To reflect advantages of continuous phase modulation (CPM), the invention provides a low complexity transmitter and receiver to transmit and receive CPM signals. CPM is a spectrum-efficient digital modulation scheme, which enables constant or quasi-constant envelope communication, leading to significant battery savings on top of bandwidth and energy savings. Despite the desirable properties of CPM, the complexity of an optimum CPM demodulator can be very high, due to the inherent memory nature of CPM. Specifically, the number of states in an optimum CPM demodulator is exponentially dependent on the length of the frequency pulse, L.

The present invention addresses a significant reduction in the CPM demodulator complexity, and is especially well-suited for large values of L, e.g., L3. The invention utilizes a linear filter front end as an integral part of the CPM demodulation process so as to reduce the ISI inherent in CPM transmit signal, and minimizes the influence of L in the reception process. To that end, the invention renders the complexity of a CPM demodulator non-exponentially dependent on L, and L only has a weak impact on the number of coefficients of the linear front end filters. Moreover, the invention provides a simple way of forming CPM signals for a digital communication transmitter using parallel Time Invariant Phase Encoders, which simplifies the production of CPM waveforms on software or hardware.

A method and apparatus are provided. The method includes receiving, by a user equipment (UE), a phase shift keying (PSK) modulated signal from a transceiver, derotating the PSK modulated signal, and equalizing the PSK modulated signal using a maximum likelihood sequence estimator (MLSE) based on a first main tap gain (MTG) look up table (LUT) and a first inter-symbol interference (ISI) LUT corresponding to even time samples and a second MTG LUT and a second ISI LUT corresponding to odd time samples.

The disclosure relates to bit-interleaved coded modulation with iterative decoding. In some implementations, a receiver comprises: a first memory including multiple first sub-memories; a decoder configured to perform first operations comprising: calculating, first extrinsic information of multiple code bits associated with multiple received symbols; and a demapper configured to perform second operations comprising: calculating soft decision information of the code bits; calculating, based on the soft decision information and the first extrinsic information, second extrinsic information of the code bits; and writing the second extrinsic information of the code bits into the first memory such that, for each received symbol, each sub-memory of the first sub-memories respectively stores the second extrinsic information associated with a respective one of the code bits corresponding to the received symbol.

Disclosed is a reception apparatus that has solved a problem that fluctuations cannot be followed immediately after a commencement of turbo equalization in a high-speed fading environment. A reception apparatus includes a soft interference canceller, an MMSE equalizer, a likelihood calculator, a de-interleaver, an SISO decoder, an information bit hard decision unit, a subtracter, an interleaver, a soft estimation value calculator, a zero storage unit, a known signal memory unit, a transmission path estimator, and a plurality of switches. At the time of equalization, the transmission path estimator uses, as a reference signal, a known signal stored in the known signal memory unit or an output of the MMSE equalizer. Meanwhile, at the time of a first equalization, the soft interference canceller is given a 0 value from the zero storage unit as a reference signal.

A method and apparatus are provided. The method includes receiving, by a user equipment (UE), a phase shift keying (PSK) modulated signal from a transceiver, derotating the PSK modulated signal, and equalizing the PSK modulated signal using a maximum likelihood sequence estimator (MLSE) based on a first main tap gain (MTG) look up table (LUT) and a first inter-symbol interference (ISI) LUT corresponding to even time samples and a second MTG LUT and a second ISI LUT corresponding to odd time samples.

A base station apparatus is provided with at least one remote unit apparatus each including at least one antenna, and a central unit apparatus connected to each remote unit apparatus via a transmission path. The antenna provided in the remote unit apparatus receives a transmission signal wirelessly transmitted from at least one wireless terminal each including at least one antenna. The remote unit apparatus includes a channel estimation unit that estimates channel information between the antenna of the wireless terminal and the antenna of the remote unit apparatus, using a reception signal received by the antenna provided in the remote unit apparatus, a likelihood calculation unit that calculates likelihood of each transmission signal included in the reception signal, for each antenna provided in the remote unit apparatus, using the channel information estimated by the channel estimation unit, and an inter-unit transmission unit that transmits likelihood information calculated by the likelihood calculation unit to the central unit apparatus. The central unit apparatus is provided with an inter-unit receiving unit that receives the likelihood information transmitted from the inter-unit transmission unit, and a signal detection unit that combines the likelihood information received by the inter-unit receiving unit, and outputs a signal corresponding to each transmission signal transmitted from the wireless terminal, using combined likelihood information.

Systems and methods for mitigating the effect of in-band interference. The methods comprise: receiving a signal comprising at least one interfering signal component; generating a soft value for each symbol in at least one interfering signal component; and using the soft values to cancel at least one interfering signal component from the signal to mitigate the effect of interference. The soft value represents a most likely value for the symbol which is obtained by: determining a probability metric between an actual value of the symbol and each of a plurality of possible symbol values using a scaling value representing an estimate of the noise level in the signal received by the device; generating current local probabilities for the plurality of possible symbol values using the probability metric; and using the current local probabilities to determine the soft value.

Systems and methods for detecting data in a received multiple-input-multiple-output signal are provided. N signals are received from N antennas, with M being greater than or equal to three. The N signals form a vector y and are associated with M sets of data values, where the M sets of data values form a vector x. A channel matrix (H) is estimated, and a QR decomposition of the channel matrix is performed, such that H=QR. The vector y is transformed into a vector z according to z=Q.sup.Hy. The R matrix and the rotated signal vector z are transformed such that one or more elements of the R matrix having complex number values are set equal to zero. Distance values are calculated using the transformed vector z and the vector x. Log likelihood ratio (LLR) values are calculated based on the distance values.

Circuits for producing signals representative of mean and variance estimations for quadrature amplitude modulation (QAM) are provided where the circuits comprise: sequentially repeated first circuit modules and sequentially repeated second circuit modules configured for producing updates in the corresponding estimation iterations. In one embodiment, a closest negative integer power of 2 is used as a substitute multiplicand when multiplying together two or more outputs of hyperbolic function generating units where the substituted for output is less than one. Size and complexity of the corresponding multiplier can then be reduced.

In an asymmetric time-reversal wireless system, a base station includes an input circuit configured to, during a hand-shake period, receive a channel response signal derived from a probe signal sent from a first terminal device to the apparatus through multiple wireless propagation paths, and during an uplink transmission period, receive combined signals that include a signal from the first terminal device and a signal from a second terminal device. The base station includes a data processor configured to calculate a signature waveform for the first terminal device based on the channel response, and determine the signal sent from the first terminal device during the uplink transmission period based on the combined signals and the signature waveform for the first terminal device.