273 results about "QAM" patented technology

In one embodiment, a receiver of the invention has an optical detector coupled to a digital processor. The optical detector is adapted to mix the received optical quadrature-amplitude modulation (QAM) signal with an optical local oscillator (LO) signal having a time-varying phase offset with respect to the carrier frequency of the QAM signal to produce two digital measures of the QAM signal. The digital processor is adapted to: (i) determine the amplitude and phase differentials for each QAM-symbol transition based on these digital measures; (ii) adjust each phase differential for an amount of phase drift associated with the time-varying phase offset; (iii) map each QAM-symbol transition onto a constellation point of a 2D decision map using the transition's amplitude differential and adjusted phase differential; and (iv) based on the mapping results, recover the data encoded in the optical QAM signal.

Certain embodiments of the invention may be found in a method and system for a vestigial side band (VSB), quadrature amplitude modulation (QAM), NTSC, out-of-band (OOB) receiver that is integrated in a single chip. The single chip integrated digital television (DTV) receiver provides plug and play DTV receiver capability for handling both North American digital cable television and digital terrestrial broadcast television compatible systems. The integrated DTV receiver may receive all standard-definition and high-definition digital formats (SDTV/HDTV) and an on-chip NTSC demodulator handles NTSC video. An output of the NTSC demodulator may be directed to an external broadcast television system committee (BTSC) or Zweiton M decoder, or it may be sent to an on-chip audio BTSC compliant decoder. The single chip integrated DTV receiver may also comprise an integrated out-of-band QPSK receiver, which may be adapted to, for example, handle a CableCard compliant with the CableCard Specification.

A hierarchical QAM system allows the transmission of different sources by embedding the relative constellation points. At the transmitter the constellations generated by the different sources are remapped by a grey coder and then combined. At the receiver, the different source data are decoded by using a corresponding grey code demapper.

Method and modem for fast timing recovery of transmitted data between a master χDSL modem and a slave χDSL modem, over a noisy, high loss, high distortion wiring. Transmitted QAM symbols are received and sampled at the slave modem. The sampled data is split into in-phase and quadrature channel, each of which is filtered by matched filter. The filtered outputs are sampled at twice the symbol rate and the lower and upper band edge components are extracted by modulating each of the sampled sequences of outputs with two discrete time sequences: cos(0.5 π n)=. . . 1,0,−1,0 . . . and sin(0.5 π n)=. . . 0,1,0,−1 . . . . Each of the resulting products is filtered with a first order low-pass filters and re-sampled again at the symbol rate. The Bit Error Rate is computed, and the slave modem switches from blind timing recovery mode, to data directed timing recovery mode, after the Bit Error Rate has sufficiently decreased.

The invention provides a uni-directional set-top cable box video-on-demand method making use of the passback of mobile communication network, which is that users use mobile communication network for visiting EPG server and examining the list of programs; a request for ordering programs is proposed; video-on-demand server sends the program stream to the IP-QAM equipment of users; IP-QAM modulates the program stream to the radio-frequency signal; and the program stream is received by the set box of the users for the playback. The video-on-demand method needs no double action transformation of cable, and extra computer network to realize the fast video-on-demand service.

The invention provides a combined modulation recognition method based on clustering and a support vector machine in order to overcome the shortcoming of low modulation recognition rate of a clustering algorithm with a low signal to noise ratio. According to the method, a characteristic parameter of a modulation signal is extracted by using the clustering algorithm according to a phase shift keying/quadrature amplitude modulation (PSK/QAM) mode based on a constellation diagram; and a modulation mode for a signal is recognized through the support vector machine, so that the modulation recognition rate of a system is increased. The method comprises the following steps of: aiming at the PSK/QAM mode based on the constellation diagram, reconstructing the constellation diagram of a receiving signal by using the clustering algorithm; and obtaining an effective function value, which can reflect an outstanding difference of modulation types under different clustering central numbers, as the characteristic parameter input into the support vector machine by constructing an effectiveness evaluation function. In order to overcome the shortcoming that two common algorithms of one to multiple and one to one have high calculation complexity when the support vector machine recognizes multiple types, the support vector machine is trained by adopting a hierarchical algorithm.

Available quadrature amplitude modulation (“QAM”) carriers transmittable by a base station to customer sites are substantially equally divided among the sites according to the expected quality of reception. ARQ transmissions from the sites are monitored as a measure of the quality of signals received by the sites. If the quality of received signals is unacceptable, the affected site is re-assigned to a higher quality QAM. In addition, if the quality of received signals is too high, the affected site is re-assigned to a lower quality QAM.

An wireless terminal includes a demodulating unit which comprises an FV (fading vector) estimating unit for receiving a CPICH spread/demodulated signal to output an FV signal with a reduced noise ratio; a phase synchronization unit for multiplying a PDSCH spread/demodulated signal with a complex conjugate of the FV signal to correct the phase offset of the PDSCH I and Q signals to send the resulting PDSCH I and Q signals to a multi-level QAM amplitude synchronization detection unit and to an amplitude demodulating unit; a first-quadrant transformation unit for collecting the second to fourth quadrant signals of the phase-synchronized PDSCH I and Q signals; and a threshold value detecting unit for calculating a multi-level QAM threshold value from the first quadrant signals and the FV signals to send the threshold signal to an amplitude demodulating unit. The amplitude demodulating unit effects amplitude demodulation to output multi-level QAM demodulated signals. The threshold value detecting unit previously assumes a plural number of probabilities as to which of the levels received data belongs to and, using a plural number of the data, raises the precision of the assumed data. The threshold value is estimated, using the frequencies and differences of the respective levels, from the assumed plural threshold values.

The invention discloses an optical transmitter supporting multiple modulation formats and a control method. The optical transmitter comprises a laser source, two parallel optical modulators, a waveform selection module, a drive amplification module, a bias control module, a master control module and an optical amplifier. The master control module is connected with the waveform selection module, the drive amplification module and the bias control module and transmits control information. The waveform selection module conducts series-parallel conversion on data to be modulated according to input modulation parameters and generates clock signals, drive amplification is conducted on the clock signals, and then the clock signals are then loaded to the optical modulator. The bias control module selects a proper bias working point according to the specified modulation format. The modulated optical signals are amplified by the optical amplifier and then are used as output of the transmitter. The optical transmitter can flexibly support multiple modulation formats only by utilizing binary data, switching between multiple modulation formats such as NRZ-2PSK, RZ-2PSK with the duty ratio of 50%, NRZ-QPSK, CSRZ-QPSK and 16 QAM is achieved, and the optical transmitter is suitable for high-speed and flexible optical fiber communication systems and networks in the future.

The invention relates to an optical orthogonal frequency division multiplexing communication method and a system thereof based on probabilistic shaping mapping, wherein the method comprises: generating a pseudo random binary bit stream PBRS signal; modulating the PRBS signal to obtain a PS-QAM complex signal; performing serial/parallel conversion, inverse fast Fourier transform and parallel/serialconversion on the PS-QAM complex signal to obtain a baseband OFDM signal, and obtaining an OFDM baseband signal with a cyclic prefix; modulating the OFDM baseband signal onto an optical carrier afterdigital/analog conversion to obtain a PS-OOFDM signal, and transmitting the signal to the optical fiber; converting the PS-OOFDM signal on the optical fiber into an analog OFDM electrical signal; performing analog/digital conversion on the analog OFDM electrical signal to obtain a digital OFDM signal, removing the cyclic prefix, and performing the inverse fast Fourier transform after parallel/serial conversion to obtain the PS-QAM complex signal; separating the real part and the imaginary part of the PS-QAM complex signal, and restoring the corresponding PBRS signal by de-mapping. The invention is capable of achieving shaping gain and improving the spectral efficiency of fiber communication.

The invention relates to the technical field of wireless communication, in particular to a large-scale multiple input multiple output (MIMO) uplink multi-user signal detection method and detection device and an MIMO receiving system. The large-scale MIMO uplink multi-user signal detection method comprises the steps of utilizing matched filtering to obtain an initial first estimation of a quadrature amplitude modulation (QAM) symbol sent by a user; after offsetting influence of the current user signal first estimation from an MIMO detection equation, utilizing a compressed sensing method to reconstruct sparse signals; performing a hard decision on signals obtained after the first estimation and the reconstructed signals are added so as to obtain a second estimation, and utilizing the second estimation to update the current first estimation; enabling the process to be subjected to iteration until iteration end conditions are met; adopting an approximate message passing algorithm to serve as a compressed sensing signal reconstructing algorithm, and simultaneously setting to-be-reconstructed signal prior probability distribution to be Bernoulli-uniform distribution. The large-scale MIMO uplink multi-user signal detection method has the advantages of being low in complexity and being easily achieved on a current hardware device and the like.

A QAM receiver for constellations having at least 16 symbols converts its received QAM signal into outputs including indications of the received symbols. A channel frequency response estimator responsive to outputs of the converter derives indications of estimates of effects of a link to the receiver on the phase and amplitude of the received signals. A processor responsive to outputs of the converter and the estimator (1) equalises the phases of the converter outputs, (2) scales the amplitude estimates by amounts determined by the amplitude associated with the separation of boundaries between symbols in the constellation, and (3) combines the phase equalised converter outputs and the scaled amplitude estimates to derive likely bit values of the received symbols.

The invention discloses a WIFI adapter and a digital television signal distribution system using the same. The WIFI adapter comprises a cable digital television signal receiving module and a wireless router switching module. The cable digital television signal receiving module comprises a QAM signal receiving module (A), a network transmission component (B) and a main control and data processing unit (C). The wireless router switching module comprises an Ethernet switching processing chip, a plurality of Ethernet signal transformers, a plurality of LAN interfaces, a WAN interface, a WIFI processing chip and a wireless signal receiving and dispatching antenna, wherein the Ethernet signal transformers, the LAN interfaces, the WAN interface and the WIFI processing chip are sequentially connected with the Ethernet switching processing chip, and the wireless signal receiving and dispatching antenna is connected with the WIFI processing chip. By means of the WIFI adapter and the digital television signal distribution system using the same, cable digital television services are expanded to various handheld and portable mobile devices, and the WIFI adapter and the digital television signal distribution system using the same bring great convenience to use for household users.

The optical modulator branches an input light into (2xN) lights in an optical branching section, and then phase modulates each of the branched lights in (2xN) phase modulating sections, and couples the phase modulated lights in an optical coupling section and generates a quadrature amplitude modulated (QAM) signal light having a 4 value. At this time, a relative difference of optical phases of the phase modulated lights is variably adjusted by an optical phase adjusting section. Moreover, a power ratio of the phase modulated lights is variably adjusted with an optical power adjusting section. As a result, it is possible to output 4 QAM signal light, with good signal quality.

The present invention describes a method for precoding using a precoder in a transmitter with multi-channel transmission for eg M-QAM (M > 4) modulated OFDM systems. The present invention describes a new precoding method suitable for use in eg MB-OFDM UWB systems, especially while targeting high data rates (above 480 Mbps). This may involve sending 16-QAM symbols instead of 4-QAM symbols. The method can also be used for some future wireless LANs (Local Area Networks) for future developments of 3G and 4G systems.

Disclosed is a demodulation apparatus for receiving signals by an adaptive modulation and coding method, and demodulating the signals, in an OFDMA based packet communication system, comprising: a QAM demapper for performing QAM demapping to the received signals by a modulation method using a maximum modulation ratio, until modulation methods for each of sub-channels are analyzed; a slot buffer for storing the data outputted from the QAM demapper; a channel decoder for decoding the data stored in the slot buffer and analyzing modulation methods for each sub-channels and transferring the analyzed modulation methods to the QAM demapper; and in at the same time, reading valid data from the data stored in the slot buffer, based on the analyzed modulation methods for each sub-channels, and demodulating the valid data.

The invention discloses a measurement and control signal and OFDM signal integrated waveform coexistence transmission system, and aims to provide a high-speed, real-time and reliable-transmission waveform coexistence transmission system, which is realized through the following technical scheme: in a data link, data information bits generated by a data information module are subjected to amplitudemodulation through an LDPC encoding module and a QAM module; an OFDM module generates an orthogonal multiplexing signal, and the OFDM signal and the measurement and control signal are subjected to rate adjustment by a power adjustment module to complete superposition of a power domain in a channel superposition module; a measurement and control information module on a measurement and control linkmaps a BPSK signal flow to a carrier after being modulated by a convolutional encoding module and a BPSK modulation module and spread by a spread spectrum module, and the power domain superposition ofthe BPSK signal flow and a data signal is completed in a channel superposition module after power adjustment. An integrated waveform signal in which the spread spectrum measurement and control signaland the OFDM signal coexist is formed through superposing.

The invention discloses a signal modulation and demodulation method based on constellation structure optimization and honeycomb-like region judgment. The method comprises the following steps: converting bit data from one path of data into multiple paths of parallel data through serial-to-parallel conversion; then carrying out distribution matching to obtain non-uniformly distributed QAM symbols; performing constellation mapping according to a designed structure-optimized constellation mapping rule by using probability shaping and combining a Gray-like mapping rule; modulating the QAM symbol information after constellation mapping to an optical carrier, then transmitting the QAM symbol information to a receiving end, and restoring the QAM symbol information after constellation mapping by the receiving end to obtain QAM symbol information after constellation mapping; determining a honeycomb-like constellation judgment area according to the positions of the constellation points, and removing the dispersion phenomenon of the QAM symbol information in the transmission process; and then performing the constellation de-mapping, inverse distribution matching and parallel-to-serial conversion successively to obtain bit data. According to the method, the anti-noise performance of the modulation format and the bit error rate performance of the system are improved.

The invention discloses a low-complexity demapping algorithm for cross constellation QAM (Quadracture Amplitude Modulation) in a G. HN (G. home Network) standard. The algorithm is used for reducing the demapping complexity of high-ranking cross constellation QAM in the G. HN standard, expanding the application scenes of the high-speed data transmission of the high-ranking cross constellation QAM, measuring the contribution of reference constellation points to demapping through contribution weight, and narrowing search scopes to the reference constellation points with large contribution weight, so as to effectively lowering demapping complexity of the high-ranking cross constellation QAM. The algorithm can make full use of channel estimation information, and assist self-adaptation to choose the search scopes, thereby narrowing down the search scopes, effectively reducing the demapping complexity of the high-ranking cross constellation QAM, reaching favorable balance between algorithm complexity and performance, and laying the foundation for expanding the application scenes of the high-ranking cross constellation QAM.

The invention discloses an OFDM encryption method based on a composite chaotic system and exclusive-OR operation. According to the method, Logistic mapping, Sine mapping and tent mapping are combined;a new composite discrete chaotic system is constructed; a chaotic sequence generated by the new system is used to carry out double encryption on a complex symbol after QAM mapping of the OFDM communication system; firstly, bitwise exclusive OR operation is adopted, secondly, a scrambling matrix is adopted for scrambling, after first encryption, a constellation diagram obtained after QAM mapping is changed into 49 constellation points from original 16 points, and an obvious confusion effect is achieved; and after the second encryption, the constellation points after the first encryption are further disrupted, inverse operation is performed at a receiving end according to the same chaotic sequence for decryption, and the bit error rate after decryption is within an acceptable range. According to the encryption scheme, the size of the disturbance matrix can be dynamically adjusted according to the size of the sent data, the flexibility is high, and violent attacks can be effectively prevented.

Systems and methods relating to the use of a Transport Block Size (TBS) table that supports 256 Quadrature Amplitude Modulation (QAM) in a cellular communications network are disclosed. In some embodiments, a wireless device determines a TBS for a downlink transmission from a radio access node to the wireless device using a TBS table that supports both a first set of modulation schemes and 256QAM. The TBS table comprises a first set of rows from a preexisting TBS table that supports the first set of modulation schemes but not 256QAM and a second set of rows added to the preexisting TBS table to provide the TBS table, where the second set of rows substantially reuse TBS values from the first set of rows. The wireless device receives the downlink transmission from the radio access node according to the Downlink Control Information (DCI) and the TBS determined for the downlink transmission.

Method and system for extracting soft estimates of DCM or 16-QAM modulated symbols that are received from a noisy channel. Optimal soft demapping rules are approximated using equations that are division-free and eliminate the need for implementing exponential and logarithmic functions that are inconvenient for hardware implementation.

The invention discloses a PS-64-QAM IMDD transmission method and system based on polar code coding. The method is used in a transmitting end, and comprises the steps: inputting binary bits which are uniformly distributed into a PS encoder, and creating a transmission mode lookup table, thereby generating K data bits and M selection bits; performing pseudo-random interleaving operation on the K bits, and inputting the K bits into a system polarization code encoder. The invention has the beneficial effects that experiments prove that in an IM/DD 64-QAM OFDM transmission system, the performance of the system is greatly improved through probability shaping and PAPR suppression in combination with system polarization code error correction. It can be seen that 7dB and 4dB performance improvements are obtained under the condition that the BER is 3.8 * 10 <-3 > before FEC and after FEC according to the scheme of the invention. Moreover, the redundant information of the PS and the SLM is skillfully put into the frozen bit of the polar code, so the redundancy of the whole transmission system is ensured to be constant.