Patent Description:
Error free data communications with minimum transmit power has always been and still is an important aspect in communications. It is desired to achieve the Shannon capacity, which is well-known to be the upper bound of bit rate per Hertz of transmit bandwidth for a given signal to noise ratio. The assumptions of Shannon capacity are rather theoretical, however other capacity measures such as bit-interleaved-coded-modulation (BICM) capacity exist which impose a more practical upper bound on bit rate per Hertz.

The BICM capacity is a function of the channel noise model (e.g. AWGN; Additive White Gaussian Noise) and its properties (e.g. probability density function, variance), the signal points (e.g. QAM) and their position within the complex plane (e.g. rectangular <NUM>-QAM), and the probability of occurrence of signal points.

Optimization of BICM capacity is desired to maximize link throughput over a given transmit bandwidth and signal to noise ratio. It can be either achieved by signal point optimization (e.g. non-uniform constellation NUC), by probability optimization, or both.

Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.

Known probabilistic signal point shaping devices and methods are described in the following documents:.

It is an object to provide a probabilistic signal point shaping device and method that optimize BICM capacity. It is a further object to provide a corresponding computer program for implementing said method.

According to aspects of the present invention there are provided a probabilistic signal point shaping device and a computer-implemented probabilistic signal point shaping method as defined in the claims.

According to still further aspects a computer program comprising program means for causing a computer to carry out the steps of the method disclosed herein, when said computer program is carried out on a computer.

It shall be understood that the disclosed method and the disclosed computer program have similar and/or identical further embodiments as the claimed device and as defined in the dependent claims and/or disclosed herein.

One of the aspects of the disclosure is to provide various enhancements to probabilistic amplitude shaping (PAS), which will be called probabilistic signal point shaping since not only amplitudes (real values of a complex plane, also known as signal point constellation) are shaped, but generally (real-valued or complex-valued) signal points of a signal point constellation. One of the ideas of these enhancements to PAS is to generate a signal point constellation in which the probability of occurrence of the signal points (represented by the output symbols) is non-uniform. It has been shown that this approach comes close to the upper bound of channel capacity measures. In this disclosure further enhancements of the PAS scheme are presented. In particular, simultaneous IQ distribution matching is disclosed, which allows use of signal point constellations combining odd numbers of bits and allows bandwidth efficient communications for channels other than AWGN.

The foregoing paragraphs have been provided byway of general introduction, and are not intended to limit the scope of the following claims.

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, <FIG> shows a schematic diagram of a first embodiment of a probabilistic signal point shaping device <NUM> according to the present disclosure. This device applies a transmission scheme which optimizes the probability of occurrence of signal points. The bit stream to be transmitted is DK with length K. A constant composition distribution matcher (CCDM) <NUM> generates n mapping symbols A<NUM>,. , An each being assigned to (or represented by) a particular signal point. A CCDM as such is e.g. known from <NPL>.

Different from the known CCDM, according to the present disclosure the mapping symbols (generally represented by signal points) are non-uniformly spaced, i.e. the distances between each pair of two neighboring signal points are not equal, if the mapping symbols are real-valued and are represented by amplitude levels. These amplitude levels are non-uniformly spaced as shown in <FIG>. Here, four different amplitude levels L<NUM>,. , L<NUM> are shown, where amplitude level L<NUM> = <NUM>, L<NUM> = <NUM>, L<NUM> = <NUM>, L<NUM> = <NUM>, i.e. the distance between amplitude levels L<NUM> and L<NUM> is larger than the difference between L<NUM> and L<NUM> and between L<NUM> and L<NUM>. The mapping symbols A<NUM>,. , An are non-uniformly distributed onto these four different amplitude level L<NUM>,. , L<NUM> according to a predetermined probability distribution as also indicated in <FIG>.

In other words, the amplitude levels L<NUM>,. , L<NUM> determine a kind of "alphabet" of the CCDM source, whereas the mapping symbols A<NUM>,. , An are different realizations from that CCDM source. When analyzing the mapping symbols, each amplitude level features a certain predetermined probability of occurrence.

Generally, the CCDM <NUM> (or general circuitry, such as a processor or other hardware) thus maps data blocks of input bits of the input bit stream DK onto mapping symbols A<NUM>,. , An, wherein said mapping symbols are taken from non-uniformly spaced signal points, in the example shown in <FIG> represented by amplitude levels, according to a predetermined probability distribution.

The probability of occurrence of these amplitude levels approximate a predefined probability distribution (which shall be optimized). The mapping of the data blocks of the input bit stream DK to signal points is invertible, i.e. the receiver recovers bits from signal points (e.g. amplitude levels) loss less. Each signal point gets assigned a bit combination (also called bit label) by the bit label assigner <NUM> (block b(. ) in <FIG>) or a corresponding circuitry. Thus, the number N of different amplitude level L<NUM>,. , LN corresponds to an integer power of <NUM>. For instance, as shown in <FIG>, four different amplitude levels are used, to which the bit labels <NUM> (to L<NUM>), <NUM> (to L<NUM>), <NUM> (to L<NUM>), and <NUM> (to L<NUM>) are assigned. Hence, depending on the amplitude level, to which a mapping symbol is assigned, a corresponding bit label is assigned to the respective mapping symbol. For instance, since the bit label <NUM> is assigned to amplitude level L<NUM>, the bit label <NUM> is finally assigned to the mapping symbols A<NUM> and A<NUM>. The assigned bit labels are generally referred to as b(A<NUM>),.

The bits generated by the bit label assigner <NUM> are passed to a redundancy generator <NUM> using a parity matrix P which originates from a systematic forward error correction (FEC) code of a given rate. The redundancy generator <NUM> uses the P matrix to generate, based on it input bits b(A<NUM>),. , b(An) (i.e. the bits of the bit labels), redundancy bits, in this embodiment parity bits b(S<NUM>),. , b(Sn), at its output. Hereby, the P matrix preferably originates from a FEC code with code rate <MAT> with m - <NUM> being the number of bits assigned to each mapping symbol.

The parity bits b(S<NUM>),. , b(Sn) are transformed into a redundancy rule by a transforming unit <NUM> (block b-<NUM>(. ) in <FIG>) or a corresponding circuitry. The redundancy rule in this embodiment is a multiplication factor S<NUM>,. , Sn of +<NUM> or -<NUM>, i.e. a sign function, but other ways to implement the redundancy rule are well possible, such as a mirroring operation.

The multiplication factor S<NUM>,. , Snis multiplied in a multiplier <NUM> or a corresponding circuitry with the mapping symbols A<NUM>,. , An output from the constant-composition distribution matcher <NUM> (CCDM) to generate output symbols X<NUM>,. In other words, the parity bits influence the sign of the mapping symbols A<NUM>,.

As a last optional step, multiplication with a scaling factor Δ in scaling unit <NUM> or a corresponding circuitry rescales output symbols X<NUM>,. , Xn such that desired (e.g. unity) transmit power is achieved. With this optional step the communication rated can be increased considerably.

The CCDM algorithm which is described in the above cited paper of Schulte and Böcherer has three inputs, i.e. bits to be transmitted, desired output symbols and desired probability of occurrence of the output symbols. It generates based on input parameters an output symbol sequence which fulfills the desired probability of occurrence. If output symbols are complex-valued or non-uniform, it will output complex-valued or non-uniform symbols. The operation itself is unchanged compared to the operation described in this paper.

The CCDM as described in this paper may thus be applied as described in this paper, i.e. it outputs real valued and uniform amplitude levels, and a mapping unit may then be attached. This mapping unit performs an invertible one-to-one mapping between real-valued, uniform amplitude levels and complex-valued signal points or non-uniform amplitude levels. For instance, the CCDM alphabet (the amplitude levels) may be <NUM>, <NUM>, <NUM>, <NUM> and a mapping unit allocates <NUM> to <NUM>, <NUM> to <NUM>+j, <NUM> to <NUM> and <NUM> to <NUM>+j. This implements a CCDM with complex-valued output symbols.

The CCDM thus basically works by dividing the [<NUM>, <NUM>] intervals into equal length sub-intervals each assigned to one of the constant composition output sequence. Afterwards, equally spaced points positioned on the [<NUM>, <NUM>] intervals are each assigned to the input binary sequences. During the distribution matching process, the CCDM will admit an input binary sequence, find its assigned points, find on which sub-intervals the point lies and finally output a constant composition sequence which is assigned to such sub-interval.

<FIG> shows a schematic diagram of a second embodiment of a probabilistic signal point shaping device <NUM> according to the present disclosure. This embodiment enables the use of the P matrix from the FEC with different code rates, i.e. code rate different from <MAT>. In this extended scheme, the length of the bypassed data bit kby of another (bypass) input bit stream DKby, preferably from the same source, can be matched to the rate of FEC code.

Basically, the additional input bits are appended to the parity generated by the redundancy generator <NUM>. Then, these extended bit sequences are mapped to signs by the transforming unit <NUM>. Care is taken during the design phase to ensure that the length of this extended sequence is equal to the CCDM output. The number of amplitudes preferably matches the number of signs, which imposes restrictions to the code. The idea of additional input bits is to overcome these restrictions. Thus, if the parity matrix is from a code with higher code rate than <MAT>, additional bits are used (where <NUM>m-<NUM> is the number of amplitudes or equivalently m-<NUM> is the number of bits assigned to each mapping symbol).

As an example a P matrix from a code with code rate <NUM>/<NUM> (i.e. no bypass bits needed for two amplitude levels, i.e. the embodiment shown in <FIG> may be applied) it shall be assumed that <NUM> mapping symbols are output from a source featuring two different amplitude levels (e.g. <NUM> and <NUM>). The bit label assigner <NUM> allocates one bit for each amplitude level (e.g. for amplitude level <NUM> bit label <NUM> is assigned and for amplitude level <NUM> bit label <NUM> is assigned). The redundancy generator <NUM> generates for each input bit one output bit and the transforming unit <NUM> does bit to sign mapping (e.g. bit <NUM> is transformed into sign -<NUM> and bit <NUM> is transformed into sign +<NUM>). The number of mapping symbols (<NUM>) matches the number of signs (<NUM>).

As another example a P matrix from a code with rate <NUM>/<NUM> (i.e. bypass needed for two amplitude levels, i.e. the embodiment shown in <FIG> may be applied) shall be considered. The operation is as described above but has a difference at the redundancy generator <NUM> which generates one output bit for two input bits. In order to match sign output to amplitude levels bypass bits are used. Assuming x bits are from the input bit stream DK and y bits are from the bypass bit stream DKby, both are concatenated before the redundancy generation, i.e. x + y bits are input into the redundancy generator <NUM>. After the redundancy generator <NUM> x/<NUM>+y/<NUM> +y bits are given (+y comes from concatenation with bypass bits). As the number of bits after the redundancy generator <NUM> shall match the number of amplitude levels, a condition for x and y can be given by <MAT> which results in 3y = x. The actual value of x and y depends on the block length of the P matrix such that the number of data bit in the parity matrix is equal to x + y. This constraint induces a system of linear equations that can be used to find a specific integer x and y which is matched to the property of the parity matrix P.

In the above described exemplary embodiments non-uniformly spaced amplitude levels are applied for the CCDM output, i.e. at least one distance between two neighboring signal points is different from all other distances between neighboring signal points. If the PAS scheme explained above is applied component-wise, e.g. I and Q component independently, the constellation seen on the channel is of non-uniform type.

For channels other than AWGN or for constellation sizes <NUM>X with X being an odd number, the separation of a 2D constellation into two 1D constellations is either not optimal (i.e. it does not achieve optimum channel capacity) or it is not possible (i.e. each 1D constellation projection would comprise a number of signal points which is different from a power of two). For those cases, more flexibility with respect to signal point position and probability of occurrence of signal points is beneficial.

Thus, it is proposed in further embodiments that the CCDM output defines complex-valued signal points, each associated with a probability of occurrence, i.e. the CCDM maps the data blocks of input bits of the input bit stream onto complex-valued mapping symbols, wherein said complex-valued mapping symbols are uniformly or non-uniformly spaced and represented by complex-valued signal points of a signal point constellation. At least one signal point is required to have a distance to its closest neighbor which is different from all other signal point distances to closest neighbors. The complex-valued signal points reside within a defined interval in the complex plane. The encoding scheme is equivalent up to the transforming unit <NUM> (the b-<NUM>(·) device), i.e. the layout of the embodiments shown in <FIG> and <FIG> also holds for these embodiments. For the proposed scheme to work, the transforming unit <NUM> allocates to an input bit combination an interval of the complex plane. This interval defines the actual location of the associated complex valued signal point generated by the CCDM <NUM>.

For the mapping onto complex-valued symbols sequences are first created in which the proportions of each symbol in the sequence satisfy the probability distribution. Then arithmetic coding scheme is used to map uniform bit input to these sequences.

Various implementations of the aforementioned procedure are conceivable.

a) In a first implementation, the CCDM <NUM> defines complex-valued signal points within a quadrant, i.e. Re><NUM> and Im ><NUM>. The transforming unit <NUM> considers a group of two of its input bits and assigns a quadrant to the signal points defined by CCDM <NUM>. An exemplary mapping table is shown in Table <NUM>.

The transforming unit <NUM> thus transforms said redundancy bits into a phase rotation function and/or an amplitude multiplication function as redundancy rule, in this implementation a phase rotation function for rotation by <NUM>°, <NUM>°, <NUM>° or <NUM>°. b) In another implementation, the CCDM <NUM> defines complex-valued signal points within an octant, i.e. all signal points reside in <MAT> where arg(·) gives the angular orientation of a complex number in the complex plane in radians. The transforming unit <NUM> considers a group of three of its input bits and interprets this number as an integerp ranging from <NUM> to <NUM>. The phase rotation applied to each output signal point of the CCDM is exemplarily given by <MAT>. c) In still another implementation, the CCDM <NUM> defines real-valued signal points, i.e. all signal points reside on the real axis. The transforming unit <NUM> considers a group of its input bits and interprets this number as a phase rotation as in implementation b). An exemplary phase rotation is given by <MAT> with integer p ranging from <NUM> to <NUM>. The constellation has a regular geometry in a magnitude-phase or polar diagram, whereas it is star-shaped (or has concentric circles) in a Cartesian diagram.

Any complex-valued signal points can be represented in a magnitude-phase/ polar or a Cartesian diagram. The relation between both representations is as shown below: The magnitude of a signal point x is defined as follows: <MAT> which can be interpreted to be the distance from the origin of the constellation or IQ diagram to signal point x.

The phase of a signal point x is defined by <MAT> where it is assumed that tan-<NUM>[x] saturates at <MAT> for x → ∞ and <MAT> for x → -∞, respectively.

Any complex signal point x has a Cartesian (IQ) and a polar representation which is equivalent: <MAT> <MAT>.

It can been shown that certain constellations which maximize the BICM shaping gain by varying signal point location under the assumption of equal probability of occurrence are also suitable for any PAS scheme, where the probability of occurrence of signal points can be different.

<FIG> shows a non-uniform constellation generated by the implementation example a). <FIG> the probability of occurrence for each signal point showing that, in this example, inner signal points are more frequently transmitted than outer signal points.

The above described embodiments enable the disclosed probabilistic signal point shaping scheme to support a non-uniform constellation which achieves higher capacity in channels other than AWGN and further enable mapping of non-separable constellations, i.e. where the number of signal points is <NUM>X with X being odd (e.g. <NUM>-QAM).

The above described scheme can be extended to a multi-user (MU) scenario. This scenario arises for example when a WLAN Access Point communicates with more than one user. Each user might have different path loss. It is theoretically known that it is possible to achieve higher communication rate if it is communicated with those users at the same time, although no practical method is offered in theory.

Another proposed embodiment is based on staged encoding. On each stage, more messages are added to the candidate transmission sequence. Without loss of generality, this will be illustrated by an example of having two users. Communication at the same time between users is achieved by providing joint constellation based on superposition for both users. Each user gets assigned specific bit label positions depending on the capacity considering their respective path loss. The generation of the final transmission sequence by the device is performed in two stages and one combining stage as will be explained below. <FIG> shows a schematic diagram of an embodiment of a mapping device <NUM> according to the present disclosure for use in a multi-user scenario.

Generally, on a first stage, the message for a user with higher path loss is encoded by a first distribution matcher (CCDM) with a predefined probability of occurrence P(A). On the second stage, the encoder takes into account the result of the first stage encoding as well as the already generated output symbols and changes the probability of occurrence of its amplitude levels for the transmitted sequence accordingly. In the combining stage, both amplitudes are linearly combined, i.e. by means of addition and multiplication. The stage concept can be generalized for the scenario with U users. In this case, the mapping symbols are encoded in U stages and combined in one combining stage.

<FIG> shows a multi-user CCDM <NUM> for two users, which replaces the single-user CCDM <NUM> in the embodiments of the probabilistic signal point shaping device <NUM>, <NUM> shown in <FIG>. In the following, a more detailed description of the operation of the MU CCDM <NUM> is given. The same concept can also be applied for more than two users.

The message M<NUM> intended for the first user is given to a first CCDM <NUM>, which operates with a defined P(A) and generates first output mapping symbols A<NUM>,. The probability of occurrence of those output mapping symbols as well as the (already generated) output mapping symbols is analyzed by an analysis unit <NUM> (or corresponding circuitry) and Pt(B|A) with <NUM> ≤ t ≤ n is computed such that the desired output probability of occurrence P(C) is achieved. The second CCDM <NUM>, which encodes message M<NUM> for user <NUM>, operates with Pt(B|A) and generates second output mapping symbols B<NUM>,. Note that the second CCDM <NUM> has a time-variant input distribution Pt(B|A) which means that each output mapping symbol Bt is generated by a specific target distribution Pt(B|A). After Bt is generated, the next Pt+<NUM>(B|A) is computed which generates Bt+<NUM> and so forth. The combination unit <NUM> (or corresponding circuitry) combines the first output mapping symbols A<NUM>,. , An and the second output mapping symbols B<NUM>,. , Bn, e.g. computes a time-invariant and invertible linear combination (i.e. amplitude multiplication and addition) of both mapping symbols.

In an embodiment the "alphabet" of C will be decomposed in term of the "alphabets" of A and B. Let the number of pair x in A and y in B be written as N_{x,y}. The number of symbols that are already emitted up to time entries i is N_{x,y}[i]. Then the probability observed at time entries i P(y'|x)[i] = N_{x,y'}[i]/Z with Z = sum N(x,y') over y'.

The analysis and computation unit considers the value of A<NUM>,. , An each being a subset of amplitudes levels (or complex signal points). At point in time t with <NUM> ≤ t ≤ n, the unit counts the number of occurrence of each particular amplitude level within the interval [<NUM>, t] which is represented by Ht(A). Based on this an empirical and instantaneous Pt(A) is computed which is <MAT>. Pt(A) can be seen as an instantaneous target distribution function which consider the actual target P(A) and the history of previous first mapping symbols up to point in time t, i.e. A<NUM>,. Furthermore, the analysis and computation unit considers the value of C<NUM>,. At point in time t, the unit counts the number of occurrence of each particular amplitude level within the interval [<NUM>, t] which is represented by Ht(C). Based on this, an empirical and instantaneous Pt(C) is computed which is <MAT>. Next step is to compute instantaneous target distribution for second CCDM which is <MAT> where Pt=<NUM>(C) = P(C). Note that with every new output a point in time t, the above procedure is repeated unit the last Bn and Cn is computed.

The MU CCDM <NUM> thus generates output mapping symbols C<NUM>,. , Cn which follows a target output probability distribution P(C). The output probability distribution P(C) is given and optimized for specific channel conditions. The first probability distribution P(A) can be chosen arbitrarily but in such a way that the computed probability distributions Pt(B|A) exists which generates the desired output distribution P(C). Some choices of P(A) are more beneficial for practical purpose, for example if P(A) is mapped according to the probability of the most robust bit, then it will be easier to perform log-likelihood-ratio (LLR) calculation at the receiver.

In the MU CCDM <NUM> the first CCDM <NUM> and/or the second CCDM <NUM> may be configured like the SU CCDM <NUM> shown in <FIG> and explained above, i.e. one or both of them may be configured to map data blocks of input bits of an input bit stream onto mapping symbols, wherein said mapping symbols are distributed according to a predetermined probability distribution and represented by complex-valued signal points or non-uniformly spaced amplitude levels. In other embodiments the first CCDM <NUM> and/or the second CCDM <NUM> may be configured differently, e.g. as described in the above cited paper of Schulte and Böcherer, i.e. one or both of them may be configured to map data blocks of input bits of an input bit stream onto mapping symbols, wherein said mapping symbols are distributed according to a predetermined probability distribution and represented by uniformly spaced amplitude levels.

Further, the mapping of the data blocks of the input bits of the respective input bit streams of the CCDMs <NUM> and <NUM> may be identical or different. For instance, the data blocks of both input bit streams may be mapped onto complex-valued mapping symbols or onto real-valued amplitude levels. In other embodiments the data blocks of the first input bit stream may be mapped onto complex-valued mapping symbols and the data blocks of the second input bit stream may be mapped onto real-valued amplitude levels.

Still further, the data blocks of input bits of the first input bit stream may be mapped onto complex-valued first mapping symbols arranged in a first predetermined area of the complex plane and the data blocks of input bits of the second input bit stream may be mapped onto complex-valued second mapping symbols arranged in a second predetermined area of the complex plane. Hereby, the first and second predetermined areas are preferably different, but may generally also be overlapping or identical.

Hereby, the data blocks of input bits of the first input bit stream may be mapped onto complex-valued first mapping symbols having a phase in a first predetermined range and/or an amplitude in a first predetermined range (e.g. in a quadrant or octant) to map the data blocks of input bits of the second input bit stream may be mapped onto complex-valued second mapping symbols having a phase in a second predetermined range and/or an amplitude in a second predetermined range. Again, the first and second predetermined ranges are preferably different, but may generally also be overlapping or identical.

For improved performance if channel conditions for user <NUM> and user <NUM> are substantially different, two P matrices (and two redundancy generators <NUM>, <NUM>) are applicable as shown in the embodiments of a probabilistic signal point shaping device <NUM> and <NUM> according to the present disclosure depicted in <FIG>. Before the redundancy generators <NUM>, <NUM>, there is a splitter <NUM> which separates bits belonging to user <NUM> and user <NUM>, respectively. Each bit stream is subsequently passed through an individual redundancy generator <NUM>, <NUM>, each applying a separate P matrix, i.e. there are now two P matrices P1 and P2, one for each user. After the individual redundancy generators <NUM>, <NUM> a combiner <NUM> reunifies both bit streams. The remaining processing is substantially identical as illustrated above with respect to <FIG> and <FIG>, except that the MU CCDM <NUM> is required as illustrated in <FIG>. The use of different redundancy generators <NUM>, <NUM> and two P matrices P1 and P2 is optional but beneficial if e.g. channel conditions are unequal between users.

The multi-user mapping device may thus also be realized by circuitry configured to:.

The analysis of the probability of occurrence of the first signal points of the first mapping symbols and earlier (i.e. previously emitted) final mapping symbols may be made by.

The second probability distribution may hereby be determined by dividing each computed probability of occurrence of the final mapping symbols by the probability of occurrence of the associated first signal point of the first mapping symbols, wherein the association is determined by a combination rule defining combination of first and second mappings symbols.

An example is provided in the following to illustrate the multi-user operation in the scheme as illustrated in <FIG>. Two users shall be assumed in this example. User <NUM> has amplitude levels u<NUM> = {<NUM>,<NUM>} whereas user <NUM> has amplitude levels u<NUM> = {<NUM>, <NUM>, <NUM>, <NUM>}. The combiner <NUM> computes u<NUM> + <NUM> · u<NUM> - <NUM>. During the design process the probability of occurrence of the output symbols and the bit level assignment is defined. Both is shown in Table <NUM>. In more detail, the first bit is assigned to user <NUM> and the second and third bits are assigned to user <NUM>.

As an example, the amplitude levels and the output stream after bit labelling by the bit labelling unit <NUM> are:.

The splitter <NUM> will split the output stream into two streams:.

Assuming that the redundancy generators <NUM>, <NUM> are designed such that the output given the input streams is equal to:.

Then possible outputs of the combiner <NUM> would be:.

The arrangement of the bit combiner output is arbitrary and irrelevant, as long as it is known and the same on the receiver and the transmitter. This output will be converted into sign and multiplied with the output stream of the CCDM <NUM> to generate the transmitter output. The number of combiner output bits may be designed to match the number of amplitude levels (both are <NUM> in this example).

Further, the bit label assignments into streams are not necessarily disjoint. It is possible to have an overlap. This overlapping assignment may help in some embodiments, e.g. to match the FEC code frame size, to allow successive decoding on the receiver, etc..

Claim 1:
A probabilistic signal point shaping device comprising circuitry configured to:
- map data blocks of input bits of an input bit stream onto mapping symbols by use of constant composition distribution matching, CCDM, wherein said mapping symbols are distributed according to a predetermined probability distribution and represented by non-uniformly spaced complex-valued signal points or non-uniformly spaced amplitude levels,
- assign bit labels to said mapping symbols,
- determine redundancy bits from the bits of said bit labels,
- transform said redundancy bits into a redundancy rule, and
- apply the redundancy rule to the mapping symbols to obtain output symbols.