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 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.

The invention described herein presents a system and method to overcome the distortions and affectations introduced by the highly variant channels of one or several antennas both in the transmitter and in the receiver.

Unlike any existing invention that operates under the same conditions, this device uses a completely new reception technique based on the concept of virtual trajectories in which iterative calculations or solution of linear systems in operating time are not required, thus saving a considerable amount of operations.

The receiver of this device manages to convert the fast variations of the channel into virtual antennas, thus achieving a considerable increase in the signal to noise-interference ratio. The resulting performance in terms of noise immunity is much better than any technique found so far and also requires a much smaller amount of calculations in the receiver.

This application provides an uplink multi-station channel estimation method, a station (STA), and an access point (AP), which can be applied to an uplink multi-user multiple-input multiple-output scenario. The uplink multi-station channel estimation method includes: a STA generating a frame including a first group of training sequences and a second group of training sequences, and sending the frame to the AP. The AP calculates a frequency offset value between the STA and the AP based on the received first group of training sequences and the received second group of training sequences. The AP performs channel estimation based on the calculated frequency offset value. According to the technical solutions provided in this application, the AP can more accurately learn of frequency offset values between a plurality of STAs and the AP. This improves channel estimation precision.

A multi-antenna network system has a reduced operational complexity for matrix inversion by referring to the variations of the status of a plurality of communication channels at a first time duration and a second time duration. Therefore, the speed for calculating matrix inversion is improved. Accordingly, the amount of servo antennas and/or user antennas operating in the same multi-antenna network system can be increased.

A plurality of circuit units of a matrix processor of a communication device are used to decompose a plurality of channel matrices, corresponding to a plurality of orthogonal frequency division multiplexing (OFDM) tones, over a plurality of cycles to determine matrix equalizer coefficients. Decomposing the plurality of channel matrices includes determining respective modes of operation for respective ones of the circuit units for respective ones of the cycles. The respective modes of operation are selected from a set of modes that includes at least one of a bypass mode for propagating input signals to output signals without altering the input signals and an idle mode for saving power when a particular circuit unit is not needed during a particular cycle. The respective circuit units are individually controlled to operate in the determined respective modes during the corresponding cycles. The determined matrix coefficients are then applied to received data signals.

A channel matrix representing characteristics of a multi-path channel between a transmitter device (210) equipped with multiple transmitter antennas (211, 212, 213, 214, 215) and at least one receiver device (220, 230, 240) equipped with one or more receiver antennas (221, 222, 231, 232, 241, 242). The channel matrix is organized in one or more channel vectors each associated with a corresponding one of the one or more receiver antennas (221, 222, 231, 232, 241, 242). An iterative optimization algorithm is applied to determine a precoding matrix from the channel matrix. At least one step size of the iterative optimization algorithm is set depending on a vector norm of at least one of the channel vectors. Multi-antenna transmission by the transmitter device (210) is then controlled based on the determined precoding matrix.

Techniques and architectures for multi-stage cancellation of self-interference (SI) and joint cancellation of mutual-interference (MI) and residual SI in signals received by devices of a full-duplex multi-cell network are disclosed. In various examples, channel estimations and interference cancellation operations are performed utilizing multiple orthogonal training signals transmitted by network devices during a common over-the-air training period. Training signals derived from the orthogonal training signals during transmission are utilized to generate SI estimation information and perform at least a first SI cancellation operation on a received signal that includes at least first and second orthogonal training signals. The received signal and orthogonal training signals are then used to estimate a MI channel impulse response and a (residual) SI channel impulse response for use in joint MI/SI cancellation operations on further received signals. Details regarding the design of the orthogonal training signals and a unique system-level delay calibration procedure are also provided.

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.

A technique for determining channel coefficients for a first array of antennas coupled through respective first phase shifters to a first radio chain and a second array of antennas coupled through respective second phase shifters to a second radio chain is described. As to a method aspect of the technique, pairs of first and second phase vectors are applied to the first and second phase shifters, respectively. Each of the pairs defines complementary directional gains at the first and second arrays for receiving reference signals. A channel estimation is performed in each of the first and second radio chains for each of the pairs based on the received reference signals. Based on the channel estimations for each of the pairs, at least one channel coefficient for the antennas in each of the first and second arrays is determined.