A target constellation diagram determining method, a data sending method, and an apparatus are provided in accordance with the disclosure. The target constellation diagram determining method in accordance with the disclosure may include receiving, by a receiving device, training data that is generated and sent by a sending device based on each constellation point in an alternative constellation diagram. A detection region of each constellation point can then be determined based on a position of the training data in the alternative constellation diagram. A cumulative distance corresponding to the alternative constellation diagram can be obtained based on a distance between the detection regions of the constellation points. The method may include determining, based on cumulative distances corresponding to a plurality of alternative constellation diagrams, that an alternative constellation diagram with a largest cumulative distance is a target constellation diagram, and notifying the sending device of the target constellation diagram, so that the sending device modulates to-be-sent data based on the target constellation diagram.

A receiver applies a calibration method to compensate for skew between input channels. The receiver skew is estimated by observing the coefficients of an adaptive equalizer which adjusts the coefficients based on time-varying properties of the multi-channel input signal. The receiver skew is compensated by programming the phase of the sampling clocks for the different channels. Furthermore, during real-time operation of the receiver, channel diagnostics is performed to automatically estimate differential group delay and/or other channel characteristics based on the equalizer coefficients using a frequency averaging or polarization averaging approach. Framer information can furthermore be utilized to estimate differential group delay that is an integer multiple of the symbol rate. Additionally, a DSP reset may be performed when substantial signal degradation is detected based on the channel diagnostics information.

An improved receiver design implements a practical method for modeling users in SIC turbo loop multiuser detection architectures, wherein in each loop unsubtracted estimation errors from previous loops are used to appropriately scale the error covariance matrix for each user, thereby accurately representing the remaining residual interference in the data stream for each desired user. The effect of estimation errors in previous interference cancellation operations is thereby minimized, and symbol estimations in successive turbo loops are improved, for example during multiuser MMSE, multiuser MMSE with interference rejection combining (MMSE-IRC), sample matrix inversion (SMI), or any of their adaptive variants (least mean-square, recursive least square, Kalman filter etc.). The estimated residual symbol energy can be computed per symbol, and then applied to entire data streams, to groups of symbols, or to each symbol separately.

An exemplary decoder is provided for decoding a signal received through a transmission channel in a communication system. The exemplary decoder comprises a transformation unit configured to determine a set of auxiliary channel matrices, each auxiliary channel matrix being determined by performing a linear combination of at least one of the column vectors of the channel matrix; a decomposition unit configured to determine a decomposition of each auxiliary channel matrix into an upper triangular matrix and an orthogonal matrix; a matrix selection unit configured to select at least one auxiliary channel matrix among the set of auxiliary channel matrices depending on a selection criterion related to the components of the upper triangular matrices. The decoder determines at least one estimate of vector of information symbols from an auxiliary signal and from the upper triangular matrix corresponding to a selected auxiliary channel matrix by applying a decoding algorithm.

Embodiments described herein include methods and systems for measuring channel impulse responses in a digital communication system. Specifically, statistical properties of the received signals at the receiver of the digital communication system are analyzed to compute, in real time, channel coefficients indicative of the channel state information, which may be time-dependent, without the use of a training signal.

Disclosed is an electronic device, including a housing, a first communication circuit disposed in the housing and configured to support omnidirectional wireless communication, a second communication circuit disposed in the housing and configured to support directional wireless communication using beamforming, a processor disposed in the housing and operatively coupled to the first communication circuit and the second communication circuit, and a memory disposed in the housing and operatively coupled to the processor. The processor may be configured to receive at least one first radio signal through a communication channel from an external device capable of supporting the omnidirectional wireless communication and the directional wireless communication using the first communication circuit, determine a state of the communication channel based on at least part of the at least one first radio signal, and activate the second communication circuit based on at least part of the determined state of the communication channel wherein the second communication circuit is configured to receive a second radio signal from the external device.

An improved receiver design implements a practical method for modeling users in SIC turbo loop multiuser detection architectures, wherein in each loop unsubtracted estimation errors from previous loops are used to appropriately scale the error covariance matrix for each user, thereby accurately representing the remaining residual interference in the data stream for each desired user. The effect of estimation errors in previous interference cancellation operations is thereby minimized, and symbol estimations in successive turbo loops are improved, for example during multiuser MMSE, multiuser MMSE with interference rejection combining (MMSE-IRC), sample matrix inversion (SMI), or any of their adaptive variants (least mean-square, recursive least square, Kalman filter etc.). The estimated residual symbol energy can be computed per symbol, and then applied to entire data streams, to groups of symbols, or to each symbol separately.

In a mobile communication system, a mobile communication apparatus in a vehicle includes a selected resource antenna permitting communication using a selected resource, establishing wireless communication with a target communication apparatus. The mobile communication system includes a propagation path characteristic acquirer section and a resource selector section. The propagation path characteristics acquirer section acquires propagation path characteristics information in association with a future communication position, the propagation path characteristics information being about propagation path characteristics between (i) the target communication apparatus and (ii) a reference antenna equal to the selected resource antenna in antenna characteristics including an antenna format. The resource selector section, based on the propagation path characteristics information, selects a resource to be used in communication at the future communication position before the selected resource antenna of the mobile communication apparatus comes to be placed at the future communication position.

The present invention relates to a method and apparatus for channel estimation between a transmitter and a receiver in a wireless communications system. In one arrangement, the method comprises: receiving at the receiver a first sequence of bits representing a first sequence of coded symbols transmitted over the communications channel; decoding the first sequence of coded symbols using maximum-likelihood based decoding including: generating traceback outcomes by tracing backwards the first sequence of bits through a maximum-likelihood based traceback path, the traceback outcomes including a first portion associated with a first traceback depth and a second portion associated with a second traceback depth that is deeper than the first traceback depth; generating a channel estimate of the communications channel based on the first portion of the traceback outcomes; and generating an estimate of at least some information bits coded in the first sequence of coded symbols based on the second portion of the traceback outcomes.

An inter-carrier interference (ICI) mitigation circuit associated with an orthogonal frequency division multiplexing (OFDM) receiver is disclosed. The ICI mitigation circuit comprises an ICI cancellation circuit configured to receive an OFDM symbol associated with an OFDM signal and determine an ICI associated with one or more OFDM subcarriers within the OFDM symbol. The ICI cancellation circuit is further configured to cancel the ICI from the one or more OFDM subcarriers associated with the OFDM symbol, in order to generate a desired OFDM symbol. In some embodiments, the ICI is determined and cancelled at the ICI cancellation circuit, in accordance with a predetermined ICI mitigation algorithm.