KR102241411B1 - A method and apparatus for generating orthogonal codes with wide range of spreading factor - Google Patents

Abstract

In a quasi-synchronous spread spectrum system, a method of generating an orthogonal set is disclosed. The method according to an embodiment includes the steps of selecting a two-level autocorrelation sequence, selecting a first index set and a second index set from the two-level autocorrelation sequence, and the first index set and the second index set. And creating two quasi-orthogonal sets using the index set.

Description

A METHOD AND APPARATUS FOR GENERATING ORTHOGONAL CODES WITH WIDE RANGE OF SPREADING FACTOR}

The present disclosure relates to the field of orthogonal code generation, and more particularly, to generating an orthogonal codeset pair having a wide spread coefficient for a quasi-synchronous spread spectrum application.

Orthogonal codes have become an essential element of any direct sequence spread spectrum based communication system for communication over a wireless channel. Typically, one or more sets of codes are generated and provided to a spread spectrum based communication system for assignment to user(s). Here, each set contains codes that are orthogonal in nature. The orthogonal nature of the codes allows different users to communicate over the same channel while minimizing multiple access interference (MAI). This enables the assignment of single or multiple orthogonal codes in a set to the user(s) in a spread spectrum based communication system according to the user request. However, the total number of orthogonal codes in a set used in the spread spectrum is limited by a processing gain or a spreading factor of a spread spectrum-based communication system.

If perfect synchronization is maintained, orthogonal codes will be an obvious choice for the spread of user data. However, due to the influence of the nonlinear channel and the geographically wide distribution of multiple users, perfect synchronization is not guaranteed in an actual environment. However, current communication systems can limit synchronization errors to a small number of chips. And, the limitation of this synchronization error can be improved with the development of the silicon industry and signal processing algorithms.

Embodiments provide a method of generating two orthogonal code sets, each set having a broad spreading factor approximately equal to 1/3 of the spreading factor.

In still other embodiments, the generated orthogonal sets are characterized by the following properties.

-The autocorrelation side lobe of any code word in any set is 0 for a time shift of ±1 chip.

-The cross-correlation between any two codes in the set is 0 for a time shift of ±1 chip, including 0.

In a quasi-synchronous spread spectrum system according to an embodiment, a method of generating an orthogonal set includes the steps of selecting a 2-level autocorrelation sequence, and a first index from the 2-level autocorrelation sequence. Selecting a set and a second index set, and generating two quasi-orthogonal sets using the first index set and the second index set. The two-level autocorrelation sequence includes at least one of an element of -1 and an element of a first value.

In the selecting of the two-level autocorrelation sequence, the two-level autocorrelation sequence of the N-1 period may be selected, and the two-level autocorrelation sequence may include an element of +1 and an element of -1. Here, N may be a diffusion coefficient.

Selecting the first index set may include obtaining indices of all +1 elements of the second level autocorrelation sequence, selecting the first index set, and continuing among the second level autocorrelation sequences It may include disregarding some of the indexes corresponding to +1 in the first index set.

The selecting of the second index set may include obtaining indices of all -1 elements of the second level autocorrelation sequence, and selecting the second index set; And ignoring some of the indexes corresponding to -1 in the second level autocorrelation sequence in the second index set.

The method according to an embodiment may further include generating two quasi-orthogonal sets using the first index set and the second index set, and the two quasi-orthogonal sets May include a first quasi-orthogonal set and a second quasi-orthogonal set.

The method according to an embodiment is by circularly reading the two-level autocorrelation sequence starting from a position corresponding to the index of +1 to one of a left hand side or a right hand side. It may further include obtaining a first quasi-orthogonal set, wherein the first quasi-orthogonal set is obtained in a first matrix including rows and columns, and the column is a cyclic reading of the two-level autocorrelation sequence. Can be obtained by

In addition, the method according to an embodiment, starting from a position corresponding to an index of -1, circularly reading the two-level autocorrelation sequence to one of a left hand side or a right hand side. ) To obtain a second quasi-orthogonal set, wherein the second quasi-orthogonal set is obtained in a second matrix including rows and columns, and the columns are It can be obtained by circular reading.

In addition, the method according to an embodiment may further include acquiring two sets of orthogonal codes from the first quasi-orthogonal set and the second quasi-orthogonal set, and the two sets of orthogonal codes are the first It may include an orthogonal set and a second orthogonal set.

The first orthogonal set may be obtained by appending all +1 columns of the first matrix.

The second orthogonal set may be obtained by appending all -1 columns of the second matrix.

In a quasi-synchronous spread spectrum system according to another aspect, an apparatus for generating two sets of orthogonal codes of spreading coefficients N includes a sequence selection module for selecting a 2-level autocorrelation sequence, the 2 An index selection module for selecting a first index set and a second index set from the level of autocorrelation sequence, and generating two quasi-orthogonal sets using the first index set and the second index set. It may include an orthogonal code generation module. The two-level autocorrelation sequence includes at least one of an element of -1 and an element of a first value.

The sequence selection module may select a 2-level autocorrelation sequence in the N-1 period, and the 2-level autocorrelation sequence may include an element of +1 and an element of -1. Here, N may be a diffusion coefficient.

The index selection module obtains indices of all +1 elements of the second level autocorrelation sequence, selects the first index set, and corresponds to a continuous +1 of the second level autocorrelation sequence. Some of the indexes may be ignored in the first index set.

The index selection module obtains indices of all -1 elements of the second level autocorrelation sequence, selects the second index set, and corresponds to consecutive -1 of the second level autocorrelation sequence. Some of the indexes may be ignored in the second index set.

The orthogonal code generation module generates two quasi-orthogonal sets using the first index set and the second index set, and the two quasi-orthogonal sets are a first quasi-orthogonal set and a second index set. Can contain 2 quasi-orthogonal sets.

The orthogonal code generation module, starting from a position corresponding to the index of +1, is performed by circularly reading the two-level autocorrelation sequence to one of a left hand side or a right hand side. One quasi-orthogonal set is obtained, and the first quasi-orthogonal set is obtained in a first matrix including rows and columns, and the columns may be obtained by cyclic reading of the two-level autocorrelation sequence.

The orthogonal code generation module, starting from a position corresponding to the index of -1, is performed by circularly reading the two-level autocorrelation sequence to one of a left hand side or a right hand side. Two quasi-orthogonal sets are obtained, and the second quasi-orthogonal set is obtained in a second matrix including rows and columns, and the columns may be obtained by cyclic reading of the two-level autocorrelation sequence.

The orthogonal code generation module obtains two sets of orthogonal codes from the first quasi-orthogonal set and the second quasi-orthogonal set, and the two sets of orthogonal codes include a first orthogonal set and a second orthogonal set. I can.

The first orthogonal set is obtained by appending all +1 columns of the first matrix, and the second orthogonal set appends all -1 columns of the second matrix ( can be obtained by appending).

According to another embodiment, in a quasi-synchronous spread spectrum system, a method of generating two sets of orthogonal codes having a spreading factor N may be provided.

1 illustrates a device including various modules according to an exemplary embodiment.
2 is a flowchart illustrating a process of generating two codes according to embodiments.
3 illustrates a computing environment implementing a method for generating two sets of orthogonal codes according to embodiments disclosed herein.

Hereinafter, some embodiments will be described in detail with reference to the accompanying drawings. However, it is not limited or limited by these embodiments. The same reference numerals shown in each drawing indicate the same members.

The terms used in the description below have been selected as currently widely used general terms as possible while taking functions of the present invention into consideration, but this may vary according to the intention or custom of a technician working in the art, the emergence of new technologies, and the like.

In addition, in certain cases, there are terms arbitrarily selected by the applicant for the purpose of aiding understanding and/or convenience of description, and in this case, detailed meanings will be described in the corresponding description. Therefore, terms used in the following description should be understood based on the meaning of the term and the contents throughout the specification, not just the name of the term.

The embodiments provide a method and apparatus for generating an orthogonal codeset pair having a wide spreading coefficient for a quasi-synchronous spread spectrum application, and reception can be synchronized within a single chip. . The number of codes in each generated set may be equal to approximately 1/3 of the spreading factor.

1 illustrates a device including various modules according to an exemplary embodiment. The apparatus 100 includes a sequence selection module 101, an index selection module 102, and an orthogonal code generation module 103. The sequence selection module 101 selects a two-level autocorrelation sequence for the elements from the {1,-1} set in a period of p=N-1. The index selection module 102 selects one or more indices within the two-level autocorrelation sequence. The orthogonal code generation module 103 generates two sets of orthogonal codes, each set comprising a sequence of approximately N/3, where N is the spreading factor of the code.

In one embodiment, the device 100 may be implemented as a stand-alone chip, an integrated circuit (IC), a silicon on chip (SoC), or similar hardware including a processor and a memory coupled to the processor. The memory includes an orthogonal code generation module 103. The orthogonal code generation module 103 may generate two orthogonal codes, and each of the two sets of orthogonal codes may include N orthogonal codes of N periods, where N is a direct sequence spread spectrum. spread spectrum) based communication system.

The method according to an embodiment may generate two sets of orthogonal codes of approximately N/3 of the spreading factor N starting with a single two-level autocorrelation sequence of a period of P=N-1.

In one embodiment, the method takes into account the following conditions in generating two sets of an orthogonal set.

-The autocorrelation side lobe of any code word in any of the two sets is 0 for a time shift of ±1 chip.

-The cross correlation between any two codes in the set is 0 for a time shift of ±1 chip including 0.

1 to 3, like reference numbers consistently designate corresponding features throughout the drawings, which are shown in preferred embodiments.

The following description describes the basic terms used in the present disclosure.

- correlation (corss - correlation)

Cross-correlation refers to the degree of similarity between two different signals. The cross-correlation function can be of either periodic or aperiodic type. Mathematically, the periodic cross-correlation at the delay τ between _{two binary sequences c k} and c _j having elements from the set {1,-1} is defined as in Equation 1.

-2 level autocorrelation sequence

Assume that R(k) is a periodic autocorrelation at a delay of k. The binary sequence satisfies the property of Equation 2.

The two-level autocorrelation sequence as described above may be defined.

-left side shift work( left shift operation )

Let a _i be assumed to be a binary sequence given as follows.

a _i =a ₀ ,a ₁ ,a ₂ ,...

If so, the left-shift operation on the binary sequence according to g _{i + g} is resulting in a, a _{i + g} L ^g = (a _i) = _g a, _g a _+1, a _{g +2,} ... Can be given as L ^g can be named as the left shift operator by g.

-Quasi-orthogonal cordset ( quasi - orthogonal codeset )

A _p ={a ₀ ,a ₁ ,a ₂ ,... Let ,a _{p -2} ,a _{p -1} } be assumed as a binary set consisting of a binary sequence P, and each of the periods P _{can be sorted so that the sequence a i} represents the ith row of the matrix A _p. have. If a _j and a _k are _{elements of A p} and the cross-correlation R _{i ,j} is -1, then the set A _p may be named a quasi-orthogonal set of P order.

2 is a flowchart illustrating a process of generating two codes according to embodiments. The method creates a pair of orthogonal sets for a given processing gain (spreading factor), each set specified with an interference free window (IFW) of ±1. The generated orthogonal sets may be specified with a spreading factor that allows to estimate any value of N in which a two-level autocorrelation sequence of period N-1 exists. As shown in the flow diagram, at step 201. The method may choose the level of P = 2 N-1 period, the autocorrelation sequence S _i. In one embodiment, the two-level autocorrelation sequence is specified as a non-normalized periodic autocorrelation value of -1 out of phase.

In step 202, the method may obtain a first set of indexes (set A) to collect the index of all +1 in the sequence S _i. In an embodiment, in step 203, the method may ignore some of the indexes corresponding to consecutive +1s in the _{two-level autocorrelation sequence S i.}

In step 204, the method may obtain a second set of indexes (set B), by collecting all of the index in the sequence S _i -1. In one embodiment, the method may override a portion of the index corresponding to -1 in the subsequent second level autocorrelation sequence S _i.

In one embodiment, the method may generate two quasi-orthogonal sets from a first index set and a second index set. The two quasi-orthogonal sets may include a first quasi-orthogonal set and a second quasi-orthogonal set.

In one embodiment, in step 206, the method starts from a position corresponding to the index of +1 and circularly reading the 2-level autocorrelation sequence to the left hand side or the right hand side. By doing so, a first quasi-orthogonal set S ¹ _k may be obtained, and a first matrix including rows and columns may be formed. In an embodiment, the columns of the first matrix may include sequences obtained by cyclic reading a two-level autocorrelation sequence.

In one embodiment, in step 207, the method includes circularly reading a 2-level autocorrelation sequence starting from a position corresponding to an index of -1 to the left hand side or the right hand side. By doing so, a second quasi-orthogonal set S ² _k may be obtained, and a second matrix including rows and columns may be formed. In an embodiment, the columns of the second matrix may include sequences obtained by cyclic reading of a two-level autocorrelation sequence.

The set {S ^t _k }, t∈{1,2} may consist of an approximately P/3 sequence of period p=N-1. Here, N may be a targeted spreading coefficient of an orthogonal sequence that is designed and subsequently designed.

In one embodiment, the method may ^{transform each of the sets {S t} _k } and t∈{1,2} to obtain two orthogonal sets. In one embodiment, the two orthogonal sets may include a first orthogonal set and a second orthogonal set. The first orthogonal set can be obtained by appending all +1s of the row to the first quasi-orthogonal set S ¹ _k in the first matrix, the second orthogonal set adding all -1s of the row to the second matrix in the second matrix. 2 can be obtained by appending to the semi-orthogonal set S ² _k. This is an interference free window of 1, i.e. the codes are orthogonal to lag 0, ±1, and the autocorrelation side lobe of individual codes is also 0 for lag ±1. You can create two sets of orthogonal sets. The various actions in flowchart 200 may be performed in the order indicated or may be performed in a different order. In addition, in other embodiments, some actions of FIG. 2 may be omitted.

The gain of such codes is their availability in a spread spectrum system, and synchronization errors within the system can be limited to within a single chip. The method can result in a large area of the diffusion coefficient, which is due to the fact that any diffusion coefficient N can be implemented in the presence of a two level autocorrelation sequence of N-1 period.

The above-described flowchart is explained by way of example below.

For example, it is assumed that a two-level autocorrelation sequence S _i is given as in Equation 5.

The method may obtain a first set of indexes (set A) and a second set of indexes (set B) as shown in Equations 6 and 7.

Furthermore, the method may ignore some of the indexes corresponding to the consecutive sequence when +1 or -1 is consecutive among the two-step autocorrelation sequence. For example, in the autocorrelation sequence of Equation 5, the first 3 consecutive +1s may be consecutive, and the method ignores the index of "2" corresponding to the second +1 from the first index set of Equation 6. I can. In addition, in the autocorrelation sequence of Equation 5, -1 may be consecutive at the 4th and 5th, and in the method, an index of "5" corresponding to the 5th -1 is obtained from the second index set of Equation 7. Can be ignored. Accordingly, the method can obtain a set such as Equations 8 and 9 below.

The method is to obtain a first quasi-orthogonal set by circularly reading set A to a right hand side, starting from a position corresponding to the indices of +1, and converting the first matrix to Equation 10 Can be formed together.

The method is to obtain a second semi-orthogonal set by circularly reading the set B to the right hand side, starting from a position corresponding to the indices of -1, and converting the second matrix to Equation 11 Can be formed together.

In addition, the method is to convert the two semi-orthogonal sets into two orthogonal sets by attaching the row of +1 to the first matrix (Equation 10) and the row of -1 to the second matrix (Equation 11). I can.

3 illustrates a computing environment implementing a method for generating two sets of orthogonal codes according to embodiments disclosed herein. The computing environment 301 may include at least one processing unit 304, and the processing unit 304 may include a control unit 302 and an arithmetic logic unit 303. The computing environment 301 may include a memory 305, a storage unit 306, a plurality of networking devices 308, and a plurality of input/output devices 307. The processing unit 304 may process commands of an algorithm. The processing unit 304 may receive a command from a control unit for performing processing. In addition, logic and arithmetic operations related to execution of an instruction may be computed with the help of the arithmetic logic unit 304.

The entire computing environment 301 may be composed of homogeneous and heterogeneous multi-cores, different types of multiple CPUs, special media, and other accelerators. The processing unit 304 may be in charge of processing an instruction of an algorithm. In addition, the plurality of processing units 304 may be located on a single chip or on a plurality of chips.

Algorithms including instructions and codes required for implementation may be stored in memory 305 or storage 306 or both. In the stage of execution, instructions may be fetched from the corresponding memory 305 and/or storage unit 306 and processed by the processing unit 304.

Among hardware implementations, various networking devices 308 or external input/output devices 307 may be connected to a computing environment and may support implementations through networking devices and input/output devices.

The embodiments disclosed herein may be implemented through execution of at least one software program that is executed on at least one hardware device and performs a network management function for controlling elements. The elements shown in FIGS. 1 and 2 may be at least one hardware device or may be a combination of a hardware device and a software module.

The apparatus described above may be implemented as a hardware component, a software component, and/or a combination of a hardware component and a software component. For example, the devices and components described in the embodiments include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), It may be implemented using one or more general purpose or special purpose computers, such as a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications executed on the operating system. Further, the processing device may access, store, manipulate, process, and generate data in response to the execution of software. For the convenience of understanding, although it is sometimes described that one processing device is used, one of ordinary skill in the art, the processing device is a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that it may include. For example, the processing device may include a plurality of processors or one processor and one controller. In addition, other processing configurations are possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of these, configuring the processing unit to operate as desired or processed independently or collectively. You can command the device. Software and/or data may be interpreted by a processing device or, to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. , Or may be permanently or temporarily embodyed in a transmitted signal wave. The software may be distributed over networked computer systems and stored or executed in a distributed manner. Software and data may be stored on one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiment, or may be known and usable to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -A hardware device specially configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those produced by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operation of the embodiment, and vice versa.

As described above, although the embodiments have been described by the limited embodiments and drawings, various modifications and variations are possible from the above description to those of ordinary skill in the art. For example, the described techniques are performed in a different order from the described method, and/or components such as systems, structures, devices, circuits, etc. described are combined or combined in a form different from the described method, or other components Alternatively, even if substituted or substituted by an equivalent, an appropriate result can be achieved.

Therefore, other implementations, other embodiments, and those equivalent to the claims also fall within the scope of the claims to be described later.

Claims (20)

In a quasi-synchronous spread spectrum system, in a method of generating an orthogonal set,
Selecting a two-level autocorrelation sequence;
Selecting a first index set and a second index set from the two-level autocorrelation sequence; And
Generating two quasi-orthogonal sets using the first index set and the second index set
Including,
Selecting the first index set,
Obtaining indices of all +1 elements of the two-level autocorrelation sequence, and selecting the first index set; And
Ignoring some of the indexes corresponding to consecutive +1s in the autocorrelation sequence of the two levels in the first index set
Including,
The two-level autocorrelation sequence is a sequence comprising at least one of an element of -1 and an element of a first value. The method of claim 1,
The step of selecting the two-level autocorrelation sequence includes selecting a two-level autocorrelation sequence in a period N-1, wherein N is a spreading factor,
The two-level autocorrelation sequence includes an element of +1 and an element of -1. delete The method of claim 2,
Selecting the second index set,
Obtaining indices of all -1 elements of the two-level autocorrelation sequence, and selecting the second index set; And
Ignoring some of the indexes corresponding to -1 in the second level autocorrelation sequence in the second index set
How to include. The method of claim 1,
The two quasi-orthogonal sets,
A method comprising a first quasi-orthogonal set and a second quasi-orthogonal set. The method of claim 5,
Starting from the position corresponding to the index of +1, the first quasi-orthogonal set is obtained by circularly reading the autocorrelation sequence of the 2nd level to either the left hand side or the right hand side. Steps to do
Including more,
The first quasi-orthogonal set is obtained in a first matrix comprising rows and columns, and the columns are obtained by cyclic reading of the two-level autocorrelation sequence. The method of claim 6,
Starting from the position corresponding to the index of -1, the second quasi-orthogonal set is obtained by circularly reading the autocorrelation sequence of the second level to either the left hand side or the right hand side. Steps to do
Including more,
The second quasi-orthogonal set is obtained in a second matrix comprising rows and columns, and the columns are obtained by cyclic reading of the two-level autocorrelation sequence. The method of claim 7,
Obtaining two sets of orthogonal codes from the first quasi-orthogonal set and the second quasi-orthogonal set
Including more,
The two sets of orthogonal codes include a first orthogonal set and a second orthogonal set. The method of claim 8,
The first orthogonal set is obtained by appending all +1 columns of the first matrix. The method of claim 8,
The second orthogonal set is obtained by appending every -1 column of the second matrix. In a quasi-synchronous spread spectrum system, an apparatus for generating two sets of orthogonal codes of spreading coefficient N,
A sequence selection module for selecting a two-level autocorrelation sequence;
An index selection module for selecting a first index set and a second index set from the two-level autocorrelation sequence; And
An orthogonal code generation module that generates two quasi-orthogonal sets using the first index set and the second index set
Including,
The index selection module obtains indices of all +1 elements of the 2-level autocorrelation sequence, selects the first index set, and selects an index corresponding to consecutive +1 among the 2-level autocorrelation sequences. Ignore some in the first index set,
The apparatus for generating an orthogonal set wherein the two-level autocorrelation sequence is a sequence including at least one of an element of -1 and an element of a first value. The method of claim 11,
The sequence selection module selects an autocorrelation sequence of two levels in a period N-1, wherein N is a spreading coefficient,
The two-level autocorrelation sequence includes an element of +1 and an element of -1. delete The method of claim 12,
The index selection module obtains indices of all -1 elements of the 2-level autocorrelation sequence, selects the second index set, and among indices corresponding to consecutive -1 of the 2-level autocorrelation sequence An apparatus that ignores some in the second index set. The method of claim 11,
The orthogonal code generation module generates two quasi-orthogonal sets using the first index set and the second index set,
The two quasi-orthogonal sets comprising a first quasi-orthogonal set and a second quasi-orthogonal set. The method of claim 15,
The orthogonal code generation module, starting from a position corresponding to the index of +1, by circularly reading the autocorrelation sequence of the two levels to one of a left hand side or a right hand side. Acquire the first quasi-orthogonal set,
The first quasi-orthogonal set is obtained in a first matrix comprising rows and columns, and the columns are obtained by cyclic reading of the autocorrelation sequence of the two levels. The method of claim 16,
The orthogonal code generation module, starting from a position corresponding to the index of -1, by circularly reading the autocorrelation sequence of the two levels to either a left hand side or a right hand side Acquire a second quasi-orthogonal set,
The second quasi-orthogonal set is obtained in a second matrix comprising rows and columns, and the columns are obtained by cyclic reading of the two-level autocorrelation sequence. The method of claim 17,
The orthogonal code generation module obtains two sets of orthogonal codes from the first quasi-orthogonal set and the second quasi-orthogonal set,
The two sets of orthogonal codes include a first orthogonal set and a second orthogonal set. The method of claim 18,
The first orthogonal set is obtained by appending all +1 columns of the first matrix. delete

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