WO2018056507A1

WO2018056507A1 - Method for generating and transmitting downlink preamble in wireless communication system

Info

Publication number: WO2018056507A1
Application number: PCT/KR2016/013316
Authority: WO
Inventors: 홍대식; 이학건; 김현수; 임성묵
Original assignee: 연세대학교 산학협력단
Priority date: 2016-09-21
Filing date: 2016-11-18
Publication date: 2018-03-29
Also published as: KR101883064B1; KR20180031925A

Abstract

Disclosed is a method for generating and transmitting a downlink preamble in a wireless communication system supporting variable tone spacing (VTS). The disclosed method for generating a downlink preamble comprises the steps of: determining a tone spacing interval for a first user terminal and a second user terminal; generating a first preamble having a length determined according to a first tone spacing interval for the first user terminal; generating a second preamble having a length determined according to a second tone spacing interval for the second user terminal; and overlapping the first preamble and the second preamble to generate a third preamble to allow a cyclic prefix (CP) of the second preamble to be located between preamble sequences.

Description

Downlink Preamble Generation and Transmission Method in Wireless Communication System

The present invention relates to a method for generating and transmitting a downlink preamble in a wireless communication system, and more particularly, to a method for generating and transmitting a downlink preamble in a wireless communication system supporting variable tone spacing (VTS).

Currently, OFDM technology is used in wireless communication systems such as mobile communication and wireless LAN. OFDM is a technology for transmitting data using a plurality of subcarriers (subcarriers) spaced at regular intervals.

Meanwhile, in order to obtain a higher data rate in a wireless communication system, a larger frequency band is required, and Carrier Aggregation (CA) is used as a solution. However, because each user communicates in a different channel environment, the interference degree or form is different according to the channel environment, and when the interval between subcarriers is fixed, ISI (Inter-Symbol interference) and ICI (Inter-Carrier Interference) are used. All have problems that are difficult to control.

Recently, research on Variable Tone Spacing (VTS) -OFDM, which transmits data by adjusting tone spacing for each user, is being conducted.

FIG. 1 is a diagram illustrating a subcarrier in a wireless communication system supporting variable tone spacing, and FIG. 2 is a diagram illustrating a symbol length in a time domain according to an interval of subcarriers.

Tone spacing refers to an interval Δf of subcarriers, and tone spacing in a wireless communication system supporting variable tone spacing may be differently allocated to each user group. 1 illustrates a case where the tone spacing interval assigned to the second user group is twice the tone spacing interval of the first user group. In general, the tone spacing frequency spacing difference may be set to 2 ⁿ (n is a natural number).

When different tone spacings are allocated for each user, a difference occurs in the length of a symbol transmitted in a time domain for each user group as shown in FIG. 2 due to the frequency difference. As shown in FIG. 1, when the tone spacing interval differs twice, the symbol length in the time domain also differs twice.

Therefore, the length of the preamble transmitted from the base station to the user terminal for time synchronization is also different for each of the first and second user groups, and thus, a preamble having a different structure for each of the first and second user groups should be used. Since this can increase the complexity of the system and reduce the transmission speed, it is necessary to study a method of synchronizing time with both the first and second user groups in one preamble structure.

The present invention provides a preamble generation and transmission method for allowing a user terminal to which different tone spacings are allocated to estimate time synchronization through one preamble structure in a wireless communication system supporting variable tone spacing.

According to an embodiment of the present invention to achieve the above object, a method of generating a downlink preamble in a wireless communication system, the method comprising: determining a tone spacing interval for the first and second user terminal; Generating a first preamble of a length determined according to a first tone spacing interval for the first user terminal; Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal; And generating a third preamble by overlapping the first and second preambles such that a cyclic prefix (CP) of the second preamble is located between the preamble sequences.

In addition, according to another embodiment of the present invention to achieve the above object, in the method for generating a downlink preamble in a wireless communication system, generating a first preamble having a length determined according to the first tone spacing interval for the first user terminal; Doing; Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal; And generating a third preamble by overlapping the first and second preambles in a state in which terminations of the first preamble and the second preamble are synchronized.

In addition, according to another embodiment of the present invention to achieve the above object, in the downlink preamble transmission method in a wireless communication system, a first preamble having a length determined according to the first tone spacing interval for the first user terminal; Generating; Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal; Generating a third preamble by overlapping the first and second preambles such that a cyclic prefix (CP) of the second preamble is located between preamble sequences; And transmitting the third preamble to the first and second user terminals.

According to the present invention, in a wireless communication system supporting variable tone spacing, a user terminal may estimate time synchronization of a downlink using one preamble structure.

According to the present invention, by allowing users assigned different tone spacings to estimate time synchronization using one preamble structure, complexity of the system can be reduced and transmission speed can be improved.

1 is a diagram illustrating a subcarrier of a wireless communication system supporting variable tone spacing.

2 is a diagram illustrating a symbol length in a time domain according to an interval of subcarriers.

3 is a flowchart illustrating a downlink preamble generation method in a wireless communication system according to an embodiment of the present invention.

4 is a view for explaining the structure of a downlink preamble according to the present invention.

5 is a flowchart illustrating a downlink preamble transmission method in a wireless communication system according to an embodiment of the present invention.

6 is a diagram illustrating a result of estimating time synchronization in a user terminal using a downlink preamble according to the present invention.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

In the present specification, a base station of a wireless communication system generally refers to a fixed station for communicating with a terminal, and in other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like. Can be called.

In addition, a user terminal of a wireless communication system may be fixed or mobile, and may include a mobile station (MS), a user equipment (UE), a mobile terminal (MT), a subscriber station (SS), a wireless device, It may be called other terms such as a personal digital assistant, a wireless modem, a handheld device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a method for generating a downlink preamble in a wireless communication system according to an embodiment of the present invention, and FIG. 4 is a view for explaining the structure of a downlink preamble according to the present invention. The downlink preamble generation method according to the present invention may be performed in a base station supporting variable tone spacing.

According to the present invention, the base station determines the tone spacing frequencies for the first and second user terminals (S310). At this time, the base station may determine the tone spacing according to the channel information transmitted from the first and second user terminal. For example, the Doppler effect may be high in a user terminal having high mobility, and thus tone spacing may be allocated at a relatively large frequency interval.

The base station generates a first preamble for the first user terminal and a second preamble for the second user terminal according to the determined tone spacing interval. More specifically, a first preamble having a length determined according to the first tone spacing interval for the first user terminal is generated (S320), and a second preamble having a length determined according to the second tone spacing interval for the second user terminal is generated. Create (S330).

Referring to FIG. 4 showing the structure of the downlink preamble when the tone spacing frequency differs by 2 times, since the second tone spacing frequency interval 2Δf is twice the first tone spacing frequency interval Δf, It can be seen that the length of the first preamble 410 is longer than the length of the second preamble 420.

The first and

second preambles

410 and 420 both include a preamble sequence A for the same time synchronization, and the same preamble sequence is repeatedly allocated. At this time, the number of repetitions of the preamble sequence is determined according to the first and second tone spacing intervals, that is, the symbol length. According to the first and second tone spacing intervals, since the length of the first preamble 410 is longer than the length of the second preamble 420, the number of repetitions of the preamble sequence with respect to the first preamble 410 is determined by the second preamble ( More than 420).

The first and second preambles include Cyclic Prefixes (411, 421).

3, the base station overlaps the first and

second preambles

410 and 420 to generate the third preamble 430 such that the CP 421 of the second preamble 420 is located between the preamble sequences ( S340).

In this case, as shown in FIG. 4, the base station synchronizes the termination of the first preamble 410 and the second preamble 420 such that the length of the third preamble 430 is equal to the length of the first preamble 410. In this state, the first and

second preambles

410 and 420 overlap. Therefore, a third preamble 430 that is equal to the length of the first preamble 410 may be generated.

A portion of the preamble sequence is overlapped by the overlap of the first and

second preambles

410 and 420. Therefore, in the third preamble 430, the preamble sequence of the rear stage is referred to based on the CP 421 of the second preamble 420. The size (2 XA) of the symbol is an integer multiple, for example, two times compared to the sizes of the preamble sequence symbols of the first and second preambles (410, 420).

In addition, the base station generates the third preamble 430 by multiplying the CP symbol 411 of the first preamble 410 so that the first user terminal can easily estimate time synchronization using the third preamble 430. do.

The user terminal obtains a correlation value with respect to the transmitted preamble and estimates time synchronization based on the peak value of the timing metric, and a peak value usually occurs in a CP symbol period. Since the size of the sequence symbol at the rear end of the third preamble 430 is doubled due to the overlap, the first user terminal can detect the peak value in the CP symbol 411 section of the first preamble 410 accordingly. For example, the size of the CP symbol 411 of the first preamble 410 is increased by twice.

In the case of the second user terminal, the size of the preamble sequence at the rear end of the third preamble 430 is increased twice as compared with the second preamble. However, since the pattern of the symbols is the same, time estimation is performed using the third preamble 430. Can be performed.

As a result, according to the present invention, in a wireless communication system supporting variable tone spacing, a user terminal may estimate time synchronization of a downlink using one preamble structure.

In addition, according to the present invention, by allowing users assigned different tone spacings to estimate time synchronization using one preamble structure, the complexity of the system and the transmission speed may be improved.

In the downlink preamble transmission method according to the present invention, the preamble generated as described in FIG. 3 is transmitted to user terminals assigned different tone spacings. That is, all user terminals assigned different tone spacings estimate time synchronization using the same preamble.

More specifically, according to the present invention, the base station generates a first preamble having a length determined according to the first tone spacing interval for the first user terminal (S510), and a length determined according to the second tone spacing interval for the second user terminal. A second preamble is generated (S520). The first and second preambles are overlapped to generate a third preamble such that CPs of the second preambles are located between the preamble sequences (S530). In operation S540, the generated third preamble is transmitted to the first and second user terminals.

Since the first and second user terminals are provided with information about the tone spacing intervals allocated to the base station, the first and second user terminals may estimate time synchronization from the third preamble, respectively.

For example, since the second user terminal knows the length of the symbol transmitted to the second user terminal, the second user terminal may estimate the time synchronization by taking a correlation value from the CP symbols of the second preamble included in the third preamble.

In FIG. 6, the solid line graph is a time synchronization estimation result at the first user terminal of FIG. 3, and the dotted line graph is a time synchronization estimation result at the second user terminal of FIG. 3.

As shown in FIG. 6, peak values 610 and 620 of a timing metric indicating time synchronization are detected in both the first and second user terminals, and the peak value detection point becomes a time synchronization estimation point. . At this time, it may be confirmed that the time synchronization estimation point of the second user terminal is later than the position of the first and second preamble CPs included in the third preamble.

As a result, it can be seen that time synchronization can be estimated in all user terminals to which different tone spacings are allocated using the downlink preamble according to the present invention.

The technical contents described above may be embodied in the form of program instructions that may be executed by various computer means and may be recorded in a computer readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. Program instructions recorded on the media may be those specially designed and constructed for the purposes of the embodiments, or they may be of the kind well-known and available to those having skill in the computer software arts. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiments. For those skilled in the art, various modifications and variations are possible from these descriptions. Therefore, the spirit of the present invention should not be limited to the described embodiments, and all the things that are equivalent to or equivalent to the claims as well as the following claims will belong to the scope of the present invention. .

Claims

A method of generating a downlink preamble in a wireless communication system,

Determining tone spacing intervals for the first and second user terminals;

Generating a first preamble of a length determined according to a first tone spacing interval for the first user terminal;

Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal; And

Generating a third preamble by overlapping the first and second preambles such that a cyclic prefix (CP) of the second preamble is located between preamble sequences;

Preamble generation method comprising a.
The method of claim 1,

The preamble sequences included in the first and second preambles are the same,

The number of repetitions of the preamble sequence is determined according to the first and second tone spacing intervals.

Preamble generation method.
The method of claim 2,

Generating the third preamble is

Synchronizing the termination of the first preamble and the second preamble, overlapping the first and second preamble

Preamble generation method.
The method of claim 1,

Generating the third preamble is

Generating the third preamble by integrally multiplying the CP symbols of the first preamble

Preamble generation method.
The method of claim 1,

The length of the third preamble is

Equal to the length of the first preamble

Preamble generation method.
The method of claim 1,

Determining the tone spacing is

The tone spacing is determined according to channel information transmitted from the first and second user terminals.

Preamble generation method.
A method of generating a downlink preamble in a wireless communication system,

Generating a first preamble of a length determined according to a first tone spacing interval for the first user terminal;

Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal; And

Generating a third preamble by overlapping the first and second preambles in a state in which the ends of the first preamble and the second preamble are synchronized;

Preamble generation method comprising a.
The method of claim 7, wherein

Generating the third preamble is

Generating the third preamble by integrally multiplying the CP symbols of the first preamble

Preamble generation method.
In the downlink preamble transmission method in a wireless communication system,

Generating a first preamble of a length determined according to a first tone spacing interval for the first user terminal;

Generating a second preamble of a length determined according to a second tone spacing interval for the second user terminal;

Generating a third preamble by overlapping the first and second preambles such that a cyclic prefix (CP) of the second preamble is located between preamble sequences; And

Transmitting the third preamble to the first and second user terminals.

Preamble transmission method comprising a.
The method of claim 9,

The lengths of the preamble sequences included in the first and second preambles are the same,

The number of repetitions of the preamble sequence is determined according to the first and second tone spacing frequencies.

Preamble Transmission Method.
The method of claim 9,

Generating the third preamble is

Synchronizing the termination of the first preamble and the second preamble, overlapping the first and second preamble

Preamble Transmission Method.
The method of claim 9,

Generating the third preamble is

Generating the third preamble by integrally multiplying the CP symbols of the first preamble

Preamble Transmission Method.