The present invention is a computationally-efficient compensator for removing nonlinear distortion. The compensator operates in a digital post-compensation configuration for linearization of devices or systems such as analog-to-digital converters and RF receiver electronics. The compensator also operates in a digital pre-compensation configuration for linearization of devices or systems such as digital-to-analog converters, RF power amplifiers, and RF transmitter electronics. The compensator effectively removes nonlinear distortion in these systems in a computationally efficient hardware or software implementation by using one or more factored multi-rate Volterra filters. Volterra filters are efficiently factored into parallel FIR filters and only the filters with energy above a prescribed threshold are actually implemented, which significantly reduces the complexity while still providing accurate results. For extremely wideband applications, the multi-rate Volterra filters are implemented in a demultiplexed polyphase configuration which performs the filtering in parallel at a significantly reduced data rate. The compensator is calibrated with an algorithm that iteratively subtracts an error signal to converge to an effective compensation signal. The algorithm is repeated for a multiplicity of calibration signals, and the results are used with harmonic probing to accurately estimate the Volterra filter kernels. The compensator improves linearization processing performance while significantly reducing the computational complexity compared to a traditional nonlinear compensator.

Compensator for removing nonlinear distortion

A method of connecting devices to a network is provided. The method includes providing base stations connected to a network, and at each of the base stations, receiving probe signals from terminal devices. For each of the terminal devices, the base station calculates a signature waveform based on a time-reversed waveform of a channel response signal derived from the corresponding probe signal. For each of the terminal devices, the base station determines a downlink transmit signal for the terminal device based on the downlink data and the corresponding signature waveform, and transmits the downlink signals to the terminal devices. Several base stations have overlapping broadcast regions, several terminal devices are located within the overlapped broadcast regions, the base stations transmit the downlink signals using a same frequency band, and some downlink signals transmitted by base stations having overlapping broadcast regions also overlap in time.

Time-reversal wireless paradigm for internet of things

There is provided a communication system including a transmitting section and a receiving section which includes a plurality of receivers. The transmitting section includes a communication unit which receives a plurality of signals respectively from the plurality of receivers, and stores a plurality of time-reversed signals corresponding to the received plurality of signals with respect to the plurality of receivers, and a first conversion unit which converts, by a first factor, a plurality of information sequences to be respectively transmitted to the plurality of receivers and forward the plurality of converted information sequences to the communication unit. The communication unit generates, based on the plurality of converted information sequences, a plurality of output signals to be respectively transmitted to the plurality of receivers, each of the plurality of the output signals including a location-specific signature unique to the corresponding receiver.

Systems and methods for time-reversal division multiple access wireless broadband communications

A multicarrier communication device can vary the number of subcarriers being used to carry on multicarrier communication within a network, based on a predetermined criterion (e.g., traffic load, etc.).

Methods and apparatus to support scalability in a multicarrier network

Orthogonal frequency division multiplexing (OFDM) is a spectrally efficient multicarrier modulation technique for high speed data transmission over multipath fading channels, but has low power efficiency. OFDM signals have large crest factors, or peak-to-average power ratios (PARs) which lead to power inefficiency in the RF portion of the transmitter. Selected mapping can be used to reduce the PAR of an OFDM signal and is distortionless. A technique is disclosed that links the index of a phase rotation sequence used in selected mapping to the location of pilot tones that are used to estimate the channel. Each pilot tone location-phase sequence selection produces a different PAR value for the time-domain OFDM signal, and the signal with the lowest PAR value is transmitted. The technique is “blind” in that the optimum pilot tone location-phase sequence index is not transmitted as side information. A technique to blindly detect the optimum index at the receiver is also disclosed.

Crest factor reduction in OFDM using blind selected pilot tone modulation

A system and method of implementing a Fast Fourier Transform (FFT) function in a high data rate communication network. The communication network, employing technology such as VDSL and DMT or FDM, frequently implements a FFT at a transmitter to transfer frequency domain modulated signals into time domain signals. An IFFT is implemented at the receiver to obtain the original signal. The present system divides the channel bandwidth into sub-bands and performs the FFT function with multiple FFTs in order to reduce chip size and computation time.

Efficient implementation of large size FFT

A system and method of implementing a Fast Fourier Transform (FFT) function in a high data rate communication network. The communication network, employing technology such as VDSL and DMT or FDM, frequently implements a FFT at a transmitter to transfer frequency domain modulated signals into time domain signals. An IFFT is implemented at the receiver to obtain the original signal. The present system divides the channel bandwidth into sub-bands (band I...band k) and performs the FFT function with multiple FFT's in order to reduce chip size and computation time.

Dividing bandwidth into sub-bands prior to implementing an FFT in a high data rate communications network

L'invention concerne un systeme et un procede permettant de mettre en oeuvre une transformation de Fourier rapide dans un reseau de telecommunications a debit de donnees eleve Le reseau de telecommunications, qui emploie des techniques telles que celles de la ligne d'abonne a tres haut debit de donnees et celles de la multitonalite discrete ou du multiplexage frequentiel, met en oeuvre une transformation de Fourier rapide dans un emetteur afin de transformer des signaux modules dans le domaine des frequences en des signaux du domaine temporel Les donnees sont soumises a l'action d'un modulateur (QAM), d'un moyen de transformation de Fourier rapide (IFFT), d'un moyen d'echantillonnage ascendant ( M), et d'un filtre (1 a K) Une transformation de Fourier rapide inverse de la premiere est mise en oeuvre dans le recepteur Le systeme de l'invention divise la largeur de bande en sous-bandes et realise la fonction de transformation de Fourier rapide au moyen de plusieurs transformations de Fourier rapide de maniere a reduire la taille de la puce et le temps de calcul

Systeme et procede de mise en oeuvre d'une transformation de fourier rapide, utilisee, notamment dans un reseau de telecommunications a debit de donnnees elevees

Qu Jin Gary

Papers

Efficient implementation of large size FFT

Dividing bandwidth into sub-bands prior to implementing an FFT in a high data rate communications network

Systeme et procede de mise en oeuvre d'une transformation de fourier rapide, utilisee, notamment dans un reseau de telecommunications a debit de donnnees elevees