CN117538821A - Channel estimation-based multi-path interference resistance method for underground long and narrow space of coal mine - Google Patents

Abstract

The invention discloses a coal mine underground long and narrow space multipath interference resisting method based on channel estimation, which comprises the following steps: and selecting a training sequence from the roadway communication electromagnetic waves, and transmitting the sequence through a transmitting antenna by a transmitting end. The receiving end receives the signal using the receiving antenna and estimates the channel response. And the receiving end decodes the received signal by calculating the signal-to-noise ratio and the channel weight of each channel to obtain a signal estimated value of the transmitting end. To solve the problem that multipath effects may severely degrade the accuracy of UWB positioning.

Description

Channel estimation-based multi-path interference resistance method for underground long and narrow space of coal mine

Technical Field

The invention relates to a coal mine underground long and narrow space multipath interference resistance method based on channel estimation, and belongs to the technical field of long and narrow path positioning.

Background

In the field of modern indoor positioning, ultra Wideband (UWB) positioning technology has received widespread attention due to its high accuracy and robustness. UWB positioning technology is based on ultra wideband wireless communication technology, which can provide positioning accuracy on the order of centimeters. UWB signals have the characteristics of short pulse, wide band and low power, which enables them to achieve high accuracy positioning in complex indoor environments. The principle of operation is to estimate the distance by measuring the Time of Arrival (ToA) or signal strength (Received Signal Strength Indicator, RSSI) of a pulse signal between transmission and reception, thereby determining the target position.

However, UWB positioning technology presents challenges in certain application scenarios, such as elongate roadways downhole in coal mines. Because the tunnel is a closed long and narrow space, UWB signals can be shielded by the tunnel wall when in transmission, and multiple reflections of the signals are caused. This phenomenon means that the wireless receiving end may receive signals from a plurality of transmission paths, thereby forming a so-called multipath effect. Multipath is a signal propagation phenomenon due to signal reflection, refraction and scattering, which interferes with the original signal, thereby affecting positioning accuracy. In such an environment in the coal mine, multipath effects may seriously reduce the accuracy of UWB positioning, bringing hidden danger to miners.

In summary, although UWB positioning technology is excellent in many indoor environments, its performance may be affected by multipath effects in specific application scenarios, such as long and narrow roadways under coal mine, and further technical improvements and optimization are needed.

Disclosure of Invention

The invention aims to solve the technical problems that: the method for resisting multipath interference in the underground long and narrow space of the coal mine based on the channel estimation is provided to overcome the defects in the prior art.

The technical scheme of the invention is as follows: a method for multipath interference resistance in an underground long and narrow space of a coal mine based on channel estimation, the method comprising the following steps:

s01, selecting electromagnetic waves with the same frequency and amplitude from roadway communication electromagnetic waves as training sequences;

s02, if the transmitting end passesThe dry root transmitting antenna transmits the training sequence, x _i Representing a training sequence transmitted by an ith antenna;

s03, the receiving end receives signals through a plurality of receiving antennas, y _j Representing the signal received by the jth antenna;

the receiving end receives the signal y _j And training sequence x _i The difference between them to estimate the channel responseThe estimation method is as follows:

wherein E [. Cndot.]Representing the expected value, sigma ² Represents the variance of the noise, represents the conjugate;

s04, the receiving end calculates the signal to noise ratio of each channel, and the calculating method is as follows:

the channel weight is calculated by the following method:

wherein N is the number of transmitting antennas, M is the number of receiving antennas;

s05, the receiving end receives the signal Y at will _j The receiving end decodes the transmitted signal, and the decoding method is as follows:

wherein,is->Hermitian transpose of +.>For transmitting end signal estimation value, Y _j Representing the real signal received by the j-th antenna of the receiving end.

Further, the variance sigma of the noise ² The calculation method of (1) is as follows:

setting a silence period, during which the transmitting end does not transmit any signal;

the receiving end receives the signal r in the silence period _j (t) and calculating the quiet-period power, i.e., the variance σ of the noise ² The calculation method is as follows:

further, in the step S01, training is performed for each frequency, and training sequences used in each training are orthogonal in time.

Further, training sequences that are mutually orthogonal in time are generated by:

set training sequence x _i Is an n-dimensional vector;

training sequence x _i Orthogonalization is carried out by the method of orthogonalization of x _i Multiplied by the ith column of the Hadamard matrix of 2n×2n.

Further, the frequency of the training sequence covers the communication spectrum range of the coal mine roadway.

The beneficial effects of the invention are as follows: in contrast to the prior art, the method has the advantages that,

1) The invention can identify and compensate the time delay caused by the multipath effect by estimating the channel response, and the system can estimate the real arrival time of the signal more accurately, thereby solving the problem of reduced accuracy of UWB positioning caused by the multipath effect in long and narrow space;

2) According to the invention, a plurality of antennas or a plurality of frequencies are used, so that an observation channel can be increased, and thus, the channel response information is obtained more comprehensively, the accuracy of signal estimation is improved, and the positioning accuracy is improved;

3) The invention cooperates with a plurality of transmitting antennas and receiving antennas, and each antenna can be under different signal attenuation and multipath interference conditions. By using multiple antennas, the system can collect information from multiple independent channels. Even if some antennas encounter poor channel conditions, others may have better conditions. This diversity can significantly reduce the error rate due to multipath fading or other channel effects.

4) The method can adapt to the change of the wireless signal condition in the environment along with time and space in real time through the matching of the plurality of transmitting antennas and the receiving antennas and the dynamic weight distribution, so that the best performance is maintained under various conditions. For example, if the quality of a certain channel suddenly drops (possibly due to physical obstructions or other sources of interference), the method will automatically reduce the dependence on that channel, which in turn relies on other better quality channels.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings of the present specification.

Example 1: as shown in fig. 1, a method for resisting multipath interference in a coal mine underground long and narrow space based on channel estimation is provided, and the method comprises the following steps:

s01, selecting electromagnetic waves with the same frequency and amplitude from roadway communication electromagnetic waves as training sequences;

s02, the transmitting end transmits training sequences through a plurality of transmitting antennas, and x is the number of the transmitting antennas _i Representing a training sequence transmitted by an ith antenna;

s03, the receiving end receives signals through a plurality of receiving antennas, y _j Representing the signal received by the jth antenna;

the receiving end receives the signal y _j And training sequence x _i The difference between them to estimate the channel responseThe estimation method is as follows:

wherein E is defined as E.]Representing the expected value, sigma ² Represents the variance of the noise, represents the conjugate;

s04, the receiving end calculates the signal to noise ratio of each channel, and the calculating method is as follows:

the channel weight is calculated by the following method:

wherein N is the number of transmitting antennas, M is the number of receiving antennas;

s05, the receiving end receives the signal Y at will _j The receiving end decodes the transmitted signal, and the decoding method is as follows:

wherein,is->Hermitian transpose of +.>For transmitting end signal estimation value, Y _j Representing the real signal received by the j-th antenna of the receiving end.

First, consider a signal transmission model:

y _j ＝H _ij x _i +μ _j

wherein x is _i Is the training sequence transmitted by the ith transmitting antenna, y _j The j-th receiving antenna receives the signal H _ij Is the true channel response, mu, of the ith transmit antenna to the jth receive antenna _j Is the noise on the j-th receive antenna.

Our goal is to estimate H _ij Estimate of (2)To get->We can use the following method:

first calculate

Then calculate

UnfoldingIs (are) desirable to be (are)>

For a pair ofDeriving, can find the minimization +.>Is>The value of the sum of the values,

further, the variance sigma of the noise ² The calculation method of (1) is as follows:

setting a silence period, during which the transmitting end does not transmit any signal;

the receiving end receives the signal r in the silence period _j (t) and calculating the quiet-period power, i.e., the variance σ of the noise ² The calculation method is as follows:

further, in the step S01, training is performed for each frequency, and training sequences used in each training are orthogonal in time.

Further, training sequences that are mutually orthogonal in time are generated by:

set training sequence x _i Is an n-dimensional vector;

training sequence x _i Orthogonalization is carried out by the method of orthogonalization of x _i Multiplied by the ith column of the Hadamard matrix of 2n×2n.

Further, the frequency of the training sequence covers the communication spectrum range of the coal mine roadway.

The present invention is not described in detail in the present application, and is well known to those skilled in the art. Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered by the scope of the claims of the present invention.

Claims (5)

1. The method for resisting multipath interference in the underground long and narrow space of the coal mine based on the channel estimation is characterized by comprising the following steps:

s01, selecting electromagnetic waves with the same frequency and amplitude from roadway communication electromagnetic waves as training sequences;

s02, the transmitting end transmits training sequences through a plurality of transmitting antennas, and x is the number of the transmitting antennas _i Representing a training sequence transmitted by an ith antenna;

s03, the receiving end receives signals through a plurality of receiving antennas, y _j Representing the signal received by the jth antenna;

the receiving end receives the signal y _j And training sequence x _i The difference between them to estimate the channel responseThe estimation method is as follows:

wherein E [. Cndot.]Representing the expected value, sigma ² Represents the variance of the noise, represents the conjugate;

s04, the receiving end calculates the signal to noise ratio of each channel, and the calculating method is as follows:

the channel weight is calculated by the following method:

wherein N is the number of transmitting antennas, M is the number of receiving antennas;

s05, the receiving end receives the signal Y at will _j The receiving end decodes the transmitted signal, and the decoding method is as follows:

wherein,is->Hermitian transpose of +.>For transmitting end signal estimation value, Y _j Representing the real signal received by the j-th antenna of the receiving end.

2. The channel estimation based method for multipath interference resistance in a coal mine underground elongated space of claim 1, wherein the variance σ of the noise ² The calculation method of (1) is as follows:

setting a silence period, during which the transmitting end does not transmit any signal;

the receiving end receives the signal r in the silence period _j (t) and calculating the quiet-period power, i.e., the variance σ of the noise ² The calculation method is as follows:

3. the method for resisting multipath interference in a coal mine underground long and narrow space based on channel estimation according to claim 1, wherein in the step S01, training is performed for each frequency, and training sequences used in each training are orthogonal in time.

4. The method for resisting multipath interference in a coal mine underground long and narrow space based on channel estimation according to claim 1, wherein the training sequences which are mutually orthogonal in time are generated by the following method:

set training sequence x _i Is an n-dimensional vector;

training sequence x _i Orthogonalization is carried out by the method of orthogonalization of x _i Multiplied by the ith column of the Hadamard matrix of 2n×2n.

5. The channel estimation based method for multipath interference resistance in a coal mine underground long and narrow space according to claim 1, wherein the frequency of the training sequence covers the communication spectrum range of the coal mine tunnel.