WO2000057559A1

WO2000057559A1 - Method and processor unit for mapping information with a variable range of values onto code words

Info

Publication number: WO2000057559A1
Application number: PCT/DE2000/000605
Authority: WO
Inventors: Bernhard Raaf
Original assignee: Siemens Aktiengesellschaft
Priority date: 1999-03-18
Filing date: 2000-03-01
Publication date: 2000-09-28

Abstract

Information with a variable range of values is mapped onto two code words with knowledge of the a priori value of the function to be mapped as follows: the value of the function to be mapped is divided by the smallest whole number that is greater or equal to the square root of the number of possible values of the function to be mapped. The first code word (Word 1) allows values between 0 and the whole number result of the division and the second code word (Word 2) allows values between 0 and the remainder. This results in an even distribution of the code words and reduces error spread.

Description

description

Method and processor unit for mapping information with a variable value range onto code words

The invention relates to a method and a processor unit for mapping information with a variable value range onto code words, in particular onto code words with a variable value range.

For the transmission of information with a variable value range, it is known to map this information to binary code words and to transmit the information assigned to them by transmitting these code words. Different assignments of information, which can be present, for example, in decimal form, to binary code words with several bit positions are known.

It is known to encode information that contains, for example, 1024 different values, to map this information to 2 code words each of length 5. The less significant bits are in the first code word and the more significant bit positions are in the second code word. If fewer than 1024 values are to be encoded, the second code word contains less information than the first code word. Since a priori information about the smaller range of values can be used for decoding, the error rate for the second code word is smaller than for the first code word.

Since all of the information transmitted by means of the two code words is incorrect if one of the two code words is decoded incorrectly, this known coding scheme for transmitting information with a variable value range is disadvantageous because the error rate for the first code word, which is large relative to the error rate for the second code word the decoding performance for the entire information deteriorates. The invention is therefore based on the problem of specifying a method and a processor unit which make it possible to map information with a variable value range to binary code words, so that the information can be decoded with little computation complexity and few errors.

According to the invention, this problem is solved by the features of the independent claims. Further training results from the subclaims.

In the case of a restricted range of values for the information to be mapped, the range of values of at least one code word is reduced, the range of values of the code words differing as little as possible.

The invention is therefore based on the idea of using a priori information about a restricted value range of the information to be mapped onto the code words when decoding the code words, so that only a reduced value range of the code words is used during the decoding.

A further development of the invention provides for the number of relevant bit positions of at least one binary code word to be reduced in the case of a restricted value range of the information to be mapped, the number of relevant bit positions of the code words differing by a maximum of 1.

It is thus possible to use a priori information about a restricted range of values of the information to be mapped to the code words when decoding the code words, so that only relevant bit positions of the code words are used for the decoding. To this a priori

The number is to use information as efficiently as possible the bit positions relevant for coding and decoding are the same for all code words or differ by 1.

A further development of the invention provides for the information to be mapped onto code words in such a way that the number of relevant bit positions of a code word is constant over a large interval of the value range of the information to be mapped when the value range of the information to be mapped changes, and the number of relevant bit positions of a code word if the value range of the information to be mapped is changed in steps of at most 1.

This enables the information to be transmitted to be distributed as evenly as possible over several code words and thus an efficient use of the a priori information.

The invention is described in more detail below with the aid of preferred exemplary embodiments, the figures listed below serving to explain them:

Figure 1 block diagram of a mobile radio system;

FIG. 2 block diagram of a processor unit;

FIG. 3 shows schematic representations of the mapping of information onto binary code words;

Figure 4 Representation of an optimized scheme for mapping information to code words.

FIG. 1 shows a cellular mobile radio network, such as the GSM (Global System for Mobile Communication) system, which consists of a large number of mobile switching centers MSC which are networked with one another or which provide access to a fixed network PSTN / ISDN . Furthermore, these mobile switching centers are each at least MSC connected to a base station controller BSC, which can also be formed by a data processing system. A similar architecture can also be found in a UMTS (Universal Mobile Telecommunication System).

Each base station controller BSC is in turn connected to at least one base station BS. Such a base station BS is a radio station which can establish a radio connection to other radio stations, so-called mobile stations MS, via a radio interface. Information can be transmitted between the mobile stations MS and the base station BS assigned to these mobile stations MS by means of radio signals. The range of the radio signals of a base station essentially define a radio cell FZ.

Base stations BS and a base station controller BSC can be combined to form a base station system BSS. The base station system BSS is also responsible for radio channel management and allocation, data rate adaptation, monitoring of the radio transmission link, hand-over procedures and, in the case of a CDMA system, for the allocation of the spreading code sets to be used, and transmits them necessary signaling information to the mobile stations MS.

Using multiple access methods, data can be accessed via a

Radio interface can be efficiently transmitted, separated and assigned to one or more specific connections or the corresponding subscriber. A time multiple access TDMA, a frequency multiple access FDMA, a code multiple access CDMA or a combination of several of these multiple access methods can be used for this purpose.

The resulting physical channels are assigned to logical channels according to a defined scheme. There are two basic types of logical channels:

Signaling channels (or control channels) for the transmission of signaling information (or control information) and Traffic channels (TCH) for the transmission of user data. The signaling channels are further divided into:

- Broadcast Channels - Common Control Channels

- Dedicated / Access Control Channel DCCH / ACCH

The group of broadcast channels includes the broadcast control channel BCCH, through which the MS receives radio information from the base station system BSS. The Random Access Channel RÄCH is one of the common control channels. In future systems, information about the data rate of data transmitted in a radio frame will be transmitted via a DPCCH (Dedicated Physical Control Channel) using a so-called Transport Format Combination Indicator (TFCI).

FIG. 2 shows a processor unit PE, which can be contained in particular in a functional unit, such as a communication device, a base station BS or a mobile station MS. It contains a control device STE, which essentially consists of a program-controlled microcontroller, and a processing device VE, which consists of a processor, in particular a digital signal processor, both of which have write and read access to memory modules SPE.

The microcontroller controls and monitors all essential elements and functions of the functional unit that contains the processor unit PE. The microcontroller, the digital signal processor, part of the digital signal processor or a special processor is responsible for carrying out the mapping of information onto code words.

An input / output interface I / O is used for the input / output of user or control data, for example to an MMI control unit, which contain a keyboard and / or a display can. The elements of the processor unit PE can be connected to one another by means of a digital bus system BUS.

Using such a processor unit PE, information can be mapped to code words using one of the methods described below.

In FIG. 3, a known scheme for mapping information with a variable value range onto two code words, each with five bit positions, is shown on the left-hand side. The following is an example of the illustration of information that comprises at least 65 values. Information that contains less than 65 values can be encoded accordingly.

If the value range of the information to be mapped comprises a maximum of 128 values, these 128 values are mapped to 7 bit positions, 5 bit positions of the first code word Word1 and 2 bit positions of the second code word Word2 being occupied. If the value range of the information to be mapped comprises a maximum of 256 values, 8 bit positions are occupied, again 5 bit positions of the first code word Word1 and 3 bit positions of the second code word Word2 being occupied. According to the illustration on the left in FIG. 3, this illustration is also continued accordingly for a range of values which comprises a maximum of 512 values and a range of values which comprises a maximum of 1024 values. Obviously, such a distribution of information over two code words is unbalanced, which leads to an inefficient use of the a priori information when decoding such coded information.

A new mapping or coding scheme is therefore proposed, which leads to a more balanced distribution of the information between the two code words. On the right-hand side of FIG. 3, it is shown that information to be mapped includes a range of values that comprises a maximum of 128 values 7 bit positions are occupied, 4 bit positions of the first code word Word1 are occupied and 3 bit positions of the second code word Word2 are occupied. Correspondingly, with 8 occupied bit positions, 4 bit positions of the first code word Word1 and 4 bit positions of the second code word Word2 are occupied. In the case of 9 occupied bit positions, 5 bit positions of the first code word Word1 and 4 bit positions of the second code word Word2 are occupied. If the range of values of the information to be mapped comprises more than 512 values, then all bit positions of both code words are occupied.

One embodiment variant provides that the information is first mapped to an intermediate code word, the bit positions of this intermediate code word being numbered starting from zero, the least important bit position (LSB) being assigned to the number zero. The bit positions of the intermediate code word are then mapped to the two code words in accordance with the diagram on the right in FIG. 3, the zero bit position of the intermediate code word being mapped to the zero position of the first code word Word1, the first

Bit position of the intermediate code word is mapped to the zeroth bit position of the second code word Word2, the second bit position of the intermediate code word is mapped to the first bit position of the first code word Word1, the third bit position of the intermediate code word is mapped to the first bit position of the second code word Word2, the fourth bit position of the Intermediate code word is mapped to the second bit position of the first code word Word1, the fifth bit position of the intermediate code word is mapped to the second bit position of the second code word Word2 etc., that is to say the bit positions of the two

Code words are alternately occupied with the bit positions of the intermediate code word.

The mapping scheme shown on the right in FIG. 3 only provides for the case of the same number of occupied

Bit positions in both code words a balanced distribution of the information. To achieve a balanced distribution of the In order to achieve information in other cases as well, the information is subsequently distributed with a finer granularity than corresponds to a single information bit. This is possible because a biorthogonal decoder can not only use a priori information about the number of bit positions to be decoded, but also use information about the number of code words used, that is to say in principle possible to be decoded. This property is explained in more detail using the following example:

Assuming the information to be mapped contains 81 different values, nine different code words are assigned to the first code word and nine different code words are also assigned to the second code word. Such a balanced distribution is possible for all square numbers. In general, however, the information to be mapped is mapped to the two code words as follows: The value of the information to be mapped is divided by the smallest integer that is greater than or equal to the square root of the number of possible values of the information to be mapped. The first code word Word1 is then equal to the integer division result and the second code word Word2 is equal to the remainder of the division.

In order not to constantly have to completely change the mapping rule of information TFCI to code words or to adapt the current value range to a variable value range of the information TFCI to be mapped, an optimized coding scheme is presented below, which distributes the information TFCI to the code words as evenly as possible and also a change in the mapping rule from information to be mapped TFCI to code words is not necessary even in the event of a change in the range of values of the information to be mapped TFCI. This mapping of TFCI values to binary code words takes place according to the following rules: if TFCI <n ^Λ 2 + n, a first code word (Wordl) has the value n and a second code word (Word2) has the value TFCI - n ^Λ 2, otherwise a second code word (Word2) has the value n and a first code word (Wordl) the value n ^Λ 2 + 2 * n - TFCI, where

TFCI is the value of the information to be mapped (TFCI), and n is the largest integer that is less than or equal to the square root of TFCI.

The coding scheme generated by these rules is shown in FIG. 4, the values of the information to be displayed being shown in decimal form (numbers 0 to 1023) in a Word1 / Word2 diagram. The values of the five-digit code words are described in decimal form (0 to 31).

Knowledge of the range of values of the information to be mapped enables the calculation of the range of values of the two code words and thus allows the decoding result of the bi-orthogonal decoder to be improved.

Such a coding scheme leads to the following trip ice:

TFCI in decimal representation; Codewortl (Wordl) in decimal

Representation, Codeword2 (Word2) in decimal representation 0; 0.0

1 ; 1, 0

2; 1.1

3; 0.1

4; 2.0 5; 2.1

6; 2, 2

7; 1.2

8th; 0.2

9; 3.0 10; 3.1

11; 3, 2

12; 3, 3 13; 2, 3 14; 1.3 15; 0.3 16; 4.07; 4.1 18; 4.2 19; 4.3 20; 4, 4 21; 3.4 22; 2.4 23; 1.4 24; 0.4 25; 5, 0 26; 5.1 etc.

A corresponding decoding can be implemented as follows:

n: = maxQVor dl, Word!) TFCI = n ² + n + Word2 - Wordl

In one embodiment variant, it is possible to implement the coding scheme by means of tables instead of the algorithm described above.

An embodiment variant of the invention provides a coding scheme which generates the following trip ice:

TFCI; Codeword1 (Wordl) in decimal representation, Codeword2 (Word2) in decimal representation 0; 0.0

2; 0.1

3; 1.1

4; 2.05; 2.1 6; 0.2

7; 1.2

8th; 2, 2

9; 3.0 10; 3.1

11; 3.2

12; 0.3

13; 1.3

14; 2, 3 15; 3.3

16; 4.0

17; 4.1

18; 4, 2

19; 4.3 20; 0.4

21; 1.4

22; 2, 4

23; 3,

24; , 4 25; 5.0

26; 5.1, etc. and coding schemes derived therefrom, in which the code word pairs can be permuted as desired within the areas of underlined triple blocks.

Another embodiment variant of the invention provides a coding rule which generates the following trip ice: TFCI; Codewortl (Wordl) in decimal representation, Codewort2 (Word2) in decimal representation 0; 0, 0 (1; 1.0 2; 0.1 3; 1.1) (4; 2.0 5; 2.1 6; 0.2 7; 1.2

8th; 2, 2)

(9; .3.0

10; 3.1 11; 3.2

12; 0.3

13; 1.3

14; 2, 3

15 3.3) (16; 4.0

17; 4.1

18; 4.2

19; 4.3

20; 0.4 21; 1.4

22; 2, 4

23; 3.4

24; , 4)

(25; 5.0 26; 5.1 etc. and coding schemes derived from them, in which the code word pairs can be permuted as desired within the range of brackets.

Another embodiment provides a coding scheme that generates the following trip ice:

TFCI; Codeword1 (Wordl) in decimal representation, Codeword2 (Word2) in decimal representation 0; 0, 0 i; i, o

2; 0.1 3; 2.04; 1.1 5; 2.1 6; 0.2 7; 1.2 8th; 3.0

9; 2.2

10; 3.1

11; 3.2 12; 0.3

13; 1.3

14; 2, 3

15; 4.0

16; 3.3 17; 4.1

18; 4, 2

19; 4.3

20; 0.4

21; 1.4 22; 2.4

23; 3, 4

24; 4, 4

25; 5.0

26; 5.1 etc.

By incorporating the invention into the system concept of future mobile radio systems, in particular UMTS, it is possible to transmit information about the data rate of data transmitted in a radio frame by means of a so-called transport format combination indicator (TFCI) via a dedicated physical control channel DPCCH . If the number does not exceed 64, the TFCI values can be mapped to a code word of length 6. As soon as the number of TFCI values exceeds 64, the current TFCI value is mapped onto two binary code words, each with a length of five, according to a method or coding scheme described above. To achieve a coding gain, the resulting code words can be mapped to Walsh functions by using biorthogonal codes. For example, length 5 code words can be encoded using biorthogonal (16.5) block codes.

Claims

claims

1.Method for mapping information (TFCI) with a variable value range onto code words (Word), in which the value range of at least one code word (Word2) is reduced if the value range of the information (TFCI) is restricted, and the value range of the code words (Word ) differs as little as possible.

2. The method according to claim 1, wherein the value range of at least one code word (Word2) is reduced if the value range of the information (TFCI) is restricted, and the value range of the code words (Word) differs by a maximum of one.

3. The method as claimed in one of the preceding claims for mapping information (TFCI) with a variable value range onto binary code words (Word) with several bit positions, in which the number of relevant bit positions of at least one code word (Word2) is reduced if the value range of the information ( TFCI) is limited, and the number of relevant bit positions of the code words (Word) differs by a maximum of one.

4. The method according to any one of the preceding claims, in which the information (TFCI) are mapped onto code words (Word) in such a way that the number of relevant bit positions of a code word (Word) changes as far as possible when the value range of the information to be mapped (TFCI) changes Intervals of the value range of the information to be mapped (TFCI) is constant, and if the value range of the information to be mapped (TFCI) changes in steps of one, the number of relevant bit positions of a code word (word) is changed in steps of a maximum of one.

5. The method as claimed in one of the preceding claims, in which the information is mapped onto two code words such that: if TFCI <n ^Λ 2 + n, a first code word (Word1) has the value n and a second code word (Word2) the value TFCI - n ^Λ 2, otherwise a second code word (Word2) has the value n and a first code word (Wordl) has the value n ^Λ 2 + 2 * n - TFCI, where TFCI is the value of the information to be mapped (TFCI), and n is the largest integer that is less than or equal to the square root of TFCI.

6. The method as claimed in one of the preceding claims, in which the information (TFCI) is mapped onto two code words (Word) according to the following scheme:

TFCI; Codewordl (Wordl) in decimal notation, Codeword2 (Word2) in decimal notation 0; 0.0 1; 1.0 2; 0.1

3; 1.1

4; 2, 0

5; 2.1

6; 0.2

7; 1.2

8th; 2, 2

9; 3.0

10; 3, 1

11; 3, 2

12; 0, 3

13; 1, 3

14; 2, 3

15; 3, 3

16; 4.0

17; 4, 1

18; 4, 2 19; 4.3 20; 0.4 21; 1.4 22; 2, 4 23; 3.4 24; 4, 4 25; 5.0 26; 5.1 etc., whereby, the code word pairs within the areas underlined triple are permutable as desired.

7. The method according to any one of the preceding claims, wherein the information is information (TFCI) about the data rate of data transmitted in a radio frame, which are mapped to two code words (Word) per radio frame.

8. A method for mapping information (TFCI) onto code words, in which the information (TFCI) is mapped onto a code word of length 6 if the value range of the information to be mapped is less than 65, and the information (TFCI) according to one of the preceding Claims to be mapped to two code words of length 5 if the value range of the information to be mapped is greater than 64.

9. processor unit (PE), which is prepared such that

Information (TFCI) according to one of the preceding claims can be mapped to code words.