| CPC H04B 7/0617 (2013.01) [H04B 7/06 (2013.01); H04B 7/086 (2013.01)] | 12 Claims |
|
1. A broadband millimeter wave beam tracking method based on vehicle movement trajectory recognition, wherein specific steps are as follow:
step 1, in a vehicle-to-vehicle (V2V) communication system, constructing a simplified dynamic movement scenario of vehicle communication;
step 2, for a moment k, calculating a distance dTX,RX[k] between two vehicles in communication in a horizontal direction; initially, k=0;
step 3, deriving a rough estimate of a transmitting end beam angle AoD (Angle-of-Departure) and a rough estimate of a receiving end beam angle AoA (Angle-of-Arrival) at the moment k, based on positions of the two vehicles in communication at the moment k, in combination with attitude information of the vehicles;
a binary variable group φazi[k]=[ϕazi[k], θazi[k]]T, ϕazi[k] represents a horizontal component of a beam angle AoD of a transmitting end vehicle A at the moment k, θazi[k] represents a horizontal component of a beam angle AoA of a receiving end vehicle B at the moment k;
 θkazi is a rough estimate of the beam angle AoA at the moment k; ϕkazi is a rough estimate of the beam angle AoD at the moment k; βk is a steering angle between a transmitting antenna and a receiving antenna when a vehicle turns at the moment k; (pTX, x[k], pTX, y[k]) is a position of the transmitting end vehicle A at the moment k; (pRX, x[k], pRX, y[k]) is a position of the receiving end vehicle B at the moment k: w[k] is a sudden change rate of the beam angle AoD of the transmitting end vehicle A at the moment k; Δt represents a time interval between adjacent moments k and k−1; δφazi[k] represents a smooth change rate of the beam angle AoD in a horizontal direction;
a binary variable group φele[k]=[ϕele[k], θele[k]]T, ϕele[k] represents a pitch component of the beam angle AoD at the moment k, θele[k] represents a pitch component of the beam angle AoA at the moment k;
 θl,kele is a rough estimate of the beam angle AoA on a lth path at the moment k; ϕl,kele is a rough estimate of the beam angle AoD on the lth path at the moment k; |HTX−HRX| is a height difference of vehicles, HTX is a height of the transmitting end vehicle A; HRX is a height of the receiving end vehicle B; δφazi represents a smooth change rate of the beam angle AoD in a pitch direction;
step 4, at the moment k=0, the transmitting end vehicle A calculating a forming vector f0 of a transmitting beam and a forming vector w0 of a receiving beam based on the rough estimates of the beam angles AoD and AoA, and transmitting a pilot signal q;
calculating the beam forming vector f0 by using an estimate at(ϕ0azi, ϕ0ele) of a transmitting beam vector;
calculating the beam forming vector w0 by using an estimate ar(θ0azi, θ0ele) of a receiving beam vector;
step 5, starting from the moment k=1, judging whether the sudden rate of the beam angle of the transmitting end vehicle A meets w(n)[k]≠0, and, if so, moving on to step 6, otherwise, moving on to step 7;
step 6, a current state of the transmitting end vehicle A is in a steering sudden change mode, calculating an observation value ŷk of a received signal at the moment k with an equation as follow:
ŷk=ραkwH(θazi, θele)ar(θkazi, θkele)atH(ϕkazi, ϕkele)f(ϕazi, ϕele)q±ñk;
wherein, ραk is a channel gain of a path; wH(θazi, θele) represents a transpose matrix of a forming vector of a receiving beam; f(ϕazi, ϕele) represents a forming vector of a transmitting beam; ar(θkazi, θkele) represents an estimate of the receiving beam vector; alH(ϕkazi, ϕkele) represents a transpose matrix of an estimate of the transmitting beam vector; ñ[k] represents a white Gaussian noise vector during observation;
step 7, the current state of the transmitting end vehicle A is in a smooth change mode, calculating an observation value pk of the received signal at the moment k with an equation as follows:
pk=ραkwk−1Har(θkazi,θkele)atH(ϕkazi,ϕkele)fk−1q+ñk
wk−1 is a forming vector of a receiving beam at the moment k−1; fk−1 is a forming vector of a transmitting beam at the moment k−1;
step 8, inputting the observation value pk or the observation value ŷk into an improved particle filter algorithm for fine beam estimation, to obtain optimal values xk of the beam angles AoD and AoA and an estimation mean square error k of a beam angle; specifically,
first, starting from n=1 for particles, when n<Np, generating particles x*(n)[k]∈N(xk,uk), and assigning a weight
 Np being a total number of particles;
then, calculating an angle sudden change rate w(n)[k] based on a random process ck of a steering command and updating a state equation:
 wherein,
 represents a white Gaussian noise vector: P=diag(ρ, φ represents a diagonal matrix of channel coefficients, represents a channel coefficient; E=diag(1, 1, 1, 1) represents a diagonal matrix of beam coefficients; R=diag(mϕ, mθ, nφ, nθ) represents a diagonal matrix of correlation coefficients of the beam angles AoD and AoA, {mϕ, mθ, nφ, nθ}∈(0,1); Q=diag (Δt, Δt, Δt, Δt) represents a diagonal matrix of correlation coefficients of iteration time differences; U=diag[Δt, Δt, 0, 0]T represents a diagonal matrix of correlation coefficients;
then, executing different particle weight updating strategies based on whether an angle change w(n)[k] is 0, if the condition w(n)[k]≠0 is met, it is determined that the current state is in a steering sudden change mode: otherwise, it is determined that the current state is in a smooth change mode;
when it is in the smooth change mode, performing weight updating on the particles with the observation value pk with an equation as follows:
w*(n)[k]=w(n)[k]
 (pk|s(n)[k]);w(n)[k] characterizes an initial weight of particles before updating the particles at the moment k; s(n)[k]
 {x(n)[k], w(n)[k]} characterizes a state equation comprising the channel state vector, the smooth change rate of the beam angle and the sudden change rate of the beam angle at the moment k;when it is in the steering sudden change mode, performing weight updating on the particles with the observation value ŷk with an equation as follows:
w*(n)[k]=w(n)[k]
 (ŷk|s(n)[k]);then, performing weight normalization and resampling by using the updated particles:
 x(j)[k] represents a channel state vector of a jth particle; w(j)[k] represents a particle weight of the jth particle;
finally, obtaining optimal values of the beam angles AoD and AoA by using the channel state vector and the updated particle weight:
 after obtaining an optimal value x*(n)[k]∈N(xk, uk) corresponding to a current particle, incrementing n by 1, and selecting a next particle to repeat the above process;
step 9, re-estimating a forming vector fk of a transmitting beam and a forming vector wk of a receiving beam by using the beam state optimal value xk and the estimation mean square error uk of the beam angle at the moment k, and transmitting the estimate of the forming vector fk of the transmitting beam to the transmitting end vehicle A for adjustment, so as to transmit a pilot signal q at the moment k+1 based on the adjusted forming vector fk of the transmitting beam;
step 10, returning to step 3, continuing to adjust the beam forming vector of each moment, until an error between an adjusted beam forming vector and an actual beam satisfies a set threshold range, so as to complete beam tracking.
|