KR20100118646A - Packet transmitting method for decreasing effect of impulsive noise based on multi-carrier - Google Patents

Abstract

PURPOSE: A method for transmitting a multiple carrier-based packet is provided to restore damaged data in case of data in a pre-set domain is damaged using data with the same value as the damaged data in other domain while a packet with the damage data is received. CONSTITUTION: Packet data or 0 is allocated to a plurality of sub-carriers with respect to a long symbol or a data symbol in order to secure an identical infinite value in the long symbol or the data symbol forming a packet(S410). The allocated symbol is converted into a time domain(S420). A transmitter converts the symbol of a frequency domain into the symbol of a time domain. Using an inverse fast Fourier transform. The converted preamble, long symbol, and data symbol are transmitted to a receiver(S430).

Description

PACKET TRANSMITTING METHOD FOR DECREASING EFFECT OF IMPULSIVE NOISE BASED ON MULTI-CARRIER}

The present invention relates to multi-carrier-based packet transmission, and more particularly, to the packet transmission in an orthogonal frequency division multiplexing (OFDM) communication system by minimizing the influence of impulsive noise. The present invention relates to a multicarrier-based packet transmission method for reducing the influence of impulsive noise, which can prevent problems that may occur.

Efforts have been made to construct a power line network using power line communication technology to existing power lines developed for power energy transmission, and are currently being commercialized.

The power line network is divided into high voltage and low voltage, indoor and outdoor, low speed and high speed, and research on each power line network has been conducted all over the world, and recently, research on access network using power line communication has been actively conducted in the US and Europe. It is becoming.

The access network uses optical communication as a backbone network and connects to the customer by using a high voltage underground or overhead distribution line and a low voltage power line. When an access network using powerline communication is established, Internet service, automatic meter reading (AMR) service, and load management service are possible.

Since power lines are not developed for the purpose of communication lines, power line communication channels are frequency selective channels and there can be a variety of colored noises.

In the power line communication system, multi-carrier transmission methods such as Discrete Multi-Tone (DMT) and Orthogonal Frequency Division Multiplexing (OFDM) technologies are used for efficient transmission of high-speed power line communication. The pilot and the data to be transmitted are allocated to each of a plurality of subcarriers, converted into a time domain, and transmitted to a receiver through a power line.

In the power line communication system, as in the example shown in FIG. 1, there is an impulsive noise that is five times larger than the average noise level, which is caused by peripheral power devices, circuits, and electrical causes. Can be generated.

Of course, impulsive noise may be present in general wireless communication systems as well as in powerline communication systems.

Packets transmitted from the transmitter to the receiver through the transmission path may be damaged by the effects of these impulsive noises, so that some of the packets may be damaged, requiring complicated methods for restoration to recover the damaged packets from the receiver, or The packet may be re-requested and received.

As such, the system has a problem of degrading system performance due to problems that may be caused by impulsive noise.

Therefore, there is a need for a method capable of minimizing the effects of impulsive noise.

An object according to an embodiment of the present invention, which was devised to solve the above problems, minimizes the effect of impulsive noise and thus prevents the problem that can be caused by impulsive noise. To provide a multi-carrier-based packet transmission method for reducing.

Another object of the present invention is to provide a multi-carrier-based packet transmission method for reducing the influence of impulsive noise, which can improve the system performance by minimizing the influence of impulsive noise.

In order to achieve the above object, a packet transmission method according to an aspect of the present invention is a multi-carrier based packet transmission method including a plurality of (N) subcarriers, the group of two subcarriers for a long symbol (long symbol) Separating into subcarriers of; Allocating a preset pilot to one of the two subcarriers separated from each other and allocating zero to the other one; Converting the long symbol into a time domain; And transmitting the long symbol converted into the time domain to a receiver.

The two groups may be a group of odd index subcarriers among the subcarriers and an even index subcarrier among the subcarriers.

The long symbol may include a first long symbol and a second long symbol, and the pilot or zero may be assigned to the same group of the two long symbols or to a different group of the two long symbols.

Separating the subcarriers for the data symbols into the two groups of subcarriers; Allocating data to a group to which the pilot is allocated among the two groups for the data symbol, and allocating the zero to the remaining group; Converting the data symbols into a time domain; And transmitting the data symbol converted into the time domain to the receiver.

Separating the subcarriers for the data symbols into the two groups of subcarriers; Allocating data to either of the two groups for the data symbol and allocating the zeros to the remaining groups; Converting the data symbols into a time domain; And transmitting the data symbol converted into the time domain to the receiver.

The method may further include assigning a preset weight to the data, converting the data symbol to which the weight is assigned to the time domain, and adding a preset weight to the pilot. The long symbol given the weight may be converted into the time domain.

A packet transmission method according to another aspect of the present invention is a multi-carrier-based packet transmission method including a plurality of (N) subcarriers, the absolute value of the symbols constituting the packet in the time domain in the same period of time domain index in a constant period Allocating preset packet data or zero to each of the subcarriers for the symbol so as to have; Converting the symbol into a time domain; And transmitting the symbol converted to the time domain to a receiver.

The allocating may include allocating the packet data or the zero to have a phase equal to the same absolute value or a phase difference of 180 degrees to the same absolute value.

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, a multicarrier based packet transmission method for reducing the influence of impulsive noise according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 7.

Impulsive noise may be generated by surrounding power devices and circuits or by electrical causes in power line communication, or may be generated by the surrounding environment in wireless communication using an antenna. When transmitting a packet from a transmitter to a receiver, the impulsive noise may break long symbols or data symbols constituting the packet, which may degrade the performance of the system.

According to the present invention, when a symbol included in a packet is transformed into a time domain, the symbol has the same value at a predetermined period so that a channel is estimated using data of another region having the same value at the receiver even if a part of the symbol is broken by impulsive noise. In order to minimize the effects of impulsive noise and to restore data, the main purpose is to improve the performance of a multi-carrier based communication system.

2 shows a communication system for explaining a packet transmission method according to an embodiment of the present invention, and shows a power line communication system as an example.

Referring to FIG. 2, the system includes a transmitter 210, a power line 220, and a receiver 230.

The power line 220 serves as a transmission path for transmitting the packet converted into the time domain by the transmitter 210 to the receiver 230.

At this time, the power line 220 transmits the impulse noise generated by the peripheral power device constituting the power system, the device constituting the power line communication system, and the circuit and the electrical cause, etc. The present invention is directed to such impulsive noise. This is to improve system performance by minimizing the problems caused by the system.

Of course, in the case of a wireless communication system, the standby serves as a transmission path.

The receiver 230 receives a packet transmitted from the transmitter 210 through the power line 220 and restores channel estimation and data using the received packet.

In the present invention, since the receiver may distract from the gist of the present invention, a detailed description thereof will be omitted.

The transmitter 210 allocates a predetermined pilot or data to be transmitted to a symbol constituting a packet by using a multicarrier, converts it to a time domain, and transmits the data to the receiver 230 through the power line 220.

In the present invention, when converting a symbol constituting the packet into the time domain, the transmitter allocates a predetermined pilot or data to be transmitted and zero to a plurality of subcarriers to have the same absolute value at a predetermined period.

In this case, as shown in FIG. 3, the packet includes a preamble (or frame separator) 310, a long symbol 320, and a data symbol 330.

The preamble 310 is a delimiter for classifying frames and includes information on synchronization and automatic gain adjustment (AGC).

The long symbol 320 is a symbol required for estimating a channel, and a preset pilot may be allocated. The long symbol 320 may be two or may be included in the preamble 310.

The data symbol 330 is a symbol to which real data is assigned.

The present invention assigns pilot or data to a plurality of subcarriers for a long symbol or a data symbol such that the long symbol and the data symbol may have the same absolute value at a constant period of the time domain index in the time domain. This is explained by reference.

4 is a flowchart illustrating a packet transmission method according to an embodiment of the present invention.

Referring to FIG. 4, a packet transmission method includes packet data or zeros in a plurality of subcarriers for a symbol such that a symbol constituting a packet, that is, a long symbol or a data symbol has the same absolute value at a constant period of a time domain index in the time domain. Assign (S410).

Here, the packet data may mean a preset pilot when the symbol is a long symbol, and may mean data to be transmitted when the symbol is a data symbol. The pilot may be a pilot modulated by a binary phase shift key (BPSK). have.

That is, when a long symbol or a data symbol is converted from the frequency domain to the time domain, packet data and 0 may be allocated to the plurality of subcarriers by using various methods in which each symbol may have the same absolute value at a constant period of the time domain index. Can be.

If packet data or 0 is allocated to each subcarrier of the symbol, the allocated symbols are converted into a time domain (S420).

The transmitter converts a symbol in the frequency domain to a time domain using an inverse fast fourier transform (IFFT).

Through this process, the preamble, long symbol, and data symbol constituting the packet are converted into a time domain and transmitted to the receiver (S430).

The above-described process for packet data allocation, conversion to a time domain, and transmission to a receiver may be performed sequentially for each symbol.

Here, since the long symbol or the data symbol has the same absolute value at a constant period of the time domain index in the time domain, even if information of one region is received in a broken state by impulsive noise, the receiver uses the same information in the other region. Estimation or data reconstruction is possible.

As can be seen through this, the packet transmission method according to an embodiment of the present invention can improve system performance by eliminating problems that may be caused by impulsive noise.

FIG. 5 is a flowchart illustrating an embodiment of step S410 illustrated in FIG. 4.

Referring to FIG. 5, in the assigning step S410, subcarriers for a symbol are divided into a plurality of groups so as to have the same absolute value at a predetermined period of the time domain index in the time domain (S510).

Here, the number of groups to be separated may vary depending on the period of the time domain index, in which the same absolute value is repeated in the time domain, or may vary according to a method of allocating packet data and 0 to subcarriers. The description is omitted since it may distract from the gist of the question.

Packet data or 0 is allocated to each of the separated plurality of groups (S520).

Here, the group to which the packet data or zero is allocated may be determined according to a method of allocating the packet data or the group to be equal to the same absolute value at a predetermined period of the time domain index in the time domain.

For example, by separating subcarriers for a symbol into a group of odd index subcarriers and a group of even index subcarriers, assigning packet data to a group of even index subcarriers, and assigning zeros to a group of odd index subcarriers, It may have the same absolute value at regular intervals of the time domain index.

In FIG. 4 and FIG. 5, packet data and 0 are allocated such that symbols have the same absolute value at regular intervals in the time domain, and may have the same absolute value and further have the same phase or a 180 degree difference.

When packet data and 0 are allocated to each group, a predetermined weight may be given to the packet data in consideration of the average transmission strength of the symbol converted into the time domain. The weight to be applied may vary depending on the type of symbol, and when the symbol is a data symbol, its value may vary depending on the data modulation scheme.

Of course, the packet transmission method according to an embodiment of the present invention shown in Figs. 4 and 5 is applicable to all symbols constituting the packet, but may be applied to only one of the long symbol and the data symbol according to the situation.

6 is an operation flowchart for a packet transmission method according to another embodiment of the present invention, which is an operation flowchart for a long symbol.

Referring to FIG. 6, the packet transmission method divides a plurality (N) of subcarriers for a long symbol into two groups of subcarriers (S610).

Here, the subcarriers may be divided into two groups, but it is preferable to divide the subcarriers into groups of even index subcarriers and groups of odd index subcarriers.

A preset pilot is allocated to any one of the two subcarriers of the separated group, and 0 is allocated to the other one (S620).

In this case, the pilot allocated to the subcarrier may be a pilot modulated by BPSK, that is, (-1, 0) or (1, 0).

The packet includes two long symbols of the first long symbol and the second long ball. The group to which the pilot is allocated in the first long symbol and the group to which the pilot is allocated in the second long symbol may be the same or different.

For example, the pilot may be allocated to the even-index subcarrier groups of the first long symbol and the second long symbol, and the zero may be assigned to the odd-index subcarrier groups of the first long symbol and the second long symbol, and the even number of the first long symbol may be allocated. The pilot may be allocated to the index subcarrier group and the odd index subcarrier group of the second long symbol, and zero may be allocated to the odd index subcarrier group of the first long symbol and the even index subcarrier group of the second long symbol.

When a pilot or 0 is allocated to the two separated groups, a preset weight is assigned to the pilot (S630).

The long symbol assigned to the pilot is converted into the time domain, and the long symbol converted into the time domain is transmitted to the receiver (S640 and S650).

Here, the long symbol may be transformed into the time domain by an inverse fast fourier transform (IFFT).

In two groups of subcarriers for two long symbols included in a packet, a first long symbol and a second long symbol, to which a pilot and zero are assigned to different groups, are represented by Equations 1 and 2 below. Can be converted to the time domain.

을 만족하는 값인 것이 바람직하다. Where (1) and (2) mean a first long symbol and a second long symbol, n means a time domain index, k means a subcarrier index, and N means the number of subcarriers, and Denotes a weight, P _k denotes a pilot modulated by BPSK, and p _n denotes a long symbol converted into a time domain. Α denotes an average transmission strength.

It is preferable that the value satisfies.

과

을 만족하는 것을 알 수 있다. 즉, 짝수 인덱스 부반송파의 그룹에 파일롯이 할당된 제1 롱 심볼은 시간 영역에서 시간 영역 인덱스 N/2을 주기로 동일한 절대값과 위상을 가지고, 홀수 인덱스 부반송파의 그룹에 파일롯이 할당된 제2 롱 심볼은 시간 영역에서 시간 영역 인덱스 N/2을 주기로 동일한 절대값과 180도의 위상차를 가진다.As can be seen from <Equation 1> and <Equation 2>, the long symbol converted to the time domain

and

It can be seen that satisfactory. That is, the first long symbol assigned a pilot to a group of even-index subcarriers has the same absolute value and phase with a time-domain index N / 2 in the time domain, and the second long symbol assigned a pilot to a group of odd-index subcarriers. Has a phase difference of 180 degrees with the same absolute value at a time domain index N / 2 in the time domain.

Of course, assigning a pilot to the group of odd index subcarriers for the first long symbol and the group of even index subcarriers for the second long symbol, and the odd number of even index subcarriers for the first long symbol and the second long symbol 0 may be allocated to a group of index subcarriers.

On the other hand, in two groups of subcarriers for two long symbols, the same value may be assigned to the same group. That is, the pilot may be allocated to the even-index subcarrier groups of the first long symbol and the second long symbol, and the zero may be allocated to the odd-index subcarrier groups of the first long symbol and the second long symbol. A pilot may be allocated to the odd index subcarrier group of the second long symbol and 0 may be allocated to the even index subcarrier group of the first long symbol and the second long symbol.

을 만족하도록 파일롯에 웨이트가 부여될 수 있다.Of course, even if the same value is assigned to the same group,

Weight may be given to the pilot to satisfy.

As described above, according to the present invention, a packet transmission method divides subcarriers for a long symbol into an odd index subcarrier group and an even index subcarrier group, allocates a pilot to one group, and assigns 0 to another group to convert to a time domain. By allowing the long symbols to have the same absolute value at regular intervals of the time-domain index, it is possible to prevent a problem caused by impulsive noise in packet transmission, thereby improving the performance of the system.

When the two long symbols constituting the packet are sequentially converted to the time domain and transmitted to the receiver, the plurality of data symbols constituting the packet are also sequentially converted to the time domain and transmitted to the receiver. Subcarriers for data symbols may be divided into two groups and then converted into a time domain to be transmitted. This will be described with reference to FIG. 7.

7 is an operation flowchart for a packet transmission method according to another embodiment of the present invention, and is an operation flowchart for data symbols.

Referring to FIG. 7, the packet transmission method divides a plurality (N) of subcarriers for a data symbol into two groups of subcarriers (S710).

Here, a method of dividing subcarriers for data symbols into two groups may vary, but it is preferable to divide the two subcarriers for long symbols in the same manner. That is, when subcarriers for long symbols are divided into groups of even index subcarriers and groups of odd index subcarriers, subcarriers for data symbols are also divided into groups of even index subcarriers and groups of odd index subcarriers.

Data to be transmitted is allocated to any one of the two subcarriers of the separated two groups, and 0 is allocated to the other one (S720).

In this case, data and 0 may be allocated to the same group of all data symbols constituting the packet, and a group to which data and 0 are allocated may be different according to the position of the data symbol. The method may vary according to a method of assigning a pilot and zero to a long symbol.

For example, when a pilot is assigned to a group of even-index subcarriers and two zeros are assigned to a group of odd-index subcarriers, the data is stored in the even-index subcarrier group of data symbols for all data symbols. And 0 for an odd index subcarrier group.

As another example, when a pilot and 0 are allocated to different groups of two long symbols, data and 0 may be allocated to the same group of all data symbols, and the groups to which data and zero are allocated differ according to the position of the data symbol. You may.

If data and 0 are allocated to the two separated groups, a predetermined weight is given to the data (S730).

At this time, the weight applied to the data may have a different value depending on the modulation scheme. For example, weights applied to data may vary according to data modulation schemes such as BPSK, quadrature amplitude modulation (QAM), and quadrature phase shift keying (QPSK).

The data symbols given the weight to the data are converted into the time domain, and the data symbols converted into the time domain are transmitted to the receiver (S740 and S750).

Here, the data symbols may be converted to the time domain by the IFFT.

At this time, the data symbols allocated to the group of even-index subcarriers and 0 assigned to the group of the odd-index subcarriers can be converted to the time domain by Equation 3 below.

을 만족하는 값인 것이 바람직하다. Here, (m) denotes a position of a data symbol, β denotes a weight, X _k denotes data to be transmitted, and x _n denotes a data symbol converted into a time domain, β denotes an average transmission As a factor that determines the strength,

It is preferable that the value satisfies.

을 만족하는 것을 알 수 있다. 즉, 짝수 인덱스 부반송파의 그룹에 데이터가 할당된 데이터 심볼은 시간 영역에서 시간 영역 인덱스 N/2을 주기로 동일한 절대값과 위상을 가진다. 물론, 홀수 인덱스 부반송파의 그룹에 데이터가 할당된 데이터 심볼은 시간 영역에서 시간 영역 인덱스 N/2을 주기로 동일한 절대값과 180도의 위상차를 가질 수 있다는 것은 상술한 롱 심볼에 대한 <수학식 2>를 통해 알 수 있다.As shown in Equation 3, the data symbol converted to the time domain

It can be seen that satisfactory. That is, a data symbol assigned data to a group of even index subcarriers has the same absolute value and phase in a time domain with a time domain index N / 2. Of course, data symbols allocated to groups of odd index subcarriers may have the same absolute value and a phase difference of 180 degrees in a time domain index N / 2 in the time domain. This can be seen through.

Like long symbols, data symbols have the same absolute value in a certain period of time-domain indexes in the time domain, so that even if a receiver receives a packet whose data is broken due to impulsive noise, data in another region having the same value is used. To restore the desired data. Therefore, there is no need to provide a separate method for recovering broken data, thereby reducing the load on the receiver and minimizing the effects of impulsive noise, thereby eliminating the problems that may be caused by impulsive noise. It can prevent and further improve the performance of the system.

The multi-carrier-based packet transmission method according to the present invention for reducing the influence of impulsive noise can be modified and applied in various forms within the scope of the technical idea of the present invention and is not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the spirit of the present invention, it is not limited to the embodiments and the accompanying drawings. And should be judged to include equality.

1 shows an example for measurement based impulsive noise.

2 shows a communication system for explaining a packet transmission method according to an embodiment of the present invention.

3 shows a multi-carrier based packet structure.

4 is a flowchart illustrating a packet transmission method according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating an embodiment of step S410 illustrated in FIG. 4.

6 is a flowchart illustrating a packet transmission method according to another embodiment of the present invention.

7 is a flowchart illustrating a packet transmission method according to another embodiment of the present invention.

Claims (21)

In the multi-carrier-based packet transmission method comprising a plurality (N) of subcarriers, Separating the subcarriers for the long symbol into two groups of subcarriers; Allocating a preset pilot to one of the two subcarriers separated from each other and allocating zero to the other one; Converting the long symbol into a time domain; And Transmitting the long symbol converted to the time domain to a receiver Packet transmission method comprising a. The method of claim 1, The two groups And a group of an odd index subcarrier among the subcarriers and an even index subcarrier among the subcarriers. The method according to claim 1 or 2, The long symbol is Including a first long symbol and a second long symbol, The pilot or zero is A packet transmission method allocated to the same group of the two long symbols. The method of claim 3, Separating the subcarriers for a data symbol into the two groups of subcarriers; Allocating data to a group to which the pilot is allocated among the two groups for the data symbol, and allocating the zero to the remaining group; Converting the data symbols into a time domain; And Transmitting the data symbol converted to the time domain to the receiver Packet transmission method further comprising. The method of claim 4, wherein Assigning a predetermined weight to the data More, And transmitting the data symbol given the weight into the time domain. The method of claim 5, The weight is A packet transmission method set differently according to a modulation method. The method according to claim 1 or 2, The long symbol is Including a first long symbol and a second long symbol, The pilot or zero is A packet transmission method allocated to different groups of the two long symbols. The method of claim 7, wherein Separating the subcarriers for a data symbol into the two groups of subcarriers; Allocating data to either of the two groups for the data symbol and allocating the zeros to the remaining groups; Converting the data symbols into a time domain; And Transmitting the data symbol converted to the time domain to the receiver Packet transmission method further comprising. The method of claim 8, The data symbol is Plural number The allocation group of the data and the allocation group of 0 are The packet transmission method of the same or differently set to the plurality of data symbols. The method of claim 8, Assigning a preset weight to the data More, And transmitting the data symbol given the weight into the time domain. The method of claim 10, The weight is A packet transmission method set differently according to a modulation method. The method according to claim 1 or 2, The converting step A packet transmission method for converting the long symbol from the frequency domain to the time domain using an inverse fast fourier transform (IFFT). The method according to claim 1 or 2, Giving a preset weight to the pilot More, And transmitting the long symbol given the weight into the time domain. The method according to claim 1 or 2, The preset pilot is A method of transmitting a packet, which is a pilot modulated with a binary phase shift key (BPSK). In the multi-carrier-based packet transmission method comprising a plurality (N) of subcarriers, Allocating preset packet data or zero to each of the subcarriers for the symbol such that a symbol constituting the packet has the same absolute value at a constant period of a time domain index in the time domain; Converting the symbol into a time domain; And Transmitting the symbol converted to the time domain to a receiver Packet transmission method comprising a. The method of claim 15, The assigning step And assigning the packet data or the zero to have the same phase as the same absolute value or a phase difference of 180 degrees with the same absolute value. The method according to claim 15 or 16, Separating the subcarriers for the symbol into a plurality of groups More, The assigning step And a packet transmission method of allocating the packet data or the zero to each of the plurality of groups. The method of claim 17, The separating step is A packet transmission method for separating an odd index subcarrier from among the subcarriers and an even index subcarrier from among the subcarriers. The method according to claim 15 or 16, The symbol is A packet transmission method comprising at least one of a long symbol and a data symbol. The method of claim 19, The packet data is Includes a preset pilot, The assigning step The packet transmission method of allocating the pilot or the zero in the case of the long symbol. The method of claim 19, The packet data is Contains the data you want to transfer, The assigning step The packet transmission method of allocating the data or the zero when the data symbol is used.

Images