Two-way relay transmission method and apparatus applied to multi-input multi-output communication systems

摘要

A two-way relay transmission apparatus applied to multi-input multi-output communication systems that combines signals received from the terminals and performs a modulo operation to the combined signal to concentrate the signal points towards the center of the constellation. And then, the modulo version of the combined signal is broadcasted. As a result, the peak and average relay transmission powers can be reduced.

主权项

1. A two-way relay transmission method applied to multi-input multi-output communication systems, comprising:
receiving a first signal transmitted from at least one of two terminals by a relay apparatus, and combining the first signal; and performing a modulo operation to the combined first signal by the relay apparatus to produce a second signal, and broadcasting the second signal, wherein the modulo operation is represented by equation (1):
xRk=αMc mod(βyRk+C,B)  (1) wherein, xRk is the second signal broadcasted by the relay apparatus at time k, αM is a scaling factor of the form of a diagonal matrix, β is a phase rotation factor of the form of a diagonal matrix, yRk is the first signal received by the relay apparatus at time k, C is an offset vector, B is the modulus vector, and the cmod function is a function having a first complex vector variable and a second complex vector variable, with the function performing a symmetric complex modulo operation on at least one complex element x of the first complex vector variable according to a complex element of the second complex vector variable at the corresponding element position, with the symmetric complex modulo operation on at least one complex element x of the first complex vector variable being represented by equation (2):
c mod(x,B)=mod({x},B)+j mod({x},B)  (2) wherein, R{ } indicates the real part of the quantity in the braces, ℑ{ } indicates the imaginary part of the quantity in the braces, B is the complex element of the second complex vector variable at the position corresponding to the position of the complex element x where B is greater than or equal to a shift value of a duplicated rotated signal footprint, with the shift value being obtained by rotating a footprint of a signal received at the relay apparatus for a signal transmitted by one of the terminals by an angle θ, duplicating the rotated footprint once, and shifting the duplicated rotated signal footprint such that the distance between any point in the shifted duplicated rotated signal footprint and any point in the original rotated signal footprint is greater than or equal to Sim, wherein i is an index of the terminal, Sim is a minimum of Ai0|hi0|, Ai1|hi1|, . . . , Ai(Q-1)|hi(Q-1)|, Q is a number of antennas of the terminal, Aij is the minimum distance of the signal points in the signal constellation transmitted from the transmitting antenna j of the terminal, hij represents the channel coefficients, and j is in 0, 1, . . . , Q−1 for antenna indexing; and the mod function is a function having a first real variable and a second real variable, with the function taking a symmetric real modulo of the arbitrary first real variable y according to the second real variable, with the symmetric real modulo operation being represented by equation (3):
mod(y,B)=[(y+B/2)%B]−B/2  (3) wherein % is an asymmetric real modulo operation mathematically defined as a%b=a−└a/b┘b, where a and b are two arbitrary real numbers, and └a/b┘ means the maximum integer smaller than or equal to a/b.