WO2017065531A1

WO2017065531A1 - Communication method and apparatus using g-ofdm for high speed wireless communication

Info

Publication number: WO2017065531A1
Application number: PCT/KR2016/011505
Authority: WO
Inventors: 김명섭; 성진숙
Original assignee: 주식회사 투니텔
Priority date: 2015-10-13
Filing date: 2016-10-13
Publication date: 2017-04-20

Abstract

The purpose of the present invention is to provide a communication method and apparatus using G-DFDM, the method simultaneously executing a filter bank (FB) method, which reduces inter-channel interference by improving OFDM technology which is the present fourth generation wireless communication technology, and a method in which a plurality of layer channels are superposition multiplexed on the same frequency band using a layer composite function and then transmitted to dramatically enhance frequency allocation and effectiveness.

Description

Communication method and device using G-OFDM for high speed wireless communication

The present invention relates to a communication method and apparatus using generalized OFDM (hereinafter, referred to as 'G-OFDM'). The present method is applicable to both wired and wireless communication, but since the wired communication method is well known, the wireless communication method will be described.

Wireless communication refers to the transmission and reception of various information such as voice and video without using a physical wire by using a radio wave. Radio waves are a part of electromagnetic waves that can transmit information at the speed of light and can be used for wireless communication because they can pass through most solids, vacuums, and atmospheres. Radio waves may be divided into various bands according to wavelengths or frequencies. As the classification according to the wavelength length, there are classifications such as long wave, medium wave, and short wave. Specifically, for example, UHF is used for TV and digital TV broadcasting, VHF is used for FM radio broadcasting, TV broadcasting, remote control, etc., and short wave is used for police, aircraft radio, and the like. Is used for AM radio broadcasting, and longwaves are used for different fields such as coastal and ship radio broadcasting.

Apart from the different application ranges for each wavelength, a method using a frequency has been used so that various communications simultaneously within one application range for each wavelength can be distinguished from each other. Specifically speaking, when a pair of people A-B talks on the phone wirelessly, that is, voice data is transmitted between the A-Bs using wireless communication. At the same time, if a telephone call should be made between another pair of people C-D, wireless communication between A-B and wireless communication between C-D should be distinguished. In this case, the radio communication between the AB is made of a radio wave having an 800 MHz frequency (for example), and the radio communication between the CD is made a radio wave having an 810 MHz frequency (also, for example). Wireless communication can be transmitted separately without mixing.

As described above, in wireless communication, it is essential to be able to discriminate several simultaneous communications from each other, and it is important to efficiently discriminate each communications and to efficiently operate a large amount of simultaneous communications.

As described above, in order to discriminate several communications simultaneously in wireless communication, a method of appropriately dividing frequency bands has been used. In the past, when the amount of wireless communication usage was not large, frequency bands were very simple as in the above-described example. Splitting and assigning did not cause a big problem. However, as the generalization trend of wireless communication has been rapidly accelerated and the number of wireless telephone users has increased exponentially, studies have been steadily made to more efficiently allocate and allocate frequency bands.

Frequency division schemes include FDMA, TDMA, CDMA, and, most recently, OFDM. FDMA is the frequency division scheme used at the earliest, and it literally divides frequency bands among users. However, as the number of concurrent users increases, the frequency bands that can be allocated become narrower, resulting in increased noise and lowered communication quality. The way to solve this problem is TDMA, which was called 2G in the wireless telephone market. In TDMA, all frequency bands are used by one person at a time, but when users increase, several users alternately use them (that is, with time difference). On the other hand, it was developed and used at a similar time as TDMA, and a more advanced method, CDMA, was called 3G. In CDMA, all frequency bands are used by all users at all times for all time, but the signals of each user are differentiated by multiplexing using random numbers assigned to each user.

Orthogonal frequency division multiplexing (OFDM) is a technology that makes these existing technologies more efficient, and is called OFDM-TDMA, OFDM-CDMA, etc. depending on which technology is combined. OFDM is a frequency orthogonal technique, in which multiple pieces of data are put in parallel on a carrier frequency at regular orthogonal intervals and transmitted simultaneously. In the case of the FDMA scheme, in order to avoid interference between adjacent frequencies, some margins have to be given between the frequency bands used for actual communication. However, when the OFDM scheme is applied, even if overlapping frequencies do not cross each other, interference does not occur. There is no need to provide the frequency and the frequency band allocation and distribution becomes much more efficient. Various specific techniques utilizing such OFDM are disclosed in Korean Patent Laid-Open Publication No. 2006-0116019 ("Method for superimposing multi-carrier and direct sequence spread spectrum signals in a broadband wireless communication system", November 13, 2006), Korean Patent Publication No. 2008 -0090031 ("Transmission apparatus and method in orthogonal frequency division multiplexed communication system", 2008.10.08) and the like. The OFDM scheme is efficient in frequency band allocation and is actively used because of its strong multipath characteristics.

Meanwhile, in the conventional OFDM transmission scheme, a guard interval (GI) is inserted to remove inter-symbol interference by multiple paths. If there is no signal in the GI interval, the orthogonality of the subcarriers may be collapsed and inter-channel interference may occur. In order to prevent this, a part of a signal behind the symbol period is copied and inserted, and this signal is a cyclic prefix (CP). However, this CP is a factor that reduces the transmission efficiency, and this method also interferes with neighboring channels because the signal level between neighboring channels is only 13.6 dB difference. In addition, it interferes with neighboring frequency bands, and thus puts a guard band in the use of frequency, thereby decreasing efficiency in using the frequency.

The technology introduced to improve this disadvantage is the FBMC (filter bank multicarrier) technology, which does not interfere with neighboring channels except for a minimum transmission band, generates little leakage power between bands, and requires no CP. This makes it possible to use the frequency more efficiently. The details of OFDM, FBMC, comparison between each technique, and the pros and cons of "FBMC (Filter Bank Multicarrier) transmission technology trend" (Korea Communications Agency, Broadcasting Technology Issues & Outlook, 2014 No. 61, 2014.03. 03) and the like in detail. On the other hand, the FBMC technology has a problem that the prototype filter is very large and the implementation complexity is very large, which causes a lot of power consumption when developed as a device, which is not suitable for commercialization. Doing.

The use of wireless communication is expected to increase exponentially thereafter, and even if the above-described methods are used, the usage of the wireless communication is not expected to be sufficiently covered. Therefore, it is urgent to develop a more efficient frequency use method.

[Preceding technical literature]

[Patent Documents]

1. Korean Patent Publication No. 2006-0116019 ("Method for superimposing multi-carrier and direct sequence spread spectrum signals in a wideband wireless communication system", November 13, 2006)

2. Korean Patent Publication No. 2008-0090031 ("Transmission Device and Method in Orthogonal Frequency Division Multiplexed Communication System", 2008.10.08)

[Non-Patent Documents]

1. "FBMC (Filter Bank Multicarrier) Transmission Technology Trend" (Korea Communications Agency, Broadcasting Technology Issues & Prospects, 2014 No. 61, 2014.03.03)

In the communication method using G-OFDM for achieving the above object, there are a plurality of hierarchical channels defined by a predetermined frequency band, so that digital data is carried for each hierarchical channel, Corresponding and defined as a function in the frequency domain, a plurality of layer channels are superimposed and multiplexed by a plurality of layer synthesis functions having orthogonality and frequency cutoff, and each layer channel is transmitted to a plurality of subchannels. Characterized in that it is formed to be divided. In this case, each frequency band of the plurality of hierarchical channels formed for each of the subchannels is formed to be identical to each other for all the hierarchical channels (that is, physically completely overlapped).

In more detail with respect to the hierarchical function, in the communication method, a matrix composed of a plurality of the hierarchical synthesis functions is a composite matrix, and a matrix composed of hierarchical separation functions corresponding to each of the plurality of hierarchical synthesis functions is called a separation matrix. , The composite matrix and the separation matrix has a hierarchical function matrix (

), The hierarchical matrix ( ) Is formed such that the following formula holds.

At this time, the hierarchical function matrix (

) Is a matrix having a column length of 1 and having orthogonality between columns.

) Is determined; Jump elimination matrix for subtracting the first row from each row to avoid frequency spreading or leakage due to jumps at the starting point.

) Is the initial matrix (

Multiplied by; To achieve column smoothing, the filtering matrix (

) Is the jump removal matrix (

) And initial matrix (

) Times (

Multiplied by; To regain orthogonality,

Filtering matrix by

), Jump removal matrix (

) And initial matrix (

) Times (

) Is converted to a hierarchy function matrix (

) Is generated;

,

It may be made, including.

In addition, the communication method, the initial matrix having an even column length And jump matrix

Hierarchical Function Matrix Created with

Or an initial matrix with odd column lengths

And jump matrix

Hierarchical Function Matrix Created with

It is characterized by using the first column of as a pilot vector.

(At this time,

Initial matrix with even column lengths

Is defined as:

Jump matrix with even column length

Is defined as:

Initial matrix with odd columns length

Is defined as:

Jump matrix with length of odd columns

Is defined as

)

In addition, in the communication method of the present invention, data of a digital signal is converted into a waveform signal and transmitted through a plurality of the hierarchical channels, and the data carried in each of the hierarchical channels is transmitted in a frequency domain using the hierarchical synthesis functions. Frequency overlapping and transmitting, converted into superposition and time domain signals and then transmitted on one communication channel; After the data in the form of a waveform signal transmitted by the frequency overlapping and transmitting step is received and converted from a time domain signal to a frequency domain signal, each hierarchical channel using hierarchical separation functions corresponding to the hierarchical synthesis function And a frequency separation and reception step, in which the data in the digital signal contained in the field is separated and restored.

In addition, at least one modulation selected from BPSK, QPSK, M-PSK, and M-QAM (where M = 2 ^N , N = 1, 2, 3, ...) when the data is loaded on each of the subchannels. The modulation scheme used for each of the hierarchical channels may be the same or different from each other.

In addition, the communication device using the G-OFDM of the present invention is characterized in that the communication device using the communication method as described above.

According to the present invention, there is a great effect that can significantly reduce the interference between the channels by using the frequency band overlapping. More specifically, in the present invention, unlike the conventional method of converting a digital symbol into a waveform signal using a modulation technique through a communication channel in data communication, the transmitter uses a hierarchical synthesis function to transmit a symbol of several hierarchical channels. Is transmitted in the frequency domain by shaping and superimposing, and the receiving side separates the original hierarchical channel symbol from the superimposed signal by using the hierarchical separation function. Accordingly, unlike the conventional one having to allocate one unique frequency band for one user, the G-OFDM of the present invention can efficiently reduce frequency interference by sending data symbols superimposed. Faster than Nyquist (FTN), which is currently being actively studied, is very difficult to achieve synchronization between transmission and reception due to severe interference between symbols. While the implementation complexity is high, the present invention is a technique of overlapping symbols using a function having a property (e.g. orthogonality) that can be separated from each other, so that it is incomparably simpler than that of the FTN technique, so that the implementation or operation of the system is much more complicated. There is also a big advantage of ease and economy. Of course, a function having properties that can be synthesized and interpreted may occur in a large number within a mathematically finite interval. However, the number of functions to be technically implemented should be appropriately limited according to the complexity.

In other words, according to the present invention, the existing frequency interference problem can be solved by using the G-OFDM technology, and it is expected to be a very useful technology as the next generation communication technology as well as the next generation.

1 is a conventional OFDM communication scheme principle.

2 illustrates an example of overlapping and separating two layer channels using the G-OFDM technique of the present invention.

3 illustrates an example in which a plurality of hierarchical channels consisting of one subchannel are synthesized and separated using the G-OFDM technique of the present invention.

4 is a communication method principle using the G-OFDM technique of the present invention.

5 illustrates oversampling.

6 is a transmitter structure implementing frequency overlapping and transmitting steps.

7 illustrates a receiver architecture for implementing frequency separation and reception steps.

8 is a structure of a transmitter and a receiver using the G-OFDM technique of the present invention.

9 is a process of generating a hierarchical matrix having orthogonality and frequency blocking.

10 is a set of hierarchical synthesis functions in the time domain of G (8,6) -OFDM.

11 is a frequency response characteristic of the hierarchical synthesis function of G (8,6) -OFDM.

12 is a power frequency density composed of a hierarchical synthesis function of OFDM and G (8,6) -OFDM.

13 is a set of hierarchical synthesis functions in the time domain of G (7,5) -OFDM.

14 is a frequency response characteristic of the hierarchical synthesis function of G (7,5) -OFDM.

15 is a power frequency density consisting of a hierarchical synthesis function of OFDM and G (7,5) -OFDM.

Hereinafter, a communication method and apparatus using G-OFDM according to the present invention having the configuration as described above will be described in detail with reference to the accompanying drawings.

1 conceptually illustrates a conventional OFDM communication scheme principle. Previously, the conventional TDMA (2G), CDMA (3G), etc. has already described that a single user uses the frequency (f) of all bands. On the other hand, in the OFDM scheme, rather than carrying a single signal over the entire frequency band, the allocated frequency band is divided into subchannels consisting of several small frequency bands as shown in FIG. Subchannel 1, subchannel 2, ... '). At this time, one subchannel occupies one information symbol. 1, symbol 1 transmits and receives using the frequency of subchannel 1, symbol 2 transmits and receives using the frequency of subchannel 2, and the like.

Here, the symbol refers to the smallest unit of data sent at a time in data communication. For example, in the case of the 4-PSK modulation scheme, four types of 1, j, -1, and -j are used at one time. In this case, two bits of information can be sent at a time, and one symbol can be thought of as almost two bits. Types of modulation schemes include BPSK, QPSK, M-PSK, M-QAM, and the like, and since the modulation schemes are widely known in the art, detailed descriptions thereof will be omitted.

In the past, data was transmitted and received on one channel including a plurality of subchannels. That is, according to the conventional method, only one information symbol could be carried on one subchannel. On the other hand, in the present invention, by using a hierarchical synthesis function in the frequency domain, a plurality of hierarchical channels composed of a plurality of subchannels are overlapped. That is, by allowing a plurality of information symbols to be carried on one subchannel (by overlapping a plurality of hierarchical channels), it is possible to obtain an effect of significantly reducing frequency interference compared to the conventional one. The overlapping scheme in the frequency domain in the present invention is referred to as 'generalized orthogonal frequency division multiplexing (G-OFDM)'.

FIG. 2 conceptually illustrates an example of overlapping and separating two hierarchical channels using the G-OFDM technique of the present invention. It is the same to divide the entire frequency band into smaller bands of subchannel 1, subchannel 2, ..., where the subchannels do not have to be the same size range as each other. It is shown an example in which the size of each is formed differently. In the present invention, the signal carrying the symbol of the hierarchical channel 1 on the sub-channel 1 and the signal carrying the symbol of the hierarchical channel 2 are overlaid in the frequency domain by using the hierarchical synthesis function. Send. That is, the superimposed symbol 1 is carried on subchannel 1 and the superimposed symbol 2, ... on subchannel 2 in the transmitted signal. The receiving side receives the overlap symbol 1 on the subchannel 1, receives the overlap symbol 2 on the subchannel 2, and receives the overlap symbols in the process of ..., the overlap symbol 1 by using a layer separation function for each subchannel By splitting, symbols 11 and 21 are obtained, and the original symbols are separated by the process of.

That is, in the present invention, by superimposing and separating information symbol signals using hierarchical synthesis and analysis functions in the frequency domain, a plurality of symbols are stored in one band, unlike in the past, only one symbol can be sent to one subchannel. Allow them to be nested and sent. Accordingly, according to the present invention, the same frequency band can be efficiently controlled, and the interference can be significantly reduced. As described above, the wireless communication method of the present invention can contribute to substantially increase communication capacity by reducing frequency interference between systems.

To conceptually summarize the wireless communication method of the present invention as described above, in the wireless communication method of the present invention, there are a plurality of hierarchical channels defined in a predetermined frequency band, so that digital data is carried for each hierarchical channel. In this case, the plurality of layered channels are overlapped and multiplexed by a plurality of layered synthesis functions corresponding to the plurality of layered channels and defined as functions in the frequency domain. In this case, each of the hierarchical channels is formed to be divided into a plurality of subchannels, so that data can be carried more efficiently. In this case, each frequency band of the plurality of subchannels formed for each of the hierarchical channels is formed to be the same for all the hierarchical channels. Accordingly, as described above, unlike the conventional case, only one information symbol may be transmitted and received on one subchannel, and in the present invention, one subchannel may transmit and receive as many information symbols as the number of hierarchical channels. It can be.

To describe the wireless communication method of the present invention in more detail, the wireless communication method of the present invention is composed of a frequency overlapping and transmitting step and a frequency separation and reception step.

In the frequency overlapping and transmitting step, data of a digital signal through a plurality of hierarchical channels is converted into an analog signal and transmitted (where the hierarchical channels are defined as predetermined frequency bands, and a plurality of subchannels as shown). And the entire band and each subchannel band are the same for each layer channel). At this time, the data carried on each of the hierarchical channels are converted into overlapping and time-domain signals in the frequency domain using the hierarchical synthesis functions and then transmitted on one communication channel.

In the frequency separation and reception step, the data in the form of an analog signal transmitted by the frequency overlapping transmission step is received and converted from a time domain signal into a frequency domain signal, and then using hierarchical separation functions corresponding to the hierarchical synthesis function. Thus, the data of the digital signals carried on the respective hierarchical channels are separated and restored.

Hereinafter, the frequency overlap principle, which is the main principle of the present invention, will be described first, and then, a specific embodiment of applying the frequency overlap principle to an actual digital communication system will be described.

■ 주파수 중첩 원리■ Frequency superposition principle

3 conceptually illustrates a principle of transmitting and receiving information symbols of a plurality of hierarchical channels in one subchannel using the G-OFDM technique of the present invention.

In order to explain the principle of the present invention, an orthogonal waveform is used as an example of the hierarchical synthesis function. Orthogonal functions in the frequency domain have the following properties:

(One)

here

And the like represent pulses in the frequency domain,

Is all

Bandwidth,

Is a mistake. Information symbol

When we say

Information symbols may be synthesized as follows.

(2)

like this

Information symbols

In the frequency domain with overlapping signals

Can be expressed as follows through an inverse Fourier transform.

(3)

In fact, through the communication channel, the signal shown in (3)

Is sent. Information symbol

Is a pulse in the frequency domain

Is a pulse in the time domain corresponding to

Will be sent on. However, when channel noise is introduced into such a signal, it may appear as follows.

(4)

here

Is a noise signal. To extract the information symbol from this signal, the following procedure is performed. First signal

Fourier transforms

(5)

Fourier-Transformed Frequency Domain Signal

about,

The integral is performed as follows by the second pulse.

(6)

here

silver

Noise component introduced to the first channel. Information symbol

Is estimated as follows.

(7)

here

Is the logic for determining the information symbol. In this way, the principle that the information can be received even if the overlapping frequency is sent.

■ 디지털 통신 시스템으로의 주파수 중첩 원리 적용■ Application of frequency superposition principle to digital communication system

In the foregoing description of the principle of frequency superposition, a principle of sending a plurality of hierarchical channel information symbols to one subchannel has been described. However, to realize the principle of frequency superposition, much more information symbols should be transmitted. To do this, as shown in FIG. 2, the hierarchical synthesis function is used to superimpose several hierarchical channels, but by placing a plurality of subchannels in one hierarchical channel, more data can be transmitted.

4 conceptually illustrates a principle of transmitting a large amount of data to a channel having a plurality of subchannels using the G-OFDM technique of the present invention. 4 and the like, each step (frequency overlapping and transmitting step, frequency separation and reception step) of the wireless communication method of the present invention will be described in more detail with a specific embodiment for applying to an actual communication system.

주파수 중첩 다중화 및 송신 단계Frequency Overlap Multiplexing and Transmission Steps

First, the input data string to be transmitted in digital form (

) Is used by symbol channel mapper

) And by subchannel (

Indexed on the complex plane symbol (

). This can be explained as follows. Data to be transmitted in a digital communication system is in digital form. These input data columns (

) Modulates through a baseband modulator called a symbol mapper. Modulation methods can be applied to all baseband digital modulation methods, such as BPSK, QPSK, M-PSK, M-QAM.

First layer channel,

Symbol mapping for the first subchannel may be expressed as follows.

(8)

Symbol mapping is

Collection of data bits on the first subchannel

Symbol on complex plane

It acts as a mapping.

Next, the symbol of each channel (

)this

The double oversampling results in an oversampling signal (

To be converted to).

Pear oversampling between symbols

This can be achieved by inserting zeros. 5 is

This is an example of four oversampling.

Next, the oversampling signal of each layer channel (

) Is an orthogonal function (

By convolution in the frequency domain

To be molded). At this time, the orthogonal function (

) Is equal to the number of the hierarchical channels, and the orthogonal function (

) Corresponds to the hierarchical synthesis function in the earlier explanation. Incidentally, as described above, if hierarchical overlap and separation can be performed, any function may be used as the hierarchical synthesis function, but since it is an orthogonal function that can be easily implemented most intuitively, only an orthogonal function is used in this embodiment. As a matter of course, a hierarchical composition function may be applied instead of an orthogonal function. The condition that the hierarchical synthesis function should have is a measurement analysis function for separating the hierarchical channel, and the function represented by the product of the synthesis function and the analysis function as a whole may be orthogonal.

(9)

The oversampling signal shaped in this frequency domain (

) That is, the molding signal (

) Can be separated for each channel at a later stage by a hierarchical separation function, which will be described later, using orthogonality with a hierarchical synthesis function in a neighboring channel.

The oversampling signal (

) And the orthogonal function (

The convolution process in the frequency domain of) is described in more detail as follows. First, the hierarchical synthesis function can be expressed as Equation (10).

10

In addition, shaping filtering by the hierarchical synthesis function is based on the length of the input data vector

And parameters

Total sample length by

This means that it is circularly convolved so that circular convolution is obtained as follows.

(11)

Thus obtained

The length of

to be.

You can get a circular convolution by nesting

(12)

Next, the shaping signal of each hierarchical channel (

) Are added to elements by element and then vector mixed so that one superimposed signal (

). This operation can be expressed as:

(13)

This represents adding up the outputs of the two hierarchical channels.

Next, the overlap signal (

) Is transformed from a frequency domain signal to a time domain signal by an inverse Fourier transform, so that a transmission signal in the form of an analog signal (

Let).

(14)

In equation (14)

Denotes an inverse Fourier transform operator.

Finally, the transmission signal (the analog signal in the time domain)

) Is transmitted on one said communication channel. 6 illustrates a transmitter structure for implementing the frequency overlapping and transmission steps as described above.

주파수 분리 및 수신 단계Frequency Separation and Receive Steps

First, the transmission signal transmitted through the communication channel (

) And the noise signal introduced into the communication channel (

) Combined with the received signal (

) Is received (see equation (15)). Ideally, the transmission signal transmitted in the spectral overlap and transmission steps should be received as it is, but noise is almost always introduced in the actual communication environment. In view of this, it is assumed that the received signal includes a noise signal as well as a transmitted signal. As shown in equation (15), the transmission signal (

), Noise signal (

), Incoming signal (

) Are all in vector form.

(15)

Next, the received signal (

) Is transformed from a time domain signal into a frequency domain signal by a fast Fourier transform (FFT) to convert the transform signal (

Let). Such an operation is expressed as follows.

(16)

Next, the conversion signal (

) Is the layer separation function (

Separate signal for each layer channel in the form of digital signal convolved in the frequency domain by

To be separated.

(17)

The hierarchical separation function corresponds to the hierarchical synthesis function used in the overlapping step, and as described above, the function represented by the product of the synthesis function and the analysis function is determined to have orthogonality. In other words, the relationship between the synthesis function h and the analysis function g is as follows.

(18)

Next, the separation signal (

)from

Signal before conversion, which is the signal at the point where

) Is saved. In other words, during the frequency overlap and transmission

It is to return the signal that had been oversampled to its original form.

(19)

Finally, the pre-conversion signal (

Symbol decision logic (

) Is applied to the output data string for each layer channel (

) Is restored.

20

7 illustrates a receiver structure for implementing the frequency separation and reception steps as described above.

■ 계층합성함수 및 계층분리함수 생성 예시■ Example of Creating Hierarchical Synthesis Function and Hierarchical Separation Function

As described above, in the wireless communication method of the present invention, data for each layer channel is overlapped in a frequency domain by using layer synthesis functions. These hierarchical synthesis functions should be excellent in frequency cutoff characteristics while being waveforms having properties that can be separated from each other (eg, orthogonality). For example, the Hadamard matrix has excellent orthogonality but no frequency blocking capability, and thus is not suitable for application to the communication method of the present invention.

In the present invention, a new layer synthesis function and a layer separation function satisfying orthogonality and frequency blocking property are proposed. An example of making such a function is described below, but enumerating each layer function is not very effective, so we introduce a matrix to discuss the orthogonality and frequency blocking characteristics of each column.

(21)

Hierarchical Function Matrix

The process of making is shown in FIG. 9. The structure of the synthetic matrix and the separation matrix is the same. Hierarchical Function Matrix

Is obtained by the following equation.

(22)

here

Is the initial matrix,

Silver jump removal matrix,

Is a filtering matrix for column smoothing of the matrix. Each function can be expressed as follows.

(23a)

(23b)

(23c)

matrix

Wow

Are transform matrices from the frequency domain to the time domain and from the time domain to the frequency domain, respectively. matrix

Wow

Each removes jumps in columns in the matrix and performs filtering in the time domain.

In the following, the initial matrix

Hierarchical Function Matrix Starting with

It will be described in more detail that the process of deriving finally appears as Equation (22).

Initial matrix

Is related to the length of the column needed to transfer data, and its shape is different when it is even and odd. A common feature is that columns are 1 in length and are orthogonal between each column.

The length of the column is even,

When this is even, the initial matrix has the form

(24)

The length of the column is odd, that is

When this is odd, the initial matrix has the form

(25)

Also, as can be seen from equations (24) and (25), the fact that most of the matrix elements are zero is to achieve the goal with the minimum operation when there is another matrix and operation. The portion of space is zero, and all of the center rows of equation (25) are zero.

Now these matrices

We have to process it to have the properties we want, but it is not easy to have that intuition in the frequency domain. This is because they are used to signal processing in the time domain rather than in the frequency domain. So first

Let's switch to the time domain.

In order to convert to the time domain, the matrix column is expanded and zero padded to the required size. The matrix required for permuting and zero padding is defined as follows.

(26)

The permute and zero-padded matrix can be expressed as

(27)

matrix

IFFT is performed on each column to convert to the time domain.

(28)

here

Is represented by equation (29),

to be.

(29)

matrix

Since the first rows of are all 1's, the first row of the matrix transformed by IDFT can be written as

(30)

Spectral spreading occurs in OFDM because each carrier function has a sharp jump at its starting point. In other words, spectral spreading or leakage occurs due to a jump that contains a lot of high frequencies at the starting point. So we can eliminate this jump by subtracting the first row from each row. The mathematical expression of this is as follows.

(31)

here

The matrix

It acts as an operator to remove jumps from the column.

The matrix may be transformed into the frequency domain by taking a DFT on the columns of. Mathematically, we can write

(32)

matrix

Most of are 0 and are not required for the operation. Therefore, permutation and truncation can reduce the matrix without loss of information, and can be expressed mathematically as follows.

(33)

Meanwhile, a method of eliminating jumps in the columns of the matrix by Equation (31) can be considered variously. When the first row is all zero in the time domain, it means the same as the sum is zero for each column in the frequency domain. Thus, the only way to get rid of a jump is not, but not all of the ways to get rid of it are useful. Criteria for determining whether a jump elimination method is useful will be described later, but will be determined with a variety of frequency characteristics and pilot vectors.

Initial matrix

And intermediate matrix

There is a relationship between:

(34)

here

Is the initial matrix

Matrix by eliminating jumps in columns

It is used as an operator that makes the sum to zero for each column in the table. If this is expressed as an equation, it is as follows.

(35)

When designing a way to eliminate jumps, it is important that the rank of the matrix from which jumps were removed should not be less than the original rank.

First even

Two satisfying equation (35) against

You can define a matrix as

(36a)

(36b)

The sum of each even column of equations (36a) and (36b)

It can be seen that. By subtracting this jump matrix from the original initial matrix, we get a matrix with jumps removed as follows:

(38a)

(38b)

We can see that the sum is zero for each column of these two matrices. From this fact it can be seen that this matrix becomes a jump-free matrix in the time domain.

Next, odd

Two satisfying equation (35) against

You can define a matrix as

(39a)

(39b)

The sum of each odd column in equations (39a) and (39b) is

40a

(40b)

Now, filtering is performed to improve the spectral characteristics of the matrix from which the jump is removed. If this is expressed as an equation, it is as follows.

(41)

here

Is represented by equation (42).

(42)

After filtering, DFT, permutation, and truncation, the filtered matrix can be obtained as follows.

(43)

The initial matrix began with a matrix with orthogonal columns, but may be distanced from the matrix with orthogonal columns while eliminating jumps and performing filtering. Thus, the matrix given by Eq. (43) can be converted into the matrix with the nearest orthogonal column as follows while maintaining its properties.

(44)

here

silver

Hermitian matrix. In this way, the initial matrix is represented by equation (22).

From

Showed that it was created.

There may be many channel paths in the communication path between the transmitter and the receiver. In order to obtain information on such a path, conventional OFDM uses pilot symbols known in advance between the transmitter and the receiver. G-OFDM does not use one subchannel but uses one column in a matrix as a pilot vector.

The process of creating a matrix containing pilot vectors is already an initial matrix.

From

Can be defined the same as the process for creating a. The matrix including the pilot vector must have all the elements of all other vectors corresponding to the rows located in the nonzero elements constituting the pilot vector all zeros.

When this is even, the initial matrix can be defined as

(45)

In addition, jump matrices can be defined as follows.

(46a)

(46b)

When this is odd, the initial matrix can be defined as

(47)

In addition, jump matrices can be defined as follows.

(48a)

(48b)

■ 시뮬레이션 및 결과■ Simulation and Results

Simulation was performed to check whether the frequency cutoff is good when the filter matrix, which is the core of the present invention as described above, is actually applied. That is, to briefly explain the following simulation process, a hierarchical matrix is obtained using an appropriately set initial matrix, a jump matrix, and equation (22), and it is checked whether the first column of the hierarchical matrix can be used as a pilot vector. In general, a reference signal known to both the transmitter and the receiver for channel estimation is called a pilot. If the first column of the hierarchical matrix obtained in the simulation satisfies the conditions described above, It can be determined that it is high and can be used as a pilot vector.

실시예 1: G(8,6)-OFDMExample 1 G (8,6) -OFDM

First, the initial matrix

And jump matrix

From equation (22)

Can be obtained. here

Wow

Are shown in Table 1 (a) and (b), respectively. Table 1 (a), see the (b) that the first time it the second column, the pilot vector, all the elements of the other vector with respect to the first non-zero element is zero, so the first column can be used as the pilot vector It can be seen.

[Table 1 (a)]

[Table 1 (b)]

10 is a matrix

By plotting the columns of in the time domain, we can see that all the curves start at zero and end with zero. This prevents spectral spreading by not drastically changing the function used as a carrier wave. 11 is the matrix

By plotting columns in the frequency domain, it can be seen that the spectral characteristics of each column are different. 12 is a comparison of power spectral density (PSD) between conventional OFDM and G-OFDM according to the present invention. It can be seen from FIG. 12 that the G-OFDM shows very high spectrum use efficiency.

Meanwhile, the initial matrix

And jump matrix

From equation (22)

Can be obtained. here

Wow

Are shown in Table 2 (a) and (b), respectively. Table 2 (a), (b) shows that when the first column is a pilot vector, for the first nonzero element all elements of the other vector are not zero , so the first column cannot be used as a pilot vector. It can be seen.

[Table 2 (a)]

[Table 2 (b)]

실시예 2: G(7,5)-OFDMExample 2: G (7,5) -OFDM

First, the initial matrix

And jump matrix

From equation (22)

Can be obtained. here

Wow

Are shown in Table 3 (a) and (b), respectively. In Table 3 (a) and (b), when the first column is a pilot vector, all elements of the other vector are zero for the first nonzero element, so the first column can be used as a pilot vector . It can be seen.

13 is a matrix

By plotting the columns of in the time domain, we can see that all the curves start at zero and end with zero. This prevents spectral spreading by not drastically changing the function used as a carrier wave. 14 is the matrix

By plotting columns in the frequency domain, it can be seen that the spectral characteristics of each column are different. 15 is a comparison of power spectral density (PSD) of conventional OFDM and G-OFDM of the present invention. It can be seen from FIG. 15 that the G-OFDM shows very high spectrum use efficiency.

[Table 3 (a)]

[Table 3 (b)]

Meanwhile, the initial matrix

And jump matrix

From equation (22)

Can be obtained. here

Wow

Are shown in Table 4 (a) and (b), respectively. In Table 4 (a) and (b), when the first column is a pilot vector, for the first nonzero element all elements of the other vector are not zero , so the first column cannot be used as a pilot vector. It can be seen.

[Table 4 (a)]

[Table 4 (b)]

In view of the above simulation results, in the present invention

from

We have developed a technique that can control orthogonality and spectrum simultaneously. The matrix for implementing the system is not unique, but a useful matrix is the proposed jump matrix.

Wow

It is also confirmed that the matrices can accommodate pilot vectors when using.

The present invention is not limited to the above-described embodiments, and the scope of application of the present invention is not limited to those of ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made.

According to the present invention, the existing frequency interference problem can be solved by using the G-OFDM technology, and it is expected to be a very useful technology as the next generation communication technology as well as the next generation.

Claims

Since there are a plurality of hierarchical channels defined as predetermined frequency bands, digital data is carried for each hierarchical channel.

A plurality of hierarchical channels are respectively overlapped and multiplexed by a plurality of hierarchical synthesis functions corresponding to a plurality of the hierarchical channels and defined as functions in the frequency domain, and having orthogonality and frequency cutoff.

Each of the hierarchical channels is formed to be divided into a plurality of sub-channels.
The method of claim 1, wherein the communication method

Each frequency band of the plurality of subchannels formed for each of the hierarchical channels is formed in the same manner for all the hierarchical channels.
The method of claim 1, wherein the communication method,

When a matrix composed of a plurality of hierarchical synthesis functions is a composite matrix and a matrix composed of a plurality of hierarchical separation functions respectively corresponding to the plurality of hierarchical synthesis functions is called a separation matrix,

The composite matrix and the separation matrix may have a hierarchical function matrix (
),

The hierarchical function matrix (
) Is a communication method using G-OFDM, characterized in that the following formula is established.
The method of claim 3, wherein the hierarchical function matrix
)

A matrix having a length of 1 and having orthogonality between columns, the initial matrix (
) Is determined;

Jump elimination matrix that performs the operation of subtracting the first row from each row to avoid frequency spreading or leakage due to jumps at the starting point.
) Is the initial matrix (
Multiplied by;

To achieve column smoothing, the filtering matrix (
) Is the jump removal matrix (
) And initial matrix (
) Times (
Multiplied by;

To regain orthogonality,
Filtering matrix by
), Jump removal matrix (
) And initial matrix (
) Times (
) Is converted to a hierarchy function matrix (
) Is generated;

,

Communication method using G-OFDM, characterized in that comprises a.
The method of claim 4, wherein the communication method

Initial matrix with even column lengths
And jump matrix
Hierarchical Function Matrix Created with
or

Initial matrix with odd columns length
And jump matrix
Hierarchical Function Matrix Created with

Communication method using G-OFDM, characterized in that using the first column of the pilot vector.

(At this time,

Initial matrix with even column lengths
Is defined as:

Jump matrix with even column length
Is defined as:

Initial matrix with odd columns length
Is defined as:

Jump matrix with length of odd columns
Is defined as

)
The method of claim 1, wherein the communication method

Data of a digital signal is converted into an analog signal and transmitted through a plurality of the hierarchical channels, and the data carried on each of the hierarchical channels is superimposed in the frequency domain using the hierarchical synthesis functions and converted into a time domain signal. Frequency overlapping and transmitting, which are then transmitted in one communication channel;

After the data in the form of an analog signal transmitted by the frequency overlapping and transmitting step is received and converted from a time domain signal to a frequency domain signal, each hierarchical channel using hierarchical separation functions corresponding to the hierarchical synthesis function A frequency separation and reception step of separating and restoring data of a digital signal carried in the field;

Wireless communication method using a G-OFDM comprising a.
The method of claim 1, wherein the communication method

When the data is loaded on each of the subchannels, one modulation method selected from BPSK, QPSK, M-PSK, and M-QAM (where M = 2 N , N = 1, 2, 3, ...) is used. But

Method of communication using G-OFDM, characterized in that the modulation scheme used for each layer channel is the same or different.
A communication device using G-OFDM, characterized in that the communication device using the communication method according to any one of claims 1 to 7.