Mitsubishi Electric Research Laboratories, Inc.

Altiostar Networks, Inc.

Ramesh Annavajjala

Philip Orlik

Jinyun Zhang

Ron Porat

Toshiaki Koike-Akino

Chunjie Duan

Hobin Kim

Raymond Yim

Yige Wang

Man-On Pun

Wei Liu

Liangbin Li

Data can be received characterizing a first signal transmitted in an orthogonal frequency-division multiplexing (OFDM) system by a transmitter with one or more transmit antennas through a wireless channel and received by a receiver with a plurality of receive antennas, the first signal including a plurality of pilot pulses. A final estimated channel impulse response of the wireless channel can be determined for each pair of transmitter and receiver antennas by iteratively finding one or more significant delay taps of an intermediate channel impulse response estimate and adding the one or more significant delay taps to an error of the intermediate channel impulse response estimate. Data characterizing the final estimated channel impulse response can be provided. Related apparatus, systems, techniques, and articles are also described.

Sparse ordered iterative group multi-antenna channel estimation

Data characterizing a first signal transmitted in an orthogonal frequency-division multiplexing (OFDM) system by a transmitter with one or more transmit antennas through an in-band channel and received by a receiver with a plurality of receive antennas can be received. The first signal can include one or more in-band pilot pulses. A channel quality for an out-of-band channel can be predicted based on the received data and a cross-correlation between an in-band channel and one or more out-of-band channels. Data characterizing the predicted channel quality for the out-of-band channel can be provided. Related apparatus, systems, techniques, and articles are also described.

Autonomous channel quality information prediction

Data can be received characterizing a first signal received on a plurality of antennas and comprising multiple transmission signals transmitted simultaneously on at least a same resource element in an orthogonal frequency-division multiple access (OFDM) communications system. A final estimate of the multiple transmission signals can be determined from at least the received data by iteratively estimating multiple transmission signals from the first signal and feeding back selected estimated multiple transmission signals, which satisfy a criterion, to cancel components of the first signal. Data characterizing the estimated multiple transmission signals can be provided. Related apparatus, systems, techniques, and articles are also described.

Sparse ordered iterative group decision feedback interference cancellation

Interference in a received orthogonal frequency division multiplexing (OFDM) symbol, modulated according to selected constellation points s, is reduced. The symbol includes a set of pilot signals and a set of data signals y, where k is a number of consecutive subcarriers used for the pilot and the data signals. The pilot signals are thresholded to detect interfering pilot signals, which are then erased. Channels &#x124;are estimated using remaining pilot signals. The set of data signals are decoded based on the estimated channels &#x124;, and, for each bit bin the set of data signals, a logarithmic likely ratio (LLR) is determined. The LLR is an indicator of the likely interference.

Method for reducing interference in OFDM wireless networks

Time-varying and frequency-selective channels in an orthogonal frequency division multiplexing (OFDM) network are estimated by first storing, in a buffer at a receiver, a received signal corresponding to a set of pilot tones of a set of OFDM symbols. The pilot tones are predetermined and inserted in frequency subcarriers and time slots of the OFDM symbol. A covariance matrix of the received signal is estimated. A diagonal matrix is estimated based on the covariance matrix and a variance of noise in the received signal. The diagonal matrix indicates delays of non-zero paths in a time domain. A channel impulse response (CIR) for each OFDM symbol is estimated using the diagonal matrix, and the received signal. Then, the CIR is transformed to the frequency domain to obtain the channel frequency response (CFR).

Method for estimating time-varying and frequency-selective channels

The first and second nodes in a wireless network estimate first and second channel response. The first node quantizes the first channel response to produce a first bit sequence, and a feed-forward message, which is transmit as a feed-forward message to the second node. The second node quantizes the second channel response using the feed-forward message to produce and an estimate of the first bit sequence, a second bit sequence and a feed-back message, which is transmitted to the first node. Then, the first and second nodes delete bits in the respective bit sequences using the feed-back and feed-forward message to generate first and second private keys with low bit mismatch rate.

Method for generating private keys in wireless networks

Symbols are encoded in a transmitter of a wireless network that uses multiple-input and multiple-output (MIMO) orthogonal frequency division multiplexing (MIMO-OFDM) by partitioning the sub-carriers to be used for transmitting the symbol into a set of K groups of contiguous sub-carriers. For each group k of N&#x2212;1 modulation symbols D(1), D(2), . . . , D(N&#x2212;1), the modulation symbol D(n), for group k, is mapped to a corresponding mapped modulation symbols X(n) according to X(n)=&#x3b1;(k)(D(n)&#x2212;m(k))+&#x3b2;(k) n=1, . . . , N&#x2212;1, X(N)=&#x3b1;(k)m(k), where m(k) is a sample-mean of the set of modulation symbols corresponding to the kgroup, &#x3b1;(k), &#x3b1;(k) and &#x3b2;(k), for k=1, . . . , K, are constants, wherein the constants are predetermined and positive.

Implicit channel sounding for closed-loop transmission in MIMO-OFDM wireless networks

In an orthogonal frequency division multiplexing (OFDM) network, a set of pseudo random sequences (PRS) are stored at a transmitter and a receiver. Each OFDM symbol is mapped to subcarriers for a set of transmit antennas to produce a mapped symbol. The mapped symbol is encoded using a pseudo-random phase precoder (PRPP) and the PRS to produce a precoded symbol. An inverse fast Fourier transform (IFFT) is applied to the precoded symbol, and the encoded symbol is transmitted to the receiver using the set of transmit antennas.

OFDM networks with pseudo-random phase precoding

A set of data symbols is selected from a set of modulation constellation, and a sample-mean of the set of data symbols is determined. Each data symbol is first shifted by the sample-mean to obtain a shifted data symbol, and then the shifted symbol is multiplied by a first constant to obtain a scaled data symbol. A second constant is added to the scaled data symbol to obtain a mapped data symbol. The sample-mean is multiplied by a third constant to obtain a sample-mean mapped symbol. The set of mapped data symbols and the sample-mean mapped symbol are then transmitted as a resource block.

Method for encoding data symbols with implicitly embedded pilot symbols in resource blocks for wireless networks

Channel state information in a closed-loop, multiple-input, multiple-output wireless networks is fed back from each mobile station to a base station by first determining a transmit covariance matrix R, and applying a singular value decomposition (SVD) R=U&#x3a3;V, where U, V are left and right singular vector matrices, &#x3a3; is a diagonal matrix with singular values. The matrix V includes column vectors V. A beamforming vector v=[1 exp(j&#x3a6;)exp(j2&#x3a6;) . . . exp(j&#x3a6;)]/&#x221a;{square root over (N)}] is approximated by the column vector V having a maximum magnitude, where &#x3a6; is a real number. Then, only the angle &#x3a6; is fed back using a phase modulation mapping of the components exp(j&#x3a6;) onto the associated subcarrier.

Parametric compression of rank-1 analog feedback

Beams are used to communicate in a wireless network including mobile and stationary receivers. The network operates according to the IEEE 802.11p in wireless access to vehicular environments (WAVE). A direction from the mobile transceiver to the stationary receiver is predicted using geographic information available to the mobile transceiver. A set of signals are received in the mobile transceiver from the stationary transceiver, wherein the signals are received by an array of antennas, and wherein the signals are received using a set of beams, and wherein each beam is approximately directed at the stationary receiver. A signal-to-noise ratio (SNR) is measured for each beam, and the beam with an optimal SNR is selected as an optimal beam for communicating data between the mobile transceiver and the stationary transceiver.

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Quincy, MA, United States of America

Ramesh Annavajjala