KR101460107B1

KR101460107B1 - Method and System for changing cyclic prefix length in wireless communication system

Info

Publication number: KR101460107B1
Application number: KR1020080105458A
Authority: KR
Inventors: 곽현선
Original assignee: 삼성전자주식회사
Priority date: 2008-10-27
Filing date: 2008-10-27
Publication date: 2014-11-12
Also published as: WO2010050731A2; KR20100046565A; WO2010050731A3

Abstract

The present invention relates to a method for changing a cyclic prefix length in a base station in a wireless communication system, the method comprising: determining a cyclic prefix length by determining a channel status during data transmission; And generating a cyclic transposition length change information by comparing the length of the cyclic prefix length change information and transmitting the downlink reference signal with the cyclic prefix length change information to the terminal. The cyclic transposition length change information is added to an initial value (C _int ) of a pseudo-random sequence used in generating the downlink reference signal.

According to the method for changing the cyclic prefix length of the base station of the present invention, the length of the cyclic prefix is flexibly changed according to the channel state, thereby efficiently coping with the channel change and maintaining stable connection, and the base station informs the terminal of the length of the cyclic prefix Symbol synchronization can be efficiently obtained.

Guard interval, cyclic prefix, cyclic prefix

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for changing a cyclic prefix length in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for changing a cyclic transposition length of a base station in a communication system, and more particularly to a method for changing a cyclic transposition length of a base station in a communication system capable of transmitting data by changing the length of cyclic prefix .

The Universal Mobile Telecommunication Service (UMTS) system is based on Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), which are European mobile communication systems, and includes a Wideband Code Division Multiple Access WCDMA) is used as the third-generation asynchronous mobile communication system.

In the 3rd Generation Partnership Project (3GPP), which is in charge of standardization of UMTS, a discussion on LTE (Long Term Evolution) is underway as a next generation mobile communication system of UMTS system. LTE is a technology that implements high-speed packet-based communication with transmission speeds of up to 300 Mbps and aims to commercialize it in about 2010. Various schemes are being discussed for this purpose. For example, there are discussions to reduce the number of nodes located on the communication path by simplifying the structure of the network, and to approach the wireless protocols as much as possible to the wireless channel.

In particular, in order to reduce the influence of multipath (ghost), LTE (Long Term Evolution) inserts a guard interval into which a cyclic prefix Send and receive. That is, by increasing the symbol period of the transmitted signal and transmitting the data by inserting the guard interval into which the CP is input, it is possible to reduce the intersymbol interference that may be caused due to the delay of the received symbols passing through the multipath, So that inter-channel interference can be reduced. Also, the UE can acquire the time synchronization of the symbol period using the CP input in the guard interval.

On the other hand, there is a problem that the length of the current CP is fixed when the connection between the subscriber station and the base station is established, and the length of the current CP is not changed even if the channel status is changed or the current CP length is determined not to be suitable for the current channel status . In other words, there is a problem that the length of the CP can not be changed flexibly according to the change of the channel environment.

The present invention proposes a method and an apparatus for a base station to change the length of a CP according to a channel state when a communication system forms a channel with the terminal and is transmitting data.

According to another aspect of the present invention, there is provided a method for changing a cyclic prefix length in a base station in a wireless communication system, the method comprising: determining a channel state during data transmission to determine a cyclic prefix length; And generating a cyclic prefix length change information by comparing the current cyclic prefix length with a current cyclic prefix length, and transmitting the downlink reference signal with the cyclic prefix length change information to the terminal. The cyclic transposition length change information is added to an initial value (C _int ) of a pseudo-random sequence used in generating the downlink reference signal.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components are denoted by the same reference numerals as possible in the accompanying drawings. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

Also, the terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor is not limited to the concept of terms in order to describe his invention in the best way. It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be properly defined.

In the present invention, a guard interval refers to a signal interval longer than a maximum delay spread of a channel inserted between consecutive symbols to prevent OFDM (Orthogonal Frequency Division Multiplexing) intersymbol interference. In the guard interval, The signal of the last section is copied and inserted, and this is referred to as a cyclic prefix (CP).

Also, in the present invention, the OFDM symbol period refers to the sum of the effective symbol period and the cyclic transposition length at which the actual data is transmitted.

In the present invention, a downlink reference signal is a pilot signal for coherent demodulation of a downlink channel, and refers to a cell specific reference signal shared by all terminals in a cell and a terminal specific reference signal used only by a specific terminal . The downlink reference signal is generated using a pseudo-random sequence.

In the present invention, the uplink reference signal refers to a demodulation reference signal (DMRS) for coherent demodulation of an uplink channel and a sounding reference signal (SRS) for frequency domain scheduling of a data channel do.

It is also assumed that the terminology of the embodiment of the present invention conforms to the 3GPP LTE system standard.

1 is a diagram illustrating a schematic structure of a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 1, in a wireless communication system according to an embodiment of the present invention, an Evolved Radio Access Network (E-RAN) 110 and 112 includes an evolved Node B (ENB) 120 , 122, 124, 126, and 128, and an EPC (Evolved Packet Core) 130 and 132.

The UE (User Equipment) 101 connects to the IP (Internet Protocol) network 114 by the E-RANs 110 and 112. The ENBs 120, 122, 124, 126, and 128 are connected to the user terminal 101 via a radio channel as nodes corresponding to the existing Node Bs. In order to realize a transmission rate of up to 300 Mbps, the wireless communication system uses Orthogonal Frequency Division Multiplexing (OFDM) as a radio access technology in a 20 MHz bandwidth. In particular, here, wireless channel 1 represents an ideal channel in which no unintended interference or delay occurs between the ENB and the UE, and wireless channel 2 represents a non-ideal channel in which unintended interference or delay occurs by a fixed object , And wireless channel 3 shows a non-ideal channel by a moving object. The guard interval into which the CP is input can be inserted between effective symbols to prevent distortion or delay that may occur in such a non-ideal channel, thereby suppressing inter-channel interference and inter-symbol interference.

However, since the fixed CP length can not effectively cope with the dynamically changing channel environment, the ENB periodically detects the channel environment even in the data communication with the UE to determine whether it is necessary to change the CP length. If it is determined that the length of the CP needs to be changed, the ENB may add information indicating that the CP length is changed to the downlink reference signal and transmit it to the UE. Also, the UE may receive the above-described CP length change information, and then modify the CP length of the received data to the changed information to obtain symbol synchronization. Also, if the UE periodically checks the channel status and determines that it is necessary to change the length of the CP, it may transmit the request for changing the CP length to the ENB by including it in the UL control signal. Such a CP length change request can be used as a criterion for the ENB to determine the channel state.

Hereinafter, the E-RAN 110 and 112 including the ENBs 120, 122, 124, 126 and 128 and the UEs 130 and 132 are referred to as the base station 200, ).

Next, a hierarchical structure of a wireless protocol of a wireless communication system according to an embodiment of the present invention will be described. 2 is a diagram illustrating a hierarchical structure of a wireless protocol of a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 2, a wireless protocol according to an embodiment of the present invention includes Packet Data Convergence Protocol (PDCP) Protocol 205, Radio Link Control (RLC) 210 and 235, Access Control 215, 230) layer, and further includes a physical layer (PHY Layer) 220, 225.

The Packet Data Convergence Protocol (PDCP) layers 205 and 240 are responsible for operations such as IP header compression / decompression. The RLC layers 210 and 235 reconstruct a PDCP PDU (packet data unit, hereinafter referred to as a PDU of the protocol) to an appropriate size to perform an ARQ (Automatic Repeat Request) operation.

The MACs 215 and 230 are connected to a plurality of RLC layer devices configured in one terminal. The MACs 215 and 230 multiplex various RLC PDUs output from the RLC layer devices with MAC PDUs and demultiplex the RLC PDUs from the MAC PDUs.

The physical layers 220 and 225 perform channel coding and modulation of the upper layer data and transmit the OFDM symbols on a wireless channel or demodulate OFDM symbols received on a wireless channel, channel decoding, and transmit the OFDM symbols to an upper layer. The physical downlink channel includes a Physical Broadcast Channel (PBCH), a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a Physical Hybrid ARQ Indicator Channel (PHICH), a Physical Downlink Shared Channel (PDSCH) A physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a physical random access channel (PRACH), a sounding reference signal channel (PMCH), a reference signal SRS).

Meanwhile, the uplink demodulation reference signal (DMRS) is transmitted together with the PUCCH and the PUSCH, and the DMRS or the sounding reference signal includes the CP length change request. Also, the base station transmits the downlink reference signal to the terminal through the RS, and the downlink reference signal includes the CP length change information.

3 is a diagram showing the structure and the type of the CP disclosed in the LTE specification of the present invention.

Referring to FIG. 3, an extended CP is generated and inserted into a length of 512 T _S, which is three times longer than a normal CP, and is suitable for a multipath channel environment in which channel interference or delay is likely to occur. On the contrary, Normal CP is suitable for a case where a symbol number (l) is 160 T _S and a symbol number is 1 ~ 6 days 144 T _S and a high data transmission amount is required in a stable radio channel.

According to an embodiment of the present invention, a base station determines a length of one of a normal CP and an extended CP according to a channel environment through a downlink reference signal, and transmits the determined length to a terminal. That is, the base station grasps the delay time and the degree of distortion of the signal transmitted from the terminal, and transmits information indicating that the length of the CP is changed to the terminal. When the terminal receives the above information, the terminal decodes data received from the next symbol period on the basis of the changed CP length. The terminal also checks the delay and distortion of the signal received by the base station to determine the channel state and transmits a signal requesting the change of the guard interval length to the base station. The change of the guard interval length can be transmitted by including it in the uplink reference signal. That is, if the BS and the UE form a channel and are transmitting / receiving data, if the channel state has a high probability of inter-channel interference or intersymbol interference, the BS changes information from Normal CP to Extended CP to transmit data And the UE can change the normal CP to the extended CP as a base station and transmit the request information to transmit the data.

Hereinafter, a method of including the information that the base station changes the length of the CP into the downlink reference signal will be described. The base station sets the length of the CP considering channel conditions. At this time, the base station sets the initial value (C _int ) of the pseudo-random sequence at the time of generating the reference signal as shown in Equation (1) below.

[Formula 1]

C _init = 2 ¹⁰ (7 (n _s +1) + l + 1) + 2 N _ID ^cell + N _CP

N _CP = 1 for normal CP

N _CP = 0 for extended CP

As shown in Equation (1), the initial CP length is set to N _CP and transmitted to the UE. The UE decodes the received signal based on one of the normal CP and the extended CP according to the value of N _CP . The base station transmits a downlink reference signal to the mobile station every predetermined period even if data is being transmitted through a wireless channel formed between the mobile station and the base station. At this time, the initial value (C _int ) of the pseudo-random sequence is set as shown in Equation 2 below when generating the downlink reference signal.

[Formula 2]

C _init = 2 ¹⁰ (7 (n _s +1) + l + 1) + 2 N _ID ^cell + N _CP

N _CP = 1 if the CP length should be changed in the next period

N _CP = 0 if the CP length should be the same in the next period

In other words, when the value of N _CP is 1, the data transmitted from the base station from the next cycle is the current The length of the CP is changed from the length of the CP to the length of another CP. If N _CP is 0, The length of the CP is maintained. Therefore, if the base station desires to change the length of the _CP , it can acquire the symbol synchronization of the data transmitted from the next symbol period by toggling N _CP , and can change the length of the CP by coping with the channel condition efficiently.

Next, a description will be given of a method in which the UE includes the CP length change request information in the uplink reference signal to the base station. When a wireless channel is established between a terminal and a base station and data is being transmitted, the terminal transmits an uplink reference signal to the base station. The uplink reference signal is divided into a demodulation reference signal (DMRS) and a sounding reference signal (SRS), and a sequence shift pattern of a base sequence group is used in signal generation. According to the LTE specification, the sequence shift pattern is determined by Equation 3 below.

[Formula 3]

f _SS ^PUCCH = N _ID ^cell MOD 30 (PUCCH DMRS or SRS)

f _SS ^PUSCH = (f _SS ^PUCCH + ?? _SS ) MOD 30 (PUSCH DMRS)

According to the embodiment of the present invention, when the UE transmits the protection interval length change request information to the base station, it generates information on the CP length in the sequence shift pattern as shown in Equation 4 below.

[Formula 4]

f _SS ^PUCCH = (N _ID ^cell +2 ⁹ ?? N _CP ) MOD 30 (PUCCH DMRS or SRS)

N _CP = 1 if the CP length should be changed in the next period

N _CP = 0 if the CP length should be the same in the next period

f _SS ^PUSCH = (f _SS ^PUCCH + ?? _SS +2 ⁶ ?? N _CP ) MOD 30 (PUSCH DMRS)

N _CP = 1 if the CP length should be changed in the next period

N _CP = 0 if the CP length should be the same in the next period

If it is determined that the CP length needs to be changed, the UE toggles N _CP and transmits the uplink reference signal including the CP length change request information to the base station to use as a criterion for determining the channel state of the base station have.

4 is a flowchart illustrating a process of generating a downlink reference signal including a CP length change information by a base station according to an embodiment of the present invention.

Referring to FIG. 4, in step 400, a base station periodically detects a channel state while transmitting / receiving data by forming a wireless channel with a terminal. That is, the base station determines whether there is intersymbol interference (ISI) or inter-channel interference (ICI) in the current wireless channel. The base station may determine whether or not the CP length change request information is received from the terminal, and may include it in the channel state information. The process of the base station receiving and processing the CP length change request information from the terminal is shown in FIG. 6 and will be described in detail later.

In step 405, the base station determines whether it is necessary to change the currently set CP length based on the detected channel state. For example, if the metric of inter-symbol interference (ISI) or inter-channel interference (ICI) is numerically expressed, change the CP length to Extended CP (if the current CP is Normal CP) or maintain Extended CP And the currently set CP is the Extended CP). Similarly, if the CP is less than the reference value, it is determined that the CP length is changed to the normal CP (when the currently set CP is an Extended CP) or that the Normal CP is maintained (when the currently set CP is a Normal CP).

If it is determined in step 405 that the current CP length is to be changed, the base station sets the CP length change information (N _CP ) to 1 in step 410. If it is determined in step 405 that the current CP length is maintained, the base station sets the CP length change information (N _CP ) to 0 in step 415.

Subsequently, in step 420, the BS determines whether the CP length change information (N _CP ) Generates a pseudo-random sequence using an initial value (C _int ), and generates a downlink reference signal using the generated pseudo-random sequence. In other words, the downlink reference signal including the CP length change information is generated.

Subsequently, in step 425, the base station transmits the downlink reference signal including the CP length change information, so that the terminal sets up symbol synchronization based on the changed CP length from the next cycle after receiving the downlink reference signal.

5 is a flowchart illustrating a process of generating an uplink reference signal including a request for changing a CP length according to an embodiment of the present invention.

Referring to FIG. 5, in step 500, a mobile station periodically detects a channel state while transmitting / receiving data by forming a radio channel with a base station. That is, the UE determines whether inter-symbol interference (ISI) or inter-channel interference (ICI) exists in the wireless channel connected to the current BS. In step 505, the UE determines whether it is necessary to change the currently set CP length based on the detected channel state.

If it is determined in step 505 that it is necessary to change the current CP length, the UE sets the CP length change information request (N _CP ) to 1 in step 510. If it is determined in step 505 that there is no need to change the current CP length, the terminal sets the CP length change information request ( _NCP ) to 0 in step 515. [

Subsequently, in step 520, the base station determines whether the CP length change information request is reflected Generates a sequence-shift pattern, and generates an uplink reference signal using the generated sequence-shift pattern. In other words, the uplink reference signal including the CP length change request is generated.

Subsequently, in step 525, the UE transmits the uplink reference signal including the CP length change request to the base station, thereby inducing the base station to change the CP length.

6 is a flowchart illustrating a process in which a base station receives an uplink reference signal from a UE and detects and recognizes CP length change request information according to an embodiment of the present invention.

Referring to FIG. 6, in step 600, the BS receives an uplink reference signal from a UE. Herein, the uplink reference signal refers to one of PUCCH DMRS, PUSCH DMRS, or SRS. In step 605, the base station detects a sequence shift pattern of the received DMRS and SRS. Subsequently, in step 610, the base station checks the detected sequence shift pattern to see if there is a CP change request.

Subsequently, the base station determines in step 615 whether there is a CP change request from the terminal. If it is determined in step 615 that there is a CP change request from the terminal, the base station recognizes the CP length change request of the terminal in step 620 and determines the channel state.

7 is a diagram illustrating a signal flow between a Node B and UEs in a mobile communication system in which a CP length is changed according to a channel environment according to an embodiment of the present invention.

Referring to FIG. 7, in step 700, the base station transmits and receives data by forming a wireless channel based on the terminal and the normal CP length. In other words, the base station assumes that the terminal is communicating with the normal CP by initial setting. In step 705 and step 710, if the UE detects a channel state and determines that data transmission / reception is not smooth due to inter-symbol interference and inter-channel interference, a demodulation reference signal (DMRS) ) Or SRS (Sounding Reference Signal).

The base station determines whether to change the CP length. If the CP is changed, the base station sets the initial value of the pseudo random number sequence to an N _CP value of 1 to generate a downlink reference signal. In other words, in this embodiment, the base station transmits information including information indicating that data is changed by changing the normal CP to the extended CP starting from the next cycle in steps 715 and 720, and transmits the information including the extended CP in step 725 and step 730 The data is modulated and transmitted.

In step 735, the UE determines that high-efficiency data transmission is required by changing the channel state, and transmits a demodulation reference signal (DMRS) or a SRS (Sounding Reference Signal) including the CP length change request information to the base station do. The base station determines whether the CP length is changed. In step 640, the base station sets the initial value of the pseudo random number sequence with the N _CP value of 1 to generate and transmit the downlink reference signal. Therefore, in the present embodiment, the base station changes from an Extended CP to a Normal CP starting from the next cycle, and transmits information including information indicating that data is transmitted, in the DL reference signal. Subsequently, in step 745, the base station modulates data based on the normal CP length to the terminal and transmits the modulated data.

8 is a block diagram of a transmitter and a receiver of a downlink reference signal channel in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 8, the downlink reference signal transmitter includes a channel state determination unit 801, a CP length determination unit 802, and a reference signal generation unit 803. The receiver of the downlink reference signal includes a CP length change information detection unit 804 and a CP length determination unit 805.

First, regarding the transmitter, the channel state determination unit 801 periodically detects a channel state during data transmission and reception to determine whether there is an inter symbol interference (ISI) or an inter channel interference (ICI) in a wireless channel.

In addition, the CP length determining unit 802 determines whether it is necessary to change the currently set CP length based on the channel state detected by the channel state determining unit 801. [ For example, if the metric of inter-symbol interference (ISI) or inter-channel interference (ICI) is numerically expressed, change the CP length to Extended CP (if the current CP is Normal CP) or maintain Extended CP And the currently set CP is the Extended CP).

The CP length determination unit 802 outputs the CP length change information to the reference signal generation unit 803. [ The reference signal generation unit 803 generates the reference signal with the CP length change information (N _CP ) Generates a pseudo-random sequence using an initial value (C _int ), and generates a downlink reference signal using the generated pseudo-random sequence. In other words, the downlink reference signal including the CP length change information is generated. The generated downlink reference signal is transmitted to the terminal through the downlink reference signal channel (RS channel).

Next, we will look at the receiver. The CP length change information detection unit 804 detects CP length change information in the downlink reference signal received via the downlink reference signal channel (RS channel). The CP length determination unit 805 determines the length of the CP inserted in the data to be transmitted by the base station in the next period using the CP length and the CP length change information that have already been set.

9 is a block diagram of a transmitter and a receiver of a downlink data channel in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 9, a transmitter 900 will be described. The transmitter 900 includes a modulator 901, a serial / parallel converter 902, an IFFT processor 903 having N sizes, a P / S converter 904, a CP inserter 905, a D / And a conversion unit 906.

The data to be transmitted (Data Source) is input to the modulator 901 of the transmitter 910. The data input to the modulator 901 is modulated according to the modulation scheme used in each system and input to the S / P converter 902. Accordingly, the modulated serial data is converted into N parallel data in the serial / parallel converter 902 and input to the IFFT processor 903. Accordingly, the IFFT processor 903 converts the N parallel data into an inverse Fourier transform and inputs the inverse parallel data to the P / S converter 904. The P / S converter 904 converts the inverse Fourier transformed data into serial data and outputs the serial data. The data output from the P / S converter 904 is input to the CP inserter 905, CP is added to the data, and the data is converted into an OFDM symbol and output.

In detail, the CP inserting unit 905 generates a CP having a length set in the Extended CP or the Normal CP based on the data output from the P / S converter 904, and adds the generated CP to the input data do. In other words, if the transmitter transmits information indicating that the CP length is changed from the next period when transmitting the downlink reference signal to the receiver, the transmitter adds the CP of the changed length to generate an OFDM symbol. The output OFDM symbol is converted into an analog signal through the D / A converter 906 and transmitted through a predetermined radio channel.

Next, the receiver 950 will be described. The receiver 950 includes an A / D converter 951, a CP demultiplexer 952, a S / P converter 953, an N-sized FFT transformer 954, an equalizer 955 A synchronization and channel estimation unit 956, a parallel / serial conversion unit 957, and a demodulation unit 958. The received analog signal is input to the A / D converter 951, converted into a digital signal, and output to the CP remover 952. The CP removing unit 952 removes the CP inserted at the time of transmission from the input signal and outputs a signal. That is, the signal from which the CP is removed in the CP removing unit 952 is a signal composed of only valid OFDM data. The signal from which the CP is removed is input to the serial / parallel converter 953, processed in parallel, and output to the FFT processor 954. The FFT processing unit 954 performs FFT transform processing with a size of N and outputs FFT-transformed parallel data to an equalizer 955. The signal input to the equalizer 955 is output as a channel equalized signal. Also, the signal output from the equalizer 955 is input to the P / S converter 957, converted into serial signals, and then output. The serial-converted signal is input to the demodulator 958 and demodulated to extract the complete data. The synchronization and channel estimation unit 956 performs symbol synchronization acquisition and performs channel estimation for the equalizer 955 tap setting. Meanwhile, the length of the CP to be removed is set by detecting the CP length change information transmitted through the downlink reference signal at the transmitter.

As another embodiment of the present invention, the base station may transmit CP length change information to be changed by including it in a radio resource control (RRC) message instead of a physical layer signal. In other words, the CP length information of each of the downlink and uplink to be used in the next cycle can be transmitted to the UE by including it in the SIB2 message.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative examples of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic structure of a mobile communication system according to an embodiment of the present invention; FIG.

2 is a diagram illustrating a hierarchical structure of a wireless protocol of a wireless communication system according to an embodiment of the present invention;

3 is a diagram showing the structure and type of a CP disclosed in the LTE specification of the present invention.

4 is a flowchart illustrating a process in which a base station generates a downlink reference signal including CP length change information according to an embodiment of the present invention.

7 is a diagram illustrating a signal flow between a Node B and UEs in a mobile communication system in which a CP length is changed according to a channel environment according to an embodiment of the present invention;

Claims

A method for changing a cyclic prefix length in a base station,

Determining a cyclic transposition length by determining a channel state during data transmission,

Generating cyclic transposition length change information by comparing the determined cyclic transposition length with a current cyclic transposition length;

And transmitting a downlink reference signal to which the cyclic prefix length change information is added to the UE.

The method according to claim 1,

Inserting the cyclic prefix of the determined length into the transmission data, and transmitting the cyclic prefix to the terminal.

The method of claim 1, wherein the cyclic transposition length change information

And adding an initial value (C _int ) of a pseudo-random sequence used for generating the downlink reference signal to the initial value (C _int ) of the pseudo-random sequence.

The method of claim 1, wherein the determining comprises:

Further comprising the step of receiving an uplink reference signal including a cyclic prefix length change request from the terminal.

5. The method of claim 4, wherein the cyclic transposition length change request

And generating a sequence shift pattern used for generating the uplink reference signal by changing the sequence shift pattern.

Determining a length of a cyclic prefix according to a channel state during data transmission;

Generating a cyclic prefix length change request by comparing the determined cyclic prefix length with a current cyclic prefix length;

And transmitting the uplink reference signal including the cyclic prefix length change request to the base station by the terminal.

The method according to claim 6,

Detecting a cyclic prefix length change request included in the received uplink reference signal and determining a cyclic prefix length of a next cycle;

Transmitting, by the base station, a downlink reference signal including cyclic transposition length change information to the terminal;

Further comprising the step of the base station inserting the determined cyclic prefix into the transmission data and transmitting the inserted cyclic prefix to the terminal.

7. The method of claim 6, wherein the cyclic transposition length change request

A cyclic prefix length determination unit for detecting a channel state to determine a cyclic prefix length, a cyclic prefix length change information generation unit for generating cyclic prefix length change information by comparing the determined cyclic prefix length with a current cyclic prefix length, A downlink reference signal generator for generating a downlink reference signal to which the cyclic transposition length change information is added, and a modulator for modulating data by inserting a cyclic prefix of the determined length into the transmission data during data transmission; and

And a demodulator for demodulating the data by removing the cyclic prefix of the determined length.

The apparatus of claim 9, wherein the downlink reference signal generator

And adds the cyclic transposition length change information to an initial value (C _int ) of a pseudo-random sequence used in generating the downlink reference signal.

10. The method of claim 9,

A cyclic prefix length determination unit for detecting a channel state and determining a length of the cyclic prefix,

A cyclic prefix length change request generator for generating a cyclic prefix length change request by comparing the determined cyclic prefix length with a current cyclic prefix length,

Further comprising an uplink reference signal generator for generating an uplink reference signal to which the cyclic transposition length change request is added.

12. The apparatus of claim 11, wherein the uplink reference signal generator

And adds the cyclic transposition length change request to a sequence-shift pattern used when generating the uplink reference signal.

The method of claim 9, wherein the downlink reference signal is

And transmitted to the terminal through the downlink reference signal channel.

14. The method of claim 13, wherein the modulated data comprises

And transmitted to the terminal through the downlink data channel.