CN113810138B - Multipath channel modeling method for dynamic on-body channel in wireless body area network - Google Patents
Multipath channel modeling method for dynamic on-body channel in wireless body area network Download PDFInfo
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Abstract
The invention belongs to the technical field of radio waves, and discloses a multipath channel modeling method of a dynamic on-body channel in a wireless body area network; setting up on-body channels under different polarization combinations for a human body model under each frame action and carrying out electromagnetic simulation; fitting according to the average power delay distribution to obtain a power attenuation index; obtaining the arrival time and path loss power of each independent path according to the multipath parameters; calculating the cross polarization discrimination rate of each path, and performing normal distribution fitting on probability distribution of the cross polarization discrimination rate to obtain the average value of normal distribution; performing normal distribution fitting on probability distribution of path loss of a first path of a channel under a plurality of frame actions to obtain standard deviation of normal distribution; analyzing probability distribution conditions obeyed by inter-path delay of the arrival time, and fitting an optimal probability distribution model; constructing channel impulse responses in a co-polarization mode and a cross-polarization mode; the invention can simply and efficiently establish an accurate multipath channel model.
Description
Technical Field
The invention belongs to the technical field of radio waves, and discloses a multipath channel modeling method for a dynamic on-body channel in a wireless body area network.
Background
The wireless body area network (Wireless Body Area Network, WBAN) is a small-range communication network centering on a human body and consists of a series of sensor network nodes distributed on the surface of the human body or around the body within a certain distance range or even inside the human body; the method has the advantages of automatic networking, low power consumption, dynamic network optimization, small volume and the like. The wireless body area network can be divided into on-body (on-body), off-body (body) and implanted (Implant in the body) according to the location of the transmitter (Tx) and receiver Rx) in the body-centric transmission. The current WBAN has very wide application and plays an important role in medical treatment, military, entertainment, sports and the like. Especially in medical treatment, key parameters related to human health are accurately presented to medical staff and patients in real time through sensor nodes arranged on human bodies, and the medical staff is helped to implement proper medical treatment means. Thus, research on transmission in vivo in WBAN is indispensable.
The human body serves as a propagation medium of loss and has a complex structure, and to effectively control energy of the WBAN system, propagation loss of electromagnetic waves on the human body needs to be estimated in detail. The WBAN channel, like the conventional radio channel, has four main propagation modes: direct waves, reflected waves, diffracted waves and surface creeping waves. The propagation of signals through the body is not direct but diffracts around the body, which complicates the channel environment and leads to multipath signal transmission and fluctuations in path loss. Furthermore, due to the random mobility of the human body, one or more parts of the body may move as the movement posture changes. Therefore, the multipath channel modeling of the dynamic body channel is of great significance for establishing a stable and reliable WBAN communication system.
Disclosure of Invention
Based on the problems existing in the prior art, the invention provides a multipath channel modeling method of a dynamic on-body channel in a wireless body area network, which can solve the problem of how to perform simulation experiments on the dynamic on-body channel and provides a calculation method of gains and arrival time of each path of the multipath channel. The multipath channel modeling method comprises the following steps:
setting up on-body channels under different polarization combinations for the human body model under each frame action, and carrying out electromagnetic simulation to obtain frequency domain transmission signals of the on-body channels;
determining the power delay distribution of a link through the frequency domain transmission signal, and fitting according to the average power delay distribution to obtain a power attenuation index;
extracting multipath parameters corresponding to the power delay distribution, and obtaining the arrival time and path loss power of each independent path according to the multipath parameters;
calculating the cross polarization discrimination rate of each path in the channel multipath under each frame action, and performing normal distribution fitting on probability distribution of the cross polarization discrimination rate to obtain the average value of a cross polarization discrimination rate distribution model;
performing normal distribution fitting on probability distribution of path loss of a first path of a channel under a plurality of frame actions to obtain standard deviation of a path loss distribution model of the first path;
statistically analyzing probability distribution conditions obeyed by inter-path delay of the arrival time of each path and the arrival time of the previous path respectively, and fitting an optimal inter-path delay probability distribution model;
constructing channel impulse response in a co-polarization mode according to the average path loss, arrival time, power attenuation index, path loss distribution model and parameters of the inter-path delay probability distribution model of the first path; and constructing the channel impulse response in the cross polarization mode by utilizing the parameters of the cross polarization discrimination distribution model based on the parameters of the channel impulse response in the co-polarization mode.
The invention has the beneficial effects that:
(1) The invention can simulate the channel on the dynamic body simply and efficiently by framing the continuous human body actions and carrying out electromagnetic simulation on the human body model under each frame of actions independently, and an accurate multipath channel model is established.
(2) The dynamic on-body multipath channel modeling method fully considers the power attenuation trend and the inter-path delay of the multipath channel, and ensures the accuracy of the established model.
Drawings
Fig. 1 is a flowchart of a method for modeling multipath channels of a dynamic on-body channel in a wireless body area network according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for modeling multipath channels of a dynamic on-body channel in a wireless body area network according to a preferred embodiment of the present invention;
FIG. 3 is a 15 frame map of a walk provided by an embodiment of the present invention;
fig. 4 is a schematic diagram of an antenna placement direction according to an embodiment of the present invention;
fig. 5 is a schematic diagram showing placement positions of the waist-chest channels Rx and Tx in the VV polarization combination mode according to the embodiment of the present invention;
FIG. 6 is a normalized PDP plot of waist-chest channels for 15 different models provided by an embodiment of the present invention;
FIG. 7 is a graph of APDP versus log fit for a waist-chest channel for 15 different models provided by an embodiment of the invention;
FIG. 8 is an illustration of an X of various paths of a waist-chest channel provided by an embodiment of the invention VV-VH Fitting a map to the probability distribution and normal distribution of (2);
fig. 9 is a normal distribution fit of the path loss of the first path of the waist-chest channel provided by an embodiment of the present invention;
fig. 10 is an exemplary diagram of an impulse response model in VV co-polarization mode of a generated waist-chest channel according to an embodiment of the present invention;
fig. 11 is an exemplary diagram of an impulse response model in VH cross-polarization mode of a generated waist-chest channel according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention considers the influence of the transformation of the human body movement posture on the on-body channel, and provides a multipath channel modeling method aiming at the dynamic on-body channel in the wireless body area network, which better reflects the variation characteristic of the channel in the human body movement state.
Fig. 1 is a flowchart of a method for modeling multipath channels of a dynamic on-body channel in a wireless body area network according to an embodiment of the present invention, as shown in fig. 1, where the method includes:
101. setting up on-body channels under different polarization combinations for the human body model under each frame action, and carrying out electromagnetic simulation to obtain frequency domain transmission signals of the on-body channels;
in the embodiment of the invention, different polarization modes are distinguished according to the placement direction of the antenna relative to the surface of the human body, the placement mode parallel to the surface of the human body is set as horizontal polarization H, the placement mode perpendicular to the surface of the human body is set as vertical polarization V, the antenna corresponding to the placement position is set at the position of the human body model according to the on-body channel, and the frequency domain transmission signal H (f) of the on-body channel is obtained through simulation.
102. Determining the power delay distribution of a link through the frequency domain transmission signal, and fitting according to the average power delay distribution to obtain a power attenuation index;
in the embodiment of the invention, the frequency domain transmission signal of the on-body channel is subjected to inverse Fourier transform to obtain a channel impulse response, and the power delay distribution is obtained according to the channel impulse response; the method comprises the steps of obtaining average power delay distribution of a channel on a body after carrying out statistical average on channel frequency domain transmission signals under a plurality of different human models; fitting the average power delay distribution to obtain a power attenuation index of the average power delay distribution which is exponentially attenuated along with time.
103. Extracting multipath parameters corresponding to the power delay distribution, and obtaining the arrival time and path loss power of each independent path according to the multipath parameters;
in the embodiment of the invention, the multipath identification range is determined according to the maximum peak, the maximum peak and other peaks are determined from the power delay distribution, and the peak attenuated by more than 30dB relative to the power value of the maximum peak is eliminated.
In some embodiments, peaks that attenuate power values relative to the maximum peak by more than 20dB may also be eliminated in this embodiment.
104. Calculating the cross polarization discrimination rate of each path in the channel multipath under each frame action, and performing normal distribution fitting on probability distribution of the cross polarization discrimination rate to obtain the average value of a cross polarization discrimination rate distribution model;
in the embodiment of the invention, four polarization combinations (HH, HV, VV, VH) can be obtained according to the different polarization modes of the transmitting end and the receiving end, and when the polarization modes of the transmitting end and the receiving end are the same, the co-polarized power (P) of the channel is obtained HH 、P VV ) Cross-polarized power (P) of channels is obtained when the polarization modes are different HV 、P VH ) Taking the ratio of the co-polarized power to the cross-polarized power as the cross-polarization discrimination rate; h represents horizontal polarization, V represents vertical polarization, HH represents horizontal-horizontal co-polarization of the transmitting-side antenna and the receiving-side antenna; HV represents that the transmitting end antenna and the receiving end antenna adopt horizontal-vertical cross polarization; VV means that the transmitting-side antenna and the receiving-side antenna adopt vertical-vertical co-polarization; VH denotes that the transmitting-side antenna and the receiving-side antenna adopt vertical-horizontal cross polarization.
In the embodiment of the invention, the probability distribution of the cross polarization discrimination rate of each path in the channel multipath is subjected to normal distribution fitting to obtain the average value mu of the normal distribution model.
105. Performing normal distribution fitting on probability distribution of path loss of a first path of a channel under a plurality of frame actions to obtain standard deviation of a path loss distribution model of the first path;
in the embodiment of the invention, the probability distribution of the path loss of the first path of the channel under continuous multi-frame actions is subjected to normal distribution fitting to obtain the standard deviation sigma of the normal distribution model.
106. Statistically analyzing probability distribution conditions obeyed by inter-path delay of the arrival time of each path and the arrival time of the previous path respectively, and fitting an optimal inter-path delay probability distribution model;
in the embodiment of the invention, the probability distribution of the delay between paths is required to be statistically analyzed, so that an optimal probability distribution model is fitted, and important parameters of the distribution model are obtained.
107. Constructing channel impulse response in a co-polarization mode according to the average path loss, arrival time, power attenuation index, path loss distribution model and parameters of the inter-path delay probability distribution model of the first path; and constructing the channel impulse response in the cross polarization mode by utilizing the parameters of the cross polarization discrimination distribution model based on the parameters of the channel impulse response in the co-polarization mode. .
In the embodiment of the invention, for constructing the channel impulse response in the co-polarization mode, the method mainly comprises the steps of generating time delay tau k Setting the arrival time of the first path of the channel as the average arrival time of the first path, and generating the time delay tau between two adjacent paths according to the optimal probability distribution model obeyed by the delay between the paths k Then delay the time by tau k Adding to the arrival time of the previous path; determining gain coefficients alpha of each path according to the path loss distribution model of the first path k The method comprises the steps of carrying out a first treatment on the surface of the According to the gain coefficient alpha k Inter-path delay τ of arrival time k And calculating to obtain the channel impulse response in the co-polarization mode.
In the embodiment of the invention, for constructing the channel impulse response in the cross polarization mode, the path loss between each path of the cross polarization channel and the co-polarization channel is calculated mainly according to the cross polarization discrimination rate; and calculating the channel impulse response of the cross polarization channel according to the generation mode of the channel impulse response in the co-polarization mode based on the path loss.
Fig. 2 is a flowchart of a method for modeling multipath channels of a dynamic on-body channel in a wireless body area network according to a preferred embodiment of the present invention, as shown in fig. 2, where the method includes:
201. carrying out framing treatment on the continuous dynamic actions to obtain a human body model under each frame of actions;
in the embodiment of the invention, continuous dynamic actions of a human body are subjected to framing treatment, the dynamic continuous actions of the human body are split, and one dynamic action of the human body is decomposed into a combination of a plurality of frames of continuous action gestures, so that a human body model with different gestures under each frame of actions is obtained.
Fig. 3 is a 15-frame division diagram of walking motion provided by the embodiment of the invention, as shown in fig. 3, the diagram shows that dynamic continuous human body motion is split, and one dynamic human body motion is decomposed into 15-frame continuous motion gesture combinations, so that 15 human body models of different gestures under each frame of motion are obtained.
202. Setting up on-body channels under different polarization combinations for the human body model under each frame action, and carrying out electromagnetic simulation to obtain frequency domain transmission signals of the on-body channels;
in the embodiment of the invention, 15 different human models are respectively imported into electromagnetic simulation software, wherein the electromagnetic simulation software can select a CST software platform; assuming that the on-waist-chest channel model needs to be studied, a receiving end antenna (Rx) is set at the left waist position of the model according to the on-waist-chest channel to be studied, and a transmitting end antenna (Tx) is set at the chest. The antenna is placed at a distance of about 5mm from the mannequin, and the specific placement position is shown in fig. 4. Antennas can be classified into horizontal polarization and vertical polarization according to the placement direction with respect to the surface of the human body. As shown in fig. 5, the antenna is placed in horizontal polarization (H) parallel to the surface of the human body and in vertical polarization (V) perpendicular to the surface of the human body. Therefore, there are 4 polarization combinations (HH, HV, VV, VH) for the transmit and receive antennas.
The body channel under different polarization combinations is set for the manikin under each frame action, and the placement positions of the waist-chest body channels Rx and Tx under the VV polarization combination mode are shown in fig. 5. After Rx and Tx are set, electromagnetic simulation can be performed to obtain a frequency domain transfer function H (f) of the channel.
203. Determining the power delay distribution of a link through the frequency domain transmission signal, and fitting according to the average power delay distribution to obtain a power attenuation index;
the power delay profile (Power Delay Profile, PDP) p (τ) can be derived from the channel impulse response h (t), i.e.:
first, the channel impulse response H (t) can be obtained by performing inverse fourier transform on the channel frequency domain transfer function H (f), expressed as:
h(t)＝F -1 {H(f)}
the power delay distribution is calculated according to the channel impulse response h (t), namely expressed as:
p(τ)＝<h(τ)·h * (τ)>
where H (F) is the frequency domain transfer function of the channel, F -1 {. The inverse fourier transform is represented. The simulation result diagram shown in fig. 6 is a normalized PDP diagram of the waist-chest channels of 15 different models in VV polarization mode.
After the frequency domain data under a plurality of different human models are statistically averaged, statistical average power delay distribution (Average Power Delay Profile, APDP) of the channels on the body under study is obtained, and the APDP decays exponentially with time, which can be expressed as:
wherein Ω 0 And τ 0 The power and arrival time of the first path, respectively, and γ is the power decay index.
After carrying out statistical averaging on frequency domain data under 15 different human models in a VV polarization mode, obtaining the APDP of the investigated waist-chest channel, and carrying out data fitting on the APDP, converting the APDP into an expression taking dB as a unit, wherein the expression is expressed as follows:
wherein PL is VV (t 0 ) And t 0 The average path loss 56.45dB and the average arrival time of the first path of the channel in VV polarization mode are 1.03ns, respectively. The fitting graph is shown in fig. 7, and the fitting result of the obtained power attenuation index gamma is 0.30ns.
204. Extracting multipath parameters corresponding to the power delay distribution, and obtaining the arrival time and path loss power of each independent path according to the multipath parameters;
in the embodiment of the invention, all obvious peaks in the PDP are caused by multipath, the arrival time and path loss power of each independent path can be obtained by identifying the peaks, namely multipath parameters of a channel are extracted, and when peak power values are attenuated by more than 30dB compared with the power value of the maximum peak, the peak power values are not included in the identification range.
Of course, in some possible implementations, the peak power value will not be included in the identification range when it is attenuated by 20-40 dB compared to the maximum peak power value.
205. Calculating the cross polarization discrimination rate of each path in the channel multipath under each frame action, and performing normal distribution fitting on probability distribution of the cross polarization discrimination rate to obtain the average value of a cross polarization discrimination rate distribution model;
in the embodiment of the invention, four polarization combinations (HH, HV, VV, VH) can be obtained according to the different polarization modes of the transmitting end and the receiving end, and when the polarization modes of the transmitting end and the receiving end are the same, the co-polarized power (P) of the channel can be obtained HH 、P VV ) Cross-polarized power (P HV 、P VH ) Cross polarization discrimination (Cross-polarization discrimination, XPD) is defined as the ratio of co-polarized power to Cross polarized power expressed as follows:
wherein X is aa-bc Represents the cross polarization discrimination using co-polarization aa and cross polarization bc; a. b, c e { H, V }, b+.c.
Calculating X of each path of channel under each frame action VV-VH And X for each path of the channel on the waist-chest as shown in FIG. 8 VV-VH Normal distribution fitting is carried out on probability distribution of (2), X VV-VH Fitting the average value obtained from the normal distribution
8.54dB.
206. Performing normal distribution fitting on probability distribution of path loss of a first path of a channel under a plurality of frame actions to obtain standard deviation of a path loss distribution model of the first path;
as shown in fig. 9, the probability distribution of the path loss of the first path of the channel under 15 frame operation is fitted to the normal distribution, and the standard deviation σ of the normal distribution is 2.35dB.
For steps 205 and 206, the probability density function that can yield a normal distribution is expressed as:
wherein μ and σ are the mean and standard deviation of the variables in the normal distribution, and step 205 and step 206 correspond to two different normal distribution models, respectively; in the embodiment of the present invention, the standard deviation σ may refer to a standard deviation of a path loss distribution model of the first path; the average μmay refer to the cross-polarization discrimination X for each path VV-VH Fitting the average value obtained from the normal distribution
I.e. mean +.of cross-polarization discrimination distribution model>
207. Statistically analyzing probability distribution conditions obeyed by inter-path delay of the arrival time of each path and the arrival time of the previous path respectively, and fitting an optimal inter-path delay probability distribution model;
the inter-path delay is the difference between the arrival time of each path and the arrival time of the previous path, and the probability distribution of the inter-path delay of the channels under 15 different human models is statistically analyzed and passed through the second-order AIC c And finding out the best distribution model obeyed by the path loss. Alternative distribution models are: rayleigh distribution, gamma distribution, inverse gaussian distribution, weibull distribution, and rice distribution. Table 1 is a comparison of the results of these several fitting models to the inter-path delay profile fit.
Table 1 comparison of the fit model to the delay profile between paths
The metric used to select the best distribution function is a second order red pool information content criterion (Akaike Information Criterion, AIC c ) Second order AIC c The calculation formula of (2) is as follows:
wherein, the liquid crystal display device comprises a liquid crystal display device,
for the maximum log likelihood value of unknown parameters theta under given data and model conditions, K is the number of estimated parameters in the model, and n is the number of samples; by AIC between several models c The comparison of the relative values of (2) determines the best probability distribution model, and the form of the relevant metric can be expressed as:
Δ i ＝AIC c,i -min{AIC c }
wherein AIC c,i AIC representing ith model c A value; let delta i The model of 0 is the best model.
From table 1, it can be seen that the best probability distribution model of the inter-path delay is an inverse gaussian distribution, wherein the inverse gaussian distribution (Inverse Gaussian distribution) is a commonly used distribution in statistics, and the density function is:
according to the second-order red pool information quantity criterion, calculating to obtain a proportion parameter mu obtained by inverse Gaussian distribution fitting τ Is 0.58 and the shape parameter lambda τ 5.21; thus, based on the proportional parameter μ τ And a shape parameter lambda τ Can obtain the correspondingAn optimal probability distribution model.
208. Constructing channel impulse response in a co-polarization mode according to the average path loss, arrival time, power attenuation index, path loss distribution model and parameters of the inter-path delay probability distribution model of the first path; and constructing the channel impulse response in the cross polarization mode by utilizing the parameters of the cross polarization discrimination distribution model based on the parameters of the channel impulse response in the co-polarization mode. All statistical models and parameters required for the channel model are shown in table 2;
table 2 all statistical models and parameters required for the channel model
From these parameters, a channel impulse response can be constructed, which is the following:
wherein alpha is k Is the path gain, τ, of the kth path k Is the time delay of the kth path relative to the arrival time of the first path.
First generating a time delay τ k The first path arrival time of the channel is 1.03ns as the average arrival time of the first path, after which the time delay tau between two adjacent paths is generated according to the inverse Gaussian distribution obeyed by the inter-path delay k Adding the same to the arrival time of the previous path; next, the gain coefficient alpha of each path is determined k The definition is:
α k ＝p k β k
wherein p is k Representing the probability of distribution, p k Taking +1 and-1 with equal probability; beta k Representing the gain coefficient alpha k Absolute value of (2); since the path loss follows a normal distribution, there are:
10lg(β k 2 )∝Normal(μ k ,σ 2 )
thus, the mean μ in the normal distribution k The method can be written as follows:
by the mu k Gain coefficient alpha of each path can be obtained k The method comprises the steps of carrying out a first treatment on the surface of the Wherein the mean mu k May refer to the mean of the path loss distribution model for the kth path. The resulting impulse response model is shown in fig. 10.
The path loss of each path of the cross polarization channel and the co-polarization channel has the following relation:
PL bc ＝PL aa +X aa-bc [dB]
wherein a, b, c ε { H, V }, b+.c, PL bc PL is the path loss value of each path of the channel in cross polarization mode aa For the path loss value of each path of the channel in the co-polarization mode, PL is calculated bc Substituted PL aa And then constructing a cross polarization channel impulse response function by using a statistical model and parameters of the channel in a co-polarization mode.
From the average path loss PL (t) of the first path of the channel in the VV polarization mode in step 203 0 ) = 56.45dB and X obtained in 205 steps above VV-VH Fitting a normal distribution mean
The average path loss PL of the first path of the channel under VH polarization mode can be calculated VH (t 0 ) = 64.99dB. And replacing the path loss value of the channel under the VV co-polarization mode with the path loss value of the channel under the VH cross-polarization mode, and constructing a channel impulse response function under the cross-polarization mode by using the statistical model and parameters of the channel under the table 1 co-polarization mode. Finally generated VH polarizationThe impulse response model in this manner is shown in fig. 11.
Specifically, the present invention can obtain the first path loss PL of the co-polarized channel by calculating VV (t 0 ) Calculating a first path loss PL of a cross-polarized channel VH (t 0 ) Then re-use PL VH (t 0 ) And constructing the co-polarized channel impulse response by using various parameters under other co-polarized channels, so that the construction mode of the cross-polarized channel impulse response omits the steps of calculating a path loss model, an inter-path delay model and the like compared with the co-polarized channels.
It can be understood that, in the embodiment of the present invention, the channel response of the cross polarization mode is obtained by using the average value of the cross polarization discrimination distribution model to reversely calculate the path loss of the first path of the cross polarization, and other parameters are all constructed by using the parameters of the co-polarization mode. Therefore, the construction of the cross-polarized channel response omits the steps of calculating the path loss model and the inter-path delay model as compared to the co-polarized channel.
In the description of the present invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "another end," "upper," "one side," "top," "inner," "outer," "front," "center," "two ends," etc. indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the invention and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the invention.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "configured," "connected," "secured," "rotated," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intermediaries, or in communication with each other or in interaction with each other, unless explicitly defined otherwise, the meaning of the terms described above in this application will be understood by those of ordinary skill in the art in view of the specific circumstances.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A method for modeling multipath channels of a dynamic on-body channel in a wireless body area network, the method comprising:
setting up on-body channels under different polarization combinations for the human body model under each frame action, and carrying out electromagnetic simulation to obtain frequency domain transmission signals of the on-body channels;
determining the power delay distribution of a link through the frequency domain transmission signal, and fitting according to the average power delay distribution to obtain a power attenuation index;
the method for acquiring the power attenuation index comprises the steps of performing inverse Fourier transform on a frequency domain transmission signal of a channel on a body to obtain a channel impulse response, and obtaining power delay distribution according to the channel impulse response; the method comprises the steps of obtaining average power delay distribution of a channel on a body after carrying out statistical average on channel frequency domain transmission signals under a plurality of different human models; fitting the average power delay distribution to obtain a power attenuation index of the average power delay distribution which decays exponentially with time;
extracting multipath parameters corresponding to the power delay distribution, and obtaining the arrival time and path loss power of each independent path according to the multipath parameters;
calculating the cross polarization discrimination rate of each path in the channel multipath under each frame action, and performing normal distribution fitting on probability distribution of the cross polarization discrimination rate to obtain the average value of a cross polarization discrimination rate distribution model;
the calculation mode of the cross polarization discrimination of each path comprises four poles obtained according to the different polarization modes of the antenna at the transmitting end and the antenna at the receiving endA combined mode (HH, HV, VV, VH) for obtaining co-polarized power (P) of the channel when the polarization modes of the transmitting and receiving antennas are the same HH 、P VV ) Cross-polarized power (P) of channels is obtained when the polarization modes are different HV 、P VH ) Taking the ratio of the co-polarized power to the cross-polarized power as the cross-polarization discrimination rate; h represents horizontal polarization, V represents vertical polarization; HH means that the transmitting-side antenna and the receiving-side antenna adopt horizontal-horizontal co-polarization; HV represents that the transmitting end antenna and the receiving end antenna adopt horizontal-vertical cross polarization; VV means that the transmitting-side antenna and the receiving-side antenna adopt vertical-vertical co-polarization; VH denotes that the transmitting-end antenna and the receiving-end antenna adopt vertical-horizontal cross polarization;
performing normal distribution fitting on probability distribution of path loss of a first path of a channel under a plurality of frame actions to obtain standard deviation of a path loss distribution model of the first path;
statistically analyzing probability distribution conditions obeyed by inter-path delay of the arrival time of each path and the arrival time of the previous path respectively, and fitting an optimal inter-path delay probability distribution model;
constructing channel impulse response in a co-polarization mode according to the average path loss, arrival time, power attenuation index, path loss distribution model and parameters of the inter-path delay probability distribution model of the first path; and constructing the channel impulse response in the cross polarization mode by utilizing the parameters of the cross polarization discrimination distribution model based on the parameters of the channel impulse response in the co-polarization mode.
2. The method for modeling multipath channels of a dynamic body channel in a wireless body area network according to claim 1, further comprising framing continuous dynamic actions of a human body before obtaining a human body model under each frame action, splitting the dynamic continuous human body actions, and decomposing a dynamic human body action into a combination of a plurality of frame continuous action gestures, thereby obtaining a human body model with different gestures under each frame action.
3. The method for modeling a dynamic on-body channel in a wireless body area network according to claim 1, wherein the obtaining the frequency domain transmission signal of the on-body channel includes differentiating different polarization modes according to the placement direction of the antenna relative to the surface of the human body, setting the placement mode parallel to the surface of the human body as horizontal polarization H, setting the placement mode perpendicular to the surface of the human body as vertical polarization V, setting the antenna corresponding to the placement position at the position of the human body model according to the on-body channel, and obtaining the frequency domain transmission signal of the on-body channel through simulation.
4. The method of claim 1, wherein extracting the multipath parameters corresponding to the power delay profile includes determining a multipath identification range based on a maximum peak, determining the maximum peak and other peaks from the power delay profile, and removing peaks that attenuate power values by more than 30dB compared to the maximum peak.
5. The method of claim 1, wherein said fitting an optimal inter-path delay probability distribution model comprises determining alternative distribution models; calculating second-order red pool information quantity standard values of probability distribution conditions of delay among paths under different alternative distribution models by adopting a second-order red pool information quantity standard; and comparing and judging the second-order red pool information quantity standard values of all the alternative distribution models to obtain an optimal probability distribution model of the inter-path delay.
6. The method of claim 1, wherein constructing the channel impulse response in co-polarization mode comprises setting a first path arrival time of the channel to be an average arrival time of the first path, generating a time delay τ between two adjacent paths according to an optimal inter-path delay probability distribution model to which the inter-path delay is subjected k Adding the time delay to the arrival time of the previous path; determining gain coefficients alpha of each path according to the path loss distribution model of the first path k The method comprises the steps of carrying out a first treatment on the surface of the And calculating to obtain the channel impulse response in the co-polarization mode according to the gain coefficient and the inter-path delay of the arrival time.
7. The method for modeling multipath channel of dynamic on-body channel in wireless body area network according to claim 1 or 6, wherein said constructing channel impulse response in cross polarization mode by using parameters of cross polarization discrimination rate distribution model includes calculating path loss between each path of cross polarization channel and co-polarization channel according to said cross polarization discrimination rate; and calculating the channel impulse response of the cross polarization channel according to the generation mode of the channel impulse response in the co-polarization mode based on the path loss.
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