CN102421189A - Method and device for realizing wireless network indoor positioning based on physical layer - Google Patents

Abstract

The embodiment of the invention discloses a method and a device for realizing wireless network indoor positioning based on a physical layer, wherein the method comprises the following steps: the method comprises the steps that channel state information of a plurality of subcarriers of a target node is obtained on the basis of an orthogonal frequency division multiplexing platform of a physical layer; calculating signal strength according to the channel state information of the plurality of subcarriers; optimizing a propagation path loss model of the indoor environment according to the signal intensity; calculating the distance between each sender and each receiver according to the optimized propagation path loss model; and positioning the target node according to the signal strength and the distance. In the embodiment of the invention, under the condition that the indoor environment multipath effect generally exists, the signal intensity is calculated by using the accurate channel state information in the wireless local area network so as to carry out indoor positioning, the frequency diversity of the channel state information is used for reducing the multipath attenuation, the influence of the indoor environment multipath effect and the frequency selective attenuation is reduced, the position information of the target node can be calculated more accurately, and the positioning precision is improved.

Description

A method and device for realizing wireless network indoor positioning based on physical layer

technical field

The present invention relates to the technical field of wireless communication, in particular to a physical layer-based wireless network indoor positioning method and device thereof. the

Background technique

With the rapid development of communication technology and wireless network, people's demand for wireless indoor positioning is increasing day by day. In order to provide users with various services based on location information, indoor location, as a hotspot of location technology research, has attracted more and more attention. Wireless Local Area Networks (WLAN) is a widely deployed new information acquisition platform. As a technology for indoor positioning, its high-density and low-cost characteristics are particularly competitive. However, due to the complexity of the indoor environment, indoor localization technology faces major challenges. How to eliminate this effect, so as to improve the positioning performance of WLAN indoors becomes a problem. the

Most of the current wireless indoor positioning technologies calculate the position of the target point based on the relationship between the received signal strength and the distance in the radio frequency signal propagation loss model in an open environment. As a general radio receiver technical index, the received signal strength indication (Received Signal Strength Indication, RSSI) value is a measurement of the strength of the radio frequency signal at the receiving end, indicating the power of the receiving end antenna. The larger the RSSI value, the stronger the signal, and vice versa, the weaker the signal. In theory, the radio frequency signal propagates along a single line-of-sight path from the transmitting source to the receiving end, and as the distance increases, the signal strength at the receiving end will decrease accordingly. However, in the real complex indoor environment, there are often various obstacles (ceiling, floor and wall, etc.) The so-called multipath effect. Under this effect, the RF signals propagating along various different reflection paths overlap or cancel each other at the receiving end, so that the received signal strength no longer satisfies the signal propagation loss model. In other words, the method of calculating the distance between the transmitting source and the receiving end based on the received signal strength according to the radio frequency signal propagation model will have the effect of inaccurate positioning. Therefore, it is not reliable to use the received signal strength indicator value (RSSI value) to calculate the signal strength. the

The existing wireless network positioning technology based on the received signal strength indication (RSSI) value is as follows: RADAR is the first indoor positioning system that proposes the application of the received signal strength indication (RSSI) value of the wireless local area network. It deploys a standard 802.11 network adapter to measure the radio signal strength at multiple base stations, and adopts the KNN algorithm to process the experimental data of the signal strength measurement of the access point in the offline phase. In addition, it builds a signal propagation model taking into account both wall attenuation factor (WAF) and ground attenuation factor (FAF), and RADAR has an accuracy of 3 meters; Horus applies a probabilistic algorithm to determine the target position with high accuracy (0.6 meters). The other is to design an indoor positioning system that regularly measures RSSI values online to mitigate the adverse effects of multipath fading and physical environment changes. The system has good adaptability to environmental fluctuations and keeps the positioning error within 3 meters. the

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art. The present invention provides a physical layer-based wireless network indoor positioning method and its device, which can effectively reduce the influence of multipath in the indoor environment, improve positioning accuracy and reduce cost. the

In order to solve the above-mentioned problems, the present invention proposes a method for realizing indoor positioning of a wireless network based on a physical layer, the method comprising:

The physical layer-based OFDM platform obtains the channel state information of multiple subcarriers of the target node;

Calculating signal strength according to the channel state information of the plurality of subcarriers;

Optimizing the propagation path loss model of the indoor environment according to the signal strength;

Calculate the distance between each sender and receiver according to the optimized propagation path loss model;

The target node is located according to the signal strength and the distance. the

Preferably, the step of calculating signal strength according to the channel state information of the multiple subcarriers includes:

Optimizing the channel state information through an inverse fast Fourier transform of OFDM and obtaining optimized subcarrier channel state information;

Calculate signal strength according to the optimized subcarrier channel state information. the

Preferably, the step of optimizing the channel state information through the inverse fast Fourier transform of OFDM and obtaining the optimized subcarrier channel state information includes:

Perform inverse fast Fourier transform on the channel state information of multiple subcarriers in the frequency domain to obtain the channel response in the time domain;

Filtering the multipath signals distinguished from the time domain and obtaining the line-of-sight of the multipath signals;

Obtain optimized sub-carrier channel state information according to the channel response and the line-of-sight of the multipath signal. the

Preferably, the step of optimizing the propagation path loss model of the indoor environment according to the signal strength includes:

Obtain the correspondence between the optimized subcarrier channel state information and the distance;

The propagation path loss model of the indoor environment is optimized according to the corresponding relationship. the

Preferably, the step of locating the target node according to the signal strength and the distance includes: locating the target node through a three-point positioning method according to the signal strength and the distance. the

Preferably, the number of channel state information of the plurality of subcarriers is 30. the

Preferably, the manner of calculating the signal strength according to the channel state information of the multiple subcarriers is to calculate the signal strength through the frequency diversity of the channel state information of the multiple subcarriers. the

Correspondingly, the embodiment of the present invention also provides a physical layer-based wireless network indoor positioning implementation device, the device includes:

The obtaining module is used to obtain the channel state information of multiple subcarriers of the target node based on the OFDM platform of the physical layer;

A signal strength calculation module, configured to calculate signal strength according to the channel state information of multiple subcarriers acquired by the acquisition module;

An optimization module, for optimizing the propagation path loss model of the indoor environment according to the signal strength calculated by the signal strength calculation module;

A distance calculation module, configured to calculate the distance between each sender and receiver according to the optimized propagation path loss model of the optimization module;

A positioning module, configured to locate the target node according to the signal strength calculated by the signal strength calculation module and the distance calculated by the distance calculation module. the

Preferably, the signal strength calculation module is also used to optimize the channel state information through OFDM inverse fast Fourier transform and obtain optimized subcarrier channel state information; and according to the optimized subcarrier channel state information Calculate signal strength. the

Preferably, the positioning module is used to locate the target node by a three-point positioning method according to the signal strength and the distance. the

In the embodiment of the present invention, in the case of the ubiquitous multipath effect in the indoor environment, accurate channel state information is used in the wireless local area network to calculate the signal strength and then perform indoor positioning, and the frequency diversity of the channel state information is used to reduce Multipath attenuation, reducing the impact of typical indoor environment multipath effects and frequency selective attenuation, can more accurately calculate the location information of the target node, and improve the positioning accuracy. the

Description of drawings

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 that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work. the

Fig. 1 is a schematic diagram of transmission of subcarrier channel state information of an embodiment of the present invention;

Fig. 2 is the schematic diagram of the positioning realization process of the present invention;

Fig. 3 is a schematic flow diagram of the implementation method of the wireless network indoor positioning based on the physical layer according to the embodiment of the present invention;

Fig. 4 is the schematic diagram of the diversity of subcarrier channel state information of the embodiment of the present invention;

Fig. 5 is a schematic diagram of eliminating time-domain multipath effects in an embodiment of the present invention;

Fig. 6 is the structural composition schematic diagram of the intelligent gateway of the embodiment of the present invention;

Fig. 7 is a schematic diagram of collecting subcarrier channel state information according to an embodiment of the present invention;

FIG. 8 is a schematic structural composition diagram of an apparatus for realizing indoor positioning of a wireless network based on a physical layer according to an embodiment of the present invention. the

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. the

The implementation principle of the embodiment of the present invention will be introduced in detail below. At present, most wireless local area networks adopt IEEE 802.11a/g/n standards to provide wireless communication services. These standards are based on Orthogonal Frequency Division Multiplexing (OFDM) at the physical layer. It is called a sub-carrier, which converts high-speed data signals into parallel low-speed sub-data streams, and modulates them for transmission on each sub-carrier. This enables the channel state information (Channel State Information, CSI) of several subcarriers to be acquired at the receiver at the same time, as shown in FIG. 1 . CSI is channel state information representing channel characteristics of a communication link. CSI describes and reflects the propagation state of radio frequency signals from the transmitting source to the receiving end, such as scattering, reflection and attenuation. The channel state information on the sub-carriers can reflect the signal strength of each different frequency. Different from the traditional way of obtaining the average value of the signal strength of each frequency from one packet, in the embodiment of the present invention, a more refined signal strength indication can be obtained. the

The concrete implementation principle of the present invention is mainly: first, analyze in detail from the physical layer of the wireless network the reasons that cause the received signal strength indication (RSSI) value to be inaccurate, including reflection attenuation and multipath effects of signals in complex indoor environments, thereby further seeking More accurate channel information to re-evaluate the signal strength; secondly, calculate the signal strength based on the finer channel state information of the physical layer, improve the propagation path loss model of the indoor environment, and calculate the distance according to the model. Refer to FIG. 2 for the positioning realization process of the present invention. the

Fig. 3 is a schematic flow diagram of a method for implementing a physical layer-based wireless network indoor positioning according to an embodiment of the present invention. As shown in Fig. 3, the method includes:

S301, obtaining channel state information of multiple subcarriers of the target node based on the physical layer-based OFDM platform;

S302, calculate the signal strength according to the channel state information of multiple subcarriers;

S303, optimizing the propagation path loss model of the indoor environment according to the signal strength;

S304, calculate the distance between each sender and receiver according to the optimized propagation path loss model;

S305. Locate the target node according to the signal strength and distance. the

Further, S302 includes:

The channel state information is optimized through the inverse fast Fourier transform of OFDM and the optimized sub-carrier channel state information is obtained; the signal strength is calculated according to the optimized sub-carrier channel state information. the

In the specific implementation, the steps of optimizing the channel state information and obtaining the optimized subcarrier channel state information through the inverse fast Fourier transform of OFDM include:

The channel state information of multiple subcarriers in the frequency domain is inversely transformed by fast Fourier to obtain the channel response in the time domain; the multipath signal distinguished from the time domain is filtered and the line-of-sight of the multipath signal is obtained; according to the channel Response and line-of-sight of multipath signals obtain optimized sub-carrier channel state information. the

Fig. 4 shows a schematic diagram of the diversity of sub-carrier channel state information according to an embodiment of the present invention. Fig. 4 describes the diversity of sub-carrier channel information. The receiving power is different, and the frequency diversity can be used to reduce small-scale fading (Small-scale fading). In a specific implementation, the frequency may be used as a weight to the amplitude of each subcarrier, and the square of the weighted average value may be calculated, that is, the received power may be obtained. S302 of the method will be further described below with reference to FIG. 4 . the

During the transmission of OFDM system data packets, the demodulated signal will be directly output to the decoder for further processing. By modifying the system kernel, a low-cost commercial wireless network card is used to obtain the channel state information of each subcarrier after demodulation, so as to calculate the corresponding signal strength. Aiming at the frequency diversity of carrier signal state information, the corresponding filtering method is combined in OFDM inverse fast Fourier transform (IFFT) processing to obtain more effective subcarrier channel state information (Effective CSI). The specific process is as follows: (1) The channel response in the time domain is obtained by inverse Fourier transforming the channel state information (channel response) of several subcarriers in the frequency domain; (2) Since the channel width of 802.11 is relatively wide, it can Part of the multipath signal is distinguished from the time domain, and through filtering processing, the influence of the multipath effect can be reduced, thereby improving the positioning accuracy. A schematic diagram of eliminating time-domain multipath effects in an embodiment of the present invention is shown in FIG. 5 . In a typical indoor environment, due to the ubiquity of multipath effects, the received signal is often a combination of line-of-sight and multipath reflections. In theory, when the bandwidth is larger than the coherence bandwidth, these reflections can be eliminated to obtain a line of sight. The bandwidth of 802.11n satisfies this limited requirement, so it can achieve the effect of eliminating the influence of multipath. the

In specific implementation, S303 further includes:

Obtain the corresponding relationship between the optimized sub-carrier channel state information and the distance; optimize the propagation path loss model of the indoor environment according to the corresponding relationship. the

The optimized channel state information is used as input, and the environment coefficient and path loss coefficient in different environments are trained according to the designed algorithm to further obtain the corresponding relationship between the optimized channel state information and the distance, so as to improve the indoor environment The following signal propagation path loss model. Since the environmental coefficient and the path loss coefficient are consistent in a specific environment, only one training process is required for different indoor environments, and multiple verifications are repeated using different distances to ensure the correctness of the improved model. In addition, the training process of environmental coefficients and path loss coefficients is completed online, and the expected training time will be limited to an acceptable time slice. Therefore, it is necessary to build experimental platforms for different environments, design algorithms to continuously measure and process path loss parameters, and correct the signal propagation model in real time. the

In specific implementation, S305 is: locating the target node by using a three-point locating method according to the signal strength and distance. the

Based on the effective relationship between channel state information and distance and the revised wireless signal propagation model, a new wireless local area network indoor positioning system is designed. The positioning system consists of two parts: a sender composed of multiple wireless access points and a receiver composed of target nodes to be positioned. On the sending side, the wireless access point sends the location information from the network layer to the target node through transmission signals. The widespread existence of wireless access points can easily and quickly obtain the location information of multiple wireless network access points. On the receiving side, the channel state information of subcarriers can be obtained from the physical layer, and the distances from each sending party to the receiving party can be calculated according to the improved signal propagation path loss model, and the target node can be positioned using a simple and effective three-point positioning method . As shown in Figure 6, it is assumed in Figure 6 that the coordinates of the three senders are A(x1, y1), B(x2, y2), and C(x3, y3), and the coordinate of the receiver O to be located is O(x , y), and the distances from this point to the three coordinate points of the sender are known as d1, d2, and d3 respectively, then the coordinates of point O can be calculated by the trilateration method, that is, the location information of the receiver can be obtained. the

In a specific implementation, the receiver can be equipped with an 802.11n wireless network card, which can obtain channel state information of 30 subcarriers at the same time. the

In the embodiment of the present invention, when the multipath effect in the indoor environment is ubiquitous, accurate channel state information is used in the wireless local area network to calculate the signal strength and then perform indoor positioning, and the frequency diversity of the channel state information is used to reduce multipath Attenuation, reducing the impact of multipath effects and frequency selective attenuation in typical indoor environments, can more accurately calculate the location information of target nodes, and improve positioning accuracy. the

In addition, FIG. 7 shows a schematic diagram of collecting subcarrier channel state information according to an embodiment of the present invention. As shown in FIG. 7 , relying on the hardware of the wireless network card and modifying the network card driver of the operating system, the channel state information can be collected and passed through the API Channel state information is provided to the user. the

Fig. 8 is a schematic diagram of the structural composition of a device for realizing indoor positioning of a wireless network based on a physical layer according to an embodiment of the present invention. As shown in Fig. 8, the device includes:

Obtaining module 80, for obtaining the channel state information of multiple subcarriers of the target node based on the OFDM platform of the physical layer;

The signal strength calculation module 81 is used to calculate the signal strength according to the channel state information of multiple subcarriers acquired by the acquisition module 80;

An optimization module 82, configured to optimize the propagation path loss model of the indoor environment according to the signal strength calculated by the signal strength calculation module 81;

The distance calculation module 83 is used to calculate the distance between each sender and the receiver according to the optimized propagation path loss model of the optimization module 82;

The positioning module 84 is configured to locate the target node according to the signal strength calculated by the signal strength calculation module 81 and the distance calculated by the distance calculation module 83 . the

Further, the signal strength calculation module 81 is also used to optimize the channel state information through the inverse fast Fourier transform of OFDM and obtain the optimized subcarrier channel state information; and calculate the signal strength according to the optimized subcarrier channel state information. the

Further, the positioning module 84 is configured to locate the target node by using a three-point positioning method according to signal strength and distance. the

For the implementation process and principle of each module function of the implementation of the physical layer-based wireless network indoor positioning in the device embodiment of the present invention, please refer to the corresponding process in the embodiment of the physical layer-based wireless network indoor positioning implementation method of the present invention description, and will not be repeated here. the

In the embodiment of the device of the present invention, when the multipath effect in the indoor environment is ubiquitous, the accurate channel state information is used to calculate the signal strength in the wireless local area network and then perform indoor positioning, and the frequency diversity of the channel state information is used to reduce the number of Path attenuation, reducing the impact of multipath effects and frequency selective attenuation in typical indoor environments, can more accurately calculate the location information of target nodes, and improve positioning accuracy. the

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage medium can include: Read Only Memory (ROM, Read Only Memory), Random Access Memory (RAM, Random Access Memory), disk or CD, etc. the

In addition, the method and device for realizing the indoor positioning of the wireless network based on the physical layer provided by the embodiments of the present invention are introduced in detail above. In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The above embodiments The description is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and scope of application. In summary, As stated above, the content of this specification should not be construed as limiting the present invention. the

Claims (10)

1. implementation method based on the wireless network indoor positioning of physical layer is characterized in that said method comprises:

Obtain the channel condition information of a plurality of subcarriers of destination node based on the OFDM platform of physical layer;

Channel condition information signal calculated intensity according to said a plurality of subcarriers;

Propagation path loss model according to said signal strength optimization indoor environment;

According to each transmit leg of propagation path loss Model Calculation after optimizing and recipient's distance;

According to said signal strength signal intensity and said distance said destination node is positioned.

2. the implementation method of the wireless network indoor positioning based on physical layer as claimed in claim 1 is characterized in that, the step of said channel condition information signal calculated intensity according to said a plurality of subcarriers comprises:

Sub-carrier channels state information after invert fast fourier transformation through OFDM is optimized and obtains to optimize to said channel condition information;

According to the sub-carrier channels state information signal calculated intensity after the said optimization.

3. the implementation method of the wireless network indoor positioning based on physical layer as claimed in claim 2; It is characterized in that the step of the sub-carrier channels state information after said invert fast fourier transformation through OFDM is optimized and obtains to optimize to said channel condition information comprises:

The channel condition information of a plurality of subcarriers on the frequency domain is carried out invert fast fourier transformation to obtain the channel response on the time domain;

The multipath signal of distinguishing from time domain is carried out Filtering Processing and obtains the straight line sighting distance of said multipath signal;

According to the sub-carrier channels state information after the straight line sighting distance acquisition optimization of said channel response and said multipath signal.

4. the implementation method of the wireless network indoor positioning based on physical layer as claimed in claim 3 is characterized in that, the step of said propagation path loss model according to said signal strength optimization indoor environment comprises:

Obtain sub-carrier channels state information and the corresponding relation between the distance after the said optimization;

Be optimized according to the propagation path loss model of said corresponding relation indoor environment.

5. the implementation method of the wireless network indoor positioning based on physical layer as claimed in claim 1 is characterized in that, saidly according to said signal strength signal intensity and said distance to the step that said destination node positions is:

Said destination node is positioned through three-point positioning method according to said signal strength signal intensity and said distance.

6. the implementation method of the wireless network indoor positioning based on physical layer as claimed in claim 1 is characterized in that the quantity of the channel condition information of said a plurality of subcarriers is 30.

7. according to claim 1 or claim 2 implementation method based on the wireless network indoor positioning of physical layer; It is characterized in that the mode of said channel condition information signal calculated intensity according to said a plurality of subcarriers is the frequency diversity signal calculated intensity through the channel condition information of said a plurality of subcarriers.

8. implement device based on the wireless network indoor positioning of physical layer is characterized in that said device comprises:

Acquisition module is used for obtaining based on the OFDM platform of physical layer the channel condition information of a plurality of subcarriers of destination node;

Signal strength signal intensity is calculated module, the channel condition information signal calculated intensity of a plurality of subcarriers that are used for obtaining according to said acquisition module;

Optimal module is used for calculating according to said signal strength signal intensity the propagation path loss model of the signal strength optimization indoor environment that module calculates;

Distance calculation module, each transmit leg of propagation path loss Model Calculation after being used for optimizing and recipient's distance according to said optimal module;

Locating module is used for according to signal strength signal intensity and said distance calculation module institute calculated distance that said signal strength signal intensity calculating module is calculated said destination node being positioned.

9. the implement device of the wireless network indoor positioning based on physical layer as claimed in claim 8; It is characterized in that the sub-carrier channels state information after said signal strength signal intensity is calculated module and also is used for invert fast fourier transformation through OFDM said channel condition information is optimized and obtains to optimize; And according to the sub-carrier channels state information signal calculated intensity after the said optimization.

10. the implement device of the wireless network indoor positioning based on physical layer as claimed in claim 8 is characterized in that said locating module is used for said destination node being positioned through three-point positioning method according to said signal strength signal intensity and said distance.

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