KR100557830B1 - Resource Allocating Method for OFDM-based Radio Communication System, Transmission Signal Generating Method and Transmitter Using the Same - Google Patents

Abstract

The present invention relates to a resource allocation method for reducing inter-cell interference, that is, noise generated when operating an orthogonal frequency division multiplex (OFDM) wireless communication system, and a transmitter of a multiple access OFDM system.

In general, asynchronous systems are not time-synchronized between base stations. From the receiver's point of view, the transmission OFDM interference signals of neighboring base stations using the same channel frequency band are not matched by discrete Fourier transform (DFT) timing. Even in a synchronous system, the timing is shifted due to the signal propagation delay. In this case, the DFT interval of the receiver increases the probability of simultaneously including the guard interval created by cyclically extending the last portion of the symbol interval and the transition period of the transmission OFDM symbol of the neighboring base station including the last portion of the previous symbol interval. do.

Therefore, when designing a transmission signal, intentionally adjusting the power of the last part of the OFDM symbol copied to the guard interval can reduce the interference noise between cells.

Multiple access OFDM system, intercell interference noise, guard interval, transmission power control

Description

Resource Allocating Method for OFDM-based Radio Communication System, Transmission Signal Generating Method and Transmitter Using the Same

1 is a timing diagram illustrating a comparison between an interference signal of a neighboring base station and a DTF section of a user terminal in order to explain interference noise between cells in a conventional Orthogonal Frequency Division Multiplexing (OFDM) wireless communication system.

2 is a schematic block diagram showing a transmitter of a multiple access OFDM wireless communication system to which the present invention is applied;

3 is a timing diagram illustrating a comparison of power types of interference signals of adjacent base stations for a multiple access OFDM wireless communication system and various DTF intervals of a user terminal to explain a basic principle for reducing inter-cell interference noise according to the present invention;

4A and 4B illustrate an interference noise reduction method through signal design in a frequency domain in OFDM-FDMA according to the first embodiment of the present invention. FIG. 4A is an OFDM-FDMA symbol in the frequency domain. OFDM-FDMA symbol in time domain obtained by IDFT processing OFDM-FDMA symbol in frequency domain of 4a,

5 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a first embodiment implemented according to a signal design in a frequency domain in the OFDM-FDMA shown in FIGS. 4A and 4B;

6 is a resource mapping diagram illustrating a resource allocation scheme for canceling inter-cell interference in an OFDM-FDMA system according to a second embodiment of the present invention;

FIG. 7 is a flowchart of resource mapping for implementing the resource allocation scheme of FIG. 6 in an OFDM-FDMA system. FIG.

8 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a second embodiment for implementing a resource allocation scheme in OFDM-FDMA according to the methods of FIGS. 6 and 7;

9 is a resource mapping diagram showing a WH orthogonal code allocation scheme in a frequency domain in an OFDM-CDMA system according to a third embodiment of the present invention;

10 is a flowchart of resource mapping using a WH orthogonal code for implementing the WH orthogonal code allocation scheme of FIG. 9 in an OFDM-CDMA system;

11 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a third embodiment for implementing a WH orthogonal code allocation scheme in a frequency domain of an OFDM-CDMA system according to the methods of FIGS. 9 and 10; ,

12 is a resource mapping diagram illustrating a Fourier code allocation scheme in a frequency domain according to the present invention in an OFDM-CDMA system according to a fourth embodiment of the present invention;

FIG. 13 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a fourth embodiment for implementing a Fourier code allocation scheme in a frequency domain of an OFDM-CDMA system according to the method of FIG.

* Explanation of Signs of Major Parts of Drawings *

100,300; Interfering signal 102,302; Protection section

104; OFDM symbol interval 106,314,404; The last part of the symbol

108,306-312; DFT interval 200,500,800,1100,1300; transmitter

202,406; User message symbol 204; Mapped signal

206; Time domain signals 208,803,1104,1304; Resource Mapper

210,510,808,1112; IDFT units 212, 512, 810, 1114; P / S converter

214; Circulating extension 216; D / A converter

218; RF transmitter circuit 220; antenna

304,400,402; OFDM symbol 408; Subcarrier

404,410,412; Point 504; X '

502,802,1102,1302; User Message Symbol Generator

514,516; Zero value setter 803c; Selector switch

803a, 803b, 1104a-1104SF, 1304a-1304SF; Multiplier

1108; Summer 1110; S / P conversion unit

The present invention relates to a resource allocation method for an orthogonal frequency division multiplexing (OFDM) wireless communication system, a method for generating a transmission signal using the same, and a transmitter thereof. In particular, an OFDM system is inserted to prevent interference between subchannels during signal transmission in an OFDM system. Resource allocation method for OFDM wireless communication system capable of reducing inter-cell interference noise on same channel of neighboring base station when receiving transmission signal by intentionally reducing power of last part of OFDM symbol copied to guard interval The present invention relates to a transmission signal generating method and a transmitter thereof.

Orthogonal Frequency Division Multiplexing (OFDM) is a system that transmits signals by separating them using orthogonality of frequencies, and is used in DVB (Digital Video Broadcasting) and wireless LAN. The mobile station can reliably receive the additional data service even when moving.

In the OFDM system, since a plurality of subcarriers exist in the entire transmission band and orthogonality is established between different subcarriers, signal separation is possible in the frequency domain. Using this characteristic, the transmitter generates a signal in the frequency domain, generates a transmission signal in the time domain through an inverse discrete Fourier transform (IDFT), and transmits it to a channel. The receiver DFTs the signals in the time domain received through the channel, converts them back into the frequency domain, separates the magnetic signals, and restores the transmitted message symbols.

At this time, interference occurs between orthogonal frequency components due to the delay of the channel, and in order to eliminate the influence of such interference noise, a guard interval 102 between OFDM symbol intervals 104 is conventionally used as shown in FIG. 1. The guard interval 102 is a cyclic extension of the last portion 106 of the OFDM symbol interval 104. The guard interval 102 is copied to the front part of the OFDM symbol interval 104 and transmitted. To form.

In general, asynchronous wireless communication systems are not time-synchronized between base stations. From a receiver's point of view, the transmission OFDM interference signals of neighboring base stations using the same channel frequency band do not match the Discrete Fourier Transform (DFT) timing. In addition, even in a synchronous system, timing is shifted due to propagation delay of a signal.

In this case, the DFT interval of the receiver includes the guard interval 102 created by cyclically extending the last portion of the symbol interval 104 of the transmission OFDM symbol of the neighboring base station and the last portion 106 of the previous symbol interval 104 simultaneously. This becomes large, and the signals included in the sections other than the symbol section 104 act as interference noise.

Meanwhile, an OFDM system may be designed as a system combined with an existing multiple access system to accommodate multiple users. OFDM-TDMA (Time Division Multiple Access), OFDM-FDMA (Frequency Division Multiple Access), and OFDM-CDMA (Code Division Multiple Access) systems are the basic techniques. It is also possible to design a hybrid system in which multiple access systems are combined. In this type of system, inter-cell interference directly affects system capacity, and therefore, a transmission scheme for reducing interference noise between cells is required.

In a wireless communication system, it is very important to maximize the capacity of the system in a given frequency band. In order to increase the capacity of the system with limited frequency resources, spatially separated base stations are reused. In a CDMA system, since the interference noise averaging effect, all base stations can use the same frequency resource. Thus, it can have a high system capacity in a limited frequency resource.

When a multiple access OFDM system is applied to a wireless communication system, a coping technique for inter-cell interference noise is also very important to improve the capacity of the system. As a conventional conventional coping technique known up to now, a technique of spreading by OFDM-CDMA scheme or averaging interference noise by OFDM-FDMA scheme through frequency hopping is known. However, these conventional approaches have not continued to reduce satisfactory intercell interference noise in a growing system environment.

The present invention further proposes a method of reducing interference noise between cells, in addition to the above-described coping technique. As described above, in the OFDM system, a guard period is inserted and transmitted to remove interference noise between subchannels caused by channel distortion, but the guard period itself acts as a factor for reducing signal transmission efficiency. However, if the power of the signal transmitted in the guard interval can be intentionally reduced, it is possible to reduce the interference noise between cells in the multiple access OFDM system.                         

Accordingly, the present invention has been made in view of the problems of the prior art, and its object is to provide the power of the last portion of an OFDM symbol copied to a guard interval inserted to prevent interference noise between subchannels during signal transmission in an OFDM system. The present invention provides a resource allocation method for an OFDM wireless communication system capable of reducing inter-cell interference noise on a same channel of a neighboring base station when a transmission signal is intentionally reduced, a transmission signal generation method using the same, and a transmitter thereof.

Another object of the present invention is to provide a resource allocation method and a transmission signal generating method for an OFDM wireless communication system which can reduce interference noise between cells according to each multiple access scheme.

It is still another object of the present invention to design a resource allocation scheme when each user's symbols are allocated to different subcarriers in an OFDM-FDMA system to statistically reduce the power of the last portion of an OFDM symbol copied to a guard interval in the time domain. The present invention provides a method for allocating a resource and generating a transmission signal for an OFDM wireless communication system capable of reducing interference noise between cells.

Another object of the present invention is to statistically reduce the power of the last part of the OFDM symbol copied into the guard interval in the time domain by selectively allocating a Walsh-Hadamard (WH) orthogonal code assigned to each user in an OFDM-CDMA system. The present invention provides a method for allocating a resource and generating a transmission signal for an OFDM wireless communication system capable of reducing interference noise between cells.

Another object of the present invention is the last of OFDM symbols copied from the time domain to the guard interval by using a Fourier code as an orthogonal code allocated to each user in an OFDM-CDMA system spreading using an orthogonal code in the frequency domain. The present invention provides a method for allocating a resource and generating a transmission signal for an OFDM wireless communication system that can reduce interference noise between cells by statistically reducing power of a portion.

In order to achieve the above object, the present invention is a transmission signal of an OFDM wireless communication system for generating an OFDM transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in the time domain by cyclic extension and inserting it into a guard interval. In the generating method, when the user message symbol is mapped to a subcarrier in the frequency domain, the OFDM wireless communication characterized by allocating resources such that the power of the last part of the OFDM symbol copied to the guard interval in the time domain is as small as possible. Provides a resource allocation method for the system.

와

의 심볼을 할당하는 단계와, 사용자가 k=N/2+m번째에 해당되는 경우 사용자 심볼(

)을 기존에 할당되어 있던 부반송파(

)에 다시 할당하고 부반송파(

)에 할당된 심볼값을

로 바꾸 어 주는 단계로 구성되는 것을 특징으로 한다.In the case of applying the concept of the present invention to an OFDM-FDMA wireless communication system, the resource allocation method sequentially allocates message symbols b _k (where K is the number of users) of each user, so that the user is k≤N / 2th. Each user's message symbol ( b _k ) is divided into two concatenated subcarriers ( f _2k-1 , f _2k ) until applicable.

Wow

Assigning the symbol of < RTI ID = 0.0 > and < / RTI >

) Has been assigned to the subcarrier (

And reassign subcarriers (

Symbol value assigned to

Characterized in that consisting of steps that change to.

)(여기서 K는 사용자 수임)에 대하여 부반송파로서 왈시-하다마드(WH) 직교 코드(W₁,W₂,...,W_SF)(여기서 SF는 확산인자임)의 짝수번째 코드(

)를 먼저 할당하는 단계와, 나머지 사용자의 메시지 심볼에 홀수번째 코드(

)를 할당하는 단계로 구성되는 것을 특징으로 한다.In the case of applying the concept of the present invention to an OFDM-CDMA wireless communication system, a resource allocation method includes a message symbol of each user.

) Is the even-numbered code of the Walsh-Hadamard (WH) orthogonal code (W ₁ , W ₂ , ..., W _SF ) (where SF is a spreading factor) as a subcarrier (where K is the number of users).

) And assign the odd-numbered code (

) Is assigned to the step of assigning.

)(여기서 K는 사용자 수임)에 부반송파로서 푸리에 직교 코드(F₁~F_K)를 순차적으로 할당하는 것을 특징으로 한다.In case of applying the concept of the present invention to an OFDM-CDMA wireless communication system, another resource allocation method includes a message symbol of each user.

(Where K is the number of users), the Fourier orthogonal codes F ₁ to F _K are sequentially assigned as subcarriers.

Meanwhile, a method of generating a transmission signal of an OFDM wireless communication system that can be implemented using the resource allocation method includes mapping a user symbol to a subcarrier in a frequency domain, and performing an inverse discrete Fourier transform (IDFT) on the signal mapped to the subcarrier. Converting a signal in a frequency domain into a signal in a time domain, converting a parallel signal converted into the time domain signal into a sequential serial signal, and converting the serial signal into a quadrature frequency in a time domain by a cyclic extension. Copying the last part of the OFDM symbol and inserting it into a guard interval to generate an OFDM transmission signal, and when mapping a user symbol to a subcarrier in the frequency domain, the end of the OFDM symbol copied to the guard interval By intentionally reducing the power of the part remains the same when receiving the pre-OFDM call Characterized in that the reduction in the influence of the interfering OFDM signal transmitted from the surrounding base stations using a frequency band.

)을 발생하는 단계와, 상기 IDFT 출력(

)과 M개의 제로값(0)을 받아들여서 IDFT 출력(

)의 뒷부분에 M개의 제로값(0)을 삽입함에 의해 시간 영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분의 전력을 제로(0)로 만드는 시간 영역의 OFDM 심볼(

)을 합성하는 단계와, 상기 합성된 시간영역의 병렬신호인 OFDM 심볼(

)을 순차적인 시리얼 신호로 변환하는 단계와, 상기 시리얼 신호를 순환 확장에 의해 시간 영역에서 직교 주파수 분할 다중(OFDM) 심볼의 마지막 부분을 복사하여 보호구간으로 삽입하여 OFDM 전송신호를 생성하는 단계로 구성되어, 상기 OFDM 전송신호를 수신할 때 동일 채널 주파수 대역을 사용하는 주변 기지국으로부터 송신된 OFDM 간섭 신호의 영향을 감소시키는 것을 특징으로 하는 OFDM-FDMA 무선 통신 시스템의 전송신호 생성방법을 제공한다.According to another feature of the invention, the invention provides NMK unused subcarriers assigned user message symbols ( b = b ₁ , b ₂ , ..., b _k ) and zero values (0) for K users. Performs an inverse discrete Fourier transform (IDFT) on the first signal X ' = ( V ₁ , V ₂ , ..., V _N ) ^T combined with

) And the IDFT output (

) And M zeros (0)

By inserting the M zeros (0) at the end of), the OFDM symbol in the time domain that makes the power of the last part of the OFDM symbol copied from the time domain to the guard interval zero (0)

) And an OFDM symbol (P) that is a parallel signal of the synthesized time domain.

) Converts the serial signal into a sequential serial signal, and generates an OFDM transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic expansion and inserting the serial signal into a guard interval. The present invention provides a method for generating a transmission signal of an OFDM-FDMA wireless communication system, characterized in that to reduce the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal.

)(여기서 K는 사용자 수임)이 부반송파에 할당될 때 연접된 두 부반송파에 서로 다른 극성을 가지도록 리소스를 할당하는 단계와, 상기 부반송파로 매핑된 신호를 역이산 푸리에 변환(IDFT)하여 주파수 영역의 신호(

)를 시간 영역의 신호(

)로 변환하는 단계와, 상기 시간 영역신호로 변환된 병렬신호를 순차적인 시리얼 신호로 변환하는 단계와, 상기 시리얼 신호를 순환 확장부에 의해 시간 영역에서 직교 주파수 분할 다중(OFDM) 심볼의 마지막 부분을 복사하여 보호구간으로 삽입하여 전송신호를 생성하는 단계로 구성되며, 상기 두 부반송파에 서로 다른 극성을 가지는 복소 심볼값이 매핑되어 시간영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분의 평균 전력을 감소시키는 것에 의해 상기 OFDM 전송신호를 수신할 때 동일 채널 주파수 대역을 사용하는 주변 기지국으로부터 송신된 OFDM 간섭 신호의 영향을 감소시키는 것을 특징으로 하는 OFDM-FDMA 무선 통신 시스템의 전송신호 생성방법을 제공한다.According to another feature of the invention, the invention provides a message symbol (

) (Where K is the number of users), allocating resources to have two different polarities concatenated with different polarities, and performing an inverse discrete Fourier transform (IDFT) on the signals mapped to the subcarriers in the frequency domain. signal(

) Is a signal in the time domain

), Converting the parallel signal converted into the time domain signal into a sequential serial signal, and converting the serial signal into a final portion of an orthogonal frequency division multiplex (OFDM) symbol in the time domain by a cyclic extension unit. Copying and inserting into the guard interval to generate a transmission signal, and complex symbol values having different polarities are mapped to the two subcarriers, and the average power of the last part of the OFDM symbol copied to the guard interval in the time domain is mapped. A method of generating a transmission signal of an OFDM-FDMA wireless communication system characterized by reducing the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal. .

)(여기서 K는 사용자 수임)에 대하여 부반송파로서 왈시-하다마드(WH) 직교 코드(W₁,W₂,...,W_SF)(여기서 SF는 확산인자임)의 짝수번째 코드(

)를 먼저 할당하고 나머지 사용자의 메시지 심볼에 홀수번째 코드(

)를 할당하는 단계와, 상기 WH 직교 코드(W₁,W₂,...,W_SF)가 할당된 모든 사용자의 전송신호를 더하여 얻어진 순차적인 전송신호를 출력하는 단계와, 상기 순차적인 전송신호를 병렬 전송신호(

)로 변환하는 단계와, 상기 병렬 전송신호(

)를 역이 산 푸리에 변환(IDFT)하여 주파수 영역의 전송신호(

)를 시간영역의 전송신호(

)로 변환하는 단계와, 상기 시간영역의 병렬 전송신호(

)를 순차적인 시리얼 신호로 변환하는 단계와, 상기 시리얼 신호를 순환 확장에 의해 시간 영역에서 직교 주파수 분할 다중(OFDM) 심볼의 마지막 부분을 복사하여 보호구간으로 삽입하여 전송신호를 생성하는 단계로 구성되며, 상기 시간영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분의 전력을 감소시키는 것에 의해 상기 OFDM 전송신호를 수신할 때 동일 채널 주파수 대역을 사용하는 주변 기지국으로부터 송신된 OFDM 간섭 신호의 영향을 감소시키는 것을 특징으로 하는 OFDM-CDMA 무선 통신 시스템의 전송신호 생성방법을 제공한다.According to another aspect of the present invention, the present invention provides a method for generating a transmission signal of an OFDM-CDMA wireless communication system spreading using an orthogonal code in a frequency domain, wherein

) Is the even-numbered code of the Walsh-Hadamard (WH) orthogonal code (W ₁ , W ₂ , ..., W _SF ) (where SF is a spreading factor) as a subcarrier (where K is the number of users).

) And assign the odd-numbered code (

) And outputting a sequential transmission signal obtained by adding the transmission signals of all the users to which the WH orthogonal codes (W ₁ , W ₂ ,..., W _SF ) are allocated, and the sequential transmission. Signal to parallel transmission signal (

And the parallel transmission signal (

) Is the inverse Fourier transform (IDFT) of the transmission signal in the frequency domain

) Is the time-domain transmission signal (

And the parallel transmission signal in the time domain

) And converting the serial signal into a sequential serial signal, and generating a transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic expansion and inserting the serial signal into a guard interval. By reducing the power of the last part of the OFDM symbol copied to the guard interval in the time domain, the influence of the OFDM interference signal transmitted from the neighboring base station using the same channel frequency band when receiving the OFDM transmission signal is reduced. The present invention provides a method for generating a transmission signal in an OFDM-CDMA wireless communication system.

)(여기서 K는 사용자 수임)에 부반송파로서 푸리에 직교 코드(F₁~F_K)를 순차적으로 할당하는 단계와, 상기 푸리에 직교 코드(F₁ ~F_K)가 할당된 모든 사용자의 전송신호를 더하여 얻어진 순차적인 전송신호를 출력하는 단계와, 상기 순차적인 전송신호를 병렬 전송신호(

)로 변환하는 단계와, 상기 병렬 전송신호(

)를 역이산 푸리에 변환(IDFT)하여 주파수 영역의 전송신호(

)를 시간영역의 전송신호(

)로 변환하는 단계와, 상기 시간영역의 병렬 전송신호(

)를 순차적인 시리얼 신호로 변환하는 단계와, 상기 시리얼 신호를 순환 확장에 의해 시간 영역에서 직교 주파수 분할 다중(OFDM) 심볼의 마지막 부분을 복사하여 보호구간으 로 삽입하여 전송신호를 생성하는 단계로 구성되는 것을 특징으로 하는 OFDM-CDMA 무선 통신 시스템의 전송신호 생성방법을 제공한다.According to still another aspect of the present invention, in the method for generating a transmission signal of an OFDM-CDMA wireless communication system that spreads using an orthogonal code in a frequency domain, a message symbol of each user (

Sequentially assigning Fourier orthogonal codes (F ₁ to F _K ) as subcarriers to (where K is the number of users), and adding the transmission signals of all users to whom the Fourier orthogonal codes (F ₁ to F _K ) are assigned Outputting the obtained sequential transmission signal, and converting the sequential transmission signal into a parallel transmission signal (

And the parallel transmission signal (

Inverse Discrete Fourier Transform (IDFT)

) Is the time-domain transmission signal (

And the parallel transmission signal in the time domain

) And converting the serial signal into a sequential serial signal, and generating a transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic expansion and inserting the serial signal into a guard interval. The present invention provides a method for generating a transmission signal in an OFDM-CDMA wireless communication system.

(=N/SF)개 만큼의 메시지 심볼을 전송할 수 있고, k번째 사용자에게 할당되는 푸리에 코드는 F _k [p]=exp[-j2πk(p-1)/SF](여기서, p=1, ... , SF임)와 같이 길이 SF인 코드로 정의된다.If the number of subcarriers is N and the spreading factor is SF, up to SF users can be accommodated, and each user can receive one OFDM symbol.

As many as (= N / SF) message symbols can be sent, and the Fourier code assigned to the k th user is F _k [p] = exp [ -j 2π k ( p -1) / SF ] where p = 1, ..., SF).

The OFDM transmission signal, which is the digital signal generated as described above, is then converted into an analog transmission signal, and then converted / amplified into an RF transmission signal and transmitted to a user terminal in a wireless channel through an antenna.

As described above, in the present invention, the neighboring base station when receiving a transmission signal by intentionally reducing the power of the last part of the OFDM symbol copied to the guard interval inserted to prevent interference noise between subchannels during signal transmission in an OFDM system It is possible to reduce inter-cell interference noise for the same channel.

(Example)

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

1 is a timing diagram illustrating the interference signal of a neighboring base station and the DFT interval of a user terminal in order to explain interference noise between cells in a conventional orthogonal frequency division multiplexing (OFDM) wireless communication system. FIG. 3 is a schematic block diagram illustrating a transmitter of a multi-access OFDM wireless communication system to be applied. FIG. 3 is a timing diagram illustrating a comparison of power types of interference signals of adjacent base stations for a multi-access OFDM wireless communication system and various DFT intervals of a user terminal. It is also.

First, co-channel interference due to frequency reuse will be described with reference to FIG. 1.

In general, co-channel interference occurs due to frequency reuse in a wireless mobile communication system. When the OFDM system is operated in a wireless communication system, the co-channel interference noise received by the terminal regardless of the synchronization / asynchronousness between base stations causes the DFT timing to be offset so that the starting point of the DFT section 108 as shown in FIG. It may be out of range.

In this case, the interference signal 100 of the base station caused by another cell using the same frequency band as the base station of the cell to which the terminal belongs is the propagation delay of the channel in the case of synchronous, or the timing shift between base stations in the case of asynchronous. As a result, the signal is received out of alignment with the DFT timing of the terminal.

If the length of the OFDM symbol interval 104 is T and the length of the guard interval 102 is Tc, the DFT interval 108 of the terminal is the guard interval 102 of the OFDM interference signal 100 and the last portion 106 of the symbol. ) Are likely to be included at the same time.

Therefore, in the present invention, since the guard interval 102 and the last portion 106 inserted between the OFDM symbol interval 104 do not play an essential role in the transmission of the signal, the last of the OFDM symbol copied to the guard interval 102. By deliberately reducing the power of the part 106, a method of reducing interference noise by probabilistically reducing the power of the interference signal 100 of the adjacent base station in the time domain is proposed.

Meanwhile, the structure of the transmitter 200 of the multiple access OFDM system to which the present invention is applied will be briefly described with reference to FIG. 2.

Assuming the number of users is K, the symbol 202 of the total users, b = ( b ₁ , b ₂ , ..., b _k ) is passed to the resource mapper 208 and mapped to subcarriers in the frequency domain. If the signal 204 mapped to the subcarrier is X = ( X ₁ , X ₂ , ..., X _N ), the signal is inversely discrete Fourier transformed through the IDFT unit 210. Parallel-to-Serial (P / S) converter 212 after the signal is converted into a signal 206 in the time domain, that is, x = ( x ₁ , x ₂ , ..., x _N ) It is converted into a sequential serial signal via.

Subsequently, the serial signal is copied into the guard interval by copying the last part of the OFDM symbol in the time domain through the cyclic extension 214 to generate a transmission signal, and then a digital-to-analog (D / A) converter 216. Converts a digital transmission signal into an analog transmission signal, converts / amplifies the RF transmission signal into an RF transmission signal, and transmits the signal to a user terminal through a radio channel through an antenna 220.

The wireless mobile communication system may consider OFDM-FDMA and OFDM-CDMA according to a resource mapping scheme as a multiple access system. In the case of OFDM-FDMA, the symbols of users are allocated to different subcarriers, and in the case of OFDM-CDMA, the symbols of users are multiplied by different orthogonal spreading codes and mapped to all subcarriers.

The present invention proposes a resource mapping scheme that can reduce interference noise between cells according to each multiple access scheme.

3 is a timing diagram illustrating a comparison of power types of interference signals of adjacent base stations for a multiple access OFDM wireless communication system and various DTF intervals of a user terminal in order to explain a basic principle for reducing inter-cell interference noise according to the present invention. It is illustrated.

The power timing diagram of the interference signal of the neighboring base station for the same channel shown in FIG. 3 shows the interference of the neighboring base station in the time domain by intentionally reducing the power of the last portion 314 of the OFDM symbol copied into the guard interval 302. An example of implementing a method of reducing interference noise by probabilistically reducing the power of the signal 300.

As shown in FIG. 3, since the start point of the DFT timing of the interference signal 300 of the neighboring base station for the same channel due to the frequency reuse is an arbitrary point, the total power in the DFT period is changed according to the DFT timing. That is, in FIG. 3, the magnitude of the total power in the DFT period is determined by the first DFT section 306 having the DFT timing starting point of the terminal 0 to Tc and the second DFT having the DFT timing starting point of the terminal Tc ~ 2Tc according to the starting point of the DFT timing. The interval 308 may be divided into a third DFT interval 310 having a DFT timing starting point of the terminal 2Tc to T and a fourth DFT interval 312 having a DFT timing starting point of the terminal T˜T + Tc.

When the DFT timing start point is the first DFT period 306, the length of the sum of the guard period 302 included in the DFT period and the last portion 314 of the OFDM symbol becomes Tc, but the second DFT period 308 and In the fourth DFT section 312, it is Tc to 2Tc, and in the third DFT section 310, it is 2Tc.

Therefore, reducing the power of the last portion 314 of the OFDM symbol copied to the guard interval 302 can significantly reduce the power of the interference signal 300 of the adjacent base station in the time domain, and Parsval's theory ), The total power in the time domain is equal to the total power in the frequency domain, so the power of the interfering signals of neighboring base stations in the frequency domain is also stochastically reduced.

Meanwhile, the ratio of the length T of the OFDM symbol 304 to the length Tc of the guard period 302 is η (= T / Tc), and the average power of the guard period and the last part 314 of the OFDM symbol is P. _g , the average power of the signals excluding the guard interval 302 and the last part 314 of the OFDM symbol in the OFDM symbol is P _d , and the ratio of the two is β (= P _g / P _d ).

When the DFT interval of the user terminal is compared with the interference signal 300 of the neighboring base station, the probability that the first DFT interval 306 corresponds to 1 / ( η +1) becomes 1 / ( η +1), and the energy of the interference signal 300 is ( eta + β -1) P _d Tc . The probability that the DFT section of the terminal is the third DFT section 310 is ( η -2) / ( η +1), where the energy of the interference signal 300 is ( η +2 β -2) · P _d Tc . Similarly, the probability of the DFT section of the terminal one of claim 2 or claim 4 DFT section (308 312) is a 2 / (η +1), when the energy of the interference signal (η 2 +3 -3 β) · P _d · Tc Becomes / 2.

Therefore, the average energy P _a of the interference signal 300 according to the present invention is [ η ( η +2 β -1) / ( η +1)] · P _d Tc and the method according to the present invention is used. Since the average energy P _n of the interference signal is not ( η + β -1) · P _d · Tc , power gain occurs as shown in Equation 1 below.

4A and 4B illustrate an interference reduction method according to a first embodiment of the present invention through a signal design of a frequency domain in the OFDM-FDMA scheme based on the basic principle of the present invention shown in FIG. OFDM-FDMA symbol in the frequency domain, Figure 4b shows an OFDM-FDMA symbol in the time domain obtained by IDFT processing the OFDM-FDMA symbol in the frequency domain of Figure 4a.

FIG. 4A illustrates an OFDM symbol 400 in the frequency domain to produce an ideal frequency domain signal that zeros the power of the last portion 404 of the OFDM symbol 402 copied from the time domain to the guard interval as shown in FIG. 4B. ) Shows how to design.

Assume that the number of subcarriers is N, the length of the guard interval is M, and the number of users is K, as shown in FIG. 4B. Since the desired signal in the present invention is a signal in which the power of the last part of the OFDM signal copied to the guard interval in the time domain becomes zero, M points 404 of the last part of the OFDM signal in the time domain are determined to be zero. The remaining (NM) points are determined by K user message symbols 406 in the frequency domain, that is, b _k ( k = 1, 2, ..., K ) and (NMK) unused subcarriers 408. do.

A vector of (NM) / M points in sequence is determined as V _m ( m = 1, 2, ...., M), and M points of the last part determined in the time domain (404 ) And M points 412 in the frequency domain, determined by (NM) points determined in the frequency domain, u _i (i = 1, 2, ...., M), Let (NM) points 410 be a _j ( j = 1, 2, ...., NM).

Further, if signal 400 of one OFDM symbol interval in the frequency domain is X and signal 402 of one OFDM symbol interval in the time domain is x , then X = ( u ₁ , b ₁ , u ₂ , b ₂ ,. ..., u _M , b _M ) ^T , x = ( a ₁ , a ₂ , ..., a _NM , 0, 0, ...., 0,) can be represented by ^T and p rows q the value of the thermal element exp - If [j 2π (p -1) ( q -1) / N] is (N × M) called the DFT matrix d X can be expressed as equation (2).

X = Dx

If we divide D into N × (NM) matrices D ₁ and (N × M) matrices D ₂ , then D = ( D ₁ | D ₂ ) and x ₁ = ( a ₁ , a ₂ , ..., a _NM ) when X ^T d is expressed as equation (3).

X '= ( b ₁ , b ₂ , ..., b _M ) ^T , and in D ₁ 1, (N / M) +1, 2 (N / M) +1, ..., (M- 1) (N / M) +1 When the matrix from which the rows are removed is referred to as D ₁ ', X ' is expressed by Equation 4 below.

Therefore, when Equation 4 is summarized with respect to x ₁ , Equation 4 is obtained as in Equation 5 below.

라고 하면 x의 해

를 하기 수학식 6과 같이 구할 수 있고, 이는 시간 영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분(404)의 전력을 제로(0)로 만드는 시간 영역의 OFDM 심볼(402)을 의미한다. The solution of x ₁ to x ₁

The solution of x

Equation 6 can be obtained as shown in Equation 6 below, which means the OFDM symbol 402 of the time domain which makes the power of the last portion 404 of the OFDM symbol copied from the time domain to the guard interval zero.

In _{D 1 1, (N / M} ) +1, 2 (N / M) +1, ..., (M-1) (N / M) of M × (NM) matrix extracted the row D + 1 If u = ( u ₁ , u ₂ , ...., u _M ) ^T , u is summarized as in Equation 7 below.

를

라고 하면, X의 해

는 하기 수학식 8과 같이 구할 수 있고, 이는 시간 영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분(404)의 전력을 제로(0)로 만드는 주파수 영역의 OFDM 심볼(400)을 의미한다. U 's solution

To

The solution of X

Equation 8 can be obtained as shown in Equation 8, which means that the OFDM symbol 400 in the frequency domain makes the power of the last portion 404 of the OFDM symbol copied to the guard interval zero in the time domain.

FIG. 5 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a first embodiment of the present invention implemented according to the signal design of the frequency domain in the OFDM-FDMA shown in FIGS. 4A and 4B.

을 발생하기 위한 IDFT부(510)와, 상기 M개의 제로값(0)을 발생하기 위한 제2제로값 설정기(514)와, 상기 IDFT 출력(

)과 M개의 제로값(0)을 받아들여서 IDFT 출력(

)의 뒷부분에 M개의 제로값(0)을 집어넣어서 본 발명에서 원하는 신호인 상기 수학식 6의

를 합성함과 동시에, 합성된 병렬신호(

)를 순차적인 시리얼 신호로 변환하기 위한 P/S 변환부(512)를 포함한다.Referring to FIG. 5, a transmitter of a first embodiment of the present invention generates a user message symbol generator for generating K user messages, that is, b = ( b ₁ , b ₂ ,..., B _k ). 502 and a first zero value setter 514 for generating a zero value to assign zero values to both NMK unused subcarriers 408, and the user message symbol b = ( b ₁ , b ₂ , ..., b _k ) and a signal that is a combination of NMK unused subcarriers 408 assigned a zero value, i.e., X '= ( V ₁ , V ₂ , ... , V _N ) ^T 504 outputs the IDFT by performing an Inverse Discrete Fourier Transform (IDFT), i.e. ( D ₁ ') ^-1

An IDFT unit 510 for generating a second zero value, a second zero value setter 514 for generating the M zero values (0), and the IDFT output (

) And M zeros (0)

M zero values (0) are inserted at the back of the Equation 6, which is a desired signal in the present invention.

And synthesized parallel signals (

) Is converted into a sequential serial signal.

Hereinafter, a signal design operation in a frequency domain in OFDM-FDMA of the transmitter 500 of the multiple access OFDM wireless communication system according to the first embodiment of the present invention will be described.

First, all zero K user message symbols 502 from the user message symbol generator 502, b = ( b ₁ , b ₂ , ...., b _k ) and the first zero value setter 514 are assigned. When the NMK unused subcarriers 408 enter the IDFT unit 510, X '= ( V ₁ , V ₂ , ..., V _N ) ^T of Equation 4 is generated.

이 수행되면 IDFT 출력

이 발생된다. 상기 IDFT 출력(

)과 제2제로값 설정기(514)로부터의 M개의 제로값(0)은 P/S 변환부(512)에 인가되며, P/S 변환기(512)는 IDFT 출력(

)의 뒷부분에 M개의 제로값(0)을 집어넣어서 상기 수학식 6의

를 합성한 후 합성된 병렬신호(

)를 순차적인 시리얼 신호로 변환하여 출력한다. 그후 시리얼 신호는 도 2의 송신기와 같이 순환 확장부(214), D/A 변환부(216) 및 RF 송신회로(218)를 순차적으로 거친 후 안테나(220)를 통해 무선채널로 사용자 단말기에 전송된다. The inverse discrete Fourier transform (IDFT), i.e.

IDFT output when this is done

Is generated. The IDFT output (

) And the M zeros from the second zero value setter 514 are applied to the P / S converter 512, and the P / S converter 512 is connected to the IDFT output ().

M zero values (0) are inserted at the back of the

After synthesizing the synthesized parallel signal (

) Is converted into sequential serial signal and output. Thereafter, the serial signal is sequentially passed through the cyclic expansion unit 214, the D / A converter 216, and the RF transmission circuit 218 as shown in FIG. 2, and then transmitted to the user terminal through the antenna 220 in a wireless channel. do.

Therefore, the transmitter 500 of the multiple access OFDM wireless communication system according to the first embodiment serves to realize a method of statistically reducing the power of the last part of the OFDM symbol copied to the guard interval in the time domain.

6 is a resource mapping diagram illustrating a resource allocation method for canceling inter-cell interference in an OFDM-FDMA system according to a second embodiment of the present invention. FIG. 7 is a resource for implementing the resource allocation scheme of FIG. 6 in an OFDM-FDMA system. This is a mapping flowchart.

)이 부반송파에 할당될 때 연접된 두 부반송파에 서로 다른 극성을 가지도록 리소스를 할당하여 시간 영역에서 보호구간으로 복사되는 OFDM 심볼의 마지막 부분의 전력을 통계적으로 줄이는 방법이다.FIG. 6 is a second embodiment modified based on the basic principles of the present invention shown in FIG. 3 in the OFDM-FDMA scheme.

) Is a method of statistically reducing the power of the last part of the OFDM symbol copied into the guard interval in the time domain by allocating resources to have different polarities for the two concatenated subcarriers when the subcarrier is allocated to the subcarrier.

Hereinafter, a second embodiment will be described in detail with reference to the resource mapping flowchart of FIG. 7.

Referring to FIG. 7, first, the number of subcarriers is N, the number of users is K (S702), and assuming that each user symbol is allocated to one subcarrier, a conventional allocation scheme requires a total of K subcarriers.

,

)에 나누어서 전송하는데 각각 서로 다른 극성을 가지도록

와

의 심볼을 할당하고, 그 이후에는 사용자의 수가 N/2보가 큰 경우 즉, k = N/2+m 일 때는 사용자 심볼(

)을 기존에 할당되어 있던 부반송파(

)에 다시 할당하고

에 할당된 심볼값을

로 바꾸어 주는 방식으로 리소스를 할당하는 것이다.In the scheme proposed in the second embodiment of the present invention, each user symbol is concatenated with a subcarrier until the number of users reaches N / 2.

,

To transmit different polarities to each other.

Wow

Assigns a symbol of, and after that if the number of users is greater than N / 2, that is, k = N / 2 + m,

) Has been assigned to the subcarrier (

To reassign)

The symbol value assigned to

Allocate resources by changing

)을 도 6처럼 2개의 연접된 부반송파(

,

)에 나누어서 전송하는데 각각

와

의 심볼을 할당한다(S710). To this end, in the present invention, the user symbols are sequentially assigned to determine whether the kth user corresponds to k≤N / 2th (S704, S706).

) Into two concatenated subcarriers (

,

To send each)

Wow

To allocate a symbol (S710).

)을 기존에 할당되어 있던 부반송파(

)에 다시 할당하고 부반송파(

)에 할당된 심볼값을

로 바꾸어 준다(S712). After that, the symbol is continuously assigned while increasing the variable k by 1 (S714 and S716), and when k> N / 2th, that is, when k = N / 2 + m (S708), symbol(

) Has been assigned to the subcarrier (

And reassign subcarriers (

Symbol value assigned to

Change to (S712).

Using this resource allocation method, if K <N / 2, complex symbol values having different polarities are mapped to two concatenated subcarriers, thereby reducing the average power of the last portion of the OFDM symbol copied to the guard interval in the time domain. In addition, even in the case of K> N / 2, the symbols of two concatenated subcarriers have different polarities than those having the same polarity, thereby reducing the power of the last portion of the OFDM symbol.

8 is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a second embodiment for implementing a resource allocation scheme in OFDM-FDMA according to the methods of FIGS. 6 and 7.

), 즉 b₁ 내지 b_N/2, b_N/2+1 내지 b_N을 순차적으로 발생하기 위한 사용자 메시지 심볼발생기(802)와; 총 사용자의 수 K

N/2인 경우 두 개의 연접된 부반송파(

,

)에 나누어서 전송하도록 각 사용자의 메시지 심볼(

)에

를 곱하기 위한 (N/2)개의 제1승산기(803a)와, 두 개의 연접된 부반송파(

,

)에 나누어서 전송할 때 그 중에서 짝수 부반송파(

)에는 두 개의 연접된 부반송파(

,

)가 서로 다른 극성을 갖도록 -1을 곱하기 위한 N/2개의 제2승산기(803b)와, K>N/2인 경우 절환 작동으로 제2승산기(803b)의 출력 대신에 k=N/2+m사용자 메시지 심볼을 부반송파(

)에 할당하여 전송하기 위한 N/2개의 절환스위치(803c)를 각각의 사용자 심볼에 대하여 포함하는 리소스 매퍼(803)와; 리소스 매퍼(803)의 주파수 영역 출력신호(

)를 수신하여 역 이산 푸리에 변환(IDFT)을 수행하여 시간영역의 IDFT 출력(

)을 발생하기 위한 IDFT부(808)와; 상기 IDFT 출력(

)을 받아들여서 병렬신호(

)를 순차적인 시리얼 신호로 변환하기 위한 P/S 변환부(810)를 포함한다.Referring to FIG. 8, the transmitter 800 of the multiple access OFDM wireless communication system according to the second embodiment uses a user symbol (

A user message symbol generator 802 for sequentially generating b ₁ to b _{N / 2} , b _{N / 2 + 1} to b _N ; Total number of users K

For N / 2, two concatenated subcarriers (

,

Each user's message symbol (

)on

(N / 2) first multipliers 803a and two concatenated subcarriers (

,

When transmitting in even-numbered subcarriers (

) Has two concatenated subcarriers (

,

N / 2 second multipliers 803b for multiplying -1 so that) have different polarities, and k = N / 2 + instead of the output of the second multiplier 803b in a switching operation when K> N / 2 m User message symbol is sent to the subcarrier (

A resource mapper 803 including N / 2 changeover switches 803c for each user symbol to be allocated and transmitted to the &lt; RTI ID = 0.0 &gt; Frequency domain output signal of the resource mapper 803

) And perform an Inverse Discrete Fourier Transform (IDFT) to obtain the IDFT output (

An IDFT unit 808 for generating a); The IDFT output (

), The parallel signal (

) Is converted into a sequential serial signal.

Hereinafter, a frequency domain resource allocation scheme in OFDM-FDMA of a transmitter 800 of a multiple access OFDM wireless communication system according to a second embodiment of the present invention will be described.

N/2인 경우 제1승산기(803a)에서 각 사용자의 메시지 심볼(

)에

를 곱한다. 그후 제1승산기(803a) 출력은 두 개의 연접된 부반송파(

,

)에 나누어서 전송하기 위하여 짝수 부반송파(

)에는 제2승산기(803b)에서 -1을 곱하여 IDFT부(808)로 전송한다. When the user symbol symbol b of the total user comes from the user message symbol generator 802, the total number of users K is K.

In the case of N / 2, the message symbol of each user in the first multiplier 803a (

)on

Multiply by The first multiplier 803a outputs two concatenated subcarriers (

,

To transmit evenly by subdividing into

) Is multiplied by -1 in the second multiplier 803b and transmitted to the IDFT unit 808.

)을 부반송파(

)에 다시 할당하고, 부반송파(

)에 할당된 심볼값을

으로 바꾸어 준다. 이어서 IDFT부(808)는 리소스 매퍼(803)의 주파수 영역 출력신호(

)를 수신하여 역 이산 푸리에 변환(IDFT)을 수행하여 시간영역의 IDFT 출력(

)을 발생하며, 상기 IDFT 출력(

)은 P/S 변환부(810)에서 병렬신호(

)가 순차적인 시리얼 신호로 변환되어 도 2와 같은 과정으로 사용자 단말기로 전송된다.Then, when the number of users K is K> N / 2, that is, when k = N / 2 + m, the operation of the switch 803c causes k = N / 2 + m user message symbols (

) To the subcarrier (

) And subcarrier (

Symbol value assigned to

Replace with The IDFT unit 808 then outputs the frequency domain output signal of the resource mapper 803 (

) And perform an Inverse Discrete Fourier Transform (IDFT) to obtain the IDFT output (

) And the IDFT output (

) Is a parallel signal (P / S conversion unit 810)

) Is converted into a sequential serial signal and transmitted to the user terminal in the same process as shown in FIG. 2.

Therefore, the transmitter 800 of the multiple access OFDM wireless communication system according to the second embodiment serves to realize a method of reducing the average power of the last part of the OFDM symbol copied to the guard interval in the time domain.

FIG. 9 is a resource mapping diagram illustrating a WH orthogonal code assignment scheme in a frequency domain in an OFDM-CDMA system according to a third embodiment of the present invention. FIG. 10 is a diagram of a WH orthogonal code implementation of the WH orthogonal code assignment scheme of FIG. 11 is a schematic block diagram of a main part of a transmitter of a multiple access OFDM wireless communication system according to a third embodiment for implementing the WH orthogonal code allocation scheme in the frequency domain according to the methods of FIGS. 9 and 10. .

9 illustrates an example of applying the present invention to an OFDM-CDMA system that spreads using an orthogonal code in a frequency domain, and selectively assigns a Walsh-Hadamard (WH) orthogonal code allocated to each user from an even code. By reducing the power of the last part of the OFDM symbol is copied to the guard interval in the time domain.

)을 발생하기 위한 사용자 메시지 심볼발생기(1102)와, SF(확산인자)개의 승산기(1104a-1104SF)를 구비하고 사용자의 메시지 심볼(

)이 오면, 각 사용자의 메시지 심볼(

)에 짝수번째 WH직교 코드(W₂,W₄, ..., W_SF)부터 먼저 할당하고, 나머지 사용자의 메시지 심볼에 홀수번째 WH직교 코드(W₁,W₃,...,W_SF-1)를 할당하기 위한 리소스 매퍼(1104)와, WH직교 코드(W₁,W₂,...,W_SF)가 할당된 모든 사용자의 신호를 더하기 위한 합산기(SUM)(1108)와, 상기 합산기의 순차적인 신호를 병렬 신호(

)로 변환하기 위한 S/P(Serial-to-Parallel) 변환부(1110)와, 상기 S/P 변환부(1110)의 병렬 신호(

)를 IDFT 처리하여 주파수 영역의 신호(

)를 시간영역의 신호(

)로 변환하기 위한 IDFT부(1112)와, 상기 IDFT부(1112)의 IDFT 출력(

)을 받아들여서 병렬 신호(

)를 순차적인 시리얼 신호로 변환하기 위한 P/S 변환부(1114)를 포함한다.First, referring to FIG. 11, the transmitter 1100 of the multiple access OFDM wireless communication system according to the third embodiment uses message symbols of each user.

And a user message symbol generator 1102 and SF (spreading factor) multipliers 1104a-1104SF for generating a user's message symbol (

), Each user's message symbol (

) Is assigned to even-numbered WH orthogonal codes (W ₂ , W ₄ , ..., W _SF ) first, and the remaining user's message symbols are odd-numbered WH orthogonal codes (W ₁ , W ₃ , ..., W _SF). and a resource mapper (1104) for assigning a _-1), WH orthogonal code _{(W 1, W 2, ...} , W SF) is a summer (sUM) (1108) for plus signals of all users assigned with The parallel signal of the sequential signal of the summer (

S-P (Serial-to-Parallel) converter 1110 and the parallel signal (S / P converter 1110)

) Is processed by the IDFT signal in the frequency domain (

) Is the time domain signal (

) And an IDFT output of the IDFT unit 1112.

) Accepts a parallel signal (

) Is converted into a sequential serial signal.

9 to 11, the operation of the third embodiment of the present invention will be described.

In the third embodiment of the present invention, a resource is allocated by selectively allocating a Walsh-Hadamard (WH) orthogonal code assigned to each user from an even code.

WH orthogonal codes have SF code sets {W ₁ , W ₂ , ...., W _SF } (S1002), and if the spreading factor is SF, it can accommodate up to SF users. As many as N / SF message symbols may be transmitted in one OFDM symbol.

)이 오면, k번째 사용자가 k≤SF/2번째에 해당되는 지를 판단하여(S1004,S1006), 판단결과 k≤SF/2인 경우에는 도 9와 같이 각 사용자의 메시지 심볼(

)에 짝수번째 WH직교 코드(

)부터 먼저 할당하는 방식으로 순차적으로 사용자 심볼을 할당한다(S1010). The resource mapper 1104 receives the user's message symbol (from the user message symbol generator 1102 to the multipliers 1104a-1104SF).

), It is determined whether the k-th user corresponds to k≤SF / 2th (S1004, S1006), and when the determination result k≤SF / 2, as shown in FIG.

) Even-numbered WH orthogonal code (

The user symbols are sequentially assigned in a manner of first assigning (S1010).

)을 할당하여(S1014,S1016), k>SF/2번째에 해당되는 경우, 즉 K=SF/2+m인 경우는(S1008), 나머지 사용자의 메시지 심볼에 홀수번째 WH직교 코드(

)를 할당한다(S1012).After that, the variable (k) is incremented by 1 and the even-numbered WH orthogonal code (

) Is assigned (S1014, S1016), where k> SF / 2th, that is, when K = SF / 2 + m (S1008), the odd WH orthogonal code (

) Is allocated (S1012).

)로 변환한 후 IDFT부(1112)로 보내면 IDFT부(1112)에서는 병렬 전송신호(

)를 IDFT 처리하여 주파수 영역의 전송신호(

)를 시간영역의 전송신호(

)로 변환하여 출력하며, 이 시간영역의 전송신호는 P/S 변환부(1114)를 거치면서 병렬 전송신호(

)가 다시 순차적인 시리얼 신호로 변환되어 도 2와 같은 나머지 과정을 거쳐 무선채널로 전송된다.The S / P converter 1110 then adds the transmission signals of all the users assigned the WH orthogonal codes W ₁ , W ₂ ,..., And _{SF to the} SUM 1108. Will output In the S / P converter 1110, the sequential transmission signals are converted into parallel transmission signals (

), And then to the IDFT unit 1112, the IDFT unit 1112 transmits the parallel transmission signal (

) Is processed by the IDFT to transmit the signal in the frequency domain (

) Is the time-domain transmission signal (

) Is converted into the output signal, and the transmission signal of this time domain passes through the P / S conversion unit 1114 and the parallel transmission signal (

) Is converted into a sequential serial signal and transmitted to the wireless channel through the remaining process as shown in FIG.

As described above, according to the third embodiment, in the case of K≤SF / 2, even if complex values having different polarities are mapped to symbol values of two contiguous carriers and K> SF / 2, these characteristics are statistically maintained. Since the power of the last portion of the OFDM symbol is small because of the high probability, the interference noise between cells can be reduced.

That is, in the case of OFDM-CDMA, the symbols of each user are first spread with different orthogonal codes and then combined and transmitted. In the case of using the WH code as the orthogonal code, if the even code is assigned first, the polarities of the concatenated subcarriers are different from each other, thereby reducing the power of the last part of the ODFM symbol. do.

However, if an odd number of codes is assigned, the power of the last part of the OFDM symbol is increased.

However, if k> SF / 2, then the even numbered WH code is assigned first, and then only the odd numbered WH codes are assigned, so even numbered WH codes are assigned more than odd numbered WH codes. Therefore, the desired effect can be obtained in the present invention. That is, the WH orthogonal code allocation scheme according to the third embodiment has a high probability of having such a property statistically.

12 is a resource mapping diagram showing a Fourier code allocation scheme in a frequency domain according to the present invention in an OFDM-CDMA system according to a fourth embodiment of the present invention. FIG. 13 is a frequency domain of an OFDM-CDMA system according to the method of FIG. Is a schematic block diagram of an essential part of a transmitter of a multiple access OFDM wireless communication system according to a fourth embodiment for implementing a Fourier code allocation scheme.

(=N/SF)개 만큼의 메시지 심볼을 전송할 수 있다. FIG. 12 shows another embodiment in which the present invention is applied to an OFDM-CDMA system that spreads using an orthogonal code in a frequency domain, and uses a Fourier code as an orthogonal code assigned to each user. If the number of subcarriers is N and the spreading factor is SF, up to SF users can be accommodated, and each user can receive one OFDM symbol.

As many as (= N / SF) message symbols can be transmitted.

코드는 시간 영역에서

번째 샘플을 중심으로 임펄스에 가까운 신호가 형성되므로, 이러한 방법으로 리소스를 할당하면 시간 영역에서 OFDM 심볼의 앞 부분부터

(=N/SF) 간격을 두고 K개의 임펄스 신호가 나타나게 된다. 그러므로 보호구간으로 복사되는 OFDM 심볼의 마지막 부분의 전력을 줄일 수가 있고, 그 결과 셀간의 간섭잡음을 줄일 수 있게 된다. The Fourier code assigned to the k th user according to the fourth embodiment is equal to F _k [ p ] = exp [− j 2π k ( p −1) / SF ], where p = 1, ..., SF. Likewise, it is defined as a code of length SF.

Code in the time domain

Since a signal close to an impulse is formed around the first sample, the resource allocation in this way allows the first part of the OFDM symbol in the time domain.

K impulse signals appear at intervals of (= N / SF). Therefore, the power of the last part of the OFDM symbol copied into the guard interval can be reduced, and as a result, the interference noise between cells can be reduced.

)에 푸리에 직교 코드(F₁~F_K)를 순차적으로 할당하기 위한 다수의 승산기(1304_a~1304_SF)를 구비하고 있다.The transmitter 1300 of the multiple access OFDM wireless communication system according to the fourth embodiment shown in FIG. 13 is an apparatus that implements the resource allocation method illustrated in FIG. 12. The user message symbol generator 1302 is a resource mapper 1304. When a user's message symbol is received from each user's message symbol (

) Are provided with a plurality of multipliers 1304 _a to 1304 _SF for sequentially assigning Fourier orthogonal codes F ₁ to F _K.

)에 푸리에 직교 코드(F₁~F_K)를 순차적으로 할당한 후 합산기(SUM)(1108)에서 푸리에 직교 코드(F₁~F_K)가 할당된 모든 사용자의 전송신호를 더하여 얻어진 순차적인 전송신호를 S/P 변환기(1110)로 출력한다. Therefore, when the transmitter 1300 of the fourth embodiment receives the user's message symbol from the user message symbol generator 1302 in the resource mapper 1304, the message symbols of each user in the multipliers 1304 _a to 1304 _SF are applied.

Sequential assignment of the Fourier orthogonal codes (F ₁ to F _K ) to the sequential order, and then adds the transmission signals of all users assigned the Fourier orthogonal codes (F ₁ to F _K ) in the summer (SUM) 1108 The transmission signal is output to the S / P converter 1110.

)로 변환한 후 IDFT부(1112)로 보내면 IDFT부(1112)에서는 병렬 전송신호(

)를 IDFT 처리하여 주파수 영역의 전송신호(

)를 시간영역의 전송신호(

)로 변환하여 출력하며, 이 시간영역의 전송신호는 P/S 변환부(1114)를 거치면서 병렬 전송신호(

)가 다시 순차적인 시리얼 신호로 변환되어 도 2와 같은 나머지 과정을 거쳐 무선채널로 전송된다.Thereafter, as in the third embodiment, the S / P converter 1110 converts the sequential transmission signals into parallel transmission signals (

), And then to the IDFT unit 1112, the IDFT unit 1112 transmits the parallel transmission signal (

) Is processed by the IDFT to transmit the signal in the frequency domain (

) Is the time-domain transmission signal (

) Is converted into the output signal, and the transmission signal of this time domain passes through the P / S conversion unit 1114 and the parallel transmission signal (

) Is converted into a sequential serial signal and transmitted to the wireless channel through the remaining process as shown in FIG.

As described above, in the present invention, when a multiple access OFDM system is operated in a mobile cellular environment, the power of the last part of an OFDM symbol copied to a guard interval inserted to prevent interference noise between subchannels during signal transmission is intentionally reduced. This makes it possible to reduce interference noise between cells on the same channel of adjacent base stations when receiving a transmission signal.

As described above, the reduction of intercell interference noise in a cellular environment immediately means an increase in system capacity. In addition, the present invention makes it possible to efficiently determine the OFDM system specifications and parameters by allowing the guard interval, which has been recognized to reduce the efficiency of signal transmission, to be effectively used to reduce intercell interference noise.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (15)

In the resource allocation method of the OFDM wireless communication system for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion, inserting into the guard interval, When the user message symbol is mapped to the subcarrier in the frequency domain, the resource allocation method of the OFDM wireless communication system characterized by intentionally reducing the power of the last part of the OFDM symbol copied to the guard interval in the time domain. . In the resource allocation method of an OFDM-FDMA wireless communication system for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion, inserting into the guard interval, In turn, each user's message symbol (

), Where K is the number of users, so that each user's message symbol (

) Into two concatenated subcarriers (

,

Divided by)

Wow

Assigning a symbol of, If the user is k = N / 2 + mth, the user symbol (

) Has been assigned to the subcarrier (

And reassign subcarriers (

Symbol value assigned to

Resource allocation method for an OFDM-FDMA wireless communication system, characterized in that it comprises a step of switching to: In the resource allocation method of an OFDM-CDMA wireless communication system for generating an OFDM transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in the time domain by cyclic expansion, inserting it into a guard interval, Each user's message symbol (

) Is the even-numbered code of the Walsh-Hadamard (WH) orthogonal code (W ₁ , W ₂ , ..., W _SF ) (where SF is a spreading factor) as a subcarrier (where K is the number of users).

) First, Odd-numbered code in the remaining user's message symbols (

Allocating a resource allocation method for an OFDM-CDMA wireless communication system, characterized in that the step of assigning (). In the resource allocation method of an OFDM-CDMA wireless communication system for generating an OFDM transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in the time domain by cyclic expansion, inserting it into a guard interval, Each user's message symbol (

(Where K is the number of users), the method of allocating Fourier orthogonal codes F ₁ to F _K as subcarriers sequentially. Mapping user symbols to subcarriers in the frequency domain; Converting a signal in the frequency domain into a signal in the time domain by inverse discrete Fourier transform (IDFT) on the signal mapped to the subcarrier; Converting the parallel signal converted into the time domain signal into a sequential serial signal; Copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by a cyclic extension unit and inserting the serial signal into a guard interval to generate an OFDM transmission signal. From a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal by intentionally reducing the power of the last part of the OFDM symbol copied into the guard interval when mapping the user symbol to the subcarrier in the frequency domain A method of generating a transmission signal in an OFDM wireless communication system, characterized in that the influence of the transmitted OFDM interference signal is reduced. A first signal ( X '= () which combines user message symbols ( b = b ₁ , b ₂ , ..., b _k ) for K users and NMK unused subcarriers assigned a zero value (0). Perform an inverse discrete Fourier transform (IDFT) on V ₁ , V ₂ , ...., V _N ) ^T )

), The IDFT output (

) And M zeros (0)

By inserting the M zeros (0) at the end of), the OFDM symbol in the time domain that makes the power of the last part of the OFDM symbol copied from the time domain to the guard interval zero (0)

), OFDM symbol which is a parallel signal of the synthesized time domain

) Into a sequential serial signal, Copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic expansion and inserting the serial signal into a guard interval to generate an OFDM transmission signal, And a method of generating a transmission signal of an OFDM-FDMA wireless communication system, wherein the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal is reduced. Each user's message symbol (

Assigning resources to have different polarities for the two concatenated subcarriers when) (where K is the number of users) is assigned to the subcarriers, Inverse Discrete Fourier Transform (IDFT) on the signal mapped to the subcarrier,

) Is a signal in the time domain

), Converting the parallel signal converted into the time domain signal into a sequential serial signal; Generating a transmission signal by copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by inserting the serial signal into a guard interval by a cyclic extension; The same channel frequency band is used when receiving the OFDM transmission signal by reducing the average power of the last portion of the OFDM symbol copied to the guard interval in the time domain by mapping complex symbol values having different polarities to the two subcarriers. A method of generating a transmission signal in an OFDM-FDMA wireless communication system, characterized by reducing the influence of an OFDM interference signal transmitted from a neighboring base station. 8. The message symbol of claim 7, wherein each user's message symbol (

When () is assigned to a subcarrier, the step of allocating resources to have different polarities for two concatenated subcarriers Each user's message symbols are assigned in sequence, until each user's symbol (

) Into two concatenated subcarriers (

,

Divided by)

Wow

Assigning a symbol of, If the user is k = N / 2 + mth, the user symbol (

) Has been assigned to the subcarrier (

And reassign subcarriers (

Symbol value assigned to

Transmitting signal generation method of an OFDM-FDMA wireless communication system, characterized in that for converting to. A transmission signal generation method of an OFDM-CDMA wireless communication system spreading using an orthogonal code in a frequency domain, Each user's message symbol (

) Is the even-numbered code of the Walsh-Hadamard (WH) orthogonal code (W ₁ , W ₂ , ..., W _SF ) (where SF is a spreading factor) as a subcarrier (where K is the number of users).

) And assign the odd-numbered code (

), Outputting a sequential transmission signal obtained by adding transmission signals of all users to which the WH orthogonal codes (W ₁ , W ₂ ,..., W _SF ) are allocated; Parallel transmission signal (sequential transmission signal)

), The parallel transmission signal (

Inverse Discrete Fourier Transform (IDFT)

) Is the time-domain transmission signal (

), Parallel transmission signal in the time domain

) Into a sequential serial signal, Copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic expansion and inserting the serial signal into a guard interval to generate a transmission signal, Reducing the impact of OFDM interference signals transmitted from neighboring base stations using the same channel frequency band when receiving the OFDM transmission signal by reducing the power of the last portion of the OFDM symbol copied into the guard interval in the time domain. A method of generating a transmission signal in an OFDM-CDMA wireless communication system characterized by the above-mentioned. A transmission signal generation method of an OFDM-CDMA wireless communication system spreading using an orthogonal code in a frequency domain, Each user's message symbol (

Sequentially assigning Fourier orthogonal codes (F ₁ to F _K ) as subcarriers to (where K is the number of users), Outputting a sequential transmission signal obtained by adding the transmission signals of all users to which the Fourier orthogonal codes F ₁ to F _K are assigned; Parallel transmission signal (sequential transmission signal)

), The parallel transmission signal (

Inverse Discrete Fourier Transform (IDFT)

) Is the time-domain transmission signal (

), Parallel transmission signal in the time domain

) Into a sequential serial signal, Copying the last part of an orthogonal frequency division multiplex (OFDM) symbol in a time domain by cyclic extension and inserting the serial signal into a guard interval to generate a transmission signal. Transmission signal generation method. 12. The method of claim 10, wherein if the number of subcarriers is N and a spreading factor is SF, up to SF users can be accommodated, and each user can receive one OFDM symbol.

As many as (= N / SF) message symbols can be sent, and the Fourier code assigned to the k-th user is: F _k [ p ] = exp [ -j 2π k ( p -1) / SF ] where p = 1, ..., SF), the transmission signal generation method of the OFDM-CDMA wireless communication system characterized in that it is defined by a code having a length SF. A transmitter for an OFDM-FDMA wireless communication system, A user message symbol generator for generating user message symbols b = ( b ₁ , b ₂ , ..., b _k ) for _K users, A first zero value setter for generating a zero value so as to assign zero values to all N-M-K unused subcarriers, A first signal X '= ( V ₁ , V ) in which the user message symbols b = ( b ₁ , b ₂ ,..., B _k ) and NMK unused subcarriers allocated with a zero value (0) are combined. IDFT output by performing an inverse discrete Fourier transform (IDFT) on ₂ , ..., V _N ) ^T

IDFT unit for generating a; A second zero value setter for generating the M zero values; The IDFT output (

) And M zeros (0)

Insert the M zeros (0) at the end of the symbol to zero the power of the last part of the OFDM symbol copied from the time domain to the guard interval.

) And simultaneously synthesized parallel signal (

Parallel / serial (P / S) converter for converting It consists of a cyclic expansion unit for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion and inserting the serial signal into a guard interval, And reducing the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal. A transmitter for an OFDM-FDMA wireless communication system, Each user's message symbol (

A user message symbol generator for sequentially generating Each user's message symbol (

Resource mapper for allocating resources to have different polarities for two concatenated subcarriers when (), where K is the number of users), Frequency domain output signal of the resource mapper (

) And perform inverse discrete Fourier transform (IDFT) to obtain the IDFT output signal (

IDFT unit for generating The IDFT output signal (

) And the IDFT output signal (

Parallel / serial (P / S) converter for converting It consists of a cyclic expansion unit for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion and inserting the serial signal into a guard interval, And reducing the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal. A transmitter for an OFDM-CDMA wireless communication system, Each user's message symbol (

A user message symbol generator for generating SF (spreading factor) multipliers and the user's message symbol (

), Each user's message symbol (

) Even-numbered sub-carriers as the Walsh-Hadamard (WH) orthogonal code _{(W 2, W 4, ...} , W SF) from the first allocation, the second odd-numbered symbols to the other user messages WH orthogonal code (W _1, W Resource mapper for allocating ₃ , ..., W _SF-1 ), A summer (SUM) for adding the signals of all users assigned the WH orthogonal codes (W ₁ , W ₂ , ..., W _SF ), Parallel signals (sequential signals of the summer)

Serial / parallel (S / P) converter to convert Parallel signal of the S / P conversion unit (

) Is processed by the IDFT signal in the frequency domain (

) Is the time domain signal (

IDFT unit for converting IDFT output of the IDFT unit (

) Accepts a parallel signal (

Parallel / serial (P / S) converter for converting It consists of a cyclic expansion unit for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion and inserting the serial signal into a guard interval, And reducing the influence of an OFDM interference signal transmitted from a neighboring base station using the same channel frequency band when receiving the OFDM transmission signal. A transmitter for an OFDM-CDMA wireless communication system, Each user's message symbol (

A user message symbol generator for generating When the user's message symbol is received from the user message symbol generator, the message symbol of each user (

A resource mapper having a plurality of multipliers for sequentially assigning Fourier orthogonal codes F ₁ to F _K as subcarriers, A summer (SUM) for adding the transmission signals of all users to which the Fourier orthogonal codes F ₁ to F _K are allocated; Parallel signals (sequential signals of the summer)

Serial / parallel (S / P) converter to convert Parallel signal of the S / P conversion unit (

) Is processed by the IDFT signal in the frequency domain (

) Is the time domain signal (

IDFT unit for converting IDFT output of the IDFT unit (

) Accepts a parallel signal (

Parallel / serial (P / S) converter for converting It consists of a cyclic expansion unit for generating an OFDM transmission signal by copying the last portion of the orthogonal frequency division multiplex (OFDM) symbols in the time domain by cyclic expansion and inserting the serial signal into a guard interval, Reducing the impact of OFDM interference signals transmitted from neighboring base stations using the same channel frequency band when receiving the OFDM transmission signal by reducing the power of the last portion of the OFDM symbol copied into the guard interval in the time domain. A transmitter for an OFDM-CDMA wireless communication system.

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