A method and apparatus for data transmission in a cellular system are disclosed herein In one embodiment, the method comprises receiving transmissions of uplink pilot signals made in each slot, by a number of UEs, over the radio resource elements in slots that are allocated for uplink pilot transmission, wherein the number of UEs in the vicinity of at least one base station exceeds the number of radio resource elements that have been allocated for uplink pilot transmission in the slot; estimating large-scale radio-channel propagation strengths of a plurality of nearby UEs to a base station; estimating radio-propagation channel coefficients between each base-station antenna and each UE, in a subset of UEs in the plurality of nearby UEs that have large-scale radio-channel propagation strengths to the base station that are stronger than those UEs in the plurality of nearby UEs not part of the subset; and transmitting to in-cell UEs via multi-user beamforming, including suppressing interference to one or more nearby out-of-cell UEs that are part of the plurality of nearby UEs.

A method and apparatus are provided for reducing the number of pilot symbols within a MIMO-OFDM communication system, and for improving channel estimation within such a system. For each transmitting antenna in an OFDM transmitter, pilot symbols are encoded so as to be unique to the transmitting antenna. The encoded pilot symbols are then inserted into an OFDM frame to form a diamond lattice, the diamond lattices for the different transmitting antennae using the same frequencies but being offset from each other by a single symbol in the time domain. At the OFDM receiver, a channel response is estimated for a symbol central to each diamond of the diamond lattice using a two-dimensional interpolation. The estimated channel responses are smoothed in the frequency domain. The channel responses of remaining symbols are then estimated by interpolation in the frequency domain.

A modified orthogonal frequency-division multiplexing (OFDM) communication system based on virtual decomposition of the channel is proposed. The system is fully compatible with standard OFDM transmitters and maintains several blocks of standard OFDM receivers. The proposed approach achieves also incoherent reception of multicarrier signals even with a simple autocovariance DPSK detector. This novel system substantially surpasses the performance of current approaches while requiring low computational complexity. Two preferred embodiments are described; one with coherent reception using pilot signals, and the second with incoherent receiver of differentially encoded signals.

The embodiments herein use a factorization based technique for determining filter coefficients for a subset of the subcarriers in a wireless frequency band. Once the filter coefficients for the subset of the subcarriers are calculated, the network device uses these filter coefficients to identify the filter coefficients in a neighboring subcarrier. To do so, the network device uses pseudo-inverse iteration to convert the already calculated filter coefficients into filter coefficients for a neighboring subcarrier. The network device can repeat this process for the next set of neighboring subcarriers until all the filter coefficients have been calculated.

Disclosed in an embodiment of the disclosure is an interference rejection combining (IRC) method supporting transmit diversity, in which an N*N interference and noise covariance matrix corresponding to one subcarrier is generated from signals, in a transmit diversity mode, received at cell reference signal (CRS) resource positions via N receiving antennas, where N is greater than or equal to 3; Cholescy decomposition and upper triangular matrix inversion is performed on the N*N interference and noise covariance matrix to obtain an N*N block matrix; the N*N block matrix is expanded to a 2N*2N noise whitening matrix; and the received signals and channel estimation values are whitened according to the noise whitening matrix, and the whitened received signals and channel estimation values used to obtain a minimum mean square error-IRC (MMSE-IRC) processing result. Also disclosed are an IRC device supporting the transmit diversity, and a computer storage medium.

A method, network node and wireless transceiver, for implementing iterative downlink passive intermodulation (PIM) spatial avoidance algorithms are provided. According to one aspect, a method in a wireless transceiver includes determining an uplink signal power. The method also includes determining an estimate of a downlink PIM subspace that minimizes a cost function that depends on the uplink signal power and a previous estimate of the downlink PIM subspace. The method further includes applying a correction to a downlink antenna signal to reduce the PIM, the correction being based at least in part on the estimate of the downlink PIM subspace

A method and apparatus are provided for reducing the number of pilot symbols within a MIMO-OFDM communication system, and for improving channel estimation within such a system. For each transmitting antenna in an OFDM transmitter, pilot symbols are encoded so as to be unique to the transmitting antenna. The encoded pilot symbols are then inserted into an OFDM frame to form a diamond lattice, the diamond lattices for the different transmitting antennae using the same frequencies but being offset from each other by a single symbol in the time domain. At the OFDM receiver, a channel response is estimated for a symbol central to each diamond of the diamond lattice using a two-dimensional interpolation. The estimated channel responses are smoothed in the frequency domain. The channel responses of remaining symbols are then estimated by interpolation in the frequency domain.

Disclosed in an embodiment of the disclosure is an interference rejection combining (IRC) method supporting transmit diversity, in which an N*N interference and noise covariance matrix corresponding to one subcarrier is generated from signals, in a transmit diversity mode, received at cell reference signal (CRS) resource positions via N receiving antennas, where N is greater than or equal to 3; Cholescy decomposition and upper triangular matrix inversion is performed on the N*N interference and noise covariance matrix to obtain an N*N block matrix; the N*N block matrix is expanded to a 2N*2N noise whitening matrix; and the received signals and channel estimation values are whitened according to the noise whitening matrix, and the whitened received signals and channel estimation values used to obtain a minimum mean square error-IRC (MMSE-IRC) processing result. Also disclosed are an IRC device supporting the transmit diversity, and a computer storage medium.

The present invention discloses a channel estimation method, apparatus, and device and a multichannel microwave communications system. According to the channel estimation method, a first vector group corresponding to a transmit end and a second vector group corresponding to a receive end are first obtained according to a transmit-receive array size; then a subchannel estimation procedure is performed multiple times according to the transmit-receive array size, the first vector group, and the second vector group, to obtain multiple corresponding subchannel estimated coefficients; and finally, a real channel matrix is determined according to the first vector group, the second vector group, and an estimation matrix consisting of the multiple subchannel estimated coefficients.

A computer-implemented method for determining a transmit precoding operation to apply to a signal to be transmitted through a wireless channel via beamforming wherein the signal u is represented by a vector, u, is described. The method comprises obtaining an inverse channel matrix, G wherein the inverse channel matrix, G, is an inverse of a channel matrix, H, wherein the channel matrix, H, is a matrix representation of the wireless channel. The method further comprises determining a vector, b, that approximately minimizes a square of a norm of a result of applying the inverse channel matrix G to the sum of the vector representing the signal, u, and the vector, b, wherein the entries of the vector, b, are integers and determining the vector b.