Complex indoor environment channel modeling method and device in wireless body area network

Abstract

The present invention discloses a method and device for modeling a complex indoor environment channel in a wireless body area network. The method comprises: (1) selecting a reference distance d0 between a transmitting and receiving antenna, obtaining a human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx (2) establish a channel average path loss model; (3) collect path loss measurement values ​​at different test points d and p in the X-band; (4) fit the data obtained in step (3) to the model established in step (2), and substitute the parameters obtained by fitting into the model in step (2), which is the indoor environment channel model. The channel model established by the present invention is more accurate.

Description

Technical Field

[0001] The present invention relates to wireless communication technology, and in particular to a complex indoor environment channel modeling method and device in a wireless body area network. Background Art

[0002] In recent years, wireless body area network (WBAN) has been the focus of research in the field of communications. The deployment requirements of WBAN in complex environments such as smart cities, plant activity monitoring, and power inspection operations have further driven the development of wearable devices. In the future, the number of terminals and network data in a small area will surge, and the existing channel model will no longer be applicable. Therefore, it is necessary to accurately model the wireless body area network in complex environments. In order to meet the high-speed data transmission of wearable device terminals in the future, it is necessary to establish an accurate body area network channel model as much as possible. However, there is no generally accepted general conclusion in this regard. For example, in the relationship between the penetration loss of the human body and the frequency or distance, some existing literature often has different measurement results, and even draws contradictory conclusions.

[0003] The paper "Research Progress on Body Surface Channel Models for Wireless Body Area Networks" summarizes and briefly introduces the current off-body channel modeling, including single path loss model, hybrid path loss model, small-scale fading, etc. The research frequency bands are low frequency band, 2.4GHz band, UWB (3.1~10.6)GHz ultra-wideband band, but the use of these frequency bands is prone to interference. The paper also discloses a single path loss model:

[0004]

[0005] PL0 represents the path loss at the reference distance d0, n is the loss exponent, and S is the shadow fading term.

[0006] However, the biggest problem with this model is that it does not take into account the occlusion loss caused by the human body. The actual path loss in the non-line-of-sight link will far exceed the loss budget of this model. Secondly, this model can only regard the human body as a whole and cannot make detailed path loss models for different parts of the body surface. The accuracy is not high enough and it cannot adapt well to the future complex body area network of multiple wearable devices. Summary of the invention

[0007] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a method and device for modeling complex indoor environment channels in a wireless body area network with higher accuracy.

[0008] Technical solution: The complex indoor environment channel modeling method in the wireless body area network of the present invention includes:

[0009] (1) Select the reference distance d0 between the transmitting and receiving antennas to obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh;

[0010] (2) The channel average path loss model is established as:

[0011]

[0012]

[0013]

[0014]

[0015] h Tx =a·h i +Δh

[0016] Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σ p,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, f hTx (h Tx ) represents the antenna height h Tx The impact on the average path loss, a p , b p 、c p d p f hTx (h Tx ) coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p , b p 、c p d p is the parameter to be fitted;

[0017] (3) Collect path loss measurements at different d and p test points in the X-band;

[0018] (4) Fitting the data obtained in step (3) to the model established in step (2), and substituting the fitted parameters into the model in step (2) to obtain the indoor environment channel model.

[0019] Furthermore, the method further comprises the steps of:

[0020] (5) According to the indoor environment channel model obtained by fitting, the path loss calculation value at different d and different p is calculated, and the determination coefficient is evaluated with the path loss measurement value. If the determination coefficient is greater than the preset threshold, it is determined that the current path loss measurement value is successfully fitted. Otherwise, return to steps (3) and (4) to re-measure and fit.

[0021] Furthermore, step (1) specifically includes:

[0022] (1-1) Select the reference distance d0 between the transmitting and receiving antennas according to the following rules:

[0023]

[0024] In the formula, D represents the diameter of the antenna, and λ represents the wavelength of the wireless carrier signal;

[0025] (1-2) Get the human height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

[0026] Furthermore, step (3) specifically includes:

[0027] (3-1) Set the value sequence of the distance d between the transmitting and receiving antennas {d1, d2, …, d Nd}, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np}, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p;

[0028] (3-2) Assume that the distance d between the transmitting and receiving antennas is d1, the part of the human body where the transmitting antenna is located is p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf}, the current receiving antenna position is divided into an H*H spatial grid array, the grid spacing is half the wavelength of the wireless carrier signal, and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data

[0029]

[0030] In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band.

[0031] (3-3) According to step (3-2), d is traversed through the value sequence {d1, d2, …, d Nd}, p respectively traverse the value sequence {p1,p2,…,p Np}, thus obtaining the path loss measurement values ​​for different d and different p.

[0032] Furthermore, step (5) specifically includes:

[0033] (5-1) According to the fitted indoor environment channel model, calculate the path loss value y(d,p) for different d and different p;

[0034] (5-2) Select N path loss measurement values ​​with different d and p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 :

[0035]

[0036]

[0037] (5-3) Determine whether the determination coefficient is greater than a preset threshold. If so, it is determined that the current path loss measurement value is successfully fitted. Otherwise, return to steps (3) and (4) to re-measure and re-fit.

[0038] The complex indoor environment channel modeling device in the wireless body area network of the present invention comprises:

[0039] The parameter selection module is used to select the reference distance d0 between the transmitting and receiving antennas and obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh;

[0040] The model building module is used to build the channel average path loss model as follows:

[0041]

[0042]

[0043]

[0044]

[0045] hTx =a·h i +Δh

[0046] Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σ p,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, Indicates the antenna height h Tx The impact on the average path loss, a p , b p 、c p d p f hTx (h Tx ) coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p , b p 、c p d p is the parameter to be fitted;

[0047] A data acquisition module is used to collect path loss measurement values ​​at different d and p of the test point in the X-band;

[0048] The simulation fitting module is used to fit the data obtained by the data acquisition module to the model established by the model establishment module, and substitute the parameters obtained by fitting into the established model, which is the indoor environment channel model.

[0049] Furthermore, it also includes:

[0050] The evaluation module is used to calculate the path loss calculation value at different d and different p according to the indoor environment channel model obtained by fitting, and evaluate the determination coefficient with the path loss measurement value. If the determination coefficient is greater than the preset threshold, it is determined that the current path loss measurement value is fitted successfully, otherwise it is re-measured and fitted.

[0051] Furthermore, the parameter selection module specifically includes:

[0052] The reference distance selection unit is used to select the reference distance d0 between the transmitting and receiving antennas according to the following rules:

[0053]

[0054] In the formula, D represents the diameter of the antenna, and λ represents the wavelength of the wireless carrier signal;

[0055] Antenna height difference acquisition unit, used to obtain human height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

[0056] Furthermore, the data acquisition module specifically includes:

[0057] A value sequence setting unit is used to set the value sequence {d1, d2, ..., d Nd}, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np}, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p;

[0058] The data measurement unit is used to set the distance d between the transmitting and receiving antennas as d1, the part of the human body where the transmitting antenna is located as p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf}, the current receiving antenna position is divided into an H*H spatial grid array, the grid spacing is half the wavelength of the wireless carrier signal, and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data

[0059]

[0060] In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band.

[0061] The traversal unit is used to traverse the value sequence {d1, d2, …, d Nd}, p respectively traverse the value sequence {p1,p2,…,p Np} and execute the data measurement unit to obtain the path loss measurement values ​​at different d and different p.

[0062] Furthermore, the evaluation module specifically includes:

[0063] The first calculation unit is used to calculate the path loss calculation value y(d,p) at different d and different p according to the indoor environment channel model obtained by fitting;

[0064] The second calculation unit is used to select N path loss measurement values ​​with different d and different p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 :

[0065]

[0066] The judging unit is used to judge whether the determination coefficient is greater than a preset threshold value. If so, it is determined that the current path loss measurement value is successfully fitted, otherwise, re-measurement and fitting are performed.

[0067] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: higher accuracy, and can accurately give the off-body channel loss value of each part of the human body. For link budgeting, it can accurately control the size of the channel power, while ensuring the transmission quality, reducing the transmission power as much as possible, and saving resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a flow chart of an embodiment of a complex indoor environment channel modeling method in a wireless body area network provided by the present invention. DETAILED DESCRIPTION

[0069] This embodiment provides a method for modeling complex indoor environment channels in a wireless body area network. Figure 1 As shown, including:

[0070] (1) Select the reference distance d0 between the transmitting and receiving antennas to obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

[0071] This step specifically includes:

[0072] (1-1) Select the reference distance d0 between the transmitting and receiving antennas according to the following rules:

[0073]

[0074] Where D is the diameter of the antenna and λ is the wavelength of the wireless carrier signal.

[0075] According to the antenna characteristics, far-field testing refers to directly measuring the far-field data of the antenna to be tested. In near-field antenna measurement, errors may be caused by multipath effects and external interference. Therefore, far-field data is often more reliable in measurement. Therefore, the selection rules are defined as follows: Here, a microstrip antenna is used as the wearable antenna of the present invention for measurement. The antenna size is small (maximum size 2.5 cm), so the theoretical minimum value of d0 is about 4.1667 cm. However, in actual situations, many factors such as the test subject's posture, body shape, unnecessary movements, etc. will cause errors. In this embodiment, d0=1m is selected.

[0076] (1-2) Get the human height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

[0077] The height of the abdomen of the human body is taken as the reference height of the receiving end. According to the differences of the human body, the height of the receiving end antenna h Rx As a person's height i Changes to: h Rx =a·h i , transmitting antenna height h Tx For: h Tx =h Rx +Δh, Δh is adjusted according to different wireless network physical channel configuration environments. When Δh is positive, it means that the transmitting antenna is above the abdomen, and when Δh is negative, it means that the transmitting antenna is below the abdomen. For the same human body model, h Rx It is a constant, so in the present invention, the fading index of the basic logarithmic distance model is affected by p of different parts of the human body; similarly, the measured values ​​of different parts of the human body change because the height of the receiving antenna changes, and the change of the propagation environment causes p to have an interrelated influence with the shadow effect and penetration loss.

[0078] (2) The channel average path loss model is established as:

[0079]

[0080]

[0081]

[0082]

[0083] h Tx =a·h i +Δh

[0084] Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σp,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, Indicates the antenna height h Tx The impact on the average path loss, a p , b p 、c p d p for The coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p , b p 、c p d p are the parameters to be fitted.

[0085] (3) Collect path loss measurement values ​​at different test points d and p in the X-band.

[0086] This step specifically includes:

[0087] (3-1) Set the value sequence of the distance d between the transmitting and receiving antennas {d1, d2, …, d Nd}, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np}, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p;

[0088] (3-2) Assume that the distance d between the transmitting and receiving antennas is d1, the part of the human body where the transmitting antenna is located is p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf}, the position of the current receiving antenna is divided into an H*H spatial grid array (3*3 in this embodiment), the grid spacing is half the wavelength of the wireless carrier signal (λ / 2), and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data

[0089]

[0090] In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band.

[0091] (3-3) According to step (3-2), d is traversed through the value sequence {d1, d2, …, d Nd}, p respectively traverse the value sequence {p1,p2,…,p Np}, thus obtaining the path loss measurement values ​​for different d and different p.

[0092] (4) Fitting the data obtained in step (3) to the model established in step (2), and substituting the fitted parameters into the model in step (2) to obtain the indoor environment channel model.

[0093] (5) According to the indoor environment channel model obtained by fitting, the path loss calculation value at different d and different p is calculated, and the determination coefficient is evaluated with the path loss measurement value. If the determination coefficient is greater than the preset threshold, it is determined that the current path loss measurement value is successfully fitted. Otherwise, return to steps (3) and (4) to re-measure and fit.

[0094] This step specifically includes:

[0095] (5-1) According to the fitted indoor environment channel model, calculate the path loss value y(d,p) for different d and different p;

[0096] (5-2) Select N path loss measurement values ​​with different d and p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 :

[0097]

[0098]

[0099] (5-3) Determine whether the determination coefficient is greater than a preset threshold. If so, it is determined that the current path loss measurement value is successfully fitted. Otherwise, return to steps (3) and (4) to re-measure and re-fit.

[0100] This embodiment also provides a complex indoor environment channel modeling device in a wireless body area network, including:

[0101] The parameter selection module is used to select the reference distance d0 between the transmitting and receiving antennas and obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh;

[0102] The model building module is used to build the channel average path loss model as follows:

[0103]

[0104]

[0105]

[0106]

[0107] h Tx =a·h i +Δh

[0108] Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σ p,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, Indicates the antenna height h Tx The impact on the average path loss, a p , b p 、c p d p for The coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p , b p 、c p d p is the parameter to be fitted;

[0109] A data acquisition module is used to collect path loss measurement values ​​at different d and p of the test point in the X-band;

[0110] A simulation fitting module is used to fit the data obtained by the data acquisition module to the model established by the model establishment module, and the parameters obtained by fitting are substituted into the established model, which is the indoor environment channel model;

[0111] The evaluation module is used to calculate the path loss calculation value at different d and different p according to the indoor environment channel model obtained by fitting, and evaluate the determination coefficient with the path loss measurement value. If the determination coefficient is greater than the preset threshold, it is determined that the current path loss measurement value is fitted successfully, otherwise it is re-measured and fitted.

[0112] The parameter selection module specifically includes:

[0113] The reference distance selection unit is used to select the reference distance d0 between the transmitting and receiving antennas according to the following rules:

[0114]

[0115] In the formula, D represents the diameter of the antenna, and λ represents the wavelength of the wireless carrier signal;

[0116] Antenna height difference acquisition unit, used to obtain the height h of the human body i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

[0117] Wherein, the data acquisition module specifically includes:

[0118] A value sequence setting unit is used to set the value sequence {d1, d2, ..., d Nd}, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np}, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p;

[0119] The data measurement unit is used to set the distance d between the transmitting and receiving antennas as d1, the part of the human body where the transmitting antenna is located as p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf}, the current receiving antenna position is divided into an H*H spatial grid array, the grid spacing is half the wavelength of the wireless carrier signal, and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data

[0120]

[0121] In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band.

[0122] The traversal unit is used to traverse the value sequence {d1, d2, …, d Nd}, p respectively traverse the value sequence {p1,p2,…,p Np} and execute the data measurement unit to obtain the path loss measurement values ​​at different d and different p.

[0123] Wherein, the evaluation module specifically includes:

[0124] The first calculation unit is used to calculate the path loss calculation value y(d,p) at different d and different p according to the indoor environment channel model obtained by fitting;

[0125] The second calculation unit is used to select N path loss measurement values ​​with different d and different p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 :

[0126]

[0127]

[0128] The judging unit is used to judge whether the determination coefficient is greater than a preset threshold value. If so, it is determined that the current path loss measurement value is successfully fitted, otherwise, re-measurement and fitting are performed.

[0129] This device corresponds to the above method one by one. Please refer to the method for any incomplete details and no further description will be given.

[0130] The above disclosure is only a preferred embodiment of the present invention, which cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for modeling complex indoor environment channels in a wireless body area network, characterized in that The method includes: (1) Select the reference distance d0 between the transmitting and receiving antennas to obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh; (2) The channel average path loss model is established as: h Tx =a·h i +Δh Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σ p,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, Indicates the antenna height h Tx The impact on the average path loss, a p 、b p 、c p ,d p for The coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p 、b p 、c p ,d p is the parameter to be fitted; (3) Collect path loss measurements at different d and p test points in the X-band; (4) fitting the data obtained in step (3) to the model established in step (2), and substituting the fitted parameters into the model in step (2) to obtain the indoor environment channel model; (5) According to the indoor environment channel model obtained by fitting, the path loss calculation value at different d and different p is calculated, and the determination coefficient is evaluated with the path loss measurement value. If the determination coefficient is greater than the preset threshold, it is determined that the current path loss measurement value is successfully fitted, otherwise, it returns to steps (3) and (4) to re-measure and fit; Wherein, step (3) specifically includes: (3-1) Set the value sequence of the distance d between the transmitting and receiving antennas {d1, d2, …, d Nd }, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np }, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p; (3-2) Assume that the distance d between the transmitting and receiving antennas is d1, the part of the human body where the transmitting antenna is located is p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf }, the current receiving antenna position is divided into an H*H spatial grid array, the grid spacing is half the wavelength of the wireless carrier signal, and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band. (3-3) According to step (3-2), d is traversed through the value sequence {d1, d2, …, d Nd }, p respectively traverse the value sequence {p1,p2,…,p Np }, thus obtaining the path loss measurement values ​​for different d and different p.

2. The complex indoor environment channel modeling method in a wireless body area network according to claim 1, characterized in that: Step (1) specifically includes: (1-1) Select the reference distance d0 between the transmitting and receiving antennas according to the following rules: In the formula, D represents the diameter of the antenna, and λ represents the wavelength of the wireless carrier signal; (1-2) Get the human height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

3. The complex indoor environment channel modeling method in a wireless body area network according to claim 1, characterized in that: Step (5) specifically includes: (5-1) According to the fitted indoor environment channel model, calculate the path loss value y(d,p) for different d and different p; (5-2) Select N path loss measurement values ​​with different d and p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 : (5-3) Determine whether the determination coefficient is greater than a preset threshold. If so, it is determined that the current path loss measurement value is successfully fitted. Otherwise, return to steps (3) and (4) to re-measure and re-fit.

4. A complex indoor environment channel modeling device in a wireless body area network, characterized in that include: The parameter selection module is used to select the reference distance d0 between the transmitting and receiving antennas and obtain the human body height h i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh; The model building module is used to build the channel average path loss model as follows: h Tx =a·h i +Δh Where d is the distance between the transmitting and receiving antennas, p is the part of the human body where the transmitting antenna is located, PL(d,p) is the average path loss, and β 0,p represents the intercept of the path loss model, n p represents the logarithmic fading index, BPAF(p) and ψ(p) represent the probability density distribution function of the shadow effect and penetration loss with p, respectively, and σ p,1 and μ p,1 is the variance and mean of the BPAF(p) distribution function, σ p,2 and μ p,2 is the variance and mean of the ψ(p) distribution function, Indicates the antenna height h Tx The impact on the average path loss, a p 、b p 、c p ,d p for The coefficient, a represents the proportion of the center of gravity of the human body, β 0,p 、n p , σ p,1 , μ p,1 , σ p,2 , μ p,2 、a p 、b p 、c p ,d p is the parameter to be fitted; A data acquisition module is used to collect path loss measurement values ​​at different d and p of the test point in the X-band; A simulation fitting module is used to fit the data obtained by the data acquisition module to the model established by the model establishment module, and the parameters obtained by fitting are substituted into the established model, which is the indoor environment channel model; An evaluation module is used to calculate the path loss calculation value at different d and different p according to the indoor environment channel model obtained by fitting, and to evaluate the determination coefficient with the path loss measurement value. If the determination coefficient is greater than a preset threshold, it is determined that the current path loss measurement value is successfully fitted, otherwise it is re-measured and fitted; Wherein, the data acquisition module specifically includes: A value sequence setting unit is used to set the value sequence {d1, d2, ..., d Nd }, the value sequence of the part of the human body where the transmitting antenna is located {p1,p2,…,p Np }, Nd represents the number of values ​​of d, and Np represents the number of values ​​of p; The data measurement unit is used to set the distance d between the transmitting and receiving antennas as d1, the part of the human body where the transmitting antenna is located as p1, and divide the sampled X frequency band into a frequency point sequence {f1, f2, …, f Nf }, the current receiving antenna position is divided into an H*H spatial grid array, the grid spacing is half the wavelength of the wireless carrier signal, and the frequency domain response amplitude of each grid is collected at each frequency point in the frequency point sequence. Each grid is collected M times, and the path loss measurement value is calculated according to the following formula based on the collected data In the formula, It refers to the frequency domain response attenuation ratio obtained by the jth measurement on the i-th grid when the distance is d, the body part p is p1, and the sampling frequency is f, that is, the energy attenuation ratio from the transmitter to the receiver. Nf represents the number of frequency points divided in the X-band. The traversal unit is used to traverse the value sequence {d1, d2, …, d Nd }, p respectively traverse the value sequence {p1,p2,…,p Np } and execute the data measurement unit to obtain the path loss measurement values ​​at different d and different p.

5. The complex indoor environment channel modeling device in a wireless body area network according to claim 4, characterized in that: The parameter selection module specifically includes: The reference distance selection unit is used to select the reference distance d0 between the transmitting and receiving antennas according to the following rules: In the formula, D represents the diameter of the antenna, and λ represents the wavelength of the wireless carrier signal; Antenna height difference acquisition unit, used to obtain the height h of the human body i and the transmitting antenna height h Tx and the receiving antenna height h Rx The difference Δh.

6. The complex indoor environment channel modeling device in a wireless body area network according to claim 4, characterized in that: The evaluation module specifically includes: The first calculation unit is used to calculate the path loss calculation value y(d, p) at different d and different p according to the indoor environment channel model obtained by fitting; The second calculation unit is used to select N path loss measurement values ​​with different d and different p and the calculated path loss value y(d,p), and calculate the determination coefficient R according to the following formula 2 : The judging unit is used to judge whether the determination coefficient is greater than a preset threshold value. If so, it is determined that the current path loss measurement value is successfully fitted, otherwise, re-measurement and fitting are performed.

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