Method of transmitting and receiving beamforming signal and signal transceriver for implementing the same

1 . A signal transmitting method in a signal transmitter, comprising:

splitting each of plural message streams to be transmitted to a plurality of receivers into a common message stream and at least one private message stream in a unit of a message stream;

combining a plurality of common message streams for the plurality of receivers to generate a common stream;

encoding the common stream and private message streams for the plurality of receivers to generate an encoded common stream and encoded private message streams;

linearly precoding the encoded common stream and the encoded private message streams to adjust amplitudes and phases of symbols such that power is distributed in a predetermined manner between the encoded common stream and the encoded private message streams and generate precoded signals; and

converting the precoded signals into a plurality of RF signals, adjusting phases of the plurality of RF signals, and outputting the plurality of phase-adjusted RF signals through a plurality of multi-input multiple-output (MIMO) antennas,

wherein linearly precoding the encoded common stream and the encoded private message streams comprises:

generating a beamforming matrix for a private stream by generating a digital beamforming matrix for the private stream by a linear combination of a singular value decomposition (SVD) beamforming matrix and a zero forcing (ZF) beamforming matrix and normalizing a size of each column of the digital beamforming matrix to 1; and

determining a right unitary matrix obtained by a singular value decomposition of an effective channel matrix of each user as a digital beamforming matrix for the common stream.

2 . The signal transmitting method of claim 1 , wherein a sum of a number of the common message streams and a number of the private message streams for each of the plurality of receivers is determined to be smaller than or equal to a number of RF chains of a corresponding receiver,

wherein a sum of a number of common message streams for all the plurality of receivers and a number of private message streams for all the plurality of receivers is determined to be smaller than or equal to a number of RF chains of the signal transmitter.

3 . The signal transmitting method of claim 2 , further comprising:

before splitting each of the plural message streams to be transmitted, determining the receivers and adjusting a proportion of the common data stream and the private data streams according to a signal-to-noise ratio of a transmission channel.

4 . The signal transmitting method of claim 1 , wherein converting the precoded signals and outputting the plurality of phase-adjusted RF signals comprises:

setting an entire analog beamforming matrix by performing a singular-value decomposition (SVD) of an entire channel matrix to obtain a right unitary matrix and taking only phase values from elements of the right unitary matrix.

5 . The signal transmitting method of claim 1 , wherein converting the precoded signals and outputting the plurality of phase-adjusted RF signals comprises:

setting an analog beamforming matrix by multiplying a beamforming matrix for a fully-connected architecture by a block diagonal identity matrix determined according to a sub-connected architecture.

6 . The signal transmitting method of claim 1 , wherein converting the precoded signals and outputting the plurality of phase-adjusted RF signals comprises:

setting an analog beamforming matrix by performing a singular-value decomposition (SVD) of a channel matrix for a channel of all users connected to each of sub-connected arrays to obtain a right unitary matrix and taking only phase values from elements of the right unitary matrix.

7 . The signal transmitting method of claim 1 , wherein converting the precoded signals and outputting the plurality of phase-adjusted RF signals comprises:

setting an analog beamforming matrix for a channel connected to each sub-connected array by selecting angles of signal paths having strongest intensity as many as a number of data streams and aligning beam formed by the analog beamforming matrix to at least one direction corresponding to the angles.

8 . A signal receiving method by a signal receiver to receive a signal transmitted by a signal transmitter and reconstruct a message stream for the signal receiver, comprising:

acquiring a receive signal through a multiple-input multiple-output (MIMO) antenna;

decoding the receive signal to reconstruct a common stream, the common stream being generated by the signal transmitter combining a plurality of common message streams for a plurality of signal receivers including the signal receiver;

separating a common message stream for the signal receiver from the common stream while excluding common message stream irrelevant to the signal receiver;

acquiring a private stream signal component by subtracting a contribution of the common message stream from the receive signal;

decoding the private stream signal component to recover a private message stream for the signal receiver; and

combining the common message stream for the signal receiver and the private message stream for the signal receiver to reconstruct the message stream for the signal receiver,

wherein in the receive signal, power is distributed in a predetermined manner between the common stream and a plurality of private message streams for the plurality of signal receivers, and

wherein the common stream and the private message stream are included in the signal through encoding and linear precoding, and the linear precoding is performed at the signal transmitter by:

generating a beamforming matrix for a private stream by generating a digital beamforming matrix for the private stream through a linear combination of a singular value decomposition (SVD) beamforming matrix and a zero-forcing (ZF) beamforming matrix, and normalizing a magnitude of each column of the digital beamforming matrix to 1; and

determining, as a digital beamforming matrix for a common stream, a right unitary matrix obtained by a singular value decomposition of an effective channel matrix of each user.

9 . The signal receiving method of claim 8 , wherein decoding the receive signal to reconstruct the common stream comprises:

decoding the receive signal while treating signal components caused by the private message stream and irrelevant to the signal receiver as an interference or noise.

10 . The signal receiving method of claim 8 , wherein decoding the private stream signal component to recover the private message stream for the signal receiver comprises:

decoding the private stream signal component while treating signal components for other signal receivers in the private stream signal component as an interference or noise.

11 . The signal receiving method of claim 8 , wherein acquiring the private stream signal component by subtracting the contribution of the common message stream from the receive signal comprises:

re-encoding a reconstructed common message stream, precoding a re-encoded common message stream, and equalizing a precoded message under a condition simulating an actual channel condition to generate the contribution of the common message stream from the receive signal.

12 . A signal transmitting apparatus, comprising:

a memory having program instructions stored therein; and

a processor coupled to the memory and configured to execute the program instructions stored in the memory,

wherein the program instructions, when executed by the processor, are configured to cause the processor to:

split each of plural message streams to be transmitted to a plurality of receivers into a common message stream and at least one private message stream in a unit of a message stream;

combine a plurality of common message streams for the plurality of receivers to generate a common stream;

encode the common stream and private message streams for the plurality of receivers to generate an encoded common stream and encoded private message streams;

linearly precode the encoded common stream and the encoded private message streams to adjust amplitudes and phases of symbols such that power is distributed in a predetermined manner between the encoded common stream and the encoded private message streams and generate precoded signals; and

convert the precoded signals into a plurality of RF signals, adjust phases of the plurality of RF signals, and output the plurality of phase-adjusted RF signals through a plurality of multi-input multiple-output (MIMO) antennas,

wherein the program instructions causing the processor to linearly precode the encoded common stream and the encoded private message streams are configured to cause the processor to:

generate a beamforming matrix for a private stream by generating a digital beamforming matrix for the private stream by a linear combination of a singular value decomposition (SVD) beamforming matrix and a zero forcing (ZF) beamforming matrix and normalizing a size of each column of the digital beamforming matrix to 1; and

determine a right unitary matrix obtained by a singular value decomposition of an effective channel matrix of each user as a digital beamforming matrix for the common stream.

13 . The signal transmitting apparatus of claim 12 , wherein a sum of a number of the common message streams and a number of the private message streams for each of the plurality of receivers is determined to be smaller than or equal to a number of RF chains of a corresponding receiver,

wherein a sum of a number of common message streams for all the plurality of receivers and a number of private message streams for all the plurality of receivers is determined to be smaller than or equal to a number of RF chains of the signal transmitter.

14 . The signal transmitting apparatus of claim 12 , wherein the program instructions causing the processor to convert the precoded signals and output the plurality of phase-adjusted RF signals are configured to cause the processor to:

set an entire analog beamforming matrix by performing a singular-value decomposition (SVD) of an entire channel matrix to obtain a right unitary matrix and taking only phase values from elements of the right unitary matrix.

15 . The signal transmitting apparatus of claim 12 , wherein the program instructions causing the processor to convert the precoded signals and output the plurality of phase-adjusted RF signals are configured to cause the processor to:

set an analog beamforming matrix by multiplying a beamforming matrix for a fully-connected architecture by a block diagonal identity matrix determined according to a sub-connected architecture.

16 . The signal transmitting apparatus of claim 12 , wherein the program instructions causing the processor to convert the precoded signals and output the plurality of phase-adjusted RF signals are configured to cause the processor to:

set an analog beamforming matrix by performing a singular-value decomposition (SVD) of a channel matrix for a channel of all users connected to each of sub-connected arrays to obtain a right unitary matrix and taking only phase values from elements of the right unitary matrix.

17 . The signal transmitting apparatus of claim 12 , wherein the program instructions causing the processor to convert the precoded signals and output the plurality of phase-adjusted RF signals are configured to cause the processor to:

set an analog beamforming matrix for a channel connected to each sub-connected array by selecting angles of signal paths having strongest intensity as many as a number of data streams and aligning beam formed by the analog beamforming matrix to at least one direction corresponding to the angles.

18 . The signal transmitting apparatus of claim 12 , wherein the program instructions are configured to further cause the processor to:

before splitting each of the plural message streams to be transmitted, determine the receivers and adjusting a proportion of the common data stream and the private data streams according to a signal-to-noise ratio of a transmission channel.