CN111163029B - Method for searching positioning reference signal of enhanced machine type communication (e-MTC) - Google Patents

Abstract

The invention relates to the technical field of wireless communication, in particular to a method for searching a positioning reference signal of enhanced machine type communication (e-MTC), which comprises the following steps: s1: determining PRS signal information to be searched, a cell rough timing position and a retrieval range of PRS starting positions of different symbols in each cell subframe; s2: obtaining a PRS list to be searched of each sampling point according to the retrieval range; s3: performing FFT every other T sampling points; s4: obtaining a symbol level correlation result of a sampling point according to the FFT result; s5: and determining the accurate timing position of each cell according to the correlation result. S3 includes: s301: performing S303 to S304 every T sampling points; s303: acquiring sampling point data required by FFT; s304: and performing 128-point FFT operation according to the acquired sampling point data. The positioning reference signal searching method for enhancing the machine type communication e-MTC provided by the invention can reduce the calculation amount and the system complexity in the PRS signal searching process, reduce the hardware requirement of a receiver and improve the searching efficiency.

Description

Method for searching positioning reference signal of enhanced machine type communication (e-MTC)

Technical Field

The invention relates to the technical field of wireless communication, in particular to a method for searching a positioning reference signal of enhanced machine type communication (e-MTC).

Background

In a cellular communication system, a user needs to determine where he or she is located during use of the handset. Besides other systems, such as positioning modes like GPS and beidou, the LTE system roughly estimates the current position by receiving the signal strength in early use, and the accuracy is poor. Currently, in the LTE system, positioning reference signals PRS for positioning are added.

Each cell has an independent PRS signal, and the user side can obtain the distance difference between different base stations and users by measuring the arrival time difference of the cells of different base stations. After obtaining a plurality of pieces of time difference of arrival information, the base station position is known at the same time, and the accurate position of the user can be obtained.

PRS from multiple cells may be transmitted simultaneously and PRS signals may be long in duration, which increases the detection complexity of the receiver and requires higher measurement accuracy while detecting multiple cells in parallel.

In the R14 protocol of LTE, the parameter add-numDL-Frames-R14 is added in high-layer signaling, and the maximum value can be configured to be 160, namely PRS signals are continuously transmitted for 160 milliseconds, so that a receiver is required to search PRS in real time, and higher requirements are made on hardware processing capacity.

Disclosure of Invention

The invention provides a method for searching a positioning reference signal of enhanced machine type communication (e-MTC), which can greatly reduce the calculated amount and the system complexity in the PRS signal searching process, reduce the hardware capability requirement of a receiver, improve the searching efficiency and meet the requirement of real-time property.

In order to solve the technical problem, the present application provides the following technical solutions:

a method for searching a positioning reference signal of enhanced machine type communication (e-MTC) comprises the following steps:

s1: according to the high-level signaling, PRS signal information to be searched and a cell rough timing position on a certain frequency point are determined, and the retrieval range of PRS starting positions of different symbols in each cell subframe is determined;

s2: obtaining a PRS list to be searched corresponding to each sampling point according to the retrieval range obtained in the S1;

s3: performing FFT every other T sampling points;

s4: obtaining symbol level correlation results of all sampling points according to the FFT result;

s5: after symbol correlation results are combined in a subframe and among subframes, the accurate timing position of each cell is determined;

s3 includes:

s301: performing steps S303 to S304 every T sampling points;

s303: acquiring sampling point data required by FFT;

s304: and performing 128-point FFT operation according to the acquired sampling point data.

In the technical scheme of the invention, in the PRS signal searching process, FFT is not carried out on each sampling point, but FFT is carried out on every T sampling points at intervals, so that repeated operation among different FFT is effectively avoided, the system complexity is greatly reduced, the hardware capability requirement of a receiver is further reduced, and the searching speed is improved.

Further, the S1 includes:

s101: resolving PRS signal information of a reference cell and a neighboring cell in a high-level signaling, obtaining rough timing positions of different neighboring cells according to the time difference between the reference cell and the neighboring cell, and simultaneously obtaining SFN information of different subframes of each cell;

s102: and for each symbol of each cell, the search range of the symbol is obtained by taking the rough timing position as the center and the uncertainty as the width.

Further, S2 includes:

s201: receiving signals within 6 RB ranges at a certain frequency point, wherein the sampling rate is set to be 1.92M;

s202: starting from the initial position of the retrieval range of the first symbol of the subframe of the reference cell, and obtaining a PRS signal list to be detected on a current sampling point according to the time offset, symbol enable and subframe enable of different cells;

each element in the PRS signal list to be detected corresponds to a position to be retrieved within a symbol retrieval range of a subframe of a cell.

The frequency domain of the data part of the e-MTC system is only 6 RBs, so that the PRS signal is generally only detected within the bandwidth range of 6 RBs.

Further, the method further includes step S302: and judging whether all sampling points between the initial sampling point of the previous FFT and the sampling point of the next FFT corresponding to the current sampling point contain the PRS signal to be detected, if so, executing S303, and otherwise, skipping the FFT.

And if the PRS signal to be detected is not included, the FFT operation is directly skipped, so that invalid operation is reduced.

Further, S303 specifically includes:

s3031: acquiring L sampling point data before an FFT initial sampling point and 128+ M sampling point data from the initial sampling point;

s3032: the actual calculated values of the FFT sampling points are calculated as follows:

when n < M, fftin [ n ] ═ d [ n ] + d [128+ n ];

when n >127-L, fftin [ n ] ═ d [ n ] + d [ n-128 ];

otherwise, fftin [ n ] ═ d [ n ];

wherein, fftin [ n ] represents the actual calculation value of the nth sampling point when FFT of 128 points is carried out; n is an integer of 0 or more and 127 or less, d [ n ] represents data of a sample point with an index of n, the index of the sample point in S3032 takes the current FFT start sample point as a start index 0, and the range of the index of the sample point used in each FFT is [ -L,127+ M ].

By taking L and M sampling points more and taking the data after modulus superposition by 128 as the actual calculation value of the sampling points participating in FFT, the accuracy of data operation can be improved.

Further, S4 specifically includes:

s401: judging whether the current sampling point is an FFT starting point, if so, executing S402; if not, executing S403;

s402: after frequency domain data are obtained, locally and synchronously generating a PRS signal to be detected of the current element, carrying out differential correlation on the PRS signal and the PRS signal, and accumulating to obtain a symbol-level correlation result of the current element;

s403: and obtaining the symbol level correlation result of the current sampling point according to the result of the previous FFT and the result of the next FFT.

Further, the S403 specifically includes:

s4031: locally and synchronously generating a PRS signal to be detected of a current element;

s4032: multiplying the result of the previous FFT by a compensation factor exp (pi x t (1+2 x k)/128) at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 0;

s4033: multiplying the last FFT result by a compensation factor exp (pi (T-T) 1+2 k)/128 at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 1;

s4034: combining corr0 and corr1 to obtain a symbol level correlation result of the PRS signal to be detected on the current sampling point;

wherein T represents the index of the current sampling point, the index of the sampling point is set as the initial index 0 at the initial sampling point of the previous FFT, the index of the initial sampling point of the next FFT is T, T belongs to {1,2, …, T-1}, k represents the frequency domain subcarrier number, and the carrier number takes the central carrier as the initial number 0.

Further, in S4034, the symbol-level correlation result is obtained according to corr ═ (T-T)/T × corr0+ T/T × corr1, where corr represents the symbol-level correlation result.

Further, the S5 includes:

s501: accumulating the symbol level correlation results in the sub-frame and the inter-frame;

s502: and after the accumulated number among the sub-frames reaches a preset number, sequencing the amplitude values of the correlation results among the sub-frames of each cell, wherein the position of the maximum value is the accurate timing position.

Further, in S501, symbol-level correlation values in subframes are combined by using a coherent combining method, and symbol-level correlation values between subframes are combined by using an energy accumulation or differential correlation accumulation method.

Drawings

Fig. 1 is a flowchart illustrating a method for searching for a positioning reference signal in an enhanced machine type communication e-MTC according to an embodiment of the present invention.

Fig. 2 is a diagram of a PRS signal structure under normal CP in an embodiment of a positioning reference signal searching method for enhancing machine type communication e-MTC according to the present invention.

Fig. 3 is a schematic diagram illustrating processing of FFT input data in step S303 in an embodiment of a method for searching for a positioning reference signal for enhanced machine-type communication e-MTC according to the present invention.

Detailed Description

The following is further detailed by way of specific embodiments:

in order to solve the technical problem, the present application provides the following technical solutions:

as shown in fig. 1, a method for searching for a positioning reference signal for enhancing machine type communication e-MTC of the present embodiment includes the following steps:

s1: according to the high-level signaling, PRS signal information to be searched and a cell rough timing position on a certain frequency point are determined, and the retrieval range of PRS starting positions of different symbols in each cell subframe is determined;

s2: obtaining a PRS list to be searched corresponding to each sampling point according to the retrieval range obtained in the S1;

s3: performing FFT every other T sampling points;

s4: obtaining symbol level correlation results of all sampling points according to the FFT result;

s5: the symbol correlation results are combined within and between sub-frames to determine the precise timing position of each cell.

As shown in fig. 2, PRS signals are sent on port6 while avoiding symbols where CRS and control signaling are located. The data part of the e-MTC system has only 6 RBs in the frequency domain, so the PRS signal is generally detected only within the bandwidth range of 6 RBs.

Specifically, S1 includes:

s101: resolving PRS signal information of a reference cell and a neighboring cell in a high-level signaling, obtaining rough timing positions of different neighboring cells according to the time difference between the reference cell and the neighboring cell, and simultaneously obtaining SFN information of different subframes of each cell;

s102: and for each symbol of each cell, taking the rough timing position as a center and the uncertainty as a width to obtain a retrieval range of the symbol, namely the starting position and the ending position of the retrieval range.

S2 includes:

s201: the receiver sets the sampling rate to be 1.92M at a certain frequency point, and receives signals in 6 RB ranges;

s202: starting from the initial position of the retrieval range of the first symbol of the subframe of the reference cell, and obtaining a PRS signal list to be detected on a current sampling point according to the time offset, symbol enable and subframe enable of different cells; each element in the PRS signal list to be detected corresponds to a position to be retrieved within a symbol retrieval range of a subframe of a cell.

S3 includes:

s301: starting from the initial position of the search range, executing steps S303 to S304 every T sampling points; in the present embodiment, T is preferably 32.

S303: acquiring sampling point data required by FFT;

s304: and performing 128-point FFT operation according to the acquired sampling point data.

Before executing S303, S302 is also executed: and judging whether all sampling points between the initial sampling point of the previous FFT and the sampling point of the next FFT (not including two ends) corresponding to the current sampling point contain the PRS signal to be detected, if so, executing S303, and otherwise, skipping the FFT.

As shown in fig. 3, S303 specifically includes:

s3031: acquiring L sampling point data before an FFT initial sampling point and 128+ M sampling point data from the initial sampling point;

s3032: the actual calculated values of the FFT sampling points are calculated as follows:

when n < M, fftin [ n ] ═ d [ n ] + d [128+ n ];

when n >127-L, fftin [ n ] ═ d [ n ] + d [ n-128 ];

otherwise, fftin [ n ] ═ d [ n ];

wherein, fftin [ n ] represents the actual calculation value of the nth sampling point when FFT of 128 points is carried out; n is an integer greater than or equal to 0 and less than or equal to 127, d [ n ] represents data of a sample point with an index of n, the index of the sample point in S3032 takes the current FFT initial sample point as an initial index 0, the index range of the sample point used in each FFT is [ -L,127+ M ], and in the embodiment, L and M are respectively 9 and 32.

In S4, for each sampling point, a symbol-level correlation result of each element is calculated according to its corresponding PRS signal list to be detected, and the specific steps are as follows:

s401: judging whether the current sampling point is an FFT starting point, if so, executing S402; if not, executing S403;

s402: after frequency domain data are obtained, locally and synchronously generating a PRS signal to be detected of the current element, carrying out differential correlation on the PRS signal and the PRS signal, and accumulating to obtain a symbol-level correlation result of the current element;

s403: and obtaining the symbol level correlation result of the current sampling point according to the result of the previous FFT and the result of the next FFT. Specifically, S403 includes:

s4031: locally and synchronously generating a PRS signal to be detected of a current element;

s4032: multiplying the result of the previous FFT by a compensation factor exp (pi x t (1+2 x k)/128) at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 0;

s4033: multiplying the last FFT result by a compensation factor exp (pi (T-T) 1+2 k)/128 at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 1;

s4034: combining corr0 and corr1 to obtain a symbol level correlation result of the PRS signal to be detected on the current sampling point; in this embodiment, the coefficient of corr0 and corr1 is linear with T, i.e. the sign-level correlation result is obtained from corr ═ (T-T)/T ═ corr0+ T/T × corr 1.

Wherein T represents the index of the current sampling point, the index of the sampling point is set as the initial index 0 at the initial sampling point of the previous FFT, the index of the initial sampling point of the next FFT is T, T belongs to {1,2, …, T-1}, k represents the number of the frequency domain subcarrier, the number of the carrier takes the central carrier as the initial number 0, and corr represents the symbol level correlation result.

S5 includes:

s501: accumulating the symbol level correlation results in the sub-frame and the inter-frame; in S501, symbol-level correlation values in subframes are combined by a coherent combining method, and symbol-level correlation values between subframes are combined by an energy accumulation or differential correlation accumulation method.

S502: and after the accumulated number among the sub-frames reaches a preset number, sequencing the amplitude values of the correlation results among the sub-frames of each cell, wherein the position of the maximum value is the accurate timing position. In S501, for each sampling point, a plurality of calculated correlation results of the symbol level of the PRS signal to be detected are accumulated to a correlation value in a subframe corresponding to a search position of a corresponding cell. And the related values in the subframes of all the retrieval positions of each cell are backed up and cleared at the initial position of each subframe of the corresponding cell. And after all symbols of the correlation values in the sub-frames of each cell are calculated, energy or difference results between the sub-frames are obtained and then accumulated into the correlation value results between the sub-frames of each cell.

In the scheme of the embodiment, in the PRS signal searching process, FFT is not performed on each sampling point, but FFT is performed on every T sampling points at intervals, so that repeated operation among different FFT is effectively avoided, the system complexity is greatly reduced, the hardware capability requirement of a receiver is further reduced, and the searching speed is increased.

If all the sampling points of all the cells are subjected to FFT operation, the complexity is high. Assuming that the current system has 8 cells, the time uncertainty of each cell is 384 samples, and each subframe has 8 symbols with PRS, then there are 1920 samples in total in each subframe, 1920 + 138 + 137 + 2+ 384-1892 points which need to be subjected to FFT, and the total number of FFTs which need to be subjected to FFT is 8+ 1892-15136 FFTs; even though, by simplification, 32 samples are taken for one FFT, 473 FFTs are required.

The method searches a plurality of cells in parallel, avoids repeated operation of a plurality of FFT between different symbols, and only needs to carry out 1920/32-60 FFT on a plurality of cells in each subframe.

Therefore, the method greatly reduces the complexity of the system, can effectively improve the PRS searching efficiency and meets the real-time requirement.

The above are merely examples of the present invention, and the present invention is not limited to the field related to this embodiment, and the common general knowledge of the known specific structures and characteristics in the schemes is not described herein too much, and those skilled in the art can know all the common technical knowledge in the technical field before the application date or the priority date, can know all the prior art in this field, and have the ability to apply the conventional experimental means before this date, and those skilled in the art can combine their own ability to perfect and implement the scheme, and some typical known structures or known methods should not become barriers to the implementation of the present invention by those skilled in the art in light of the teaching provided in the present application. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.

Claims (5)

1. A method for searching a positioning reference signal of enhanced machine type communication (e-MTC), is characterized in that: the method comprises the following steps:

s1: according to the high-level signaling, PRS signal information to be searched and a cell rough timing position on a certain frequency point are determined, and the retrieval range of PRS starting positions of different symbols in each cell subframe is determined;

s2: obtaining a PRS list to be searched corresponding to each sampling point according to the retrieval range obtained in the S1;

s3: performing FFT every other T sampling points;

s4: obtaining symbol level correlation results of all sampling points according to the FFT result;

s5: after symbol correlation results are combined in a subframe and among subframes, the accurate timing position of each cell is determined;

s3 includes:

s301: performing steps S303 to S304 every T sampling points;

s303: acquiring sampling point data required by FFT;

s304: performing 128-point FFT operation according to the acquired sampling point data;

s4 specifically includes:

s401: judging whether the current sampling point is an FFT starting point, if so, executing S402; if not, executing S403;

s402: after frequency domain data are obtained, locally and synchronously generating a PRS signal to be detected of the current element, carrying out differential correlation on the PRS signal and the PRS signal, and accumulating to obtain a symbol-level correlation result of the current element;

s403: obtaining a symbol-level correlation result of the current sampling point according to the result of the previous FFT and the result of the next FFT;

the S403 specifically includes:

s4031: locally and synchronously generating a PRS signal to be detected of a current element;

s4032: multiplying the result of the previous FFT by a compensation factor exp (pi x t (1+2 x k)/128) at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 0;

s4033: multiplying the last FFT result by a compensation factor exp (pi (T-T) 1+2 k)/128 at different frequency domain positions, correlating the result with frequency domain data corresponding to the local sequence, and accumulating to obtain a symbol-level correlation value corr 1;

s4034: combining corr0 and corr1 to obtain a symbol level correlation result of the PRS signal to be detected on the current sampling point;

wherein T represents the index of the current sampling point, the index of the sampling point is set as the initial index 0 at the initial sampling point of the previous FFT, the index of the initial sampling point of the next FFT is T, T belongs to {1,2, …, T-1}, k represents the frequency domain subcarrier number, and the carrier number takes the central carrier as the initial number 0;

in S4034, a symbol-level correlation result is obtained according to corr = (T-T)/T × corr0+ T/T × corr1, where corr represents the symbol-level correlation result;

the S5 includes:

s501: accumulating the symbol level correlation results in the sub-frame and the inter-frame;

s502: after the accumulated number among the sub-frames reaches a preset number, sequencing the amplitude values of the correlation results among the sub-frames of each cell, wherein the position of the maximum value is the accurate timing position;

in S501, symbol-level correlation values in subframes are combined by a coherent combining method, and symbol-level correlation values between subframes are combined by an energy accumulation or differential correlation accumulation method.

2. The method of claim 1, wherein the method comprises: the S1 includes:

s101: resolving PRS signal information of a reference cell and a neighboring cell in a high-level signaling, obtaining rough timing positions of different neighboring cells according to the time difference between the reference cell and the neighboring cell, and simultaneously obtaining SFN information of different subframes of each cell;

s102: and for each symbol of each cell, the search range of the symbol is obtained by taking the rough timing position as the center and the uncertainty as the width.

3. The method of claim 1, wherein the method comprises: s2 includes:

s201: receiving signals within 6 RB ranges at a certain frequency point, wherein the sampling rate is set to be 1.92M;

s202: starting from the initial position of the retrieval range of the first symbol of the subframe of the reference cell, and obtaining a PRS signal list to be detected on a current sampling point according to the time offset, symbol enable and subframe enable of different cells;

each element in the PRS signal list to be detected corresponds to a position to be retrieved within a symbol retrieval range of a subframe of a cell.

4. The method of claim 1, wherein the method comprises: further comprising S302: and judging whether all sampling points between the initial sampling point of the previous FFT and the sampling point of the next FFT corresponding to the current sampling point contain the PRS signal to be detected, if so, executing S303, and otherwise, skipping the FFT.

5. The method of claim 4, wherein the method comprises: the S303 specifically includes:

s3031: acquiring L sampling point data before an FFT initial sampling point and 128+ M sampling point data from the initial sampling point;

s3032: the actual calculated values of the FFT sampling points are calculated as follows:

when n < M, fftin [ n ] = d [ n ] + d [128+ n ];

when n >127-L, fftin [ n ] = d [ n ] + d [ n-128 ];

otherwise, fftin [ n ] = d [ n ];

wherein, fftin [ n ] represents the actual calculation value of the nth sampling point when FFT of 128 points is carried out; n is an integer of 0 or more and 127 or less, d [ n ] represents data of a sample point with an index of n, the index of the sample point in S3032 takes the current FFT start sample point as a start index 0, and the range of the index of the sample point used in each FFT is [ -L,127+ M ].

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