Modulated-carrier systems

HELECTRICITY H04Electric communication H04LTRANSMISSION OF DIGITAL INFORMATION

H04L27/00Modulated-carrier systems

H04L27/0002analog front ends; means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0004using wavelets H04L27/0006Assessment of spectral gaps suitable for allocating digitally modulated signals H04L27/0008arrangements for allowing a transmitter or receiver to use more than one type of modulation H04L27/001using chaotic signals H04L27/0012arrangements for identifying the type of modulation H04L27/0014Carrier regulation H04L27/01Equalisers H04L27/02Amplitude-modulated carrier systems H04L27/04Modulator circuits Transmitter circuits H04L27/06Demodulator circuits Receiver circuits H04L27/063Superheterodyne receivers H04L27/066Carrier recovery circuits H04L27/08Amplitude regulation arrangements H04L27/10Frequency-modulated carrier systems H04L27/103Chirp modulation H04L27/106M-ary FSK H04L27/12Modulator circuits Transmitter circuits H04L27/122using digital generation of carrier signals H04L27/125using a controlled oscillator in an open loop H04L27/127using a controlled oscillator in a feedback loop H04L27/14Demodulator circuits Receiver circuits H04L27/142Compensating direct current components occurring during the demodulation and which are caused by mistuning H04L27/144with demodulation using spectral properties of the received signal H04L27/148using filters, including PLL-type filters H04L27/152using controlled oscillators H04L27/1525using quadrature demodulation H04L27/156with demodulation using temporal properties of the received signal H04L27/1563using transition or level detection H04L27/1566using synchronous sampling H04L27/16Frequency regulation arrangements H04L27/18Phase-modulated carrier systems H04L27/183Multiresolution systems H04L27/186in which the information is carried by both the individual signal points and the subset to which the individual signal points belong H04L27/20Modulator circuits Transmitter circuits H04L27/2003for continuous phase modulation H04L27/2007in which the phase change within each symbol period is constrained H04L27/201in which the allowed phase changes vary with time H04L27/2014in which the phase changes in a piecewise linear manner during each symbol period H04L27/2017in which the phase changes are non-linear H04L27/2021in which the phase change per symbol period is not constrained H04L27/2025in which the phase changes in a piecewise linear manner within each symbol period H04L27/2028in which the phase changes are non-linear H04L27/2032for discrete phase modulation H04L27/2035using a single or unspecified number of carriers H04L27/2039using microwave technology H04L27/2042with more than two phase states H04L27/2046in which the data are represented by carrier phase H04L27/205in which the data are represented by the change in phase of the carrier H04L27/2053using more than one carrier H04L27/2057with a separate carrier for each phase state H04L27/206using a pair of orthogonal carriers H04L27/2064using microwave technology H04L27/2067with more than two phase states H04L27/2071in which the data are represented by the carrier phase H04L27/2075in which the data are represented by the change in carrier phase H04L27/2078in which the phase change per symbol period is constrained H04L27/2082for offset or staggered quadrature phase shift keying H04L27/2085with more than one phase shift per symbol period H04L27/2089with unbalanced quadrature channels H04L27/2092with digital generation of the modulated carrier (does not include the modulation of a digitally generated carrier) H04L27/2096Arrangements for directly or externally modulating an optical carrier H04L27/22Demodulator circuits Receiver circuits H04L27/223Demodulation in the optical domain H04L27/227using coherent demodulation H04L27/2271wherein the carrier recovery circuit uses only the demodulated signals H04L27/2272using phase locked loops H04L27/2273associated with quadrature demodulation H04L27/2275wherein the carrier recovery circuit uses the received modulated signals H04L27/2276using frequency multiplication or harmonic tracking H04L27/2277using remodulation H04L27/2278using correlation techniques H04L27/233using non-coherent demodulation H04L27/2331wherein the received signal is demodulated using one or more delayed versions of itself H04L27/2332using a non-coherent carrier H04L27/2334using filters H04L27/2335using temporal properties of the received signal H04L27/2337using digital techniques to measure the time between zero-crossings H04L27/2338using sampling H04L27/24Half-wave signalling systems H04L27/26Systems using multi-frequency codes H04L27/2601Multicarrier modulation systems H04L27/2602Signal structure H04L27/2604Multiresolution systems H04L27/2605Symbol extensions H04L27/2607Cyclic extensions H04L27/2608Allocation of payload H04L27/261Details of reference signals H04L27/2611Distribution thereof H04L27/2613Structure of the reference signals per se H04L27/2614Peak power aspects H04L27/2615Reduction thereof using coding H04L27/2617using block codes H04L27/2618Reduction thereof using auxiliary subcarriers H04L27/262Reduction thereof by selection of pilot symbols H04L27/2621Reduction thereof using phase offsets between subcarriers H04L27/2623Reduction thereof by clipping H04L27/2624by soft clipping H04L27/2626Arrangements specific to the transmitter H04L27/2627Modulators H04L27/2628Inverse Fourier transform modulators H04L27/263modification of IFFT/IDFT modulator for performance improvement H04L27/2631with polyphase implementation H04L27/2633using partial FFTs H04L27/2634IFFT/IDFT in combination with other circuits for modulation H04L27/2636with FFT/DFT H04L27/2637with direct modulation of individual subcarriers H04L27/2639Discrete cosine transform modulators H04L27/264Filterbank multicarrier [FBMC] H04L27/2642Wavelet transform modulators H04L27/2643using symbol repetition H04L27/2644with oversampling H04L27/2646using feedback from receiver for adjusting OFDM transmission parameters H04L27/2647Arrangements specific to the receiver H04L27/2649Demodulators H04L27/265Fourier transform demodulators H04L27/2652with polyphase implementation H04L27/2653with direct demodulation of individual subcarriers H04L27/2655Synchronisation arrangements H04L27/2656Frame synchronisation H04L27/2657Carrier synchronisation H04L27/2659Coarse or integer frequency offset determination and synchronisation H04L27/266Fine or fractional frequency offset determination and synchronisation H04L27/2662Symbol synchronisation H04L27/2663Coarse synchronisation H04L27/2665Fine synchronisation H04L27/2666Acquisition of further OFDM parameters H04L27/2668Details of algorithms H04L27/2669characterised by the domain of operation H04L27/2671Time domain H04L27/2672Frequency domain H04L27/2673characterised by synchronisation parameters H04L27/2675Pilot or known symbols H04L27/2676Blind H04L27/2678using cyclostationarities H04L27/2679Decision-aided H04L27/2681characterised by constraints H04L27/2682Precision H04L27/2684Complexity H04L27/2685Speed of convergence H04L27/2686Range of frequencies or delays tested H04L27/2688Resistance to perturbation H04L27/2689Link with other circuits H04L27/2691involving interference determination or cancellation H04L27/2692with preamble design H04L27/2694adaptive design H04L27/2695with channel estimation H04L27/2697in combination with other modulation techniques H04L27/2698double density OFDM/OQAM system H04L27/28with simultaneous transmission of different frequencies each representing one code element H04L27/30wherein each code element is represented by a combination of frequencies H04L27/32Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26 H04L27/34Amplitude- and phase-modulated carrier systems H04L27/3405Modifications of the signal space to increase the efficiency of transmission H04L27/3411reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set H04L27/3416in which the information is carried by both the individual signal points and the subset to which the individual points belong H04L27/3422in which the constellation is not the n - fold Cartesian product of a single underlying two-dimensional constellation H04L27/3427in which the constellation is the n - fold Cartesian product of a single underlying two-dimensional constellation H04L27/3433using an underlying square constellation H04L27/3438using an underlying generalised cross constellation H04L27/3444by applying a certain rotation to regular constellations H04L27/345Modifications of the signal space to allow the transmission of additional information H04L27/3455in order to facilitate carrier recovery at the receiver end H04L27/3461in order to transmit a subchannel H04L27/3466by providing an alternative to one signal point H04L27/3472by switching between alternative constellations H04L27/3477by using the outer points of the constellation or of the constituent two-dimensional constellations H04L27/3483using a modulation of the constellation points H04L27/3488Multiresolution systems H04L27/3494using non - square modulating pulses, e.g. using raised cosine pulses; Partial response QAM H04L27/36Modulator circuits Transmitter circuits H04L27/361Modulation using a single or unspecified number of carriers H04L27/362Modulation using more than one carrier H04L27/363using non - square modulating pulses, modulators specifically designed for this H04L27/364Arrangements for overcoming imperfections in the modulator H04L27/365Modulation using digital generation of the modulated carrier (not including modulation of a digitally generated carrier) H04L27/366Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator H04L27/367using predistortion H04L27/368adaptive predistortion H04L27/38Demodulator circuits Receiver circuits H04L27/3809Amplitude regulation arrangements H04L27/3818using coherent demodulation H04L27/3827in which the carrier is recovered using only the demodulated baseband signals H04L27/3836in which the carrier is recovered using the received modulated signal or the received IF signal H04L27/3845using non - coherent demodulation H04L27/3854using a non - coherent carrier, including systems with baseband correction for phase or frequency offset H04L27/3863Compensation for quadrature error in the received signal H04L27/3872Compensation for phase rotation in the demodulated signal H04L27/3881using sampling and digital processing, not including digital systems which imitate heterodyne or homodyne demodulation H04L27/389with separate demodulation for the phase and amplitude components