The present disclosure relates to the technical field of channel modeling and channel emulators, and especially relates to a method for designing an a time-domain non-stationary vehicle-to-vehicle (V2V) multiple-input multiple-output (MIMO) communication channel emulator.
Before a new communication system be commercialized, the new communication system needs to be practically tested in a corresponding environment. Although the system can be tested on-site in different locations, this method has a relative high cost and is easy to be influenced by surrounding environment. In addition, propagation conditions of a real external field are difficult to be reproduced by comparative analyses of simulation results. A more practical method is to create suitable and stable simulation environments for channels, and then evaluate performances of the communication system in these environments. The channel environments can be controllably and repeatably simulated by channel emulators, which is used for a consistency testing, a performance testing, and an interoperability testing of communication systems. This means that there is no need for an on-site testing, and efficiencies of time and cost can be greatly improved. At present, there is no emulator for a time-domain non-stationary V2V communication channel that supports a birth-death process of clusters and considers macro cells, micro cells, and micro-micro cells.
In summary, it is necessary to establish a method for designing a time-domain non-stationary V2V MIMO communication channel emulator.
In view of this, the objectives of the present disclosure are to provide a method for designing the time-domain non-stationary V2V MIMO communication channel emulator, so as to accurately and stably test a V2V MIMO communication system.
In order to achieve above objectives, the technical solutions adopted by the present disclosure are as follows.
A method for designing a time-domain non-stationary V2V MIMO communication channel emulator is provided. The method includes the following steps.
In Step S1, the basic parameters for the V2V MIMO communication channel are determined.
In Step S2, a V2V two-dimensional (2D) time-domain non-stationary communication channel environment is generated by using a MATLAB, and the environment specifically includes the number of scatterers and positions of the scatterers, a random phase of a non-line-of-sight (NLoS) path, an angle spread of the NLoS path, a sine function lookup table, and an arctangent function lookup table.
In Step S3, parameters generated in Step S2 are imported into a hardware simulation platform to calculate communication channel parameters for the clusters, and the communication channel parameters include an angle distribution and an amplitude distribution, a Verilog code is written for running, and a channel impulse response of the time-domain non-stationary V2V MIMO communication channel is eventually obtained by calculation.
In Step S4, a comparison is performed with a statistical characteristic of a theoretical communication channel model, and an appropriate hardware diagram of a communication channel emulator is designed.
Preferably, in Step S1, in a geometry-based stochastic model for the time-domain non-stationary V2V MIMO communication channel, the basic parameters for the V2V MIMO communication channel include the number of a simulation time point, a simulation time interval, a position of a transmitter, a position of a receiver, a velocity of the transmitter, a velocity of the receiver, a Rice factor, an angle spread coefficient, a total link power, a line-of-sight (LoS) path, a power ratio of a single-bounce (SB) path, a power ratio of a double-bounce (DB) path, the number of initial scatterers, a velocity of the initial scatterers, the number of sub-paths in each cluster, a generation rate for scatterers, a disappearance rate for the scatterers, a motion ratio of the scatterers, a relative coordinate of a receiver antenna and a relative coordinate of a transmitter antenna.
Preferably, Step S2 specifically includes as follows.
In Step S201, the numbers of the scatterers and the positions of the scatterers are generated, and an average survival probability Premain of effective scatterers within a time period Δt is expressed as
where γR denotes a generation rate of the scatterers, Pm denotes a motion percentage, {right arrow over (v)}s
A probability function P(Nnew(Δt)=k) of the number of newly generated scatterers is expressed as
where λ denotes a parameter for a Poisson distribution probability distribution function; and
Eventually, the numbers of the scatterers within each time period Δt are obtained by calculation, which are generated through a MATLAB, and are sequentially stored in a file with a coe suffix.
Position coordinates of the scatterers are uniformly and randomly generated in a rectangular area around the receiver and the transmitter, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S202, the random phase of a NLoS path is generated, and the random phase of a NLoS path follows a uniform distribution in [−π, π), which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S203, the angle spread of the NLoS path is generated, whose calculation formula is expressed as
where φAoDm(t) and φAoAm(t)denote an angle spread of an angle of departure (AoD) and an angle spread of an angle of arrival (AoA), respectively, AS(θAoD)and AS(θAoA)denote an angle spread coefficient for the AoD and an angle spread coefficient for the AoA, respectively, and YAoDm and YAoAm follow a standard normal distribution N(0,1), respectively. The angle spread of the AD and the angle spread of the AoA are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S204, the sine function lookup table is generated, and 65536 points are uniformly sampled within one cycle to be symmetric about a y-axis, and function values are amplified to 4096 times, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S205, the arctangent function lookup table is generated, and 524288 points are uniformly sampled around an origin point with an interval 1/65536 between each sampling point to be symmetric about the y-axis, and function values are amplified to 215/π times, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
Preferably, in Step S3, the angle distributions of the clusters are expressed as θAoDLoS(t) θAoALoS(t), θAoDi,n(t) and θAoAi,n(t), the amplitude distribution is expressed as HqpLoS(t), HqpSBi(t) and HqpDB(t); an angle of the clusters is determined by the coordinate of the transmitter, the coordinate of the receiver, and the coordinates of the scatterers; the amplitude is determined by the Rice factor, the total power, a proportion of a SB ray and a DB ray to a total scattering power on the NLoS path, the number of an i-th class scatterers at a time instant t, and the number of sub-paths in each cluster of the NLoS path, and Step S3 specifically includes the following steps.
In Step S301, the AD of all paths and the AoA of all paths are generated, whose calculation formulas are expressed as
where Si,nx(t), Txx(t) and Rxx(t) denote a horizontal coordinate of the n-th scatterer in the i-th class (i=1,2,3), a horizontal coordinate of the transmitter, and a horizontal coordinate of the receiver, respectively, and Si,ny(t), Txy(t)and Rxy(t)denote a vertical coordinate of the n-th scatterer in the i-th class, a vertical coordinate of the transmitter, and a vertical coordinate of the receiver, respectively.
In Step S302, a sub-path angle of the NLoS path is generated, whose calculation formulas are expressed as
where θAoDi,n,m(t)and θAoAi,n,m(t)denote an AoD of the m-th sub-path and an AoA of the m-th sub-path, respectively, φAoDm(t)and φAoAm(t) denote an angle spread value for the AoD of the m-th sub-path and an angle spread value for the AoA of the m-th sub-path, respectively, and φAoDi,n and φAoAi,n denote an average value for the AoDs of clusters passing through the n-th scatterer in the i-th class and an average value for the AoAs of the clusters passing through the n-th scatterer in the i-th class, respectively.
In Step S303, a time delay value is generated, whose calculation formula is expressed as
where, τLoS(t)denotes a time delay value for a LoS path, τnSBi(t) denotes a time delay value for a SB path cluster passing through the n-th scatterer in the i-th class, τn
In Step S304, Doppler phase values ϕLoS(t), ϕn,mSBi(t) and ϕn
where fLoS(t) denotes a Doppler frequency of the LoS path, fc denotes a carrier frequency; and {circumflex over (r)}TXLOS(t)=(cosθAoDLoS(t), sinθAoDLoS(t))
where {circumflex over (r)}TXLoS(t) and θRXLoS(t) denote a unit vector for the AoD of the LoS path and a unit vector for the AoA of the LoS path, respectively, and φLoS(t) denotes a Doppler phase of the LoS path; and
fn,mSBi(t) denotes a Doppler frequency of the m-th sub-path of the SB path passing through the n-th scatterer in the i-th class, and {right arrow over (v)}n
where {right arrow over (v)}n
where fn
where {circumflex over (r)}TX,n
In Step S305, an antenna phase value is generated, whose calculation formula is expressed as follows.
A relative coordinate {right arrow over (d)}Tx of a transmitter antenna is:
where dTxx denotes a horizontal ordinate of {right arrow over (d)}Tx and dTxy, denotes a vertical ordinate of {right arrow over (d)}Tx.
A phase difference ψTx(t) of the transmitter antenna is:
where {circumflex over (r)}Tx(t) denotes a unit vector for an AoD at the time instant t.
A relative coordinate {right arrow over (d)}Rx of the receiver antenna i:
where dRxx denotes a horizontal ordinate of {right arrow over (d)}Rx, dRxy denotes a vertical ordinate of {right arrow over (d)}Rx.
A phase difference ψRx(t) of the receiver antenna is:
where {circumflex over (r)}Rx(t) denotes a unit vector for an AoA at the time instant t.
A total antenna phase value ψ(t) is:
In Step S306, amplitude values are generated, whose calculation formulas are expressed as:
where, HqpLoS(t) denotes a channel impulse response amplitude value for a LoS path between the q-th receiving antenna and the p-th transmitting antenna, HqpSBi(t) denotes a channel impulse response amplitude value for a sub-path of a SB path passing through the scatterer in the i-th class located between the q-th receiving antenna and the p-th transmitting antenna, HqpDB(t) denotes a channel impulse response amplitude value for the sub-path of the DB path between the q-th receiving antenna and the p-th transmitting antenna, Kqp denotes a Rice factor of a p-q link, Pqp denotes a total power of the p-q link, ξSB
In Step S307, channel impulse response is generated, whose calculation formula is expressed as:
where hqpLoS(t,τ) denotes a channel impulse response for the LoS path between the q-th receiving antenna and the p-th transmitting antenna, hqpSB(t,τ) denotes the channel impulse response for the SB path between the q-th receiving antenna and the p-th transmitting antenna, hqpDB(t,τ) denotes a channel impulse response for the DB path between the q-th receiving antenna and the p-th transmitting antenna, fc denotes a carrier center frequency, τ denotes a time delay, ϕ denotes a Doppler phase, ψ denotes an antenna phase difference, φn,mSB
Preferably, in Step S4, formulas for the statistical characteristic specifically include followings:
In Step S401, a calculation formula of a time autocorrelation function TACF curve is expressed as:
where hqp(t,τ) denotes a channel impulse response between the q-th receiving antenna and the p-th transmitting antenna in a case where a time period is t and a time delay is τ, hq′p′(t,τ) denotes a channel impulse response between the q′-th receiving antenna and the p′-th transmitting antenna in a case where a time period is t and a time delay is τ;(·)* denotes a conjugate complex of(·)
In Step S402, a calculation formula of a spatial cross-correlation function(SCCF) curve is expressed as
In Step S403, a calculation formula of a delay power spectral density(PSD)curve is expressed as
Kqp, ξSB
The beneficial effects of the present disclosure are in the following.
The present disclosure can provide a method for designing a time-domain non-stationary V2V MIMO communication channel emulator, so as to accurately and stably test a V2V MIMO communication system.
In order to clarify the objectives, the technical solutions, and the advantages of the embodiments of the present disclosure to be clearer, the technical solutions in the embodiments of present disclosure will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are one part of the embodiments of the present disclosure, not all of them. Based on the embodiments in the present disclosure, all other embodiments obtained by a person skilled in the art without creative labor fall within the protection scope of the present disclosure.
With reference to
In Step S1, basic parameters for the V2V MIMO communication channel are determined.
Specifically, in this embodiment, c a method for establishing a geometry-based stochastic channel model (GBSM). Firstly, the application scenario is determined as V2V, and the initial coordinates of the transmitter and the receivers are determined as (8,8) and (50,50) at the same time. The carrier center frequency is set as 500 MHz, the antenna spacing distance between the transmitter and the receiver is set as 1 meter, the elevation angle and the horizontal angle of the transmitting antenna array and the receiving antenna array are set as 0 and 0, the motion velocity of the transmitter and the motion velocity of the receiver are set as 10 m/s and 5 m/s, respectively, and the direction of the motion is that the elevation angle is 0 and the horizontal angle is 0. Kqp=1, ξSB
In Step S2, a V2V 2D time-domain non-stationary communication channel environment is generated by using a MATLAB, and the environment specifically includes the number of scatterers and positions of the scatterers, a random phase of a NLoS path, an angle spread of the NLoS path, a sine function lookup table, and an arctangent function lookup table.
Specifically, in this embodiment, the V2V communication channel model is adopted in the model, and the schematic diagram of the specific communication channel model is illustrated in
A uniform linear array is adopted at the antenna terminal, which can be placed arbitrarily in a 2D space. For simplicity, only one cluster in each of LoS path, SB path, and DB path is shown in the drawings. Three classes of the scatterers are located on a circle with the transmitter as the center, a circle with the receiver as the center, and an ellipse representing the street environment, respectively, and only one scatterer of all three classes of the scatterers is shown in the drawings. {right arrow over (v)}S
More specifically, in this embodiment, generating a V2V 2D time-domain non-stationary communication channel environment specifically includes the following steps.
In Step S201, the numbers of the scatterers and positions of the scatterers are generated.
An average survival probability of effective scatterers within the time period Δt is expressed as
where γR denotes a generation rate of the scatterers, Pm denotes a motion percentage, {right arrow over (v)}S
where λ denotes a parameter for a Poisson distribution probability distribution function; and γG denotes a disappearance rate of the scatterers. By combining the above two formulas, the average number of scatterers can be obtained:
Eventually, the numbers of the scatterers within each time period are obtained by calculation, which are generated through a MATLAB, and are sequentially stored in a file with a coe suffix. Position coordinates of the scatterers are uniformly and randomly generated in a rectangular area around the receiver and the transmitter, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S202, the random phase of a NLoS path is generated.
The random phase of a NLoS path follows a uniform distribution in [−π,π), which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S203, the angle spread of the NLoS path is generated.
Calculation formula of the angle spread of the NLoS path is expressed as
where AS(θAoD)and AS(θAoA)denote an angle spread coefficient for the AoD and an angle spread coefficient for the AoA, respectively, and YAoDm and YAoAm follow a standard normal distribution N(0,1), respectively, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S204, the sine function lookup table is generated.
65536 points are uniformly sampled within one cycle to be symmetric about a y-axis, and function values are amplified to 4096 times, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S205, the arctangent function lookup table is generated.
524288 points are uniformly sampled around an origin point with an interval 1/65536 between each sampling point to be symmetric about the y-axis, and function values are amplified to 215/π times, which are generated through the MATLAB, and are sequentially stored in the file with a coe suffix.
In Step S3, parameters generated in Step S2 are imported into a hardware simulation platform to calculate the communication channel parameters of the clusters, such as an angle distribution and an amplitude distribution, a Verilog code is written for running, and a channel impulse response of the time-domain non-stationary V2V MIMO communication channel is eventually obtained by calculation.
In this embodiment, Step S3 specifically includes the following steps.
In Step S301, the AoD of all paths and the AoA of all paths are generated.
The calculation formulas of the AoD of all paths and the AoA of all paths are expressed as
where Si,nx(t), Txx(t) and Rxx(t) denote a horizontal coordinate of the n-th scatterer in the i-th class(i=1,2,3), a horizontal coordinate of the transmitter, and a horizontal coordinate of the receiver, respectively, and Si,ny(t), Txy(t) and Rxy(t) denote a vertical coordinate of the n-th scatterer in the i-th class, a vertical coordinate of the transmitter, and a vertical coordinate of the receiver, respectively.
In Step S302, a sub-path angle of the NLoS path is generated.
The calculation formulas of a sub-path angle of the NLoS path are expressed as
where φAoDm(t) and φAoAm(t) denote an angle spread value for the AoD of the m-th sub-path and an angle spread value for the AoA of the m-th sub-path, respectively, and θAoDi,n and θAoAi,n denote an average value for the AoDs of clusters passing through the n-th scatterer in the i-th class and an average value for the AoAs of the clusters passing through the n-th scatterer in the i-th class, respectively.
In Step S303, a time delay value is generated.
The calculation formula of a time delay value is expressed as
where, τLoS(t) denotes a time delay value for a LoS path, τnSB
In Step S304, Doppler phase values are generated.
The calculation formulas of the Doppler phase values are expressed as
where fLoS(t) denotes a Doppler frequency of the LoS path, fc denotes a carrier frequency; and {circumflex over (r)}TxLoS(t)=(cosθAoDLoS(t),sinθAoDLoS(t))
where {circumflex over (r)}TxLoS(t) and {circumflex over (r)}RxLoS(t) denote a unit vector for the AoD of the LoS path and a unit vector for the AoA of the LoS path, respectively, and ϕLoS(t) denotes a Doppler phase of the LoS path; and
fn,mSB
where {right arrow over (v)}n
where fn
where {circumflex over (r)}Tx,n
In Step S305, an antenna phase value is generated.
The calculation formula of the antenna phase value is expressed as follows.
A relative coordinate {right arrow over (d)}Tx of a transmitter antenna is:
where dTxx denotes a horizontal ordinate of {right arrow over (d)}Tx and dTxy denotes a vertical ordinate of {right arrow over (d)}Tx
A phase difference ψTx(t) of the transmitter antenna is:
where {circumflex over (r)}Tx(t) denotes a unit vector of an AoD at the time instant t.
A relative coordinate {right arrow over (d)}Rx of the receiver antenna i:
where dix denotes a horizontal ordinate of {right arrow over (d)}Rx, dRxy denotes a vertical ordinate of {right arrow over (d)}Rx. A phase difference ψTx(t) of the receiver antenna is:
where {circumflex over (r)}Rx(t) denotes a unit vector for an AoA at the time instant t.
The calculation formula of the total antenna phase value ψ(t) is expressed as:
In Step S306, amplitude values are generated.
The calculation formulas of the amplitude values are expressed as:
where, HqpLoS(t) denotes channel impulse response amplitude value for a LoS path between the q-th receiving antenna and the p-th transmitting antenna, HqpSB
Kqp, ξSB
In Step S307, channel impulse response is generated.
The calculation formula of the channel impulse response is expressed as
where hqpLoS(t,τ) denotes a channel impulse response for the LoS path between the q-th receiving antenna and the p-th transmitting antenna, hqpSB(t,τ) denotes the channel impulse response for the SB path between the q-th receiving antenna and the p-th transmitting antenna, hqpDB(t,τ) is a channel impulse response for the DB path between the q-th receiving antenna and the p-th transmitting antenna, fc denotes a carrier center frequency, τ denotes a time delay, ϕ denotes a Doppler phase, ψ denotes an antenna phase difference, φn,mSB
In Step S4, a comparison is performed with a statistical characteristic of a theoretical communication channel model, and an appropriate hardware diagram of a communication channel emulator is designed.
The specific hardware block diagram is illustrated in
In Step S401, a calculation formula of a time autocorrelation function TACF curve is expressed as:
where hqp(t,τ)denotes a channel impulse response between the q-th receiving antenna and the p-th transmitting antenna in a case where a time period is t and a time delay is τ, hq′p′(t,τ) denotes a channel impulse response between the q′-th receiving antenna and the p′-th transmitting antenna in a case where a time period is t and a time delay is τ; (·)* denotes a conjugate complex of(·).
In Step S402, a calculation formula of a SCCF curve is expressed as
In Step S403, a calculation formula of a delay PSD curve is expressed as
In order to verify the correctness of the method provided in this embodiment, experiments are conducted, and specifically lie as follows.
The TACF between the transmitting antenna and the receiving antenna at different time intervals are verified, and the results are as illustrated in
The SCCF between the receiving antennas at different antenna intervals are verified, and the results are as illustrated in
The delay PSD of channel impulse response at different antenna intervals are verified, and the results are as illustrated in
In summary, provided in the present disclosure is a method for designing a time-domain non-stationary V2V MIMO communication channel emulator, which can describe the fading characteristics of macro cell, micro cell, and micro-micro cell, as well as the birth and death process of the clusters. The statistical characteristics of the simulations have important reference value for the designs of time-domain non-stationary communication channel emulators.
The unspecified parts in the present disclosure are all the common sense for a person skilled in the art. The preferred specific embodiments of the present disclosure are described in details in above. It should be understood that various amendments and changes can be made by an ordinary person skilled in the art according to the concept of the present disclosure with no creative efforts. Therefore, all technical solutions that can be obtained by a person skilled in the art on a basis of the prior art according to the concept of the present disclosure through the logical analysis, reasoning, or limited experiments should be within the protection scope determined by the claims.
Number | Date | Country | Kind |
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2023110930773 | Aug 2023 | CN | national |