KR20070061027A - Control method for fft window positioning in multiband ofdm uwb system - Google Patents

Abstract

A controlling method for FFT(Fast Fourier Transform) window positioning in an MB-OFDM UWB(Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) system is provided to obtain an optimal receiving environment in a simple way through a MAC-PHY interface standard without correcting additional complex algorithm to overcome a sampling clock offset and a multipath fading environment. A controlling method for FFT window positioning in an MB-OFDM UWB system includes the steps of: obtaining an initial FFT window position and a frequency hopping position(801); modulating a receiving signal by using the FFT window position and the frequency hopping position obtained in the previous step(802); transmitting received data information to a MAC layer through an RX frame structure, and determining whether an error of a packet exists by using an FCS at the MAC layer(803,804); and proceeding to the modulating step if there is no error based on the result of the error determining step, and proceeding to the modulating step if there is any error after adjusting the FFT window position and the frequency hopping position by using a predetermined interface line among the MAC-PHY interfaces to change a register map(806).

Description

Fast Fourier Transform Window Positioning in Multiband Orthogonal Frequency Division Multiplexed Ultra Wideband System {Control method for FFT window positioning in multiband OFDM UWB system}

1 is a diagram illustrating an embodiment of a symbol structure of a conventional IEEE 802.11a WLAN system;

2 is a diagram illustrating an embodiment of a symbol structure of a general IEEE 802.15.3a MB-OFDM UWB system;

3 is a diagram illustrating an embodiment of a synchronization process using a preamble structure provided by an MB-OFDM UWB system and a preamble at a receiver;

4A illustrates a typical multipath impulse response,

4B is an explanatory diagram illustrating a correlation value between a received preamble OFDM symbol and a reference preamble OFDM symbol for tracking an FFT window position in a symbol timing estimation process, which is the first of the synchronization process of FIG. 3;

5 is a diagram for explaining an FFT window position adjusting method according to an embodiment of the present invention;

6 is a diagram illustrating an embodiment of a frame structure of an MB-OFDM UWB system to which the present invention is applied;

7 is a diagram illustrating an embodiment of a Mac-physical layer interface in the FFT window position adjusting method according to the present invention;

8 is a flowchart illustrating an embodiment of an FFT window position adjusting method according to the present invention.

The present invention is a multi-band orthogonal frequency division multiplexing ultra-wideband (hereinafter referred to as "MB-OFDM UWB") system using a time frequency hopping scheme which is being standardized by the IEEE802.15.3a physical layer protocol (Alt-PHY). Overcomes the effects of sampling clock offset and multipath due to ultra-wideband transmission characteristics, which can be caused by the frequency offset of the local oscillator (LO) in the transmit / receive period. The present invention relates to a fast Fourier transform window position adjusting method in an MB-OFDM UWB system capable of increasing a packet reception probability.

UWB (Ultra Wide Band) is a high-speed wireless communication standard that uses the frequency range of 3.1 ~ 10.6㎓ and adopts MB-OFDM method developed by "Texas Instrument". MB-OFDM UWB method can transmit / receive video such as video easily because it can transmit 10 times faster and large capacity than existing Wi-Fi.

1 is a diagram illustrating an embodiment of a symbol structure of a conventional IEEE 802.11a WLAN system.

The symbol structure of a WLAN system such as IEEE 802.11a is 64 samples 101 and 16 CPs to be used as fast Fourier transform (FFT) inputs. Prefix 102).

In the configuration of the symbol as shown in FIG. 1, the effect of multipath using 16 cyclic prefixes (CP) 102 before 64 samples 101 to be used as actual FFT inputs. The FFT Window Transition Phenomena by Sampling Clock Offset evaluates the amount of phase shift during the tracking process, and sets the FFT window position in the initial synchronization process whenever necessary. The method of restoring to an initial FFT window position was mainly used.

In Korean Patent Laid-Open No. 2001-0083190, pilots are extracted from a fast Fourier transform, an equalized OFDM signal in an OFDM system receiver, and the extracted pilots are processed to derive an FFT window adjustment factor and an associated equalizer tap adjustment value. Using this value, we present a method for simultaneously controlling the FFT window position correction and the phase of the equalizer tap.

In Korean Laid-Open Patent Publication No. 2001-0045947, if the fast Fourier transform window timing is set in the initial acquisition mode and the correction is required in the tracking mode, it is performed in the time domain as it is, and the discontinuity of the phases generated from the fast Fourier transform is performed. A timing correction apparatus and method for a digital broadcast receiver for tracking through a phase rerotation at a rear end of a converter are described.

)이 있을 경우 FFT 후의 각 파일롯 심볼(pilot symbol) 위치에서의 위상 오차가 파일롯 위치 i와 타임 옵셋

에 비례한다는 특성을 이용하여 OFDM 심볼 내의 위치에 따른 타임 옵셋(time offset) 양을 추정하고 평균을 취하는 최대 유사도(ML : Maximum Likelihood) 추정 방법을 이용하는 이론적인 수식과 실제 간략화된 구현 방안을 제시하였다.In the paper "Tracking of time misalignments for OFDM systems in multipath fading channels," published in IEEE Transactions On Consumer Electronics, VOL. 48, NO. 4, November 2002, a specific time offset is based on a well-known OFDM signal model. ) (

), The phase error at each pilot symbol position after FFT is equal to the pilot position i and time offset.

We propose a theoretical formula and a simplified implementation method using the method of estimating the maximum likelihood (ML) that estimates and averages the amount of time offset according to the position in an OFDM symbol using the property of proportional to. .

MB-OFDM UWB system transmits OFDM symbols according to TF hopping pattern using various frequencies, and phase rotation in demodulation stage by sampling clock offset due to OFDM characteristics. Very sensitive to In addition, since the MB-OFDM UWB system transmits with 528MHz bandwidth, it exhibits unique performance degradation characteristics due to the multipath effect and other broadband channel models experienced by other narrowband systems such as the IEEE 802.11a WLAN system. .

Due to the characteristics of the ultra-wideband channel model, in demodulating the transmission signal of the MB-OFDM UWB system, it is MB to maintain the FFT window obtained by using the correlation characteristics of the preamble during the initial synchronization process. There is a limit to properly recover the OFDM UWB signal.

In more detail, the MB-OFDM UWB system using Time Frequency Hopping, which is being standardized by the IEEE802.15.3a Alternate Physical Layer Protocol (Alt-PHY), is implemented in a full digital manner. In order to solve the FFT window transition problem caused by Sampling Clock Offset, the method of restoring the FFT window position to the initial FFT window position set in the initial synchronization process is a very wideband multipath. (Multipath) There was a problem that can not completely solve the performance degradation due to fading.

The present invention has been proposed to solve the above problems, and in the receiver of the MB-OFDM UWB system using the Time Frequency Hopping method which is being standardized by the IEEE802.15.3a Alternate Physical Layer Protocol (Alt-PHY). By adjusting the FFT window position, MB-OFDM can simultaneously overcome the FFT window transition caused by Sampling Clock Offset and performance degradation caused by the effect of ultra-wideband multipath channel. An object of the present invention is to provide a fast Fourier transform window position adjustment method in a UWB system.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The method of the present invention for achieving the above object, in the fast Fourier transform window position adjustment method in a multi-band orthogonal frequency division multiplexing ultra-wideband system (MB-OFDM UWB), the initial FFT window position and frequency hopping ( Frequency hopping) initial position acquisition step; Demodulating the received signal using the FFT window position and the frequency hopping position obtained in the initial position obtaining step; An error determination step of transmitting the received data information to the MAC layer using a RX frame structure, and determining whether or not there is an error of a packet using a frame check sequence (FCS) in the MAC layer. ; And as a result of the determination of the error determination step, if there is no error, proceeds to the demodulation step. If there is an error, the FFT is changed by changing a register map using a predetermined interface line among MAC-PHY interfaces. And adjusting the window position and the frequency hopping position, and then proceeding to the demodulation step.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an embodiment of a symbol structure of a general IEEE 802.15.3a MB-OFDM UWB system.

As shown in FIG. 2, the symbol of the MB-OFDM UWB system includes a guard section 32 zero, five zeros 201 for channel switching, and 128 points to be used as inputs of the FFT. Point) 202.

The symbol of the MB-OFDM UWB system has a shorter time interval than the symbol of the IEEE 802.11a WLAN system of FIG. 1, but the sampling clock is much higher, so that the samples are more samples. It is composed. Due to the symbol characteristics of the MB-OFDM UWB system, the received signal undergoes ultra-wideband multipath fading.

Meanwhile, in the present invention, in order to overcome the multipath phenomenon, a guard section 32, which is relatively longer than 16 samples, which is a guard section provided by the IEEE 802.11a WLAN system, is provided. Considering zero and five zeros for channel switching, a method of changing the FFT window position and a channel switching position and a method of executing the same are described in detail below.

3 is a diagram illustrating an embodiment of a synchronization process using a preamble structure provided by an MB-OFDM UWB system and a preamble at a receiver.

As shown in FIG. 3, the initial FFT window position and frequency hopping position are symbol timing, which is the first of the synchronization algorithms using the packet sequence (PS) symbols of the preamble. Symbol timing estimation is determined through a synchronization process.

4A is a diagram illustrating a general multipath impulse response, and FIG. 4B is a reception preamble OFDM symbol and a reference preamble OFDM for tracking the FFT window position in symbol timing estimation, which is the first of the synchronization process of FIG. 3. An exemplary explanatory diagram showing a correlation value with a symbol.

When there is a multipath environment as shown in FIG. 4A, between a packet sequence (PS) symbol and a reference packet sequence (Reference PS) in a received preamble that have undergone such multipath fading When the correlation value is detected, it is the same as that of FIG. 4B. Most of the points where the double peak is detected are determined as the initial FFT window position.

FIG. 5 is a diagram illustrating an embodiment of a method for adjusting an FFT window position according to the present invention, and overcomes the effects of fading caused by a sampling clock offset and an ultra-wideband multipath channel. The following shows an example in which the receiver is designed in four parallels to adjust the FFT window position and the frequency hopping position and generate the FFT input value to increase the reception probability.

Since the receiver is designed in 4 parallel in FIG. 5, the FFT window position and the frequency hopping position, which can be corrected in one clock, must be adjusted by a multiple of four. In other words, in a four parallel reception structure as shown in FIG. 5, the FFT window position adjustment is set to 0, 4, 8, 12, ... within the guard interval (32 zeros). It should be adjusted. In this case, the frequency hopping position should always be set 5 samples or more ahead of the FFT window position, and to overcome multipath fading in IEEE 802.11a WLAN system. To give the same effect as the Cyclic Prefix (CP) used, up to 32 samples from the end of the actual 128-point FFT window are combined with the samples in front of the FFT window and used as the FFT input. do.

That is, the symbol structure of the MB-OFDM UWB system is an OFDM symbol to transmit samples of about the last quarter of the OFDM symbol to overcome multipath fading, unlike the existing IEEE 802.11a WLAN system. Zeros are sent instead of the cyclic prefix that is repeatedly transmitted at the beginning, and up to 32 from the end of the actual 128 point FFT window to give the receiver the same effect as the cyclic prefix. The sample is combined with the samples in front of the FFT window and used as the FFT input.

In the FFT window setting that sets the FFT input value range, in the case of MB-OFDM UWB system, the amount of sampling clock offset, transmission mode, payload transmission length, and ultra-wideband channel model By adjusting the FFT window position and the frequency switching position that should be located at least 5 samples before the FFT window position in accordance with fading, the received packet error at the receiving end ( It is characterized by reducing the error rate.

[Table 1] below shows 480Mbps mode among the data rates that can be provided by MB-OFDM UWB system to 100 profiles of CM1 provided by UWB channel model at 50dB SNR (Signal to Noise Ratio). The packet error situation for each profile obtained by adjusting the FFT window position and the frequency hopping position is shown.

FFT Window Position = 0, Frequency Hopping Position = -8 FFT Window Position = -4, Frequency Hopping Position = -12 FFT Window Position = -8, Frequency Hopping Position = -16 FFT Window Position = -12, Frequency Hopping Position = -20 Profile_Num Header Payload Header Payload Header Payload Header Payload One 0 0 0 0 0 0 0 0 2 0 0.0002 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 5 0 0.0021 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 11 0 0.021 0 0 0 0 0 0 12 0 0.033 0 0 0 0.0022 0 0.0005 13 0 0 0 0 0 0 0 0 14 0 0 0 0 0 0 0 0 15 0 0.082 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 17 5 0.4681 11 0.4554 0 0.4066 0 0 18 0 0 0 0 0 0 0 0 19 0 0 0 0 0 0 0 0 20 0 0 0 0 0 0 0 0.0002 21 0 0 0 0 0 0 0 0 22 0 0 0 0 0 0 0 0 23 0 0.0467 0 0.0136 0 0 0 0 24 0 0 0 0 0 0 0 0 25 0 0 0 0 0 0 0 0 26 0 0 0 0 0 0 0 0 27 0 0.0031 0 0.3588 0 0 0 0 28 0 0 0 0 0 0 0 0 29 0 0 0 0 0 0 0 0 30 0 0 0 0 0 0 0 0 31 0 0 0 0 0 0 0 0 32 0 0 0 0 0 0 0 0 33 0 0 0 0 0 0 0 0 34 0 0 0 0 0 0 0 0 35 0 0 0 0 0 0 0 0.0001 36 0 0 0 0 0 0 0 0 37 0 0 0 0 0 0 0 0 38 0 0.0002 0 0 0 0 0 0 39 0 0 0 0 0 0 0 0 40 0 0 0 0 0 0 0 0 41 0 0.0005 0 0 0 0 0 0 42 0 0 0 0 0 0 0 0 43 0 0 0 0 0 0 0 0 44 0 0 0 0 0 0 0 0 45 0 0 0 0 0 0 0 0 46 0 0 0 0 0 0 0 0 47 0 0 0 0 0 0 0 0 48 0 0.0407 0 0 0 0 0 0 49 0 0 0 0 0 0 0 0 50 0 0 0 0 0 0 0 0 51 0 0 0 0 0 0 0 0 52 0 0 0 0 0 0 0 0 53 0 0 0 0 0 0 0 0 54 0 0.0054 0 0 0 0 0 0 55 0 0 0 0 0 0 0 0 56 0 0 0 0 0 0 0 0 57 0 0 0 0 0 0 0 0 58 0 0 0 0 0 0 0 0 59 0 0.0516 0 0 0 0 0 0 60 0 0 0 0 0 0 0 0 61 0 0 0 0 0 0 0 0 62 0 0 0 0 0 0 0 0 63 0 0 0 0 0 0 0 0 64 0 0 0 0 0 0 0 0 65 0 0 0 0 0 0 0 0 66 0 0 0 0 0 0 0 0 67 0 0.0175 0 0 0 0 0 0 68 0 0 0 0 0 0 0 0 69 0 0 0 0 0 0 0 0 70 0 0 0 0 0 0 0 0 71 0 0 0 0 0 0 0 0 72 0 0 0 0 0 0 0 0 73 0 0 0 0 0 0 0 0 74 0 0.0153 0 0 0 0 0 0 75 0 0 0 0 0 0 0 0 76 0 0.0002 0 0 0 0 0 0 77 0 0 0 0 0 0 0 0 78 0 0 0 0 0 0 0 0 79 0 0 0 0 0 0 0 0 80 0 0 0 0 0 0 0 0 81 0 0 0 0 0 0 0 0 82 0 0 0 0 0 0 0 0 83 0 0 0 0 0 0 0 0 84 0 0.0127 0 0 0 0 0 0 85 0 0 0 0 0 0 0 0 86 0 0.0064 0 0 0 0 0 0 87 0 0 0 0 0 0 0 0 88 0 0.007 0 0.0034 0 0 0 0 89 0 0 0 0 0 0 0 0 90 0 0 0 0 0 0 0 0 91 0 0 0 0 0 0 0 0 92 0 0 0 0 0 0 0 0 93 0 0 0 0 0 0 0 0 94 0 0 0 0 0 0 0 0 95 0 0.0004 0 0 0 0 0 0 96 0 0 0 0 0 0 0 0 97 0 0 0 0 0 0 0 0 98 0 0 0 0 0 0 0 0 99 0 0.0006 0 0 0 0 0 0.0004 100 0 0 0 0 0 0 0 0

Table 2 below shows the average Bit Error Rate (BER) and PER (Packet Error Rate) and the worst 10 profiles for the 100 profiles obtained in Table 1 above. Average BER and PER for 90 profiles are shown.

division FFT Window Position = 0, Frequency Hopping Position = -8 FFT Window Position = -4, Frequency Hopping Position = -12 FFT Window Position = -8, Frequency Hopping Position = -16 FFT Window Position = -12, Frequency Hopping Position = -20 PER (100) 0.2100 0.0400 0.0200 0.0400 BER (100) 0.00815 0.00831 0.00409 0.00001 BER (90) 0.000394444 3.77778E-05 0 8.16889E-06 PER (90) 0.099 0.009 0 0.027

In the case of MB-OFDM UWB system that undergoes ultra-wideband multipath fading from the results of Tables 1 and 2, the same multiplication is performed by adjusting the FFT window position and frequency hopping position. It can be seen that the performance can be greatly improved in a profile environment that suffers from multipath fading. This suggests that the method proposed in the present invention can greatly increase the probability of receiving packets at the receiving end without complicated algorithm modification. It is showing that it can be done.

6 is a diagram illustrating an embodiment of a frame structure of an MB-OFDM UWB system to which the present invention is applied.

As shown in FIG. 6, the frame structure of the MB-OFDM UWB system includes a transmit frame (TX frame) and a receive frame (RX frame).

By using MAC-PHY interface specification, frame check strings (FCS) generated at MAC layer and transmitted through modem transmitter are demodulated at modem receiver and sent to MAC layer. In the MAC layer, the frame check sequence FCS may be checked to determine whether an error occurs in the entire packet.

7 is a diagram illustrating an embodiment of a Mac-physical layer interface in the FFT window position adjusting method according to the present invention.

As shown in FIG. 7, the lines used in the MAC-PHY interface are "PHY_RESET", "TX_EN", "RX_EN", "PHY_ACTIVE", "STOPC", " PCLK "," DATA_EN "," DATA [7: 0] "," CCA_STATUS "," SERIAL_DATA "," SYS_CLK ", and" RESERVED [1: 0] ".

MB-OFDM UWB system has a very small sampling clock offset so that the FFT window position transition does not occur in the packet, so the FFT window position is fixed to the position obtained in the initial synchronization process. Even in this case, a severe performance degradation occurs due to a multipath condition. In this case, packet error can be eliminated by artificially adjusting the FFT window position.

In this case, in order to properly adjust the FFT window position, the frame check string (FCS) that is raised from the MAC layer to the modem is checked, and if an error is still detected, the MAC-physical layer ( By changing the "RXCTL" register map using the "Serial-DATA" line provided in the MAC-PHY interface specification, the modem changes the FFT window position sequentially. By repeating the process of checking the MAC layer again by the MAC layer based on the changed FFT window position, it is possible to estimate the FFT window position that can best receive the environment in the real environment. have. This method has the advantage that it is possible to extract the optimal reception environment in the simplest way without any complicated algorithm when implementing the actual receiver.

On the other hand, using the "SERIAL_DATA" in the Interface Line (MAC), you can read the status of the modem from the register map in the MAC layer, and the register map to change the modem status. It can also be modified at the MAC layer.

FIG. 8 is a flowchart illustrating an FFT window position adjusting method according to an embodiment of the present invention, using a frame check sequence (FCS) of a TX frame and a RX frame as shown in FIG. 6. In the MAC layer, it is determined whether there is an error in the packet, and using the determination result, "SERIAL_DATA" is used in the MAC-PHY interface as shown in FIG. The procedure for modifying the FFT window position and frequency hopping position by changing the "RXCTL" value in the register map using a line is shown.

First, after an analog-to-digital conversion (ADC), an initial FFT window position and frequency hopping position are obtained through a timing synchronization process (801), and the obtained FFT window position and frequency hopping (Frequency) are obtained. The received signal is demodulated using the hopping position (802).

Next, the received data information is transmitted to the MAC layer using an RX frame structure (803), and the presence or absence of an error in a packet using a frame check sequence (FCS) in the MAC layer. Determination is made (804, 805).

As a result of the determination, if there is no packet error, the process proceeds to demodulating the received signal (802). If there is a packet error, a register map is used by using a "SERIAL_DATA" line in a MAC-PHY interface. Next, after adjusting the FFT window position and the frequency hopping position by changing 806, the process proceeds to demodulating the received signal 802.

At this time, the FFT Window position range which can be adjusted by using the "RXCTL" register map information should be limited within the guard section (32 zeros), and in the "RXCTL" register map. If a packet error is not corrected within a definable range of FFT window positioning, it means that the modem is experiencing insurmountable fading.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention provides a sampling clock offset and a multipath in an MB-OFDM UWB system using a time frequency hopping scheme that is being standardized by the IEEE802.15.3a physical layer protocol (Alt-PHY). In order to overcome the performance degradation caused by (Multipath), an additional complex algorithm is used to overcome the sampling clock offset and ultra-wideband multipath fading environment when the actual receiver is implemented by adjusting the FFT window. Using the MAC-PHY interface (IF) standard without modification, it is possible to extract the optimal reception environment in the simplest way.

Claims (10)

A fast Fourier transform window position adjusting method in a multi-band orthogonal frequency division multiplexing ultra wideband system (MB-OFDM UWB), An initial position acquiring step of acquiring an initial FFT window position and a frequency hopping position; Demodulating the received signal using the FFT window position and the frequency hopping position obtained in the initial position obtaining step; An error determination step of transmitting the received data information to the MAC layer using a RX frame structure, and determining whether or not there is an error of a packet using a frame check sequence (FCS) in the MAC layer. ; And As a result of the determination of the error determination step, if there is no error, the process proceeds to the demodulation step. If there is an error, the FFT window is changed by changing a register map using a predetermined interface line among MAC-PHY interfaces. After adjusting the position and the frequency hopping position, the position adjusting step proceeds to the demodulation step. Fast Fourier transform window position adjustment method comprising a. The method of claim 1, In the position adjusting step, Fast Fourier transform window position adjustment method characterized in that for adjusting the FFT window position in the guard interval (32 zeros) by using the register map (Register Map) information. The method of claim 2, The predetermined interface line, Fast Fourier transform window position adjustment method characterized in that the "SERIAL_DATA" line of the MAC-PHY layer (MAC-PHY) interface. The method of claim 3, wherein In the position adjusting step, The state of the modem is read from the register map in the MAC layer using "SERIAL_DATA" in the MAC-PHY interface line, and the MAC is read. And changing a modem state of the register map in a layer. The method of claim 4, wherein In the position adjusting step, As an error is continuously detected by checking a frame check sequence (FCS) in the MAC layer, the MAC-PHY interface standard "Serial-" is proposed. Change the "RXCTL" register map using the DATA "line to allow the modem to change the FFT window position sequentially, and the frame check sequence (FCS) based on the changed FFT window position. The method of claim 4, wherein the FFT window position is adjusted by repeating the check of the MAC layer again. The method of claim 2, The FFT window is, And the frequency hopping position is set 5 samples or more ahead of the FFT window position. The method according to any one of claims 1 to 6, The FFT window is, Fast Fourier which transmits zeros in front of the OFDM symbol and uses up to 32 samples from the end of the 128-point FFT window as the FFT input by combining the samples in front of the FFT window. How to adjust the translation window position. The method of claim 7, wherein The FFT window is, Frequency switching to be located at least 5 samples ahead of the FFT window position and FFT window position, depending on the amount of sampling clock offset, transmission mode, payload transmission length, and fading by the ultra-wideband channel model (Frequency Switching) A fast Fourier transform window position adjustment method characterized in that the setting by adjusting the position. The method of claim 7, wherein In the initial position acquisition step, Synchronization process of symbol timing estimation, which is the first of the synchronization algorithms using the packet sequence (PS) symbols of the preamble for the initial FFT window position and the frequency hopping position. Fast Fourier transform window position adjustment method characterized in that determined through. The method of claim 9, In the initial position acquisition step, Detecting a correlation value between a packet sequence (PS) symbol in a received preamble and a reference packet sequence (Reference PS) to determine a point where a double peak is detected as an initial FFT window position. Fast Fourier transform window position adjustment method, characterized in that.

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