In transmitter apparatus for a digital television broadcasting system, internet-protocol (IP) packets of digital television information are subjected to multilevel coding (MLC) before being Gray-mapped to quadrature-amplitude-modulation (QAM) constellations. The constituent codes of the MLC comprise respective low-density parity-check (LDPC) inner coding. Preferably, the LDPC inner coding is LDPC convolutional coding. The QAM constellations are used in coded orthogonal frequency-division modulation (COFDM) of plural carrier waves up-converted to a radio-frequency broadcast television channel. In receiver apparatus for the digital television broadcasting system the results of de-mapping QAM constellations recovered from demodulating the COFDM carrier waves are de-interleaved, and the LDPC constituent codes of the MLC are independently decoded in parallel with decoding results time-interleaved to recover the IP packets of digital television information.

In transmitter apparatus for a digital television broadcasting system, internet-protocol (IP) packets of digital television information are subjected to multilevel coding (MLC) before being Gray-mapped to quadrature-amplitude-modulation (QAM) constellations. The constituent codes of the MLC comprise respective low-density parity-check (LDPC) inner coding. Preferably, the LDPC inner coding is LDPC convolutional coding. The QAM constellations are used in coded orthogonal frequency-division modulation (COFDM) of plural carrier waves up-converted to a radio-frequency broadcast television channel. In receiver apparatus for the digital television broadcasting system the results of de-mapping QAM constellations recovered from demodulating the COFDM carrier waves are de-interleaved, and the LDPC constituent codes of the MLC are independently decoded in parallel with decoding results time-interleaved to recover the IP packets of digital television information.

A method of reducing transmission power for an encoded data stream includes the steps of receiving an incoming data stream having equal probability for a plurality of incoming data bits, assigning a symbol scheme to the received data bits of the incoming data stream according to probabilities of occurrence of individual ones of the received data bits, and transmitting an outgoing data stream according to the assigned symbol scheme having a second average transmit power, different than the first average transmit power, for a plurality of outgoing symbols.

A method of reducing transmission power for an encoded data stream includes the steps of receiving an incoming data stream having equal probability for a plurality of incoming data bits, assigning a symbol scheme to the received data bits of the incoming data stream according to probabilities of occurrence of individual ones of the received data bits, and transmitting an outgoing data stream according to the assigned symbol scheme having a second average transmit power, different than the first average transmit power, for a plurality of outgoing symbols.

Methods, systems, and apparatus described herein make a multi-level PAM signal (PAM-N signal) at a transmitter using CMOS-based components. By forming the PAM-N signal at the transmitter, receivers do not have to recombine and/or realign multiple signals and only employs a single transmission line channel (or two transmission line channels in differential implementations) to convey the data stream to the receiver from the transmitter.

Methods, systems, and apparatus described herein make a multi-level PAM signal (PAM-N signal) at a transmitter using CMOS-based components. By forming the PAM-N signal at the transmitter, receivers do not have to recombine and/or realign multiple signals and only employs a single transmission line channel (or two transmission line channels in differential implementations) to convey the data stream to the receiver from the transmitter.

Examples relating to techniques for wireless communications, e.g., visible light communication, VLC, are disclosed. In particular, there is disclosed a communication device for communicating with a plurality of other devices, using a wireless link. The device provides individual reference signals using a number of subcarriers or time slots in accordance to the optical clock reference and the number of transmitting devices in the set or streams to be transmitted in parallel. The device defines the position of subcarriers or of signals at the time slots in accordance to an identification number associated to an individual device within the whole set of transmitting devices or in dependence on an identification number identifying a specific stream or transmitter. The device transmits the reference signal which enables the plurality of receiving devices to identify the signal coming from the individual communication device in the whole set of devices.

A signal shaping device includes: a generation unit to perform plural types of predetermined processes on blocks obtained by dividing plural sequences of bit strings by a predetermined length, and generate a plurality of candidate blocks that are candidates for a shaped block to be transmitted; a calculation unit to calculate, on a candidate-block-by-candidate-block basis, a weight of a one-dimensional modulation symbol when a plurality of bits included in the candidate block are converted into the one-dimensional modulation symbol; a selection unit to select, from among the candidate blocks, the shaped block on a basis of the weight; an addition unit to add, to the shaped block, selection information indicating a selection result; and a symbol mapping unit to generate a one-dimensional modulation signal by converting a plurality of bits included in the shaped block, into the one-dimensional modulation symbol.

A signal shaping device includes: a generation unit to perform plural types of predetermined processes on blocks obtained by dividing plural sequences of bit strings by a predetermined length, and generate a plurality of candidate blocks that are candidates for a shaped block to be transmitted; a calculation unit to calculate, on a candidate-block-by-candidate-block basis, a weight of a one-dimensional modulation symbol when a plurality of bits included in the candidate block are converted into the one-dimensional modulation symbol; a selection unit to select, from among the candidate blocks, the shaped block on a basis of the weight; an addition unit to add, to the shaped block, selection information indicating a selection result; and a symbol mapping unit to generate a one-dimensional modulation signal by converting a plurality of bits included in the shaped block, into the one-dimensional modulation symbol.

A signal generator 10 generates an OOK (on-off keying) modulation signal by mapping a CAZAC (constant amplitude zero auto-correlation) sequence to N subcarriers (N being an integer that is greater than or equal to 2) arranged at a determined interval among M subcarriers (M being an integer that is greater than or equal to 3) that are adjacent in the frequency domain, carrying out inverse fast Fourier transform (IFFT) processing on the mapped CAZAC sequence, and carrying out Manchester coding on a time domain signal generated by the IFFT processing. A radio transmitter 107 transmits the OOK modulation signal.