Nitero Pty Limited

Yunxin Li

This invention concerns the estimation of signal to noise ratio (SNR) at a communications receiver; it may be applicable to a wide range of receivers but is particularly suited for Orthogonal Frequency Division Multiplexing (OFDM) receivers. In particular the invention is a method, a receiver and software for performing the method. The signal to noise ratio (SNR) in the received signals is estimated by directly estimating the power ratio, in the received signal, between the part of the frequency spectrum of the received signal that contains only noise, and the part of the spectrum that contains both signal and noise; and averaging this value over a time interval.

Estimation of signal to noise ratio in receivers

This invention concerns soft-decision demapping of Quadrature Amplitude Modulation (QAM) signals to enable soft-decision channel decoding in a communications system. In a first aspect the invention is a method for performing the soft-decision demapping of Quadrature Amplitude Modulation (QAM) signals to enable soft-decision channel decoding in a communications system. The method comprises the steps of Extracting baseband signals from both I-and-Q channels. Sampling the baseband signals to extract a stream of complex numbers. Converting the stream of complex numbers to frequency domain vectors with components for each subcarrier frequency. Approximating bit log-likelihood ratios for each symbol directly from the real and imaginary parts of the corresponding frequency vector, without equalization by the estimated channel. And, soft-decoding of the channel codes using the approximated log-likelihood ratios. In other aspects the invention concerns a device for performing the method and software for performing the method.

Soft-demapping of QAM signals

In one aspect, the method of synchronizing a communications device in a wireless communications network comprises receiving a beacon signal at a first frequency; and receiving a data signal at a second frequency, the beacon signal being used to synchronize reception of the data signal. In another aspect, the method comprises transmitting a beacon signal at a first frequency; and transmitting a data signal at a second frequency, the beacon signal being useable to synchronize reception of the data signal. The first frequency is substantially less than the second frequency such that the beacon signal experiences substantially different frequency-dependent propagation effects to the data signal.

Synchronising a communications device

A Symbol vector for RF transmission after multiplexing onto a subset of a set of subcarriers using OFDM is transformed to the time domain. A first time domain cancellation vector is generated from a basis vector that has the same dimensionality as the symbol vector. In the frequency domain the basis vector has a substantially zero value in each of a first subset of sub-carriers of the symbol vector and in the time domain the difference between a first element of the basis vector having the highest value and a second element of the basis vector having the next highest value is maximized. The first cancellation vector is subtracted from the symbol vector to produce modified symbol vector having reduced Peak-to-Average Power Ratio (PAPR). A second cancellation vector is generated using the modified symbol vector and is used to produce a second modified symbol vector having reduced PAPR.

Growing community of inventors

Vaucluse, Australia

Yunxin Li