A method and an apparatus for measuring a displacement of an object according to steps of: dividing a signal into an I signal and a Q signal according to a phase of the signal, wherein the signal is reflected by the object after a transmission signal having a plurality of frequencies is emitted toward the object by the radar measurement system; estimating a direct current (DC) component from an N-tuple information acquired from the I signal and the Q signal; removing the estimated DC component to correct the I signal and the Q signal; and measuring the displacement of the object based on the corrected I signal and Q signal are provided.

Embodiments of this application provide a coding and modulation method, a demodulation and decoding method, an apparatus, and a device. The coding and modulation method includes obtaining K to-be-encoded bits and a modulation scheme, and coding the K to-be-encoded bits, based on M bit levels of the modulation scheme, to obtain M code blocks, where M<M, a code length of an i.sup.th code block is N.sub.i, N.sub.i=M.sub.i*N, M.sub.i is a quantity of bit levels corresponding to the i.sup.th code block, N is a symbol block length, and 1?i?M. The disclosed method further includes modulating the M code blocks, according to a mapping relationship between the M code blocks and the M bit levels, to obtain and output a modulated symbol sequence, where a code block whose code length is M.sub.i*N corresponds to M.sub.i bit levels in the mapping relationship.

We disclose a transmitter that uses at least first and second fixed constellations in which the same bit-words are assigned to different respective constellation symbols of different respective transmit energies. The transmitter generates an outgoing data frame by first generating two data frames using the first and second constellations, respectively, and then selecting the one of the two data frames that has the lower overall transmit energy and discarding the other. The first and second constellations are constructed in a manner that enables the transmitter to realize a significant shaping gain. Some embodiments of the transmitter are compatible with the use of forward-error-correction coding and provide a shaping gain for the transmission of both information and parity bits. An example embodiment of the transmitter can advantageously be implemented with relatively low complexity by employing constellation mappers and demappers that operate using relatively small look-up tables.

Transmitter apparatus to broadcast coded orthogonal frequency-division multiplexed (COFDM) radio-frequency carriers conveying low-density parity-check (LPDC) coding transmits the same coded DTV signals twice some time apart. The coded DTV signals of initial transmissions and of final transmissions are mapped to quadrature amplitude modulation (QAM) of the COFDM carriers according to first and second patterns, respectively. Bits that map to lattice points in the first mapping pattern more likely to experience error are mapped to lattice points in the second mapping pattern less likely to experience error. Bits that map to lattice points in the second mapping pattern more likely to experience error are mapped to lattice points in the first mapping pattern less likely to experience error. Receiver apparatus demaps QAM symbols in the earlier and later transmissions of twice-transmitted COFDM signals and maximal-ratio combines the de-mapping results at bit level, rather than symbol level.

A BASE-T Ethernet transceiver is disclosed. The transceiver includes a BASE-T Ethernet data framing module having an input interface to receive Ethernet block data bits at a first data rate, logic to associate the Ethernet block data bits with an auxiliary bit and a number of Reed-Solomon check bytes, and a forward error correction encoder. The encoder is coupled to the logic to encode all of the data bits, auxiliary bit and the Reed-Solomon check bytes into a first error encoded transport frame having plural error check bits. A symbol mapper receives the first error encoded transport frame and modulates the first error encoded transport frame into symbols, each of the symbols having uncoded bits. A BASE-T transmitter is coupled to the symbol mapper to transmit the first group of symbols over an Ethernet link at one of a selection of symbol rates. Errors in the uncoded bits are correctable via the Reed-Solomon check bytes.

An optical transmitter device includes a digital signal processor (DSP) having digital hardware. The DSP is operative to generate shaped bits from a first set of information bits, and to apply a systematic forward error correction (FEC) scheme to encode the shaped bits and a second set of information bits, where the first set of information bits and the second set of information bits are disjoint sets. Unshaped bits and the shaped bits are mapped to selected symbols or are used to select symbols from one or more constellations. The selected symbols are mapped to physical dimensions. Each unshaped bit is either one of the second set of information bits or one of multiple parity bits resulting from the FEC encoding. In this manner, a target spectral efficiency is achieved.