292 results about "Qpsk modulation" patented technology

Binary and Quadrature Feher's Modulation (F-Modulation, or FMOD) Transmitter-Receiver systems and circuits exhibit reduced envelope fluctuation and peak radiation, and increased efficiency. A subclass of these systems has a constant envelope. They advantageously provide lower power operation with improved performance including robust BER performance, and compatibility with both linearly and nonlinearly amplified narrow spectrum, and without disadvantages of conventional BPSK, DBPSK QPSK and pi/4-QPSK. Feher's BPSK (FBPSK) is an improved efficiency transmitter which is compatible with conventional BPSK receivers. FBPSK modems are based on using quadrature structure where Q-channel data is inserted in quadrature with I-channel data for certain applications. The Q-channel data may be “offset” from the I-channel data by an amount selectable between zero and a specified time. Further improvement in the spectrum is attained using correlation between I and Q channels. FBPSK modem is shown to meet the IEEE 802.11 specified spectral direct sequence spread spectrum mask (−30 dB point) for wireless LAN, and leads to an output power gain of 6.5 dB over conventional BPSK modems. The cross-coupled quadrature FMOD structure is also suitable for continuous mode and for burst operated TDMA, FDMA, CDMA, WCDMA and CSMA Frequency Modulation Quadrature AM (QAM), QPSK and offset QPSK, as well as pi/4-shifted QPSK modems/processors. Reduced modulation index Gaussian FSK (GFSK), multilevel FM and cross-coupled Quadrature Amplitude Modulated (QAM) transmitters and combinations of these modulations and corresponding coherent demodulators are disclosed. Controlled rise and fall time descriptions of burst operated systems are included.

The invention provides a method and a device for sending physical uplink control signals in a time-division duplex system, the method comprises following steps: encoding the uplink control signals with a communication channel to obtain coded bits, modulating the coded bits with QPSK to obtain modulation symbols, transforming the modulation symbols with DFT to obtain symbols on a frequency domain,expanding the symbols on the frequency domain with time-domain through adopting a CAZAC root sequence to respectively obtain a first signal and a second signal which are sent on two time slots, mapping the first signal and the second signal on an information symbol which is corresponded with a PUCCH reference signal structure 2, and combining the information symbol and the reference signal into asignal which will be sent by a sub-frame. The invention can well satisfy the performance requirement and the covering requirement that a plurality of ACK/NACK can be sent on an uplink sub frame.

The invention discloses a micro/nano satellite measure and control communication integral transmitting and receiving system and a realization method thereof. The method comprises the following steps: 1) uplink signal processing: 11) receiving and processing radio-frequency signals to obtain analog intermediate-frequency signals; and 12) carrying out analog to digital conversion and digital underlocking on the analog intermediate-frequency signals and dividing into two paths of uplink digital intermediate-frequency signals, namely, one path of the signals is sent to a satellite-mounted computer by QPSK (quadrate phase shift keying) demodulation and uplink protocol processing so as to finish uplink data transmission, and the other path of the signals is subjected to the PM (phase modulation) demodulation to obtain side sound signals and PSK (phase shift keying) remote signals, and the PSK remote signals are subjected to BPSK (binary phase shift keying) demodulation to convert into a remote control command which is sent to the satellite-mounted computer so as to finish the remote control; and 2), downlink signal processing: 21), acquiring two paths of data from the satellite-mounted computer and a storage unit, namely, one path of data which is subjected to downlink protocol processing, BPSK modulation, combination with the side sound signals and downlink measure and control carrier PM modulation is combined with the other path of data which is subjected to the downlink protocol processing and the QPSK modulation to enter a satellite-ground radio-frequency emission channel; and 22) converting into radio-frequency signals to finish the remote measure and the downlink data transmission.

Aspects of a method and system for providing visually related content description to physical layer are provided. A MAC layer and/or a PHY layer in a wireless communication device may be controlled for processing at least one media object in an audiovisual scene based on metadata information that corresponds to the audiovisual scene. The metadata information may result from, for example, MPEG-4 encoding of the audiovisual scene. Each media object may be forward error corrected based on a determined priority level, such as foreground and background priorities, that results from the metadata information. In this regard, the number of bits utilized for protection and/or the RF modulated scheme may be selected in accordance with the priority level. The RF modulation may be, for example, QPSK modulation or 16 QAM modulation. The metadata information and the processed media objects may then be wireless communicated.

A high-speed optical transmitter comprises multiple digital lanes that are provided to a bank of digital-to-analog converters. The analog signals are then used to Phase Shift Keyed (PSK) modulation using a Chirp Managed Laser (CML)-based transmitter, and potentially using dual polarization. A corresponding optical receiver receives the sequence of optical signals at a demodulator. For each polarization, the demodulator includes a corresponding demodulation channel that is configured to demodulate that polarization component of the optical signal into one or more signal components. Each of these signal components is converted into a corresponding digital signal using a corresponding analog-to-digital converter. In the case of higher-order PSK modulation (e.g., 8PSK or higher), for each polarization, the analog converter has a lower sampling rate than for QPSK modulation.

The invention relates to a method for feeding back ACK/NACK information. The method comprises the following steps that: when user equipment (UE) correctly receives the data of a first downlink subframe sent by a base station and the ACK/NACK feedback information on other subframes is NACK or DTX, the UE sends the ACK/NACK feedback information on the first subframe, and indicates at the same time that the ACK/NACK feedback information on other subframes is NACK or DTX and records the information as a first mode; and when the UE dost not correctly receive the data of the first downlink subframesent by the base station or the ACK/NACK feedback information on other subframes is ACK, the UE selects a used ACK/NACK channel from a plurality of ACK/NACK channels on the basis of QPSK modulation totransmit the ACK/NACK information on a plurality of downlink subframes and records the information as a second mode. The method utilizes a mechanism for detecting missed data transmission to supporta multi-bit feedback method of ACK/NACK information on multiple subframes, and can be converted into a feedback method for feeding back the ACK/NACK information on a single subframe without confusion.

The invention discloses a method for transmitting service data in HSDPA, a device and a system thereof. UE time slot track is notified to distribute information by high-level signaling, by adopting synchronous mode of hybrid automatic repeat request, permanently adopting incremental redundancy versions of QPSK modulation and predefinition used during different transmission times. A base station only transmits control information including cyclical sequence number of a high-speed shared control channel, size index of transmission blocks and user identifications to UE on a physical control channel in the first transmission of data. Regarding small data packet service, such as transmission of VoIP service, information content of the control information is reduced, and transmission times of the control information during transmitting process can be greatly reduced, therefore, network load is reduced, and transmission efficiency of data of the small data packet service in HSDPA is improved.

An object of the present invention is to provide a method for suppressing peak power at a high encoding rate in a multi-carrier transmission system.

The present invention provides a transmitter for transmitting a multi-carrier signal, in which when generating 128 patterns used to suppress the peak power of 8-bit sub-carrier mapping signals from 7-bit information bits in a encoding unit 9, a sub-carrier generation unit 11, for example, divides the signal point of QPSK modulation into orthogonal groups, generates a sub-carrier mapping signal in which a part of sub-carriers is dependent on the signal point of another sub-carrier and a receiver for receiving such a multi-carrier signal.

A system for adaptive modulation and power control in a wireless communication system includes a downlink from a base station to a remote unit and an uplink from the remote unit to the base station. The base station incorporates adaptive modulation on the downlink while power control is not utilized. In contrast, the remote unit utilizes a fixed modulation level and power control to control transmit power levels. In an exemplary embodiment, the remote unit uses QPSK modulation. The header of uplink messages include data from the remote unit to instruct the base station which modulation level to utilize on downlink transmissions. This provides closed-loop, non-iterative modulation control. In an exemplary embodiment, the modulation selection data is included in all uplink messages so that adaptive modulation can be communicated on a frame-by-frame basis.

A demodulation method for establishing clock synchronization within a short period of time from a received signal modulated by π/4-shift QPSK modulation that contains a synchronization establishment signal wherein the change in phase periodically alternates between positive and negative, and for demodulating the received signal. The method includes establishing synchronization from the received signal based on the timing of changes in the positive/negative polarity of the change in phase of the synchronization establishment signal contained in the received signal, and demodulating the received signal.

The invention provides a communication link used for a telemetry and telecontrol communication system. An uplink broadcasing and downlink TDMA (time division multiple access) mode is adopted to solve the measurement and control problems of a single ground station for multiple aircrafts. A downlink adopts hybrid spread spectrum BPSK (binary phase shift keying) with multiple stages of adjustable gain for modulation, an uplink adopts coded spread spectrum QPSK (quadrature phase shift keying) with fixed gain for modulation, so that the anti-interference, anti-interception and anti-capturing capacity of a wireless link is improved, and asymmetry of the uplink and the downlink is considered. Both the uplink and the downlink adopt a single-pulse modulation symbol packet transmission mode, a fixed interval is inserted into every two adjacent symbol pulses, and accordingly, the spread spectrum signal capturing, tracking and synchronizing complication of receivers is reduced. Non-coherent demodulation is adopted, a complicated carrier synchronization problem is avoided, and the design and project realization of the receivers are further simplified. The complicated carrier synchronization problem is avoided, and wireless communication between a single ground station device and multiple telecontrol terminal devices is realized.

In a multi-carrier communication apparatus, it is an object of the invention to increase the amount of data per unit time greatly with the band width kept unchanged. A modulator (102) sequentially performs primary modulation of data (101) which are first transmitted data on the basis of, for example, QPSK modulation. A pattern generating unit (104) generates a pattern of particular signals which is to be allocated to sub-carriers of a matrix formed by arranging a plurality of sub-carriers arranged in the direction of a frequency axis into a plurality of symbols in the direction of a time axis. The pattern is determined based on data (103) which are second transmitted data. A mapping unit (105) allocates the sub-carriers modulated by the data (101) at the modulator (102) and the pattern of the particular signals to the sub-carriers of the matrix.

A turbo encoding section 102 turbo-encodes transmission data, outputs systematic bit data to a first modulation section 103a and outputs parity bit data to a second modulation section 104. The first modulation section 103a always QPSK-modulates systematic bit data. The second modulation section 103b adaptively modulates parity bit data. The control section 101 outputs a control signal for carrying out 16 QAM modulation to the second modulation section 103b when the RSSI value is equal to or higher than a threshold and outputs a control signal for carrying out QPSK modulation to the second modulation section 103b when the RSSI signal value is less than the threshold. In this way, it is possible to further make the error rate characteristic compatible with the transmission efficiency.

The invention involves a parallel spread spectrum ('PSS') technique of spreading orthogonal encoded data. In a preferred embodiment, a method and system for communicating data comprises encoding and spreading a data stream using a scheme employing orthogonal Walsh functions, and thereby segmenting the data stream into multiple bit data packets representing one of a number of true or inverted Walsh codes. The data stream is then differentially encoded for either BPSK or QPSK modulation, and spread using a PN-sequence. The parallel spread data stream is modulated for transmission to a receiver. At the receiver, the data stream is recovered by computing a cross correlation between the digitized data stream and a programmed sequence. One of the benefits of the PSS techniques over conventional communication systems is that additional processing gain plus data forward error correction can be simultaneously achieved.

The invention provides a remote underwater acoustic communication method based on soft-demodulation soft-decoding joint iteration. The method comprises the following steps that: a transmitting end performs low density parity check (LDPC) coding on a binary information sequence which is sent by a signal source, performs quaternary phase shift keying (QPSK) modulation and Gray mapping, maps code elements to one of four positions in a constellation diagram by taking two code elements as a group, performs Walsh-m composite sequence spectrum spreading to obtain a signal to be transmitted, and converts a digital signal to be transmitted into an underwater acoustic signal; and an underwater acoustic transducer at a receiving end converts the received underwater acoustic signal, de-spreads by using a composite sequence which is the same as that of the transmitting end to obtain a receiving signal, performs self-adaptation decision feedback equalization to obtain an amplitude fading complex signal, performs soft-demodulation soft-decoding joint iteration on the signal, stops joint iteration after set iteration frequency is reached, performs belief propagation (BP) decoding on an LDPC decoder and outputs a bit value to a sink. By the method provided by the invention, the reliability of remote underwater acoustic communication is improved. The method is applicable to the remote underwater acoustic communication.

Railway track circuit apparatus for train detection comprises a track circuit transmitter and a receiver, wherein the transmitter generates a QPSK modulated signal that is transmitted into a track circuit and which is detected by the receiver.

A device used for generating QPSK millimeter wave of radio frequency optical fiber transmission system consists of semiconductor laser of central station, polarization controller, optical phase modulator, optical comb fiber, optical QPSK modulator, optical branching unit/combining unit, optical detector of base station, narrow band band-pass filter, millimeter wave amplifier and millimeter wave antenna. Its optical modulating method for obtaining QPSK modulated millimeter wave signal is also disclosed.

The invention discloses a non-local-oscillator low-phase-noise microwave signal optical frequency-doubling generation device and method, and belongs to the technical field of microwave signal generation. According to the device and the method, a narrow-band microwave photonic filter is formed by utilizing an equivalent phase modulation characteristic of one double parallel Mach-Zehnder modulator (DP-MZM) integrated in a polarized multiplexed double parallel Mach-Zehnder modulator (DP-QPSK modulator) and a phase shifting fiber bragg grating (PS-FBG); and in an optoelectronic oscillator, generation of a frequency tunable low-phase-noise microwave resonance signal is implemented. Signal frequency doubling of the generated microwave resonance signal is implemented by the other DP-MZM integrated in the DP-QPSK modulator so as to generate a high-frequency microwave signal. The non-local-oscillator low-phase-noise microwave signal optical frequency-doubling generation device and method disclosed by the invention can overcome the defect of limitation of the electronic bottleneck of an electronic system in the aspect of generating the high-frequency low-phase-noise microwave signal, and implement generation of the low-phase-noise microwave signal with a magnitude of dozens of GHz and even hundreds of GHz.

The invention discloses a carrier synchronization system and a method of combining pilot frequency and iterative decoding. The system comprises a Turbo coding module, a multiplex module, a modulation module, a carrier estimation module, a demodulation module and an extension Turbo decoding module. The method includes the steps of receiving sequences, initial estimation, correcting signals, quadrature phase shift keying (QPSK) demodulation, data demultiplexing, Turbo decoding, hard decision, decoding termination conditions, data multiplexing, QPSK modulation and fine estimation. The carrier synchronization system and the method of the combining the pilot frequency and the iterative decoding have the advantages that the defect that in prior art, the frequency estimation accuracy is low caused by the fact that pilot frequency with the same number and maximum likelihood algorithm are utilized is overcome, the carrier frequency estimation accuracy is improved, simultaneously the disadvantage that in prior art, the output of a Turbo decoder is required to be recoded or subjected to nonlinear transformation is overcome, and the algorithm complexity of combining Turbo decoding and carrier synchronization process is reduced.

The invention relates to methods for transmitting and receiving a data bit stream in a communication system using a 16-QAM constellation. Further, an apparatus for performing the methods is provided. To provide a modulation and coding scheme using a signal space expansion and 16-QAM which improves the bit-error rate in comparison to QPSK modulated signals and still provides the possibility to implement coders and decoders with low complexity the invention suggests the use a 16-QAM constellation with specially selected mapping rules together with repetition coding (signal space expansion) and interleaving of the data stream to be transmitted.