KR101078972B1 - Ｍ－ａｒｙ ｄｕａｌ ｃａｒｒｉｅｒ ｍｏｄｕｌａｔｉｏｎ ｄｅｍｏｄｕｌａｔｉｏｎ ｍｅｔｈｏｄ ｂａｓｅｄ ｏｎ ｍｕｌｔｉ－ｂａｎｄ ｏｒｔｈｏｇｏｎａｌ ｆｒｅｑｕｅｎｃｙ ｄｉｖｉｓｉｏｎ ｍｕｌｔｉｐｌｅｘｉｎｇ ｓｙｓｔｅｍ ａｎｄ ａｐｐａｒａｔｕｓ ｔｈｅｒｅｏｆ - Google Patents

Abstract

The present invention relates to a M-ary DCM demodulation method and apparatus based on MB-OFDM system. MB-OFDM-based M-ary DCM demodulation method according to the present invention comprises the steps of: receiving a M- DCM signal pair based on MB-OFDM, selecting a first DCM signal of high reliability among the M-DM DCM signal pair, 1, detecting a temporary candidate symbol from a DCM signal, further selecting C-1 candidate symbols adjacent to the temporary candidate symbol in the first DCM signal, and selecting a total of C (C is a natural number less than M) symbols Selecting a symbol, selecting a symbol corresponding to a bit string of C symbols as a candidate symbol in a second DCM signal paired with the first DCM signal, and receiving each received signal value of the M-ary DCM signal pair; Demodulating using the distance between the C candidate symbols. As described above, even when demodulating considering only a relatively small number of candidate symbols among all the symbols included in the DCM signal, compared to the prior art, efficient performance can be obtained.

M, MB-OFDM, DCM, MDCM

Description

Gene M based on the MB-OFDM system demodulation method and apparatus DCM {M-ARY DUAL CARRIER MODULATION DEMODULATION METHOD BASED ON MULTI-BAND ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM AND APPARATUS THEREOF}

The present invention relates to a M-ary DCM demodulation method and apparatus based on an MB-OFDM system, and more particularly, to an M-based DCM based MB-OFDM system that performs demodulation by considering only some candidate symbols among all symbols included in a DCM signal. DCM demodulation method and apparatus.

Ultra Wide Band (UWB) wireless communication systems based on Multi-band Orthogonal Frequency Division Multiplexing (MB-OFDM) have similar levels of noise levels to bandwidths up to 528 MHz per band. Since communication is performed using very low power, it is easy to share with existing narrowband systems, and it is possible to provide a much higher data rate than other wireless communication systems currently developed.

The MB-OFDM system is one of UWB transmission methods. The MB-OFDM system can distinguish 8 transmission modes according to a transmission rate. The MB-OFDM system uses a dual carrier modulation (DCM) and a modified DCM (MDCM) modulation technique in a high-speed transmission mode. I use it.

DCM technology in the form of 16-QAM (Quadrature Amplitude Modulation) modulates four input bits with two 16-QAM modulators with different constellations, and transmits the modulated signal on two carriers as far away as possible. Technology.

In addition, the 256-QAM MDCM technology modulates eight input bits using two 256-QAM modulators with different constellations, and transmits the modulated signal on two carriers as far as possible.

This allows the same information to be transmitted twice, reducing the rate to half but using two different constellations designed for low correlation so that the same rate under the Additive White Gaussian Noise (AWGN) channel It provides the same bit error rate performance as the existing modulation technique. In addition, under a frequency selective channel, even if one carrier suffers from severe fading, the original signal can be estimated using information carried on the other carrier, which is superior to conventional modulation techniques having the same bit rate. You can expect error rate performance.

However, M-ary DCM is a relatively higher-order modulation technique and the received signal pairs must be considered at the same time when demodulating. As M increases, demodulation complexity increases rapidly when demodulating a signal using ML (Maximum Likelihood), a general demodulation technique. Will increase.

Accordingly, an aspect of the present invention is directed to a method and apparatus for demodulating M-ary DCM based on MB-OFDM capable of performing demodulation considering only some candidate symbols among all symbols included in the M-ary DCM signal.

M-MIN DCM demodulation method based on the MB-OFDM system according to an embodiment of the present invention for achieving the technical problem, M-Minal Dual Carrier Modulation (DCM) signal pair based on multi-band orthogonal frequency multiple division (MB-OFDM) Receiving a first DCM signal having a high reliability among the M-ary DCM signal pairs, detecting a temporary candidate symbol from the first DCM signal, and centering the temporary candidate symbol in the first DCM signal Further selecting the adjacent C-1 candidate symbols, and selecting the total C (C is a natural number smaller than M) symbols as candidate symbols, in the second DCM signal paired with the first DCM signal, Selecting a symbol corresponding to a bit string of the C symbols as a candidate symbol, and demodulating by using a distance between each received signal value of the signal pair and the C candidate symbols.

Detecting a temporary candidate symbol from the first DCM signal, detects a temporary candidate symbol satisfying the following equation.

는 수신단에서 추정한 원 신호를 나타낸다. Here, k is a subcarrier index of the first DCM signal, G ¹ is a set of candidate symbols included in the first DCM signal, Y _k is a signal received through the k- th subcarrier, H _k is a k- th subcarrier Indicates the subchannel that passed,

Denotes the original signal estimated by the receiver.

Demodulating by using each received signal value of the M-ary DCM signal pair and the distance between the C candidate symbols, detecting and demodulating a symbol satisfying the following equation from the candidate symbol.

_k+i 는 수신단에서 추정한 원 신호를 나타낸다. Here, U ¹ and U ² are sets including only C candidate symbols selected from a total of M candidates included in the first DCM signal and the second DCM signal, respectively, and k + i is a subcarrier of the second DCM signal. Is an index, Y _{k + i} denotes a signal received on the k + i th subcarrier, H _{k + i} denotes a subchannel through which the k + i th subcarrier passed,

_{k + i} represents the original signal estimated by the receiver.

The M-ary DCM demodulation apparatus based on the MB-OFDM system according to another embodiment of the present invention, Signal receiving unit for receiving a M- binary Dual Carrier Modulation (DCM) signal pair based on multi-band orthogonal frequency multiple division (MB-OFDM), A signal selector for selecting a first DCM signal having a high reliability among the M-ary DCM signal pairs, a pre-detector for detecting a temporary candidate symbol from the first DCM signal, and a close proximity to the temporary candidate symbol in the first DCM signal A first candidate symbol selector configured to further select C-1 candidate symbols, and select a total of C (C is a natural number smaller than M) symbols as candidate symbols, and a second DCM paired with the first DCM signal; In the signal, a second candidate symbol selector for selecting a symbol corresponding to a bit string of the C symbols as a candidate symbol, and using the distance between each received signal value of the M-ary DCM signal pair and the C candidate symbols And a demodulation section to demodulate.

According to the present invention, even when demodulating in consideration of only a relatively small number of candidate symbols among all symbols included in the DCM signal, a similar performance can be obtained, thereby enabling efficient demodulation. Therefore, the present invention can reduce the power consumption of the MB-OFDM based ultra-wideband wireless communication system device to extend the battery life.

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 the following, DCM and MDCM are named 16-DCM and 256-DCM, so that their characteristics are clearly distinguished.

First, a demodulation method of a general M-ary DCM will be described with reference to FIGS. 1A and 1B. 1A and 1B are diagrams showing constellations for explaining a DCM demodulation method based on a general MB-OFDM system.

In more detail, FIG. 1A shows the constellation of the first DCM signal generating e _k , which is the first signal of the 256-DCM signal pair, and FIG. 1B shows the second signal e _{k + i} , which is the second signal of the 256-DCM signal pair. Each shows the constellation of the 2nd DCM signal which produces | generates.

In each constellation, the horizontal axis represents the real part, the vertical axis represents the imaginary part, and in FIG. 1A and FIG. 1B, the x marks indicate the received signal on the constellation.

When eight input bits from b ₀ to b ₇ are input, two 256-DCM signals are generated by each modulator, which form a signal pair. Demodulation of M-ary DCM using a general ML method is performed using the following equation.

는 수신단에서 추정한 원 신호를 나타낸다. Here, k and k + i are subcarrier indexes of the signal pair, and G ¹ and G ² are sets of candidate symbols included in the first DCM signal and the second DCM signal, respectively, which constitute the signal pair. Also, Y _k is a signal received through the k th subcarrier, H _k is a subchannel through which the k th subcarrier has passed,

Denotes the original signal estimated by the receiver.

In the case of M-ary DCM, since G ¹ and G ² each have M candidates, as the M value increases, the demodulation complexity rapidly increases.However, unlike conventional modulation techniques, M-ary DCM requires consideration of signal pairs simultaneously. Normal demodulation cannot reduce the complexity of demodulation.

2 is a block diagram of a DCM demodulation device based on an MB-OFDM system according to an embodiment of the present invention. MB-OFDM-based DCM demodulation device 200 according to an embodiment of the present invention is a signal receiver 210, a signal selector 220, a pre-detector 230, a first candidate symbol selector 240, a second The candidate symbol selector 250 and the demodulator 260 are included.

The signal receiver 210 receives the M-ary DCM signal pair based on MB-OFDM from the transmitter. The signal selector 220 selects a DCM signal having high reliability from among the received M-DCM signal pairs using the estimated channel information value.

The pre-detector 230 detects the most likely symbol as a temporary candidate symbol by using a distance from the selected DCM signal in the selected DCM signal.

The first candidate symbol selector 240 additionally selects the C-1 closest candidate symbols centering on the pre-detected temporary candidate symbols and selects a total of C (C is a natural number smaller than M) symbols as candidate symbols. Select.

The second candidate symbol selector 250 expands and applies candidate symbol selection by selecting a symbol corresponding to a bit string of C symbols as a candidate symbol among DCM signals forming a signal pair with a highly reliable DCM signal.

The demodulator 260 demodulates using the Euclidean distance and channel information between each received signal value of the M-ary DCM signal pair and the C candidate symbols.

Hereinafter, an M-based DCM demodulation method based on MB-OFDM system according to an embodiment of the present invention will be described with reference to FIGS. 3 to 4B. 3 is a flowchart illustrating a M-DCM demodulation method based on an MB-OFDM system according to an embodiment of the present invention, and FIGS. 4A and 4B are diagrams illustrating constellations for describing an embodiment of the present invention.

FIG. 4A shows a constellation of the first DCM signal generating e _k , which is the first signal of the 256-DCM signal pair, as in FIG. 1A, and FIG. 4B shows e _{k + i} , the second signal of the 256-DCM signal pair. The constellations of the generated second DCM signals are respectively shown. In particular, when the reliability of the first signal e _k among 256-DCM received signal pairs is high, it is a diagram showing an example of selecting candidate symbols when C = 9.

According to an embodiment of the present invention, since the signal pairs of the M-ary DCM are received through different subchannels, the M-levels are performed through the following procedure utilizing channel information, taking into consideration that their reliability is different. Demodulate the DCM signal.

First, the MB-OFDM-based DCM demodulation device 200 uses M-based symbols as shown in FIGS. 4A and 4B by using estimated channel information. Y _k and Y _{k + i,} which are signal pairs of DCM, are received (S310).

In FIG. 4A and FIG. 4B, the x mark indicates the received signal in the constellation diagram.

The signal selector 220 selects a signal having high reliability from among the signal pairs Y _k and Y _{k + i} through the channel estimation method (S320). The channel estimation is performed from a signal that has passed through the FFT, and may be performed by adopting a least square method using a channel estimation sequence provided by the MB-OFDM. Therefore, the reliability may be determined using the channel state information obtained by channel estimation. In the embodiment of the present invention, M binary for convenience. _{Assume that} the reliability of Y _k corresponding to the first DCM signal among the DCM signal pairs is higher than the reliability of Y _{k + i} corresponding to the second DCM signal.

The pre-detector 230 detects a temporary candidate symbol from the selected signal Y _k (S330). That is, the pre-detector 230 pre-detects 256 e _k symbols included in G ¹ and a symbol satisfying Equation 2 with respect to the received signal Y _k as temporary candidate symbols.

는 수신단에서 추정한 원 신호를 나타낸다. Here, k is a subcarrier index of the first DCM signal, G ¹ is a set of candidate symbols included in the first DCM signal, Y _k represents a signal received through the k th subcarrier, H _k is a k th subcarrier Indicates the subchannel through which

Denotes the original signal estimated by the receiver.

Therefore, through Equation 2, a symbol having a minimum result value is detected in advance. Since the reliability of the Y _k is higher than the reliability of the Y _{k + i} is the pre-detected with the highest possible bit sequences won a signal from the candidate symbol e _k. In the embodiment of the present invention, it is assumed that [ b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ] = [01010101] is pre-detected, and the pre-detected temporary candidate symbol is indicated by a in FIG. 4A. .

Next, the first candidate symbol selecting unit 240 additionally selects the C-1 closest candidate symbols centering on the pre-detected symbols among the G ¹ corresponding to the first DCM signal, and totals C symbols. Is selected as a candidate symbol (S340).

That is, the closest 8 (= 9-1) additional candidate symbols around the pre-detected symbol are selected. In FIG. 4A, symbols included in a circle around a symbol are candidate symbols to which are added. In the embodiment of the present invention, since C = 9, eight additional candidate symbols are selected based on pre-detected symbols.

In addition, the second candidate symbol selector 250 may G ² corresponding to the second DCM signal. The symbol corresponding to the bit string of the C symbols selected as the candidate symbols in G ¹ is enlarged and selected as the candidate symbols (S350).

That is, the symbols corresponding to the bit strings of the nine candidate symbols selected in FIG. 4A are enlarged and selected as candidate symbols as shown in FIG. 4B. In FIG. 4B, the selected nine candidate symbols are indicated by dotted circles. For example, for [ b ₀ b ₁ b ₂ b ₃ b ₄ b ₅ b ₆ b ₇ ] = [0110100] symbol selected as an additional candidate symbol in FIG. 4a, it is also extended to G ² as a signal pair.

The demodulator 260 demodulates using the Euclidean distance and channel information between each received signal value of the signal pair and the C candidate symbols (S360). The demodulator 260 demodulates using Equation 3 below.

Here, U ¹ and U ² are sets including only C candidate symbols selected from a total of M candidates included in M-ary DCM modulator-1 and M-ary DCM modulator-2, respectively. As shown in Equation 3, Euclidean operations are performed on the C candidate symbols belonging to U ¹ and U ² , respectively, and a candidate symbol having a minimum sum of Euclidean operations is detected.

번의 덧셈과

번의 곱셈을 필요로 하는데, 여기서 덧셈은 2개의 변조기에서 실수부와 허수부의 유클리드 거리를 계산하는 것(

)과 실수부와 허수부의 유클리드 거리를 합하는 것(

), 그리고 실수부와 허수부에서 각각

개 중 가장 작은 값을 찾는 것(

)을 포함한다. 그리고, 곱셈은 실수부와 허수부에서

개의 원소를 갖는 값들의 곱 (

)으로 이루어진다. On the other hand, since M bits are mapped independently to the real part and the imaginary part during M-ary DCM modulation, it is possible to reduce the demodulation complexity by separately demodulating the real part and the imaginary part. The number of additions and multiplications required according to the C value of the present invention based on Equations 2 and 3 is as follows. ML method

Addition of times

Multiplication is required, where the addition involves calculating the Euclidean distances of the real and imaginary parts of the two modulators.

) And the Euclidean distance of the real part and the imaginary part

), And real and imaginary

To find the smallest value of

). And, multiplication in real and imaginary parts

Of values with elements

)

번의 덧셈과

번의 곱셈을 필요로 하는데, 여기서 덧셈은 사전 검출 단계에서 실수부와 허수부 비트의 사전 결정을 위한

번, C개의 후보들을 선정하는데 있어

이 짝수인 경우, 근접 후보 비트 검색을 위해 추가로 요구되는 1번, C개의 후보들을 확대 선정하는 단계에서의

번을 포함하며, 곱셈은 ML 방식인 경우에서 C개만 고려할 때와 동일하다. On the other hand, the method according to the present invention

Addition of times

Multiplication times are required, where addition is used to determine the real and imaginary bits in advance in the pre-detection phase.

In selecting C candidates

If the number is even, the number of candidates, which are additionally required for the proximity candidate bit search, is expanded.

Multiplication is the same as when considering only C in the ML method.

는 1, 음이면

는 0의 값으로 사전 결정될 수 있다. 만약

가 성상도에 존재하는 가장 큰 값이라 했을 때,

가 0이라면

를 등화된 신호에 더하고,

가 1인 경우에는

를 등화된 신호에서 뺀 후 그 결과 값의 부호에 따라 음이면

이 0, 양이면

이 1로 사전 결정된다. 같은 방법으로

및

의 가감을 통해

과

을 사전 결정할 수 있다.The number of additions required in the pre-detection step will be described in detail. Since both constellations of M-ary DCMs have a repetitive structure, each bit can be predetermined by adding or subtracting a received-and-equalized signal. For example, if the real part of the left constellation of FIG. 1 is positive,

Is 1, negative

May be predetermined as a value of zero. if

Is the largest value in the constellation,

Is 0

To the equalized signal,

Is 1

Is subtracted from the equalized signal and is negative according to the sign of the result.

Is 0, positive

This is predetermined as 1. In the same way

And

Through

and

Can be determined in advance.

Table 1 compares the demodulation complexity through the number of additions and multiplications required according to the ML method and the C value of the present invention during 256-DCM demodulation.

5 is a graph comparing a bit error rate according to the C value of the present invention when the MB-OFDM-based ultra-wideband wireless communication system transmits in the 800Mbps mode using 256-DCM. Where the vertical axis is the bit error rate and the horizontal axis is the signal-to-noise ratio. The simulation assumes perfect time and frequency synchronization and channel estimation. C = 1 is the same as the demodulation using only one signal of high reliability among the received signal pairs, and C = 256 is the same as the demodulation using the general ML method.

The demodulation method invented through Table 1 and FIG. 5 can be confirmed to obtain reliability comparable to the ML method even with a C value having a relatively very low complexity.

In the description and simulation of the present invention, only 256-DCM is dealt with, but the present invention can be applied to demodulation of any M-ary DCM signal, and the effect becomes larger as the M value becomes larger.

As described above, according to the conventional ML method described with reference to FIGS. 1A and 1B, since M candidates of a received signal pair must be considered in order to demodulate the M-ary DCM, the complexity rapidly increases as the M value increases. However, according to an embodiment of the present invention, even if demodulation is performed considering only C candidate symbols, which is a relatively small number of total M candidates, performance similar to that of the ML method in which all M are considered can be effectively demodulated. It becomes possible. Therefore, the present invention can reduce the power consumption of the MB-OFDM based ultra-wideband wireless communication system device to extend the battery life.

Meanwhile, the M-ary DCM demodulation method based on the above-described MB-OFDM system is implemented by computer-readable codes / instructions / programs. For example, the method may be implemented in a general-purpose digital computer operating the code / instructions / program using a computer readable recording medium. The computer-readable recording media may include magnetic storage media (ex, ROM, floppy disk, hard disk, magnetic tape, etc.), optical reading media (ex, CD-ROM, DVD, etc.) and carrier waves (ex, transmission via the Internet). Storage media, and the like. In addition, embodiments of the present invention may be implemented as a medium (s) containing computer readable code, such that a plurality of computer systems connected via a network can be distributed and processing operations. It is obvious that the functional programs, codes and code segments realized by the method of the present invention can be easily inferred by programmers in the technical field to which the present invention belongs.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1A and 1B are diagrams showing constellations for explaining a DCM demodulation method based on a general MB-OFDM system.

2 is a block diagram of a DCM demodulation device based on an MB-OFDM system according to an embodiment of the present invention.

3 is a flowchart illustrating a DCM demodulation method based on MB-OFDM system according to an embodiment of the present invention.

4A and 4B are diagrams showing constellations for describing an embodiment of the present invention.

5 is a graph comparing a bit error rate according to the C value of the present invention when the MB-OFDM-based ultra-wideband wireless communication system transmits in the 800Mbps mode using 256-DCM.

Claims (6)

Receiving a M-ary Dual Carrier Modulation (DCM) signal pair based on multiband orthogonal frequency multiple division (MB-OFDM), Selecting a first DCM signal having a high reliability among the M-ary DCM signal pairs using channel state information passed through the M-ary DCM signal pairs; Detecting a temporary candidate symbol from the first DCM signal, Further selecting adjacent C-1 candidate symbols based on the temporary candidate symbols in the first DCM signal, and selecting a total of C (C is a natural number smaller than M) symbols as candidate symbols; Selecting a symbol corresponding to a bit string of the C symbols as a candidate symbol in a second DCM signal paired with the first DCM signal, and Demodulating using each received signal value of the M-ary DCM signal pair and the distance between the C candidate symbols. The method of claim 1, Detecting a temporary candidate symbol from the first DCM signal, M-ary DCM demodulation method based on MB-OFDM system for detecting temporary candidate symbols satisfying the following equation:

Here, k is a subcarrier index of the first DCM signal, G ¹ is a set of candidate symbols included in the first DCM signal, Y _k is a signal received through the k- th subcarrier, H _k is a k- th subcarrier Indicates the subchannel that passed,

Denotes the original signal estimated by the receiver. 3. The method of claim 2, Demodulating by using the distance between each received signal value of the M-ary DCM signal pair and the C candidate symbols, A M-ary DCM demodulation method based on the MB-OFDM system which detects and demodulates a symbol satisfying the following equation from the candidate symbol:

Here, U ¹ and U ² are sets including only C candidate symbols selected from a total of M candidates included in the first DCM signal and the second DCM signal, respectively, and k + i is a subcarrier of the second DCM signal. Is an index, and Y _{k + i} represents a signal received on the k + i th subcarrier, H _{k + i} represents a subchannel through which the k + i th subcarrier passed,

_{k + i} represents the original signal estimated by the receiver. A signal receiver for receiving an M-ary dual carrier modulation (DCM) signal pair based on multi-band orthogonal frequency multiple division (MB-OFDM), A signal selector configured to select a first DCM signal having a high reliability among the M-ary DCM signal pairs by using channel state information passed through the M-ary DCM signal pairs; A pre-detector detecting a temporary candidate symbol from the first DCM signal; A first candidate symbol selecting unit configured to further select adjacent C-1 candidate symbols based on the temporary candidate symbols in the first DCM signal and to select a total of C (C is a natural number smaller than M) symbols as candidate symbols , A second candidate symbol selector that selects a symbol corresponding to a bit string of the C symbols as a candidate symbol in a second DCM signal paired with the first DCM signal, and M-based DCM demodulation device comprising a demodulator for demodulating by using the received signal value of the M-DM DCM signal pair and the distance between the C candidate symbols. 5. The method of claim 4, The pre-detector, An M-ary DCM demodulation device based on an MB-OFDM system which detects a temporary candidate symbol satisfying the following equation from the first DCM signal:

Here, k is a subcarrier index of the first DCM signal, G ¹ is a set of candidate symbols included in the first DCM signal, Y _k is a signal received through the k- th subcarrier, H _k is a k- th subcarrier Indicates the subchannel that passed,

Denotes the original signal estimated by the receiver. The method of claim 5, The demodulation unit, M-ary DCM demodulation device based on MB-OFDM system which detects and demodulates a symbol satisfying the following equation from the candidate symbol:

Here, U ¹ and U ² are sets including only C candidate symbols selected from a total of M candidates included in the first DCM signal and the second DCM signal, respectively, and k + i is a subcarrier of the second DCM signal. Is an index, and Y _{k + i} represents a signal received on the k + i th subcarrier, H _{k + i} represents a subchannel through which the k + i th subcarrier passed,

_{k + i} represents the original signal estimated by the receiver.

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