KR101660875B1 - Zero Crossing Demodulation based Receiver and Driving Method Thereof - Google Patents

Abstract

In the embodiment of the present invention, for example, a demodulation is performed using a LLR value stored in a look-up table form while reducing hardware complexity in a wireless communication receiver that performs near-field communication such as ZigBee based on zero crossing demodulation, To a zero crossing demodulation based receiver and a driving method thereof for improving performance. A zero-crossing demodulation-based receiver according to an embodiment of the present invention includes an RF signal processor for receiving an RF signal and converting the received RF signal into a channel frequency band signal and outputting the RF signal, and a zero crossing point detecting unit for detecting a zero crossing point from the channel frequency band signal, And a demodulation unit for extracting the number of zero crossings for the symbol (n) and the total time of the zero crossing number, and selecting and outputting the LLR value using the zero crossing number and the total time.

Description

[0001] Zero Crossing Demodulation Based Receiver and Driving Method Thereof [

Embodiments of the present invention relate to a zero crossing demodulation based receiver and a method of driving the same. More specifically, in a wireless communication receiver that performs near-field communication such as Zigbee based on zero crossing demodulation, demodulation is performed using a LLR (Log-likelihood ratio) value stored in a look- To a zero crossing demodulation based receiver and a driving method thereof for improving the performance of a wireless communication receiver.

2. Description of the Related Art Generally, a digital transmission / reception device for short-distance transmission of voice and sound signals capable of digitally transmitting and receiving audio or voice signals provided by an audio device or a portable telephone within a limited distance includes a frequency modulation (FM) A signal is transmitted using a method such as Amplitude Modulation, Frequency Shift Keying (FSK), Amplitude Shift Keying (ASK), Minimum Shift Keying (MSK), and Quadrature Phase Shift Keying (QPSK) And demodulates the received signal.

Among them, FSK is a modulation method in which the frequency of a sinusoidal wave having a constant amplitude is set to two and data assigned to one of the two frequencies is transmitted to the other side as the data changes to 1 or 0. For example, in the case of binary FSK, FSK is a system in which the carrier frequency is changed according to the digital signal for 0 and 1, and the binary 1 and 0 are corresponded to the high frequency and the low frequency two frequencies in which the center frequency is inserted .

 Such FSK is more resistant to errors than ASK and is relatively simple to use in data transmission. Such FSK is easy to construct and is relatively strong in long distance transmission, and is widely used in public communication network (PSTN). FSK is mainly used for asynchronous transmission of relatively low data rate of 200 bps or less.

FIG. 1 is a diagram showing a structure of a general wireless communication system, and FIG. 2 is a waveform showing an example of a data signal transmitted from the transmitting apparatus of FIG.

1 and 2, a wireless communication system includes a transmitting apparatus 100 for modulating and transmitting a data signal, and a receiving apparatus 110 for receiving and demodulating a data signal transmitted from the transmitting apparatus 100 do.

Here, in the case of the FSK scheme, the transmitting apparatus 100 modulates bit 1 corresponding to a high frequency and 0 to a low frequency as shown in FIG. 2, and transmits the modulated data signal to the receiving apparatus 110.

The receiving apparatus 110 of the FSK scheme receives the data signal transmitted from the transmitting apparatus 100 and corresponds to 1 in the case of a high frequency higher than a predetermined reference value and to 0 in the case of a low frequency lower than a reference value Demodulate the digital data.

As a result, it is most importantly considered in this receiving apparatus 110 how accurately and simply how to demodulate the digital data from the frequency. Accordingly, various demodulation schemes may be used for the receiving apparatus 110 such as the FSK scheme.

At present, zero crossing demodulation is well known as a method for accurately detecting data. Here, zero crossing is a concept that is often used in a stable control of electronic circuits and a sound forge program. In other words, in the electronic circuit, the AC voltage has a sinusoidal waveform. It is used to detect the moment when the voltage passes through the OV and to control the ON / OFF at this point to prevent a sudden current change. If the value of the negative waveform goes up or down between the positive and negative values along the axis of time when it is called, the point at which the magnitude of the sound becomes zero is called the zero crossing. Zero crossing point is cut to the point, and it is used to attach to front and back.

However, the conventional receiver 110 using the zero crossing demodulation demodulates the data by associating the received data signal with only the high frequency 1 and the low frequency 0, so that the performance of the system is not improved in terms of the quality of service such as resolution .

The embodiment of the present invention is based on a zero crossing demodulation based on a soft demodulation based on soft LLR values stored in a lookup table form in a memory in a demodulation of a signal in a wireless communication receiver performing near- And a method of driving the same.

A zero-crossing demodulation-based receiver according to an embodiment of the present invention includes an RF signal processor for receiving an RF (Radio Frequency) signal and converting the received RF signal into a channel frequency band signal and outputting the signal, and for detecting a zero crossing point from the channel frequency band signal, And a demodulation unit for extracting a total number of zero crossings for the arbitrary unit symbol (n) and a total number of the zero crossings, and outputting a log-likelihood ratio (LLR) value corresponding to the number of zero crossings and the total time .

Also, a method of driving a receiver based on a zero crossing demodulation according to an exemplary embodiment of the present invention includes detecting a zero crossing point from a channel frequency band signal obtained by receiving an RF (Radio Frequency) signal and using the detection information of the zero crossing point Calculating a zero crossing number for any unit symbol (n) having data information and a total time of the zero crossing number; Comparing the number of zero crossings with a first comparison value stored in the memory unit to determine whether the number of zero crossings is out of the range of the first comparison value; Comparing the second comparison value stored in the memory unit with the total time according to the column of the first comparison value matched with the number of zero crossings when the number of zero crossings is not out of the range of the first comparison value Determining whether the total time is less than the second comparison value; And outputting a log-likelihood ratio (LLR) value matching the second comparison value when the total time is less than the second comparison value.

According to the embodiment of the present invention, the signal is demodulated using the soft LLR values in the demodulation of the receiver of the wireless communication, so that the performance of the system can be improved without increasing the hardware complexity. That is, the cost efficiency can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing the structure of a general wireless communication system,
FIG. 2 is a waveform diagram showing an example of a data signal transmitted from the transmission apparatus of FIG. 1;
3 is a diagram illustrating a structure of a zero crossing demodulation based receiver according to an embodiment of the present invention;
FIG. 4 is a diagram for explaining a zero crossing point detection, a zero crossing number determination, and a delta value summing process in the demodulation unit of FIG. 3;
FIG. 5 is a diagram for explaining a calculation method of an LLR value stored in the memory unit of FIG. 3;
6 is a diagram illustrating a signal demodulation process in the demodulation unit of FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals as possible, as they can be displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

FIG. 3 is a diagram illustrating a structure of a zero-crossing demodulation-based receiver according to an embodiment of the present invention. FIG. 4 is a block diagram illustrating a zero crossing point detection, a zero crossing number determination, FIG.

3 and 4, the zero-crossing demodulation-based receiver according to the embodiment of the present invention includes an RF signal processing unit 310 and a demodulation unit 320. The zero crossing demodulation based receiver may further include a receive antenna 300 for receiving an RF signal.

The RF signal processing unit 310 converts an RF signal received through the reception antenna 300 into a channel frequency band signal and outputs the channel frequency band signal. For example, the RF signal processing unit 310 according to an embodiment of the present invention may include a low noise amplifier (LNA) 311, a mixer 313, and a band pass filter (BPF) 315. The mixer 313 mixes the amplified RF signal with a local oscillation signal provided from an external local oscillator to generate a baseband signal, Band pass filter 315 selects and outputs a channel frequency band signal from the baseband signal.

The RF signal processing unit 310 may be variously modified according to the embodiment of the present invention. In other words, if the zero crossing demodulation based receiver according to the embodiment of the present invention is applied to an apparatus for performing, for example, Zigbee communication, the RF signal processing unit 310 may constitute a part of the MSK receiver. Here, the MSK receiver receives and processes a signal provided by OQPSK (Offset Quadrature Phase Shift Keying) modulation at a transmitter, or receives and processes a signal provided through a DSSS (Direct Sequence Spread Spectrum) based MSK modulation process , And a signal modulated by the MSK scheme is received through the FSK demodulation process. Generally, the MSK signal is generated by an OQPSK scheme employing a sine filter as a pulse shaping filter. Here, the MSK signal generated according to the polarity of the sine filter is classified into two types. In the first type, the sine filter is used. In the second type, the sine is subjected to the filtering after the absolute value is taken . Due to this difference, the two forms of MSK show a completely different contrast between the input data and the frequency of the generated signal.

The demodulator 320 receives the output signal of the RF signal processor 310, that is, the channel frequency band signal of the band pass filter 315, and then converts the digital signal into a digital signal. More precisely, the demodulator 320 detects (or calculates) the zero crossing point (t ₁ to t _{n + 1} ) of the channel frequency band signal, for example, to recover accurate digital data from the channel frequency band signal, zero crossing point by _{(t 1 ~ t n + 1} ) based on the detected information about the time of the zero crossing number (Z _{δ, n)} and the zero crossing number (Z _{δ, n)} for any of the symbols (n) And calculates one sum of the LLR values of one of the LLR values represented by the seven codewords selected on the lookup table (LUT) in accordance with the zero crossing number (Z _{?, N} ) and the sum of the time? To restore digital data.

In digital receivers, fixed-point notation of signals is usually preferred over floating-point notation. Accordingly, the LLR values should be limited to a certain number of bits, and these preconditions may be performed by using a lookup table in a zero crossing demodulation based receiver using ZigBee or the like, as in embodiments of the present invention, In the example, the width of each LLR value can be limited to 3 bits only.

3 and 4, the demodulating unit 320 according to the embodiment of the present invention includes a zero crossing point detecting unit 321, a zero crossing information calculating unit 323, a control unit 325, (327), and may further include an LLR symbol decoding unit (329). The zero crossing point detection unit 321 may include a counter and may detect a zero crossing point t ₁ to t _n of the channel frequency band signal provided by the RF signal processing unit 310 using the clock signal frequency F _CLE provided in the counter ₊₁ ) can be detected. The zero crossing information calculation unit 323 includes a zero crossing number determination unit 323a and a delta value summation unit 323b. The zero crossing number determination unit 323a includes a zero crossing information detection unit 323a, information from the detection zero for any of the symbols (n) crossing number _{(δ Z, n),} and the determination, the delta value summation unit (323b) the zero crossing point (t ₁ ~ t _{n +1)} the spacing between the respective delta calculate the sum (△ n) of time to (δ ₁ ~ δ _n). The control unit 325 also outputs the corresponding LLR value from the memory unit 327 based on the zero crossing number (Z _{?, N} ) provided by the zero crossing information calculation unit 323 and the total sum? And outputs it. The memory unit 327 stores an LLR (n), which corresponds to a first comparison value for comparing with a zero crossing number (Z _{?, N} ) as a lookup table type and a second comparison value for comparing with a total sum? Store the value. The memory unit 327 selects an LLR value mapped to the number of zero crossings (Z _{?, N} ) and the total time _? N of arbitrary symbols (n) provided by the control unit 325 And provides it to the control unit 325. The LLR symbol decoding unit 329 decodes the LLR values provided by the controller 325 and outputs a 32-bit bit stream, for example.

The demodulation unit 320 according to the embodiment of the present invention obtains a temporal difference, i.e., a delta (m) through a zero crossing point detection unit 321. [ These delta (? _M ) correspond to the inverse instantaneous frequency (f _{i , m} ) of the modulated signal. Here, since the number and position of zero crossings associated with a certain symbol are governed not only by the phase of the OQPSK baseband signal but also by the phase of the intermediate frequency signal, and since the symbols are independent of each other, It does not correspond to the index. Thus, the number of zero crossings (Z [ _{delta], n} ) associated with the symbols in embodiments of the present invention may be different.

5 is a diagram for explaining a calculation method of the LLR value stored in the memory unit of FIG.

Referring to FIG. 5 together with FIG. 3, LLR values in the form of a look-up table stored in the memory unit 327 according to an embodiment of the present invention are substantially equal to a value calculated in consideration of noise of a signal received by a zero crossing demodulation- .

For example, suppose that the transmitter transmits a signal in the conventional OQPSK modulation scheme having the same half-sine pulse shape as the MSK specified in the IEEE 802.15.4 standard of Zigbee communication. At this time, if perfect symbol synchronization is estimated, there are two distinct instantaneous frequencies f ⁺ and f ^- . These instantaneous frequencies f ⁺ and f ^- are concentrated around the intermediate frequency f _IF .

Assuming that the MSK modulation index h is 1/2 and the symbol frequency fs, the frequency shift (f) of the modulated signal is fs / 4. Therefore, the instantaneous frequencies f ⁺ and f ^- can be expressed as Equation (1).

[Equation 1]

f ⁺ = f _IF + fs / 4,

f ^- = f _IF - fs / 4

The counter of the zero crossing point detector 321 that generates the delta? M operates at the frequency f _CLK . Therefore, all the frequencies can be represented as a symbol frequency fs as shown in Equation (2) and Equation (3).

&Quot; (2) "

F _IF = f _IF / fs

&Quot; (3) "

F _CLK = f _CLK / fs

Based on Equations (1) to (3), the instantaneous frequencies f ⁺ and f ^- can be expressed as Equation (4).

&Quot; (4) "

F ⁺ = F _IF + 1/4,

F ^- = F _IF - 1/4

When calculating the LLR values as in the embodiment of the present invention, the conditional probability density for the noise processing is considered. Additive white Gaussian noise (AWGN), for example, describes the noise processing in the complex baseband of the received signal. These AWGNs must be converted to the instantaneous frequency domain, that is, amplitude noise must be converted to phase or frequency noise. It is known in the literature, for example, that MSK modulated signals show Tikhonov distribution phase noise processing. The literature shows that the frequency distribution of the MSK modulated signals can be modeled by a normal distribution.

Therefore, the two conditional probability densities for the observed instantaneous frequency (F _ie = f _ie / f _s ) observed at the receiver can be expressed as Equation (5) and Equation (6).

&Quot; (5) "

&Quot; (6) "

Here, F _ie = Fi / Fn and Fn is the deviation of the instantaneous frequency caused by the frequency noise.

Therefore, the LLR value can be calculated using Equation (5) and Equation (6), which is expressed by Equation (7).

&Quot; (7) "

Based on Equation (7), it can be seen that the LLR value has an inclined straight line that depends on the noise variance as shown in FIG. If the straight line is clipped or has a step shape by considering the quantization level and the like in the calculation of the LLR values, the inclined straight line may be ignored.

These LLR values may be represented by Q bit constants. Instead of using one codeword to have an unbiased LLR range, the LLR range is [- 2 ^Q-1 + 1; 2 ^Q-1 - 1].

Equation (7) represents the LLR as a function of the normal effective instantaneous frequency. As mentioned earlier, a zero-crossing demodulation-based receiver obtains delta values that are inversely proportional to the effective instantaneous frequency. In order to avoid the inverse (or inversion) operation, the embodiment of the present invention uses a look-up table form for mapping the delta values of the demodulation unit 320 to their LLR values.

)와 일치한다. △n = Σδ_i는 어떤 심볼(n)에 연계된 델타의 합이라 정의하자. 가수(addends)들의 수는 실질적으로 그 심볼의 제로크로싱 개수(Z_δ,n)와 동일하다.The number of available deltas ( _{Zδ, n} ) for a certain symbol (n) varies in one range (or region) determined by the normal intermediate frequency. The normal intermediate frequency is effectively the average number of zero crossings per symbol (

). Let Δn = Σδ _{i be} the sum of the delta associated with a certain symbol (n). The number of addends is substantially equal to the zero crossing number (Z _{?, N} ) of the symbol.

According to the embodiment of the present invention, the demodulation unit 320, more precisely the zero crossing information calculation unit 323, obtains a pair of (? N, Z _{?, N} ) Can be expressed as follows.

&Quot; (8) "

F _ie = F _CLK · Z _{δ, n} / Δn

The values on the lookup table as shown in Table 1 can be obtained by applying the system parameters of Equation (8) and Equation (9).

&Quot; (9) "

F _IF = 2 [MHz]

F _CLK = 32 [MHz]

Q = 3 [level]

Here, F _IF is an intermediate frequency, F _CLK is a clock signal frequency, and Q is a quantization level.

In Table 1, LLRs are 7 codewords, represented by 3-bit constants. Only the seven codewords containing 0 are actually used to obtain the non-deflected area. So the LLRs are [-3; 3].

+ 1;

- 1]의 범위에서 다루어지기에 충분하다. 실질적인 제로크로싱의 개수가 룩업 테이블에서 다루어질 수 있는 범위를 초과한다면, 전반적 비트 에러 동작을 현저하게 감소하지 않는 한 <수학식 10>이 적용될 수 있을 것이다.F _IF is sufficiently small and a small range of Z _{?, N} in the lookup table, i.e.,

+ 1;

- 1] is sufficient to be covered. If the number of practical zero crossings exceeds the range that can be covered in the look-up table, Equation (10) may be applied so long as it does not significantly reduce the overall bit error operation.

&Quot; (10) &quot;

In applying Equation (10), the demodulation unit 320 can operate as follows.

The demodulation unit 320 first calculates a pair of (? N, Z _{?, N} ) through the zero crossing information calculation unit 323.

The control unit 325 then operates on the upper column on the lookup table of Table 1 based on Z _{?, N} , or on the basis of Equation (10) if it goes out of range. Where Z [ _{delta], n} is compared to the first comparison value on the lookup table associated with the number of zero crossings.

The control unit 325 starts from the first column after selecting the corresponding Z _{delta, n} , and then goes down to check whether? N is smaller than the value stored in the lookup table. At this time, the value stored in the lookup table compared with? N is the second comparison value, and the second comparison value represents the total time for the number of zero crossing.

If it is determined that? N is smaller than the second comparison value, the controller 325 selects and outputs the corresponding Λ _LUT corresponding to Δn of the current column.

The values on the look-up table shown in Table 1 represent the perfect floating-point threshold. Therefore, in the embodiment of the present invention, since the values of DELTA n from the zero crossing information calculation unit 323 are integers, it may be preferable to appropriately convert such values. In other words, when the value of DELTA n is 15.1 or 15.6, the zero crossing information calculating section 323 converts the value of DELTA n of 15.1 or 15.6 to 15, or rounding down the decimal point to 15.1 and 15.6, 16. &Lt; / RTI >

6 is a diagram illustrating a signal demodulation process in the demodulation unit of FIG.

3, the zero crossing information calculator 323 of the demodulator 320 receives a signal provided by the RF signal processor 310, for example, a channel frequency band signal, and outputs a channel frequency band signal and a clock A pair of (? N, Z _{?, N} ) is calculated using the signal frequency (S601). Here, Z _{?, N} can be calculated by the zero crossing number determination unit 323a of the zero crossing information calculation unit 323 as the number of zero crossings _{,? N} is the sum of the number of zero crossings, Can be calculated by the delta value summing unit 323b of the information calculating unit 323. [

Next, the control unit 325 determines whether Z _{?, N} provided by the zero crossing information calculation unit 323 is out of the range on the lookup table stored in the memory unit 327 (S603). In other words, since only the number of zero crossings on the lookup table, which may appear differently depending on noise, is stored for only 1 to 3, it can not be judged when the number of zero crossings is 4 or when the number of zero crossings is zero do. Since the number of zero crossings can be changed as much as possible depending on how the parameters are designed, it is not particularly limited in the embodiment of the present invention. In other words, the number of zero crossings on the lookup table may be designed to be in the range of 2 to 4.

If it is determined that Z _{?, N} provided by the zero crossing information calculation unit 323 does not deviate from the range on the lookup table _{, the} control unit 325 selects a column to be matched on the lookup table, i.e., Z _{?, n} (S605) . Here _{, the} number of zero crossings on the lookup table compared with Z _{?, N} provided by the zero crossing information calculation unit 323 becomes the first comparison value.

Then, the control unit 325 determines whether? N provided by the zero crossing information calculation unit 323 is smaller than a second comparison value stored on the lookup table, i.e.,? N, while descending along the corresponding column of the selected Z _? (S607).

If it is determined that? N is smaller than the second comparison value, the controller 325 outputs the? _LUT corresponding to the current? N (S609).

The selected LAMBDA _LUT, for example, may be provided to the LLR symbol decoding unit 329 to be restored into digital data.

On the other hand, when the control unit 325 _{δ Z,} in step S603 _n is causing a departure from the scope of the first comparison value on the look-up table, on the look-up table _LUT Λ One of the maximum value and the minimum value can be selected and output (S611). This is shown in Equation (10). In the embodiment of the present invention, this is referred to as performing the first algorithm.

The controller 325 does not select the Λ _LUT when Δn provided by the zero crossing information calculator 323 in step S607 is larger than a second comparison value stored on the lookup table, g., located on the upper side or the lower side of the _LUT Λ Λ _LUT (Step S613). In the embodiment of the present invention, this is referred to as performing the second algorithm.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

The terms "include", "comprise", or "have" in the specification do not exclude other components, unless the context clearly indicates otherwise. But should be construed to include other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The embodiment of the present invention is applicable to a receiver based on a zero crossing demodulation and a driving method thereof. According to an embodiment of the present invention, a signal is demodulated using soft LLR values in signal demodulation of a wireless communication receiver, The performance of the system can be improved at the same time.

100: transmitting apparatus 110: receiving apparatus
300: Receive antenna 310: RF signal processor
311: LNA 313: Mixer
315: BPF 320: Demodulator
321: Zero crossing point detection unit 323: Zero crossing information calculation unit
323a: zero crossing number determination unit 323b: delta value summing unit
325: control unit 327: memory unit
329: LLR symbol decoding unit

Claims (11)

An RF signal processor for receiving an RF (Radio Frequency) signal and converting it into a channel frequency band signal and outputting the RF signal; and
Detecting a zero crossing point from the channel frequency band signal to extract a zero crossing number and a total time of the zero crossing number for any unit symbol (n) having information and storing the zero crossing number and the total time A demodulator for outputting a LLR (Log-likelihood Ratio) value for the channel frequency band signal which is matched with the comparison values and is matched
Zero-crossing demodulation-based receiver. The method according to claim 1,
The demodulation unit,
A zero crossing detection unit for detecting a zero crossing point from the channel frequency band signal;
A zero crossing number determiner for determining the number of zero crossings for the symbol (n) using detection information of the zero crossing point;
A delta value summation unit for extracting the total time using detection information of the zero crossing point;
A memory unit for storing the LLR values in a lookup table format; And
And a controller for selecting and outputting the LLR value corresponding to the number of zero crossings and the total time
Zero-crossing demodulation-based receiver. 3. The method of claim 2,
The demodulation unit may further include an LLR symbol decoding unit,
Wherein the LLR symbol decoding unit decodes the LLR value provided by the controller, converts the LLR value into digital data, and outputs the digital data. The method according to claim 1,
The LLR value is represented by a constant of Q bits, the range of the LLR value is [- 2 ^Q-1 + 1; 2 ^Q-1 - 1]. &Lt; / RTI &gt; The method according to claim 1,
Wherein the number of zero crossings associated with the arbitrary unit symbol (n) is different. A method for detecting a zero crossing point from a channel frequency band signal obtained by receiving an RF (Radio Frequency) signal and converting the detected zero crossing point to zero crossing counts for arbitrary unit symbols (n) having data information using the detection information of the zero crossing point, Calculating a total time of the zero crossing number;
Comparing the number of zero crossings with a first comparison value stored in the memory unit to determine whether the number of zero crossings is out of the range of the first comparison value;
Comparing the second comparison value stored in the memory unit with the total time according to the column of the first comparison value matched with the number of zero crossings when the number of zero crossings is not out of the range of the first comparison value Determining whether the total time is less than the second comparison value; And
And outputting a log-likelihood ratio (LLR) value matching the second comparison value if the total time is less than the second comparison value
Wherein the zero crossing demodulation based receiver is configured to receive the zero crossing demodulation based receiver. The method according to claim 6,
And outputting the LLR value comprises receiving the LLR value and decoding the LLR symbol and converting the LLR symbol to digital data. The method according to claim 6,
Wherein the first comparison value and the second comparison value include a number of zero crossings and total time information stored in the memory unit in the form of a look-up table, respectively. The method according to claim 6,
The step of determining whether the first comparison value is out of the range includes:
And outputs a maximum value or a minimum value of the LLR values when the number of zero crossings is out of the range of the first comparison value. The method according to claim 6,
Wherein determining whether the total time is less than the second comparison value comprises:
And outputs an LLR value that is one level higher or lower than an LLR value matched with the second comparison value if the total time is greater than the second comparison value. The method according to claim 1,
The demodulation unit,
Comparing the number of zero crossings with a previously stored first comparison value to determine whether the number of zero crossings is out of the range of the first comparison value; and if the number of zero crossings is not out of the range of the first comparison value, Comparing the second comparison value previously stored along the column of the first comparison value matched with the number of crossings with the total time to determine whether the total time is less than the second comparison value, And outputs an LLR value matching the second comparison value if the comparison value is smaller than the comparison value.

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