KR20090114929A - Device and method for assigning pilot in orthogonal frequency division multiplexing transceiver - Google Patents

Abstract

PURPOSE: A device and a method for assigning a pilot in an orthogonal frequency division multiplexing transceiver are provided to improve transmission efficiency by controlling a bandwidth allocated to pilot and data. CONSTITUTION: In a device and a method for assigning a pilot in an orthogonal frequency division multiplexing transceiver, a channel impulse response estimator(110) estimates a channel impulse response signal from a received channel signal. A pilot position controller(130) detects group information including a number of the multi-path group, path delay between each group, and the length between groups in a presumed channel impulse response signal. A pilot position controller determines a pilot assignment information by applies detected group information to a number of routing group. The pilot position controller includes a group information detector and a pilot pattern selector.

Description

DEVICE AND METHOD FOR ASSIGNING PILOT IN ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING TRANSCEIVER}

The present invention relates to a signal processing apparatus and method of a modem, and more particularly, to a pilot allocation apparatus and method of an OFDM transceiver.

In general, orthogonal frequency division multiplexing transceiver (OFDM) technology is a transmission / reception scheme for performing transmission and reception of signals by dividing a broadband band into a plurality of narrow bands. In addition, such an OFDM transmission and reception method is actively reflected in various wireless communication technologies due to high transmission efficiency and ease of implementation due to the development of VLSI technology. The biggest advantage of the OFDM technique is an efficient one-tap equalizer, and a simple structure allows efficient reception recovery if only channel estimation is accurate.

The wireless channel environment has two characteristics, one that is very time-varying and the other is that it has a fairly large frequency selectivity for long channel delays (for channels with long delay spreads). . In order to estimate such a channel, several methods of pilot allocation are possible. In this case, it should be noted that the frequency and time interval to which the pilots are allocated should be narrow enough according to the Nyquist sampling theory. This is related in time to the Doppler frequency and in the frequency direction to the length of the multipath of the channel.

As described above, for accurate channel estimation in an OFDM transceiver, a bandwidth for pilots having a certain density or more (or more specifically, satisfying a Nyquist condition) must be allocated. However, allocating pilots at higher densities means that data transmission efficiency is lower. Therefore, if a channel of sufficient density can be estimated sufficiently, it is not necessary to allocate many pilots at the expense of bandwidth.

In general, pilots need a higher density of pilot allocation to prevent aliasing as the Doppler frequency increases in the time direction and the delay of the multipath channel in the frequency direction. In this case, the OFDM channel environment may be a situation in which multiple multipath channels are separated from each other with a very long delay. For example, broadcast receivers (e.g., DMB, DVB, etc.) that use OFDM transmission / reception schemes may not synchronize timing with global positioning systems (GPS), in which case multiple multipath channels are separated from each other with a long delay. It can often happen. This environment can also occur in mobile communications. As in the case of the long delay spread channel, the longer the impulse response of the channel, the higher frequency sampling is required to avoid aliasing, which means that a higher density pilot allocation is required. Otherwise, aliasing will occur and distortion will occur in channel estimation.

In general, however, channel paths with significant levels of power are concentrated at some location, and there are no real cases where there are paths with large power over the entire delay spread. In the conventional case, however, as the channel impulse response becomes longer, as in the case of a long delay spread channel, a higher sampling frequency is used to avoid aliasing, which leads to a higher density pilot.

The present invention corresponds to the signal processing and transmission and reception signal processing technology of the OFDM transceiver. The technique of the present invention corresponds to a channel estimating technique among the signal processing techniques of an FDM transceiver, and the channel estimating technique performs effective channel distortion recovery and error correction at a receiver by estimating a fixed or time-varying channel as accurately as possible in a wired or wireless channel environment. To correctly recover the transmitted data.

OFDM transceivers require higher frequency sampling to avoid aliasing as the channel impulse response becomes longer as in the case of long delay spread channels. In general, however, channel paths with significant levels of power are concentrated at some location, and there are no real cases where there are paths with large power over the entire delay spread. In the embodiment of the present invention, the receiving side estimates the CIR of the received signal, analyzes the estimated channel impulse response, and uses a technique for determining a pilot sequence having a corresponding appropriate sampling frequency. It is possible to perform channel estimation without error even if the density is not increased. That is, in the embodiment of the present invention, the receiving side minimizes the sampling frequency according to the channel impulse response or uses an undersampling technique in some cases, and the transmitting side adjusts the pilot density according to the adjusted sampling frequency of the receiving side. The present invention proposes an OFDM transceiver and method for improving performance and improving data transmission efficiency.

In an orthogonal frequency multiple access communication apparatus according to an embodiment of the present invention, a channel impulse response estimator estimates a channel impulse response signal from a received channel signal, the number of multipath groups in the estimated channel impulse response signal, and a path between each group. And after detecting group information such as delay and length between groups, a pilot position controller is configured to determine pilot allocation information by applying the detected group information to the condition of the number of path groups.

The pilot position controller includes a group information detector for detecting group information of a number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response, and the number of corresponding multipath groups using the group information. And a pilot pattern selector for selecting pilot allocation information for allocating a pilot pattern of the lowest sampling frequency that satisfies the condition. The pilot pattern selector may include indexes of the sequence mapping table sorted by a pilot sampling frequency, and output the pattern index of the sequence mapping table corresponding to the selected sampling frequency as the pilot allocation information. The group information detector determines the number of path groups by centering the center of the channel impulse response signal, comparing the channel impulse response signal with a threshold value, and delaying each path group from the start and end positions in each group. The length can be calculated and the delay length between the path groups can be calculated.

The channel impulse response estimator comprises: a first channel impulse response estimator for estimating a channel impulse response signal of a first type from an entire FFT transformed signal, and a channel impulse response signal of a second type at a pilot position of the FFT transformed signal; The second channel impulse response estimator and the pattern matcher for estimating the final channel impulse response by matching the patterns of the first and second types of channel impulse response signals.

The transmitting side may include a pilot generator for receiving the pilot assignment information and generating a pilot sequence according to the pilot assignment information and multiplexing the transmission data. The pilot generator may include a sequence mapping table for storing the pilot patterns sorted by the sampling frequency, and generate a pilot sequence of the sequence mapping table corresponding to the received pilot assignment information.

The receiving side may further include a channel estimator for generating a channel estimating signal after restoring the change according to the pilot density control by using the group information and the pilot assignment information, and transmitting the received signal to an equalizer. The channel estimator may include an IDFT interpolator for IDFT interpolating an FFT transform signal, an image remover for removing an image included in an output of the DFT interpolator by the group information, and an output of the image remover. A delay shifter shifted by a pilot sampling frequency, and a DFT converting unit for DFT converting the output of the delay shifter.

In addition, the orthogonal frequency multiplexing apparatus of a mobile terminal according to an embodiment of the present invention comprises: a first channel impulse response estimator for estimating a channel impulse response signal of a first type from the entire received signal; A channel impulse response estimator comprising a second channel impulse response estimator for estimating two types of channel impulse response signals and a pattern matcher for matching the patterns of the first and second types of channel impulse responses to estimate a final channel impulse response; An estimator, a group information detector for detecting group information of the number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response, and applying to a condition of the number of the multipath groups of the group information Pilot selector for selecting pilot allocation information for allocating the pilot pattern of the lowest sampling frequency satisfying the It characterized by consisting of a pilot controller configured.

In addition, a portable terminal of an orthogonal frequency multiple access communication apparatus according to an embodiment of the present invention includes a first channel impulse response estimator for estimating a channel impulse response signal of a first type from an entire FFT transformed signal, and a pilot of the FFT transformed signal. A channel impulse response consisting of a second channel impulse response estimator for calculating a second type of channel impulse response signal at a position and a pattern matcher for matching a pattern of the first and second type channel impulse responses to estimate a final channel impulse response The base station includes a group information detector for detecting group information of the number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response, and the corresponding multipath group using the group information. Select pilot assignment information for allocating the pilot pattern of the lowest sampling rate that satisfies the condition It characterized in that the pilot controller consists of consisting of the pilot pattern selector.

In addition, a portable terminal of an orthogonal frequency multiple access communication apparatus according to an embodiment of the present invention includes a first channel impulse response estimator for estimating a channel impulse response signal of a first type from an entire FFT transformed signal, and a pilot of the FFT transformed signal. A channel comprising a second channel impulse response estimator for estimating a channel impulse response signal of a second type at a position and a pattern matcher for matching a pattern of the channel impulse responses of the first and second types to estimate a final channel impulse response; An impulse response estimator and a group information detector for calculating group information of the number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response, and the base station uses the group information to determine the multipath. Select pilot allocation information for allocating the pilot pattern of the lowest sampling rate that satisfies the condition G of the group. It is characterized in that it consists of a pilot pattern selector.

In addition, the orthogonal frequency multiple access communication method according to an embodiment of the present invention, the process of estimating the channel impulse response signal from the received channel signal, the number of multipath groups in the estimated channel impulse response signal, the path delay between each group and After detecting the group information such as the length of the group, and using the detected group information characterized in that the process of determining the pilot allocation information for adjusting the sampling frequency.

The process of generating pilot assignment information from the channel impulse response may include detecting group information of the number of multipath groups, path delay length between groups, and length between groups from the channel impulse response, and analyzing the group information. In this case, the pilot allocation information for allocating the pilot pattern of the lowest sampling frequency satisfying the condition of the number of the multipath groups may be determined.

The estimating of the channel impulse response may include estimating the channel impulse response of the first type from the entire FFT-converted signal of the received signal, and the channel of the second type at the pilot position of the FFT-converted signal of the received signal. Estimating an impulse response and estimating a final channel impulse response by matching patterns of the first and second channel impulse responses.

In addition, the orthogonal frequency access communication method of a mobile terminal according to an embodiment of the present invention estimates a channel impulse response of a first type from all FFT-converted signals of a received signal, and estimates a channel impulse response from the FFT-converted signal of the received signal. Estimating the channel impulse response of the second form, and estimating the final channel impulse response by matching the pattern of the channel impulse responses of the first and second forms, the number of multipath groups from the channel impulse response, and each group. Detecting the group information of the path delay length between the groups and the length between the groups; and analyzing the group information to obtain pilot allocation information for allocating the pilot pattern of the lowest sampling frequency satisfying the condition of the number of the multipath group. It is characterized by the process of determining.

In addition, in the pilot allocation method according to the embodiment of the present invention, the portable terminal estimates the channel-type impulse response of the first type from the entire FFT-converted signal, and obtains the channel-type impulse response of the second type from the signal of the FFT-converted pilot position. Estimating a final channel impulse response by matching patterns of channel impulse responses of the first and second types, and the base station determines the number of multipath groups from each channel impulse response and a path delay between the groups. Detecting group information of a length and a length between groups, and applying pilot information to allocate a pilot pattern having a lowest sampling rate that satisfies the condition by applying the group information to the number G of the multipath groups. Pilot assignment information received from the sequence mapping table storing the selection process and the pilot patterns sorted by the sampling frequency It performs a process for generating a pilot sequence corresponding to.

As described above, in the mobile terminal using the OFDM transceiver, the transmission efficiency can be improved by reducing the bandwidth allocated to the pilot and increasing the bandwidth allocated to the data. Currently, portable terminals tend to be used in conjunction with the location information of the terminal, and the pilot allocation method according to an embodiment of the present invention is large in a situation where the location of the terminal is subdivided in a cell by using spatial division multiple access (SDMA). Can have efficiency.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the same components in the figures represent the same numerals wherever possible.

In general, in a wireless communication environment, channel paths with significant high levels of power are concentrated in some locations, and there are virtually no paths with high power over the spread of the entire delay. Therefore, the OFDM transceiver can perform channel estimation without error if the appropriate sampling technique (eg, undersampling technique) that analyzes the received signal and adjusts the sampling frequency in some cases does not increase the pilot density more than necessary. have. The present invention provides an apparatus and method for adjusting the pilot density according to the channel impulse response to increase the transmission and reception performance and improve the data transmission efficiency.

To this end, in an OFDM transceiver according to an embodiment of the present invention, a receiving end estimates a channel impulse response (hereinafter referred to as a CIR) of a receiving channel, determines an actual required pilot density from the estimated CIR, and transmits the same to the transmitting end. Inform. Then, the transmitting end multiplexes and transmits pilot symbols varying with the set pilot density in data symbols.

In the embodiment of the present invention, the term "pilot allocation information" is a term for selecting a pilot sequence in the mapping table of the pilot sequence. Here, the pilot allocation information can be generated in various ways, and in the embodiment of the present invention, it will be described on the assumption that it is a pattern index that can be used as an address of a sequence mapping table that stores the pilot sequence. The term "group information" refers to information detected by an estimated channel impulse response. In an embodiment of the present invention, the term "group information" may be the number of multipath groups, the length of the path delay of each group, the length of each group, and the like.

In addition, the term "sampling frequency" may be the sampling frequency of the pilot, and the sampling frequency may be the sampling frequency of the pilot sequence having an appropriate pilot density by the CIR measurement of the receiver. In an embodiment of the present invention, the pilot density is adjusted according to the channel impulse response, and the adjustment of the pilot density may be such that channel estimation can be performed without error at the receiving side. In this case, when the pilot density is decreased according to the channel impulse response, undersampling is performed. In this case, the receiver can perform channel estimation without error even from a received signal having a low pilot density. In the embodiment of the present invention, the case of undersampling is shown as an example. The same applies to general sampling. In the following description, adjustment of the pilot density or adjustment of the sampling frequency will be used in the same sense, and one example of such a method may be an undersampling technique.

1 is a diagram illustrating a structure of an OFDM transceiver according to an embodiment of the present invention.

Referring to the configuration of FIG. 1, the receiver may include a CIR estimator 110 and a pilot position controller 130 for generating pilot allocation information for allocating a pilot sequence having an appropriate pilot density by estimating the CIR from a received signal. May include a pilot generator 150 for generating a pilot symbol according to the determined pilot pattern. The receiver includes a channel estimator 140 for reconstructing the pilot sequence of which the pilot density is adjusted to the original pilot sequence for channel estimation. Here, the pilot position controller 130 may be configured in the receiver and may also be configured in the transmitter. The CIR estimator 110 and / or the pilot position controller 130 may be configured in hardware or may be configured in software.

Referring to FIG. 1, a transmission operation is performed. The Tx stream generator 210 performs a function of generating data to be transmitted. A channel coder 220 performs channel coding on the transmission data stream to perform error correction coding, and a mapper 230 converts the channel coded data into data symbols. Here, the mapper 230 may use a quadrature amplitude modulation (QAM) mapper. Since the transmitter must transmit pilot symbols in addition to the data symbols during the OFDM transmission, the pilot generator 150 generates pilot symbols to be transmitted with the data symbols. In an embodiment of the present invention, the pilot generator 150 may generate a pilot symbol that is variably adjusted by pilot allocation by a receiver. The multiplexer 240 multiplexes the pilot symbols generated in the pilot generator 150 and the data symbols generated in the mapper 230, and an inverse fast fourier transform part (IFFT) 250 performs time domain data and pilot symbols in the multiplexed frequency domain. After converting the signal into a transmission band, the RF transmitter 260 filters the signal into a transmission band and then increases the frequency of the signal to a wireless signal of the transmission band.

Secondly, in the reception operation, the RF receiver 310 converts the received radio signal into falling frequency and filters the received baseband signal. A fast fourier transform part (FFT) 320 converts received time component data and pilot signals into frequency components. The channel impulse response estimator 110 estimates the received channel impulse response by estimating the FFT transform signal. In this case, the CIR estimator 110 is for estimating a pilot density substantially required at the receiver. The pilot location controller 130 generates pilot assignment information for allocating an appropriate pilot using the CIR estimated by the CIR estimator 110. The pilot allocation information is transmitted to the pilot generator 150 of the transmitter.

In addition, the demultiplexer 330 of the receiver demultiplexes pilot symbols and data symbols in a received signal, and a channel estimator 170 predicts distortion in a channel from the demultiplexed pilot symbols and restores the transmission symbols to a transmission form. Generate a channel estimation signal for Since the channel estimator 170 receives a pilot signal having a pilot density adjusted, the channel estimator 170 may further include a function of removing a pilot image generated by sampling and shifting the pilot signal from which the image is removed to an appropriate position. . An equalizer 340 equalizes the demultiplexed data symbols by the channel estimation signal. Here, the equalizer 340 may use a one-tap equalizer. A demapper 350 demaps the data symbol into its original data form, a channel decoder 360 decodes the data into original data, and a data processor 370 processes the channel decoded received data stream. do.

The OFDM transceiver according to the embodiment of the present invention having the configuration as shown in FIG. 1 can increase the transmission efficiency by appropriately adjusting the pilot density according to the shock response of the channel as described above. To this end, in an embodiment of the present invention, after estimating the CIR of the received signal, the estimated CIR is analyzed and the pilot frequency is appropriately sampled to determine a pilot pattern for adjusting the pilot density. The pilot generator of the transmitter is controlled according to the adjusted pilot pattern so as not to increase the pilot density more than necessary. In this case, the channel estimator at the receiving side can perform channel estimation without error.

In the embodiment of the present invention will be described in the order of the above CIR estimation, pilot position control, pilot generation and channel estimation.

First, a CIR estimation method according to an embodiment of the present invention will be described with reference to FIGS. 2 to 4. 2 is a diagram illustrating an example in which one third of the N point FFT signals are pilots. FIG. 3 is a diagram showing the configuration of the CIR estimator 110 which generates the CIR of the first form as shown in FIG. 4B and the CIR of the second form as shown in FIG. 4C, and generates the desired CIR using them. 4A is a diagram showing an original CIR, FIG. 4B is a diagram showing an output CIR of a first form, and FIG. 4C is a diagram showing an output CIR of a second form.

The CIR estimator 110 estimates the CIR by receiving the FFT-converted signal, and can estimate the CIR in two ways. One method is to estimate the CIR by selecting only the pilot position signals among the entire N point FFT signals. In this case, when the pilot assumes that 1 / m is a pilot, when performing an N / m point IFFT, m CIR images repeatedly appear, and one of them may be selected as a CIR. The other method is to estimate the CIR of all N point FFT signals. This may be a method of IFFTing the result of NFT FFT output of the FFT320, and in this case, the entire CIR appears on both sides, and one of them may be selected as a CIR. The CIR estimator 110 may estimate the CIR using results of one or two methods of the CIR estimation method. In this case, a pilot transmission of relatively high density is preferable in the initial transmission stage. This is to allow the receiver to accurately estimate the CIR.

Referring to the operation of estimating the first type of CIR (type 1 CIR), the squarer 113 squares the N point FFT output output from the FFT 320, and IFFT115 IFFT transforms the output of the squarer 113 to the first. Generate a CIR of the form. At this time, the CIR of the first form is shown as the original CIR as shown in FIG. The delay type 1 estimator 117 estimates the delay distance D between the first path and the last path in the CIR of the first type as shown in FIG. 4B.

In addition, referring to the operation of estimating the second type of CIR (type 2 CIR), a descrambler 123 descrambles an N point FFT output to select an FFT output where a pilot is located, and IFFT125 selects the descrambling. IFFT transforms the FFT output of the bling pilot to generate a second type of CIR. In the following description, it is assumed that 1/3 of the N point FFT signals are pilots. In this case, when the pilot is 1/3 of N points as shown in FIG. 2, the descrambler 123 extracts N / 3 points of the pilot, and IFFT125 performs IFFT conversion on the N / 3 points of the FFT output of FIG. 4C. Generate a second form of CIR such as In this case, three CIR images may repeatedly appear in the CIR of the second form. The delay type 2 estimator 112 measures the delay distances H ₀ , H ₁ , H ₂ , ..., H _P-1 , of each path in the CIR of the second type as shown in FIG. 4C. Estimate.

Since the pattern matching (pattern matching part) 129 is a first aspect of the CIR, and a first aspect of the delay distance D with a second aspect of the CIR and the second aspect of the delay distance _{(H 0, H 1, H} 2, ... The final CIR is obtained by pattern matching with, H _P-1 ,). In this case, the pattern matcher 129 may know the location of the multipath from the CIR of the first type as shown in FIG. 4B and the value of the multipath from the CIR of the second type.

The delay distance of the CIR of the first type can be estimated as shown in FIG. 4B. First, the CIR vectors r ₀ , r ₁ , r ₂ ,..., R _N-1 , of the first form are obtained. Second, more than a certain threshold value in the vectors is considered as multipath. In this case, if the number of multipaths satisfying the multipath condition is P, the locations (n ₀ , n ₁ , n ₂ ,..., N _P-1 ,) of the multipaths may be known. Third, the distance (D = n _P-1 -n ₀ ) between the first path and the last path of the multipaths is obtained.

As described above, in the CIR of the second type, although the value of each path is accurate, it is difficult to find the starting position of the multi path because it is cyclically shifted. In order to accurately obtain the CIR, it is necessary to know which path is the first and which path is the last. To confirm this, the delay of each path is estimated first, and the case most similar to the delay distance D of the first type is regarded as the actual situation.

Here, the distance of the second type CIR may be estimated as shown in FIG. 4C. First, it is assumed that each multipath is the first multipath for all multipaths obtained in the second type of CIR. Secondly, create a hypothesis for each case where each multipath is the first path, and the distance of the first path for each hypothesis and the last path if it is cyclically shifted (H ₀ , H ₁ , H ₂ , ..., H _{Find P-1} ,).

The pattern matcher 129 is the closest to the delay distance D of the first type CIR as shown in FIG. 4B among the delay distances H ₀ , H ₁ , H ₂ ,..., H _P-1 of FIG. 4C. Perform hypothesis finding. Once the closest hypothesis is determined, the first and last paths and the overall CIR are automatically calculated. The CIR output from the pattern matcher 129 is composed of N points.

In general, when the channel has a short delay spread, the CIR estimator 110 may estimate the results as shown in FIGS. 4B and 4C, and uses only one (eg, + direction) CIR image of the first type of CIR. It is also possible to use the central portion CIR image in the second form of CIR. Originally, the length corresponding to the delay spread must be secured to the sampling frequency (in this case, it can be expressed as sampling frequency T _samp = 1 / (NfΔf) since it is time domain) so that aliasing does not occur.

Secondly, as described above, when the CIR estimator 110 generates the CIR output, the pilot position controller 130 determines an appropriate pilot allocation according to the CIR output result. 5 to 9, the operation of the pilot position controller 130 for determining the pilot allocation will be described.

 5 is a diagram showing a CIR output from the channel estimator 110, and FIG. 6 is a diagram showing the configuration of the pilot position controller 130. FIG.

5 to 6, the configuration and operation of the pilot position controller 130 are described. A group detector 133 inputs a CIR having the same characteristics as that of FIG. 5, and the number of multipath groups from the CIR ( G), the path delay length T _D of each group, and the lengths T _G1 , T _G2 , T _G3 ,...

In this case, the group detector 133 may obtain the number of the multipath groups, the path delay length, and the length between each group as follows. First, CIR vectors are received and centered so that the center is the origin as shown in FIG. This corresponds to delay in the time domain and phase rotation in the frequency domain. Second, calculate the power of each multipath. The multipath power calculation method assumes that the multipath group starts when a certain threshold is exceeded, and that the multipath group ends when it falls below a certain threshold. As described above, each time the multipath group ends, the number of multipath groups G is increased (G + 1). Third, we store the start and end positions of each group, and then calculate the length of that group. Fourthly, while performing the above procedure, the group detector 133 finally performs the number of multipath groups (G), the length of the path delay (T _D ) of each group, and the length between each group (T _G1 , T _G2). , T _G3 , ...)

The pilot pattern selector 135 then determines the number of multipath groups G and the length of path delay T _D between the groups representing the total delay spread, the length of each group T _G1 , T _G2 , An appropriate pilot pattern is selected using T _G3 ..., And a pilot index corresponding to the selected pilot pattern is determined. In this case, the pilot pattern selector 135 may include an internal memory that stores pilot patterns having a plurality of sampling rates, and the memory may store pilot patterns by matching corresponding pilot indices. Accordingly, the pilot pattern selector 135 selects and outputs the index of the pilot pattern having the lowest sampling rate by matching the results output from the group detector 133 with the pilot patterns stored therein.

As shown in FIG. 5, in most single frequency network (SFN) channels, an interval having actual meaningful power among total delay spread T _D is very small. This is a characteristic of a general broadcasting system, and is similar to that of a mobile terminal which performs a mobile communication function. Therefore, even if the sampling rate is lower than the rate satisfying the Nyquist condition, an appropriate sampling technique (eg, undersampling) can be used to obtain a channel estimate of the received signal without distortion. If undersampling is not used, the lowest sampling rate that satisfies the Nyquist condition can be used to estimate the distortion-free channel with minimal pilot transmission.

The transmitter may make multiple pilot patterns, each of which may have a different sampling rate. In this case, a low sampling rate is good if possible, but aliasing may occur if the sampling rate is too low. Accordingly, the pilot pattern selector 135 selects and outputs a pattern index corresponding to the lowest sampling rate among the pilot pilot patterns.

In this manner, the pilot position controller 130 determines the pattern index of the pilot pattern having the lowest sampling rate by using the CIR output from the CIR estimator 110, and the pattern index is transmitted to the pilot generator 150 of the transmitter.

A method of setting a pattern index in the pilot position controller 130 will be described in detail.

7 is a flowchart illustrating a procedure for setting a pattern index in the pilot pattern selector 135 of the pilot position controller 130. Referring to FIG. 8A is a diagram illustrating a case where aliasing occurs when the pattern index 0 is assigned, and FIG. 8B is a diagram illustrating a case where aliasing does not occur when the pattern index 1 is assigned. 9A to 9B illustrate pilot sequences allocated according to pattern indices, and it can be seen that the pilot density is relatively increased as the pattern index increases.

As shown in FIG. 8A and FIG. 8B, it can be seen that aliasing occurs depending on the pattern index. In reality, the condition is checked by a mathematical method. For example, when G = 2 (where G = 2 is expected to be the most common SFN environment), the mathematical condition is expressed by Equation 1 below.

Where T _samp can be the sampling frequency of the pilot pattern to be assigned, T _D is the path delay length between the groups, and can be the total delay spread length here, T _G1 is the length of the path delay of the first group, and T _G2 Is the length of the path delay of the second group. That is, if the pilot index is sorted by the sampling frequency, the pilot position controller 130 calculates given parameters and outputs the first pattern index without aliasing as information for allocating the pilot.

The pilot pattern selector 130 according to the embodiment of the present invention has various pilot patterns as shown in FIGS. 9A to 9C as described above, and these pilot patterns are set to have different sampling frequencies, respectively. Set the index. In addition, the pilot patterns and the index are preferably provided with the same pilot generator 150 on the transmitting side. Therefore, when determining the pilot pattern, the pilot pattern selector 130 of the pilot position controller 130 analyzes the path information generated by the group selector 133 to determine a pattern index of the pilot pattern corresponding to the corresponding path condition.

Referring to FIG. 7, first, in step 411, the number of groups G of the multipaths is checked, and a pattern index is determined while performing steps 413 to 417 according to the identified G. First, when G = 2, the pilot pattern selector 135 increases the pattern index in step 413, updates the pilot sampling frequency according to the pattern index change in step 415, and then, in step 417, the condition as shown in Equation 1 above. Check if it satisfies. If the equation condition is not satisfied, the process returns to step 413 to increase the pattern index and repeats the above operation. If the equation condition is satisfied, the pattern index is determined. In addition, if G = 3 or more, the equations corresponding to the corresponding G value are provided, and in step 421, the pattern index is determined using the same procedure as that for the G = 2.

Third, the pilot generator 150 generates a pilot with a pattern set by the pattern index of the pilot pattern allocated by the pilot position controller 130. 10A and 10B are diagrams showing the configuration of the pilot generator 150. FIG.

The pilot location information generator 153 generates location information for inserting a pilot sequence according to the pilot index output from the pilot location controller 130. Then, the pilot selector 155 generates a pilot sequence corresponding to the pattern index according to the pilot position information. The pilot selector 155 may generate a sequence mapping table 163 for storing pilot sequences and an address generator 161 for generating an address of the sequence mapping table corresponding to the pattern index, as shown in FIG. 7B. It can be configured as. Accordingly, the pilot selector 155 selects and outputs a pilot sequence according to the pattern index. In this case, the selected pilot sequence is sampled at a sampling frequency having an appropriate pilot density by the CIR of the receiver, and the pilot sequence is multiplexed with data at the transmitter and transmitted.

Fourth, the channel estimator 170 of the receiver looks at the procedure of receiving and estimating a signal transmitted by adjusting the pilot density as described above. 11 is a diagram illustrating a configuration of a channel estimator 170 according to an embodiment of the present invention. 12A through 12D are diagrams for describing a channel estimation procedure according to a pilot signal received by the channel estimator 170.

As described above, the transmitter generates and transmits a pilot signal adjusted to an optimal density by the receiver. The receiver must then estimate the channel accordingly. In this case, when the pilot signal sampled as described above is obtained, a shifted version value different from the channel estimation value actually obtained is obtained. That is, the original channel signal as shown in FIG. 12A further includes images copied by adjusting the sampling frequency, and also appears as shown in FIG. 12B in the form of shifted signals. For example, using N / 3 point pilots, three signals as shown in FIG. 12B are generated. Therefore, when estimating a channel using a pilot signal whose sampling rate is adjusted, the channel estimator 170 selects one signal as shown in FIG. 12 from m signals, and as shown in FIG. 12C in the selected signal as shown in FIG. Unnecessary images are removed, and shifted signals from the signal as shown in FIG. 12C should be shifted to their original positions as shown in FIG. 12D. That is, by adjusting the pilot density, unlike the desired signal as shown in FIG. 12A, an unwanted image is included as shown in FIG. 12B to obtain a shifted signal. Therefore, the channel estimator 170 removes the image included in the signal as shown in FIG. 12B as shown in FIG. 12C, shifts to the original signal position as shown in FIG. 12D, generates a desired signal, and estimates a channel using the same. The channel estimator 170 according to an embodiment of the present invention may further include a configuration of removing an image generated by adjusting a sampling frequency during channel estimation and shifting a signal remaining after the image removal to its original position. It can be configured as shown in FIG.

The output of the FFT converter 320 of the receiver is applied to an IDFT interpolator 173 of the channel estimator 170, and the IDFT interpolator 173 performs IDFT interpolation of signals at pilot positions in a received signal converted into a signal in a frequency domain. To convert the signal back into the time domain. In this case, an actual channel response during channel estimation is a signal as shown in FIG. 12A, and signals output from the IDFT interpolator 173 may be signals of a type as shown in FIG. 12B. This is because unwanted image is generated by adjusting the sampling frequency. Also, a plurality of signals as shown in FIG. 12B may be generated. (For example, in the case of an N / 3 point FFT signal, three signals as shown in FIG. 12B may be generated). The image remover 175 may include the number of multipath groups G output from the group detector 133 of the pilot position controller 130, the length of path delays T _D of each group, and the lengths T _G1,. T _G2 , T _G3 , ...) is input, and one of the plurality of signals having the structure as shown in FIG. 12B is selected, and unnecessary images are removed from the signal as shown in FIG. Generate a signal. Then, the delay shifter 177 is the number of multipath groups G output from the pilot position controller 130, the length of the path delay of each group (T _D ), and the length between each group (T _G1 , T _G2 , T). _G3 , ...) and the pattern index, and after confirming the sampling frequency from the pattern index, confirms the shifted position and shifts it to the original signal position as shown in FIG. 12D is then converted into a signal having a frequency component by the DFT converter 179 and applied to the equalizer 340 as a channel estimation signal.

As described above, the channel estimator 170 removes an image generated by the image removal unit 175 by adjusting the pilot density during channel estimation, and the delay shifter 177 shifts the shifted signal back to the original signal position by adjusting the pilot density. To the desired signal shape. Therefore, the channel estimator 170 corrects the image and shift characteristics caused by the adjustment of the pilot density, thereby accurately performing channel estimation of the received signal.

13 is a flowchart illustrating a pilot allocation procedure of an OFDM transceiver according to an embodiment of the present invention.

Referring to FIG. 13, the transmitter performs an initialization function in step 511 during initialization, and allocates an initial pilot pattern. Thereafter, when data transmission occurs, the transmitter transmits an OFDM transmission function by multiplexing the transmission data to the allocated pilot pattern in step 513. When the data transmission ends, the transmitter performs an idle mode in step 515. Then, when the pilot allocation information for allocating the pilot is output from the receiving side, the transmitting side receives in step 517 and then, in step 519 controls the pilot generator to allocate a pilot sequence according to the received pilot allocation information. After the transmission mode is reached, the transmitter transmits OFDM by multiplexing the allocated pilot sequence to the data in step 513. This operation is repeated.

When the receiver receives the signal, the receiver processes the received signal in step 551. In step 553, the receiver measures the CIR of the received signal to allocate the pilot according to the channel state. In this case, the method of measuring the CIR of the received signal may be performed by the method as shown in FIG. 3. At this time, the CIR generates delay values of the first type CIR, the second type CIR, and the two types of CIRs, and measures the CIR of the received signal using the CIRs. The CIR estimation method includes estimating a CIR of a first type and calculating a first delay estimation distance of the estimated first type CIR, and estimating a second delay of the second type and estimating a second delay estimated distance of the second type. And calculating the CIR of the received signal by pattern matching the CIRs of the first and second forms and the first and second delay estimation distances.

Here, the process of estimating the CIR of the first type squares N point FFT signals and IFFT transforms the squared signal to estimate the CIR of the first type. And determining multipaths having a predetermined threshold value or more among the vector signals of the CIR of the first type, checking the number and location of the determined multipaths, and the distance D between the first path and the last path of the multipaths. Is obtained and determined as the delay distance D of the first type CIR. The process of estimating the CIR of the second form selects the N / m point FFT signals in which the pilot is located, and IFFT transforms these signals to estimate the CIR of the second form. Then, for each multipath obtained in the second type CIR, it is assumed that each multipath is the first multipath, each multipath makes hypothesis for the first path, and for each hypothesis, the first path and Find the distance of the last path as you cycle. The pattern matching process finally finds a hypothesis closest to D by pattern matching the first estimated delay distance and the second estimated delay distance. When the hypothesis closest to the D is determined, the first path and the last path are determined, and thus the final CIR is estimated by pattern matching the second shape CIR at the multipath location of the first shape CIR.

In step 555, the receiver performs a group information detection process for appropriately assigning a pilot sampling frequency to the pilot using the CIR estimation value. In the group information detection process, the number of multipath groups, the path delay length of each group, and the length between each group are obtained from the CIR. First, the center of the CIR response vector is adjusted to the origin (delay in the time domain and phase rotation in the frequency domain). In addition, the power of each multipath is calculated, and if it exceeds a certain threshold value, it is determined that the multipath group starts and if it falls below a certain threshold value, it is determined that the multipath group ends, and the number of multipath groups is increased ( G + 1). We also store the start and end positions in each group and calculate the length. The group detection process is performed by repeating the above process, the number of multipath groups G, the path delay length T _D of each group, and the lengths T _G1 , T _G2 , T _G3 , .. Obtain

In step 555, the receiving side pilots to match the channel characteristics by using the number G of the multipath groups, the path delay length T _D of each group, and the lengths T _G1 , T _G2 , T _G3 ,. A pilot pattern selection process for generating pilot allocation information for allocating pilots by adjusting a frequency is performed. In general, in the SFN channel environment, the section having the actual meaningful power among the path delay lengths T _D of each group, which is the total delay spread section, is very small. In this case, even if the sampling rate is lower than the rate satisfying the Nyquist condition, the channel estimation can be performed without error. Therefore, various pilot patterns are made, and these pilot patterns are set to have different sampling rates, and the number G of the multipath groups, the path delay length T _D of each group, and the lengths T _G1 , T _G2 , Each condition is set according to the number G of the path groups so that an appropriate sampling frequency T _samp can be set in the T _D section according to T _{G3 ,.} If the pattern index for determining a pilot pattern is sorted by the sampling frequency T _samp , the pattern according to the parameters G, T _D , T _G1 , T _G2 , T _G3 ,.. You can set the index.

Thereafter, the receiving side transmits the pattern index determined as described above to the transmitting side in step 559. Then, the transmitting side receives the pattern index in step 517 as described above, and in step 519 controls the pilot generator of the transmitting side to allocate a pilot according to the pattern index. Thereafter, in the transmission mode, the transmitting side multiplexes and transmits the allocated pilot to the data to be transmitted in step 513. Accordingly, the OFDM signal transmitted from the transmitting side includes pilots allocated according to the channel environment of the receiving side.

In FIG. 13, the group detection process and the pilot pattern selection process for controlling the pilot position are shown at the receiving side, but the same result can be obtained even if the process is performed at the transmitting side. That is, the steps 555 and 557 are the same result even if performed between steps 517 and 519 of the transmitting side. In this case, the receiving side transmits the CIR value estimated in step 553 as pilot allocation information to the transmitting side in step 555. After the transmitter receives this in step 517, the transmitter selects a pilot index while performing group detection and pilot pattern selection in steps 555 and 557, and selects a new pilot in step 519 using the selected pilot index. Can be assigned.

Although not shown in FIG. 13, the signal received in step 551 is processed while performing an FFT process, channel estimation, and equalization process. At this time, since the received pilot signal is a signal allocated by the sampling frequency adjusted by the above-described bar and the receiving CIR, the received pilot signal is an image shifted signal. Therefore, during channel estimation, the receiving side preferably removes an image included in the pilot signal and restores the shifted pilot signal to generate a channel estimation signal.

The pilot allocation method according to an embodiment of the present invention can be used in a portable terminal such as a cellular phone, a broadcast receiver, or the like using an OFDM transceiver. In the following description, it will be assumed that the mobile terminal is a mobile phone. In this case, the above-mentioned receiving end (receiving side, receiver) may be a receiver of a mobile terminal, and the transmitting end (transmitting side, transmitter) may be a transmitter of a base station.

In this case, the portable terminal estimates the CIR of the reception channel to determine a necessary pilot allocation, and then transfers the determined pilot allocation information to the base station, and the base station generates a pilot symbol based on the pilot allocation information transmitted from the terminal. Can be sent. Secondly, after estimating the CIR of the reception channel, the mobile terminal transmits the estimated CIR information to a base station, and the base station determines a pilot allocation from the CRI estimation information of the received terminal, and determines the determined pilot allocation information. According to the pilot symbol can be generated and transmitted.

FIG. 14 is a diagram showing the configuration of a base station and a mobile terminal showing the former pilot allocation method, and FIG. 15 is a diagram showing a configuration of the base station and the mobile terminal showing the latter pilot allocation method.

Referring to FIG. 14, first, an RF receiver 310 of a portable terminal converts a received radio signal into a signal of a baseband received, and the FFT converter 320 converts data and pilot signals of the received time component into frequency components. To convert. A channel impulse response estimator 110 estimates the received CIR by estimating the FFT transform signal. Here, the CIR estimator 110 estimates the CIR estimation signal to estimate the pilot density substantially required in the channel environment of the mobile terminal. Create The CIR estimator 110 may have the configuration as shown in FIG. 3. As described above, in the embodiment of the present invention, the CIR of the first type is obtained from the N point FFT signal, and the N / m point FFT signal in which the actual pilot is located. The CIR of the second form is obtained from The CIRs of the first and second forms are pattern-matched using these delay values to obtain a CIR of a desired form. Here, CIR can also be calculated | required using either CIR of a said 1st form, or CIR of a 2nd form. In the embodiment of the present invention, it is assumed that a method of obtaining a final CIR by obtaining a CIR of a first type and a CIR of a second type, pattern matching of the CIR of a second type, and the like, is used to obtain an accurate CIR.

The pilot location controller 130 generates pilot allocation information for allocating an appropriate pilot using the CIR output from the CIR estimator 110. In the embodiment of the present invention, the pilot allocation information may be a pattern index for selecting a desired pilot pattern among various pilot patterns included in the transmitter, that is, the base station. The pilot position controller 130 may have a configuration as shown in FIG. 6. In this case, the pilot position controller 130 may determine the number of multipath groups G, the path delay length T _D of each group, and the length T between the groups. _And a group detector 133 for detecting _G1 , T _G2 , T _G3 ,..., And a pilot pattern selector 135 for selecting a pattern index for sampling a pilot frequency from the output of the group detector 133. The pattern index is information for allocating a pilot pattern that can be estimated for a section having a really significant power among the entire spread region, and the pilot position controller 133 performs a condition according to G while performing the procedure as shown in FIG. 7. A pattern index having a satisfactory sampling frequency is selected. In this case, the sampling rate of the pilot pattern corresponding to the selected pattern index may be lower than the sampling rate that satisfies the Nyquist condition (ie, may be undersampled), and in this case, the mobile terminal may perform channel estimation without distortion. . At this time, the base station has a plurality of pilot patterns each having a different sampling rate, these pilot patterns have a structure corresponding to the pattern index.

The pattern index output from the pilot position controller 130 is transmitted to the pilot generator 150 of the base station through the transmission path of the mobile terminal. Referring to the transmission path of the portable terminal, the encoder (tx encoder) 391 codes data to be transmitted from the portable terminal. The multiplexer 393 multiplexes the coded transmission data and the pattern index output from the pilot position controller 130 to the corresponding transmission channel. Here, the channel of the mobile terminal through which the pattern index is transmitted may be a channel for transmitting control data. The modulator 395 OFDM modulates the transmission data output from the multiplexer 393. The RF transmitter 397 increases the modulated transmission data to a frequency of the transmission RF signal and outputs the modulated transmission data.

In addition, the channel estimator 170 predicts channel distortion from the FFT-converted pilot signal and generates a channel estimating signal for restoring the signal shape at the time of transmission. In this case, the channel estimator 170 receives a pilot signal whose pilot density is adjusted by adjusting a pilot frequency at the base station. Therefore, the channel estimator 170 removes a pilot image generated by adjusting the pilot density and places the pilot signal from which the image is removed. It may further comprise a function for shifting. The channel estimator 170 may have a configuration as shown in FIG. 11. In this case, the channel estimator calculates the number G of the multipath groups detected by the pilot position controller 130, the path delay length T _D of each group, and the lengths T _G1 , T _G2 , T _G3 , .. and wave pattern indexes between the groups. Removes an unwanted image included in the received signal, and shifts the remaining signal to an appropriate position after removing the image.

An equalizer 340 equalizes the demultiplexed data symbols by the channel estimation signal. Here, the equalizer 340 may use a one-tap equalizer. A demapper 350 demaps the data symbol into its original data form, a channel decoder 360 decodes the data into original data, and a data processor 370 processes the channel decoded received data stream. do.

The base station receives the signal of the mobile terminal transmitted as described above through the reception path. Referring to the reception path of the base station, the RF receiver 291 converts the received signal into a baseband signal, the modulator 293 OFDM demodulates the signal output from the RF receiver 291, and the decoder 295 decodes the demodulated signal. . In this case, the signal decoded by the decoder 295 may include a pattern index transmitted from the mobile terminal, and the pattern index is transmitted to the pilot generator 150.

The pilot generator generates a pilot signal for accurate channel estimation at the receiving side during OFDM transmission, where the pilot signal may be generated by a pattern index transmitted from the mobile terminal according to an embodiment of the present invention. The pattern generator 150 according to the embodiment of the present invention may have the configuration as shown in FIG. 10A, and the pilot selector 153 of FIG. 10A may have the configuration as shown in FIG. 10B. The pilot selector 155 of the pilot generator 150 includes a sequence mapping table 163 having a pilot location sequence in an internal memory, and the address generator 165 converts the received pattern index into an address of the sequence mapping table. Accordingly, the pilot generation is activated at the position set by the pilot location information generator 153 of the pilot generator 150, and the pilot selector 155 selects a pilot location sequence having a sampling frequency corresponding to the pattern index at the pilot location information location, thereby multiplying. Pass on firearm 240.

The Tx stream generator 210 performs a function of generating data to be transmitted. A channel coder 220 performs channel coding on the transmission data stream to perform error correction encoding, and a mapper 230 converts the channel coded data into data symbols. Here, the mapper 230 may use a quadrature amplitude modulation (QAM) mapper. Since the transmitter must transmit pilot symbols in addition to the data symbols during the OFDM transmission, the pilot generator 150 generates pilot symbols to be transmitted with the data symbols. In an embodiment of the present invention, the pilot generator 150 may generate a pilot symbol that is variably adjusted by pilot allocation by a receiver. The multiplexer 240 multiplexes the pilot symbols generated by the pilot generator 150 and the data symbols generated by the mapper 230, and the inverse fast fourier tramsform part (IFFT) 250 performs time domain data and pilot symbols in the multiplexed frequency domain. After converting the signal into a transmission band, the RF transmitter 260 filters the signal into a transmission band and then increases the frequency of the signal to a wireless signal of the transmission band.

Referring to FIG. 15, the CIR estimator 110 is located in a mobile terminal, and the pilot position controller 130 is located in a base station. Accordingly, the CIR estimator 110 of the portable terminal estimates the CIR of the received signal, and the CIR is transmitted through the transmission path of the portable terminal. In addition, the pilot position controller 130 of the base station analyzes the CIR received through the reception path of the base station to determine a pilot pattern index having a sampling rate for channel estimation appropriately for the mobile terminal. In this case, the configuration and operation of the CIR estimator 110 and the pilot position controller 130 may be identical to those of the CIR estimator 110 and the pilot position controller 130 of FIG. 14. Accordingly, FIG. 15 estimates the CIR of the signal received by the mobile terminal and informs the base station. The base station analyzes the received CIR of the mobile terminal and allocates a pilot such that the channel estimation can be performed without error in the mobile terminal. have. In this case, the base station generates information generated by the pilot position controller 130 (number of multipath groups, path delay length T _D of each group, and lengths T _G1 , T _G2 , T _G3 , .. and pattern indexes between groups). Is transmitted to the mobile terminal, and the channel estimator 170 can use this to estimate the channel. In this case, the base station can allocate the pilot bandwidth appropriately to allocate the transmission efficiency of the data.

In addition, the group detector 133 of the pilot position controller 130 may be located in the mobile terminal and the pilot pattern selector 135 may be located in the base station. In this case, the information generated by the group detector 133 (number of multipath groups, path delay length T _D of each group, and length T _G1 , T _G2 , T _G3 ,. The channel index may be transmitted, and the channel index may be received by the base station.

1 is a diagram illustrating a structure of an OFDM transceiver according to an embodiment of the present invention.

2 is a diagram illustrating an example in which 1/3 of N point FFT signals is a pilot;

FIG. 3 is a diagram showing the configuration of a CIR estimator 110 that generates a CIR of a first form and a CIR of a second form, and uses these to generate a desired CIR.

4A is a diagram showing an original CIR, FIG. 4B is a diagram showing an output CIR of a first form, and FIG. 4C is a diagram showing an output CIR of a second form.

5 is a diagram illustrating a CIR output from a channel estimator.

6 is a diagram showing the configuration of the pilot position controller 130. FIG.

7 is a flowchart illustrating a procedure for setting a pattern index in the pilot pattern selector 135 of the pilot position controller 130. FIG.

8A is a diagram showing a case where aliasing occurs when the pattern index 0 is assigned, and FIG. 8B is a diagram showing a case where aliasing does not occur when the pattern index 1 is assigned.

9A-9B illustrate pilot sequences allocated according to a pattern index.

10A and 10B show the configuration of the pilot generator 150.

11 illustrates a configuration of a channel estimator 170 according to an embodiment of the present invention.

12A and 12D are diagrams for describing a channel estimation procedure according to a pilot signal received by the channel estimator 170.

13 is a flowchart illustrating a pilot allocation procedure of an OFDM transceiver according to an embodiment of the present invention.

14 and 15 illustrate configurations of a base station and a mobile terminal for allocating pilots according to an embodiment of the present invention.

Claims (29)

In the orthogonal frequency multiple access communication device, A channel impulse response estimator for estimating a channel impulse response signal from the received channel signal; After detecting the group information such as the number of multipath groups, the path delay between each group, and the length between the groups in the estimated channel impulse response signal, the pilot allocation information is applied by applying the detected group information to the condition of the number of path groups. Orthogonal frequency multiple access communication apparatus comprising a pilot position controller for determining. The method of claim 1, wherein the pilot position controller, A group information detector for detecting group information of the number of multipath groups, the path delay length between each group, and the length between groups from the channel impulse response; And a pilot pattern selector configured to select pilot allocation information for allocating a pilot pattern of a lowest sampling frequency satisfying a condition of the number of multipath groups using the group information. . The method of claim 2, wherein the pilot pattern selector includes indexes of the sequence mapping table sorted by a pilot sampling frequency, and outputs the pattern index of the sequence mapping table corresponding to the selected sampling frequency as the pilot assignment information. Orthogonal frequency multiple access communication device. The method of claim 3, wherein the group information detector, The center of the channel impulse response signal is set to the origin, the number of path groups is determined by comparing the channel impulse response signal with a threshold value, the delay length of each path group is calculated from the start and end positions in each group, and the path And orthogonal frequency multiple access communication device for calculating delay lengths between groups. The method of claim 4, wherein the channel pattern selector, And the number of path groups is G = 2, and the pilot allocation information having the pilot pattern having the lowest sampling rate is selected under the condition of Equation 2 below.

Where T _samp is the sampling frequency of the pilot pattern to be assigned, T _D is the path delay length between the groups, T _G1 is the length of the path delay in the first group, and T _G2 is the length of the path delay in the second group. The method of claim 2, wherein the channel impulse response estimator, A first channel impulse response estimator for estimating a channel impulse response signal of a first type in the entire FFT-converted signal; A second channel impulse response estimator for calculating a second type of channel impulse response signal at a pilot position of the FFT transformed signal; And a pattern matcher for matching a pattern of first and second types of channel impulse response signals to estimate a final channel impulse response. The method of claim 6, The first channel impulse response estimator comprises: a squarer for squaring the entire FFT-converted signal, an IFFT transformer for generating a channel impulse response signal of a first type for IFFT transforming the squarer output, and the channel of the first type It consists of a first delay estimator for estimating the first delay distance from the first path to the last path of the impulse response signal, A second channel impulse response estimator extracts and descrambles the FFT signal of the pilot position from the entire FFT-converted signal; And a second delay distance, which is the distances to the last path, assuming each multipath of all multipaths of the channel impulse response of the second type as the first multipath, and assuming that each multipath is the first path. It consists of a second delay estimator, And the pattern matcher determines a final channel impulse response by pattern matching the channel impulse responses of the first and second types and the first and second delay distances. The method of claim 6, And a pilot generator configured to receive the pilot assignment information, generate a pilot sequence according to the pilot assignment information, and multiplex the transmission data to transmit data. The method of claim 8, wherein the pilot generator, And a sequence mapping table for storing the pilot patterns sorted by the sampling frequency, and generating a pilot sequence of the sequence mapping table corresponding to the received pilot allocation information. The method of claim 8, And a channel estimator for generating a channel estimating signal after restoring the change according to the pilot density adjustment using the group information and the pilot assignment information, and transmitting the received signal to an equalizer. Connection communication device. The method of claim 10, wherein the channel estimator, An IDFT interpolator for performing IDFT interpolation of the FFT conversion signal; An image removal unit for removing an image included in an output of the DFT interpolator by the group information; A delay shifter for shifting the output of the image removing unit by the group information and a pilot sampling frequency; And a DFT converter configured to DFT convert the output of the delay shifter. In the orthogonal frequency multiplexing device of a mobile terminal, A first channel impulse response estimator for estimating a channel impulse response signal of a first type from the received total signal, a second channel impulse response estimator for estimating a channel impulse response signal of a second type at a pilot position of the received signal; A channel impulse response estimator comprising a pattern matcher for matching the patterns of the first and second types of channel impulse responses to estimate a final channel impulse response; A group information detector for detecting group information of the number of multipath groups, the path delay length between groups, and the length of the groups from the channel impulse response, and applying the condition to the conditions of the number of the multipath groups corresponding to the group information. Orthogonal frequency multiple access communication device comprising a pilot controller consisting of a pilot pattern selector for selecting pilot allocation information for allocating a pilot pattern of the lowest sampling frequency that satisfies The method of claim 12, wherein the received signal is transmitted after a pilot generator of a base station having a sequence mapping table storing pilot patterns sorted by a sampling frequency generates a pilot sequence of the sequence mapping table corresponding to the pilot assignment information. And the pilot sequence is multiplexed to data and transmitted to a mobile terminal. The method of claim 13, And a channel estimator for generating a channel estimation signal from the received signal and transmitting the channel estimation signal to an equalizer, wherein the channel estimator removes an image included in the received signal by using the group information and pilot assignment information. And a delay shifter for shifting the position of the image-removed signal. In the orthogonal frequency multiple access communication device, Mobile terminal, A first channel impulse response estimator for estimating a channel impulse response signal of a first type from the entire FFT-converted signal, and a second channel impulse response estimator for calculating a channel impulse response signal of a second type at a pilot position of the FFT-converted signal And a channel impulse response estimator comprising a pattern matcher for matching the patterns of the first and second type channel impulse responses to estimate the final channel impulse response. The base station, A group information detector for detecting group information of the number of multipath groups, the path delay length between groups, and the length of the groups from the channel impulse response; and using the group information, the condition of the number G of the multipath groups is determined. And a pilot controller comprising a pilot pattern selector for selecting pilot allocation information for allocating a pilot pattern having the lowest sampling rate that satisfies. In the orthogonal frequency multiple access communication device, Mobile terminal, A first channel impulse response estimator for estimating a channel impulse response signal of a first type from the entire FFT transformed signal, and a second channel impulse response estimator estimating a channel impulse response signal of a second type at a pilot position of the FFT transformed signal A channel impulse response estimator comprising a pattern matcher for matching the patterns of the first and second types of channel impulse responses to estimate a final channel impulse response; And a group information detector for calculating group information of the number of multipath groups, the path delay length between each group, and the length between groups from the channel impulse response. The base station Orthogonal frequency multiple access, comprising: pilot pattern selector configured to select pilot allocation information for allocating a pilot pattern of the lowest sampling rate satisfying the condition G of the multipath group using the group information; Communication device. In the orthogonal frequency multiple access communication method, Estimating a channel impulse response signal from the received channel signal; After detecting the group information such as the number of multipath groups, the path delay between each group, and the length between the groups in the estimated channel impulse response signal, the pilot allocation information for adjusting the sampling frequency is determined using the detected group information. Orthogonal frequency multiple access communication method characterized in that consisting of a process. The method of claim 17, wherein the step of generating pilot assignment information from the channel impulse response, Detecting group information of the number of multipath groups, the path delay length between each group, and the length between groups from the channel impulse response; And analyzing the group information to determine pilot allocation information for allocating a pilot pattern of the lowest sampling frequency that satisfies the condition of the number of the corresponding multipath groups. 19. The method of claim 18, wherein the pilot assignment information is a pattern index of a sequence mapping table sorted by a pilot sampling frequency. The method of claim 18, wherein the detecting of the group information comprises: Adjusting the center of the channel impulse response signal to an origin; The number of path groups is determined by comparing the channel impulse response with a threshold value, the delay length of each path group is calculated from the start and end positions in each group, and the delay length between the path groups is calculated. Orthogonal frequency multiple access communication method. The method of claim 20, wherein the determining of the pilot allocation information comprises: And if the number of path groups is G = 2, the pilot allocation information having the pilot pattern having the lowest sampling rate is selected under the condition of Equation 3 below.

Where T _samp is the sampling frequency of the pilot pattern to be assigned, T _D is the path delay length between the groups, T _G1 is the length of the path delay in the first group, and T _G2 is the length of the path delay in the second group. 19. The method of claim 18, wherein estimating the channel impulse response, Estimating the channel impulse response of the first type in the entire FFT-converted signal of the received signal; Estimating the channel impulse response of the second type at the pilot position of the FFT transformed signal of the received signal, And matching the patterns of the first and second channel impulse responses to estimate a final channel impulse response. The method of claim 22, The channel impulse response estimation process of the first form Squaring the entire FFT-converted signal, generating a first type channel impulse response for IFFT transforming the squared signal, and a first path to the last path of the first type channel impulse response; 1 consists of estimating the delay distance, In the second form of channel impulse response estimation process, Extracting and descrambling the FFT signal of the pilot position from the entire FFT-converted signal, IFFT converting the descrambled signal to generate a channel impulse response of a second type, and channel impulse of the second type Assuming that each multipath of all multipaths in the response is the first multipath, each multipath is assumed to be the first path, and the second delay distance, which is the distances to the last path, is estimated. The process of generating the final channel impulse response, And the final channel impulse response is determined by matching the channel impulse responses of the first and second types with the patterns of the first and second delay distances. The orthogonal frequency multiple access communication method according to claim 22, wherein the received signal is a signal from which a transmitter selects a pilot sequence according to the pilot assignment information from a sequence mapping table and multiplexes the transmission data. The method of claim 24, Generating a channel estimation signal from the received signal, and equalizing the received signal using the channel estimation signal, The process of generating the channel estimation signal, IDFT interpolating the received signal, removing the image included in the IDFT interpolated signal using the group information, and shifting the signal from which the image is removed to the original position using group information and pilot assignment information. The orthogonal frequency multiple access communication method, characterized in that consisting of a process. In the orthogonal frequency connection communication method of a mobile terminal, Estimating the channel impulse response of the first form from the FFT-converted total signal of the received signal, estimating the channel impulse response of the second form from the pilot position signal in the FFT transformed signal of the received signal, and Estimating the final channel impulse response by matching a pattern of channel impulse responses; Detecting group information of the number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response; And analyzing the group information to determine pilot allocation information for allocating a pilot pattern of the lowest sampling frequency that satisfies the condition of the number of the corresponding multipath groups. 26. The method of claim 25, wherein the received signal is a signal generated by a base station to generate a pilot sequence of a sequence mapping table corresponding to pilot allocation information received through a reception path, and multiplexes it to transmitted data and transmits the result to a mobile terminal. Orthogonal frequency multiple access communication method. 27. The portable terminal of claim 26, wherein the mobile terminal Generating a channel estimation signal from the received signal, and equalizing the received signal using the channel estimation signal, The process of generating the channel estimation signal, IDFT interpolating the received signal, removing the image included in the IDFT interpolated signal using the group information, and shifting the signal from which the image is removed to the original position using group information and pilot assignment information. The orthogonal frequency multiple access communication method, characterized in that consisting of a process. Mobile terminal, Estimating the channel impulse response of the first type from the entire FFT transformed signal, estimating the channel impulse response of the second type from the signal of the FFT transformed pilot position, and extracting the pattern of the channel impulse responses of the first and second type. Estimating the final channel impulse response by matching; The base station, Detecting group information of the number of multipath groups, a path delay length between groups, and a length between groups from the channel impulse response; Selecting pilot allocation information for allocating a pilot pattern of the lowest sampling rate satisfying the condition by applying the group information to the number G of the corresponding multipath groups; And generating a pilot sequence of the sequence mapping table corresponding to the received pilot assignment information, the sequence mapping table storing the pilot patterns sorted by the sampling frequency. The mobile terminal transmits the channel impulse response through a transmission path, and the base station multiplexes the group information and the pilot sequence generated by the channel impulse response to transmission data and transmits the result to the mobile terminal. Orthogonal frequency multiple access communication method.

Images