CN114070440A - Doppler channel model construction method and system based on dual-path propagation - Google Patents
Doppler channel model construction method and system based on dual-path propagation Download PDFInfo
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Abstract
The invention discloses a Doppler channel model construction method and a system based on dual-path propagation, which comprises the following steps: s1, constructing a small-scale fading model based on frequency selective fading and fast fading; s2, constructing a large-scale fading model based on an Okumura-Hata actual measurement data model; s3, constructing a narrow-band Gaussian noise model; and S4, constructing a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model. The invention constructs a Doppler channel model based on double-path propagation by comprehensively considering various losses in the channel transmission process based on an actually measured data model and theoretical calculation, more truly simulates the channel transmission environment, and provides accurate channel parameters for algorithm development and communication system design.
Description
Technical Field
The invention relates to the technical field of channel models, in particular to a Doppler channel model construction method and system based on dual-path propagation.
Background
With continuous development of various types of communication services and rapid development of the internet of things, the accuracy requirement of people on channel models in various scenes is higher and higher, and a channel model approaching the real environment without any difference is urgently needed for better developing a baseband algorithm and researching the performance of a communication system.
The existing channel models mainly have the following directions, the first channel model based on the environment measured data has large data volume and long time consumption, and data can be collected only under some common scenes; the second is a channel model based on pure theoretical calculation, which is easy to implement but often has a large difference from the actual channel environment.
Disclosure of Invention
The invention aims to provide a channel model construction method with small data volume and high precision.
In order to solve the above problems, the present invention provides a doppler channel model construction method based on dual path propagation, which includes the following steps:
s1, constructing a small-scale fading model based on frequency selective fading and fast fading;
s2, constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
s3, constructing a narrow-band Gaussian noise model;
and S4, constructing a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model.
As a further improvement of the present invention, in step S2, the large-scale fading model is constructed as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale attenuation factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
As a further improvement of the present invention, step S3 includes:
s31, generating two independent components nc (t) and ns (t) which obey Gaussian distribution, wherein the mean value of the two components is 0, and the variance is rho ^ 2;
s32, constructing a narrow-band Gaussian noise model as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein, B is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
As a further improvement of the present invention, step S1 includes:
s11, based on frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, the transmitter and the receiver are in barrier-free transmission, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, signals transmitted by the transmitter are reflected to the receiver through barriers, and the time delay is determined by the total distance between the transmitter and the barriers and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
s12, based on the fast fading caused by the doppler frequency offset caused by the fast movement of the transmitter, let: and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
As a further improvement of the present invention, step S4 includes:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
In order to solve the above problem, the present invention further provides a doppler channel model building system based on dual path propagation, which includes:
the small-scale fading model building module is used for building a small-scale fading model based on frequency selective fading and fast fading;
the large-scale fading model construction module is used for constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
the narrow-band Gaussian noise model building module is used for building a narrow-band Gaussian noise model;
and the Doppler channel model building module is used for building a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model.
As a further improvement of the invention, the large-scale fading model is constructed as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale fading factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
As a further improvement of the invention, the constructed narrow-band Gaussian noise model is as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein nc (t) and ns (t) are two mutually independent components which obey Gaussian distribution, the mean value of the two components is 0, and the variance is rho ^ 2; b is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
As a further improvement of the present invention, the small-scale fading model building module comprises:
the frequency selective fading modeling module is used for simulating frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, barrier-free transmission exists between a transmitter and a receiver, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, a signal transmitted by the transmitter is reflected to the receiver through a barrier, and the time delay is determined by the total distance between the transmitter and the barrier and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
a fast fading modeling module, configured to simulate fast fading caused by doppler frequency offset caused by fast movement of a transmitter, such that:
and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
As a further improvement of the present invention, the constructing a doppler channel model based on dual path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band gaussian noise model includes:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
The invention has the beneficial effects that:
the invention constructs a Doppler channel model based on double-path propagation by comprehensively considering various losses in the channel transmission process based on an actually measured data model and theoretical calculation, more truly simulates the channel transmission environment, and provides accurate channel parameters for algorithm development and communication system design.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a Doppler channel model construction method based on dual path propagation in the preferred embodiment of the invention;
FIG. 2 is a diagram of frequency selective fading in a preferred embodiment of the present invention;
FIG. 3 is a diagram of fast fading in a preferred embodiment of the present invention;
FIG. 4 is a diagram of large scale fading in a preferred embodiment of the invention;
FIG. 5 is a diagram of narrow band Gaussian noise in a preferred embodiment of the invention;
FIG. 6 is a diagram of the channel frequency response in a preferred embodiment of the present invention;
fig. 7 is a diagram of channel impulse response in a preferred embodiment of the present invention.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
As shown in fig. 1, a method for constructing a doppler channel model based on dual path propagation in a preferred embodiment of the present invention includes the following steps:
s1, constructing a small-scale fading model based on frequency selective fading and fast fading; the method specifically comprises the following steps:
s11, based on frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, the transmitter and the receiver are in barrier-free transmission, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, signals transmitted by the transmitter are reflected to the receiver through barriers, and the time delay is determined by the total distance between the transmitter and the barriers and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
s12, fast fading caused by doppler frequency offset caused by fast movement of the transmitter, wherein the fast fading characteristic is that when the transmitter moves towards the receiver at a speed v, a doppler frequency shift phenomenon generated by electromagnetic waves causes a fast phase change, which in turn causes attenuation, such that: and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
S2, constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
the large-scale fading model is constructed as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale fading factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
S3, constructing a narrow-band Gaussian noise model; the method specifically comprises the following steps:
s31, generating two independent components nc (t) and ns (t) which obey Gaussian distribution, wherein the mean value of the two components is 0, and the variance is rho ^ 2;
s32, constructing a narrow-band Gaussian noise model as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein, B is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
And S4, constructing a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model. The method specifically comprises the following steps:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
The preferred embodiment of the invention also discloses a Doppler channel model construction system based on dual-path propagation, which comprises the following modules:
the small-scale fading model building module is used for building a small-scale fading model based on frequency selective fading and fast fading;
the large-scale fading model construction module is used for constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
specifically, the large-scale fading model is constructed as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale fading factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
The narrow-band Gaussian noise model building module is used for building a narrow-band Gaussian noise model;
specifically, the constructed narrow-band gaussian noise model is as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein nc (t) and ns (t) are two mutually independent components which obey Gaussian distribution, the mean value of the two components is 0, and the variance is rho ^ 2; b is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
And the Doppler channel model building module is used for building a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model.
Specifically, the small-scale fading model building module comprises:
the frequency selective fading modeling module is used for simulating frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, barrier-free transmission exists between a transmitter and a receiver, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, a signal transmitted by the transmitter is reflected to the receiver through a barrier, and the time delay is determined by the total distance between the transmitter and the barrier and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
a fast fading modeling module, configured to simulate fast fading caused by doppler frequency offset caused by fast movement of a transmitter, such that:
and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
The method for constructing the Doppler channel model based on the dual-path propagation by combining the small-scale fading model, the large-scale fading model and the narrow-band Gaussian noise model specifically comprises the following steps:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
In order to verify the effectiveness of the doppler channel model construction method and system based on dual-path propagation, in a specific embodiment, channel modeling is performed on 60 frequency points of 900mhz, 25-74khz frequency bands, with the frequency band interval of 1khz, and the specific steps are as follows:
(1) and (3) performing small-scale fading modeling: setting the carrier frequency as f 900 x 10 x 6+1 x 10 x 3hz, the transmitter is 2km away from the receiver, the transmitter is 3km away from the obstacle, and the obstacle is 5km away from the receiver. The transmitter transmission signal is X2 × cos (2 × pi f × t), the transmission power is 2w, the moving speed toward the receiver is v 10m/s, the first received signal is Y1 × 2 × cos (2 pi f ((1-v/c) t-2 10^3/3 ^ 10^8)), the second received signal is Y2 ═ cos (a) · 2 cos (2 × pi f ((1+ v/c) · t-8 ^ 10 3/3 ^8)), wherein α pi/4 is the angular difference between two paths to the receiver, and is uniformly distributed from [0,2pi ^ f). Y3 is the two-path composite signal received by the receiver, Y1+ Y2. The correlation bandwidth B is calculated to be 1/(6 Td) 8.3khz, Td being the difference between the two-path delays. And calculating the correlation time T ═ 1/(12 ^ fm) ═ 74us, and fm ═ v ^ f/c ═ 375 ^ 900 ^ 10^6+10^3)/3 ^ 10^8 ^ 1125hz as the Doppler frequency shift. Referring to fig. 2, it can be seen that the signal fading amplitude is different in different frequency bands, and referring to fig. 3, it can be seen that the signal fading amplitude is different in different time.
(2) And (3) performing large-scale fading modeling: an Okumura-Hata model function based on environment actual measurement data is adopted, the height hm of a receiving antenna is 90 meters, the height hb of a transmitting antenna is 1.5 meters, the antenna gain Db of a transmitter is 17Db, the antenna gain Dm of a receiver is 3Db, and the distance between the transceiver and the receiving antenna is d. p-69.55 +26.16 log10(900 x 10 x 6+1 x 10 x 3) -13.82 log10(hb) -A _ hm + (44.9-6.55 log10(hb)) -log 10(d) -Db-Dm; the environmental correction factor a _ hm is 3.2 (log10(11.75 hm)) 2-4.97, and referring to fig. 4, the relationship between large scale fading and the distance between the transmitter and receiver can be seen.
(3) Performing narrow-band Gaussian noise modeling: generating two mutually independent components nc (t) and ns (t) which obey Gaussian distribution, wherein the mean value of the two components is 0, the variance is rho ^2 ^ 1.5, and the noise power is 0.04 w; noise n (t) ═ 0.2 × nc (t) — cos (2 × pi × f × t) — 0.2 × ns (t) (2 × pi t); referring to fig. 5, the time domain information of the narrow-band gaussian noise can be seen.
(4) And (3) counting the transmission characteristics of the channel: combining small scale fading, large scale fading and noise interference, the transmitter transmits a signal of X-A-cos (2-pi-f-t), and the receiver receives a signal of X-A-cos (2-pi-f-t)
Wherein the first path is large scale fading:
p1＝69.55+26.16*log10(900*10^6+1*10^3)-13.82*log10(90)-A_hm+(44.9-6.55*log10(90))*log10(2*10^3)-17-3；
second-path large-scale fading:
p2＝69.55+26.16*log10(900*10^6+1*10^3)-13.82*log10(90)-A_hm+(44.9-6.55*log10(90))*log10(8*10^3)-17-3
a _ hm is 3.2 (log10(11.75 × 1.5)) 2-4.9. And respectively carrying out Fourier transform on X and Y, taking frequency points corresponding to f to obtain energy values Xp and Yp, and enabling pl1 to be Xp/Yp to be the attenuation factor of the frequency points. Replacing other carrier frequencies f 900 × 10^6+2 × 10^3, executing the same process to obtain corresponding pl2, repeating the process for 60 times to obtain pl1, pl2. After the mean value of the frequency response is removed, fourier transform is performed, and the first half section of the result is the channel impulse response of the frequency band, referring to fig. 7.
The invention constructs a Doppler channel model based on double-path propagation by comprehensively considering various losses in the channel transmission process based on an actually measured data model and theoretical calculation, more truly simulates the channel transmission environment, and provides accurate channel parameters for algorithm development and communication system design.
The above embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. A Doppler channel model construction method based on dual-path propagation is characterized by comprising the following steps:
s1, constructing a small-scale fading model based on frequency selective fading and fast fading;
s2, constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
s3, constructing a narrow-band Gaussian noise model;
and S4, constructing a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model.
2. The method for constructing a doppler channel model based on dual path propagation as claimed in claim 1, wherein the large scale fading model constructed in step S2 is as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale fading factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
3. The dual path propagation-based doppler channel model construction method according to claim 1, wherein the step S3 includes:
s31, generating two independent components nc (t) and ns (t) which obey Gaussian distribution, wherein the mean value of the two components is 0, and the variance is rho ^ 2;
s32, constructing a narrow-band Gaussian noise model as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein, B is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
4. The dual path propagation-based doppler channel model construction method according to claim 1, wherein the step S1 includes:
s11, based on frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, the transmitter and the receiver are in barrier-free transmission, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, signals transmitted by the transmitter are reflected to the receiver through barriers, and the time delay is determined by the total distance between the transmitter and the barriers and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
s12, based on the fast fading caused by the doppler frequency offset caused by the fast movement of the transmitter, let: and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
5. The dual path propagation-based doppler channel model construction method according to claim 4, wherein the step S4 comprises:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
wherein, p1 and p2 are large scale fading factors corresponding to the first path and the second path respectively, and n (t) is noise;
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
6. A Doppler channel model construction system based on dual path propagation is characterized by comprising the following components:
the small-scale fading model building module is used for building a small-scale fading model based on frequency selective fading and fast fading;
the large-scale fading model construction module is used for constructing a large-scale fading model based on an Okumura-Hata actual measurement data model;
the narrow-band Gaussian noise model building module is used for building a narrow-band Gaussian noise model;
and the Doppler channel model building module is used for building a Doppler channel model based on dual-path propagation by combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model.
7. The dual-path propagation-based doppler channel model construction system of claim 6, wherein the large-scale fading model is constructed as follows:
p＝69.55+26.16*log10(f)-13.82*log10(hb)-A_hm+(44.9-6.55*log10(hb))*log10(r)-Db-Dm
wherein, p is a large-scale fading factor calculated based on an Okumura-Hata model, f is a carrier frequency, hb is a receiver antenna height, hm is a transmitter antenna height, a _ hm is an environment correction factor, Db is a receiver antenna gain, Dm is a transmitter antenna gain, and a _ hm is 3.2 (log10(11.75 hm)). times 2-4.97.
8. The dual-path propagation-based doppler channel model construction system of claim 6, wherein the constructed narrow-band gaussian noise model is as follows:
n(t)＝B*nc(t)*cos(2*pi*f*t)-B*ns(t)*sin(2*pi*t)
wherein nc (t) and ns (t) are two mutually independent components which obey Gaussian distribution, the mean value of the two components is 0, and the variance is rho ^ 2; b is a noise power factor used for regulating and controlling the power of noise, f is a carrier frequency, the random envelope of the noise n (t) obeys Rayleigh distribution, and the phase obeys uniform distribution.
9. The dual-path propagation-based doppler channel model construction system according to claim 6, wherein the small-scale fading model construction module comprises:
the frequency selective fading modeling module is used for simulating frequency selective fading caused by multipath propagation, the first two paths in multipath transmission are used as transmission paths, the first path is LOS transmission, barrier-free transmission exists between a transmitter and a receiver, the time delay is determined by the distance between the transmitter and the receiver, the second path is NLOS transmission, a signal transmitted by the transmitter is reflected to the receiver through a barrier, and the time delay is determined by the total distance between the transmitter and the barrier and the receiver; the two paths reach the receiver with different phases, the peak-valley of the carrier wave is counteracted, and then fading is caused, the phase difference of the two paths is 0, the fading is minimum, the phase difference is pi, the fading is maximum, and the phase difference of the two paths of the carrier waves with different frequencies is different, and the fading is different; simplifying X ═ a × cos (2 × pi × f × t) as a transmitter transmission signal, Y1 ═ a × cos (2 × pi f (t-r/c)) as a first diameter, and Y2 ═ cos (a) × a × cos (2 × pi f (t- (2d-r)/c)) as a second diameter; y3 ═ Y1+ Y2 is the receiver receive signal, i.e.:
Y3＝A*cos(2*pi*f*(t-r/c))+cos(ɑ)*A*cos(2*pi*f*(t-(2d-r)/c))
wherein, a is amplitude, f is carrier frequency, r is transmitter-receiver distance, d is obstacle-receiver distance, c is electromagnetic wave speed, a is electromagnetic wave incident angle of the second path, a is uniformly distributed at [0,2 × pi ], phase difference θ between the two paths is 4 × pi (d-r)/c, the phase difference θ is changed from 0 to pi, namely attenuation is from minimum to maximum, change of the carrier frequency f is Δ f ═ 1/[2 ((2d-r)/c-r/c) ], and Td ═ 2d-r)/c-r/c, namely difference of propagation delays of the two paths; when the carrier frequency f changes the reciprocal of twice of the difference of the two-path time delay, the attenuation of the received signal is from minimum to maximum;
a fast fading modeling module, configured to simulate fast fading caused by doppler frequency offset caused by fast movement of a transmitter, such that: and Y4 is A & ltcos (2 & ltpi & gt & ltf & gt ((1+ v/c) & ltt-r/c)) + cos (A & ltpi & gt cos (2 & ltpi & gt f ((1-v/c) & ltt- (2d-r)/c)), namely the small-scale fading model, the phase difference theta of the two paths is 4 & ltpi & gt & ltf [ (d-r-v & ltt)/c ], the phase difference theta is changed from 0 to pi, the change of the emission time t is c/(4 & ltf & gt v), the Doppler frequency offset fm & ltv)/c, and the time change t is 1/(4 & ltfm), and the received signal attenuation is from minimum to maximum.
10. The dual path propagation-based doppler channel model construction system according to claim 9, wherein the combining the small-scale fading model, the large-scale fading model and the narrow-band gaussian noise model to construct the dual path propagation-based doppler channel model comprises:
combining a small-scale fading model, a large-scale fading model and a narrow-band Gaussian noise model, and ordering:
wherein, p1 and p2 are large scale fading factors corresponding to the first path and the second path respectively, and n (t) is noise;
respectively carrying out Fourier transform on X and Y, solving energy values as Xp and Yp of frequency points corresponding to f, and enabling pl to be Xp/Yp to be attenuation factors of the frequency points; replacing the carrier frequency f, wherein the carrier interval is 1khz, and executing the steps to obtain the corresponding pl; combining pls of all tested carrier frequency points to obtain the frequency response of the frequency band, and performing Fourier transform after mean value removal on the frequency response to obtain the channel impulse response of the frequency band.
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