The scope of the subclass H03M is so broad that a detailed description of the subject matter appropriate for this place is correctly possible only at the main-group level, e.g. H03M 7/00.

Provisions that are valid at a general level (e.g. of a kind appropriate to more than one of the main groups) are provided in the sections that follow.

The user is otherwise referred to the IPC definitions for the individual main groups of H03M which follow hereinafter. The following list is intended to assist the user.

Coding and decoding

Conversion

Others

See the application places listed below the subclass title.

The structural association with components such as transducers, sensors, gain stages or filters can be classified either in H03M 1/00 or in the subclass covering the component (or in both the subclasses), depending on which aspect is more relevant.

In particular A/D or D/A converters represented as "black boxes" in a specific application (e.g. a measuring or telecommunication system) are in general not classified in H03M.

Relations between H03M 1/00 and H03M 3/00

A/D and D/A converters using differential modulation are classified in H03M 3/00. According to the reference out following main group symbol H03M 1/00, for all A/D and D/A converters using differential modulation, e.g. delta modulation, DPCM and nowadays in particular delta-sigma modulation, main group H03M 3/00 has precedence over H03M 1/00. Note however, that inventions actually relating to "normal" converters which are used as components within such differential modulators are classified in H03M 1/00 again (because they can be more widely applied than only in the "differential" context). An example of the latter is dynamic element matching in D/A converters used in feedback paths of multi-bit delta-sigma A/D converters or in feedforward paths of multi-bit delta-sigma D/A converters, which is classified in group branch H03M 1/066.

Position or velocity encoders

In principle the classification in H03M 1/00 is directed to the coding aspects, whereas that in G01D or G01P is directed to the transducer aspects, but in practice they also appear to have subgroups directed to coding aspects.

Electro-optical A/D or D/A converters

In many cases inventors state to have invented an optical A/D or D/A converter though in fact only the sampling or signal conditioning is optical but the conversion itself is electronic. In principle both these cases and true electro-optical converters are classified in H03M while true optical converters are classified in G02F 7/00, but in practice many electro-optical converters appear to have been classified in G02F 7/00 as well.

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This group deals with the provision of special means for saving power, e.g. for allowing a sleep mode.

Thus the group should not be used for overall designs using less power than prior ones.

This group covers converters which are truly reconfigurable between A/D and D/A conversion as well as CODEC's having separate A/D and D/A converters with at least partially common control.

converters in which the conversion process as such has a stochastical nature or which convert the analogue or digital signal to a (possibly intermediate) signal in which the information content is represented by stochastic parameters.

It does not cover the use of dither or the random selection among identical elements for averaging out errors.

H03M 1/001 - H03M 1/10 take precedence

It is noted that some patent documents deal with converters stated by the inventor to be "parallel converters using n comparators for n bits" or similar but in which in fact the reference values of the second and further comparators are modified according to the outputs of one or more preceding comparators. Thus, in reality these converters are not parallel but asynchronous serial converters falling within the scope of H03M 1/42.

Multiple stage A/D converters in which the input signal is broadcasted to all stages while the reference value applied to each stage but the first one is modified by the output of one or more preceding stages.

Examples:

Multiple stage A/D converters in which the input signal is broadcasted to all stages while the reference value applied to each stage but the first one is modified by the output of one or more preceding stages.

A/D converters in which the output signal continuously tracks the input signal by means of reconversion of the output signal to an analogue feedback signal which is compared to the input signal.

The error signal usually adjusts the digital generator in one or the other direction, in dependence upon the sign of the error, in order to reach the correct position along the shortest route. However, occasionally the digital generator can be adjusted in one direction only; then it has to move circularly through nearly a full cycle in order to obtain a change in the other direction.

It is difficult sometimes to distinguish the latter systems from the range sweeping type (H03M 1/56) in which, however, the digital generator returns to a datum position between successive conversions.

The "successive approximation" type converters (H03M 1/46) are sometimes called "feedback converters" as well but are also reset between conversions.

Also, it is sometimes difficult to distinguish servo-type converters from A/D converters using differential modulation (H03M 3/00) which, however, deliver an output signal having a reduced number of bits at an oversampling rate, thus needing a decimation filter for converting it to a final result at full resolution and Nyquist rate. General analogue servo-systems using only digital feedback, for example as shown in the following block diagram, do, strictly spoken, not fall within the definition of an A/D conversion system.

However, they are very similar to an A/D conversion system using a D/A converter in a feedback arrangement (output Y instead of X) and therefore these systems are classified in H03M 1/48 unless the converters are merely shown as black boxes.

H03M 1/001 - H03M 1/10 take precedence

D/A converters in which the output signal continuously tracks the input signal by means of reconversion of the output signal to an digital feedback signal which is compared to the input signal.

The error signal usually adjusts the analogue generator in one or the other direction, in dependence upon the sign of the error, in order to reach the correct position along the shortest route. However, occasionally the analogue generator can be adjusted in one direction only; then it has to move circularly through nearly a full cycle in order to obtain a change in the other direction. It is difficult sometimes to distinguish the latter systems from the range sweeping type (H03M 1/82) in which, however, the analogue generator returns to a datum position between successive conversions.

Networks comprising impedances in series as well as parallel branches.

The structural association with components such as transducers, sensors, gain stages or filters can be classified either in H03M 3/00 or in the subclass covering the component (or in both the subclasses), depending on which aspect is more relevant.

In particular differential modulators represented as "black boxes" in a specific application (e.g. a measuring or telecommunication system) are in general not classified in H03M.

Conversion of codes where one aspect is the representation of the code as a signal, e.g. a code embodied by pulses or other shapes (e.g. sinusoidal). Examples are modulation codes (like Manchester coding).

In groups H03M 5/02 - H03M 5/22, in the absence of an indication to the contrary, an invention is classified in the last appropriate place.

Classification of additional information:

A sequence of numerical or textual symbols representing a code and transformations/conversions thereof into a different sequence of numbers or textual symbols. It comprises in particular code conversions resulting in shorter codes (data compression and decompression).

The sequence of textual symbols could be part of a structured text document, for example an XML document.

Also covered are devices which provide for such code conversion, e.g. hardware implemented code converters and code converters based on logic circuit and programmable converters.

Furthermore, data reduction methods in order to get a short representation of a signal or of digital data in general are also covered. An example would be methods for reducing the number of necessary samples in data acquisition.

Relations between H03M 7/46 and H03M 5/145:

Relations between H03M 7/30 and H04N 19/00:

Use of data compression bandwidth reduction for in video coding (H04N 19/00) when the data compression is merely represented as a "black box" are not in the scope of H03M 7/30. However, if a certain data compression scheme for video bandwidth reduction is detailed and goes beyond conventional compression algorithms, this new aspect can be classified in H03M 7/30. An example is the use of arithmetic coding in video coding (e.g. CABAC) where specific aspects should be classified under H03M 7/30.

In general, data compression schemes merely represented as "black boxes" in a certain application field should not be classified under H03M 7/00.

Classification of additional information:

Further information:

H03M 7/26

This subgroup deals solely with data compression and is not to be used for run-length-limited modulation techniques.

H03M 7/30

This group branch in general deals with all types of data compression unless the data compression is specified merely as a "black box". It also deals with precoding before the actual compression stage in order to get better compression results (e.g. Burrows-Wheeler transform).

H03M 7/3002

This group branch deals with digital differential modulation, e.g. delta modulation [DM], differential pulse code modulation [DPCM], delta-sigma modulation.

This subgroup deals solely with data compression and is not to be used for run-length-limited modulation techniques.

all types of data compression unless the data compression is specified merely as a "black box". It also deals with precoding before the actual compression stage in order to get better compression results, e.g. Burrows-Wheeler transform.

Parallel/series conversion or vice-versa, in general;

Timing and synchronisation aspects thereof.

Encoding, decoding, coding or decoding schemes for the correction or detection of errors, i.e. error control coding (ECC) or forward error correction (FEC)

Coded modulation for error detection or correction.

Combination of error correction coding and techniques for the efficient use of the spectrum, e.g. modulation codes with error correction properties

Synchronisation by means of error correction codes

H03M 13/00 has relationships with a plurality of different other technical areas, wherein the relationships are characterised in that the other technical areas relate to applications and frameworks to which the H03M 13/00 specific techniques are applied.

Techniques for error control coding and forward error correction, which are characterised by their intrinsic nature, which is independent of its field of use, are to be classified in H03M 13/00. This makes H03M 13/00 a function-oriented place.

The application of techniques for error control coding or forward error correction in the sense that a function is plugged into an application without modification of the intrinsic properties of the function itself is only to classified in the respective application place (e.g. the use of a CRC check to determine whether data read from a memory is error free, the use of Reed-Solomon codes on a recording medium, the use of LDPC coded modulation in a transmitter arrangement).

If the application requires an adaptation of the techniques for error control coding or forward error correction to a particular application place, which involves a modification of the intrinsic properties of the function as well, then the classification in the function-oriented place and the application place is obligatory (e.g. the use of a CRC in a memory wherein the CRC calculation is parallelized in order to increase the read speed; this modification involves an intrinsic property of the CRC calculation; e.g. the design of an LDPC code having particular distance properties for a LDPC coded modulation scheme in a transmitter arrangement).

The application places that have relationships with H03M 13/00 are as follows:

The invention as such as well as additional information shall be classified

H03M 13/61 - H03M 13/65 are used to introduce a so-called 2nd dimension to the classification and are, thus, always to be used in combination with one of the subgroups of the range H03M 13/00-H03M 13/45 or the corresponding Indexing Codes

Component or constituent codes within a particular scheme are to be classified by means of the appropriate Indexing Codes; for instance, a product code built from a Reed-Muller code and a BCH code should be classified using H03M 13/2909 (product code) and H03M 13/136 and H03M 13/152 to indicate its component codes

For the search in main group H03M 13/00 it is noted that additional information has been classified in this group from 01-04-2004 onwards.

Further information:

It follows a brief explanation of those CPC subgroups, where it might not be clear from the wording alone what technical features are meant to fall within their scope:

H03M 13/6362

H03M 13/033

H03M 13/091

H03M 13/093

H03M 13/1114

H03M 13/1131

H03M 13/155

H03M 13/1555

H03M 13/1565

H03M 13/157

H03M 13/1575

H03M 13/158

Methods and arrangements for finite field processing when applied in an encoder or decoder for error correcting codes, e.g. a finite field multiplier.

If the finite field processing is not disclosed in the context of error control coding, then this class is not to be given.

Methods and arrangements for finite field arithmetic are always to be circulated to G06F 7/72.

H03M 13/25

Coded modulation.

The subgroups H03M 13/251 - H03M 13/258 provide details as to the type of code that is used.

The type of code can be further refined by using the appropriate Indexing Code or ECLA subgroup; e.g. coded modulation with a Reed-Muller code would be classified using H03M 13/251 (coded modulation with block coding) and H03M 13/136 (Reed-Muller codes).

H03M 13/27

For a complete classification of a document concerning interleaving, it may be required to allocate more than one subgroup of H03M 13/27 to the document.

H03M 13/2703 - H03M 13/2757 relate to different types of interleavers, whereas H03M 13/2771 - H03M 13/2796 relate to characteristics other than the type of interleaving.

Hence, a document relating to interleaving should usually have a designation of the type of interleaving (H03M 13/2703 - H03M 13/2757) and optionally one or more classes relating to the other characteristics (H03M 13/2771 - H03M 13/2796).

H03M 13/2771 indicates that the document deals with interleavers/interleaving for turbo codes (so-called turbo code internal interleavers).

H03M 13/2728

This subgroup covers the principle underlying a helical type interleaver for 1-bit dummy codes

H03M 13/276

This subgroup covers the actual calculation of interleaving addresses.

Note that the principle underlying a particular interleaving type may be described without actually providing details about how the address or index calculation is performed or implemented.

If a document does not only relate to a particular type of interleaver but provides in addition details about the calculation of interleaver addresses or indices, then this class should be given in addition.

H03M 13/2764

Circuits/hardware implementations for the calculation of interleaver addresses or indices.

See also the comments w.r.t. H03M 13/276.

H03M 13/2912

Product codes in which the sub-block comprising the checks-on-checks or parity-on-parity is not present (as it is either not generated or removed).

H03M 13/2927

Turbo decoding of concatenated block codes is to be classified in H03M 13/2963.

If the decoding strategy involves iterative decoding different from turbo decoding, e.g. sub-sequent decoding of rows and columns of a product code, then this feature (iterative decoding) is to be classified using H03M 13/2948.

H03M 13/2939

Coding schemes including any concatenation of two or more convolutional codes, wherein decoding is not based on the turbo principle, e.g. serial concatenation of convolutional codes without turbo decoding.

H03M 13/2948

If the decoding strategy involves iterative decoding different from turbo decoding, e.g. decoding without exchange of extrinsic soft-decision information between decoders, then this feature (iterative decoding) is to be classified using H03M 13/2948.

H03M 13/2957

Note that H03M 13/2957 is also to be allocated when a component code is replaced by a non-coded constraint, e.g. turbo equalisation (cf. also the Glossary of terms and the comments on H03M 13/63).

H03M 13/333

Feedback from the channel decoder to a synchronisation unit is used to establish synchronisation with respect to a frame or block of bits.

H03M 13/336

Phase recovery in combination with channel decoding, wherein feedback from the channel decoder to phase estimation is used to achieve or improve the recovery/estimation of the symbol phase.

H03M 13/3707

Decoding methods or techniques providing more than one decoding algorithm for one code and selection of the appropriate decoding method or technique

Adaptive decoding in which decoding is adapted to some extrinsic or intrinsic parameter, e.g. setting of internal thresholds.

H03M 13/3715

The extrinsic or intrinsic parameter is the number of estimated errors or information about the state of the channel (e.g. SNR).

H03M 13/3723

Initialisation is meant to denote the configuration of the decoder (e.g. setting of internal variables) prior to decoding.

Initialisation of MAP decoders for turbo decoding using the result of the previous iteration; initialisation of variable nodes for LDPC code decoding; initialisation of state probabilities for a tail-biting MAP decoder.

H03M 13/3776

Note that re-encoding is often performed to estimate error rates but is not integral to decoding as such.

H03M 13/3994

For trellis decoding, some bits may be known (e.g. during decoding of concatenated codes, padding bits) to the decoder, which exploits this information as a priori information.

The trellis decoder is forced to take the a priori known decision, for instance, by adding to the ACS circuit a decision-overriding logic or by saturating state or branch metrics.

This technique is sometimes referred to by state pinning or decision forcing or trellis pruning.

H03M 13/451

For decoding, the optimum code word (in terms of a metric) is searched in a set of possible code words

The set of possible code words is often denoted by candidate code words

H03M 13/456

This subgroup includes maximum likelihood or MAP decoding, wherein a list of all code words of the code or its dual code is processed.

H03M 13/458

SISO decoding of block codes with updating of hard decisions of most reliable symbols using extrinsic information from least reliable symbols.

H03M 13/613

Use of properties of the code to be encoded or decoded that relate to its dual code.

This includes, for instance, decoding using the trellis of the dual code instead of that of the code itself.

H03M 13/63 and its subgroups:

These subgroups are intended to cover the combination of error control coding and other techniques.

These subgroups are in particular important when the so-called turbo principle is applied to e.g. demodulation (turbo demodulation) or equalisation (turbo equalisation); then, H03M 13/2957 is to be used to indicate the use of the turbo principle and H03M 13/6325 and H03M 13/6331, respectively, are used to indicate the non-coded constraint.

H03M 13/65 and its subgroups:

Methods and arrangements for finite field processing when applied in an encoder or decoder for error correcting codes, e.g. a finite field multiplier.

If the finite field processing is not disclosed in the context of error control coding, then this group is not to be given.