# Demodulation device and method for communication system using octic phase-keyed modulation

FIELD: radio engineering.

SUBSTANCE: demodulation device for octic phase-keyed signals receives input signal Rk(Xk, Yk) incorporating k quadrature component Yk and k cophasal component Xk and functions to generate L(sk, 0), L(sk, 1, and L(sk, 2) relaxed-solution values. Computer functions to calculate Zk by subtracting |Yk| level of quadrature signal component Yk from |Xk| level of cophasal signal component Xk. First selector chooses Zk for respective most significant bit of quadrature signal component Yk. Second selector chooses Zk for respective most significant bit of cophasal signal component Xk. Third selector is used to select output signal of second selector or "0" for respective most significant bit in Zk.

EFFECT: facilitated processing required in calculating minimal distance from signal received.

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The technical field

The present invention relates to a device and method of demodulation in a digital communication system using multi-level modulation, in particular to a device and method for the demodulation, to calculate a soft decision is required as input signals for the channel decoder to the demodulator for a digital communication system using a modulation 8-hex phase shift keying (FM).

Prior art

In a digital communication system using a modulation 8-ranks FM, representing a type of multilevel modulations used to increase spectral efficiency, the signal encoded channel encoder is transmitted after the implementation of its modulation. Then the demodulator demodulates the transmitted signal and outputs the demodulated signal to a channel decoder for decoding. Channel decoder performs decoding soft decision error correction. To accomplish this, the demodulator must have the logic to display to generate the values of the soft decision (soft values), the corresponding output bits of the channel encoder, from a two-dimensional signal comprising in-phase signal component and a quadrature signal component.

The algorithms display classified on the procedure simple metric, proposed to the companies Nokia, and procedure of the metric dual of the minimum proposed by Motorola. Both algorithms compute the logarithmic likelihood ratio (LLP) for the output bits, and use the calculated LLP as the input values of the soft decision channel decoder.

The procedure is simple metric that represents the algorithm of the display specified by modifying the formula of the complex calculations LLP, a simple approximate formula is a simple formula to calculate the LLP, but the distortion LLP, caused by the use of the approximate formula, leads to performance deterioration. The procedure is the metric dual of the minimum that represents the algorithm of the display to calculate LLP with a more accurate approximate formula using the calculated LLP as the input and the values of the soft decision channel decoder, may to some extent compensate for the deterioration in performance of the procedure simple metric. However, compared with the procedure simple metric this procedure requires more computation, which leads to a significant increase in the complexity of the hardware.

The invention

Therefore, the present invention is a device and method for facilitating the acquisition of input values of the soft decision channel decoder, the computed p is procedure metric double minimum, without the use of a table display or complex processing required to retrieve the value of the minimum distance to the received signal, a demodulator for a digital communication system using a modulation 8-ranks FM.

Also the present invention is a device and method for calculating values of the soft decision on a simple conditional formula in a digital communication system using a modulation 8-ranks FM.

To achieve these and other results, the proposed demodulation device 8 hex FM for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature component Y_{k}and k-th in-phase component X_{k}and to generate values Λ (s_{k,0}), Λ (s_{k,1}and Λ (s_{k,2}) soft decisions for the input signal R_{k}(X_{k},Y_{k}by using the soft decision. The device includes a calculator for calculating soft values of Z_{k}by subtracting the level |Y_{k}| quadrature signal component Y_{k}from level |X_{k}| in-phase signal component of X_{k}the received signal R_{k}(X_{k},Y_{k}) and output Z_{k}as the first value of the soft decision; a first selector for receiving Z_{k}from the solver and the inverted values of Z_{k}for Z_{k}and the choice of Z_{k}the if-Z_{
k}accordingly, the most significant bit (MSB) of the quadrature signal component of Y_{k}; a second selector for receiving Z_{k}from the solver and Z_{k}and the choice of Z_{k}or-Z_{k}accordingly, the MSB of the in-phase signal component of X_{k}; a third selector for receiving the output signal of the second selector and the value “0” and selecting the output signal of the second selector or “0” respectively, the MSB of the function Z_{k}; a first adder for summing the values calculated by multiplying the quadrature signal component of Y_{k}with the output value of the third selector, and outputting the resultant value as the third value of the soft decision; a fourth selector for receiving the output signal of the second selector and the value “0” and selecting the output signal of the second selector or “0” respectively, the MSB of the function Z_{k}; and a second adder for summing the values calculated by multiplying the in-phase signal component of X_{k}with the output of the fourth selector, and outputting the resultant value as the second value of the soft decision.

To achieve these and other findings, the authors proposed a method of demodulating 8-ranks FM for receiving the input signal R_{k}(X_{k},Y_{k}) contains the k-th quadrature component Y_{
k}and k-th in-phase component X_{k}and to generate values Λ (s_{k,0}), Λ (s_{k,1}and Λ (s_{k,2}) soft decisions for the input signal R_{k}(X_{k},Y_{k}by using the soft decision. The method includes the steps of: a) calculating soft values of Z_{k}the first demodulated symbol by subtracting the level |Y_{k}| quadrature signal component Y_{k}from level |X_{k}| in-phase signal component of X_{k}the received signal R_{k}(X_{k},Y_{k}a), (b) set the first variable α "0"if the soft value of Z_{k}has a positive value, setting the first variable α "-1"if the soft value of Z_{k}has a negative value and the quadrature component Y_{k}has a positive value, and setting the first variable α 1 if Z_{k}has a negative value and the quadrature component Y_{k}has a negative value, (C) determining a soft value of the third demodulated symbol by calculatingusing quadrature component Y_{k}soft values of Z_{k}and the first variable α ; d) set the second variable β "0"if the soft decision Z_{k}has a negative value, setting the second variable β -1, if Z_{k}
has a positive value and the in-phase component X_{k}has a negative value, and set the second variable β 1 if Z_{k}has a positive value and the in-phase component X_{k}has a positive value; e) determining a soft value of the second demodulated symbol by calculatingusing the in-phase component X_{k}soft values of Z_{k}and the second variable β .

Brief description of drawings

The above and other objectives, features and advantages of the present invention are explained in the following detailed description with reference to the drawings, which represent the following:

Figure 1 is a set of signals from the pixels of the display according to 8-ranks FM;

Figure 2 - calculation of the values of the soft decisions in a digital communication system that uses 8-ranks FM in accordance with a possible embodiment of the present invention;

Figure 3 - block diagram of the transmitter to determine the values of the soft decision for the demodulated symbols in accordance with a possible embodiment of the present invention;

4 is a logic diagram of the transmitter of values of mild solutions for use in a digital communication system that uses 8-ranks FM, and

5 is a set of signals from points C is agenia according to 8-ranks FM, for explanation of calculations.

A detailed description of the preferred option of carrying out the invention

The preferred implementation of the present invention is described below with reference to illustrative drawings. In the following description, well-known functions or constructions are not described in detail so as not to clutter the invention with unnecessary detail.

The present invention provides a method for computing multi-dimensional values of the soft decision is required as an input signal of the channel decoder of a two-dimensional received signal, using the procedure of the metric dual of the minimum.

The transmitter divides the output bitstream of the channel encoder to m-bit signal sequence and displays the signal sequence to the corresponding signal point of M(=2^{m}) signal points according to the encoding rule code gray. This can be represented as follows:

Equation (1)

In equation (1) s_{k,i}(i=0, 1,... ,m-1) denotes the i-th bit in the signal sequence shown on the k-th symbol, a I_{k}and Q_{k}denote in-phase (I) and quadrature (Q) signal components of the k-th symbol, respectively. For 8-ranks FM m=3, and the corresponding set of signals presented is a figure 1.
As shown in the drawing, a set of signals contains 8 (=2^{3}points display, and each point has a phase difference of 45° relative to neighboring pixels of the display.

As shown in figure 1, the symbol is displayed on the in-phase signal component I_{k}and quadrature signal component Q_{k}and transmitted to the receiver through the transmission medium. After receiving the in-phase signal component and a quadrature signal component of the receiver demodulates received signal components in the demodulator characters. The received signal corresponding to transmitted signal containing the in-phase signal component I_{k}and quadrature signal component Q_{k}can be expressed in complex entries according to the following equation (2), taking into account the gain and noise.

Equation (2)

In equation (2) X_{k}and Y_{k}denote the in-phase signal component and a quadrature signal component of a two-dimensional received signal displayed on the k-th symbol, respectively. In addition, g_{k}is a complex coefficient representing the coefficients of transmission of the transmitter, transmission medium and receiver. In addition,and- Gaussian noises with zero mean what value is and divergence
moreover, these noises are statistically independent from each other.

The demodulator of the characters in the receiver calculates LLP using the received signal R_{k}according to equation (2). The value LLP, corresponding to the i-th bit of s_{k,i}(i=0, 1,... ,m-1) in the output sequence of the channel encoder in the transmitter, can be calculated using equation (3), and the calculated value of the LLP is fed to the channel decoder in the receiver as the value of the soft decision.

Equation(3)

In equation (3) Λ (s_{k,i}) is an LLP or the value of the soft decision corresponding to s_{k,i}, k is a constant, Pr{A|B} is the conditional probability defined as the probability that event a will occur when the condition that caused the condition C. However, equation (3) is nonlinear, requiring relatively large calculations. It is therefore necessary to approximate equation (3) for the actual implementation. In the case of channels with Gaussian noise, with g_{k}=1 in equation (2) equation (3) can be written as follows.

Equation (4)

However, equation (4) is also nonlinear. Therefore, equation (4) can be approximated by the procedure of the metric dual of the minimum proposed by Motorola, in the following form:

Equation (5)

In equation (5) K'=(1/σ^{2})K and z_{k}(s_{k,i}=0) and z_{k}(s_{k,i}=1) indicate the actual values of I_{k}+jQ_{k}for s_{k,i}=0 and s_{k,i}=1, respectively. To compute equation (5), you must define z_{k}(s_{k,i}=0) and z_{k}(s_{k,i}=1) to minimize |R_{k}-z_{k}(s_{k,i}=0)|^{2}and |R_{k}-z_{k}(s_{k z}=1)|^{2}for two-dimensional received signal R_{k}.

Given n_{k,i}indicating the value of the i-th bit of the sequence for the signal point closest to R_{k}andindicates logical negation operation for n_{k,i}equation (5) can be rewritten in the following form:

Equation (6)

I.e. equation (6) can be calculated by determining whether the value is equal to n_{k,i}the i-th bit of the sequence for the signal point on the shortest distance from R_{k}the value "0" or "1", and determining the minimum value offor the value of the i-th bit of the restore sequence. The value calculated by equation (6), becomes the value of the soft decision values for the i-th bit of the restore sequence. As the value of the soft decision becomes more positive or negative value is Y.
the information presented on channel decoder becomes more correct.

Signal point on the shortest distance from R_{k}is determined by the ranges of values of the inphase signal component and the values of the quadrature signal component of R_{k}. So the first

term in brackets in equation (6) can be written as follows:

Equation (7)

In equation (7) U_{k}and V_{k}denote the in-phase signal component and a quadrature signal component of the signal point shown by n_{k}={n_{k,m-1},... ,n_{k,i},... ,n_{k,1}n_{k,0}} respectively.

In addition, the second term in brackets in equation (6) can be written in the following form:

Equation (8)

In equation (8) U_{k,i}and V_{k,i}denote the in-phase signal component and a quadrature signal component of the signal point shown by sequence recoveryfor z_{k}that minimizesrespectively. Equation (6) can be written as equation (9) using equations (7) and (8) in the following form:

Equation (9)

Λ (s_{k,i})=K'(2n_{k,i}-1)[{(X_{k}-U_{k})^{2}+(Y_{k}-V_{k})^{2}}-{(X_{k}-U_{k,i})^{2
+(Yk-Vk,i)2}]=}

=K'(2n_{k,i}-1)[(U_{k}+U_{k,i}-2X_{k})(U_{k}-U_{k,i})+(V_{k}+V_{k,i}-2Y_{k})(V_{k}-V_{k,i})]

From equation (9) can be calculated m values of the soft decisions are required as input values of the channel decoder that supports m-level modulation.

Below is described a method of calculating the input values of the soft decision for the channel decoder to the demodulator data transmission system that uses 8-ranks FM, according to equation (9).

First, use table 1 to calculate {n_{k,2}n_{k,1}n_{k,0}}, U_{k}V_{k}of the two signal components X_{k}and Y_{k}the modulated 8-ranks of the FM received signal R_{k}. Table 1 illustrates {n_{k,2}n_{k,1}n_{k,0}}, U_{k}and V_{k}for the case where the received signal R_{k}occurs in each of the 8 regions with centers in the signal points shown in figure 1. For convenience, in Table 1 omitted 4 boundary values, i.e. the resulting values for X_{k}=0, Y_{k}=0, Y_{k}=X_{k}, Y_{k}=-X_{k}.

In addition, table 2 illustrates the sequence {m_{k,2},m_{k,1},m_{k,0}}that minimizescalculated for i (where i∈ {0,1,2}), in terms of functions {n_{k,2}n_{k,1}n_{k,0}}and also illustreret in-phase and quadrature signal components U_{
k,i}and V_{k,i}the corresponding z_{k}.

Table 2 | |||

i | {m_{k,2},m_{k,i},m_{k,0}} | U_{k,i} | V_{k,i} |

2 | U_{k,2} | V_{k,2} | |

1 | U_{k,1} | V_{k,1} | |

0 | U_{k,0} | V_{k,0} |

Table 3 illustrates the U_{k,i}and V_{k,i}the corresponding {m_{k,2},m_{k,1},m_{k,0}}defined in Table 2 for all combinations of {n_{k,2}n_{k,1}n_{k,0}}.

Table 3 | ||||||

{n_{k,2}n_{k,1}n_{k,0}} | U_{k,2} | U_{k,1} | U_{k,0} | V_{k,2} | V_{k,1} | V_{k,0} |

{0,0,1} | cos(π /8) | -sin(π /8) | cos(π /8) | -sin(π /8) | cos(π /8) | sin(π /8) |

{0,0,0} | cos(π /8) | -sin(π /8) | sin(π /8) | -sinπ /8) | cos(π /8) | cos(π /8) |

{0,1,0} | -cos(π /8) | sin(π /8) | -sin(π /8) | -sin(π /8) | cos(π /8) | cos(π /8) |

{0,1,1} | -cos(π /8) | sin(π /8) | -cos(π /8) | -sin(π /8) | cos(π /8) | sin(π /8) |

{1,1,1} | -cos(π /8) | sin(π /8) | -cos(π /8) | sin(π /8) | -cos(π /8) | -sin(π /8) |

{1,1,0} | -cos(π /8) | sin(π /8) | -sin(π /8) | sin(π /8) | -cos(π /8) | -cos(π /8) |

{1,0,0} | cos(π /8) | -sin(π /8) | sin(π /8) | sin(π /8) | -cos(π /8) | -cos(π /8) |

{1,0,1} | cos(π /8) | -sin(π /8) | cos(π /8) | sin(π /8) | -cos(π /8) | -sin(π /8) |

Table 4 illustrates the results obtained by scaling with a decrease in the relationfor values of soft decisions obtained by substituting U_{k,i}and V_{k,i}from Table 3 into equation (9), i.e. illustri is the duty to regulate the results
normalized byI.e. when applied signal R_{k}it can be defined LLR satisfying the appropriate condition, as the value of the soft decision Table 4. If the channel decoder used in the system, is not a decoder logarithmic maximum a posteriori probability, it must be added to the process of scaling with increasing LLR Table 4 in reverse relation to the scale to decrease.

However, when performing demodulation soft solutions 8-ranks FM using Table 4, the demodulator must first perform an operation condition determination, including the division operation, the two components of the received signal. After that, the demodulator selects the formula corresponding to the result of the operation condition determination among the formulas specified conditions respectively, and supplies the two components of a received signal in the selected formula, thereby calculating the values of the soft decision. To this end, the demodulator requires the operator to perform a division operation and a memory for storing various formulas, corresponding to the condition.

To avoid the division operation and eliminate the need for memory, you need to modify the formula to determine the services the via and formula calculating the value of the soft decision
so you can use them the same way even to different conditions. With this purpose, the formula to determine the conditions shown in Table 4, can be expressed as shown in Table 5, using the new function, Z_{k}defined as |X_{k}|-|Y_{k}|. In Table 5 of the division operation is eliminated, and the values of the soft decision for 4 boundary values, which for convenience have been omitted in Table 4, here taken into account.

In the implementation of a hardware-based table 5 can be simplified in Table 6, provided that X_{k}, Y_{k}and Z_{k}can be expressed by the most significant bit (MSB or sign bit. In Table 6 MSB(x) denotes the most significant bit of this value X.

From Table 6 the values of the soft decision Λ (s_{k,2}), Λ (s_{k,1}and Λ (s_{k,0}for each i is expressed as follows:

Equation (10)

In equation (10) parameter α 0 for MSB(Z_{k})=0; -1 MSB(Z_{k})=1 and MSB(Y_{k})=0; and 1 for the MSB(Z_{k})=1 and MSB(Y_{k})=1.

Equation (11)

In equation (11) the parameter β 0 for MSB(Z_{k})=1; -1 MSB(Z_{k})=0 and MSB(X_{k})=1; and 1 for the MSB(Z_{k})=0 and MSB(X_{k})=0.

Equation (12)

Λ
(S_{k,0})=Z_{k}

I.e. in a digital communication system that uses 8-ranks FM, it is possible to really calculate 3 values soft solutions, which are output signals of the demodulator for a single received signal or the input signal of the channel decoder, using the procedures of the metric dual of the minimum in equation (4)by simple computational formulas according to equations (10)-(12). This process is illustrated in figure 2.

Figure 2 shows the procedure to calculate the values of the soft decision in a digital communication system that uses 8-ranks FM according to a possible variant of implementation of the present invention. According to figure 2 in step S110 demodulator characters computes Z_{k}=|X_{k}|-|Y_{k}| to determine the formulas that determine the conditions shown in Table 4 as a new feature. The demodulator characters analyzes the MSB for Z_{k}at the step S120 to determine α and β in accordance with the MSB at Z_{k}in equations (1)-(12). The analysis at step S120, if the MSB in the Z_{k}"0", the demodulator of the characters goes to step S130, and otherwise, goes to step S140. At step S130, the demodulator characters analyzes MSB in X_{k}. The analysis at step S130, if the MSB in X_{k}equal to "1", then the demodulator characters sets the parameter α to "0" and β "-1" at step S150. If the MSB is X_{
k}equal to "0", then the demodulator characters sets the parameter α to "0" and β "1" at step S160.

The analysis at step S120, if the MSB in the Z_{k}equal to "1", the demodulator of the characters on the stage S140 analyzes MSB Y_{k}. The analysis at step S140, if the MSB in Y_{k}equal to "0", then the demodulator characters sets the parameter α -1 and β to "0" at step S170. If the MSB in Y_{k}equal to "1", then the demodulator characters sets the parameter α to "1" and the parameter β to "0" at step S180. After that, at step S190, the demodulator characters calculates the values of the soft decision by substitution parameters α and β defined in the previous steps, and the received signal in equation (10)-(12). This way you demodulation symbols.

Thus, the process of computing the values of the soft decision on the procedure of the metric dual of at least includes a first step of determining the first parameter α and the second parameter β by analyzing the two-dimensional received signal containing the in-phase component and quadrature component, and a second step of calculating the values of the soft decision using a two-dimensional received signal and the first parameter α and the second parameter β defined at the first stage. The obtained values of the soft decision demodulated symbol serves on the canal the first decoder.

Figure 3 shows the transmitter to determine the values of the soft decision demodulated symbol, respectively, a possible variant of implementation of the present invention. According to figure 3 the evaluator to determine the values of the soft decision on the procedure of the metric dual of the minimum in the digital communication system includes an analyzer 10 of the received signal and the block 20 of issuance of the values of the soft decision. The analyzer 10 received signal specifies the first parameter α and the second parameter β by analyzing the two-dimensional received signal containing the in-phase signal component of X_{k}and quadrature signal component Y_{k}. The block 20 of issuance of the values of the soft decision then calculates the values of the soft decision Λ (s_{k,2}), Λ (s_{k,1}and Λ (S_{k,0}required for decoding the soft decision using the received signal and the specified parameters α and β .

Logic calculator for calculating soft values of the decision in accordance with equations (10)-(12) is shown in figure 4. In particular, figure 4 shows the transmitter values soft solutions for use in a digital communication system that uses 8-ranks FM. Logic diagram in figure 4 is included in the demodulator of a digital communication system that uses 8-ranks FM, and calculates the values of the soft decision using the EQ is tions (10)-(12).
Here a two-dimensional received signal R_{k}, the in-phase signal component of X_{k}and quadrature signal component Y_{k}the variable Z_{k}parameter α and β all are real numbers and a digital value with sign bit. Figure 4 the transmitter 105, the inverter 115, a first block 155 selection MSB, the first selector 110, the third block 165 selection MSB and the third selector 120 to form the structure for determining the first parameter α . In addition, the transmitter 105, the inverter 115, the second block 160 selection MSB, the second selector 135, the third block 165 selection MSB and the fourth selector 140 to form the structure for determining the parameter β .

In accordance with figure 4, the calculator 105 calculates Z_{k}=|X_{k}|-|Y_{k}| using the in-phase signal component of X_{k}and quadrature signal component Y_{k}two-dimensional received signal R_{k}displayed on the k-th symbol. The inverter 115 inverts the sign of Z_{k}by multiplying Z_{k}with the transmitter 105 to "-1". The first block 155 selection MSB selects the MSB of the received Y_{k}and outputs the selected MSB to the first selector 110 as the first selected signal. The second block 160 selection MSB selects the MSB of the received X_{k}and outputs the selected MSB to the second selector 135 as a second selected signal. The third block 165 selection MSB selects MSB Z_{
taken from a transmitter 105, and outputs the selected MSB to the third selector 120 as the third selected signal. In addition, Ykmultiplied byin the first multiplier 130 and Xkalso is multiplied byin the second multiplier 150.}

The first selector 110 receives Z_{k}from the transmitter 105 and a-Z_{k}from the inverter 115, and selects one of these input signals respectively to the first selected signal from the first block 155 selection MSB. A third selector 120 then receives the output signal of the first selector 110 and the bit "0" and selects one of the input signals respectively selected third signal from the third block 165 selection MSB. The output signal of the third selector 120 is summed with the output value ofthe first multiplier 130 via the first adder 125, forming a third value of the soft decision Λ (S_{k,2}) received signal R_{k}displayed on the k-th symbol.

In addition, the second selector 135 accepts Z_{k}from the transmitter 105 and a-Z_{k}from the inverter 115, and selects one of these input signals, respectively, the second selected signal with the second unit 160 selection MSB. The fourth selector 140 then receives the output signal of the second selector 135 and bit "0" and selects one of these input signals, respectively freemobilegame signal from the third block 165 selection MSB.
The output signal of the fourth selector 140 is summed with the output value ofthe second multiplier 150 through the second adder 145, forming the second value of the soft decision Λ (s_{k,1}) received signal R_{k}displayed on the k-th symbol.

The output value of Z_{k}transmitter 105 becomes the first value of the soft decision Λ (s_{k,0}) received signal R_{k}displayed on the k-th symbol.

In accordance with the previous description normal calculator value soft decision using the procedure metric double minimum, sold by the equation (5), requires ten or more operations of squaring and comparison. However, the new evaluator on figure 4, is implemented using equations (10)-(12), contains three adder 3 multiplier and 4 multiplexer, which contributes to considerable reduction in time and complexity of the transmitter. Table 7 illustrates the comparison between equation (5) and equations (10)-(12) in terms of the type and number of operations i∈ {0,1,2}.

tr>Table 7 | |||

Equation (4) | Equations (10)-(12) | ||

Operation | Number of operations | Operation | Number of operations |

Summation | 3× 8+3=27 | Summation | 3 |

Squaring | 2× 8=16 | Multiplication | 3 |

Comparison | 3× 2× 3=18 | A mul replacerange | 4 |

Below a comparison between the usual way of calculating the value of the Λ (s_{k,2}) using equations (5) and the new method of calculating the value of the Λ (s_{k,2}) using equation (10). Figure 5 shows a set of signals with the point of display, respectively, 8-ranks FM, for explanation of calculations. According to figure 5 two-dimensional received signal R_{k}containing in-phase signal component of X_{k}and quadrature signal component Y_{k}has a coordinate value is represented by "x". Here it is assumed that X_{k}=and-0.6 and Y_{k}=-0,1.

First describe the normal process of calculating the value of the Λ (s_{k,2}) using equation (5).

To determine the shortest distance first, calculate the square of each of distances between the received signal R_{k}and 4 showing the points in s_{k,2}=1 (i.e. 4 showing the points below the x-axis in figure 5).

The square of the distance from the reflecting point “110”={minus 0.6-cos(9π /8)}^{2}+{-0,1-sin(9π /8)}^{2}=0,185

^{2}+{-0,1-sin(11π /8)}

^{2}=0,726

The square of the distance from the reflecting point “101”={minus 0.6-cos(13π /8)}^{2}+{-0,1-sin(13π /8)}^{2}=1,644

The square of the distance from the reflecting point “100”={minus 0.6-cos(15π /8)}^{2}+{-0,1-sin(15π /8)}^{2}=2,402

Therefore, the minimum value (or the shortest distance from the received signal R_{k}) |R_{k}-z_{k}(s_{k,2}=1)|^{2}well 0,185.

Then to determine the shortest distance first, calculate the square of each of distances between the received signal R_{k}and 4 showing the points in s_{k,2}=0 (i.e., 4 showing the points above the x-axis in figure 5).

The square of the distance from the reflecting point "000"={minus 0.6-cos(π /8)}^{2}+{-0,1-sin(π /8)}^{2}=2,555

The square of the distance from the reflecting point "001"={minus 0.6-cos(3π /8)}^{2}+{-0,1-sin(3π /8)}^{2}=2,014

The square of the distance from the reflecting point "011"={minus 0.6-cos(5π /8)}^{2}+{-0,1-sin(5π /8)}^{2}=1,096

The square of the distance from the reflecting point “010”={minus 0.6-cos(7π /8)}^{2}+{-0,1-sin(7π /8)}^{2}=0,338

Therefore, the minimum value of |R_{k}-z_{k}(s_{k,2}=1)|^{2}well 0,338.

If the results obtained above to substitute in equation (5), the value of the soft decision is received as a

Next described is a new process vicis the possible values Λ
(s_{k,2}) using equation (10).

First calculate Z_{k}and α .

Z_{k}=|X_{k}|-|Y_{k}|=|-0,6|-|-0,1|=0,5

Hence, since Z_{k}≥_{}0, i.e. the MSB(Z_{k})=0, α =0.

If the above results are substituted into equation (10), the value of the soft decision would be:

The fact that the result of equation (5) differs from the equation (10), due to the fact that the value of the soft decision, calculated according to equation (9), was normalized byIn the case of turbolader using the kernel maximum logarithmic posteriori probability (currently as L3QS and 1× TREME using the engine maximum logarithmic posteriori probability) normalization of all values LLP (or soft values) using the same factor never affect performance.

If a certain factor, in fact, is multiplied to compute the non-normalized values, then

It should be noted that the calculated normalized value is identical to the result of equation (5).

Thus, in order to reduce the time delay and the complexity caused by the use of procedures for the metric dual of the minimum in equation (5), we shall Aasee the invention provides for the transmission of the tables display (Tables 4-6) through the process in equations (6)-(9) and Tables 1-3. In addition, the present invention provides for the substitution of tables displayed in equations (10)-(12), representing formulas that implement the procedure of the metric dual of the minimum. In addition, the present invention provides a logic circuit calculator for calculating soft values of the 8-ranks FM, implemented according to the equations(10)-(12).

As described above, when obtaining the values of the soft decision required as input to the channel decoder in the procedure metric double minimum, new demodulator for a digital communication system using a modulation by 8-ranks FM, provides a simple and fast calculations, greatly contributing to the reduction of working time and the complexity of the demodulator, which calculates the values of the soft decision.

Although the invention is shown and described with reference to its preferred variant implementation, it should be borne in mind that specialists in this field of technology can be made various changes in form and details without deviating from the essence and scope of the invention as presented in the claims.

1. The device demodulation of the 8-hex phase-shift keying (FM) for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature component Y_{k}and k-th in-phase component X_{k}and degenerative values Λ
(s_{k,0}), Λ(s_{k,1}and Λ(s_{k,2}) soft decisions for the input signal R_{k}(X_{k},Y_{k}by using the soft decision containing the analyzer received signal to calculate the functions Z_{k}the input signal R_{k}(X_{k},Y_{k}according to the equation Z_{k}=|X_{k}|-|Y_{k}| and the definition of the first parameter α and the second parameter β through the input signal and block the issuance of mild solutions to calculate the values of the soft decision for the input signal R_{k}(X_{k},Y_{k}) using the first parameter α and the second parameter β and a received signal R_{k}(X_{k},Y_{k}in accordance with

Λ(s_{k,0})=Z_{k}

where Λ(s_{k,i}indicates the value of the soft decision corresponding to s_{k,i}(i=0, 1, 2), and s_{k,i}indicates the i-th bit in the sequence of the encoded signal that is displayed on the k-th symbol.

2. Method demodulate 8-hex phase-shift keying (FM) for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature component Y_{k}and k-th in-phase component X_{k}and to generate values Λ(s_{k,0}), Λ(s_{k,1}and Λ(s_{k,2}) soft decisions for the input signal R_{k}
(X_{k},Y_{k}by using the soft decisions, including the steps of calculating soft values of Z_{k}the input signal R_{k}(X_{k},Y_{k}according to the equation Z_{k}=|X_{k}|-|Y_{k}| and the definition of the first parameter α and the second parameter β through the input signal and calculate a soft decision for the input signal R_{k}(X_{k},Y_{k}) using the first parameter α and the second parameter β and a received signal R_{k}(X_{k},Y_{k}in accordance with

Λ(s_{k,0})=Z_{k}

where Λ(s_{k,i}indicates the value of the soft decision corresponding to s_{k,i}(i=0, 1, 2), and s_{k,i}indicates the i-th bit in the sequence of the encoded signal that is displayed on the k-th symbol.

3. The device demodulation of the 8-ranks FM for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature component Y_{k}and k-th in-phase component X_{k}and to generate values Λ(s_{k,0}), Λ(s_{k,1}and Λ(s_{k,2}) soft decisions for the input signal R_{k}(X_{k},Y_{k}by using the soft decision containing a calculator for calculating soft values of Z_{k}by subtracting the level |Y_{k}| uadrature signal component Y_{
k}from level |X_{k}| in-phase signal component of X_{k}the received signal R_{k}(X_{k},Y_{k}) and output Z_{k}as the first value of the soft decision;

the first selector for receiving Z_{k}from the solver and the inverted values of Z_{k}regarding Z_{k}and the choice of Z_{k}or-Z_{k}accordingly, the most significant bit (MSB) of the quadrature signal component of Y_{k};

a second selector for receiving Z_{k}from the solver and Z_{k}and the choice of Z_{k}or-Z_{k}accordingly, the MSB of the in-phase signal component of X_{k};

a third selector for receiving the output signal of the second selector and the value "0" and selecting the output signal of the second selector or "0" respectively MSB in Z_{k};

a first adder for summing the values calculated by multiplying the quadrature signal component of Y_{k}with the output value of the third selector, and outputting the resultant value as the third value of the soft decision;

a fourth selector for receiving the output signal of the second selector and the value "0" and selecting the output signal of the second selector or "0" respectively MSB in Z_{k}; and

a second adder for summing the values calculated by cleverly is placed in-phase signal component of X_{
k}with the output of the fourth selector, and outputting the resultant value as the second value of the soft decision.

4. Method demodulate 8-ranks FM for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature component Y_{k}and k-th in-phase component X_{k}and to generate values Λ(Λ_{k,0}), Λ(Λ_{k,1}and Λ(Λ_{k,2}) soft decisions for the input signal R_{k}(X_{k},Y_{k}by using the soft decisions, including the steps:

a) calculating soft values of Z_{k}the first demodulated symbol by subtracting the level |Y_{k}| quadrature signal component Y_{k}from level |X_{k}| in-phase signal component of X_{k}the received signal R_{k}(X_{k},Y_{k}),

b) set the first variable α "0"if the soft value of Z_{k}has a positive value, setting the first variable α -1, if Z_{k}has a negative value and the quadrature component Y_{k}has a positive value, and setting the first variable α 1 if Z_{k}has a negative value and the quadrature component Y_{k}has a negative value,

C) determining a soft value of the third dem is dublirovannoe symbol by calculating
using quadrature component Y_{k}soft values of Z_{k}and the first variable α;

d) installing a second variable β "0"if the soft decision Z_{k}has a negative value, setting the second variable β -1, if Z_{k}has a positive value and the in-phase component X_{k}has a negative value, and set the second variable β 1 if Z_{k}has a positive value and the in-phase component X_{k}has a positive value;

e) determining a soft value of the second demodulated symbol by calculatingusing the in-phase component X_{k}soft values of Z_{k}and the second variable β.

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