KR101021306B1 - A demodulator system for supporting MIMO and OFDM transsmission and control method thereof - Google Patents

Abstract

The present invention relates to a terminal demodulation system that supports MIMO and OFDM transmission methods and a control method thereof. The present invention relates to a multiplex that extracts valid data through guard interval elimination, fast Fourier transform, and guard band elimination. A carrier demodulator extracts a reference signal from the extracted valid data to synchronize valid data, calculates and outputs a channel estimate based on the antenna combination through frequency and linear interpolation, and propagates a signal from the synchronized data based on the channel estimate. By providing a system and a control method including a frame deformatter that extracts channels for a path and outputs them sequentially, there is no need for additional hardware resources because no additional internal modules are required as the number of receive antennas increases. Effect foot It is.

In addition, according to the terminal demodulation system supporting the MIMO and OFDM transmission scheme and the control method according to the present invention, the interference between the reference signal (RS) for channel estimation transmitted from each antenna is minimized, the channel estimate is a frequency And to be continuous in time to ensure the performance of channel estimation.

OFDM, MIMO, Antenna, Frame, Channel, Estimation, Demodulation

Description

A demodulator system for supporting MIMO and OFDM transsmission and control method

The present invention relates to a terminal demodulation system, and more particularly, to a system for receiving a large amount of data transmitted by a transmitter of a wireless mobile communication system in a MIMO and OFDM transmission scheme and demodulating according to a transmission scheme and a control method thereof.

The present invention is derived from a study conducted as a part of the IT new growth engine core technology project of the Ministry of Knowledge Economy and the Ministry of Information and Communication Research and Development. [Task management number: 2006-S-001-03, Assignment name: Application for 4G mobile communication Wireless access and transmission technology development].

In general, a baseband modem, which is a component of a terminal of an OFDM mobile communication system, includes a receiver for receiving data from a base station and a transmitter for transmitting data of the terminal to a base station.

The receiver includes a synchronizer for finding synchronization of a received signal, a demodulator for restoring received data, a decoder for decoding channel coding, and the like. The dual demodulator processes the reverse order of modulation in the transmitter.In OFDM transmitters, after performing inverse fast Fourier transform (IFFT) and then inserting a guard interval, the receiver first removes the guard interval. FFT is performed on the removed data of a certain length. Thereafter, the FFT signal is divided into a control channel and a data channel, and the original signal is determined by identifying a channel between the transmitter and the receiver through a demodulation reference signal (RS) generated using a known sequence. You will be taken to the next step.

On the other hand, the initial OFDM transmission and reception apparatus was a single input single output (SISO) type using one transmission antenna and one reception antenna, but recently, 2 × 2 multiple input / output (MIMO), It is evolving into the form of 4x4 MIMO and 8x8 MIMO. If the number of receiving antennas is increased, the demodulator should increase the internal module that undergoes the demodulation procedure described above, in order to increase the transmission rate in proportion to the increase in the number of transmit and receive antennas.

However, as the number of antennas increases, the number of internal modules increases, so the cost of internal hardware resources must be increased, and signal distortion occurs due to the increased interference between antennas, so an algorithm for removing the interference is required. This algorithm has the problem of requiring more hardware resources as a result.

SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional problems as described above, and the channel for the signal propagation path by dividing the channel by the correct extraction order based on the reference signal and the channel estimate in the data received from the plurality of receiving antennas It is to provide an apparatus and method for determining.

In addition, another object of the present invention is to minimize the interference between the reference signal (RS) for channel estimation transmitted from each antenna, and to ensure the performance of channel estimation by ensuring that the channel estimate is continuous in frequency and time To provide.

In order to achieve the above object, the terminal demodulation system supporting the MIMO and OFDM transmission scheme according to the present invention, the effective data through the guard interval removal, fast Fourier transform and guard band removal of the data signal input from a plurality of antennas A multi-carrier demodulator for extracting a signal, synchronizing valid data by extracting a reference signal from the extracted valid data, and calculating and outputting a channel estimate based on an antenna combination through frequency and linear interpolation and synchronized based on the channel estimate And a frame deformatter that sequentially extracts a channel for a signal propagation path from data and sequentially outputs the channel.

In addition, the terminal demodulation system control method supporting the MIMO and OFDM transmission method according to the present invention, the step of extracting the valid data through the guard interval removal, fast Fourier transform and guard band removal of the data signal input from a plurality of antennas, Extracting a reference signal from the extracted valid data and synchronizing the valid data by comparing with a preset reference signal, performing FFT interpolation on a frequency in a section where the reference signal is present, and outputting a channel estimate value; Outputting a channel estimate by performing linear interpolation over time in a period where there is no signal, temporarily storing the synchronized data and the channel estimate so that the reference signals do not overlap, and synchronized data based on the temporarily stored channel estimate Extracts the channel for the signal propagation path It may be made, including the step of outputting the enemy.

As described above, according to the terminal demodulation system and its control method supporting the MIMO and OFDM transmission scheme according to the present invention, since no additional internal module is required according to the increase in the number of receive antennas, the cost for hardware resources is not added. The effect is exerted.

In addition, according to the terminal demodulation system supporting the MIMO and OFDM transmission scheme and the control method according to the present invention, the interference between the reference signal (RS) for channel estimation transmitted from each antenna is minimized, the channel estimate is a frequency And the effect of ensuring the performance of channel estimation by being continuous in time is also obtained.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. In addition, in describing this invention, the same code | symbol is attached | subjected and the repeated description is abbreviate | omitted.

1 is a block diagram schematically illustrating a configuration of a terminal demodulation system supporting a MIMO and OFDM transmission scheme according to an embodiment of the present invention.

As shown in FIG. 1, the terminal demodulation system 100 according to the present invention includes a multi-carrier demodulator 110, a channel estimator 120, and a frame deformatter 130.

The multi-carrier demodulator 110 extracts valid data from data signals input from four antennas (not shown) through guard interval removal, fast Fourier transform, and guard band removal. A guard interval removing unit 111 for removing a guard interval inserted after an inverse fast Fourier transform (IFFT) on the second stage, and outputting the data on the time axis as a data on the frequency axis through a fast Fourier transform The FFT unit 112 includes a guard band removing unit 113 for outputting valid data by removing a guard band from the data of the frequency axis.

The channel estimator 120 extracts a reference signal from the extracted valid data to synchronize valid data, and calculates and outputs a channel estimate based on an antenna combination through frequency and linear interpolation. A reference signal extractor 121 for extracting a signal, a frequency interpolator 122 for outputting a channel estimate by performing an FFT interpolation on a frequency in a section in which the reference signal is present, and a time type in a section in which the reference signal is absent And a linear interpolator 123 for performing interpolation to output a channel estimate.

The frame deformatter 130 extracts and sequentially outputs a channel for a signal propagation path from the synchronized data based on the channel estimate, and includes a PBCH including values related to cell characteristics broadcast to the entire cell. PBCH extractor 131 for extracting a physical broadcast channel), PCFICH extractor 132 for extracting a physical control format indicator channel (PCFICH) for transmitting the number of OFDM symbols, except for time and frequency resources allocated to the PCFICH A PHICH extractor 133 for extracting a PHICH (physical hybrid ARQ indicator channel) disposed at a location, and a PDCCH extractor for extracting a physical downlink control channel (PDCCH) located on a frequency other than the positions occupied by the PCFICH and PHICH. 134) and a PDSCH extraction for extracting a physical downlink shared channel (PDSCH) located at a location without a synchronization signal and a reference signal among the OFDM symbols without the channels; And a unit (135).

In addition, the frame formatter 130 further includes a temporary storage unit 136 for temporarily storing the synchronized data and the channel estimate so that reference signals do not overlap when the respective extracting units 131 to 135 locate the channel. .

Referring to the accompanying drawings, the operation process according to the embodiment of the present invention configured as described above is as follows.

2 is a flowchart illustrating a demodulation process in a terminal demodulation system according to an embodiment of the present invention, FIG. 3 is a diagram showing a reference signal allocation according to the 3GPP LTE standard according to an embodiment of the present invention, and FIG. A linear interpolation factor in a symbol without a reference signal according to an embodiment is shown.

Referring to FIG. 2, first, when a data signal input from four receiving antennas (complex data corresponding to four receiving antennas) is input, the base station modulator removes a guard interval inserted after IFFT when outputting the final signal. In operation S210, valid data is extracted through fast Fourier transform and guard band removal.

For example, if a 20 MHz band is used, since 2,208 or 2,192 data are inputted according to the 20 or 20 guardrail data, 160 or 144 guard intervals can be inserted for 2048 data (data on a subcarrier). Remove the interval so that only 2048 data is left.

The 2048 data from which the guard interval has been removed is subjected to fast Fourier transform to convert 2048 data on the time axis into 2048 data on the frequency axis, and valid data (data on 1200 subcarriers) and guard bands are applied to the converted 2048 data. Since there is a guard band, only valid data is extracted through guard band elimination. In this case, the extracted valid data exist for all four spatially divided reception antennas, and are complex data of 1200 units.

Subsequently, the reference signal RS is extracted from the valid data extracted in step S210, and the valid data is synchronized by comparing with the preset RS (S220).

That is, the reference signal RS is not continuous in terms of frequency and time axis. As shown in FIG. 3, the horizontal axis is a time axis and 14 OFDM symbols constituting one subframe, and indexes representing each of them. 14) (10 subframes together form one radio frame), and the vertical axis represents the frequency axis with one unit representing one subcarrier (in the 3GPP LTE standard, 12 subcarriers are defined as one resource block). If the number of RBs is defined up to 110 RB depending on the system band), ○ denotes RS assigned to antenna 1, □ denotes antenna 2, △ denotes antenna 3, and ☆ denotes antenna. In case 4, the RS of each antenna differs in position on the frequency or time axis. Therefore, since the synchronization of the data output from each antenna does not match, the data is synchronized by comparing with a preset reference signal.

 On the other hand, since the embodiment of the present invention uses four transmit / receive antennas, there may be up to 16 combinations depending on which receiving antenna reference signals are extracted from which receiving antennas, and each combination is not continuous in time and frequency. Therefore, since the channel estimate using the reference signal should be used to calculate the distortion of the physical signal at different time and frequency positions where the reference signal is not located, the present invention provides an interpolation process so that it can be continuous in frequency and time. The process of guessing a point between neighboring data).

That is, in the section in which the reference signal is present, the channel estimate is output by performing FFT interpolation on the frequency (a process of filling a blank on the frequency in FIG. 3) (S230).

For example, as shown in FIG. 3, since only a reference signal for two antennas is included in one time symbol, frequency interpolation may be performed on eight propagation paths, which are a combination of two transmitting antennas and four receiving antennas, in a specific time interval.

When the execution of step S230 is completed, linear interpolation is performed in time to output a channel estimate (S240). If the reference signal is absent, linear interpolation is performed immediately without performing frequency interpolation.

For example, as shown in FIGS. 3 and 4, since antennas 1 and 2 have reference signals only in symbols 1, 5, 8, and 12, 2, 3, 4, 6, 7, 9, 10, 11, 13, and 14 Since the channel values in the symbols are estimated, and the antennas 3 and 4 have reference signals only in symbols 2 and 9, the channel values are estimated for the remaining symbols (the symbol index indicated by '*' in FIG. 4 is not current). Symbol in the next subframe).

In this case, a symbol index in time for obtaining a reference signal for linear interpolation is t, a linear interpolation factor is α, and a symbol index with an adjacent reference signal is t ', t' ', and the symbol estimate f (t) is as follows. It is shown together.

f (t) = α × f (t ') + (1-α) × f (t' ')

Upon completion of step S240, the synchronized data and channel estimates are temporarily stored in a temporary storage unit (e.g., a buffer, etc.) (S250), which is a reference signal when locating a channel with respect to a signal propagation path. This is to avoid overlapping.

Subsequently, PBCH, PCFICH, PHICH, PDCH, and PDSCH, which are channels for a signal propagation path, are extracted from the synchronized data based on the temporarily stored channel estimate, and output in the extraction order (S260). And since the position on the frequency is fixed and only in one subframe of one radio frame, it is only demodulated in that subframe. For example, it may be subframe 1 of 10 subframes constituting one radio frame.

Since the PBCH is updated at the time of connection or handover, the PBCH is searched every time an event occurs through higher control.

The PCFICH finds the position in the first OFDM symbol of every subframe on the time axis, and indicates how many OFDM symbols the PDCCH occupies because no other channel can come to the position of the PCFICH. Occupy until.

The PHICH is found at a location excluding the time and frequency resources allocated to the PCFICH.

The PDCCH is determined by the PCFICH in time, and is found in the frequency except the positions occupied by the PCFICH and PHICH in frequency.

The PDSCH is located in an OFDM symbol different from the channels, but the PDSCH is finally extracted because the position of the PDCCH can be found in order to find the position on the frequency. Since the time axis position is located in all the OFDM symbols without the PDCCH, the channels are The search is performed at a position without a synchronization signal and a reference signal among the missing OFDM symbols.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example and can be variously changed in the range which does not deviate from the summary.

1 is a block diagram schematically illustrating a configuration of a terminal demodulation system supporting a MIMO and OFDM transmission scheme according to an embodiment of the present invention.

2 is a flowchart illustrating a demodulation process in a terminal demodulation system according to an embodiment of the present invention.

3 is a view showing a reference signal allocation according to the 3GPP LTE standard according to an embodiment of the present invention.

4 illustrates a linear interpolation factor in a symbol without a reference signal according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: terminal demodulation system 110: multi-carrier demodulator

111: protection section removal section 112: FFT section

113: guard band removal unit 120: channel estimator

121: reference signal extractor 122: frequency interpolator

123: linear interpolator 130: frame deformatter

131: PBCH extractor 132: PCFICH extractor

133: PHICH extractor 134: PDCCH extractor

135 PDSCH extractor 136 temporary storage (buffer)

Claims (10)

Multi-carrier demodulator for extracting valid data through guard interval elimination, fast Fourier transform and guard band rejection A channel estimator extracting a reference signal from the extracted valid data to synchronize valid data, and calculating and outputting a channel estimate according to the antenna combination through frequency and linear interpolation; And a frame deformatter for sequentially extracting a channel for a signal propagation path from the synchronized data based on the channel estimate and supporting the MIMO and OFDM transmission scheme. The multicarrier demodulator of claim 1, wherein the multicarrier demodulator A guard section removal unit for removing the guard interval inserted after the inverse fast Fourier transform at the time of outputting the final signal from the base station modulator; An FFT unit for outputting the data of the time axis as the data of the frequency axis through the fast Fourier transform of the signal from which the guard interval is removed; And a guard band removal unit for removing valid guard bands from the data on the frequency axis and outputting valid data. The channel estimator of claim 1, wherein the channel estimator A reference signal extracting unit for extracting a reference signal from the valid data; A frequency interpolator for outputting a channel estimate by performing FFT interpolation on a frequency in a section including the reference signal; And a linear interpolator for outputting a channel estimate by performing linear interpolation on a new signal in a section in which there is no reference signal. The method of claim 1, The channel estimate is an estimate according to the plurality of antenna combinations, And the valid data is data carried on a subcarrier according to a frequency band excluding a guard band. The method of claim 1, wherein the frame deformatter A PBCH extractor for extracting a physical broadcast channel (PBCH) including values related to cell characteristics broadcast throughout the cell; PCFICH extraction unit for extracting a physical control format indicator channel (PCFICH) for transmitting the number of OFDM symbols, A PHICH extraction unit for extracting a PHICH (physical hybrid ARQ indicator channel) disposed at a location except for time and frequency resources allocated to the PCFICH; A PDCCH extractor for extracting a physical downlink control channel (PDCCH) located on a frequency other than the positions occupied by the PCFICH and PHICH; And a PDSCH extractor for extracting a physical downlink shared channel (PDSCH) located at a position in which there is no synchronization signal and a reference signal among the OFDM symbols without the channels. The method of claim 5, wherein the PBCH extractor A UE demodulation system supporting MIMO and OFDM transmission schemes in which PBCH is extracted only when an event of initial access or handover occurs. The method of claim 5, The PDSCH is located in accordance with the result of decoding the PDCCH terminal demodulation system supporting the MIMO and OFDM transmission scheme. The method of claim 5, The frame deformatter is a terminal demodulation system that supports the MIMO and OFDM transmission scheme that is located in a position that does not overlap with a reference signal when the position of the channels. The method of claim 5, And a temporary storage means for temporarily storing the synchronized data and the channel estimate so that reference signals do not overlap when the location of the channel is found by each extractor. Extracting valid data through guard interval elimination, fast Fourier transform, and guard band rejection of data signals inputted from a plurality of antennas, Extracting a reference signal from the extracted valid data and synchronizing valid data by comparing with a preset reference signal; Outputting a channel estimate by performing FFT interpolation on a frequency in a section in which the reference signal is present; Outputting a channel estimate by performing linear interpolation on time in a section without the reference signal, Temporarily storing the synchronized data and a channel estimate so that the reference signals do not overlap; And extracting a channel for a signal propagation path from the synchronized data based on the temporarily stored channel estimate and sequentially outputting the channel for a signal propagation path.

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