300 results about "Qam modulation" patented technology

A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.

The present disclosure provides a method of carrier phase error removal associated with an optical communication signal. The method includes estimating and removing a first phase angle associated with an information signal using coarse phase recovery, the information symbol being associated with a digital signal, the digital signal representing the optical communication signal; estimating a carrier frequency offset between a receiver light source and a transmitter light source by using the estimated first phase angle, the carrier frequency offset being associated with the information signal; removing carrier phase error associated with the carrier frequency offset; and estimating and removing a second phase angle associated with the information signal, the estimated second phase angle being based on the estimated first phase angle and the estimated carrier frequency offset.

The invention provides a method for sending channel quality indication. The method comprises that: channel quality indication supporting a 256 quadrature amplitude modulation (QAM) mode is newly increased; and user equipment receives a pilot signal sent by a base station, carries out channel measurement according to the pilot signal and feedbacks current channel quality indication to the base station. Besides, provided is an apparatus for sending channel quality indication. According to the invention, a 256 QAM modulation mode is supported and the system throughput is improved.

A method of baseband/passband digital modulation for a data transmission system wherein a plurality of data symbols is transmitted over a transmission channel at a symbol rate. The method comprises the following steps: (1) generating a plurality of I and Q components of symbols by mapping an input bit stream comprising a plurality of digital codewords into a QAM constellation; (2) selecting a passband or a baseband mode; and (3) generating an analog output signal in the passband or baseband mode. The step of selecting the passband or the baseband mode depends on the complexity of QAM constellation. If QAM constellation includes less than 64 QAM plant points, the passband mode is selected, and if QAM constellation includes more than 64 QAM plant points, the baseband mode is selected. If the QAM constellation includes less than 64 QAM plant points, initially selecting the passband mode until a D/A conversion speed reaches a maximum passband conversion speed, and until an output symbol rate reaches a maximum passband symbol output rate, and subsequently switching to the baseband mode in order to double the maximum passband conversion speed and to double the maximum passband symbol output rate.

The invention provides a block-encoded modulation scheme using multi-level partitioning techniques. This scheme is made transparent to phase ambiguities of ±pi/2 and of pi, by means of differential encoding and appropriate mapping, it is applicable to 16-QAM modulation, and it has theoretical encoding gain that is optimal for the rate of the code. The decoder associated with this scheme uses the Wagner algorithm which is much less complicated to implement than the Viterbi algorithm or than the Reed-Solomon algorithm.

In a QAM demodulator including an adaptive equalizer, a method of carrier tracking comprising the following steps is disclosed: (A) sampling a QAM signal received from a transmission channel; (B) recovering a symbol clock function from the sampled QAM signal; (C) applying the sampled QAM signal to the adaptive equalizer in order to obtain a QAM equalized signal in a Blind Equalization (BE) mode; (D) using a slicer to locate a nearest plant point for the QAM Blind equalized signal for each recovered symbol clock; (E) using a complex conjugate multiplier to obtain an instantaneous inphase component and an instantaneous quadrature component of a phase angle error signal; (F) using a linear phase detector to obtain an instantaneous phase angle error for each symbol clock; (G) averaging the instantaneous phase angle error signal by using a carrier loop filter; (H) using a complex multiplier to insert an inverse of the averaged phase angle error signal into the QAM Blind equalized signal to compensate for the carrier phase angle error; and (I) repeating the steps (D-H) to close a carrier frequency loop.

Distributed CMTS device for a HFC CATV network serving multiple neighborhoods by multiple individual cables, in which the QAM modulators that provide data for the individual cables are divided between QAM modulators located at the cable plant, and remote QAM modulators ideally located at the fiber nodes. A basic set of CATV QAM data waveforms may be transmitted to the nodes using a first fiber, and a second set of IP/on-demand data may be transmitted to the nodes using an alternate fiber or alternate fiber frequency, and optionally other protocols such as Ethernet protocols. The nodes will extract the data specific to each neighborhood and inject this data into unused QAM channels, thus achieving improved data transmission rates through finer granularity. A computerized “virtual shelf” control system for this system is also disclosed. The system has high backward compatibility, and can be configured to mimic a conventional cable plant CMTS.

A headend transmitter that transmits 1024 QAM including a 256 QAM modulator which has been modified to have more aggressive forward error correction processing. The 256 QAM modulator outputs 256 QAM points to a summer. Another data modulator receives additional data to be transmitted in a separate, substantially less complex constellation. This modulator processes the additional data to do forward error correction thereon and then maps the encoded data into a less complex constellation such as QPSK, 16 QAM etc. The additional data constellation points are then amplified in a variable gain amplifier and fed to a summer where each additional data point is added by vector summation to one 256 QAM point. The output 1024 QAM point is filtered and shifted to the desired transmission frequency. Legacy cable modem receivers can still receive the 256 QAM point since the addition of the new data just appears to be noise which they can overcome using the parity bits encoded in the transmitted symbols. 1024 QAM cable modem receivers receive both the 256 QAM points and the new data points and output both.

In a communication method, a sequence of information bits is encoded into systematic bits and parity bits. The systematic bits and the parity bits are grouped in output blocks, each output block to be assigned to an address of a constellation scheme. The addresses include addresses that are more prone to error and address that are less prone to error so that the symbols are grouped such that bits in groups of consecutive bits of the sequence of information bits are not all assigned to addresses that are more prone to error.

A Cellular network system wherein the physical layer as defined in 802.16a includes means for its optimization for mobile operators for improved reliability, coverage, capacity, user location, fully scalability, and mobility from 2-6 Ghz, while working in a reuse of 1. The same RF frequency is allocated to all sectors in the cell. The system further includes means for its operation in a Coordinated Synchronous mode, wherein permutations, collisions and averaging interferences from other cells cause limitations on the use of high QAM modulations, which sometimes can increase capacity up to three times (64 QAM instead QPSK).

The modulation indication bit is interpreted as a QPSK/xQAM modulation indication if both the user equipment and the serving cell support 64QAM modulation, such that if QPSK is indicated, the 7 code-set information bits in the HS-SCCH part 1 structure is interpreted as is presently interpreted today as defined in the 3GPP release 5 specification, and if xQAM is indicated, the 7 code-set information bits in the HS-SCCH part 1 structure is interpreted such that only 6 bits are used for code information and one bit is stolen for use for the 16QAM/64QAM selection.

Distributed and highly software reconfigurable CMTS (CMRTS) device, based on MAC and PHY units with FPGA and DSP components, for a HFC CATV network. The various CATV RF modulators, such as QAM modulators, may be divided between QAM modulators located at the cable plant, and remote QAM modulators ideally located at the fiber nodes. A basic set of CATV QAM data waveforms may optionally be transmitted to the nodes using a first fiber, and a second set of IP/on-demand data may be transmitted to the nodes using an alternate fiber or alternate fiber frequency, and optionally using other protocols such as Ethernet protocols. The nodes will extract the data specific to each neighborhood and inject this data into unused QAM channels, thus achieving improved data transmission rates through finer granularity. A computerized “virtual shelf” control system for managing and reconfiguring the FPGA and DSP based CMTRS units is also disclosed.

A modulation processing method, a UE and a base station are disclosed; wherein, the base station transmits a high-layer configuration signaling to the UE, wherein the high-layer configuration signaling is used to indicate whether to support a high-order Quadrature Amplitude Modulation (QAM) modulation scheme, wherein the high-order QAM modulation scheme is a modulation scheme of M QAM, wherein M is a number greater than 64. With a high-layer configuration signaling indicating whether to support the high-order QAM, the high-order QAM modulation scheme is supported on the basis of being compatible with existing wireless transmission networks, and the peak data rate and the spectral efficiency are improved

System and method to extend the data carrying capacity of a hybrid fiber cable (HFC) network by adding wideband RF signal capability above 1 GHz, and replacing at least some CATV active devices such as amplifiers with a new type of Coax Domain Node (CDN) device that acts to segment the CATV cable portion of the HFC network into a series of smaller domains. The CDN generally filter RF signals from 5-865 MHz, while amplifying and passing RF signals over 1 GHz. Upstream capability is enhanced because the CDN intercept 5-42 MHz upstream signals from each domain and convert to 1 GHz+ signals. Downstream capability is also enhanced because the CDN can take efficiently encoded 1 GHz+ digital data, QAM modulate it, and locally inject into each domain without crosstalk between domains. The system pushes data management and downstream from the head end to the CDN, creating more throughput.

A timing recovery device for CAP/QAM modems includes an equalizer filter designed to monitor the movement of the filter coefficients within a memory buffer and to adjust the relative position of the filter coefficients within the memory buffer so that the coefficients remain substantially centered within the buffer.

Producing advanced HFC CATV cable systems while easing the burden of backward compatibility. The system improves CATV data carrying capacity by moving RF QAM modulators from the cable head end to various individually or group addressed optical fiber nodes supplying neighborhood CATV cables, and sending data from the cable head IP backbone to the nodes over optical fiber as IP data packets. For high backward compatibility, the system digitizes legacy RF waveforms, or demodulates legacy QAM waveforms to QAM symbols, also transmits these over the optical fiber as IP data packets, and then reconstitutes back to original waveforms as needed. The system is thus able to easily handle legacy NTSC, FM, QPSK waveforms and do partial (QAM symbol level) compression of legacy QAM waveforms to and from multiple nodes without requiring additional optical fiber wavelengths. The system may use non-standard upstream/downstream CATV frequency splits, filter bank receivers, and FPGA/DSP/ASIC methods.

Distributed and software reconfigurable remote CMTS (CMRTS) device, based on MAC and PHY units with FPGA and DSP components, for a HFC CATV network. The various CATV RF modulators, such as QAM modulators, may be located entirely at the fiber nodes if desired. Although a basic set of CATV QAM data waveforms may optionally be transmitted to the nodes using a first fiber, in a preferred embodiment, all data may be transmitted to the nodes using other protocols such as Ethernet protocols. The nodes will extract the data specific to each neighborhood and inject this data into the cable portion of the system as RF waveforms, such as RF QAM channels. A computerized “virtual shelf” control system for managing and reconfiguring the FPGA and DSP based CMTRS units, as well as a new type of edge router based all-digital virtual head end (virtual converged cable access platform) is also disclosed.

The invention relates to the technical field of communication anti-jamming, in particular to a superposition coded modulation (SCM) technology communication system, subcarrier index modulation (SIM) and related time domain detecting technologies. According to an SCM method based on SIM-orthogonal frequency division multiplexing (OFDM), ideas of SIM-OFDM and spatial modulation (SM) are used as reference, a part of a string of bit data is used for transmission, the other part of the string of bit data is used as indexing bits, and the indexing bits are respectively coded. During transmission in an OFDM system, particular subcarrier is selected for transmitting data according to the bit data after coding of the indexing bits. A maximum likelihood method is used at a receiving end to obtain soft information of the indexing bits, and the indexing bits are decoded. Compared with prior SCM methods, the SCM method based on the SIM-OFDM has the advantages that the SCM superposition layers are reduced, the complexity is reduced, and error rate performances can be maintained or even improved to a certain degree. Meanwhile, the SCM is used for replacing quadrature amplitude modulation (QAM), and performances can be improved under the same transmission efficiency.

Data is transmitted across an optical fiber communications system by splitting an incoming tributary into multiple low-speed data channels, modulating each of these into a stream of symbols (e.g., by using QAM modulation) and then frequency division multiplexing a number of symbol streams into a single high-speed channel to be transmitted across a fiber. The receiver reverses this process. In order to preserve the jitter tolerance for the overal system, reference clocks are used to remove unwanted jitter in the timing of the system.

A method for determining the distance between a base station (SLG) and a mobile object (DT1-DT3). A HF carrier frequency and an offset frequency (df) are predetermined for a QAM modulation. The HF carrier frequency is increased and decreased by the offset frequency in sequence over time in such a way that the HF carrier base frequencies (fo+df, fo−df) resulting in an HF carrier signal (TS) thus modulated exhibit an identical phase when the frequency is changed. The HF carrier signal is subsequently transmitted and simultaneously mixed (MIX) with an HF carrier signal (RS) that has been backscattered by the mobile object to obtain a carrier phase signal (PS). The corresponding carrier phase (PH1, PH2) for the two HF carrier base frequencies is determined in sequence over time. The difference (dPH) between these phases is used to calculate the distance between the base station and the respective mobile object.