Maximum delay spread estimation optimization method in wireless ad hoc network

Abstract

The invention particularly relates to a maximum delay spread estimation optimization method in a wireless ad hoc network. According to the maximum delay spread estimation optimization method in the wireless ad hoc network, after a signal r is received, the conjugate product h of a pilot frequency position signal and a reference symbol is calculated firstly, then the frequency domain correlation Corr and the product f (m) of the frequency domain correlation and a filter coefficient are calculated, post-processing is conducted on the product f (m), and the gear of maximum delay spread is selected; when the maximum delay spread gear of the continuous A subframes is not changed and the receiving node number is not changed, reducing the estimation frequency of the maximum delay spread; and when the estimation result changes or the receiving node number changes, the estimation of the maximum delay spread in each sub-frame is restarted. According to the maximum time delay spread estimation optimization method in the wireless ad hoc network, time delay spread areas can be clearly divided in different scenes, the maximum time delay spread of a channel is further estimated, the calculation complexity is reduced, and the calculation error-tolerant rate is also improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly to an optimization method for estimating the maximum delay spread in a wireless ad hoc network. Background Art

[0002] A wireless ad hoc network is different from traditional wireless communication technologies and is an independent network autonomous system. It does not rely on a fixed backbone network (but can cooperate with it) or a base station, can be quickly deployed, and establish a complete, powerful, and highly survivable network communication system to provide effective data and multimedia communication services. All hosts in a wireless ad hoc network can move freely, and the hosts are connected by wireless links. The wireless ad hoc network has the characteristics of high mobility, high convenience, and easy construction, and has great development prospects in scenarios such as the Internet of Things, wireless cities, smart furniture, robot communication, and quickly building a communication network during emergency rescue.

[0003] Channel estimation, as one of the key technologies in the field of wireless communication, is widely used in communication scenarios such as 3G / LTE / NR. Among them, the LMMSE channel estimation algorithm based on the maximum delay spread also has a large number of applications and optimization schemes in the algorithms of various wireless receiving devices. Estimating the maximum delay spread by designing a suitable filter to divide the time domain length of the received signal PDP into bins is a scheme with relatively high accuracy and low complexity.

[0004] In a wireless ad hoc network, if relatively accurate channel estimation is to be achieved, a relatively high requirement is also put forward for the accuracy of the algorithm for estimating the maximum delay spread. However, the application scenarios of wireless ad hoc networks are diverse, and different scenarios have different channel change characteristics. In actual applications, the existing algorithms for estimating the maximum delay spread will have problems such as relatively high computational complexity or limited accuracy.

[0005] The signal received by a wireless receiver arrives at the receiver through different direct, reflected, refracted, etc. paths. Since the distances of the signals passing through each path are different, the arrival times in each path are different, resulting in multipath delay spread. The time difference between the first and the last clearly distinguishable paths is considered the maximum delay spread, as shown in the appendix Figure 1 as follows.

[0006] Classify common wireless channels, and the corresponding maximum delay spread length can be divided into 1 / 4 CP length, 1 / 2 CP length, and 1 CP length. By filtering the PDP spectrum of the received signal using filters corresponding to the three lengths, a most matching filter can be selected, and the corresponding length is the maximum delay spread to be estimated. Since the PDP spectrum and the frequency-domain correlation are Fourier transforms of each other, filtering the PDP spectrum in the time domain is equivalent to multiplying the frequency-domain correlation by the coefficients corresponding to a set of filters in the frequency domain.

[0007] In a wireless ad hoc network, since the receiving end may encounter node handover in any subframe, the existing solution estimates the maximum delay spread in each subframe. Then, in a scenario where node handover is not frequent, this will cause the problem of increased power consumption.

[0008] To solve the above problems, the present invention proposes an optimization method for estimating the maximum delay spread in a wireless ad hoc network. Summary of the Invention

[0009] In order to make up for the deficiencies of the prior art, the present invention provides a simple and efficient optimization method for estimating the maximum delay spread in a wireless ad hoc network.

[0010] The present invention is realized by the following technical solutions:

[0011] An optimization method for estimating the maximum delay spread in a wireless ad hoc network, characterized in that it includes the following steps:

[0012] Step S1, receive the signal r;

[0013] Step S2, calculate the product h of the pilot position signal and the conjugate of the reference symbol;

[0014] In the step S2, the calculation process is as follows:

[0015] Step S2.1, extract the signal value r j at the pilot position p pj from the received signal r;

[0016] Step S2.2, calculate the conjugate complex number j of the reference symbol s

[0017] Step S2.3, calculate the product h of the pilot position signal and the conjugate of the reference symbol; j ;

[0018]

[0019] Step S2.4, summarize the product results of all pilot positions into a vector h;

[0020] h = [h1, h2, ..., h v

[0021] where v is the total number of known pilot symbol positions.

[0022] Step S3: Calculate the frequency-domain correlation Corr, and the calculation formula is as follows:

[0023]

[0024] where N is the number of pilots on each reference symbol;

[0025] The minimum frequency-domain correlation length L required to restore the PDP shape is 72. When using equally spaced frequency-domain correlation operations, the relationship between the correlation length L and the correlation interval is as follows:

[0026] L = Nlag × delta

[0027] where Nlag represents the number of points of the frequency-domain correlation, and delta represents the correlation interval;

[0028] To reduce the computational complexity, the delta value is customarily selected as 2, and the Nlag value is 36, that is, i = 0, 2, 4, ..., 70;

[0029] Step S4: Calculate the product f(m) of the frequency-domain correlation and the filtering coefficient, and the calculation formula is as follows;

[0030]

[0031] where w(m, n) are 3 groups of filtering coefficients corresponding to three filters;

[0032] The maximum delay spread lengths corresponding to the filters are 1 / 4 CP length, 1 / 2 CP length, and 1 CP length;

[0033] In the said Step S3, the unequally spaced frequency-domain correlation is calculated as follows:

[0034]

[0035] i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0036] Correspondingly, in the said Step S4, the calculation formula of f(m) is as follows:

[0037]

[0038] ​i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0039] By calculating the frequency-domain correlation of non-uniform intervals, the amount of computation is reduced by half compared to the frequency-domain correlation operation of uniform intervals. The calculation of the 36-point frequency-domain correlation is optimized to the calculation of the 18-point frequency-domain correlation. At the same time, the amount of computation of f(m) is also halved.

[0040] In step S3, since the frequency-domain correlation of different symbols changes slowly on the same transceiver antenna pair, the alpha filter is used to update the value of the signal based on the weighted average of the current value and the historical value;

[0041] For the same symbol, there is a large difference between different transceiver antenna pairs, and it is not suitable for merging or averaging processing; for a 2 transmit and 2 receive system, the non-uniform interval frequency-domain correlation operation is adopted to calculate the frequency-domain correlation of different antenna pairs, that is:

[0042] Corr(iRx, iTx, i), iRx = 0, 1, iTx = 0, 1,

[0043] i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0044] Among them, iRx is the index of the receiver at the receiving end, and iTx is the index of the transmitter at the sending end.

[0045] Step S5: Post-process the product f, and select the gear with the maximum delay spread, specifically as follows:

[0046] Use f(2) for normalization to obtain parameters x and y, that is

[0047]

[0048] If both parameter x and parameter y are greater than 0.92, then set parameter idxRegion to 1, the maximum delay spread is one-fourth of the cyclic prefix (CP), and the maximum delay spread length corresponding to the filter is 1 / 4CP length;

[0049] If parameter x is not greater than 0.92, but parameter y is greater than 0.92, then set parameter idxRegion to 2, indicating that the maximum delay spread is half of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 / 2CP length;

[0050] If both parameter x and parameter y are not greater than 0.92, set parameter idxRegion to 3, indicating that the maximum delay spread is equal to the length of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 CP length;

[0051] Step S6: Estimate the maximum delay spread for each subframe in the initial state. When the maximum delay spread level does not change for consecutive A subframes and the receiving node number remains unchanged, reduce the estimation frequency of the maximum delay spread and change it to perform frequency-domain correlation calculation and maximum delay spread estimation every 5 subframes. After that, when the maximum delay spread estimation level does not change for consecutive B times and the receiving node number remains unchanged, that is, after 5*B subframe durations, reduce the estimation frequency of the maximum delay spread again and change it to perform frequency-domain correlation calculation and maximum delay spread estimation every 10 subframes;

[0052] Among them, both A and B are parameters configured by the user;

[0053] Correspondingly, when the estimation result of the maximum delay spread level between subframes changes or the receiving node number changes, restart the estimation of the maximum delay spread for each subframe and repeat the above process.

[0054] In the theoretical analysis, f(0) < f(2), f(1) < f(2), so the values of x and y are both less than 1. However, through a large number of simulations, it is found that there will be cases where the calculated values of x and y in individual subframes are greater than 1, which is inconsistent with the theoretical analysis. This is due to the estimation error and fixed-point quantization error in the simulation. Therefore, in actual estimation, to avoid the influence of this error, in step S5, an adjustment factor δ is added to the calculation formulas of parameter x and y values, that is:

[0055]

[0056] Among them, δ is a parameter configured by the user. For example, δ = 1 / 32 can be selected.

[0057] In step S5, for a 2 transmit and 2 receive system, calculate the maximum delay spread idxRegion(iRx, iTx) estimated for different antenna pairs, and the final estimation result takes the maximum value among them, that is:

[0058] idxRegion = max(idxRegion(iRx, iTx))

[0059] where iRx = 0, 1, iTx = 0, 1.

[0060] An optimization device for estimating the maximum delay spread in a wireless ad hoc network, characterized in that it includes a memory and a processor; the memory is used to store computer programs, and the processor is used to implement the above method steps when executing the computer programs.

[0061] A readable storage medium, characterized in that: a computer program is stored on the readable storage medium, and when the computer program is executed by a processor, the above method steps are implemented.

[0062] The beneficial effect of the present invention is that: for the main application scenarios and pilot patterns of the wireless ad hoc network, the maximum delay spread estimation optimization method of the present invention provides an algorithm for estimating the maximum delay spread, which can clearly divide the delay spread region in different scenarios, and then estimate the maximum delay spread of the channel, not only reducing the computational complexity, but also improving the computational fault tolerance rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0064] Attached Figure 1 is a schematic diagram of the maximum delay spread of the present invention.

[0065] Attached Figure 2 is a schematic diagram of the optimization method for estimating the maximum delay spread in the wireless ad hoc network of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0066] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0067] The optimization method for estimating the maximum delay spread in the wireless ad hoc network includes the following steps:

[0068] Step S1, receiving the signal r;

[0069] Step S2, calculating the conjugate product h of the pilot position signal and the reference symbol;

[0070] In the step S2, the calculation process is as follows:

[0071] Step S2.1: Extract the pilot position p from the received signal r j and the signal value r pj ;

[0072] Step S2.2: Calculate the conjugate complex number of the reference symbol s j ;

[0073] Step S2.3: Calculate the product h of the pilot position signal and the conjugate of the reference symbol j ;

[0074]

[0075] Step S2.4: Aggregate the product results at all pilot positions into a vector h;

[0076] h = [h1, h2,..., h v

[0077] where v is the total number of positions of the known pilot symbols.

[0078] Step S3: Calculate the frequency-domain correlation Corr, and the calculation formula is as follows:

[0079]

[0080] where N is the number of pilots on each reference symbol;

[0081] The minimum frequency-domain correlation length L required to restore the PDP shape is 72. When using equally spaced frequency-domain correlation operations, the relationship between the correlation length L and the correlation interval is as follows:

[0082] L = Nlag × delta

[0083] where Nlag represents the number of points of the frequency-domain correlation, and delta represents the correlation interval;

[0084] To reduce the computational complexity, the delta value is customarily selected as 2, and the Nlag value is 36, that is, i = 0, 2, 4,..., 70;

[0085] Step S4: Calculate the product f(m) of the frequency-domain correlation and the filter coefficient, and the calculation formula is as follows;

[0086]

[0087] where w(m,n) are 3 groups of filter coefficients corresponding to three filters;

[0088] The maximum delay spread lengths corresponding to the filters are 1 / 4 CP length, 1 / 2 CP length, and 1 CP length respectively;​

[0089] In step S3, the non-uniform frequency-domain correlation is calculated as follows:

[0090]

[0091] i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0092] Correspondingly, in step S4, the calculation formula of f(m) is as follows:

[0093]

[0094] i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0095] By calculating the non-uniform frequency-domain correlation, the amount of computation is reduced by half compared with the uniform frequency-domain correlation operation. The calculation of the 36-point frequency-domain correlation is optimized to the calculation of the 18-point frequency-domain correlation, and at the same time, the amount of computation of f(m) is also halved.

[0096] In step S3, due to different symbols, the frequency-domain correlation on the same transceiver antenna pair changes slowly, and the alpha filter is used to update the signal value according to the weighted average of the current value and the historical value;

[0097] For the same symbol, there is a large difference on different transceiver antenna pairs, and it is not suitable for merging or averaging processing; for a 2-transmitter and 2-receiver system, the non-uniform frequency-domain correlation operation is adopted to calculate the frequency-domain correlation on different antenna pairs, that is:

[0098] Corr(iRx, iTx, i), iRx = 0, 1, iTx = 0, 1

[0099] i = 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 26, 32, 38, 44, 52, 60, 70;

[0100] where iRx is the index of the receiver Receiver, and iTx is the index of the transmitter Transmitter.

[0101] Step S5: Post-process the product f and select the gear with the maximum delay spread, specifically as follows:

[0102] Use f(2) for normalization to obtain parameters x and y, that is

[0103]

[0104] If both parameter x and parameter y are greater than 0.92, set parameter idxRegion to 1. The maximum delay spread is one quarter of the cyclic prefix (CP), and the maximum delay spread length corresponding to the filter is 1 / 4 of the CP length;

[0105] If parameter x is not greater than 0.92, but parameter y is greater than 0.92, set parameter idxRegion to 2, indicating that the maximum delay spread is half of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 / 2 of the CP length;

[0106] If both parameter x and parameter y are not greater than 0.92, set parameter idxRegion to 3, indicating that the maximum delay spread is equal to the length of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 CP length;

[0107] Step S6: Estimate the maximum delay spread for each subframe in the initial state. When the maximum delay spread level does not change for consecutive A subframes and the receiving node number remains unchanged, reduce the estimation frequency of the maximum delay spread and change it to perform frequency-domain correlation calculation and maximum delay spread estimation every 5 subframes. After that, when the maximum delay spread estimation level does not change for consecutive B times and the receiving node number remains unchanged, that is, after 5*B subframe durations, reduce the estimation frequency of the maximum delay spread again and change it to perform frequency-domain correlation calculation and maximum delay spread estimation every 10 subframes;

[0108] Among them, both A and B are parameters configured by the user;

[0109] Correspondingly, when the estimation result of the maximum delay spread level between subframes changes or the receiving node number changes, restart the estimation of the maximum delay spread for each subframe and repeat the above process.

[0110] In theoretical analysis, f(0) < f(2), f(1) < f(2), so the values of x and y are both less than 1. However, through a large number of simulations, it is found that there will be cases where the calculated values of x and y in individual subframes are greater than 1, which does not conform to the theoretical analysis. This is due to the estimation error and fixed-point quantization error in the simulation. Therefore, in actual estimation, to avoid the influence of this error, in step S5, an adjustment factor δ is added to the calculation formula of parameter x and y values, that is:

[0111]

[0112] Among them, δ is a parameter configured by the user. For example, δ = 1 / 32 can be selected.

[0113] In step S5, for a 2 - transmit 2 - receive system, the maximum delay spread idxRegion(iRx, iTx) estimated for different antenna pairs is calculated, and the final estimated result takes the maximum value among them, that is:

[0114] idxRegion = max(idxRegion(iRx, iTx))

[0115] where iRx = 0, 1 and iTx = 0, 1.

[0116] The device for optimizing the estimation of the maximum delay spread in the wireless ad - hoc network includes a memory and a processor; the memory is used to store computer programs, and the processor is used to implement the above - mentioned method steps when executing the computer programs.

[0117] A computer program is stored on the readable storage medium, and when the computer program is executed by a processor, the above - mentioned method steps are implemented.

[0118] Compared with the prior art, the method for optimizing the estimation of the maximum delay spread in the wireless ad - hoc network provides an algorithm for estimating the maximum delay spread for the main application scenarios and pilot patterns of the wireless ad - hoc network. In different scenarios, the regions of the delay spread can be clearly divided, and then the maximum delay spread of the channel can be estimated. This not only reduces the computational complexity but also improves the computational fault tolerance.

[0119] The above - described embodiments are only one of the specific implementation manners of the present invention. The ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for estimating the maximum delay spread in a wireless ad hoc network, characterized in that: The following steps are involved: Step S1, receiving a signal r; Step S2, calculating the conjugate product h of the pilot position signal and the reference symbol; Step S3, calculate the frequency domain correlation Corr, the calculation formula is as follows: Where N is the number of pilots on each reference symbol; The minimum frequency domain correlation length L required to restore the PDP shape is 72. When the frequency domain correlation operation is performed with equal intervals, the relationship between the correlation length L and the correlation interval is as follows: L = Nlag × delta Among them, Nlag represents the number of frequency domain correlation points, and delta represents the correlation interval; To reduce the computational complexity, the custom delta value is 2, then the Nlag value is 36, i.e., i = 0, 2, 4, ..., 70; Step S4, calculate the product f(m) of the frequency domain correlation and the filter coefficient, the calculation formula is as follows; Among them, w(m,n) is the three sets of filter coefficients corresponding to the three filters; The maximum delay spread length corresponding to the filter is divided into 1 / 4 CP length, 1 / 2 CP length and 1 CP length; Step S5: post-process the product f(m) and select the gear position with the maximum delay spread, as follows: Normalize the product f(m) to get the parameters x and y, that is: If both parameter x and parameter y are greater than 0.92, the parameter idxRegion is set to 1, the maximum delay spread is one quarter of the cyclic prefix (CP), and the maximum delay spread length corresponding to the filter is 1 / 4 of the CP length; If the parameter x is not greater than 0.92, but the parameter y is greater than 0.92, the parameter idxRegion is set to 2, indicating that the maximum delay spread is half of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 / 2CP length; If both parameter x and parameter y are not greater than 0.92, the parameter idxRegion is set to 3, indicating that the maximum delay spread is equal to the length of the cyclic prefix, and the maximum delay spread length corresponding to the filter is 1 CP length; Step S6: In the initial state, each subframe estimates the maximum delay spread. When the maximum delay spread position of A consecutive subframes does not change and the receiving node number remains unchanged, the estimation frequency of the maximum delay spread is reduced, and the frequency domain correlation calculation and the maximum delay spread estimation are performed once every 5 subframes. After that, when the maximum delay spread estimation position does not change for B consecutive times and the receiving node number remains unchanged, that is, after 5*B subframes, the estimation frequency of the maximum delay spread is reduced again, and the frequency domain correlation calculation and the maximum delay spread estimation are performed once every 10 subframes. Among them, A and B are parameters configured by the user; Correspondingly, when the estimation result of the maximum delay spread gear between subframes changes or the receiving node number changes, the maximum delay spread estimation is restarted in each subframe and the above process is repeated.

2. The method for estimating the maximum delay spread in a wireless ad hoc network according to claim 1, wherein: In step S2, the calculation process is as follows: Step S2.1: Extract the pilot position p from the received signal r j and the signal value r pj ; Step S2.2, calculate the conjugate complex number of the reference symbol s j ​ Step S2.3, calculate the conjugate product h of the pilot position signal and the reference symbol j ; Step S2.4, summarizing the product results of all pilot positions into a vector h; Wherein, v is the total number of known pilot symbol positions.

3. The method for estimating the maximum delay spread in a wireless ad hoc network according to claim 1, wherein: In step S3, the frequency domain correlation calculation using non-equal intervals is as follows: i＝0,2,4,6,8,10,12,14,16,18,20,26,32,38,44,52,60,70； Correspondingly, in the step S4, the calculation formula of f(m) is as follows: i＝0,2,4,6,8,10,12,14,16,18,20,26,32,38,44,52,60,70； By calculating the frequency-domain correlation of non-uniform intervals, the amount of computation is reduced by half compared with the frequency-domain correlation operation of uniform intervals, which is optimized from calculating the 36-point frequency-domain correlation to calculating the 18-point frequency-domain correlation. At the same time, the amount of computation of f(m) is also halved.

4. The method for estimating the maximum delay spread in a wireless ad hoc network according to claim 3, characterized in that: In the step S3, for the same symbol, there is a large difference between different transceiver antenna pairs, so it is not suitable for merging or averaging processing; for a 2 transmit and 2 receive system, the frequency-domain correlation of non-uniform intervals is used to calculate the frequency-domain correlation of different antenna pairs, that is: Corr(iRx,iTx,i), iRx = 0,1, iTx = 0,1 i＝0,2,4,6,8,10,12,14,16,18,20,26,32,38,44,52,60,70 where iRx is the index of the receiver at the receiving end, and iTx is the index of the transmitter at the transmitting end.

5. The method for estimating the maximum delay spread in a wireless ad hoc network according to claim 1, wherein: In order to avoid the situation where the values of x and y are greater than 1 caused by estimation error and fixed-point quantization error, in the step S5, an adjustment factor δ is added to the calculation formula of the parameters x and y values, that is: where δ is a parameter configured by the user.

6. The method for estimating the maximum delay spread in a wireless ad hoc network according to claim 5, wherein: In the step S5, for a 2 transmit and 2 receive system, the maximum delay spread estimated for different antenna pairs is calculated idxRegion(iRx,iTx), and the final estimation result takes the maximum value among them, that is: idxRegion = max(idxRegion(iRx,iTx)) where iRx = 0,1, iTx = 0,1.

7. An apparatus for estimating the maximum delay spread in a wireless ad hoc network, characterized in that: It includes a memory and a processor; the memory is used to store a computer program, and the processor is used to implement the method steps described in any one of claims 1 to 6 when executing the computer program.

8. A readable storage medium, characterized in that: A computer program is stored on the readable storage medium, and when the computer program is executed by the processor, the method steps described in any one of claims 1 to 6 are implemented.

Images