CN118301738A - Ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard - Google Patents
Ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard Download PDFInfo
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Abstract
The invention relates to the field of ultra-wideband data synchronization and communication positioning, in particular to an ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard. The system comprises 1 central node, a plurality of anchor nodes and at least 1 target node, wherein the anchor nodes receive IR-UWB signals sent by the target nodes, and the communication information is demodulated through the arrival time difference of each pulse signal; the anchor node transmits the communication information to the central node, and the central node performs position calculation by combining TOA values of a plurality of anchor nodes to finish the process of one-time communication and positioning; the target node transmits a fixed-length '0' bit string to help signal capture and timing adjustment, and transmits a specific data string as a synchronization mark, and after the anchor node demodulates the synchronization mark, the capture is completed, and data reception is started. The invention can ensure the mutual coordination working degree with other systems; the pulse synchronization callback can be realized under the condition that the clocks of the receiving and transmitting ends are asynchronous, and the system communication and the target positioning are realized simultaneously through a low-complexity algorithm.
Description
Technical Field
The invention relates to the field of ultra-wideband data synchronization and communication positioning, in particular to an ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard.
Background
Since pulsed ultra wideband (IR-UWB) signals primarily employ nanosecond pulses to convey information, both the correct data demodulation and target position estimation rely on accurate signal time of arrival (TOA) estimates. Therefore, for the communication and sensing positioning system, the UWB signal transceiver has similar radio frequency spectrum, hardware front end and signal processing algorithm, so that the IR-UWB technology has strong feasibility for realizing the communication positioning integrated system, and further the characteristics of high spectrum efficiency, strong instantaneity, hardware integration and the like are realized.
Currently, a plurality of wireless communication standards exist to adapt to different wireless communication requirements, the ultra wideband IEEE802.15.4z protocol is a 2020 latest edition of UWB positioning technology standard, and the IEEE802.15.4z standard defines a mode and a protocol for mutual communication between devices in a personal area network through a radio frequency mode, and a protocol model is divided into two sublayers, namely a physical layer (PHY) and a medium access control layer (MAC) to be implemented. One of the frame structures of the ieee802.15.4z physical layer is divided into the following parts:
| SYNC | SFD | STS | PHR | PHR Payload |
SYNC is a frame synchronization header for performing pulse synchronization; SFD is frame separator to define the start bit of data sync frame; STS is a section of encryption sequence used for enhancing the security of the system and increasing the integrity of the frame structure; PHR defines the data length, speed and other load related information of a frame; PHR Payload is valid data transmitted by the physical layer.
In order to meet the wireless communication requirements in different application fields, partial scholars propose own protocol schemes, and meanwhile, the compatibility of autonomous design protocol schemes and international standard protocols is particularly important in order to improve the degree of mutual coordination work among systems.
Disclosure of Invention
The invention provides an ultra-wideband communication positioning integrated method compatible with IEEE802.15.4z standard, which aims to realize the frame structure design of an ultra-wideband wireless communication system and the data communication and target positioning functions under an ad hoc network architecture and provides technical reference for designing an IR-UWB communication positioning integrated system compatible with IEEE802.15.4z standard protocol.
The invention provides an ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard, which comprises 1 central node, a plurality of anchor nodes and at least 1 target node, wherein the anchor nodes receive IR-UWB signals sent by the target nodes, demodulate communication information through the arrival time difference of each pulse signal, and synchronize clocks of the anchor nodes and asynchronous clocks of the target nodes; the anchor node transmits the communication information to the central node, and the central node performs position calculation by combining TOA values of a plurality of anchor nodes to finish the process of one-time communication and positioning;
In the communication process, on the basis of a communication frame structure, a target node firstly transmits a 0 bit string with a fixed length for helping signal capture and timing adjustment, then transmits a specific data string as a synchronous mark, and when the anchor node demodulates the synchronous mark, the capture is considered to be completed and data reception is started.
As a further improvement of the invention, in the process of communication and positioning, the central node positions the target node through multi-anchor joint solution; the target node completes the information transmission to the anchor node at the same time.
As a further improvement of the invention, the transmitting signal of the target node uses a TH ultra wideband signal, the communication data is modulated by adopting a PPM modulation mode, and the TH-PPM UWB signal of the j-TH transmitting period is expressed as:
Where T f is the pulse repetition period, N f is the total number of pulses of the received signal, T is the clock time of the transmitter, To have a periodic pseudo-random time hopping code, for the kth target,T is an integer, N p is the period of the pseudo-random code, for a given value N h, atThe code element in the range is an integer, and the larger N h is, the lower the correlation between sequences is, and T c is the unit time-hopping width; delta is PPM modulated time shift, the data sequence { p j } transmitted by the transmitter is binary bit stream carrying some information, if the data symbol is 1, the single-period pulse will increase delta pulse time shift; if the data symbol is 0, there is no additional modulation time shift, w (t) is the energy normalized pulse shape,T b is the duration of the pulse,For the energy of the transmitted pulse, P t is the signal transmit power; if the pulse protection interval is gamma, the setting relation of each parameter should satisfy:
NhTc+δ+γ＜Tf
the signal received by the ith anchor node after passing through the channel can be expressed as:
sr(t)＝Aig(t-Δτ-tdi)+z(t)
Where Δτ represents an initial clock offset between the signal receiver and the transmitter, a i represents an amplitude attenuation of a signal transmitted by the target transmitter reaching the ith receiver after propagating through the path, g (t) =s (t) ×h (t) is a response function of a single pulse of normalized energy after passing through the multipath channel, t di represents a transmission delay between the transmitter and the ith receiver, and noise z (t) at the receiving end is additive white gaussian noise.
As a further development of the invention, the communication frame structure comprises a pilot sequence equivalent to a frame synchronization header in the IEEE 802.15.4z protocol, a specific synchronization header equivalent to a frame delimiter SFD in the IEEE 802.15.4z protocol, DATA equivalent to a PHR Payload in the IEEE 802.15.4z protocol.
As a further improvement of the present invention, a quasi-static time Tstatic is formulated, the quasi-static time Tstatic covers the pilot sequence, the specific synchronization header, the DATA, the timing error generated in Tstatic will not affect the DATA reception, and the acquisition synchronization and timing adjustment are performed again after the transmission time exceeds Tstatic
As a further improvement of the invention, the pilot frequency sequence adopts a TOA estimation method based on matched filtering to carry out pulse synchronization, and the anchor node receiving end adopts a CFAR algorithm to carry out pulse signal identification.
As a further improvement of the invention, the pilot frequency sequence adopts a TOA estimation method based on matched filtering to carry out pulse synchronization, and adopts a CFAR algorithm to carry out pulse signal identification at the receiving end of the anchor node, and the specific process comprises the following steps:
The discretized receiving signal and the environment noise in one frame interval are respectively set as r (n) and z (n), the local module signal is discretized into omega (n), and when one pulse exists in one frame time of the receiving end, the discretized receiving signal of the current frame is as follows:
r(n)＝Aw(n-τ(n))*h(n)+z(n)
Wherein A represents amplitude attenuation of a signal transmitted by a transmitter reaching a receiver after being propagated through a path, τ (n) represents a discretized numerical value of total transmission delay of the signal in one period, h (n) is a discretized multipath channel, and w (n) represents a discretized transmitted signal;
the decision variables of the matched filtering are:
Where N s is the number of signal samples in a frame interval, then the expected sum variance of r MF is:
Wherein the method comprises the steps of Is the variance of the noise;
Establishing a hypothesis testing model through parameters of a matched filtering decision variable r MF:
Wherein H 0 represents that only noise exists in one frame time of the receiving end, H 1 represents that a signal exists in one frame time, and:
the false alarm probability of the signal in the time period before the Anchor receives the pilot is expressed as:
The threshold value gamma for acquisition pilot is therefore:
Wherein, The threshold gamma is determined by limiting the false alarm probability P FA for the variance of the noise, the decision variable obtained by the matched filtering of the receiving end is compared with the threshold value, if the threshold value is exceeded, a pilot pulse is considered to be captured, otherwise, the current frame is noise.
As a further improvement of the present invention, after pulse synchronization is completed, a reception mode of correlation detection is adopted to perform data reception, and a received j frame signal of the i link and a local module signal are subjected to correlation operation:
The peak value of the cross-correlation function is the position of the captured pulse signal I.e., the time of arrival of the signal is estimated using the received data of a pulse in the received signal.
As a further improvement of the present invention, the integrated communication and positioning resolving process includes:
Let the position coordinates of the target node be p= [ p x,py,pz]T, the positions of i anchor nodes are known, and expressed as r= [ x i,yi,zi]T, the propagation time of the signal from the target to the receiving point is:
Assuming that the time of a first pulse signal transmitted by a target is zero, the clock deviation of a receiving end and a transmitting end is delta tau, the modulation time of the j-th frame data is T j, and the pulse repetition interval is T f;
the arrival time estimate of the jth frame data of the ith link is:
The modulation time t j of each frame signal includes two parts of time hopping code modulation c jTc and pulse position modulation δa j;
the signal measurement and data demodulation process of the single anchor node is as follows:
Considering only the operation of the first receiver, when j 0 modulation data symbols are 0 and j 1 and j 2 modulation data symbols are 1, the operation of the first receiver is obtained by a correlation algorithm The values are respectivelyAndThe method can obtain:
Wherein the method comprises the steps of AndFor the arrival times of the j 0、j1 th and j 2 th pulse signals respectively,AndThe corresponding pseudo-random time hopping codes are modulated for each pulse data respectively, and the difference value of toa 0 and toa 1 is the length delta of PPM modulation under ideal conditions, and toa 1 and toa 2 are equal; in the actual calculation process, setting a pulse position demodulation threshold value as delta/2, when toa 1-toa0 is more than delta/2, considering modulation data symbols of j 0 and j 1 pulses as 0 and 1 respectively, and when |toa 2-toa1 | < delta/2, considering modulation symbols of toa 2 and toa 1 as the same as each other as 1, namely finishing demodulation of information; meanwhile, toa 0、toa1 -delta and toa 2 -delta are estimated values of delta tau+t d1, and delta tau+t di of the jth pulse of the ith anchor point is recorded as tes ij;
the plurality of anchor nodes diversity demodulate data and realize the positioning process as follows:
Adopting a space diversity method, utilizing data demodulated by multiple anchor points to jointly calculate the error rate of a communication system, and for the same signal pulse, when the data demodulated by multiple anchor nodes are different, selecting the data according to the number of the anchor nodes with the same demodulation data;
from the estimate of Δτ+t d1, we can get:
wherein c represents the propagation velocity of electromagnetic waves in the air, the anchor node position r is known, and the target node estimated position Unknown, by equationSolving for clock bias Deltaτ and estimated position of target
The beneficial effects of the invention are as follows: the IR-UWB signal frame structure designed by the invention has compatibility with the IEEE 802.15.4z in protocol, and can ensure the mutual coordination working degree with other systems; the pulse synchronization callback can be realized under the condition that the clocks of the receiving and transmitting ends are asynchronous, system communication and target positioning are realized simultaneously through a low-complexity algorithm, the utilization rate of spectrum resources is improved, and theoretical reference is provided for hardware integrated design.
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FIG. 1 is a schematic diagram of a networking architecture of the present invention;
FIG. 2 is a schematic illustration of TH-PPM signal modulation in accordance with the present invention;
FIG. 3 is a communication frame structure diagram of the present invention;
fig. 4 is a schematic diagram of the propagation delay of a single link signal of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent.
The invention provides an ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard, which can be applied to an indoor and outdoor communication positioning integrated system, and particularly relates to an IR-UWB clock synchronization system frame structure design compatible with IEEE 802.15.4z, a communication signal modulation and demodulation mode, a receiving end signal measurement mode and an ad hoc network architecture capable of realizing communication positioning integration.
The communication positioning integrated system based on the IR-UWB signal provided by the invention mainly has three innovation points: firstly, an ultra-wideband signal frame structure which is compatible with an IEEE802.15.4z standard protocol and can realize pulse synchronization and data transmission is designed; secondly, a proper UWB signal modulation mode and a proper UWB signal measurement method are selected, so that a receiving end can obtain communication data and signal arrival time at the same time; thirdly, the networking scheme with reasonable design enables the system to realize accurate target positioning.
The basic idea and main operation of the present invention are specifically described below.
(Networking structure):
The networking structure of the invention is like the networking of figure 1, the position of the target under the three-dimensional Cartesian coordinate system is estimated according to the transmitting signal of the target, the clock of the receiving end is synchronous, and the clock of the receiving end and the node clock of the target are asynchronous. Without loss of generality, the network comprises 1 central node (for resolving, not participating in positioning in the communication), 4 anchor nodes and 1 target node (which may be added later). The anchor node receives the IR-UWB signals sent by the target node, demodulates communication information through the arrival time difference of each pulse signal, then transmits the information to the center node, and the center node performs position calculation by combining TOA values of a plurality of anchor nodes to finish the process of one-time communication and positioning.
In the process, the central node can realize the positioning of the target node through multi-anchor joint calculation; the target node completes the information transmission to the anchor node at the same time.
Therefore, under the self-networking platform, the method can realize simultaneous target positioning and communication.
(Signal model and modulation):
In view of the scalability of the system, the present invention uses time-hopping (TH) ultra-wideband signals as the target transmit signals to implement multiple access techniques, with the TH sequence employing a pseudo-random sequence. The communication data adopts a PPM modulation mode to carry out signal modulation, and for a transmitter, a TH-PPM UWB signal of a j-TH transmission period can be expressed as:
Where T f is the pulse repetition period, N f is the total number of pulses of the received signal, T is the clock time of the transmitter, To have a periodic pseudo-random time hopping code, for the kth target,T is an integer, N p is the period of the pseudo-random code, for a given value N h, atThe value of the code element in the range is an integer, and the larger N h is, the lower the correlation between the sequences is, and T c is the unit time-hopping width. Delta is PPM modulated time shift, the data sequence { p j } transmitted by the transmitter is a binary (0 or 1) bit stream carrying some information, if the data symbol is 1, the single period pulse will increase delta pulse time shift; if the data symbol is 0, there is no additional modulation time shift, w (t) is the energy normalized pulse shape,T b is the duration of the pulse,For the energy of the transmit pulse, P t is the signal transmit power. The invention transmits the pulse as the monopulse, namely the pulse repetition number is 1, set the pulse guard interval as gamma, then the setting relation of each parameter should satisfy:
NhTc+δ+γ＜Tf (2)
Taking the upper limit value of time hopping code N h =4 as an example, fig. 2 shows a schematic diagram of signal modulation of two target users when the signal transmission data stream is 010, and the time hopping sequences thereof are {4,2,3} and {2,3,4}, respectively.
The signal received by the ith anchor point after the channel can be expressed as:
sr(t)＝Aig(t-Δτ-tdi)+z(t) (3)
Where Δτ represents an initial clock offset between the signal receiver and the transmitter, a i represents an amplitude attenuation (related to a distance and an attenuation factor) of a signal transmitted by the transmitter reaching the ith receiver after propagating through a path, g (t) =s (t) ×h (t) is a response function of a single pulse of normalized energy after passing through a multipath channel, t di represents a signal transmission delay between the transmitter and the ith receiver, noise z (t) at a receiving end is additive white gaussian noise, s (t) is a transmitted signal, as shown in formula (1), and h (t) is a multipath channel.
(Signal frame structure):
In a communication system, a certain protocol must be achieved between transceivers to communicate. Based on the communication frame structure shown in fig. 3, a data-assisted synchronization means is employed. The transmitter first transmits a fixed length '0' bit string to aid in signal acquisition and timing adjustment. Then a specific data string is sent as a synchronous mark, and when the mark is demodulated by a receiving end, the capturing is considered to be completed, and the data receiving can be started.
Because of some insignificant interference factors in the environment, such as drift of the crystal clock of the transceiver, narrowband interference in the environment, etc., a quasi-static time Tstatic is formulated according to the frame structure shown in fig. 3, the timing error considered to be generated in Tstatic will not affect the data reception, and when the transmission time exceeds Tstatic, the acquisition synchronization and timing adjustment need to be performed again. This approach, while sacrificing some system efficiency, is easy to implement.
The pilot sequence of the frame structure of the invention has the same effect as the frame synchronization header in the IEEE 802.15.4z protocol; EB90 specific synchronization header has the same effect as frame delimiter SFD in IEEE 802.15.4z protocol; the DATA is effective DATA transmitted by the physical layer, and is equivalent to PHR Payload in the IEEE 802.15.4z protocol. As for STS and PHR in standard protocol can be added according to specific scene, it does not affect system to realize communication and positioning, but affects system communication rate and positioning accuracy.
For the pilot frequency part, the pulse synchronization is carried out by adopting a TOA estimation method based on matched filtering, and the pulse signal identification is carried out by adopting a CFAR (Constant FALSE ALARM detection) algorithm at a system receiving end.
The discretized receiving signal and the environmental noise in one frame interval are respectively set as r (n) and z (n), the local module signal is discretized into ω (n), and when one pulse exists in one frame time of the receiving end, the discretized receiving signal of the current frame is (for simplifying the representation, corner marks are omitted):
r(n)＝Aw(n-τ(n))*h(n)+z(n) (4)
Wherein A represents amplitude attenuation of a signal transmitted by a transmitter reaching a receiver after being propagated through a path, τ (n) represents a discretized numerical value of total transmission delay of the signal in one period, h (n) is a discretized multipath channel, and w (n) represents a discretized transmitted signal;
the decision variables of the matched filtering are:
Where N s is the number of signal samples in a frame interval, then the expected sum variance of r MF is:
Wherein the method comprises the steps of Is the variance of the noise.
Establishing a hypothesis testing model through parameters of a matched filtering decision variable r MF:
Where H 0 denotes that only noise exists in one frame time at the receiving end (r MF obeys gaussian distribution, μ 0, Representing the corresponding expected and variance, respectively), H 1 represents the presence of a signal (r MF obeys gaussian distribution, μ 1,Representing the corresponding expectations and variances, respectively), and:
the false alarm probability of the signal in the time period before the Anchor receives the pilot is expressed as:
The threshold value gamma for acquisition pilot is therefore:
Wherein, The threshold gamma is determined by limiting the false alarm probability P FA for the variance of the noise, the decision variable obtained by the matched filtering of the receiving end is compared with the threshold value, if the threshold value is exceeded, a pilot pulse is considered to be captured, otherwise, the current frame is noise.
(Correlation detection):
After the system completes pulse synchronization, the data is received by adopting a receiving mode of correlation detection, and the received j frame signal of the ith link is subjected to correlation operation with a local module signal:
The peak value of the cross-correlation function is the position of the captured pulse signal I.e. the arrival time of the signal. The signal arrival time may be estimated directly using a pulse in the received signal to receive data.
(Communication positioning integration algorithm):
Let the position coordinates of the target node be p= [ p x,py,pz]T, the positions of the four anchor nodes are known, and expressed as r= [ x i,yi,zi]T, i=1, 2,3,4. The propagation time of the signal from the target to the receiving point is then:
fig. 4 shows a schematic diagram of signal propagation delay of a single link, where it is assumed that the time of the first pulse signal transmitted by the target is zero, the clock deviation between the receiving end and the transmitting end is Δτ, the modulation time of the jth frame of data is T j, and the pulse repetition interval is T f.
If the time of receiving each frame signal by the four link receiving ends is respectively denoted as t s1j,ts2j,ts3j,ts4j, the arrival time of the jth frame data of the ith link is estimated as follows:
four anchor points are arranged in the unidirectional ranging model, so that an equation set can be obtained according to the above formula:
The modulation time t j of each frame signal comprises two parts of time hopping code modulation c jTc and pulse position modulation δa j, wherein the TH modulation length of each frame signal is known as a priori knowledge, and the arrival time of the left value signal of the equation set The bit stream data symbols and other parameters of the system of equations are unknown. The solution process of the equation set is as follows:
Signal measurement and data demodulation of a single anchor node are realized:
Considering the operation of the first receiver, when j 0 modulation data symbols are 0 and j 1 and j 2 modulation data symbols are 1, the operation of the first receiver is obtained by a correlation algorithm The values are respectivelyAndFrom a first equation in equation set (14) is available:
Wherein the method comprises the steps of AndFor the arrival times of the j 0、j1 th and j 2 th pulse signals respectively,AndThe pseudo-random time hopping codes corresponding to the pulse data modulation are respectively calculated, the parameters are known through calculation, the numerical values of toa 0、toa1 and toa 2 can be calculated according to the parameters, and the difference value of toa 0 and toa 1 is the length delta of PPM modulation under ideal conditions, toa 1 and toa 2 are equal. In the actual calculation process, since the signal arrival time is an estimated value and a certain error exists between the signal arrival time and a true value, the pulse position demodulation threshold value is set to delta/2, when toa 1-toa0 is more than delta/2, the modulation data symbols of the j 0 th pulse and the j 1 th pulse are respectively considered to be 0 and 1, When the absolute value of the toa 2-toa1 is less than delta/2, the modulation symbols of the toa 2 and the toa 1 are the same and are 1, namely the demodulation of the information is completed. Meanwhile, toa 0、toa1 -delta and toa 2 -delta are estimated values of delta tau+t d1, and delta tau+t di of the jth pulse of the ith anchor point is recorded as tes ij for convenience of explanation.
The plurality of anchor nodes diversity demodulates the data and achieves positioning:
In addition, the invention adopts a space diversity method, utilizes the data combination of multi-anchor demodulation to calculate the error rate of a communication system, and carries out data selection according to the number of anchor nodes with the same demodulation data when the data demodulated by four anchor nodes are different for the same signal pulse, for example, three anchor node demodulation data are 1, one anchor node demodulation data are 0, the current pulse carrying data are considered to be 1, and if two anchor node demodulation data are respectively 0 and 1, the current pulse carrying data are randomly selected.
The estimate of Δτ+t d1 from equation (15) can be combined with equation set (14):
wherein c represents the propagation velocity of electromagnetic waves in the air, the anchor node position r is known, and the target node estimated position Unknown. The clock deviation delta tau and the estimated position of the target can be calculated by the equation set (16)
The ultra-wideband communication positioning integrated method compatible with the IEEE 802.15.4z standard has the following advantages:
1) The IR-UWB signal frame structure designed by the invention has compatibility with the IEEE 802.15.4 in the protocol, and can ensure the mutual coordination working degree with other systems;
2) The pulse synchronization callback can be realized under the condition that the clocks of the receiving and transmitting ends are asynchronous, system communication and target positioning are realized simultaneously through a low-complexity algorithm, the utilization rate of spectrum resources is improved, and theoretical reference is provided for hardware integrated design.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (9)
1. An ultra-wideband communication positioning integrated method compatible with IEEE 802.15.4z standard is characterized by comprising 1 central node, a plurality of anchor nodes and at least 1 target node, wherein the anchor nodes receive IR-UWB signals sent by the target nodes, the communication information is demodulated through the arrival time difference of each pulse signal, the clocks of the anchor nodes are synchronous, and the clocks of the anchor nodes and the target nodes are asynchronous; the anchor node transmits the communication information to the central node, and the central node performs position calculation by combining TOA values of a plurality of anchor nodes to finish the process of one-time communication and positioning;
in the communication process, on the basis of a communication frame structure, a target node firstly transmits a 0 bit string with a fixed length for helping signal capture and timing adjustment, then transmits a specific data string as a synchronous mark, and when the anchor node demodulates the synchronous mark, the capture is completed and data reception is started.
2. The ultra-wideband communication positioning integrated method compatible with the IEEE 802.15.4z standard according to claim 1, wherein the center node performs positioning on the target node through multi-anchor joint solution in the communication and positioning process; the target node completes the information transmission to the anchor node at the same time.
3. The method for integrating ultra-wideband communication and positioning compatible with IEEE 802.15.4z standard as claimed in claim 1, wherein the transmitting signal of the target node uses TH ultra-wideband signal, the communication data is modulated by PPM modulation mode, TH-PPM UWB signal of the j-TH transmitting period is expressed as:
Where T f is the pulse repetition period, N f is the total number of pulses of the received signal, T is the clock time of the transmitter, To have a periodic pseudo-random time hopping code, for the kth target,T is an integer, N p is the period of the pseudo-random code, for a given value N h, atThe code element in the range is an integer, and the larger N h is, the lower the correlation between sequences is, and T c is the unit time-hopping width; delta is PPM modulated time shift, the data sequence { p j } transmitted by the transmitter is binary bit stream carrying some information, if the data symbol is 1, the single-period pulse will increase delta pulse time shift; if the data symbol is 0, there is no additional modulation time shift, w (t) is the energy normalized pulse shape,T b is the duration of the pulse,For the energy of the transmitted pulse, P t is the signal transmit power; if the pulse protection interval is gamma, the setting relation of each parameter should satisfy:
NhTc+δ+γ＜Tf
the signal received by the ith anchor node after passing through the channel can be expressed as:
sr(t)＝Aig(t-Δτ-tdi)+z(t)
Where Δτ represents an initial clock offset between the signal receiver and the transmitter, a i represents an amplitude attenuation of a signal transmitted by the target transmitter reaching the ith receiver after propagating through the path, g (t) =s (t) ×h (t) is a response function of a single pulse of normalized energy after passing through the multipath channel, t di represents a transmission delay between the transmitter and the ith receiver, and noise z (t) at the receiving end is additive white gaussian noise.
4. The method according to claim 1, wherein the communication frame structure includes a pilot sequence equivalent to a frame synchronization header in the IEEE802.15.4z protocol, a specific synchronization header equivalent to a frame delimiter SFD in the IEEE802.15.4z protocol, and DATA equivalent to PHR Payload in the IEEE802.15.4z protocol.
5. The method of claim 4, wherein a quasi-static time Tstatic is defined, the quasi-static time Tstatic covers the pilot sequence, the specific synchronization header, and the DATA, the timing error generated in Tstatic does not affect the DATA reception, and the acquisition synchronization and the timing adjustment are performed again after the transmission time exceeds Tstatic.
6. The method for integrating ultra-wideband communication and positioning compatible with IEEE 802.15.4z standard as claimed in claim 4, wherein the pilot sequence uses TOA estimation method based on matched filtering to perform pulse synchronization, and uses CFAR algorithm to perform pulse signal identification at the receiving end of the anchor node.
7. The method for integrating ultra-wideband communication and positioning compatible with IEEE 802.15.4z standard as claimed in claim 6, wherein the pilot sequence uses a TOA estimation method based on matched filtering to perform pulse synchronization, and the anchor node receiving end uses a CFAR algorithm to perform pulse signal identification, and the specific process comprises:
The discretized receiving signal and the environment noise in one frame interval are respectively set as r (n) and z (n), the local module signal is discretized into omega (n), and when one pulse exists in one frame time of the receiving end, the discretized receiving signal of the current frame is as follows:
r(n)＝Aw(n-τ(n))*h(n)+z(n)
Wherein A represents amplitude attenuation of a signal transmitted by a transmitter reaching a receiver after being propagated through a path, τ (n) represents a discretized numerical value of total transmission delay of the signal in one period, h (n) is a discretized multipath channel, and w (n) represents a discretized transmitted signal;
the decision variables of the matched filtering are:
Where N s is the number of signal samples in a frame interval, then the expected sum variance of r MF is:
Wherein the method comprises the steps of Is the variance of the noise;
Establishing a hypothesis testing model through parameters of a matched filtering decision variable r MF:
H0:
H1:
Wherein H 0 represents that only noise exists in one frame time of the receiving end, H 1 represents that a signal exists in one frame time, and:
μ0＝0,
the false alarm probability of the signal in the time period before the Anchor receives the pilot is expressed as:
The threshold value gamma for acquisition pilot is therefore:
Wherein, The threshold gamma is determined by limiting the false alarm probability P FA for the variance of the noise, the decision variable obtained by the matched filtering of the receiving end is compared with the threshold value, if the threshold value is exceeded, a pilot pulse is considered to be captured, otherwise, the current frame is noise.
8. The method for integrating ultra-wideband communication and positioning compatible with IEEE 802.15.4z standard as claimed in claim 6, wherein after pulse synchronization is completed, data reception is performed by adopting a reception mode of correlation detection, and correlation operation is performed between the received j-th frame signal of the i-th link and the local module signal:
The peak value of the cross-correlation function is the position of the captured pulse signal I.e., the time of arrival of the signal is estimated using the received data of a pulse in the received signal.
9. The integrated method for ultra-wideband communication and positioning according to claim 1, wherein the integrated calculation process for communication and positioning comprises:
Let the position coordinates of the target node be p= [ p x,py,pz]T, the positions of i anchor nodes are known, and expressed as r= [ x i,yi,zi]T, the propagation time of the signal from the target to the receiving point is:
Assuming that the time of a first pulse signal transmitted by a target is zero, the clock deviation of a receiving end and a transmitting end is delta tau, the modulation time of the j-th frame data is T j, and the pulse repetition interval is T f;
the arrival time estimate of the jth frame data of the ith link is:
The modulation time t j of each frame signal includes two parts of time hopping code modulation c jTc and pulse position modulation δa j;
the signal measurement and data demodulation process of the single anchor node is as follows:
Considering only the operation of the first receiver, when j 0 modulation data symbols are 0 and j 1 and j 2 modulation data symbols are 1, the operation of the first receiver is obtained by a correlation algorithm The values are respectivelyAndThe method can obtain:
Wherein the method comprises the steps of AndFor the arrival times of the j 0、j1 th and j 2 th pulse signals respectively,And c j2 are respectively pseudo-random time hopping codes corresponding to each pulse data modulation, and in ideal cases, the difference value of toa 0 and toa 1 is the length delta of PPM modulation, and toa 1 and toa 2 are equal; in the actual calculation process, setting a pulse position demodulation threshold value as delta/2, when toa 1-toa0 is more than delta/2, considering modulation data symbols of j 0 and j 1 pulses as 0 and 1 respectively, and when |toa 2-toa1 | < delta/2, considering modulation symbols of toa 2 and toa 1 as the same as each other as 1, namely finishing demodulation of information; meanwhile, toa 0、toa1 -delta and toa 2 -delta are estimated values of delta tau+t d1, and delta tau+t di of the jth pulse of the ith anchor point is recorded as tes ij;
the plurality of anchor nodes diversity demodulate data and realize the positioning process as follows:
Adopting a space diversity method, utilizing data demodulated by multiple anchor points to jointly calculate the error rate of a communication system, and for the same signal pulse, when the data demodulated by multiple anchor nodes are different, selecting the data according to the number of the anchor nodes with the same demodulation data;
from the estimate of Δτ+t d1, we can get:
wherein c represents the propagation velocity of electromagnetic waves in the air, the anchor node position r is known, and the target node estimated position Unknown, by equationSolving for clock bias Deltaτ and estimated position of target
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