where the positioning signal simultaneously carries a CDMA signal for positioning and an OFDM signal for positioning, and the positioning signal is obtained by coupling the CDMA signal and the OFDM signal by the upstream device;
a first analyzing module 42, configured to analyze the positioning signal to obtain a CDMA signal;
a second analyzing module 43, configured to analyze the positioning signal to obtain an OFDM signal;
and a ranging module 44, configured to perform ranging according to the CDMA signal and the OFDM signal.
Optionally, the ranging module 44 is configured to perform multi-path capture outside the first path and the chip by using the CDMA signal, perform multi-path signal tracking outside the first path and the chip by using the CDMA signal, and reproduce multi-path signals outside the first path and the chip; calculating a multipath error correction term according to a multipath signal reproduction result; according to the multipath error correction term, correcting a frequency domain code sequence obtained by FFT of a received signal; pseudo-range calculation is performed based on the corrected received signal.
Optionally, the ranging module applies the following formula, calculates a multipath error correction term,
wherein q is the number of off-chip multipaths obtained by CDMA tracking, diRepresenting a code adopted by an ith subcarrier of the OFDM signal; j represents an imaginary part; t is the time length of the OFDM ranging coincidence; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispDelay time of the p path signal;
the ranging module 44 is configured to apply the following formula to modify a frequency domain code sequence obtained by performing FFT on a received signal according to the multipath error correction term,
Zi＝Yi(Xi-Δi)*；
wherein,is a complex sequence XiConjugation of (1); y isiIs a frequency domain code sequence on each subcarrier.
Optionally, the first parsing module 42 is specifically configured to determine an initial code phase and a carrier frequency of the CDMA signal; and obtaining the transmission delay of the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal.
Optionally, the first parsing module 42 is further configured to track the CDMA signal according to an initial code phase and a carrier frequency of the CDMA signal, obtain time and frequency synchronization information, and demodulate the navigation message.
Optionally, the second parsing module 43 is specifically configured to determine, according to the navigation message, a time slot where the OFDM signal is located; and carrying out time delay measurement on the time slot of the OFDM signal according to the time and frequency synchronization information to obtain the transmission time delay of the OFDM signal.
The distance measuring device of the embodiment of the invention can realize the method embodiment, the constituent modules of the device and the functions of each module are only briefly described, and please refer to the method embodiment for detailed description.
The distance measuring device of the embodiment of the invention receives a CDMA signal for positioning and a positioning signal of an OFDM signal for positioning which are simultaneously carried and sent by upstream equipment; analyzing the positioning signal to obtain a CDMA signal; analyzing the positioning signal to obtain an OFDM signal; and performing ranging according to the CDMA signal and the OFDM signal. Therefore, the CDMA signal and the OFDM signal are simultaneously applied to ranging by receiving the positioning signal which simultaneously bears the CDMA signal for positioning and the OFDM signal for positioning, so that the ranging error can be reduced, and the positioning precision is improved.
Example 4
As shown in fig. 6, an embodiment of the present invention provides a method for transmitting a positioning message, which may include:
610. and coupling the CDMA signal and the OFDM signal for positioning to generate a positioning signal simultaneously carrying the CDMA signal and the OFDM signal.
620. And transmitting the positioning signal to a positioning terminal so that the positioning signal realizes positioning.
The execution subject of this embodiment may be a positioning message transmission device, and the apparatus may include a plurality of modules or devices to implement the method described above.
In the method for transmitting the positioning message of the embodiment, the CDMA signal and the OFDM signal used for positioning are coupled to generate the positioning signal simultaneously carrying the CDMA signal and the OFDM signal; and transmitting the positioning signal to the positioning terminal so that the positioning signal realizes positioning. Therefore, the positioning signal carries the CDMA signal and the OFDM signal simultaneously, the signal quality can be improved, and the positioning terminal can use the CDMA signal and the OFDM signal for positioning, so that the positioning accuracy is improved.
In the embodiment of the invention, when a mechanism for positioning signals (such as TC-OFDM signals) is constructed, CDMA navigation signals are added on the premise of not influencing normal OFDM services, so that the same-frequency common-load of the CDMA and OFDM signals is realized, the CDMA navigation signals are used as a distance measurement main channel, the OFDM signals are used as an auxiliary channel, and the wireless distance measurement precision under the environment of multipath and the like is improved through the coupling of the CDMA and OFDM signals.
As shown in fig. 4a, the OFDM traffic channel is composed of three systems, i.e., a frame, a slot, a beacon and an OFDM symbol, where one frame is composed of multiple slots, and each slot includes a beacon and multiple OFDM symbols, where the beacon is used for system synchronization and base station identity identification, and the traffic information is carried by the OFDM symbols. In the design of TC-OFDM signals, correct receiving of OFDM symbols cannot be influenced, so that normal operation of existing services is guaranteed.
Optionally, the CDMA signal includes a CDMA pilot and a CDMA navigation signal carrying a navigation message, the OFDM signal includes an OFDM ranging signal and an OFDM symbol for carrying a communication service, the positioning signal includes a beacon part and a data carrying part, and the CDMA signal and the OFDM signal for positioning are coupled in the above 610, so that when the positioning signal is generated, the CDMA pilot and the OFDM ranging signal can be carried in the beacon part, and the OFDM symbol for carrying a communication service and the CDMA navigation signal can be carried in the data carrying part, so as to generate the positioning signal.
For example, the signal structure per slot of the positioning signal in the embodiment of the present invention is shown in fig. 4 b.
The positioning signal (e.g., TC-OFDM signal) is newly designed for the existing beacon portion without changing the frame structure of the existing traffic system. Because the OFDM signal and the CDMA signal have complementary characteristics in multipath channel ranging, the beacon part adopts CDMA pilot frequency to carry out system synchronization and also reserves a period of time to carry the OFDM ranging signal for coupling ranging with the CDMA, thereby improving the ranging accuracy in multipath environment. And the rest part of the OFDM symbol is superposed with the CDMA navigation signal with low energy, time and frequency measurement can be carried out through long-time integration, and a navigation message is carried. The CDMA navigation signal and the OFDM symbol carrying normal service are simultaneously carried at the same frequency, and the normal receiving of the OFDM symbol is not influenced by the control of signal energy.
The signals of the various parts of the positioning structure shown in fig. 4b play a role as follows:
CDMA pilot frequency: and occupying part of time in the beacon, and adopting a short pseudo code sequence for quick time synchronization of the time slot signal. Different base stations are distinguished by different spreading codes. The CDMA pilot frequency can select Gold codes with good self-correlation and cross-correlation characteristics, and the code length can be designed according to the available time length of the beacon and the system bandwidth.
OFDM ranging signal: the method is used for carrying out decimal part time delay fine measurement and carrier frequency estimation in an OFDM ranging mode. The OFDM ranging signal is modulated with a specific code sequence in the frequency domain by IFFT, and then transmitted in the time domain. Different base station signals are distinguished by different times, and each time slot can configure k base station signals according to the available time of the beacon, as shown in fig. 4 c. The OFDM ranging signal can be used for supplementing with a CDMA navigation signal, and the ranging precision of the system in a complex environment is improved. (for example, k is 3 can be selected)
Weak energy CDMA navigation signal: can be used for fine synchronization of system carrier waves; CDMA long-time integration and fine tracking ranging; navigation messages are carried. The partial signals are transmitted at the same frequency with the OFDM symbols by adopting low energy, the energy does not influence the normal demodulation of the OFDM symbols, but high integral gain can be obtained by carrying out long-time integration on the CDMA signals, and the CDMA tracking distance measurement and the navigation message broadcasting are realized. (e.g., the CDMA pilot signal may be selected to be weak 15dB from the OFDM signal).
OFDM symbol: the modulation mode of OFDM service symbols of the existing system is not changed, and the compatibility of a service receiving part of the system is ensured.
Further optionally, when the OFDM symbol for carrying the communication service and the CDMA navigation signal are carried in the data carrying part, the OFDM symbol for carrying the communication service and the CDMA navigation signal of the data carrying part may be carried in the data carrying part at the same time and at the same frequency.
For example, a part of signals of the weak-energy CDMA navigation signal are transmitted at the same frequency with the OFDM symbol, and the energy does not affect the normal demodulation of the OFDM symbol, but high integral gain can be obtained by long-time integration of the CDMA signal, so that CDMA tracking ranging and navigation message broadcasting are realized.
Optionally, before the carrying the OFDM symbol for carrying the communication service and the CDMA navigation signal on the data carrying part, the method further includes:
and adjusting the strength of the CDMA navigation signal according to the signal strength of the OFDM symbol for bearing the communication service.
In the embodiment of the invention, the navigation message is carried by the weak energy CDMA navigation signal, and in order to ensure enough spread spectrum gain, 1bit message information can be carried by 1 or more time slots according to the time slot lengths of different OFDM service systems. Each frame of navigation message information comprises complete information necessary for navigation, and the navigation message frame and the OFDM service frame keep an integral multiple relation in time length in consideration of system consistency. Optionally, in the embodiment of the present invention, the navigation message includes at least one of the following:
the method comprises the following steps of base station number, base station coordinates, fixed time delay correction parameters, clock error compensation parameters, OFDM ranging signal parameters, barometric altimetry correction parameters, synchronization information and verification information.
Wherein, the base station number is used for identifying the identity of the base station; the base station coordinates are used for representing the position of a central phase point of a transmitting antenna of the base station; the fixed time delay correction parameter is used for giving time delay errors caused by factors such as different lengths of feeder lines of the base station and the like; the clock error compensation parameter is used for compensating the clock synchronization error of the base station; the OFDM ranging signal parameter, the time slot number where the OFDM ranging signal is located and the time period in the time slot; the air pressure height measurement correction parameter is used for correcting an air pressure height measurement error by the terminal; the synchronization and verification are used for frame synchronization and frame verification of the navigation message.
In the method for transmitting the positioning message of the embodiment, the CDMA signal and the OFDM signal used for positioning are coupled to generate the positioning signal simultaneously carrying the CDMA signal and the OFDM signal; and transmitting the positioning signal to the positioning terminal so that the positioning signal realizes positioning. Therefore, the positioning signal carries the CDMA signal and the OFDM signal simultaneously, the signal quality can be improved, and the positioning terminal can use the CDMA signal and the OFDM signal for positioning, so that the positioning accuracy is improved.
Example 5
As shown in fig. 7, a positioning message transmission device according to an embodiment of the present invention includes:
a generating module 71, configured to couple a CDMA signal and an OFDM signal for positioning, and generate a positioning message that simultaneously carries the CDMA signal and the OFDM signal;
and a transmission module 72, configured to transmit the positioning message to the positioning terminal, so that the positioning message realizes positioning.
Optionally, the CDMA signal includes a CDMA pilot and a CDMA navigation signal carrying a navigation message, the OFDM signal includes an OFDM symbol and an OFDM ranging signal for carrying a communication service, and the generating module 72 is specifically configured to carry the CDMA pilot and the OFDM ranging signal in the beacon portion, and carry the OFDM symbol and the CDMA navigation signal for carrying the communication service in the data carrying portion, so as to generate the positioning message.
Optionally, the generating module 71 is specifically configured to use the data carrying part for carrying the OFDM symbol of the communication service and the CDMA navigation signal simultaneously and co-frequency carried in the data carrying part.
Optionally, the generating module 71 is specifically configured to adjust the strength of the CDMA navigation signal according to the signal strength of the OFDM symbol used for carrying the communication service.
The positioning message transmission device of the embodiment of the present invention can implement the above method embodiment, and the constituent modules of the device and the functions of each module are only briefly described, and please refer to the above method embodiment for detailed description.
The positioning message transmission device of the embodiment generates a positioning signal simultaneously carrying a CDMA signal and an OFDM signal by coupling the CDMA signal and the OFDM signal for positioning; and transmitting the positioning signal to the positioning terminal so that the positioning signal realizes positioning. Therefore, the positioning signal carries the CDMA signal and the OFDM signal simultaneously, the signal quality can be improved, and the positioning terminal can use the CDMA signal and the OFDM signal for positioning, so that the positioning accuracy is improved.
Example 6
As shown in fig. 8, the present embodiment provides a cdma and ofdma signal coupling ranging system, which includes an upstream device 81 and a ranging apparatus 82, wherein:
the upstream device 81 is configured to couple the CDMA signal for positioning and the OFDM signal for positioning, and generate a positioning signal that simultaneously carries the CDMA signal and the OFDM signal; transmitting a positioning signal to a ranging device; the upstream device may perform the method of embodiment 4. That is, the upstream device may refer to the positioning message transmitting device shown in embodiment 5.
The distance measuring device 82 is the distance measuring device of embodiment 3 described above.
The distance measuring system of the embodiment of the invention receives a positioning signal which is sent by an upstream device and simultaneously bears a CDMA signal for positioning and an OFDM signal for positioning; analyzing the positioning signal to obtain a CDMA signal; analyzing the positioning signal to obtain an OFDM signal; and performing ranging according to the CDMA signal and the OFDM signal. Therefore, the CDMA signal and the OFDM signal are simultaneously applied to ranging by receiving the positioning signal which simultaneously bears the CDMA signal for positioning and the OFDM signal for positioning, so that the ranging error can be reduced, and the positioning precision is improved.
In the embodiment of the present invention, the influence of multipath on the CDMA signal and the OFDM signal is shown in fig. 9, for the CDMA signal, the smaller the correlator spacing d is, the smaller the error generated by multipath is, and when the multipath delay is greater than (1+ d) chips, the CDMA code phase measurement error caused by multipath is 0. However, when the correlator spacing d is too small, the phase operating points of the early and late correlators will be near the top of the main peak of the autocorrelation function. In practical situations, due to bandwidth limitation, the curve of the correlation function is not an ideal triangle and is smoother near the top of the main peak of the function, so that the sensitivity and dynamics of the code loop are reduced due to too small a correlator spacing. For OFDM signals, the ranging error fluctuates periodically with multipath delay. When the multipath delay is small, the CDMA ranging is affected by the multipath more seriously, and when the multipath delay is large, the CDMA ranging is not affected by the multipath any more, but the multipath interference in the OFDM ranging still exists.
The distance measurement method, the device and the system of the embodiment of the invention fully utilize the complementary distance measurement characteristics of CDMA and OFDM signals under a multipath channel, and reduce the distance measurement error caused by multipath in the urban complex environment. Meanwhile, the TC-OFDM signal system provided by the technology can realize high-precision ranging navigation under the condition of not influencing OFDM services.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program instructing relevant hardware, where the program may be stored in a computer-readable storage medium, and the above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts of the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the apparatus embodiment, since it is substantially similar to the method embodiment, it is relatively simple to describe, and reference may be made to some descriptions of the method embodiment for relevant points. The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software plus necessary general hardware, including general-purpose integrated circuits, general-purpose CPUs, general-purpose memories, general-purpose components, etc., or by special hardware including dedicated integrated circuits, dedicated CPUs, dedicated memories, dedicated components, etc., but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention may be substantially implemented or a part of the technical solutions contributing to the prior art may be embodied in the form of a software product, which is stored in a readable storage medium, such as a floppy disk, a hard disk, or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the method of the embodiments of the present invention.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent replacements, improvements, etc. within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for measuring distance by coupling code division multiple access and orthogonal frequency division multiple access signals is characterized by comprising the following steps:
receiving a positioning signal sent by upstream equipment, wherein the positioning signal simultaneously carries a Code Division Multiple Access (CDMA) signal for positioning and an orthogonal frequency division multiple access (OFDM) signal for positioning, and the upstream equipment couples the CDMA signal and the OFDM signal to obtain the positioning signal;
analyzing the positioning signal to obtain the CDMA signal;
analyzing the positioning signal to obtain the OFDM signal;
performing ranging according to the CDMA signal and the OFDM signal;
performing ranging according to the CDMA signal and the OFDM signal includes:
the CDMA signal is used for capturing the first path and the multipath outside the chip, and the CDMA signal is used for tracking the first path and the multipath outside the chip to reproduce the first path and the multipath outside the chip;
calculating a multipath error correction term according to a multipath signal reproduction result;
according to the multipath error correction term, correcting a frequency domain code sequence obtained by FFT of a received signal;
performing pseudo-range calculation based on the corrected received signal;
calculating a multipath error correction term according to a multipath signal reproduction result includes: according to the multipath signal reproduction result, the following formula is applied to calculate the multipath error correction term,
wherein q is the number of off-chip multipaths obtained by CDMA tracking, diRepresenting a code adopted by an ith subcarrier of the OFDM signal; j represents an imaginary part; t is the time length of the OFDM ranging coincidence; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispDelay time of the p path signal;
according to the multipath error correction term, correcting the frequency domain code sequence obtained by FFT of the received signal comprises the following steps: according to the multipath error correction term, the frequency domain code sequence obtained by FFT of the received signal is corrected by applying the following formula,
Zi＝Yi(Xi-Δi)*；
wherein,is a complex sequence XiConjugation of (1); y isiIs a frequency domain code sequence on each subcarrier.
2. The method of claim 1, wherein said resolving the positioning signal to obtain the CDMA signal comprises:
determining an initial code phase and a carrier frequency of the CDMA signal;
and obtaining the transmission delay of the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal.
3. The method of claim 1, wherein after obtaining the CDMA signal transmission delay according to the initial code phase and carrier frequency of the CDMA signal, further comprising:
and tracking the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal to obtain time and frequency synchronization information, and demodulating a navigation message.
4. The method of claim 3, wherein parsing the positioning signal to obtain the OFDM signal comprises:
determining the time slot of the OFDM signal according to the navigation message;
and performing time delay measurement on the time slot of the OFDM signal according to the time and frequency synchronization information to obtain the transmission time delay of the OFDM signal.
5. A cdma and ofdma signal coupling ranging apparatus, comprising:
a receiving module, configured to receive a positioning signal sent by an upstream device, where the positioning signal simultaneously carries a CDMA signal for positioning and an OFDM signal for positioning, and the positioning signal is obtained by coupling the CDMA signal and the OFDM signal with the upstream device;
the first analysis module is used for analyzing the positioning signal to obtain the CDMA signal;
the second analysis module is used for analyzing the positioning signal to obtain the OFDM signal;
the ranging module is used for ranging according to the CDMA signal and the OFDM signal;
the distance measurement module is used for capturing the first path and the multipath outside the chip by using the CDMA signal, tracking the first path and the multipath outside the chip by using the CDMA signal and reproducing the first path and the multipath outside the chip; calculating a multipath error correction term according to a multipath signal reproduction result; according to the multipath error correction term, correcting a frequency domain code sequence obtained by FFT of a received signal; performing pseudo-range calculation based on the corrected received signal;
the ranging module applies the following formula to calculate a multipath error correction term,
wherein q is the number of off-chip multipaths obtained by CDMA tracking, diRepresenting a code adopted by an ith subcarrier of the OFDM signal; j represents an imaginary part; t is the time length of the OFDM ranging coincidence; tau'0Is the difference between the actual time delay of the first path signal and τ 0, ApIs the amplitude of the p-th path signal; tau ispDelay time of the p path signal;
the ranging module is used for correcting the frequency domain code sequence obtained by FFT of the received signal according to the multipath error correction term by applying the following formula,
Zi＝Yi(Xi-Δi)*；
wherein,is a complex sequence XiConjugation of (1); y isiIs a frequency domain code sequence on each subcarrier.
6. The apparatus of claim 5, wherein the first parsing module is specifically configured to determine an initial code phase and a carrier frequency of the CDMA signal; and obtaining the transmission delay of the CDMA signal according to the initial code phase and the carrier frequency of the CDMA signal.
7. The apparatus of claim 5, wherein the first parsing module is further configured to track the CDMA signal according to an initial code phase and a carrier frequency of the CDMA signal, obtain time and frequency synchronization information, and demodulate a navigation message.
8. The apparatus according to claim 7, wherein the second parsing module is specifically configured to determine a time slot in which the OFDM signal is located according to the navigation message; and performing time delay measurement on the time slot of the OFDM signal according to the time and frequency synchronization information to obtain the transmission time delay of the OFDM signal.
9. A code division multiple access and orthogonal frequency division multiple access signal coupling ranging system is characterized by comprising upstream equipment and a ranging device, wherein:
the upstream device is used for coupling a CDMA signal for positioning and an OFDM signal for positioning to generate a positioning signal for simultaneously carrying the CDMA signal and the OFDM signal; transmitting the positioning signal to the ranging device;
the distance measuring device as claimed in any one of the preceding claims 5-8.
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Application publication date: 20140319 Assignee: Beijing Duwei Technology Co.,Ltd. Assignor: Beijing University of Posts and Telecommunications Contract record no.: X2022980005266 Denomination of invention: Code division multiple access and orthogonal frequency division multiple access signal coupling ranging method, device and system Granted publication date: 20170222 License type: Common License Record date: 20220507 |
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