WO2006072516A1

WO2006072516A1 - Code sequence and radio station

Info

Publication number: WO2006072516A1
Application number: PCT/EP2005/056432
Authority: WO
Inventors: Bernhard Raaf; Jürgen MICHEL
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-01-10
Filing date: 2005-12-02
Publication date: 2006-07-13
Also published as: DE102005001149A1

Abstract

The invention relates to a code sequence which is described by the lines of a code matrix. The code matrix can be obtained according to the following steps: a hadamard matrix having the length n is formed and gaps of the hadamard matrix are interchanged.

Description

description

Code sequence and radio station

The invention relates to both code sequences and radio stations, in particular mobile stations or base stations, which are set up to use code sequences accordingly.

The rapid technological development in the field of mobile radio communication led in recent years to the development and standardization of the so-called third generation of mobile communications systems, in particular the UMTS (Universal Mobi ^¬ le Telecommunications System), which among other objectives is to strengthen the To provide users of mobile stations, such as mobile phones, increased data rates.

Especially in the last few months, a so-called enhanced-up-link is a focal point of these development and standardization activities. With this Enhanced-Up-Link increased data rates are to be made available for the connection from a mobile station to a base station. For construction or in order to maintain such an enhanced-up link, the Enhanced Up Link Dedicated Channel Hybrid (ARQ Indicator Channel) signaling channels and Enhanced Up Link dedicated Channel Relative Grant Channel (E-RGCH) are provided in the direction from the base station to the mobile station ,

With the E-HICH an "Acknowledge" or an "Emergency

Acknowlegde "signals to the mobile station, depending on whether a packet was received correctly by the base station or not. The E-RGCH signals to the mobile station whether it is allowed to transmit at a higher, equal or lower data rate.

The data, in particular data bits, which are sent via said signaling channels, in particular via the same radio channel, to different mobile stations are spread for subscriber separation with a code sequence, also called a signature sequence.

Since, for example, within the same radio channel various ^¬ dene data to various mobile stations sent, it is necessary to impart the various data corresponding to different code sequences to the mobile stations as to enable to separate the received on this radio channel data from each other and in a mobile station, only the to further process data directed to this mobile station.

During the enhanced uplink channel relates to a data transmission from the mobile station to the base station, describing the mentioned signaling channels, E-HICH and E-RGCH, the rich ^¬ processing of the base station to different mobile stations.

It is now the aim of the global development efforts to provide a set of code sequences or signature sequences that allow an efficient implementation of these said signaling ^¬ channels.

The invention is therefore based on the problem to provide a technical teaching that allows an efficient implementation of said signaling channels. This problem is solved by the features of the independent claims to ^¬. Advantageous and advantageous developments of the invention are defined by the features of the dependent claims.

The invention is based initially on the idea of using code ^sequences which are mutually orthogonal. This has, that a receiver (e.g., a Mobilsta ^¬ tion), which correlates with its code sequence in a received signal sequence, which is not intended for it, is obtained the advantage, in the ideal case, no correlation signal. Therefore, in a first step, the use of code sequences which form the lines of a Hadamard matrix proves to be advantageous, since the lines of a Hadamard matrix are mutually orthogonal.

Hadamard matrices are defined in particular as matrices with size 1 elements whose rows are mutually orthogonal and whose columns are mutually orthogonal. In the context of the application, however, the term "Hadamard matrix" is generally intended to describe all matrices with elements of size 1 whose rows are mutually orthogonal.

However, the invention gave underlying investi ^¬ deviations that the use of the rows of a Hadamard matrix as the code sequence for impressing on data, in particular data ^¬ bits does not result in the application referred to the desired results.

Extensive research and thought led to the realization that frequency errors, in particular the difference between the transmission frequency and the reception frequency due to a Doppler shift, reduce or worsen the orthogonality of the code sequences in practical application. These Reduction or deterioration of the orthogonality of code sequences due to a frequency error just then turned out to be particularly strong out when the Zei ^¬ be used len known as Hadamard code sequences.

An essential aspect of the invention is therefore the recognition to use code sequences for the realization of the above-mentioned signaling channels, the orthogonality of which is as far as possible unimpaired even in the presence of a frequency error. The subject matter of the invention is therefore also a set of code sequences, in particular of length 40, for which it holds that the code sequences are mutually orthogonal and that the maximum of

is minimal, the maximum being formed for all possible pairs s and e, where s is unequal to e, C (s, i) is the element of the code matrix in line s and column i, and the sum is over all the columns of Code matrix is executed.

In the context of the invention is also a code sequence which is described by the line of a code matrix, wherein the code ^¬ matrix is obtainable by the following steps:

Forming a Hadamard matrix of length n;

Swapping columns of the Hadamard matrix.

Consuming simulations showed with specially Create ^¬ for this purpose th simulation tools that code sequences, which are described by the lines of a code matrix thus formed, also preserve at a frequency error their orthogonality with each other as well as possible, and so the mobile stations a good separability of signals based on a Sprei ^¬ tion with such code sequences allow.

A further improvement results from the use of code sequences taken from a code matrix which can be obtained by the following steps:

Numbering of the n columns of the Hadamard matrix from 0 to n-1; - Grouping of the columns in even-numbered columns (0, 2, 4, ... n-2) and in odd-numbered columns (1, 3, 5, ..., n-1);

Swapping the columns of the Hadamard matrix such that the group of even-numbered columns form the first n / 2 columns of the code matrix, and that the group of the

Odd-numbered columns form the last n / 2 columns of the code matrix.

Within the scope of the invention, of course, there are also radio stations, in particular base stations and mobile stations, which are suitably set up to use code sequences according to the invention, in particular for the transmission of the above-mentioned signaling channels. In this case, the data bits to be transmitted via these signaling channels can be multiplied (spread) on the transmitter side for better separability by the code sequences according to the invention. On the receive side, the receiver can correlate a code sequence according to the invention with the received signals for better separation of the received signals, ie. H . Form correlation sums and process them accordingly.

In the following, embodiments of the invention will be described in more detail with reference to figures. Showing: Figure 1 is a simplified representation of an up-link or. Down-link connection;

Figure 2 is a code matrix;

FIG. 3 shows a simulation result.

FIG. 1 shows two (enhanced uplink) data channels EU0 and EU1 from two mobile stations MS0 and MS1 to a base station BS of a UMTS system.

For construction or in order to maintain such an enhanced-up link, the signaling channels E-HICHO and E-HICHl (Enhanced Up Link Dedicated Channel Hybrid ARQ Indicator

Channel) and e-RGCHO and e-RGCHl (Enhanced Up Link Dedicated Channel Relative Grant Channel) provided in the direction of the Ba ^¬ sisstation BS to the mobile stations MSO, MSl.

In order to make the base station BS to the mobile stations MSO, MSl within a radio channel (same time and Frequenzres ^¬ source) realized signaling channels at the receiving end for the various mobile stations MSO, MSl separable, are the transmitting end over these signaling channels to be transmitted data bits ( base station side) ver ^¬ different code sequences imprinted.

Radio stations (mobile stations, base stations) are in terms of hardware or software technology arranged to code sequences according to the invention are used for the transmission of data, in particular data to be transmitted with a ^¬ OF INVENTION to the invention code sequence multiplied (are spread advertising the) or received signals are correlated with a code sequence according to the invention.

For example, a base station transmitting means for transmitting data to various subscribers and a processor device which is set up such that Da ^¬ th, which are directed to different subscribers, various ^¬ dene code sequences are imprinted, wherein the code sequences of a code matrix are taken, which is obtainable by the following steps:

Forming a Hadamard matrix of length n; Swapping columns of the Hadamard matrix.

According to one embodiment variant, the code sequences are taken from a code matrix which can be obtained by the following steps:

Numbering of the n columns of the Hadamard matrix from 0 to n-1;

- Grouping of the columns in even-numbered columns (0, 2, 4, ... n-2) and in odd-numbered columns (1, 3, 5,

-, n-1);

Swapping the columns of the Hadamard matrix such that the group of even-numbered columns is the first n / 2

Form columns of the code matrix, and that the set of odd-numbered columns form the last n / 2 columns of the code matrix.

For example, a mobile station has a receiving ^device for receiving a received signal ^sequence and a processor device which is set up such that the received signal sequence in accordance with one of the named above ge ^¬ code sequences is correlated.

For better separability because of these code sequences should be mutually orthogonal. This means that a receiver (e.g. a mobile station), which correlates to a row (code ^¬ sequence) receives a signal when another row (code sequence) has been sent:

The received signal E is then when the transmitter correlates the sequence (code sequence) and the receiver sends s to the sequence (code ^¬ follow) e:

£ = ΣC (s, i) C (e, /) = 0,

this represents C (s, i) is the i-th element of the transmitting end USAGE ^¬ Deten code sequence represents and C (e, i) is the i-th element of the code sequence receiving side used.

Thus, transmissions for other users based on the code sequence s do not interfere with the transmissions for a given user who expects data based on the code sequence e. However, this perfect orthogonality is lost if the signals have a frequency error. Then:

E = ΣC (s, i) C (e, i) * _e ^{j2πft (ι)} = ΣC (s, i) C (e, i) * e ^j2πfTι ≠ 0 ^<<

Where f denotes the value of the frequency error, t (i) = Ti is the time at which the i-th bit is transmitted, T is the duration of one bit. As usual in signal processing, the calculation is complex. Here, it is assumed that the i-th Sym bol ^¬ is sent once i at time t. Strictly speaking, this is only the case if the bits are transmitted serially in succession. will wear. It is also possible, for example, to transmit two bits in parallel at the same time, for example by using a so-called IQ multiplex method, ie. H . In a complex transmission signal, one bit is transmitted as a real part and the other as an imaginary part. In this case, two bits each are transmitted at the same time, so that t (i) = (int (i / 2) * 2 + 0, 5) * T. int () denotes the integer part here. However, the difference between these two cases is only 0.5T and is generally negligible so that this fineness will not be discussed further below.

Thus, emissions affect each other, d. H . When data is sent to a mobile station based on the code string s, it interferes with the reception at the mobile station which expects data on the basis of the code string e. This disturbance is minimized by the present invention.

It would be optimal if one sets (code matrices) of orthogona ^¬ len sequences (code sequences) could find that even in the presence of a frequency error have good properties. In particular, should the worst case, the Be ^¬ above influencing be as low as possible for the worst pair of sequences. The aim of the invention is therefore also to provide a method for generating such sequences and the use of these sequences for purposes of transmission.

Square matrices with n orthogonal lines are also called Hadamard matrices. The following education law to

Construction of a Hadamard matrix of length 2n n of a matrix of the length generally known and is frequently fixed ^¬ applies: C _n C _n

C _2n = c "-c"

Starting from the Hadamard matrix H2 of length 2, it is possible to generate matrices whose length is a power of two:

In addition, Hadamard matrices of length 20 are known, from which can be generated with this rule matrices of length 40, 80, 160 ....

It now appears, however, that generated this rule Matri ^¬ zen length 2n a particularly bad trait in the presence of frequency errors have d. H . the loss of orthogonality is especially great. The influence on the lines k and n + k (where k <n) is particularly large. This is because two such lines in the first n elements are identical, whereas in the last n elements they have opposite signs. The correlation contribution of the first half is thus rigiert until the second half kor ^¬. However, as the frequency error increases with time, this correction is already comparatively strongly falsified by the already relatively strong influence of the frequency error.

It turns out that with a certain permutation of columns of a Hadamard matrix, the orthogonality properties (without frequency error) do not change, but the column interchange definitely has an influence on the orthogonality properties in the case of frequency errors. They are therefore mierung the orthogonal properties in case of frequency errors suitable column interchanges feasible.

A column interchange, which has proved particularly advantageous in simulations, is the following:

The algorithm is described here for the convention that the columns (not 1) counted starting with 0 to who, but can of course also for other Num merierungskonventionen ^¬ adapt.

From the matrix C2n, one selects the even columns (columns 0, 2, 4, ... 2n-2) and sets them to the columns 0 to n-1. The odd columns (columns 1, 3, 5, ... 2n-l) are placed on the columns n to 2n-l. The order within the straight or Odd columns are retained. Thus one uses the following permutation: 0, 2, 4, 6, ... 2n-4, 2n-4, 1, 3, 5, 7, ... 2n-3, 2n-l.

The just-shown column interchange is equivalent to the following alternative construction principle (by the way, this design principle also leads to an equivalent interchanging of lines.) However, interchanging lines are irrelevant to the problem to be solved.)

A Hadamard matrix of dimension 2n is generated by the fact that one replaces all elements of the Hadamard matrix of dimension 2n by the elementary 2er Hadamard matrix, multiplied ^¬ ed with the value of the element, d. H . you replace in the matrix

1 1 -1 -1

1 through and 1 through

1 -1 -1 1 This gives a matrix with the double dimension.

Particularly advantageous is the following construction ^¬ proved, for a code matrix:

Generation of a Hadamard matrix C20 of length 20 as a so-called Williamson matrix, it can be generated as: A A C D

-C -D A A

^ 20 -AA-C-D-C-A

Whereby A resp. C in each case 5 times 5 matrices are with lines that from the cyclic permutations of the sequences [-1 1 1 1 l] resp. [l -1 1 1 -l] exist, and D = -C II where I is the 5 by 5 matrix represents a ^¬ standardized so that D contains the cyclic mix up ^¬ mixtures of the sequence [l 1 -1 -1 l].

The Williamson matrix is thus the following matrix, with the individual blocks of 5 highlighted:

-1 1 1 1 1 -1 1 1 1 1 1 -1 1 1 -1 1 -1 -1 -1 1 1 -1 1 1 1 1 -1 1 1 1 -1 1 -1 1 1 1 1 1 -1 -1 1 1 -1 1 1 1 1 1 -1 1 1 1 -1 1 -1 1 -1 1 1 1 -1 1 1 1 -1 1 1 1 1 -1 1 1 1 -1 1 -1 -1 -1 - 1 1 1 1 1 1 1 1 -1 1 1 1 1 -1 -1 1 1 -1 1 1 -1 -1 1 1 -1 1 -1 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 1 1 1 1 1 -1 1 -1 -1 -1 -1 -1 1 1 1 -1 1 1 1 1 -1 1 1 1 -1 1 -1 1 -1 1 -1 -1 - 1 1 1 1 -1 1 1 1 1 -1 1 1 -1 -1 1 -1 1 1 1 -1 -1 -1 1 1 1 -1 1 1 1 1 -1 1 1 -1 -1 1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 1 1 1 1 -1 1 -1 -1 -1 -1 -1 1 1 1 1 1 1 -1 -1 1 -1 1 -1 -1 -1 1 -1 1 -1 -1 -1 1 1 -1 1 1 1 1 1 -1 -1 -1 1 -1 1 -1 -1 -1 -1 1 -1 -1 1 1 -1 1 1 -1 1 1 1 1 -1 -1 1 -1 1 -1 -1 -1 -1 1 1 1 1 1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 1 -1 -1 -1 -1 1 1 1 1 1 -1 1 -1 -1 1 1 1 -1 -1 1 -1 -1 -1 1 1 -1 1 -1 1 1 -1 -1 1 -1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 1 1 -1 1 1 -1 1 -1 1 -1 -1 -1 1 -1 1 1 1 1 -1 -1 -1 -1 1 1 -1 1 -1 1 -1 -1 1 -1 -1 1 1 -1 1 1 1 1 -1 -1 -1 1 1 -1 1 -1 -1 -1 -1 1 1 1 1 1 -1 1 -1 1 1 -1 -1 -1 1 1 -1 1 -1 -1 -1 -1 1 1 1 1 1 -1

Generation of a Hadamard matrix of length 40 from this matrix of length 20;

Numbering of the 40 columns of the Hadamard matrix from 0 to 39;

- Grouping of columns in even numbered columns (0, 2, 4, ... 38) and in odd numbered columns (1, 3, 5,

..., 39);

Swapping the columns of the Hadamard matrix such that the group of even-numbered columns is the first 20

Form columns of the code matrix, and that the group of odd-numbered columns form the last 20 columns of the code matrix; Swap columns 12 and 37.

Furthermore, one can perform column interchanges even with the Hadamard matrix of length 20, then generate the 40th Hadamard matrix from them, and then perform further column interchanges on the 40th Hadamard matrix. This has the advantage that you start with a better 20 Hadamard ^¬ matrix, which is also a better 40 Hadamard result has, so that this method more quickly to a good solution results than if you would perform only on the 40 Hadamard column transpositions.

In a computer-aided search, the following column interchanges were found to be particularly favorable:

- On the 20's Hadamard matrix, replace the columns (5, 6), (0, 4), (6, 9), (0, 1)

(Hint: Since the column 0 is exchanged twice, this corresponds to a cyclic permutation of the columns (1, 4, 0), the permutation in relation to the original 20's Hadamard matrix is then (1, 4, 2, 3, 0, 8, 9, 7, 5, 6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19);

Then generate the 40's Hadamard matrix according to one of the above instructions, and then replace the columns (1, 10), (3, 4).

This results in the optimized matrix shown in FIG. The maximum of the sub-correlations in this matrix is 3, 89, which is comparable to the value of the original matrix of 8, 26. This means suppression for receiving broadcasts for other mobile stations of 6, 54dB. Another, even better, optimization is available through the following operations:

- On the 20th Hadamard matrix, replace the columns (6, 9),

(10, 13), (0, 3), (16, 19), (0, 1), (18, 19), (5, 7), (12, 14), (1, 2), (17 , 18)

Then, according to one of the above-mentioned rules, generate the 40th Hadamard matrix, and then exchange the columns (6, 9), (11, 14), (6, 10), (14, 16), (3, 4), (13, 14), (2, 3), (17, 18). The maximum of the minor correlations is with this matrix

3, 7406.

A development of the invention therefore provides the following steps for the formation of a particularly advantageous code matrix:

C and D are Hadamard matrices,

A development of the invention provides the following steps for the formation of a particularly advantageous code matrix:

C and D are Hadamard matrices,

[D _n D _n

form a code matrix according to: D _7n =

C _n . -C _n

These code matrices can be further optimized by the above-mentioned column commutation steps.

FIG. 3 shows the distribution of the correlations for frequency errors, namely for the prior art (UMTS) and the presented method with the optimized column interchange shown above (group even and odd). but de columns), which is equivalent to the process of the g ven alternatively ^¬ generation of the matrix (without the o.. tenertauschungen further cleavage). The frequency error was assumed to be 100 Hz. The size of the cross-correlations is plotted on the y-axis, they are sorted by size. The x-axis thus corresponds to the number of the pair for which the cross-correlation was calculated.

As you can see, according to the state of the art, 40 extra lines with a value greater than 8 are created. After the improvement, the maximum is only approx. 6 and is also rarely reached.

It can be shown that the sum of the squares of all sublines is constant. Therefore lowered the maxima, so inevitably raised the values attached ^¬ for smaller branch lines. But they are essentially the Maxima, the processing capacity, the Leis ^¬ determine the system. This is because an error occurs just when a reception value is corrupted by the interference of the cross-correlation. This is mainly caused by the large secondary maxima, less by the small ones. Thus, the increase of the smaller secondary lines (cross-correlations) is not only inevitable but also harmless.

Claims

claims

1. code sequence beschrie by the line of a code matrix is ben ^¬, wherein the code matrix by the steps of ER- hältlich is:

Forming a Hadamard matrix of length n; Swapping columns of the Hadamard matrix.

2. Code string according to claim 1, wherein the code matrix is obtainable by the following steps:

Numbering of the n columns of the Hadamard matrix from 0 to n-1; - Grouping of the columns in even-numbered columns (0, 2, 4, ... n-2) and in odd-numbered columns (1, 3, 5, -, n-1);

Odd-numbered columns form the last n / 2 columns of the code matrix.

3. A code sequence according to any one of claims 1 or 2, wherein the Hadamard matrix is based on an intermediate Hadamard matrix of length n / 2, and wherein the intermediate Hadamard matrix is based on an exchange of columns from an output Hadamard matrix of length n / 2 ,

4. Code sequence according to one of the preceding claims, wherein n = 40

5. code sequence beschrie by the line of a code matrix is ben ^¬, with the proviso that rows of the code matrix forms a plurality of code sequences that the code sequences are orthogonal to each other, and that the maximum of

is minimal, the maximum being formed for all possible pairs s and e where s is not e,

C (s, i) is the element of the code matrix in line s and column i, the sum being executed over all columns of the code matrix.

6. radio station with a memory device for storing a code sequence according to one of claims 1 to 5.

7. radio station with a processor device for generating a code sequence according to one of claims 1 to 5.

8. radio station, with a processor device which is set up such that a code sequence according to one of claims 1 to 5 is imposed on data to be transmitted.

9. radio station, in particular base station, with a transmitting device for transmitting data to various subscribers, with a processor device which is set up in such a way that data which are directed to different subscribers are impressed on different code sequences, the code paths being gene are taken from one of the code matrices described in any one of claims 1 to 5.

10. A radio station, in particular a mobile station, having a receiving device for receiving a received signal sequence, and having a processor device which is set up such that the received signal sequence is correlated with a code sequence according to one of claims 1 to 5.