KR20100046565A

KR20100046565A - Method and system for changing cyclic prefix length in wireless communication system

Info

Publication number: KR20100046565A
Application number: KR1020080105458A
Authority: KR
Inventors: 곽현선
Original assignee: 삼성전자주식회사
Priority date: 2008-10-27
Filing date: 2008-10-27
Publication date: 2010-05-07
Also published as: WO2010050731A3; KR101460107B1; WO2010050731A2

Abstract

The present invention relates to a method of 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 state during data transmission, and determining the cyclic prefix length and the current cyclic prefix length. And comparing the lengths to generate cyclic prefix length change information, and transmitting a downlink reference signal to which the cyclic prefix length change information is added to the terminal. The cyclic prefix length change information may be added to an initial value C _int of a pseudo-random sequence used when generating the downlink reference signal.

According to the method of changing the cyclic prefix length of the base station of the present invention, by changing the length of the cyclic prefix in accordance with the channel state, it is possible to efficiently cope with the channel change and maintain a stable connection, and the base station notifies the terminal of the cyclic prefix length in advance. Symbol synchronization can be obtained efficiently.

Description

Method and system for changing cyclic prefix length in wireless communication system

The present invention relates to a method of changing a cyclic prefix length of a base station in a communication system, and more particularly, to a method of changing a cyclic prefix length of a base station in a communication system capable of transmitting data by changing the length of the cyclic prefix according to a change in channel state during data transmission. It is about.

UMTS (Universal Mobile Telecommunication Service) system is based on the European mobile communication system Global System for Mobile Communications (GSM) and General Packet Radio Services (GPRS), and Wideband Code Division Multiple Access, Third generation asynchronous mobile communication system using WCDMA).

The 3rd Generation Partnership Project (3GPP), which is in charge of UMTS standardization, is discussing Long Term Evolution (LTE) as the next generation mobile communication system of the UMTS system. LTE is a technology that implements high-speed packet-based communication with a transmission speed of up to 300 Mbps, and aims to commercialize it in 2010. To this end, various schemes are discussed. For example, a scheme of reducing the number of nodes located on a communication path by simplifying a network structure, or approaching wireless protocols as close as possible to a wireless channel are under discussion.

In particular, LTE (Long Term Evolution) is a method for reducing the influence of multi-path (ghost) to insert a guard interval (cyclic prefix) (CP) is input to the transmission signal in the symbol unit to insert the data Send and receive That is, by increasing the symbol period of the transmitted signal, by inserting the guard interval inputted by the CP to transmit data, it is possible to reduce the inter-symbol interference that may be caused by the delay of the received symbols through the multi-path, and the orthogonality of the subcarriers It can be maintained to reduce the interference between channels. In addition, the UE can obtain the time synchronization of the symbol period using the CP input to the protection period.

On the other hand, the length of the current CP is fixed when the connection between the terminal and the base station is set, there is a problem that the length of the current CP does not change even if it is determined that the channel state is changed or the length of the current CP is not suitable for the current channel state. . In other words, there is a problem in that the length of the CP cannot be changed flexibly according to the change of the channel environment.

The present invention is to propose a method and apparatus for changing the length of the CP according to the channel state when the base station is transmitting data by forming a channel with the terminal.

In the wireless communication system of the present invention for solving the above object, a cyclic prefix length change method in a base station includes determining a cyclic prefix length by determining a channel state during data transmission, and the determined cyclic prefix length. And comparing the current cyclic prefix length with each other to generate cyclic prefix length change information, and transmitting a downlink reference signal including the cyclic prefix length change information to the terminal. The cyclic prefix length change information may be added to an initial value C _int of a pseudo-random sequence used when generating the downlink reference signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present invention will be omitted.

Also, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should use the concept of terms to explain their own invention in the best way. It should be interpreted as meanings and concepts corresponding to 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 the maximum delay spread of a channel inserted between consecutive symbols to prevent interference between orthogonal frequency division multiplexing (OFDM) symbols, and a guard interval is a valid symbol in the guard interval. The signal of the last section is copied and inserted in the section, and this is called a cyclic prefix (CP).

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

In addition, in the present invention, the 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 using only 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 the uplink channel and a sounding reference signal (SRS) for frequency domain scheduling of the data channel. do.

In addition, the terms of the embodiment of the present invention will be in accordance with 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 exemplary embodiment of the present invention, an Evolved Radio Access Network (E-RAN) 110 and 112 may be an Evolved Node B (ENB) 120. , 122, 124, 126, and 128 and an Evolved Packet Core (EPC) 130, 132.

The UE (User Equipment) 101 connects to the Internet Protocol (IP) network 114 by the E-RANs 110 and 112. The ENBs 120, 122, 124, 126, and 128 are nodes corresponding to the existing Node Bs and are connected to the user terminal 101 through a wireless channel. In order to realize a transmission rate of up to 300 Mbps, a wireless communication system uses Orthogonal Frequency Division Multiplexing (OFDM) as a wireless access technology in a 20 MHz bandwidth. In particular, here, radio channel 1 represents an ideal channel in which unintended interference or delay does not occur between the ENB and the UE, and radio channel 2 represents a non-ideal channel in which unintended interference or delay caused by a fixed object occurs. , Radio channel 3 shows a non-ideal channel by a moving object. The guard interval, into which the CP is input, is inserted between effective symbols to prevent distortion or delay that may occur in such an ideal channel, thereby suppressing inter-channel interference and inter-symbol interference.

However, since the fixed CP length cannot effectively cope with the dynamically changing channel environment, the ENB periodically detects the channel environment and determines whether it is necessary to change the length of the CP even during data communication with the UE. If it is determined that the length of the CP needs to be changed, the ENB may add information indicating that the length of the CP is changed to the downlink reference signal and transmit the information to the UE. In addition, the UE may receive the above-described change information of the CP length, and may later obtain symbol synchronization by modifying the CP length of the received data to the changed information. In addition, when the UE also periodically checks the channel state and determines that the length of the CP needs to be changed, the UE may transmit a request for changing the length of the CP to the ENB in the uplink control signal. The request for changing the CP length may be used as a reference for the ENB to determine the channel state.

Hereinafter, the E-RAN 110, 112 including the ENBs 120, 122, 124, 126, 128, and ?? 130, 132 is connected to the base station 200, and the UE 101 is connected to the mobile terminal 100. It will be called).

Next, a hierarchical structure of a radio protocol of a radio 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 exemplary embodiment of the present invention.

2, a wireless protocol according to an embodiment of the present invention is PDCP (Packet Data Convergence Protocol 205, 240), Radio Link Control (hereinafter referred to as RLC) (210, 235), and MAC (Medium) Access control 215, 230, including the layer, and further comprises a physical layer (PHY Layer, PhysicalLayer) (220, 225).

The Packet Data Convergence Protocol (PDCP) layers 205 and 240 are responsible for operations such as IP header compression / restore. 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 Automatic Repeat Request (ARQ) operation.

The MACs 215 and 230 are connected to several RLC layer devices configured in one terminal. The MACs 215 and 230 multiplex multiple RLC PDUs output from the RLC layer devices into MAC PDUs and demultiplex the RLC PDUs from the MAC PDUs.

The physical layers 220 and 225 channel-code and modulate upper layer data, make an OFDM symbol, and transmit it to a wireless channel, or demodulate, channel decode, and transmit an OFDM symbol received through a wireless channel to a higher layer. Physical downlink channels include Physical Broadcast Channel (PBCH), Physical Control Format Indicator Channel (PCFICH), Physical Downlink Control Channel (PDCCH), Physical Hybrid ARQ Indicator Channel (PHICH), Physical Downlink Shared Channel (PDSCH), Physical Multicast Channel ( PMCH), Reference signal (RS) and Sync channel, and the physical uplink channel includes a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), a physical random access channel (PRACH), a sounding reference signal channel ( SRS) and the like.

Meanwhile, the uplink demodulation reference signal (DMRS) may be transmitted together with the PUCCH and the PUSCH. The DMRS or the sounding reference signal may include a CP length change request. In addition, the base station transmits the downlink reference signal to the terminal through the RS, the downlink reference signal is transmitted with the CP length change information.

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

Referring to FIG. 3, an extended CP is 512 T _S in length and is inserted and inserted three times longer than a normal CP, and is suitable for a multipath channel environment having a high probability of channel interference or delay. On the contrary, Normal CP is 160 T _S when the symbol number l is 0 and 144 T _S when the symbol number is 1 to 6, and is suitable when high data transmission amount is required in a stable wireless channel.

According to an embodiment of the present invention, the base station determines a length of one of the protection intervals of the normal CP or the extended CP according to the channel environment through the downlink reference signal and transmits it to the terminal. That is, the base station grasps the delay time and the distortion degree of the signal transmitted from the terminal, and transmits information to change the length of the CP to the terminal. In addition, when the terminal receives the above information, data received from the next symbol period is decoded based on the changed length of the CP. 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 for requesting the change of the guard interval length to the base station. The request for changing the guard interval length may be included in the uplink reference signal and transmitted. In other words, even when the base station and the terminal form a channel and are transmitting and receiving data, if the channel state has a high probability of occurrence of channel-to-channel or symbol-to-symbol interference, the base station transmits data to the terminal from the normal CP to the extended CP to transmit data. The terminal may transmit the request information to transmit data by changing from the normal CP to the extended CP to the base station.

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

[Equation 1]

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

N _CP = 1 for normal CP

N _CP = 0 for extended CP

As disclosed in Equation 1, the initial CP length is set to N _CP and transmitted to the UE, and the UE decodes the received signal based on one of the normal CP or the extended CP according to the value of N _CP . Even when a wireless channel is formed between the terminal and the base station, the base station transmits a downlink reference signal to the terminal at regular intervals. At this time, when generating the downlink reference signal, an initial value (C _int ) of a pseudo-random sequence is set as shown in Equation 2 below and transmitted.

[Equation 2]

C _init = 2 ¹⁰ (7 (n _s +1) + l + 1) + 2N _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 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 period is It means that information is changed from the length of CP to the length of another CP. If the value of N _CP is 0, the current It means that the length of the CP is maintained. Accordingly, when the base station wants to change the length of the CP, the base station can acquire the symbol synchronization of data transmitted from the next symbol period by toggling the N _CP and transmitting the CP.

Next, a method of including a CP length change request information to the base station in an uplink reference signal will be described. When a radio channel is formed between the terminal and the 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 both of them use a sequence-shift pattern of a base sequence group when generating a signal. In addition, according to the LTE specification, the sequence shift pattern is determined by the following Equation 3.

[Equation 3]

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

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

When the terminal transmits the guard interval length change request information to the base station according to an embodiment of the present invention, as shown in Equation 4 below, the terminal includes information about the CP length in the sequence shift pattern.

[Equation 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 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 same in the next period

If it is determined that the CP length needs to be changed by determining the channel state, the UE may toggle the N _CP to transmit an 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 CP length change information by a base station according to an embodiment of the present invention.

Referring to FIG. 4, in step 400, the base station periodically detects a channel state while establishing a wireless channel with a terminal to transmit and receive data. That is, the base station determines whether there is inter-symbol interference (ISI) or inter-channel interference (ICI) in the current radio channel. In addition, the base station may determine whether to receive the CP length change request information from the terminal, it may include in the channel state information. The process of receiving and processing the CP length change request information from the terminal is described with reference to FIG. 6 and will be described in detail later.

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

Subsequently, if it is determined in step 405 that the current CP length is changed, the base station sets 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 CP length change information N _CP to 0 in step 415.

Subsequently, in step 420, the base station reflects the set CP length change information N _CP . A pseudo-random sequence is generated using an initial value C _int , and a downlink reference signal is generated using the pseudo-random sequence. In other words, a downlink reference signal including CP length change information is generated.

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

5 is a flowchart illustrating a process of generating, by the terminal, an uplink reference signal including a CP length change request according to an embodiment of the present invention.

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

Subsequently, if it is determined in step 505 that the current CP length needs to be changed, the UE sets the CP length change information request (N _CP ) to 1 in step 510. In addition, if it is determined in step 505 that it is not necessary to change the current CP length, the terminal sets the CP length change information request (N _CP ) to 0 in step 515.

In step 520, the base station reflects the set CP length change information request. A sequence-shift pattern is generated and an uplink reference signal is generated using the sequence shift pattern. In other words, an uplink reference signal including a CP length change request is generated.

Subsequently, in step 525, the terminal transmits an uplink reference signal including a 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 terminal to detect and recognize CP length change request information according to an embodiment of the present invention.

Referring to FIG. 6, the base station receives an uplink reference signal from the terminal in step 600. Here, the uplink reference signal refers to one of PUCCH DMRS, PUSCH DMRS, or SRS. In addition, in step 605, the base station detects the sequence shift pattern of the received DMRS and SRS. In step 610, the base station determines whether there is a CP change request based on the detected sequence shift pattern.

Subsequently, the base station determines whether there is a CP change request from the terminal in step 615. In addition, when 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 a channel state.

FIG. 7 is a diagram illustrating a signal flow between a base station and terminals 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 establishes a wireless channel based on a normal CP length with a terminal to transmit and receive data. In other words, it is assumed that the base station is in communication with the terminal by initially setting the system to the Normal CP. In step 705 and step 710, if the terminal detects the channel state and the inter-symbol interference and the inter-channel interference is present to determine that the data transmission and reception is not smooth, demodulation reference signal including the CP length change request information to the base station (Demodulation Reference Signal, DMRS Or SRS (Sounding Reference Signal).

The base station receives this, generates a downlink reference signal by setting the initial value of the pseudo random number sequence to a N _CP value is 1, if you want to determine whether changes to the CP length, and change. In other words, in the present embodiment, the base station transmits the information indicating that the base station transmits data by changing from the normal CP to the extended CP from the next period in steps 715 and 720, and transmits the extended CP in steps 725 and 730. The data is modulated and transmitted as a reference.

In step 735, the UE determines that the channel state is changed to require high-efficiency data transmission, and transmits a demodulation reference signal (DMRS) or sounding reference signal (SRS) including CP length change request information to the base station. do. Upon receiving this, the base station determines whether the CP length is changed. In step 640, the base station sets an initial value of a pseudo random number sequence with an N _CP value of 1 to generate and transmit a downlink reference signal. Therefore, in the present embodiment, the base station transmits the downlink reference signal with information indicating that data is transmitted from the extended CP to the normal CP from the next period. Subsequently, in step 745, the base station modulates and transmits data based on the normal CP length to the terminal.

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 transmitter of the downlink reference signal includes a channel state determiner 801, a CP length determiner 802, and a reference signal generator 803. In addition, the receiver of the downlink reference signal includes a CP length change information detector 804 and a CP length determiner 805.

First, referring to the transmitter, the channel state determination unit 801 periodically detects a channel state while transmitting and receiving data to determine whether inter-symbol interference (ISI) or inter-channel interference (ICI) exists in a wireless channel.

In addition, the CP length determiner 802 determines whether a change in the currently set CP length is necessary based on the channel state detected by the channel state determiner 801. For example, if the measure of inter-symbol interference (ISI) or inter-channel interference (ICI) is numerically exceeded, change the CP length to Extended CP (if the currently set CP is Normal CP), or maintain the Extended CP ( If the current CP is an extended CP).

In addition, the CP length determiner 802 outputs CP length change information to the reference signal generator 803. The reference signal generator 803 reflects CP length change information N _CP . A pseudo-random sequence is generated using an initial value C _int , and a downlink reference signal is generated using the pseudo-random sequence. In other words, a downlink reference signal including CP length change information is generated. The generated downlink reference signal is transmitted to the terminal through a downlink reference signal channel (RS channel).

Next, the receiver will be described. The CP length change information detector 804 detects CP length change information from a downlink reference signal received through a downlink reference signal channel (RS channel). In addition, the CP length determining unit 805 determines the length of the CP inserted in the data to be transmitted by the base station in the next period by using the CP length and the CP length change information that are already 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, the 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 parallel / serial converter 904, a CP inserter 905, and a D / A. The conversion unit 906 is configured.

Data to be transmitted is input to the modulator 901 of the transmitter 910. Data input to the modulator 901 is modulated according to a modulation scheme used in each system and input to the serial / parallel converter 902. Accordingly, the modulated serial data is converted into N parallel data by the serial / parallel converter 902 and input to the IFFT processor 903. Accordingly, the IFFT processor 903 inverse Fourier transforms the N parallel data and inputs it to the parallel / serial converter 904. The parallel / serial converter 904 converts the inverse Fourier transformed data into serial data and outputs the serial data. In addition, the data output from the parallel / serial converter 904 is input to the CP inserter 905, adds a CP to the data, and converts the data into OFM symbols.

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

Next, the receiver 950 will be described. The receiver 950 includes an A / D converter 951, a CP remover 952, a serial / parallel converter 953, an FFT converter 954 having N sizes, and an equalizer 955. ), A synchronization and channel estimator 956, a parallel / serial converter 957, and a demodulator 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 by the CP remover 952 is a signal composed of valid OMD data only. The signal from which the CP has been removed is input to the serial / parallel converter 953, processed in parallel, and output to the FFT processor 954. The FFT processor 954 performs an FFT transform process having a size of N and outputs the FFT transformed parallel data to the equalizer 955. The signal input to the equalizer 955 is output as a channel equalized signal. In addition, the signal output from the equalizer 955 is input to the parallel-to-serial converter 957 and serially converted and then output. The serially converted signal may be input to the demodulator 958 to demodulate and extract intact data. In addition, the synchronization and channel estimator 956 acquires symbol synchronization, and performs channel estimation for tap setting of the equalizer 955. Meanwhile, the length of the CP to be removed is set by detecting 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 included in a radio resource control (RRC) message instead of a physical layer signal. In other words, CP length information of each of the downlink and the uplink to be used in the next period may be included in the SIB2 message and transmitted to the terminal.

On the other hand, embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope 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 can be carried out in addition to the embodiments disclosed herein.

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

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;

7 is a diagram illustrating a signal flow between a base station and terminals in a mobile communication system whose CP length is changed according to a channel environment according to an embodiment of the present invention.

Claims

In the method of changing the cyclic prefix length at the base station,

Determining a cyclic prefix length by determining a channel state during data transmission;

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

And transmitting a downlink reference signal added with the cyclic prefix length change information to a terminal.

The method of claim 1,

And inserting the determined cyclic prefix into the transmission data and transmitting the cyclic prefix to the terminal.

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

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

The method of claim 1, wherein the determining

And receiving an uplink reference signal including a cyclic prefix length change request from the terminal.

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

And generating and changing a sequence-shift pattern used to generate the uplink reference signal.

Determining, by the terminal, the cyclic prefix length according to the channel state during data transmission;

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

And transmitting, by the terminal, an uplink reference signal including the request for changing the cyclic prefix length to a base station.

The method of claim 6,

Determining, by the base station, the cyclic prefix length of a next period by detecting the cyclic prefix length change request included in the received uplink reference signal;

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

And the base station inserting the cyclic prefix of the determined length into the transmission data and transmitting the cyclic prefix to the terminal.

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

A cyclic prefix length determination unit for detecting a channel state and determining a cyclic prefix length, and a cyclic prefix length information generator for generating cyclic prefix length change information by comparing the determined cyclic prefix length with a current cyclic prefix length. A base station including a downlink reference signal generator for generating a downlink reference signal added with the cyclic prefix length change information, and a modulator for modulating the data by inserting the cyclic prefix of the determined length during data transmission into transmission data; and

And a demodulation unit configured to demodulate data by removing the cyclic transpose of the determined length.

The method of claim 9, wherein the downlink reference signal generation unit

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

The method of claim 9, wherein the terminal

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 generation unit for generating a cyclic prefix length change request by comparing the determined cyclic prefix length with a current cyclic prefix length;

And an uplink reference signal generator configured to generate an uplink reference signal added with the cyclic prefix length change request.

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

And adding the cyclic prefix 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

A wireless communication system characterized in that the transmission to the terminal via a downlink reference signal channel.

The method of claim 13, wherein the modulated data is

A wireless communication system, characterized in that transmitted to the terminal via a downlink data channel.