7561results about "Multiple carrier systems" patented technology

Transmitter and receiver units for use in a communications system and configurable to provide antenna, frequency, or temporal diversity, or a combination thereof, for transmitted signals. The transmitter unit includes a system data processor, one or more modulators, and one or more antennas. The system data processor receives and partitions an input data stream into a number of channel data streams and further processes the channel data streams to generate one or more modulation symbol vector streams. Each modulation symbol vector stream includes a sequence of modulation symbol vectors representative of data in one or more channel data streams. Each modulator receives and modulates a respective modulation symbol vector stream to provide an RF modulated signal, and each antenna receives and transmits a respective RF modulated signal. Each modulator may include an inverse (fast) Fourier transform (IFFT) and a cyclic prefix generator. The IFFT generates time-domain representations of the modulation symbol vectors, and the cyclic prefix generator repeats a portion of the time-domain representation of each modulation symbol vector. The channel data streams are modulated using multi-carrier modulation, e.g., OFDM modulation. Time division multiplexing (TDM) may also be used to increase flexibility.

A novel apparatus and method for a hybrid Cartesian / polar digital QAM modulator. The hybrid technique of the present invention utilizes a combination of an all digital phase locked loop (ADPLL) that features a wideband frequency modulation capability and a digitally controlled power amplifier (DPA) that features interpolation between 90 degree spaced quadrature phases. This structure is capable of performing either a polar operation or a Cartesian operation and can dynamically switch between them depending on the instantaneous value of a metric measured by a thresholder / router. In this manner, the disadvantages of each modulation technique are avoided while the benefits of each are exploited.

The present invention provides an FM Orthogonal Frequency Division Multiplexing (OFDM) modulation process that enable high-speed data communications over any transmission media and networks. The process is implemented with a modem device modulator and demodulator that provides communication with several other modem devices along any communication media that uses an FM OFDM modulation technique, a physical transmission medium such as power lines, or wireless (air), or cable, or twisted pairs communication media.

A system, method and power / data transmission device comprising a coil having a high Q, a low-voltage driver and a high-voltage driver switchably coupled to the coil. The low-voltage driver and the high-voltage driver are controlled by a microcontroller and switch at about the same time thereby providing a modulated data signal for transmission. Furthermore, the system includes at least one implantable microstimulator coupled to the transmission device.

A data-modulated ultra wideband transmitter that modulates the phase, frequency, bandwidth, amplitude and / or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and / or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and / or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and / or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.

An amplitude error compensating device comprises an amplitude correcting section for performing amplitude correction with respect to an in-phase component and a quadrature component of a complex signal obtained by quadrature demodulation, based on amplitude error information, and outputting a resultant amplitude-corrected complex signal, and an amplitude error detecting section for obtaining the amplitude error information, depending on amplitudes of an in-phase component and a quadrature component of the amplitude-corrected complex signal. The amplitude error detecting section comprises a power difference calculating section for obtaining as a power error a difference in power between the in-phase component and the quadrature component of the amplitude-corrected complex signal, a rotation detecting section for detecting a rotation of a signal point of the amplitude-corrected complex signal, an error information control section for outputting the power error when a rotation of the signal point has been detected, and 0 when a rotation of the signal point has not been detected, and a smoothing section for smoothing an output of the error information control section, and outputting the result as the amplitude error information.

An approach is provided for a method of encoding structure Low Density Parity Check (LDPC) codes. Memory storing information representing a structured parity check matrix of Low Density Parity Check (LDPC) codes is accessed during the encoding process. The information is organized in tabular form, wherein each row represents occurrences of one values within a first column of a group of columns of the parity check matrix. The rows correspond to groups of columns of the parity check matrix, wherein subsequent columns within each of the groups are derived according to a predetermined operation. An LDPC coded signal is output based on the stored information representing the parity check matrix.

A novel apparatus and method for a fully digital quadrature architecture for a complex modulator. The complex modulator can substitute for existing prior art analog quadrature modulator structures and those based on a digital polar architecture (r, θ). The modulator effectively operates as a complex digital-to-analog converter where the digital inputs are given in Cartesian form, namely I and Q representing the complex number I+jQ, while the output is a modulated RF signal having a corresponding amplitude and phase shift. The phase shift being with respect to a reference phase dictated by the local oscillator, which is also input to the converter / modulator. Several embodiments are provided including modulators incorporating dual I and Q transistor arrays, a single shared I / Q transistor array, modulators with single ended and differential outputs and modulators with single and dual polarity clock and I / Q data signals.

A data processing apparatus communicates data bits on a predetermined number of sub-carrier signals of an Orthogonal Frequency Division Multiplexed (OFDM) symbol. The data processing apparatus comprises a parity interleaver operable to perform parity interleaving on Low Density Parity Check (LDPC) encoded data bits obtained by performing LDPC encoding according to a parity check matrix of an LDPC code including a parity matrix corresponding to parity bits of the LDPC code, the parity matrix having a stepwise structure, so that a parity bit of the LDPC encoded data bits is interleaved to a different parity bit position. A mapping unit maps the parity interleaved bits onto data symbols corresponding to modulation symbols of a modulation scheme of the OFDM sub-carrier signals. A symbol interleaver is arranged in operation to read-into a symbol interleaver memory the predetermined number of data symbols for mapping onto the OFDM sub-carrier signals, and to read-out of the interleaver memory the data symbols for the OFDM sub-carriers to effect the mapping, the read-out being in a different order than the read-in, the order being determined from a set of addresses, with the effect that the data symbols are interleaved on the sub-carrier signals. The set of addresses are generated by an address generator which has been optimised to interleave the data symbols on to the sub-carrier signals of the OFDM carrier signals for a given operating mode of the OFDM system, such as a 32K operating mode for DVB-T2 or DVB-C2.

Provided is a transmission circuit which allows smooth switching of the operation mode when switching the operation mode of the transmission circuit. A power amplifier 14 includes: a first input terminal to which a direct-current voltage or a voltage in accordance with an amplitude signal M is supplied; a second input terminal to which an output signal from a first variable gain amplifier 171 or an output signal from a second variable gain amplifier 172 is inputted; and a third input terminal to which an output signal from a first bias circuit 15 or an output signal from a second bias circuit 16 is inputted. A control section 11 switches the operation mode of the transmission circuit so that at least one of the first input terminal, the second input terminal, and the third input terminal of the power amplifier is prevented from being in a no input state.

When supplying a power from a base station to a terminal station on radio and a distance from a base station to a terminal station is long, it becomes impossible for the terminal station to rectify the power. The feature of the present invention is found in a wireless communication system in which the peak value and duty ratio of a transmission power are controlled simultaneously, keeping the transmission power of a base station below a fixed value, thereby allowing a voltage to be applied to a diode, which is a component of a rectifier circuit possessed by a terminal station, always in excess of a threshold voltage of the diode, and energy is exchanged between the base station and the terminal station below a limit power.

A cellular radio communication system is provided for transmitting data over a plurality of transmission links. The system includes means for generating a modulated signal by applying a constant amplitude envelope modulation scheme to data to be transmitted across poor quality transmission links and amplifier means for non-linearly amplifying the modulated signal. The system can additionally include means for generating a second modulated signal by applying an amplitude dependent modulation scheme to data to be transmitted across higher quality transmission links and amplifier means for linearly amplifying the second modulated signal. Using a constant amplitude envelope modulation scheme, such as GMSK or MLCAM for poorer quality links means that for these links signals can be amplifier non-linearly at higher gains.

A method and system (102) provide adaptive modulation / coding with distribution of excess resources based on one or more system criteria. The system (102) may be any system with more than one modulation rate or more than one coding rate and may be a wireless communication system using CDMA, TDMA, OFDM or any other signal formats. Generally, the method determines excess resources of the system based on desired characteristics of links supported by the system. The excess resources may be any number of system resources, such as transmit power. These excess resources are then distributed to the links based on various system criteria, such as to increase system coverage, to increase system capacity, to modify a data rate profile of the system or to reduce interference in the system. Methods for providing such distribution of the excess resources are also provided for equal data rate systems.

A method for a combined adaptive digital pre-distorter and pre-equalizer apparatus in single- and / or multiple-link hopping radio systems including hopping among a plurality of radio links to transmit variable-length bursts of radio signals on the plurality of radio links. Further, pre-distorting amplitude and phase of transmitted signal constellations based on the inverse AM-to-AM and AM-to-PM characteristics and the operating conditions of the high-power amplifier, respectively. Further, pre-equalizing amplitude and group-delay variations of the transmit RF radio using the pre-stored estimated complex tap coefficient of the pre-equalizer under different frequency bands.

A reduction in a peak-to-mean envelope power ratio of a multicarrier signal, represented as a time domain signal, is achieved by applying (76) an offset, indicative of a difference (74) between a mean signal level and a midpoint level of the time domain signal, to the time domain signal. Alternatively, constellation values of positive and negative frequency components are modified by differing functions to produce a modified data set. Preferably, the negative frequency components are set to a predetermined value (namely zero (124)) to provide an alternate coding scheme Once the multicarrier signal has been converted into a time domain representation, real and imaginary parts (126-128) of the modified data set that consequently only contain positive frequency components and zeros are compared with one another to identify (130) which of the real and imaginary parts has a lower peak-to-average signal ratio (134) for the time domain representation. Then, based upon which of the peak-to-average signal ratios is lowest (136), either the real and imaginary part of the time domain signal is selected for subsequent transmission (138).

An interleaving method performed by a transmitter for a communication system with quasi-cyclic low-density parity-check codes, spatial multiplexing, and T transmit antennas is used for applying permutation to N cyclic blocks of a codeword in order to map bits of the permutated cyclic blocks onto T constellation words constituting multiple spatial-multiplexing blocks from the codeword. Each cyclic block consists of Q bits.

Fiber, cable, and wireless data channels are typically impaired by reflectors and other imperfections, producing a channel state with echoes and frequency shifts in data waveforms. Here, methods of using OTFS pilot symbol waveform bursts to automatically produce a detailed 2D model of the channel state are presented. This 2D channel state can then be used to optimize data transmission. For wireless data channels, an even more detailed 2D model of channel state can be produced by using polarization and multiple antennas in the process. Once 2D channel states are known, the system turns imperfect data channels from a liability to an advantage by using channel imperfections to boost data transmission rates. The methods can be used to improve legacy data transmission modes in multiple types of media, and are particularly useful for producing new types of robust and high capacity wireless communications using non-legacy OTFS data transmission methods.

The invention relates to a method and system for wideband digital pre-distortion linearization, which is used to overcome the influence of memory effect in radio frequency power amplifier, to expand digital pre-distortion linearization bandwidth, and to improve digital pre-distortion linearization performance. The method and system can get an in-band pre-distortion signal and an out-of-band pre-distortion signal according to the characteristic parameter of the amplifier; the in-band pre-distortion signal is up-converted and the up-converted signal is added to the out-of-band pre-distortion signal, which is not up-converted, then the combined signal is inputted to the power amplifier as an input signal; a part of the output signal from the power amplifier, serving as a feedback signal, can be compared with the original input signal, and the characteristic parameter of the amplifier for generating the in-band pre-distortion signal and the out-of-band pre-distortion signal is adaptively regulated according to the comparison result, so that the waveform of time domain or the frequency domain of the feedback signal can be close to that of the original input signal as much as possible.

A transmitter apparatus and a receiver apparatus are provided. The transmitter apparatus includes: an encoder configured to generate a low density parity check (LDPC) by performing LDPC encoding; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol. The modulator maps a bit included in a predetermined group from among a plurality of groups constituting the LDPC codeword onto a predetermined bit in the modulation symbol.

A data field of transmitted digital television signals includes a first set of A / 53-compliant data segments that convey payload information and further includes a second set of A / 53-compliant data segments that contain parity bytes for transverse Reed-Solomon forward-error-correction coding of the data contained within the first set of A / 53-compliant data segments. A digital television receiver uses the parity bytes in the second set of A / 53-compliant data segments to implement transverse Reed-Solomon forward-error-correction decoding that corrects byte errors in the data contained in the first set of A / 53-compliant data segments.

An apparatus for transmitting data in a communication system using a Low Density Parity Check (LDPC) matrix is provided. The apparatus includes an interleaver for interleaving a descending bit-ordered codeword having a predetermined size and in accordance with a predetermined modulation scheme; and a bit mapper for mapping codeword bits constituting the interleaved codeword in accordance with a predetermined mapping scheme that takes into account degrees of the codeword bits and reliability characteristics of modulation symbol-constituting bits based on the predetermined modulation scheme.

A cellular wireless packet data communication system containing transmit-only endpoint devices which transmit to receive-only base stations. The system is configured to allow for large area coverage (e.g., a metropolitan area) with far fewer number base stations than are required with conventional two-way cellular systems. The base station coverage areas are configured to overlap, allowing for reception of packets at multiple base stations. A data concentrator resolves redundantly received messages. The network is configurable as a WAN, a LAN, or a combination of the two. Novel modulation techniques (e.g., a 16QAM submodulation together with a 7FSK modulation) are used such that low cost components can be used in the transmitters and receivers while achieving outstanding probability of success performance. The endpoint devices are battery operated and accordingly, are designed for low power consumption and multi-year battery life. The system is used in a variety of applications including remote monitoring and mobile communications.

This invention is generally concerned with methods, apparatus and processor control code for decoding signals, in particular by means of sphere decoding. A sphere decoder configured to search for one or more strings of symbols less than a search bound from an input signal by establishing a value for each symbol in turn of a candidate said string by postulating values for each said symbol in turn of said candidate string and determining whether a said postulated symbol value results in a distance metric dependent upon said search bound being satisfied, each said symbol of a said candidate string for which values are postulated defining a level of said search. The sphere decoder includes a data structure configured to define, for each level of said search, a set of symbol values from which said postulated values are selected, said sets of symbol values being different at different levels of said search.

The present invention is related to methods and apparatus that compensate for quadrature impairments of an analog quadrature modulator and / or demodulator over a relatively wide signal bandwidth. One embodiment pre-distorts baseband signals in a quadrature modulator compensation signal processor (QMCSP) to negate the quadrature impairment of an analog quadrature modulator and corrects a received baseband signal in a quadrature demodulator compensation signal processor (QDCSP) to cancel the quadrature impairment of an analog quadrature demodulator. The QMCSP and the QDCSP contain adaptive digital filter correction structures that pre-compensate and post-compensate, respectively, for the quadrature impairments introduced by the analog quadrature modulator and the analog quadrature demodulator over a relatively wide bandwidth. A phase shifter advantageously shifts the phase of a local oscillator signal to the analog quadrature demodulator to distinguish quadrature impairments introduced by the modulation path from quadrature impairments introduced by the demodulation path.

The present invention provides a digital (computational) branch calibrator which uses a feedback signal sensed from an RF transmit signal path following the combining stage of LINC circuitry of a transmitter to compensate for gain and phase imbalances occurring between branch fragment signals leading to the combiner. The calibrator feeds a quiet (zero) base band signal through the transmit path during the calibration sequence (i.e. a period when data is not transmitted) and adjusts the phase and gain of the phasor fragment signals input thereto by driving the sensed output power to zero. The calibration is performed by alternating phase and gain adjustments with predetermined (programmable) and multiple update parameters stages (speeds). A baseband modulation is preferably used to distinguish false leakage (e.g. due to local oscillator, LO, feed through and DC offset in the base band Tx) from imbalance leakage.

A receiver system that receives signals and has a demapper device that is responsive to an equalizer output and generates a demapper output including one or more bit metrics. The receiver system also generates equalizer output, and the demapper uses distance measure to calculate bit metrics. The receiver system uses demapper output to generate a processed output. The receiver system further includes a convolutional decoder which is responsive to the processed output, and subsequently generates a decoded bit sequence, as well as uses the processed output to generate one or more path metrics. The convolutional decoder uses bit metrics and path metrics to the decode processed output, to generate a decoded bit sequence. The receiver system uses the distance measure to reduce the size of the bit metrics and the size of the path metrics to improve the performance of said convolutional decoder.

The present invention provides a method and an apparatus may increase or extend the range of wireless communication cells for a given throughput in a downlink of a wireless communication system. When transmitting data in a downlink of a plurality of access point cells in a wireless local area network (WLAN), the range of the downlink may be increased for a given throughput under one or more radiated power constraints. The method includes providing a plurality of antennas at an access point to transmit the data to a wireless unit under at least one of a first and a second radiated power constraints. The method further includes using the plurality of antennas for beamforming over a group of sub-carriers subject to the first and / or second radiated power constraints. Under one or more radiated power constraints, a multiple antenna based beamforming may extend the range of a wireless communication for a user of a wireless unit that may be located within a coverage area across the plurality of access point cells of a Wi-Fi network associated with the WLAN. A joint beamforming optimized over all of sub-carriers may account for a European regulation restriction into at least one of an averaged and a spectral density Equivalent Isotropic Radiated Power (EIRP) constraint. In this way, an Orthogonal Frequency-Division Multiplexing (OFDM) based joint beamformer may provide a significant performance improvement and range extension.

An RF transmitter uses two digital-to-RF conversion modules to convert digital baseband signals into RF signals. In Cartesian mode, baseband signals are conveyed to the conversion modules for RF conversion. In polar mode, baseband signals are converted into amplitude and phase data parts. Phase data part is converted into I and Q data parts to be converted by the conversion modules into RF signals, which are modulated in a power amplifier by amplitude data part through the power supply of the power amplifier. Each digital-to-RF module uses parallel unit cells to perform D / A conversion function and upconversion function by an IF signal. Each unit cell, adapted to receive a control voltage indicative of a data signal value, is a mixer cell type converter having a differential data switch section connected in series to a differential LO-switch pair. LO-switch is further connected in series to a current source.