Methods and apparatus for efficient demapping of constellations are described. In an embodiment, these methods may be implemented within a digital communications receiver, such as a Digital Terrestrial Television receiver. The method reduces the number of distance metric calculations which are required to calculate soft information in the demapper by locating the closest constellation point to the received symbol. This closest constellation point is identified based on a comparison of distance metrics which are calculated parallel to either the I- or Q-axis. The number of distance metric calculations may be reduced still further by identifying a local minimum constellation point for each bit in the received symbol and these constellation points are identified using a similar method to the closest constellation point. Where the system uses rotated constellations, the received symbol may be unrotated before any constellation points are identified.

To provide signal generating apparatus that is capable of controlling the DC bias of the optical modulator applicable to various kinds of modulation format, a signal processing apparatus includes a digital processing unit for deserializing an input digital data into parallel data lanes, for comparing the value of the digital data of symbol rate F to at least one predetermined threshold value, for selecting an offset value based on the result of the comparison; and for adding the selected offset value to the digital data, a converting unit for converting the digital data added the offset value to analog signals in each lane; an optical modulating unit for modulating a lightwave according to the analog signals with predetermined modulation format at the symbol rate F, where the modulated signal contains a frequency component at F/N.

To provide signal generating apparatus that is capable of controlling the DC bias of the optical modulator applicable to various kinds of modulation format, a signal processing apparatus includes a digital processing unit for deserializing an input digital data into parallel data lanes, for comparing the value of the digital data of symbol rate F to at least one predetermined threshold value, for selecting an offset value based on the result of the comparison; and for adding the selected offset value to the digital data, a converting unit for converting the digital data added the offset value to analog signals in each lane; an optical modulating unit for modulating a lightwave according to the analog signals with predetermined modulation format at the symbol rate F, where the modulated signal contains a frequency component at F/N.

Methods, systems, and devices are described for mitigating an unwanted increase in a coding rate of a wireless communication signal. A plurality of symbols including a transmitted codeword is received. The plurality of symbols including a first group of data symbols with a first modulation and coding scheme and a second group of data modulated pilot symbols with a second modulation and coding scheme. Applicable demodulation schemes are adaptively switched for each group of the plurality of symbols. The second group of data modulated pilot symbols are used in lieu of pilot symbols. The second modulation and coding scheme is a more reliable modulation and coding scheme than the first modulation and coding scheme.

Apparatus and methods for multi-antenna communications are provided. In certain embodiments, a communication system includes an antenna array including a plurality of antenna elements, and a plurality of RF circuit channels each coupled to a corresponding one of the antenna elements. The plurality of RF circuit channels generate two or more analog baseband signals in response to the antenna array receiving a radio wave. The communication system further includes a controllable amplification and combining circuit that generates two or more amplified analog baseband signals based on amplifying each of the two or more analog baseband signals with a separately controllable gain, and that combines the two or more amplified analog baseband signals to generate a combined analog baseband signal.

Apparatus and methods for multi-antenna communications are provided. In certain embodiments, a communication system includes an antenna array including a plurality of antenna elements, and a plurality of RF circuit channels each coupled to a corresponding one of the antenna elements. The plurality of RF circuit channels generate two or more analog baseband signals in response to the antenna array receiving a radio wave. The communication system further includes a controllable amplification and combining circuit that generates two or more amplified analog baseband signals based on amplifying each of the two or more analog baseband signals with a separately controllable gain, and that combines the two or more amplified analog baseband signals to generate a combined analog baseband signal.

A technique for de-mapping a point in a constellation diagram into a bit sequence is presented. The de-mapping provides for each bit of the bit sequence an output value with a sign of the output value indicating a bit value and a magnitude of the output value indicating probability information in the form of a distance to a decision boundary in the constellation diagram. A method aspect of the technique presented herein comprises receiving a signal indicative of a constellation point, wherein the constellation point represents a bit sequence having a most significant bit and at least one next significant bit, deriving a first output value for the most significant bit based on a first decision boundary, receiving a priori information, and deriving a second output value for the next significant bit based on the first output value, the a priori information and a second decision boundary.

A simplified but accurate soft-symbol determination process represents one of the advantages provided by the example embodiments disclosed herein. In this regard, a mapping function “maps” symbol estimates to corresponding soft symbol values, which may be used in interference mitigation, joint detection processing, etc. Whether the mapping function is implemented on-the-fly as a live calculation or is embodied in a look-up table, it advantageously operates on the symbol estimates directly, rather than requiring the derivation of corresponding soft bit values or the like, and it maps each symbol estimate to its “expected value,” i.e., the weighted sum of constellation point probabilities. Moreover, the mapping function may be changed dynamically—e.g., by using different look-up tables—to account for changing reception conditions and/or different modulation schemes or other signal parameters associated with the symbols being estimated and mapped to soft symbol values.

In a PAM-N receiver, sampler reference levels, DC offset and AFE gain may be jointly adapted to achieve optimal or near-optimal boundaries for the symbol decisions of the PAM-N signal. For reference level adaptation, the hamming distances between two consecutive data samples and their in-between edge sample are evaluated. Reference levels for symbol decisions are adjusted accordingly such that on a data transition, an edge sample has on average, equal hamming distance to its adjacent data samples. DC offset may be compensated to ensure detectable data transitions for reference level adaptation. AFE gains may be jointly adapted with sampler reference levels such that the difference between a reference level and a pre-determined target voltage is minimized

A signal processing device includes: an extraction section configured to extract a signal having a predetermined component from an obtained signal; and a detection section configured to determine a timing of decoding when a modulation part lasting for a first time period and a non-modulation part lasting for a second time period are detected from the signal extracted by the extraction section.