CN1640036A

CN1640036A - A method to form orthogonal spread spectrum code groups having inter-group zero correlation window characteristic

Info

Publication number: CN1640036A
Application number: CN03805477.9A
Authority: CN
Inventors: 李道本; 邹永忠; 张永生; 徐绍君; 高岩
Original assignee: Linkair Communications Inc
Current assignee: Linkair Communications Inc
Priority date: 2003-01-31
Filing date: 2003-01-31
Publication date: 2005-07-13
Also published as: AU2003211844A1; WO2004068762A1

Abstract

The invention provides a method to form orthogonal spread spectrum code groups which has inter-group zero correlation window characteristic by building or selecting a set of orthogonal spread spectrum code as orthogonal spread spectrum code group spread radix, then using the said orthogonal spread spectrum code group spread radix to make the orthogonal spread spectrum code group spread core having inter-group [-T,T] non-cycle zero correlation window, here the T is single side non-cycle zero correlation window width T, T>=0; and then getting the inter-group zero correlation window orthogonal spread spectrum code groups by spreading the said orthogonal spread spectrum code groups spread core. Since the correlation characteristic among the sets of formed spread spectrum address codes has zero correlation window, that is the cross correlation functions between the different address codes in the zero correlation window having no side peak, multi address interference (MAI) is eliminated, while even the MAI among the different address codes of the same set exits, the joint detection technique could be used to achieve the optimal receiving.

Description

A method to form orthogonal spread spectrum code groups having inter-group zero correlation window characteristic

Method for generating orthogonal spread spectrum code group with intergroup zero correlation window characteristic

Technical Field

The invention belongs to the technical field of communication, in particular relates to a spread spectrum code coding method in spread spectrum and Code Division Multiple Access (CDMA) technology, and particularly relates to a method for generating an orthogonal spread spectrum code group with an intergroup zero correlation window characteristic. Background

With the increasing popularity of personal communication services and the relative scarcity of radio spectrum resources, people have increasingly high requirements on spectrum utilization in radio communications. Conventional access schemes, such as FDMA (frequency division multiple access) and TDMA (time division multiple access), have become increasingly inadequate for the ever-increasing demands of modern wireless communications due to their inefficient spectrum utilization. The new access method CDMA (code division multiple access) has been recognized as the main access method in the next generation of wireless communication due to its high frequency-Fu utilization.

Criga differs from other access modalities in that: a CDMA system is a soft capacity whose capacity depends on the interference level of the system, and any means that can reduce interference can increase the capacity of the CDMA system. The capacity of other access schemes such as FDMA and TDMA systems is a hard capacity that is determined after the system is set up.

Since CDMA system capacity depends on the interference level of the system, it is critical for a CDMA system how to reduce interference in the system. There are three main types of interference in a CDMA system: one is inter-symbol interference (ISI), two is Multiple Access Interference (MAI), and three is Adjacent Cell Interference (ACI). For intersymbol interference, the intersymbol interference is mainly caused by imperfect autocorrelation of spreading code words, the multiple access interference is mainly caused by imperfect correlation characteristics between user codes in a cell, and the adjacent cell interference is mainly caused by imperfect correlation characteristics between user codes in cells. Designing a code group with good auto-correlation and good cross-correlation properties is critical to CDMA systems. An ideal autocorrelation means that the autocorrelation function is zero at all time offsets except the origin, and an ideal cross-correlation means that the cross-correlation function is zero at all time offsets. However, according to the elch bound, autocorrelation and cross-correlation are a pair of contradictions, and decreasing one necessarily causes an increase in the other, so that a codeword in which autocorrelation and cross-correlation are simultaneously perfect does not exist.

In conventional CDMA systems, a combination of common orthogonal sequences such as Walsh sequences, PN sequences, Gold sequences, etc. is used. The correlation properties of these codewords are not ideal. For example, Walsh sequences remain orthogonal only at the origin, and correlation values other than zero are used because the mobile channel is a multi-path channel in which ISI and MAI are necessarily introduced by the system using the code, which determines that the capacity of the system cannot be 4 inches.

In 1997, the Li Dai professor proposed a new spreading code-complementary zero correlation window code in PCT/CN 00/00028. Assuming that the maximum time dispersion of the channel is Δ, it is desirable that such a codeword guarantees correlation properties within [ - Δ, Δ ]. Systems applying such codewords eliminate ISI and Μ Α Ι, greatly increasing the capacity of the system.

Assuming that the complementary code set is { C, S, l ≦ i ≦ M, the code length of the C portion or S portion is N, the single-side zero correlation window width is Γ, according to the zero correlation window boundary:_M≤ ^{2N + 2T}. Given the code length and the size of the zero window,

T + 1

the maximum number of codes possible has been determined and it is not possible to find more code words.

In order to eliminate the influence of interference, besides directly constructing a zero window code during code word design, another method is to transmit a non-zero window code at a transmitting end and to achieve optimal reception at a receiving end by adopting a joint detection technology. Assuming that there are M code channels in total, and using element modulation, the total detection amount during optimal joint detection is adopted. The complexity of the detection method is exponentially increased along with the number M of users, and when the number M of users is increased, the receiver cannot be used, so that the increase of the system capacity is limited. In order to reduce the complexity of the receiver, some suboptimal joint detection algorithms such as decorrelated multi-user detection, interference cancellation techniques, etc. are used, but these algorithms bring performance loss and the complexity is still large when the number of users is large. Disclosure of Invention

The invention aims to provide a method for generating orthogonal spread spectrum code groups with an intergroup zero correlation window characteristic, which enables the correlation characteristic between the formed groups of spread spectrum multi-address codes to have a 'zero correlation window', namely, the cross-correlation function between the address codes of each group in the zero correlation window has no peak, thereby eliminating the Multiple Access Interference (MAI) between the groups, and even if the Multiple Access Interference (MAI) exists between the address codes in the same group, the optimal receiving can be achieved by utilizing a joint detection technology. The spread spectrum code coding method with the characteristics of the zero correlation windows among the beams not only utilizes the characteristics of the zero correlation windows, but also can utilize joint detection, interference cancellation technology and equalization technology, thereby providing possibility for increasing system capacity. Meanwhile, the invention solves the complexity problem of applying combined detection in the CDMA system.

The technical scheme of the invention is as follows: a method for generating orthogonal spreading code groups having an inter-group zero correlation window characteristic, comprising the steps of:

generating or selecting a group of orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base;

generating the spread base with the orthogonal spread code groups to have the code space [ -7; t ] orthogonal spreading code group spreading kernel of aperiodic zero correlation window, where: the width gamma of the unilateral non-periodic zero correlation window is more than 0, and the spread spectrum code group.

The selecting a group of orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base comprises the following steps: and selecting any group of orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base.

The generating a set of orthogonal spreading codes as an orthogonal spreading code set spreading base comprises: in an arbitrarily selected orthogonal spread spectrum code as an orthogonal spread spectrum code group spreading base, if a given original sequence group is not orthogonal, a new orthogonal sequence group can be formed by inserting a certain number of zero guard intervals or time slots into the given original sequence group, and the new orthogonal sequence group is used as the orthogonal spread spectrum code group spreading base.

The arbitrary set of orthogonal spreading codes may include: wal sh code group, orthogonal complementary code with zero correlation window characteristic.

The spreading base of the orthogonal spreading code group is generated to have a value of [ -7; t ] orthogonal spread spectrum code group spreading core of non-periodic zero correlation window comprises:

if the orthogonal spreading code spread base is greater than or equal to [ -7; Γ ], and Γ is greater than or equal to 0, then the spreading base of the orthogonal spreading code group is used as the spreading kernel of the orthogonal spreading code group;

if the spreading base of the orthogonal spreading code group is less than [ -7; t ], and is greater than or equal to the orthogonal spread code of the aperiodic zero correlation window of 0, can insert a certain amount of zero guard interval or time slot in the said orthogonal spread code group spreading base, new orthogonal spread code group formed from this has greater than or equal to [ -7T ], and is greater than or equal to the aperiodic zero correlation window of 0, then can regard this orthogonal spread code group as the spreading kernel of orthogonal spread code group.

Each code length of the orthogonal spread spectrum code group spreading core is N, and M code words exist in total:

{c_;l.ltoreq.z'. ltoreq.m._n,c_i2,---,c_iN) Represents a first code; the code matrix is: c m χ Ν, each row of the code matrix represents a spreading code word;

Γ is defined as follows:

T_ccw= max (τ) = 0, ,1≤ i, j≤M,i≠ j,0≤ |r|<w)

wherein, the microspheres W represent aperiodic cross-correlation function between the first code and the jth code, r represents time offset, and Γ « ^ represents unilateral aperiodic cross-correlation zero window width;

the width of the single-sided aperiodic zero correlation window of the code group is defined as: t = T_CCW。

The said spreading kernel of the orthogonal spread spectrum code group is extended to generate the orthogonal spread spectrum code group with the inter-group zero correlation window characteristic includes: firstly, selecting an expansion matrix = the expansion matrix

The orthogonal matrix is used, and the correlation characteristic between the codes in the orthogonal spread spectrum code group with the inter-group zero correlation window characteristic generated by expansion can be optimized by selecting a better expansion matrix;

i expresses orthogonal spread spectrum code group with I window closing characteristic'

Wherein "", indicates Kronecker product;

each row of the extension matrix representation is used as a new code word, thus the code word has a total of MK codes, the code length is that the code words are divided into-groups in sequence, thus the total code length can be divided into

M:

a first group: ci g-_l5Ci ^,'-Ά

Second group: c. C₂®g_l5c₂®g₂,---,c₂The M group: c. C_M®g_l5c_M®g^---,c_M®^,_K\

M groups of orthogonal spread spectrum code groups generated after the spreading have an intergroup zero correlation window which is more than or equal to [ Ur ];

the orthogonal spreading code group with the inter-group zero correlation window characteristic is inserted into a certain number of zero guard intervals or time slots, so that a new orthogonal spreading code group is generated, and the inter-group zero correlation window is larger than [ -r, Jr |.

Influence of interference caused if correlation between codewords in a generated group having an inter-group zero correlation window orthogonal spreading code group is ideal; because only the code words between the same code group have interference, the code words in the group can be jointly detected, and the optimal complexity of the joint detection is O (: wherein g is element modulation).

The method comprises the following specific steps:

step 1, generating or selecting a group of orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base; wherein: any group of orthogonal spread spectrum codes can be selected as an orthogonal spread spectrum code group spreading base; the arbitrary set of orthogonal spreading codes may include: walsh code groups, orthogonal complementary code groups with zero correlation window characteristics, and the like; if the given original sequence group is not orthogonal, a certain number of zero guard intervals or time slots can be inserted into the given original sequence group to form a new orthogonal sequence group, and the new orthogonal sequence group is used as an orthogonal spread spectrum code group spreading base;

step 2, generating an orthogonal spread spectrum code group spreading base with [ -7; the orthogonal spread spectrum code group of the aperiodic zero correlation window of the gamma; if the spreading base of the orthogonal spreading code group is greater than or equal to [ -7; t ], and gamma is more than or equal to 0, then the orthogonal spread spectrum code group spreading base is used as the spreading kernel of the orthogonal spread spectrum code group; if the spreading base of the orthogonal spreading code group is less than [ -7; gamma ], and is greater than or equal to the orthogonal spread spectrum code group of the aperiodic zero correlation window of 0, can insert a certain number of zero guard interval or time slot into the said orthogonal spread spectrum code group spreading base, thus form and have greater than or equal to [ -7; gamma ] is more than or equal to 0, and the orthogonal spread spectrum code group of the aperiodic zero correlation window can be used as an orthogonal spread spectrum code group expansion core; let each code length of the said orthogonal spread spectrum code group spreading core be Ν, there are a total of m such code words:

{_C/},1<<where C, = (, · C J) represents the ith code, the code matrix is C, each row of the code matrix represents a spreading code word;

The unilateral aperiodic zero correlation window width Γ is defined as follows:

T_ccw= max{ | ¾ (τ) = 0, ,1<i, j≤M,i≠ j,0≤ \τ\≤ w\，

wherein, represents the non-periodic cross-correlation function between ί th code and j' th code, r represents the time offset, r represents_CCTRepresenting the width of a single-sided aperiodic cross-correlation zero window; the width of the single-sided aperiodic zero correlation window of the code group is defined as: t = T_CCW；

Step 3, expanding the core of the orthogonal spread spectrum code group to generate an orthogonal spread spectrum code group with the inter-group zero correlation window characteristic; wherein: firstly, selecting an expansion matrix, wherein the expansion matrix

The orthogonal matrix is used, and the correlation characteristic between the codes in the orthogonal frequency code group with the inter-group zero correlation window characteristic generated by expansion can be optimized by selecting a better expansion matrix; frequency code group:

wherein "" represents the Kronecker product;

each row of the extension matrix representation is used as a new code word, namely, a total of MK codes with the code length of NJ, and the code words are sequentially divided into-groups, so that the total code word can be divided into

And M groups:

a first group: c! g_l5C_x®g₂,---,C_x®g_K]

Second group: c. C₂®g_l5c₂®g₂,---,c₂The second group: c g and C ^ g₂,---,c ®g^;

M groups of orthogonal spread spectrum code groups generated after spreading have intergroup zero correlation windows which are larger than or equal to gamma and gamma;

inserting the orthogonal spread spectrum code group with the intergroup zero correlation window characteristic into a certain number of zero guard intervals or time slots, so as to generate a new orthogonal spread spectrum code group with an intergroup zero correlation window larger than < - >, Γ >;

if the correlation characteristics among the code words in the generated group with the orthogonal spread spectrum code groups with the inter-symbol zero correlation windows are not ideal, the influence of interference caused by the imperfect correlation characteristics among the code words in the group can be eliminated by adopting joint detection; because only the code words between the same code group have interference, the code words in the group can be jointly detected, and the optimal complexity of the joint detection is cq^K) Wherein, the element modulation is.

The invention has the advantages that the method for generating the orthogonal spread spectrum code group with the interclass zero correlation window characteristic is provided, so that the formed correlation characteristic between the groups of the spread spectrum multi-address codes has a 'zero correlation window', namely, the cross correlation function between the address codes in the zero correlation window has no peak, thereby eliminating the Multiple Access Interference (MAI) between the groups, and even if the Multiple Access Interference (MAI) exists between the address codes in the same group, the optimal receiving can be achieved by utilizing the joint detection technology. The new code of the spread spectrum code with the zero correlation window characteristics of the components not only utilizes the zero correlation window characteristics, but also utilizes the joint detection, interference cancellation technology and equalization technology, thus providing possibility for increasing the system capacity. Meanwhile, the invention solves the complexity problem of applying the joint detection in the traditional CDMA system.

Drawings

FIG. 1 is a diagram illustrating the single-sided aperiodic zero correlation window characteristic of the spreading base of the triple orthogonal spreading code set according to the embodiment; fig. 2 is a characteristic diagram of a single-sided aperiodic zero correlation window of the generated orthogonal spreading code block after the triple spreading according to the embodiment;

fig. 3 is a non-periodic correlation curve among the first group of inner codes of the generated orthogonal spread codes after the three spreading of the embodiment;

fig. 4 is a non-periodic cross-correlation curve between the first and second groups of codes of the generated orthogonal spread spectrum code-group code word after the third spreading of the embodiment;

FIG. 5 is a graph of aperiodic cross-correlation between the first and third groups of codes of the generated orthogonal spreading code group code word after the third spreading according to the embodiment;

fig. 6 is a non-periodic cross-correlation curve between the first and fifth groups of codes of the generated orthogonal spreading codes after the third spreading of the embodiment;

fig. 7 is a non-periodic cross-correlation curve between the first and ninth groups of codes of the generated orthogonal spreading codes after the three spreading according to the embodiment.

Fig. 8 is a characteristic diagram of a single-sided aperiodic zero correlation window of a new orthogonal spreading code group obtained by inserting zero guard slots or intervals into a generated orthogonal spreading code group after triple spreading according to the embodiment;

Detailed Description

The present invention will be described in detail below with reference to examples and the accompanying drawings. The first embodiment is as follows:

the first step, selecting the following four orthogonal spread spectrum codes as the spreading base of the orthogonal spread spectrum code group:

wherein "+" represents the number +1 and "-" represents the number-1, which is the same as the above.

Secondly, generating the orthogonal spread spectrum code group spreading base into an orthogonal spread spectrum code group spreading core with [ - ], (2 unilateral aperiodic zero correlation window width) aperiodic zero correlation window:

since the above-mentioned orthogonal spreading code group spreading base only has the non-periodic zero correlation window width of zero, we can insert the above-mentioned orthogonal spreading code group spreading base into the zero guard interval or time slot in the following way, thereby forming the spreading code group spreading base with [ - Λ ])]The following orthogonal spreading code groups of the aperiodic zero correlation window of (1),then we can use this orthogonal spreading code group as the spreading core of the orthogonal spreading code group.

Thirdly, the orthogonal spread spectrum code group is subjected to core expansion to generate an orthogonal spread spectrum code group with the inter-group zero correlation window characteristic, and the specific process is as follows:

first, a spreading matrix such as 4x 4 Wal sh orthogonal spreading matrix is selected

Then, a new orthogonal spread code with the inter-group zero correlation window characteristic is generated by the following spreading method: + + + ++++++++++++++++ ooo +++++++++++++++++++++

+-+-+-+-+-+--+-+ oooo +-+--+-++-+-+-+-

++--++--++ ++ oooo ++ ++++——++—_

+——++——++—— +—++_ oooo +--+-++-+--++--+

+ + + + + + + + + + + + 0000 + + + +

+ - + - + - + -- + - + + - + - 0000 +- + -- + - + - + - + - + - +

+ + -- + + + + + + -- 0000 + + + + -- + + -- + +

+ -- + + -- + - + + - + -- + 0000 + -- + - + + -- + + -- + + -

+ + + + + + + + + + + + 0000 + + + + + + + + + + + +

+ - + --+ - + + - + - + - + - 0000 +- + - + - + - + - + -- + - +

+ + + + + + + -, - -0000 + + - -, - + + +++ -, - + Egger +++

+ -- + - + + - + -- + + -- + 0000 +-- + + -- + + -- + - + + -

+ + + + 0000 + + + + + + + + + + + +

+ - + -- + - + - + - + - + -+ 0000 +- + - + - + -- + - + + - + -

+ + + + -- + + -- + + 0000 + + -- + + + + + + --

According to the method, 16 36-bit-long code words can be obtained, and can be divided into 4 groups, wherein each group comprises 4 code words, and the four groups can be verified to have a non-periodic zero correlation window of [ -4, 4 ].

Example two:

we first choose the following four orthogonal complementary codes with the length of 4 of the C code and S code of PCT/CN00/00028 as the spreading base of the orthogonal spreading code set:

it should be noted that, for the orthogonal complementary codes in the present embodiment, when performing correlation or matched filtering operation, the C code only operates with the C code, the S code only operates with the S code, and the C code and the S code do not meet each other during operation.

The orthogonal spread spectrum code group spreading base has 1 and (1 single-side aperiodic zero correlation window width) aperiodic zero correlation window.

Secondly, since the orthogonal spread spectrum code group spreading base itself has [ - Λ J ], < lambda > single-sided aperiodic zero correlation window width) aperiodic zero correlation window, we directly use the above orthogonal spread spectrum code group spreading base as the orthogonal spread spectrum code group spreading core with [ -, U > single-sided aperiodic zero correlation window width) aperiodic zero correlation window: +

+

Thirdly, the orthogonal spread spectrum code group is subjected to core expansion to generate an orthogonal spread spectrum code group with the characteristics of a zero correlation window among orthogonal spread spectrum code group groups of a unilateral non-periodic zero correlation window width) non-periodic zero correlation window, and the specific process is as follows:

first, a spreading matrix, such as a 2 x 2 Walsh orthogonal spreading matrix, is selected

+ +

G 2x2

+1

Then, a new orthogonal spreading code group with the inter-group zero correlation window characteristic is generated by the following spreading method:

+ + + + -- + +, + + -

+ - + -- + + -, +—— + - + - +

++++++-- + + - - + + + +

+ -- + + - + - c ■■■·： ——++++++， - + + --

- ++ - + - + -, one + - + - ++ - +

--++ ， + +

The method described above can obtain 8 16-bit codewords, which can be divided into 4 groups of 2 codewords, and the four groups of groups can be verified to have a zero correlation window of [ -2, 2 ].

The first table shows the correlation function values of the 8 codes, and the first table shows that a zero correlation window exists in the vicinity of the origin of the cross correlation function among the spread spectrum address codes of each group after spreading, the width of the window is greater than or equal to 5, and the autocorrelation function of each spread spectrum address code after spreading is zero at other places except the origin and the relative shift tau is 1 and-1 in the zero correlation window among the groups; the cross-correlation function of two spreading address codes in the same group is not zero only at two relative shifts τ of 1 and-1, and zero elsewhere, within the above-mentioned intergroup zero-correlation window. Table one: complementary correlation function table (each code length is 2)³=8)

(Cl， SI) = ( + + + + + + + - )；

(C2, S2) = ( + - +—— + + ―， + + - + -+)；

(C3， S3) = (+ + + + + + - ―， + + - - + + + +)；

(C4， S4) = (+- + - + - - +， + + + - + - )；

(C5, S5) = (— + + +++++, - - + + one);

(C6, S6) = (++++ - + one, - ++ - +);

(C7, S7) = (— + + -one, ++);

(C8， S8) = ( - + +—— + ― ― + - + - + + - )；

correlation noodle value ~^T-3 -2 - 1 0 1 2 3

R,(t) = R_CI(T) + R_SI(T) 0 0 8 16 8 0 0

R₂(T) = R_Ci(T) + R_S2(T) 0 0 -8 16 -8 0 0

0 0 8 16 8 0 0

R (T) = R_C(T) + R_S4(T) 0 0 -8 16 -8 0 0 i?₅(r) = i?_C5(r) + i?_S5(r) 0 0 8 16 8 0 0

R₆(T) = R_C6(T) + R_S6(T) 0 0 -8 16 -8 0 0

R₇( ) = R_Ci( ) + R_SiW 0 0 8 16 8 0 0

]R,{T) = R_Cs(T) + R_Ss(T) 0 0 -8 16 -8 0 0

0 0 8 0 -8 0 0

0 0 0 0 0 0 0

R₁₅(r) = R_ClC5(r) + R_SIS5(T) 4 0 0 0 0 0 4

-4 0 0 0 0 0 4

4 0 0 0 0 0 -4ει

H000/C001N3/X3d Z9.890/1-00J Λ \ inserts the above orthogonal spreading code group with the inter-group [ -2, 2] zero correlation window characteristic into a zero guard interval or time slot in the following way, and thus forms a new orthogonal spreading code group as follows:

the 8 20-bit code words can be obtained by the method, and can be divided into 4 groups, each group is 2 code words, and the zero correlation window with [ -3, 3] between the four groups can be verified.

The second table shows the correlation function values of the 8 complementary codes, and it can be seen from the second table that a zero correlation window exists in the vicinity of the origin of the cross-correlation function among the extended groups of spreading address codes, and the width of the window is greater than or equal to 7; the cross-correlation function of two spreading address codes within the same group is not zero within the above-mentioned intergroup zero-correlation window only at two relative shifts τ of 1 and-1, and is zero elsewhere.

TABLE II complementary correlation function table

(C1, S1) = (+ + + + 0 - - + + 0 , + + - - 0 0 )；

(C2, S2) = ( + - + - 0 - + + - 0 , +—— + 0 - + - + 0 )；

(C3, S3) = (+ + + + 0 + + - - 0 , + + - - 0 + + + + 0 )；

(C4, S4) = (+ - + - 0 + - - + 0 , +—— + 0 + - + - 0 )；

(C5, S5) = (— +++ 0, one 0 ++ -0);

(C6， S6) = (- + + - 0 + -+ - 0 ， - + - - + 0 + - - + 0 )；

(C7, S7) = ( - - + + 0 0， - - 0 - - + + 0 )；

(C8， S8) = (- + + - 0 - + - + 0 , - + - + 0 — + +— 0 );

+. A relative shift τ

Correlation function values-3-2-10123 i?_Ci(r) + i?_Si(r) 0 0 8 16 8 0 0

R₂(T) = R_C2(T) + R_S2(T) 0 0 -8 16 -8 0 0

0 0 8 16 8 0 0

R₄(T)^R_C4(T) + R_S4(T) 0 0 -8 16 -8 0 0

R₅(T) = R_C5(T) + R T) 0 0 8 16 8 0 0

0 0 -8 16 -8 0 0

R₇(T) = R_Ci(T) + R_S7(T) 0 0 8 16 8 0 0

R_s(T) = R_Cs(T) + R_Ss(T) 0 0 -8 16 -8 0 0

R_N(T) = R_CiC2(r) + R_S>H(T) 0 0 8 0 -8 0 0

R_U(T) = R_CTC3(T + R_SISI(T) 0 0 0 0 0 0 0

R ( ) = R_CiCi(r) + R_SISI(T) 0 0 0 0 0 0 0

R₁₅(r) = R_CLC5(T)₊R_SiS5(r) 0 0 0 0 0 0 0

0 0 0 0 0 0 0

R₂₅(T) = R_CiCs(T) + R_SiS5(T)

0 0 0 0 0 0 0

R₃₄(r) = R_C}Ci(v) + R_S}S4(T) 0 0 8 0 -8 0 0

0 0 0 0 0 0 00 0 0 0 0 0 0

0 0 0 0 0 0 0

R₇^) = R_C4C,(T)+R_SSi(T) 0 0 0 0 0 0 0

R_4S(r) = R_CICS(T) + R_sr) ' 0 0 0 0 0 0 0

0 0 8 0 -8 0 0

0 0 0 0 0 0 0

R_5S(r) = R_C5CA(T)+R_SSSS(T) 0 0 0 0 0 0 0

R₆₇( )-R_C6) + R_S6Si(r) 0 0 0 0 0 0 0

R_6S(r) = R_C^(T) + R_SeSs(r) 0 0 0 0 0 0 0

R_ls(r) = R_CICS(T) + R_5≠S(T) 0080-800 example III: we first choose the following 16 orthogonal complementary codes with C code and S code length of PCT/CN00/00028 as the spreading base of the orthogonal spreading code set:

The orthogonal spread spectrum code group spreading base has [ - Λ 1], (1 ^ single side aperiodic zero correlation window width) aperiodic zero correlation window.

The single-sided aperiodic zero correlation characteristic of the spreading base of the orthogonal spreading code group is shown in fig. 1.

Second, since the orthogonal spreading code set spreading base itself has [ - _____________________ then]And (J ^ single-side aperiodic zero correlation window width) aperiodic zero correlation window, so we directly use the above-mentioned orthogonal spreading code group spreading base as the orthogonal spreading code group spreading kernel with [ - Λ, ^ single-side aperiodic zero correlation window width) aperiodic zero correlation window:

thirdly, the orthogonal spread spectrum code group is spread and kernel is spread to generate a code with [ -4 ]]And 4, the width of the unilateral aperiodic zero correlation window) aperiodic zero correlation window, and the specific process of the orthogonal spread spectrum code group with the characteristic of the zero correlation window among the orthogonal frequency code groups of the aperiodic zero correlation window is as follows: firstly, a 4x 4 orthogonal spreading matrix G is selected_4x4=

^C16x32 ®^G4x4

wherein "" represents the Kronecker product;

each row of the spreading matrix representation is treated as a new codeword such that there are 64 such codewords, the code length is 128, the codewords are grouped into groups of 4 in order, such that a total of 16: group 1: c. C₁®g₁,c₁®_g2，c₁®g₃,c₁®_g4

Group 2: c. C₂®_gl,c₂®g₂,c₂®g3₅c₂®g₄Group 16: (:₁₆®_§1，(:₁₆®₈₂,(:₁₆®_§3,(;₁₆®_§4

the 16 orthogonal frequency code groups generated after the expansion have an intergroup zero correlation window which is greater than or equal to [ -4, 4 ].

The one-sided aperiodic zero correlation characteristic among the 16 orthogonal spread code groups generated after the spreading is shown in fig. 2.

Fig. 3 shows the correlation characteristics of the extended codes, and we show only the correlation curves of the first code with other codes, which have similar properties.

(1) And the characteristics in the group:

it can be seen from FIG. 3 that the correlation value of the codes in the group is [ -4, 4 [ -4 [ ]]The maximum side peak has a modulus of 0.75 and the correlation is exactly the same as that of the spreading matrix. That is, the correlation characteristics of the codes in the group are mainly determined by the spreading matrix. For code word_Cl®_glOnly the code word generating interference_Cl® g_15Cl® g₂,_Cl® g₃,_Cl® g₄But we can use joint detection to eliminate the interference between them for optimal reception. Because the correlation characteristic of the codes in the group is mainly determined by the spreading matrix, the good code word improves the performance of the joint detection.

(2) Cross-correlation of the first set with the second set:

the first and second sets of correlation windows are [ -63, 63] as shown in fig. 4.

(3) The cross-correlation of the first group and the third group:

the first and third sets of correlation windows are [ -28, 28) as shown in fig. 5.

(4) Cross-correlation of the first and fifth sets:

the first and fifth sets of interdependent windows are [ -12, 12] as shown in fig. 6.

(5) Cross-correlation of the first and ninth sets:

the first and ninth sets of correlation windows are [ -4, 4] as shown in fig. 7. From the above curve, it can be seen that the zero correlation window characteristic still exists between different groups of code words after the expansion, and the width of the zero correlation window is expanded to 4 times of the original width on the original basis. Summarizing the above results, we can see that the correlation of the code word after spreading is determined by the correlation characteristics of the spreading core of the orthogonal spreading code group and the characteristics of the spreading matrix.

Since the correlation characteristic 22 in the group is mainly determined by the spreading matrix, we need to find a spreading matrix with better correlation in order to P strive for the largest secondary peak of the correlation in the group.

Let G_4x4 ⁼[g/_c/]_4x4=

.2π Απ

(1) When e^J,e^ό _?β⁰When the orthogonal matrix minimizes the maximum secondary peak

X,

x₃= e^J0,x₄= e^J0The mode of the maximum secondary peak at this time was 0.5,

the correlation curve within the code set generated using this spreading matrix is shown in fig. 13.

(2) When in_e{ l, -1,' }, orthogonal matrix makes the largest secondary peak the smallest:

-j, c ^ -1, two 1, 4⁼1, the maximum secondary peak modulus at this time. If we have [ -4, 4] for the 16 sets generated after the above expansion]The orthogonal spread spectrum code group of the intergroup zero correlation window is inserted according to the following zero guard interval or time slot: inserting 1 zero at the tail of every 8 chips (Chip), and the inter-group zero correlation window width of the formed new orthogonal spread spectrum code group is [ -5, 5]。

The single-sided aperiodic zero correlation characteristic between the new 16 orthogonal wide-frequency code groups generated after inserting the zero guard interval or time slot is shown in fig. 8. The generation process of the orthogonal spreading code group with the inter-group zero correlation window characteristic of the present invention is described as follows: firstly, generating or selecting a piece of orthogonal spread spectrum code as the spreading base of the orthogonal spread spectrum code: any orthogonal spread spectrum code can be used as the spreading base of the orthogonal spread spectrum code group, for example, the spreading base of the orthogonal complementary code group orthogonal spread spectrum code group with zero correlation window characteristic in PCT/CN00/00028 of the present teaching of Landolt can be selected; if the given original sequence group is not orthogonal, a new orthogonal sequence group is formed by inserting a certain number of zero guard intervals or time slots into the given original sequence group, and the new orthogonal sequence group is used as an orthogonal spreading code group spreading base.

Second, the spread base of the orthogonal spread spectrum code group is generated to have [ -7 r ]](7 ^ single-sided aperiodic zero correlation window width_ΓΓ≥0) And (3) an orthogonal spread spectrum code group spreading core of the aperiodic zero correlation window: if the spreading base of the orthogonal spreading code group is greater than or equal to [ -7; gamma-shaped]The Gamma is not less than 0, and the orthogonal spread spectrum code group of the non-periodic zero correlation window, so that the orthogonal spread spectrum code group expansion base can be used as an orthogonal spread spectrum code group expansion core; otherwise, we can use the above orthogonal spreading codesThe group extension base is formed by inserting a certain number of zero guard intervals or time slots, thereby forming a channel having a length greater than or equal to [ -T [ ]_?Τ]And gamma is more than or equal to 0, namely the orthogonal spread spectrum code group of the aperiodic zero correlation window, so that the orthogonal spread spectrum code group can be used as an orthogonal spread spectrum code group spreading kernel.

Let each code length of the spreading kernel of the orthogonal spreading code group be N, there are M such codes in total

' < ΐ < M, wherein c, = (c)_fl,¾,···, c_iN) Represents the ith code; the code matrix is: each row of the C m χ Ν code matrix represents a spreading code word;

T_ccw= max{ ?_iy(r) = 0, ,1<i, j≤M,i≠ j,0≤ \τ\≤ w)

wherein the time offset, r, represents the aperiodic cross-correlation function between the first code and the second code_CCTy represents the width of a single-side aperiodic cross-correlation zero window;

the width of the single-sided aperiodic zero correlation window of the code group is defined as:

t = t, ccw the third step,

the orthogonal spread spectrum code group is prepared by selecting a spreading matrix, wherein the spreading matrix is selected

The orthogonal matrix or the non-orthogonal matrix can be adopted, and the correlation characteristic among the codes in the orthogonal spread spectrum code group with the inter-group zero correlation window characteristic generated by the expansion can be optimized by selecting a better expansion matrix;

wherein "", indicates Kronecker product;

taking each row of the extension matrix representation as a new code word, so that there are a total of MK code words, the code length is such that the code words are sequentially divided into groups each, so that the total can be divided into M groups:

a first group: c. C_x®g^ c_x®g₂,--,c_x®g_K

Second group: c. C₂®g_l5c₂®g₂,---,c₂®g^ΖΓ]Inter-group zero correlation window of (1). Zero guard interval or slot of a quantity, the new orthogonal spreading code group thus formed having a length greater than [ - Γ, Γ [ - Γ [ ]]Inter-group zero correlation window of (1). For example, a certain number of zero guard intervals or time slots may be periodically inserted into the orthogonal spreading code groups with the above-mentioned zero correlation window characteristics, so that the width of the zero correlation window of the orthogonal spreading code group with the new zero correlation window characteristics is greater than that of the original orthogonal spreading code group.

The above specific embodiments are merely illustrative of the present invention and are not intended to limit the present invention.

If the correlation properties between codewords in the group with the interclass zero correlation window orthogonal spreading code group are not ideal, then we can use joint detection to eliminate the effect of interference caused by the non-ideal correlation properties between the codewords in the group: because only code words between the same code group have interference, the code words in the group can be jointly detected, and the optimal complexity of joint detection is

0(q^K) Wherein g is element modulation;

the invention provides a method for generating orthogonal spread spectrum code group with intergroup zero correlation window characteristic,

the Tianiff 'f ^' zero correlation window, i.e. the correlation function and cross correlation function between each group of address codes in the zero correlation window have no peak-load, thereby eliminating the Multiple Access Interference (MAI) between groups, and even if the Multiple Access Interference (MAI) exists between each address code in the same group, the optimal receiving can be achieved by using the joint detection technology. Because the correlation characteristic of the intergroup zero correlation window code in the group is not ideal, the influence of interference can be eliminated only by carrying out joint detection, but only by carrying out joint detection on the codes in the group, if g-ary modulation is adopted, the detection quantity of the optimal joint detection is only O (^), and because a smaller value is generally adopted, the complexity is greatly reduced. The new orthogonal spread spectrum code group with the characteristics of the intergroup zero correlation window not only utilizes the characteristics of the zero correlation window, but also can utilize joint detection, interference cancellation technology and equalization technology, thereby providing possibility for increasing the system capacity. Meanwhile, the invention solves the complexity problem of applying combined detection in the traditional CDMA system.

Claims

Claims to follow

1. A method for generating orthogonal spreading code groups having an inter-group zero correlation window characteristic, comprising the steps of:

generating a group of orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base;

generating the spreading base of the orthogonal spreading code group to have [ -7; t is]The spreading core of the orthogonal spreading code group of the aperiodic zero correlation window, where: 7¹The unilateral non-periodic zero correlation window width gamma is not less than theta, and the spread spectrum code group.
2. The method of claim 1, wherein a zero guard interval or a time slot can be inserted into the orthogonal spreading code group spreading base.
3. The method of claim 1, wherein a zero guard interval or a time slot can be inserted into the orthogonal spreading code group spreading core.
4. The method of claim 1, wherein zero guard intervals or time slots can be inserted into the orthogonal spreading address codes.
5. The method of claim 1, wherein selecting a set of orthogonal spreading codes as the spreading bases of orthogonal spreading code groups comprises selecting any set of orthogonal spreading codes as the spreading bases of orthogonal spreading code groups.
6. The method of claim 5, wherein the arbitrary set of orthogonal spreading codes comprises: wa l sh code group, orthogonal complementary code group with zero correlation window characteristic.
7. The method of claim 5, wherein generating the set of orthogonal spreading codes comprises: if the given original sequence group is not orthogonal, a certain number of zero guard intervals or time slots can be inserted into the given original sequence group to form a new orthogonal sequence group which is used as an orthogonal spreading code group spreading base; if a given original sequence set is orthogonal, the given original sequence set can be used as a spreading base of a forward spreading code set.
8. The method of claim 1, wherein the generating the orthogonal frequency code set spreading base has [ -7; t ] orthogonal spread spectrum code group spreading core of non-periodic zero correlation window comprises: if the spreading base of the orthogonal spreading code group is greater than or equal to [ -7; is and

the gamma is more than or equal to 0, and the orthogonal spread spectrum code group of the non-periodic zero correlation window, the spreading base of the orthogonal spread spectrum code group is used as the spreading kernel of the orthogonal spread spectrum code group;

if the spreading base of the orthogonal spreading code group is less than [ -7; τ ], and r is greater than or equal to o, the spreading base of the orthogonal spreading code group can be formed by inserting a certain number of zero guard intervals or time slots, thereby forming a code group with a non-periodic zero correlation window greater than or equal to [ -7; 7 Ί, and J is greater than or equal to 0, then the orthogonal spread code group can be used as the spreading core of the orthogonal spread code group.
9. The method of claim 8 wherein each code length of said orthogonal spreading code group spreading core is N, and there are a total of M such code words:

{ ≦ ί ≦ m, wherein_C;= ( ,¾,···, c_iN) Represents the ith code; the code matrix is: c MxN, where each row of the code matrix represents a spreading code;

the unilateral aperiodic zero correlation window width r is defined as follows:

T_ccw= max^ | ¾ (τ) = 0, ,1<i, j≤M,i≠ j,0≤ \τ\≤ w\

wherein the microspheres W represent the aperiodic cross-correlation function between the ζ -th and the jth' codes, r representing the time offset: t is_CORepresents the aperiodic cross-correlation zero window width;

the aperiodic zero correlation window width of the code group is defined as: t = T_CCW。
10. The method of claim 1, wherein the spreading the kernel of the set of orthogonal spreading codes to generate the set of orthogonal frequency codes with the inter-set zero correlation window characteristic comprises: firstly, selecting an expansion matrix, wherein the expansion matrixIs an orthogonal matrix, and can optimize the extended generator by selecting a better extended matrixThen, the new orthogonal spreading code group with the inter-group zero correlation window characteristic is generated by the following spreading method:

wherein "" represents the Kronecker product;

each row of the extension matrix representation is used as a new code word, thus the code word has a total of MK codes, the code length is that the code words are divided into-groups in sequence, thus the total code length can be divided into

And M groups:

a first group:_Cl®_gl, c₁®g₂,---,c₁®g_A.;

second group: tgig c₂®g₂,-",c₂®g_AThe M group: tile_gl, c ®g₂,---,c_M®g_A.;

M groups of orthogonal spread codes generated after spreading have intergroup zero correlation windows which are more than or equal to [ the number of F, F ];

inserting a certain number of zero guard intervals or time slots into the orthogonal spread spectrum code group with the characteristics of the zero correlation windows among the beams to generate a new orthogonal spread spectrum code group with the characteristics more than or equal to that of the orthogonal spread spectrum code group

-inter-group zero correlation window of [ -Jr, r ].
11. The method of claim 10, wherein if the correlation between the codewords in the generated orthogonal spreading code group with the interclass zero correlation window is not ideal, joint correlation is used
The effect of the induced interference; because only the code words between the same code group have interference, the code words in the group can be jointly detected, and the optimal complexity of joint detection is O), which is element modulation.
12. The method of claim 1, comprising the steps of 1, selecting a set of orthogonal spreading codes as spreading bases of orthogonal spreading code sets; wherein: selecting any one of the orthogonal spread spectrum codes as an orthogonal spread spectrum code group spreading base; the arbitrary set of orthogonal spreading codes may include: walsh code groups, orthogonal complementary code groups with zero correlation window characteristics, and the like; if the given original sequence group is not orthogonal, a certain number of zero guard intervals or time slots can be inserted into the given original sequence group to form a new orthogonal sequence group, and the new orthogonal sequence group is used as an orthogonal spreading code group spreading base; if the given original sequence group is orthogonal, the given original sequence group can be used as an orthogonal spread spectrum code group spreading base; step 2, generating an orthogonal spread spectrum code group spreading base with [ -7; the orthogonal spread spectrum code group of the aperiodic zero correlation window of the gamma; if the spreading base of the orthogonal spreading code group is greater than or equal to [ -7; t ], and 7 is more than or equal to 0, then the orthogonal spread spectrum code group spreading base is used as the spreading core of the orthogonal spread spectrum code group; if the spreading base of the orthogonal spreading code group is less than [ -; t3, and 7 ≧ 0, by inserting a certain number of zero guard intervals or time slots into the orthogonal spreading code group spreading base, thereby forming a spread code group with a non-periodic zero correlation window greater than or equal to [ -7; t ], and 7 is more than or equal to the orthogonal spread spectrum code group of the aperiodic zero correlation window of 0, then the orthogonal spread spectrum code group can be used as the spreading kernel of the orthogonal spread spectrum code group; assuming that the code length of each code of the orthogonal spread spectrum code group spreading kernel is N, there are M such code words:

represents a first code;

each row of the code matrix represents a spreading code word;

the unilateral aperiodic zero correlation window width Γ is defined as follows:

wherein the microspheres (r) represent aperiodic cross-correlation functions between the first code and the _/code, r represents time offset, and ^ represents aperiodic cross-correlation zero-window width; the aperiodic zero correlation window width of the code group is defined as: t = T_CCW；

Step (ii) of³Expanding the core of the orthogonal spread spectrum code group to generate an orthogonal spread spectrum code group with the inter-group zero correlation window characteristic; wherein: first, a spreading matrix is generated or selected

The spreading matrix is an orthogonal matrix, and the correlation characteristic between the codes in the orthogonal spreading code group with the inter-group zero correlation window characteristic generated by spreading can be optimized by selecting a better spreading matrix;

then, a new orthogonal spreading code group with the inter-group zero correlation window characteristic is generated by the following spreading method:

wherein "", indicates Kronecker product;

each row of the extension matrix representation is used as a new code word, thus MK codes with the code length of NZ are shared, and the codes are sequentially divided into-groups, so that the codes can be totally divided into

And M groups:

a first group: g g_l3C_l®g₂,---,_l®g_K;

Second group: c. C₂®_gl, c₂Og₂₅---,c₂®_gitAnd the third component: ^ a ^ b_δι, c_M®g_z,--;c_Mg_K;

The M groups of orthogonal spread spectrum code groups generated after spreading have an intergroup zero correlation window which is greater than or equal to phi, gamma;

inserting the orthogonal spread spectrum code group with the intergroup zero correlation window characteristic into a certain number of zero guard intervals or time slots, thereby generating a new orthogonal spread spectrum code group with an intergroup zero correlation window which is greater than or equal to [ -LT, LT ];

if the correlation characteristics among the code words in the generated groups with the intergroup zero correlation window orthogonal spread spectrum code groups are not ideal, joint detection can be adopted to eliminate the influence of the interference from the code words in the groups due to the fact that the correlation characteristics among the code words in the groups are not ideal; because only the code words between the same code group have 4, I can carry out joint detection on the code words in the group, and the optimal complexity of the joint detection is omicron iota, wherein 2 is element modulation.
13. A method according to claim 2, 3 or 4, characterised in that it consists in pairing said

Each spreading address code of the orthogonal spreading code group is inserted into a zero guard interval or a time slot to increase the size of an intergroup zero correlation window between each group of spreading address codes generated after spreading.