WO2003085873A2

WO2003085873A2 - Method and communications device for adapting the data transfer rate in a communications device

Info

Publication number: WO2003085873A2
Application number: PCT/DE2003/001061
Authority: WO
Inventors: Martin DÖTTLING; Bernhard Raaf
Original assignee: Siemens Aktiengesellschaft
Priority date: 2002-04-08
Filing date: 2003-04-01
Publication date: 2003-10-16
Also published as: WO2003085873A3

Abstract

The invention relates to a method for adapting the data transfer rate of a data flow in a communications device according to which: the data flow can be subdivided into at least one data block containing transmission bits to be transmitted; the transmission bits are formed by a coding process from information-carrying input bits; transmission bits determined from a data block of the data flow are removed (dotted) in order to adapt the data transfer rate; a dotting pattern stipulates which transmission bits are to be removed, and; the dotting pattern is constructed in such a manner that transmission bits are preferably removed that, during the coding process, depend on few input bits. The invention also relates to a corresponding communications device.

Description

description

Method and communication device for adapting the data rate in a communication device

The present invention relates to a method for adapting the data rate in a communication device and a corresponding communication device according to the preamble of claim 16.

Different applications in communication systems mostly work with different data rates. The underlying transmission channels usually offer e.g. because of the embedding in certain broadcast formats, only a fixed one

Data transfer rate or raw data transfer rate, or only a discrete set of such data rates. It will therefore generally be necessary to adapt the data rates to one another at the corresponding interface. This is described in the following using an example from UMTS standardization:

Work is currently underway to standardize the so-called UMTS mobile radio standard ('Universal Mobile Telecommunication System') for mobile radio devices of the third mobile radio generation. According to the current state of UMTS standardization, it is provided that the data to be transmitted via a high-frequency channel are subjected to channel coding, with convolutional codes being used in particular for this purpose. The channel coding encodes the data to be transmitted redundantly, which enables a more reliable recovery of the transmitted data on the receiver side. The code used in the channel coding is characterized by its code rate r = k / n, where k denotes the number of data or message bits to be transmitted and n the number of bits present after coding. The lower the code rate, the more efficient it is Rule the code. However, a problem associated with coding is that the data rate is reduced by the factor r.

In order to adapt the data rate of the coded data stream to the respective possible transmission rate, a rate matching ('rate matching') is carried out in the transmitter, bits being either removed from the data stream or doubled in the data stream according to a certain pattern. Removing bits is called 'puncturing' and doubling is called 'repeating'.

According to the current state of UMTS standardization, it is proposed to use an algorithm for rate adaptation which punctures with an approximately regular puncturing pattern, i.e. the bits to be punctured are distributed equidistantly over the coded data block to be punctured.

In addition, it is known that in the case of convolutional coding, the bit error rate (BER) decreases at the edge of a correspondingly coded data block. It is also known that the bit error rate within a data block can be changed locally by puncturing that is distributed unevenly. It is also known from WO 01 / 26273A1 and WO 01/39421 AI that it is advantageous for the individual

Puncture data blocks of the data stream for adapting the data rate according to a specific puncturing pattern, the puncturing pattern being designed such that it has a puncturing rate which increases continuously from a central region of the individual data blocks to at least one end of the individual data blocks.

The present invention is therefore based on the object of providing a method for adapting the data rate of a data stream in a communication device and a corresponding communication device which have a ensure a satisfactory bit error rate and can be used in particular in mobile radio systems with convolutional coding.

This object is achieved according to the invention by a method with the features of claims 1 and 16 or by a communication device with the features of claim 16. The subclaims define preferred and advantageous embodiments of the present invention.

The system of the convolutional code was used to find heuristic puncturing patterns, after which all bits of the punctured data block have a bit error rate that corresponds to their importance.

The puncturing pattern preferably has a puncturing rate increasing from the central region to both ends of the respective data block. In this way, the bits are punctured more strongly at the beginning and end of the data block to be punctured, this being done not with a uniform puncturing rate but with a puncturing rate that increases essentially towards the two ends of the respective data block, i.e. the distance between the punctured bits becomes the two ends of the

Data blocks are getting shorter and shorter on average. As will be explained in the following, the puncturing rate surprisingly does not necessarily have to increase strictly monotonously towards the ends, or in other words the puncturing distance decreases strictly monotonously. Rather, due to the specific properties of the convolutional codes used and in particular the generator polynomials used, it can also be advantageous to use somewhat irregular patterns.

This puncturing leads to an evenly distributed error rate of the individual over the punctured data block Bits and also results in a reduced overall error probability.

The present invention is particularly suitable for adapting the data rate of a convolutionally coded data stream and can therefore preferably be used in UMTS mobile radio systems, this relating to both the area of the mobile radio transmitter and that of the mobile radio receiver. However, the invention is not limited to this area of application, but can generally be used wherever the data rate of a data stream has to be adapted.

The present invention is described in more detail below with reference to the accompanying drawing using preferred exemplary embodiments. 1 shows a simplified block diagram of a mobile radio transmitter according to the invention,

2: the bit error rate BER per bit for puncturing according to an embodiment in HS-SCCH, Part 2,

Coding with R = l / 3 with a ratio of the energy of the transmitted bits to the noise power density E _s / N ₀ = -2 dB. The HS-SCCH channel is the so-called high-speed shared control channel, via which certain configuration information is transmitted and which can be divided into two parts, the so-called Part 1 and Part 2. Part 1 is transmitted first and contains the information that the mobile station needs first to process the following data channel, Part 2 contains information that the mobile station only needs a little later. This division in two means that the delay through the HS-SCCH is as small as possible, since only the first part has to be decoded before the data can be received.

3: the bit error rate BER per bit for those in UMTS (specification 25.212 v5.0.0, chapter 4.2.7 "rate matching") proposed rate adjustment for HS-SCCH, Part 2, with a ratio of the energy of the transmitted bits to the noise power density of E _s / N _υ = -2 dB.

Fig. 4: a comparison with an inventive

Puncturing (upper curve, crosses) or conventional puncturing (lower curve, circles) with regard to the resultant overall error probability, the probability that at least one bit of a block was incorrectly transmitted (so-called frame error rate).

Fig. 5: underlying schemes for convolutional codes in UMTS.

Fig. 6: the bit error rate BER per bit for in UMTS

(Specification 25.212 vδ.OO, Chapter 4.2.7 "Rate matching") proposed rate adjustment for HS-SCCH, Part 1, with a ratio of the energy of the transmitted bits to the noise power density of E _s / No = -3 dB

Fig. 7: how many input bits are affected when an output bit is punctured in the different output stages Output 1, Output 2 and Output 3.

8: Which input bits (bit numbers) are affected by the puncturing.

Figure 9. : a table with the results of puncturing depending on the number of punctured bits.

10: the bit error rate BER per bit for puncturing according to an exemplary embodiment in HS-SCCH, Part 1, with a signal-to-noise ratio of the energy of the transmitted bits to the noise power density of E _s / N ₀ = -3 dB 11: Different exemplary embodiments for puncturing 8 bits (48 to 40 bits) for coding with rate 1/3

Fig. 12: different embodiments for a

Puncturing 31 bits (puncturing 111 to 80 bits), R = 1/3

13: different exemplary embodiments for a repetition of 31 bits (repetition from 32 to 40 bits), R = y ₂

Fig. 14: different embodiments for a repetition of 6 bits (74 to 80 bits), R = 1/3

15: different exemplary embodiments for a repetition of 4 bits (36 to 40 bits), R = V ₂

16: different exemplary embodiments for puncturing 14 bits (54 to 40 bits), R = 1/3

FIG. 17: further exemplary embodiments for puncturing 31 bits (puncturing from 111 to 80 bits), R = 1/3. This figure can therefore also be regarded as a continuation of FIG. 12.

Fig. 18: an embodiment for puncturing from 108 to 80 bits, R = 1/3

Fig. 19: Exemplary embodiments for puncturing from 114 to 80 bits, R = 1/3

Fig. 20: Exemplary embodiments for puncturing from 117 to 80 bits, R = 1/3

Fig. 21: Exemplary embodiments for puncturing from 52 to 40 bits, R = 1/2 Fig. 22: Exemplary embodiments for puncturing from 46 to 40 bits, R = 1/2

Fig. 23: Exemplary embodiments for puncturing from 54 to 40 bits, R = 1/3

24: Exemplary embodiments for puncturing from 56 to 40 bits, R = 1/2

Fig. 25: Exemplary embodiments for a repetition from 36 to 40 bits, R = 1/2

Fig. 26: Exemplary embodiments for puncturing from 48 to 40 bits

Fig. 27: Exemplary embodiments for puncturing from 11 to 80 bits.

Fig. 28: Rate adjustment rule from the 3 GPP

Specification 25.212 v5.0.0, chap. 4.2.7 "Rate matching"

In general, the lines in the tables with numbers printed entirely in bold mean the respectively particularly preferred exemplary embodiment, but the quality of the other exemplary embodiment does not necessarily deviate significantly from this exemplary embodiment which is emphasized. In Figures 26 and 27, however, bold numbers denote those described by the inventive method

Construction principle of the rate adjustment formula punctured or repeated bits at the beginning or end of the repetition pattern. These are thus fixed, whereas the position of the bits not shown in bold can also shift slightly (typically by one position) by varying the parameters within the scope of this invention. 1 schematically shows the structure of a mobile radio transmitter 1 according to the invention, from which data or communication information, in particular voice information, is transmitted to a receiver via a high-frequency transmission channel. 1 shows, in particular, the components involved in the coding of this information or data. The information supplied by a data source 2, for example a microphone, is first converted into a bit sequence using a digital source encoder 3. The speech-coded data are then coded with the aid of a channel encoder 4, the actual useful or message bits being coded redundantly, as a result of which transmission errors can be recognized and then corrected. The channel encoder 4 can be one

Act convolutional encoder. The code rate r resulting in the channel coding is an important variable for describing the code used in each case in the channel coding and, as has already been mentioned, is defined by the expression r = k / n. K denotes the number of

Data bits and n the total number of coded bits, i.e. the number of redundant bits added corresponds to the expression n - k. A code with the code rate r defined above is also referred to as an (n, k) code, the performance of the code increasing with decreasing code rate r. So-called block codes or convolutional codes are usually used for channel coding.

In the following it should be assumed that - as is determined by the current state of UMTS standardization - convolutional codes are used for channel coding. An essential difference from block codes is that convolutional codes do not encode individual data blocks one after the other, but that they are continuous processing, with each current code word of an input sequence to be coded also depending on the previous input sequences. Independent of Code rate r = k / n convolutional codes are also characterized by the so-called influence length or 'constraint length' K. The 'constraint length' specifies the number of cycles of k new input bits of the channel encoder 4 by means of which a bit influences the code word output by the channel encoder 5.

The following convolutional codes are used for UMTS, as shown in FIG. The illustration is from the specification 25.212 chap. 4.2.3.1 "Convolutional coding" (convolutional codes) taken.

Before the channel-coded information is transmitted to the receiver, it can be fed to an interleaver 5, which rearranges the bits to be transmitted in time according to a certain scheme and thereby spreads them in time, as a result of which the errors which generally occur in bundles are distributed in order to create a so-called ) Receive transmission channel with a quasi-random error distribution. The information or data coded in this way is fed to a modulator 7, the function of which is to modulate the data onto a carrier signal and to transmit it to a receiver via a high-frequency transmission channel 3 in accordance with a predetermined multiple access method.

For transmission, the coded data stream is divided into data blocks, the channel encoder 4 being set to a known state at the start of a data block. In the end, each coded data block is terminated by so-called 'tail bits', so that the channel encoder 4 is again in a known state. This construction of the convolutional code and of the channel encoder 4 ensures that the bits at the beginning and end of an encoded data block are better protected against transmission errors than in the middle of the block. It is irrelevant whether these tail bits all have the known value 0, or some other value. The values of these tail bits can also be chosen arbitrarily, whereby both sender and receiver must know the values to be used.

The error probability of a bit differs depending on its position within the respective data block. This effect is used, for example, in voice transmission in GSM mobile radio systems by placing the most important bits at the two ends of the block, where the probability of errors is lowest. In data transmissions, however, data packets are generally already discarded when only a single transmitted bit is faulty, which can be determined, for example, in the receiver by a so-called 'cyclic redundancy check' (CRC). It is therefore not possible to speak of important or less important bits in a data transmission, but all bits are to be regarded as equally important. If errors occur in a control block, i.e. a data block that contains control information that contains information about how subsequent user data are encoded and transmitted, it is generally no longer possible to correctly detect this user data if only a single bit is received incorrectly because the received data is then interpreted incorrectly.

In order to adapt the data rate of the coded data stream to the respective possible transmission rate, a rate adjustment ('rate matching') is carried out in front of the modulator 7. In the exemplary embodiment shown in FIG. 1, the rate adjustment takes place in the rate adjustment unit 6b, the puncturing unit 6a first performing puncturing in accordance with a specific puncturing pattern in order to achieve a more uniform error distribution over a data block. The sequence of the puncturing unit 6a and the interleaver 5 shown in FIG. 1 are to be understood only as an example. The interleaver can also be arranged after the unit 6b. Likewise, the interleaver 5 can also be replaced by two interleavers before and after the rate adjustment unit 6b, etc.

It is therefore also an object of this invention to further optimize puncturing patterns and in particular to adapt them to the polynomials used for the channel encoder. It is therefore the task, depending on the convolutional code used (including the polynomials used) and the block length, to select the amount of bits to be punctured or repeated so that the decoding can be carried out as well as possible. As a rule, there are a large number of possibilities, so that it is at least very time-consuming and resource-consuming, a very good one

To develop rate adjustment patterns purely through simulation. For example, if you want to examine all possible puncturing patterns for puncturing from 48 bits to 40 bits, then that would be 48! / (8! * 40!) = 377348994 different possibilities that cannot be examined in a reasonable time.

This problem arises particularly for short block lengths, such as. B. for the control information of the UMTS extension HSDPA, and there in particular the HS-SCCH channel (High Speed Shared Controll CHannel). This channel transmits configuration information which specifies how the actual user data sent via a special data channel is coded and further details, for example the spreading codes used for transmission. In contrast to the data channel, over which a lot of data can be transmitted, this is comparatively little data. In UMTS, convolutional codes with the rate V or 1/3 are used for coding, the polynomials used are shown in FIG. 5. Polynomials also refer to the exact design of the "tapping points", that is to say which delay stages for the individual output bit streams are tapped and linked by an exclusive-or operation. The invention is therefore particularly applicable to the so-called HS-SCCH (High Speed Shared Controll CHannel).

According to the current state of the art, the definition of the coding of the HS-SCCH is given in the specification 3GPP TS 25.212 V5.0.0 (2002-03), "Multiplexing and Channel coding (FDD) (Release 5)", in particular in chapter 4.6 "Coding for HS-SCCH ". This specification is otherwise referred to in this application as 25.212. Subchapter 4.6.6 "Rate matching for HS-SCCH" stipulates that the rate adjustment must be carried out in accordance with the standard rate adjustment algorithm in Chapter 4.2.7 "Rate matching", which essentially results in (as far as possible) equidistant puncturing or repetition ,

The block length of the two parts of the HS-SCCH is currently 8 bits for the first part, or if the end bits (tail bits) are included 16 bits, 29 bits for the second part, or if the end bits (tail bits) are also included become 37 bits. Since the specification is still in flow, changes in various parameters can also result in other block lengths. Furthermore, the convolutional codes with the rate h or 1/3 can also be used. The following rate adjustments are particularly relevant:

a) 32 on 40 (with code rate R = 1/2), or b) 48 on 40 (with code rate R = 1/3), and c) 74 on 80 (with code rate R = 1 / 2), or d) 111 to 80 (with code rate R = 1/3).

Procedure for determining puncturing and repeating patterns

At a glance, it can be seen that a puncturing and / or repetition or repetition is also carried out in such a way that the total bit error rate (BER) is minimal. Let us first consider the situation in FIG. 3: The bit error rate for the individual bits is plotted in a frame. The abscissa represents the index of the respective bit "(frame index)". It can clearly be seen that the first and last bits have a lower bit error rate. This can be understood in connection with the scheme for convolutional codes from FIG. 5: For the transmission, bits from the different are used for the convolutional code

Delay stages D of the decoder linked together. The first bits are e.g. also linked to the bits preceding them, that is, bits that actually do not exist. These "non-existent bits" are then set to a known value, usually zero. This is known to the receiver, who in turn decodes the first transmitted bits with these bits set to zero. Decoding is very safe here, since some of the bits are known with absolute certainty. The same applies to the last bits: Following them, bits, the so-called end bits or “tail bits”, are again artificially inserted into the delay elements D of the decoder; these end bits are in turn set to a known value, usually zero.

In the middle area bits are linked with each other, the value of which is not known with certainty at the receiver. Decoding therefore increases the likelihood that an error will occur, which is reflected in a higher bit error rate.

The envelope curve of the bit error rate compared to the frame number is here initially shaped convexly with even repetition or puncturing. There are now several options for how the envelope changes when the puncturing (or repetition) is changed: a) the envelope curve essentially represents a horizontal

(or approaches it):

This means that the bit error rate is essentially the same for all bits within a frame. This is done, for example, by dotting on the edge or

Repetition in the middle, or both, depending on the rate to be adjusted. b) concave design of the envelope

In this case, the edge is punctured so strongly, for example, that the bits in the central area of the frame have a lower bit error rate. This fact can be seen in Figure 2. c) the bit error rate is irregular compared to the

Frame number distributed. This case is not considered here for reasons explained below.

The following explanations relate to puncturing. Analogous considerations can also be made for repeating or for combinations of repeating and puncturing:

There are now many ways in which individual bits can be punctured. For example, as already mentioned above, one would like all sorts

Examine puncturing patterns for puncturing from 48 bits to 40 bits, that would be 48! / (8! * 40!) = 377348994 different possibilities, which cannot all be examined in a reasonable time.

The aim is therefore to eliminate opportunities that are not sensible from the outset. This is not done by repeating and / or puncturing, which is why alternative c) is not considered further here.

An ordering principle is shown in FIG. 7. For the first 9 input bits 1-9 and the last 9 input bits n-8 to n the puncturing level for the respective output stage Output 0, Output _χ l, Output 2 is shown. The output stages themselves, as can be seen in FIG. 5, are the respective output functions which are formed from all input bits preceding the input bit under consideration by linking.

The output stages of FIG. 5b) are considered here, that is to say the rate 1/3 convolutional encoder. For puncturing with as little information loss as possible, it is advisable to omit bits (puncturing) that have little influence on other bits. The

Puncturing level therefore indicates how many bits are affected by puncturing the considered bit.

An exemplary procedure for omitting or puncturing bits is shown in FIG. 8.

The first 9 input bits 1-9 and the last 9 input bits n-8 to n are specified in the first column. In the following columns, the bit numbers of the information bits affected by the puncturing, i.e. information bits or input bits, are for the respective one

Output stage Output 0, Output 1 and Output 2 shown. As in Fig. 7, the table fields have an increasingly dark background as the number of information bits affected increases. The bits belonging to the bright table fields are therefore candidates for puncturing.

A table is shown in FIG. 9, in which the important variables when puncturing near the ends, ie puncturing the first and last bits, are illuminated. N input bits (information bits) and k coded bits (bits at the output stage, output bits) are considered. The first column shows the number of punctured output bits (# punct bits), the last column (cumulative) the number of information bits affected at the input, whereby input bits that are affected several times, i.e. by puncturing several output bits, also be counted accordingly several times. The second column under Sequence indicates which output bit (bit number) was punctured in this step. The puncturing is done, starting with the least important bits in the first line, up to the following bits in the following lines. The total puncturing pattern for, for example, 7 bits to be punctured results from the bits specified in column 2 in rows 1 to 7, that is to say bits 1, k, 4, k-4, k-6, 2, k-1. This pattern thus comprises bits 1, 2, 4, k-6, k-4, k-1, k. Above the first line is the indexing for the first information bits 1-9 and the last information bits k-8 to k. For space reasons, only -8 etc. is written instead of k-8. The entries in the columns below the indexing of the information bits indicate how strong the information bit in question is by puncturing the

Output bits that are specified in the 2nd column up to the respective line and are therefore punctured are affected. That is, how many of the punctured output bits were associated with this information bit. This is a measure of how much the information bit in question has been weakened by the puncturing.

The last column (cumulative) finally shows the sum of these impairments. It is called the cumulative puncturing strength here.

The column mean indicates the ratio V of the sum of the last column divided by the number of information bits concerned. For example, for 6 punctured bits, V = (2 + 1 + 1 + 1 + 1) / (1 + 1 + 1 + 1 + 1) = 1.2

The mean puncturing rate (mean P-rate) is the column "mean value" divided by 18, the total number of "exclusive or" links occurring per information bit during the encoding. One way to puncture any number of bits is to make tables analogous to those mentioned above. For rate 1/3 and the polynomials considered Convolutional encoder, the tables shown can be used. With other coding rates and / or other polynomials, the tables can easily be determined analogously. With the help of these tables, a puncturing order is then determined, where those output bits are first punctured which have only a minor influence on the cumulative puncturing strength. If there are several alternatives, then bits are preferably punctured which minimize the maximum of the puncturing strength of the individual bits.

For a higher number of bits to be punctured and / or longer block lengths, i. d. As a rule, the information from the tables can be combined with the idea of puncturing the entire block as evenly as possible. It is then advisable to puncture additional bits in the middle part that are generated by the generator polynomial with the fewest powers, i.e. are generated with the fewest links. At the same time, however, care must be taken to ensure that the overall distribution of the puncturing strength in the central region of the frame does not show any significant increases.

The same applies to repetition, in each case with the opposite sign. This means that bits that would be punctured first according to the heuristic are now repeated last and that generally a uniform repetition is carried out first in the middle section, preferably by the polynomials with the most links. Then those bits are repeated on the edge that (in the case of puncturing) have the greatest possible influence on the cumulative puncturing strength.

In contrast to methods in which the puncturing rate increases steadily towards the ends,. this leads to an unexpected result in itself, since one would expect the reliability of the coded bits to increase steadily towards the ends. However, a closer look at the polynomials for the convolutional encoder used shows that this assumption is surprisingly incorrect. Through the Specific properties of the polynomials, especially at the end, result in coded bits that contribute less effectively to coding. However, these bits do not appear at the end in ever increasing proportions, but are somewhat irregularly distributed. By aligning the puncturing pattern specifically to these “weak” bits, ie preferably puncturing these bits, the coding can be further improved.

The invention therefore uses a heuristic method which allows:

• approximately determine the effect of puncturing / repetition of a coded bit on the underlying information bits using a newly defined, heuristic metric, • selectively and specifically select bits for each convolutional code that are to be punctured or repeated,

• severely restrict the number of rate adjustment patterns to be examined.

After a few promising rate adaptation patterns have been determined based on this method, these are compared on the basis of the frame error rate and the bit error rate of each individual information bit (hereinafter referred to as bit error rate distribution). Iteratively, based on the developed metric, the

Rate adjustment patterns are further refined and optimized. The bit error rate distribution of the unpunctured / non-repeated block serves as start information

The puncturing strength Si pro is used as a heuristic metric

Bit information bit i defines the number of links between an information bit and the respective output bits of the encoder that are not transmitted by the puncturing. Si is therefore positive for puncturing. For repetition, Si, k = n-1 is defined for each link transmitted n times. S _m a _x is the maximum possible puncturing strength, given by the code-specific total number of existing links:

A good rate adjustment pattern is sought according to the following quality criteria:

1. Choose the cumulative punctuation strength close to the possible minimum

2. Make sure the bit error rate is distributed as evenly as possible over all information bits

For the selection of the bits to be punctured / repeated, tables are set up based on the generator polynomials of the code, for the beginning and the end of the coded block, which represent the cumulative puncturing strength per coded bit, as well as the information bits concerned. The coded bits can thus be divided into so-called classes of cumulative puncturing strength.

According to the above quality criterion, bits to be punctured / repeated are selected on the basis of these tables in such a way that for those information bits that show a lower bit error rate than other bits, the puncturing strength is increased and at the same time the cumulative puncturing strength is kept low. The puncturing strength is therefore chosen to be inversely proportional to the bit error rate of the information bit and, in addition, bits are selected which contribute little to the cumulative puncturing strength.

This method is then applied iteratively based on the first determined pattern, so that after just a few simulations, a rate adjustment pattern specifically optimized for the respective convolution code can be found. 11 and 12 show different possibilities for puncturing patterns according to the invention, the numbers of the bits to be punctured (the counting starts at 1). The tables are for different numbers of to be transferred

Information bits and different numbers of bits to be transmitted after the rate adjustment are specified.

3 shows an example of the course of the bit error rate for the individual transmitted bits of a data block in

Dependent on their position in the data block for conventional puncturing with a regular puncturing pattern.

2, this course is for an inventive

Dotting with pattern number 33 from FIG. 12, which has been found to be particularly suitable in simulations, is shown. It can be seen from FIG. 2 that by using the puncturing pattern according to the invention, a more uniform course of the bit error rate can be achieved over the entire data block. Since puncturing is less frequent in the middle area of the data block compared to the conventional procedure, a lower probability of error can be obtained there. In fact, the error rate now increases somewhat towards the ends, which at first glance might seem unfavorable. However, this results from the fact that there are a particularly large number of “weak” bits at the edge, as already explained above, where puncturing can be carried out quite cheaply. 4 is the course of the same for the same cases

Total error rate plotted against the ratio of the energy of the transmitted bits to the noise power density. It can be seen from FIG. 4 that with the aid of the invention (lower curve, circles), a frame error rate which is improved by approximately 0.2 dB can be achieved compared to the conventional procedure (upper curve, crosses). Similar improvements can also be achieved with other parameters. For example, FIG. 6 shows the course of the bit error rate for the individual transmitted bits of a data block as a function of their position in the data block for conventional puncturing with a regular puncturing pattern with coding with rate 1/3 and puncturing 8 bits (48) 40 bit). This corresponds to a transmission of 8 input bits. FIG. 10 shows the distribution if, instead, the puncturing pattern No. 3 from FIG. 11 is used, which has also been found to be particularly suitable in simulations. You can see that there is a very balanced distribution here. Here, too, there is an improvement of approx. 0.2dB (however, no curve has been added for this, since it does not bring any further significant findings).

FIG. 16 shows further preferred exemplary embodiments in the context of the invention with a puncturing of 14 out of 54 bits, the patterns 3 and 4 achieving the best results.

Figures 13, 14 and 15 show preferred ones

Repetition patterns that were also obtained using the rules shown in this invention.

The present invention has so far been described in terms of use in a mobile radio transmitter. Of course, the invention can, however, also be extended to mobile radio receivers where a signal punctured or repeated in order to adapt the data rate in the manner described above corresponds to the puncturing or Repetition patterns must be worked up. In this case, additional bits are inserted into the received bit stream in the respective receiver for punctured or repeated bits on the transmission side, or two or more bits of the received bit stream are combined. When additional bits are inserted, this is noted in the form of a so-called 'soft decision' information that their information content is very insecure. The processing of the received signal can take place in the respective receiver in the reverse order to FIG. 1.

Further rate adjustment patterns determined using the procedure explained above

The previously specified puncturing patterns mainly focus on puncturing in the end areas and / or repeating in the middle area.

The further rate adjustment patterns now described were determined using the method explained above for various proposals for HS-SCCH coding in the standardization. The bits to be punctured or repeated are given in each case. The bits are numbered from 1 to N. The preferred pattern is mentioned first, but the other patterns always have similarly favorable properties. FIG. 17, in which these further puncturing patterns are listed, thus represents a supplement to FIG. 12. Correspondingly, puncturing patterns for different output bit rates are shown in FIGS. 18-24 and further repetition patterns in FIG. 25.

Approximation of preferred rate adjustment patterns using components already specified in UMTS.

The patterns shown so far have the aim of proposing the best possible selection of bits to be punctured or repeated, with no other restrictions regarding the patterns being assumed. In practical implementations, however, it can be advantageous to consider only those patterns which can be implemented with the smallest possible changes to existing rate adjustment circuits. A corresponding Rate adjustment rule is in the already mentioned specification 25.212 v5.0.0, Chap. 4.2.7 "Rate matching" is described in the following. The part of this regulation which actually punctures or repeats and is described in Chapter 4.2.7.5 "Rate matching pattern determination" is described accordingly played. Extract from the specification:

Before the rate adjustment, the bits are marked with x _ll , x _l2 , x, ..., x _ιX . Here i represents the transport channel number, the sequence itself is in sections 4.2.7.4 of the specification for the uplink and in 4.2.7.1. defined for the downlink. The uplink is the connection of a communication device to the base station, the downlink is the connection of a base station to a communication device.

The rule for rate adjustment is in the ??? shown program section reproduced, which expires when the condition is met that puncturing is carried out. First an error value e is set to an initial value which lies between the original error value and the desired puncturing rate. In a loop with the index m of the currently considered bit as a running parameter, the

Sequence, i.e. up to the index Xi

First the error value e is set to e - e _m j _.nus , where e _m inus essentially represents the number of bits to be punctured. - It is then checked whether the error value e <= 0

In this case, it is checked whether the bit should be punctured with the index m, a bit to be punctured then being set to a value δ that is different from 0 or 1. In the event that repetition is to take place, an essentially analogous process takes place, in which case a repeated bit is set directly after the original bit. bit

When puncturing, the bits which have been set to the value δ are then removed in the further course, so that these bits are punctured.

The parameters ∑i, eι _n i, e _p ι _US and e _m i _nU s are each selected so that the desired rate adjustment can be achieved. The following then essentially applies: e _p j _us = X, e _m i _nus = N _p , where ∑i denotes the number of bits before the rate adjustment and N _p the number of bits to be punctured or repeated. eι _n i can in principle be chosen arbitrarily in the range between 1 and e _p ι _us , whereby there is a slight shift in the pattern, this is used in certain cases (rate adjustment after a first interleaving (nesting)) to differentiate the pattern Suitable to move the frame against each other. The parameter i identifies different transport channels in the specification. However, this parameter is irrelevant in the present case and is therefore omitted. The following shows how you can use this rate matching algorithm

Rate matching patterns for short block sizes in convolutional codes can approximate. Under the boundary condition of this algorithm, an attempt is made to use bits at the ends of the code block when puncturing, and especially bits from the middle of the code block when repeating. A key aspect of this embodiment is the parameter i ei _{n is} not to be limited to the range of values from 1 to _p e ι _UΞ, but to select instead in an advantageous manner outside this range. At first glance, such a choice may seem contradictory, because then it is no longer ensured that the desired number of bits is punctured or repeated. By an advantageous Adjusting the values of e _p ι _us and e _m inus can, however, be achieved so that the desired number is nevertheless achieved.

It is:

∑i: number of bits before rate matching

N _p : number of bits to be punctured / repeated (the index _p in N _p indicates the number of bits to be punctured, but N _p can also denote the number of bits to be repeated)

In order to specify the use of the rate matching algorithm and thus the rate matching pattern complete, each of the error initial value θi _n i, e _plus the Fehlerinkrement and Fehlerdekrement e _m i _nus must be specified, since these

Parameters fully describe the rate adjustment pattern.

In the following, the approximation of preferred rate adjustment patterns is presented using the algorithm listed in Release 99 UMTS Rate Matching.

In the following, possibilities are shown how preferred rate adaptation patterns for short block sizes for convolutional codes can be approximated by means of the rate matching algorithm (data rate adaptation algorithm) already present in the standard. Under the boundary condition of this algorithm, an attempt is made to use bits at the ends of the code block when puncturing, and especially bits from the middle of the code block when repeating.

dotting

The parameters of the rate matching algorithm are chosen so that the first N ₀ bits are punctured at the beginning of the code block

₀ ^• ™ » ^{" e} _P lus) < ^e ini ≤ ^ 0 ^• «» * ». ^" (# 0 ^"l ) ^'β plus ⁽ 1> Another criterion is that the last bit of the block is also punctured, according to the following condition:

(N ₀ - l) - (e _mam - e _pba ) <e _m (2)

In this case, the value of the error variable e will become negative precisely at the last bit, which means that this bit is then punctured.

Both criteria are e.g. B. fulfilled by the following preferred choice of parameters:

e _pba = X, - N ₀ (3) e _mmus = N _p - N ₀ (4)

These formulas also include the special case that no bit should be punctured at the beginning of the code block (N ₀ = 0). The following then applies: θi _n i = X ±, e _pluε = ∑i, e _m i _nus = N _p .

The general implementations, which choose θi _n i according to formulas (1) to (4), result in rate adjustment patterns which differ from those of the preferred parameter selection

Distinguish (3) to (5) only in that the index of the bit to be punctured can be decreased by one from the (No + l) th to the (N _p - l) th puncturing point.

For the application example of puncturing from 48 bits to 40 bits, the table in FIG. 26 shows puncturing patterns according to the preferred parameter _selection up to No = 6. The puncturing points that are not printed in bold can be _varied by varying the e _ιn i value according to (1) and (2). either partially or completely decreased by one. The table shown below in FIG. 27 shows in the same way the resulting patterns for puncturing from 111 bits to 80 bits.

Although this is not the best

Puncturing patterns, which were already discussed above, can be achieved with this method, a certain improvement in the transmission quality compared to the current state of the specification can be achieved, the changes to be made are comparatively small.

repetition

According to the invention, the parameters of the rate matching algorithm are calculated such that a maximum distance of the last bit to be repeated from the end of the block is guaranteed, so the following must apply: e _m = ^ + X _l - e _mma - N ^' _p ' e _pba . (6) Furthermore, the average distance between bits R _R to be repeated can be specified. R _R need not be an integer, but can be a positive rational number. The following then applies:

D e P ', ^us ^R _R = (7) minus Thus, e _p ι _us and e _mιnus can be freely chosen under the boundary condition that their quotient just results in R _R and a total of N _p bits are repeated.

If the first bit to be repeated, more precisely the position of the first bit to be repeated (here referred to as £> ι), is to be specified, the following must also apply next to (6)

where e _m i _nU s should be an integer and b _x ≤ ∑i - N _p + 1. A preferred _{choice of} parameters gives ^e _nunus = H _p . ⁽ 9 ⁾

'plus = χ. -b, + 1 (10)

im = (b, - l) - N _p + l (ii)

With this choice of parameters, the position of the first bit to be repeated is Ji, and N _p bits are repeated as required.

Again, the resulting repetition patterns are not optimal compared to the patterns already discussed above. Nevertheless, a certain improvement in the transmission quality compared to the current state of the specification can be achieved with this method, the changes to be made again being comparatively small. A good choice of parameter b _\ can ensure that repetition does not start at the beginning. Repetition is not necessary at the beginning, since the bits at the beginning of the convolution decoder already have a comparatively low error rate, as shown above. It is much more useful if the bits to be repeated, as is done by this method, are concentrated more towards the middle. A disadvantage of this exemplary embodiment, however, is that it avoids repetition only at the beginning, while the conditions can be influenced far less positively at the end. This is the price that has to be paid for the simplified implementation.

Of course, a combination of the above criteria is also possible when selecting a puncturing pattern. For example, you can combine a pattern from two patterns presented here, using the beginning of one pattern at the beginning and the end of the second pattern at the end. Furthermore, it is irrelevant if the bits are output in a different order, and at the same time the puncturing pattern is adjusted analogously. For example, the order of the polynomials in the convolutional encoder can be exchanged.

Claims

claims

1. Method for adapting the data rate of a data stream in a communication device, wherein the data stream can be subdivided into at least one data block which contains transmission bits to be transmitted.

- The transmission bits are formed by a coding process from information-carrying input bits, - in which to adapt the data rate from a

Data block of the data stream certain transmission bits are removed (punctured),

a puncturing pattern is used to specify which transmission bits are to be removed, and the puncturing pattern is designed such that preferably transmission bits are removed which depend on a few input bits via the coding process.

2. The method of claim 1, wherein the puncturing pattern is formed by the following steps:

Determination of a cumulative puncturing strength, which indicates which portion of information bits has been removed from the data block by removing transmission bits, formation of a decision function as a function of the cumulative puncturing strength,

- Minimize the decision function to determine the puncturing pattern.

3. The method as claimed in one of the preceding claims, in which the puncturing pattern specifies the spacing between transmission bits to be removed via a puncturing rate, the puncturing rate being different for different areas in the data block.

The method of claim 3, wherein the puncturing rate is substantially in the central area of the data block has equidistant distances between the bits to be removed.

5. The method as claimed in one of the preceding claims, characterized in that the puncturing pattern is designed in such a way that, through the puncturing, viewed from the front end of the data block to be punctured, it contains a section from the following series (bit positions): 1, 4, 2 , 3, 8, 7, 5, 6, 15, 12, 14, 11, 10, 9 where "1" corresponds to the first bit position.

6. The method according to any one of the preceding claims, characterized in that the puncturing pattern is designed in such a way that the puncturing, viewed from the rear end of the data block to be punctured, contains a section from the following series (bit positions): 0, 4, 6 , 1, 2, 15, 12, 10, 9, 7, 4, 5, 18, 13, 8, where "0" corresponds to the last bit position.

7. The method according to any one of the preceding claims, characterized in that the puncturing pattern is designed such that 8 of 48 bits are punctured, namely bits 1, 2, 4, 8, 42, 45, 47, 48.

8. The method according to any one of the preceding claims, characterized in that the puncturing pattern is designed such that 31 of 111 bits are punctured, namely bits 1, 2, 3, 4, 5, 6, 7, 8, 12, 14, 15, 24, 42, 48, 54, 57, 60, 66, 69, 96, 99, 101, 102, 104, 105, 106, 107, 108, 109, 110, 111.

9. The method according to any one of the preceding claims, characterized in that the puncturing pattern is designed such that 14 of 54 bits are punctured, namely bits 1, 2, 3, 4, 7, 8, 36, 39, 42, 48, 51, 52, 53, 54.

10. The method according to any one of the preceding claims 1-8, characterized in that the puncturing pattern is designed such that 14 of 54 bits are punctured, namely bits 1, 2, 3, 4, 6, 7, 8, 39, 45 , 48, 51, 52, 53, 54.

11. Method for adapting the data rate of a data stream in a communication device, wherein the data stream can be subdivided into at least one data block which contains transmission bits to be transmitted.

- The transmission bits are formed by a coding process from information-carrying input bits, - in which to adapt the data rate from one

Data block of the data stream, certain transmission bits are repeated (repeated),

a repetition pattern is used to specify which transmission bits are to be repeated, and the puncturing pattern is designed such that transmission bits are preferably repeated which depend on many input bits via the coding process.

12. The method according to claim 11, wherein the repetition pattern is formed by the following steps:

Determination of a function of a cumulative repetition strength, which indicates

- what proportion of input bits has been repeated by repeating transmission bits in the data block, - formation of a decision function depending on the cumulative repetition strength, - Maximize the decision function to determine the repetition pattern.

13. The method according to any one of the preceding claims 11 or 12, characterized in that the repetition rate of the repetition pattern, which specifies the distance between the bits to be repeated, causes essentially equidistant distances in the central region of the data block and such large distances at the edge of the data block, that no bits are repeated.

14. The method according to any one of the preceding claims 11 to 13, characterized in that the repetition pattern is designed such that 4 of 36 bits are repeated, namely bits 16, 18, 20, 22.

15. The method according to any one of the preceding claims, characterized in that the data block in which the rate adjustment is carried out comprises data encoded with a convolutional code.

16. Communication device with a rate adjustment device (6) for puncturing or repeating a data block of a data stream supplied to the rate adjustment device (6) according to a specific rate adjustment pattern

Adjustment of the data rate of the data stream, the rate adjustment device removing or repeating bits corresponding to the rate adjustment pattern from the data block by puncturing or repetition, characterized in that the rate adjustment device (6) is designed such that it adjusts the rate adjustment with a Dotting pattern or repetition pattern carried out, which is designed according to any one of the preceding claims 1-15.

17. Communication device according to claim 16, characterized in that the communication device (1) is a mobile radio transmission or mobile radio reception device, in particular a UMTS mobile radio transmission or UMTS mobile radio reception device.