A processor coupled to a first communication device produces and transmits a first encoded vector and a second encoded vector to a second communication device via a communication channel that applies a channel transformation to the encoded vectors during transmission. A processor coupled to the second communication device receives the transformed signals, constructs a matrix based on the transformed signals, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. A first symbol of the second encoded vector and a second symbol of the second encoded vector are sent to the first communication device for identification of the message.

Provided is a precoding method for generating, from a plurality of baseband signals, a plurality of precoded signals to be transmitted over the same frequency bandwidth at the same time, including the steps of selecting a matrix F[i] from among N matrices, which define precoding performed on the plurality of baseband signals, while switching between the N matrices, i being an integer from 0 to N−1, and N being an integer at least two, generating a first precoded signal z1 and a second precoded signal z2, generating a first encoded block and a second encoded block using a predetermined error correction block encoding method, generating a baseband signal with M symbols from the first encoded block and a baseband signal with M symbols the second encoded block, and precoding a combination of the generated baseband signals to generate a precoded signal having M slots.

A system includes first and second sets of communication devices. A processor coupled to the first set of communication devices produces a first encoded vector and transmits the first encoded vector to the second set of communication devices via a communication channel that applies a channel transformation to the first encoded vector during transmission. A processor coupled to the second set of communication devices receives the transformed signal, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. The second encoded vector is sent to the first set of communication devices for identification of the message.

A transmission method for transmitting a first modulated signal and a second modulated signal in the same frequency at the same time. Each signal has been modulated according to a different modulation scheme. The transmission method applies precoding on both signals using a fixed precoding matrix, applies different power change to each signal, and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.

A system includes first and second sets of communication devices. A processor coupled to the first set of communication devices produces a first encoded vector and transmits the first encoded vector to the second set of communication devices via a communication channel that applies a channel transformation to the first encoded vector during transmission. A processor coupled to the second set of communication devices receives the transformed signal, detects an effective channel thereof, and identifies left and right singular vectors of the effective channel. A precoding matrix is selected from a codebook of unitary matrices based on a message, and a second encoded vector is produced based on a second known vector, the precoding matrix, a complex conjugate of the left singular vectors, and the right singular vectors. The second encoded vector is sent to the first set of communication devices for identification of the message.

A transmission method for transmitting a first modulated signal and a second modulated signal in the same frequency at the same time. Each signal has been modulated according to a different modulation scheme. The transmission method applies precoding on both signals using a fixed precoding matrix, applies different power change to each signal, and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.

Precoding coefficients can be compressed based on user equipment signal interference to noise ratio or path loss in front haul cloud radio access network systems. For example, a baseband unit can compute a precoder matrix from an estimated channel associated with an uplink signal. Once the baseband unit computes the channel, it can determine the coefficients for the linear combination of the basis vectors, which are known at the baseband unit and the radio unit as well. The baseband unit can estimate the path loss and the signal interference to noise ratio and determine the basis vectors. The baseband unit can then compress the coefficients and transmit the coefficients to the radio unit. When the radio unit receives the compressed coefficients, the radio unit can reconstruct the precoder matrix and apply to reference signals and data traffic channels.

Provided is a precoding method for generating, from a plurality of baseband signals, a plurality of precoded signals to be transmitted over the same frequency bandwidth at the same time, including the steps of selecting a matrix F[i] from among N matrices, which define precoding performed on the plurality of baseband signals, while switching between the N matrices, i being an integer from 0 to N1, and N being an integer at least two, generating a first precoded signal z1 and a second precoded signal z2, generating a first encoded block and a second encoded block using a predetermined error correction block encoding method, generating a baseband signal with M symbols from the first encoded block and a baseband signal with M symbols the second encoded block, and precoding a combination of the generated baseband signals to generate a precoded signal having M slots.

This disclosure provides methods, devices and systems for obtaining and providing channel feedback. In some implementations, a beamformee provides channel feedback to a beamformer that enables the beamformer to construct and independently precode two or more different sets of spatial streams for transmission to the beamformee. The independent precoding of the different sets of spatial streams ensures that the decodings of the different sets of spatial streams may be decoupled from one another at the beamformee. To provide the channel feedback, the beamformee partitions a channel estimate into two or more sub-estimates prior to performing a channel decomposition. In some implementations, the beamformee determines null-space-based projections of the sub-estimates before performing the channel decomposition. The determination of the null-space-based projections enables the beamformee to perform independent decompositions of the multiple channel sub-estimates to determine multiple respective feedback matrices, which are then assembled to provide the channel feedback to the beamformer. The channel feedback is then reconstructed and disassembled by the beamformer to perform the independent precoding of the different sets of spatial streams.

Embodiments can provide a precoding matrix indicating method, a precoding matrix determining method, a receive end device, and a transmit end device. In the precoding matrix indicating method, component matrices of an ideal precoding matrix and a weight of each component matrix can be determined based on at least one basic codebook. A dimension of each component matrix is the same as a dimension of the ideal precoding matrix, and a column vector of each component matrix is selected from column vectors of one of the at least one basic codebook. A precoding matrix indicator can be sent. The precoding matrix indicator can indicate the component matrices and the weight of each component matrix. With this, an ideal precoding matrix is approximately represented in a form of a weighted sum of a plurality of component matrices so that feedback overheads caused by feeding back a precoding matrix can be reduced.