# Device and method for demodulation in communication system, using hexadecimal quadrature amplitude modulation

FIELD: radio engineering.

SUBSTANCE: first calculator calculates soft value Λ of third demodulated symbol of 4 demodulated symbols by subtraction of distance 2a between two demodulated symbols of same axis of indication table from level , quadrature component Y_{k}. Second calculator determines soft value Λ of fourth demodulated symbol by calculating using first variable α. Third calculator calculates soft value Λ of first demodulated signal by subtraction of distance 2a from level of common-mode component X_{k}. Fourth calculator determines soft value Λ of second demodulated symbol by calculating using second variable β.

EFFECT: higher efficiency.

5 cl, 14 dwg, 12 tbl

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 channel decoder to the demodulator for a digital communication system using a 16-hexadecimal quadrature amplitude modulation (QAM).

Prior art

In a digital communication system, when a signal encoded in a channel encoder, is modulated using 16-hexadecimal QAM, which represents a typical multi-level modulation to increase spectral efficiency, the demodulator in the receiver requires the use of the algorithm of the 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 to a channel decoder in the receiver was decoding the modulated signal by decoding the soft decision.

The algorithms display classified on the procedure simple metric, proposed by Nokia and 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 is the quality of 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 values of the soft decision channel decoder, may to some extent compensate for the deterioration of the operating characteristics inherent in 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, calculated by the procedure of the metric dual of the minimum, without using 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 that uses 16-R is know CAM.

To achieve these and other findings, the authors proposed a method of demodulating a received signal in a data transmission system that uses a modulation technique for separating the output sequence of the channel encoder 4 bits and the mapping of bits in a particular one of the 16 signal points having a common mode component of X_{k}and the quadrature component Y_{k}. The method includes the steps of calculating soft values of Z_{k}the third demodulated symbol by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the level |Y_{k}| quadrature signal component Y_{k}; set the first variable α "0"if the soft value of Z_{k}has a negative value, setting the first variable α ″ 1″ , if Z_{k}has a positive value and the quadrature component Y_{k}has a negative value, and set the first variable α 1 if Z_{k}has a positive value and the quadrature component Y_{k}has a positive value; determining a soft value of the fourth demodulated symbol by calculating Y_{k}+α *Z_{k}using quadrature component Y_{k}soft values of Z_{k}and the first variable α ; calculating soft values of Z'_{k
the first demodulated symbol by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the level |Xk| in-phase signal component of Xk; set the second variable β "0"if the soft decision Z'khas a negative value, setting the second variable β -1, if Z'khas a positive value and the in-phase component Xkhas a negative value, and set the second variable β on ″ 1 if Z'khas a positive value and the in-phase component Xkhas a positive value; and determining a soft value of the second demodulated symbol by calculating Xk+β *Z’kusing the in-phase component Xksoft Z'kand 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 - diagram of the set of signals for a 16-hexadecimal QAM;

Figure 2 - calculation of the values of the soft decision 4 demodulated symbols at the input of the channel decoder in a digital communication system using a 16-hexadecimal QAM in accordance with zmeinym of the embodiment of the present invention;

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

Figure 4 - demodulator characters to determine the values of the soft decision channel decoder in a digital communication system using a 16-hexadecimal QAM, in accordance with a possible embodiment of the present invention.

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 of obtaining the input soft values of the channel decoder using the procedures of the metric dual of the minimum without the use of a table display or complex calculations in a demodulator for a data transmission system using 16-hexadecimal QAM.

The following describes the algorithm for generating multidimensional soft values from a two-dimensional received signal. The output sequence of a binary channel encoder is divided into m bits, and appears to correspond to the s 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 output sequence of a binary channel encoder, shown on the k-th symbol, a I_{k}and Q_{k}denote in-phase and quadrature signal components of the k-th symbol, respectively. For 16-hexadecimal QAM m=4 and the corresponding set of signals presented in figure 1. As shown in the drawing, a set of signals contains 16 signal points, each quadrant contains 4 signal points.

Each signal point is expressed by 4 characters. For example, in figure 1 the first quadrant is divided into 4 areas; the upper-right pane is displayed on the character stream "0000", the lower right region is displayed on a character stream "0100", left top area appears in the character stream "0001" and the lower left region is displayed on a character stream "0101".

The integrated output signal of the demodulator of characters in the receiver, containing the in-phase signal component I_{k}and quadrature signal component Q_{k}, is defined as follows:

Equation (2)

In equation (2) X_{k}and Y_{k}denote the phase signaline the component and the quadrature signal component of the output signal of the demodulator characters, respectively.
In addition, g_{k}is a complex coefficient representing the coefficients of transmission of the transmitter, transmission medium and receiver. In addition, η^{I} _{k}and η^{Q} _{k}- Gaussian noises with zero mean value and divergence σ^{2} _{n}and these noises are statistically independent from each other.

The value of the LLP, the corresponding sequence s_{k,i}(i=0,1,...,m-1), can be calculated using equation (3), and the calculated value of the LLP can be used as the value of soft decisions supplied to the channel decoder.

Equation (3)

In equation (3) Λ (s_{k,i}) is the value of the soft decision, K - 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, because equation (3) is nonlinear and requires a relatively large computing needs an algorithm for approximation of 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)

In equation (4) K'=(1/σ_{n} ^{2}) And z_{k}(s_{
,i=0) and Zk(sk,i=1) denote the actual values of Ik+jQkfor sk,i=0 and sk,i=1, respectively. To calculate equation (4), you must define zk(sk,i=0) and zk(sk,i=1) by minimizing |Rk-zk(sk,i=0)|2and |Rk-zk(sk,i=1)|2for two-dimensional received signal R2.}

Equation (4), approximated by means of the procedure of the metric dual of the minimum can be rewritten in the following form:

Equation (5)

In equation (5) n_{k,i}indicates the value of the i-th bit of the sequence for the signal point closest to R_{k}andindicates the negation of n_{k,i}. The nearest signal point is determined by the ranges of values of the inphase signal component and the values of the quadrature signal component of R_{k}. The first term in brackets in equation (5) can be written as follows:

Equation (6)

In equation (6) 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 the brackets in equation (5) can be written in the following form:

Equation (7)

In equation (7) U_{k,i}and V_{k,i}denote the in-phase signal component and a quadrature signal component of the signal point shown by the sequence {m_{k,m-1},... ,m_{k,i},... m_{k,1},m_{k,0}} for z_{k}minimize |R_{k}-Z_{k}(s_{k,i}=)|^{2}respectively. Equation (5) is rewritten as equation (8) using equations (6) and (7).

Equation (8)

Below is described a method of calculating the input values of the soft decision for the channel decoder to the demodulator communication system using a 16-hexadecimal QAM. First, use table 1 and table 2 to calculate {n_{k,3}n_{k,2}n_{k,1}n_{k,0}}, U_{k}V_{k}of the two signal components X_{k}and Y_{k}modulated 16-hexadecimal QAM received signal R_{k}. Table 1 illustrates {n_{k,3}n_{k,2}and V_{k}for the case where the quadrature signal component of Y_{k}the received signal R_{k}occurs in each of the 4 areas parallel to the horizontal axis in figure 1. For convenience, in Table 1 omitted 3 boundary values, i.e. the resulting values for Y_{k}=-2a, Y_{k}=0 and Y_{k}=2a. Table 2 illustrare the {n_{
k,1}n_{k,0}and U_{k}for the case where the in-phase signal component of X_{k}the received signal R_{k}occurs in each of the 4 areas parallel to the vertical axis in figure 1. For convenience, in Table 2 omitted 3 boundary values, i.e. the resulting values for X_{k}=-2a, X_{k}=0 and X_{k}=2a.

Table 1 | ||

The condition for Y_{k} | (n_{k,3}n_{k,2}) | V_{k} |

Y_{k}>2a | (0,0) | 3A |

0<Y_{k}<2a | (0,1) | and |

-2a<Y_{k}<0 | (1,1) | -and |

Y_{k}<-2a | (1,0) | -3A |

Table 2 | ||

The condition for X_{k} | (n_{k,1}n_{k,0}) | U_{k} |

X_{k}>2a | (0,0) | 3A |

0<X_{k}<2a | (0,1) | and |

-2a<X_{k}<0 | (1,1) | -and |

X_{k}<-2a | (1,0) | -3A |

Table 3 illustrates the sequence {m_{k,3}, m_{k,2}, m_{k,1}, m_{k,0}}, min is Misirlou |R_{
k}-z_{k}(S_{k,i}=)|^{2}calculated for i (where i∈ {0,1,2,3}, in terms of functions {n_{k,3}n_{k,2}n_{k,1}n_{k,0}}and also illustrates in-phase and quadrature signal components U_{k,i}And V_{k,i}the corresponding z_{k}.

Table 3 | |||

i | {m_{k,3}, m_{k,2}, m_{k,1}, m_{k,0}} | V_{k,i} | U_{k,i} |

3 | {, 1, n_{k,1}n_{k,0}} | V_{k,3} | U_{k} |

2 | {n_{k,3},n_{k,1}n_{k,0}} | V_{k,2} | U_{k} |

1 | {n_{k,3}n_{k,2},n_{k,0}} | V_{k} | U_{k,i} |

0 | {n_{k,3}n_{k,2}n_{k,1}} | V_{k} | U_{k,0} |

Table 4 and table 5 show the V_{k,i}and U_{k,i}the corresponding (m_{k,3}, m_{k,2}) and (m_{k,1},m_{k,0}calculated in Table 3 for all combinations (n_{k,3}n_{k,2}) and (n_{k,1}n_{k,0}).

(n_{k,3}n_{k,2}) | V_{k,3} | V_{k,2} |

(0,0) | -and | a |

(0,1) | -and | 3A |

(1,1) | and | -3A |

(1,0) | and | -and |

Table 5 | ||

(n_{k,1}n_{k,0}) | U_{k,i} | U_{k,0} |

(0,0) | -a | a |

(0,1) | -and | 3A |

(1,1) | and | -3A |

(1,0) | and | -and |

Table 6 and table 7 illustrate the results obtained by scaling with the decrease in the ratio K ha for soft values of the solutions obtained by substituting V_{k,i}and U_{k,i}from Table 4 and Table 5 in equation (8). I.e. when applied signal R_{k}it can be defined LLR satisfying the corresponding condition as the value of the soft decision according to Table 6 and Table 7. If the channel decoder used in the system, is not a logarithmic decoder maximum aposterior the second probability,
it should be added to the process of scaling with increasing LLR Table 6 and Table 7 in reverse relation to the scale to decrease.

Table 6 | ||

The condition for Y_{k} | Λ(s_{k,3}) | Λ(s_{k,2}) |

Y_{k}>2a | 2Y_{k}-2a | Y_{k}-2a |

0<Y_{k}<2a | Y_{k} | Y_{k}-2a |

-2a<Y_{k}<0 | Y_{k} | -Y_{k}-2a |

Y_{k}<-2a | 2Y_{k}+2a | -Y_{k}-2a |

Table 7 | ||

The condition for X_{k} | Λ(s_{k,1}) | Λ(s_{k,0}) |

X_{k}>2a | 2X_{k}-2a | X_{k}-2a |

0<X_{k}<2a | X_{k} | X_{k}-2a |

-2a<X_{k}<0 | X_{k} | -X_{k}-2a |

X_{k}<-2a | 2X_{k}+2a | -X_{k}-2a |

However, when the input soft values of the channel decoder using Tables 6 and 7 display demodulate is, unfortunately, I have to first perform the operation of determining the conditions for the received signal and requires memory for storing the output of the content according to the corresponding condition. Such shortcomings can be overcome by calculating the values of the soft decision channel decoder using a formula expressing a simple operation condition determination instead of table display.

With this purpose, the formula to determine the conditions shown in Tables 6 and 7, can be expressed as shown in Tables 8 and 9. In Table 8 Z_{k}=|Y_{k}|-2a and in Table 9 Z'_{k}=|X_{k}|-2a. In Tables 8 and 9 taken into account even soft value 3 limit values, which were omitted in Tables 6 and 7 for convenience.

Table 8 | |||

The condition for Y_{k} | The condition for Z_{k} | Λ (s_{k,3}) | Λ (s_{k,2}) |

Y_{k}>0 | Z_{k}>0 | Y_{k}+(Y_{k}-2a) | Y_{k}-2a |

Z_{k}<0 | Y_{k} | Y_{k}-2a | |

Y_{k}<0 | Z_{k}>0 | Y_{k}-(-Y_{k}-2a) | -Y_{k}-2a |

Z_{k}<0 | Y_{k} | -Y |

Table 9 | |||

The condition for X_{k} | The condition for Z'_{k} | Λ (s_{k,1}) | Λ (s_{k,0}) |

X_{k}≥_{}o | Z'_{k}≥_{}0 | X_{k}+(X_{k}-2a) | X_{k}-2a |

Z'_{k}<0 | X_{k} | X_{k}-2a | |

X_{k}<0 | Z'_{k}≥_{}0 | X_{k}-(-X_{k}-2a) | -X_{k}-2a |

Z'_{k}<0 | X_{k} | -X_{k}-2a |

In the implementation of a hardware-based Tables 8 and 9 can be simplified in the form of Tables 10 and 11, provided that X_{k}, Y_{k}, Z_{k}and Z'_{k}can be expressed through significant bits. In Tables 10 and 11 MSB(x) denotes the most significant bit (MSB) of the given values of X.

Table 10 | |||

MSB(Y_{k}) | MSB(Z_{k}) | Λ (s_{k,3}) | Λ (s_{k,2}) |

0 | 0 | Y_{k}+Z_{k} | Z_{k} |

1 | Y_{k} | Z_{k} | |

1 | about | Y_{k}-Z_{k} | Z_{k} |

1 | Y_{k} | Z_{k} |

Table 11 | |||

MSB(X_{k}) | MSB (Z'_{k}) | Λ (s_{k,i}) | Λ (s_{k,o}) |

0 | 0 | X_{k}+Z'_{k} | Z'_{k} |

1 | X_{k} | Z'_{k} | |

1 | 0 | X_{k}-Z'_{k} | Z'_{k} |

1 | X_{k} | Z'_{k} |

From Table 10 the values of the soft decision Λ (s_{k,3}and Λ (s_{k,2}for i=3 and i=2 are expressed as follows:

Equation (9)

From Table 11, the values of the soft decision Λ (s_{k,1}and Λ (s_{k,0}for i=1 and 1=0 can be expressed as follows:

Equation (10)

I.e. in a digital communication system, and the use of 16-hexadecimal QAM, it is indeed possible to calculate the values of the soft decisions, 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 (9) and (10). 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 using a 16-hexadecimal QAM according to a possible variant of implementation of the present invention. According to figure 2 the process of determining the soft decision through the procedures of the metric dual of the minimum can be subdivided into the first stage of the definition of α by analyzing the quadrature signal component and the values "a" and the definition of β by analyzing the in-phase signal component and the values "a" and the second stage of issuing soft values defined by the values α and β obtained at the first stage. The operation, described below, may be performed, for example, the demodulator of the characters in the receiver.

According to figure 2 on the phase demodulator 201 characters computes Z_{k}=|Y_{k}|-2a using a two-dimensional received signal R_{k}consisting of in-phase component X_{k}and quadrature component Y_{k}and the distance 2A between the two demodulated symbols on the same axis in the grid display.
Here Z_{k},Y_{k}X_{k}and "a" are real numbers. The demodulator of the characters on the stage 203 determines whether the resulting value calculated by the above formulas, a positive value. For example, Z_{k}, Y_{k}X_{k}and "a" is expressed by a numerical value, including the sign bit. Therefore, at step 203 demodulator symbol determines whether the MSB (or sign bit) of the result value is equal to "0". If the MSB is equal to "0", the demodulator of the characters goes to step 205. Otherwise, the demodulator of the characters goes to step 209, where he sets the parameter α to "0". At step 205 demodulator symbol determines whether the quadrature component Y_{k}a positive value, i.e. determines whether the MSB in Y_{k}a value of "0". If Y_{k}has a positive value, the demodulator of the characters on stage 208 sets the variable α to "1". Otherwise, the demodulator characters sets the variable α "-1" at step 207. Then at step 210 the demodulator symbol defines a fourth demodulated symbol s_{k,3}of the demodulated symbols corresponding to the accepted signal R_{k}using Y_{k}+α *Z_{k}and determines the third demodulated symbol s_{k,2}using Z_{k}, thereby defining the input soft value for Kahn is a high decoder.

So far we described the procedure for determining the soft values for the third and fourth demodulated symbols using quadrature component. Then is described the procedure for determining the soft values for the second and the first demodulated symbols using in-phase component.

At step 211, the demodulator characters computes Z'_{k}=|X_{k}|-2A using a two-dimensional received signal R_{k}consisting of in-phase component X_{k}and quadrature component Y_{k}and the distance 2 between two demodulated symbols on the same axis in the grid display. The demodulator of the characters on the stage 213 determines whether the resulting value calculated by the above formulas, a positive value, i.e. determines whether the MSB (or sign bit) of the result value is equal to "0". If the resulting value is positive, the demodulator of the characters goes to step 215. Otherwise, the demodulator of the characters goes to step 219, where he sets the parameter β to "0". At step 215 demodulator symbol determines whether the in-phase component X_{k}a positive value, i.e. determines whether the MSB in X_{k}a value of "0". If X_{k}has a positive value, the demodulator of the characters on stage 218 set is assigned the variable β
to "1". Otherwise, the demodulator characters sets the variable β "1" at step 217. Then at step 220 the demodulator symbol defines a second demodulated symbol s_{k,1}of the demodulated symbols corresponding to the accepted signal R_{k}using X_{k}+β *Z_{k}and defines a first demodulated symbol s_{k}o using Z_{k}, thereby defining the input soft value for the channel decoder. The procedure for determining the third and fourth demodulated symbol and the procedure of determination of the second and first demodulated symbols can be executed either sequentially or simultaneously. The received soft values of demodulated symbols are served in the channel decoder.

Figure 3 shows the functional block diagram for the procedure of determining the values of the soft decision demodulated symbols, respectively, a possible variant of implementation of the present invention. According to figure 3, the analyzer 301 quadrature signal component calculates the variable α using quadrature signal component Y_{k}the received signal R_{k}and the distance 2A between two demodulated symbols on the same axis table display according to the predetermined rule. As stated above, the variable ;
computed based on the sign of Z_{k}(=|Y_{k}|-2A) and the sign of the quadrature signal component of Y_{k}. The first block 302 issuance soft values solves the equation (9) using the variable α analyzer 301 quadrature signal component of the quadrature signal component of Y_{k}and distance 2A and generates soft values of the third and fourth demodulated symbols.

The analyzer 303 in-phase signal component calculates the variable β using in-phase signal component of X_{k}the received signal R_{k}and the distance 2A between two demodulated symbols on the same axis table display according to the predetermined rule. As stated above, the variable β calculated on the basis of the sign of the Z'_{k}(=|X_{k}|-2a) and the sign of the inphase signal component X_{k}. The second block 304 issuing soft values solves the equation (10) using the variable β analyzer 303 in-phase signal component, the in-phase signal component of X_{k}and distance 2a and generates soft values of the second and first demodulated symbols.

Figure 4 shows the demodulator symbol to calculate a soft decision channel decoder in the data transmission system using 16-hexadecimal QAM, according to a possible variant of the implementation of this is th invention,
moreover, the demodulator symbols implemented by the hardware based on equations (9) and equation (10). 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}the variable Z'_{k}parameter α and β all are real numbers with a numeric value, including the sign bit.

In accordance with figure 4, the first calculator 401 calculates Z_{k}=|Y_{k}|-2a using a quadrature signal component of Y_{k}the received signal R_{k}and the distance 2a between two demodulated symbols on the same axis table display and displays the value of Z_{k}. The multiplier 402 multiplies Z_{k}from the first transmitter 401 to -1 to invert the sign of Z_{k}. The first block 403 selection MSB selects the MSB of the quadrature signal component of Y_{k}and submits it to the first selector 405, and the second block 404 selection MSB selects MSB Z_{k}from the first transmitter 401 and supplies it to the second selector 406. The first selector 405 accepts Z_{k}from the first transmitter 401 and "-Z_{k}" from the first multiplier 402 and selects one of two inputs respectively to the select signal from the first block 403 selection MSB. The second selector 406 receives the output signal from the first selector 405 and "0" and selects the od is about from two inputs respectively to the select signal from the second unit 404 selection MSB.
The first adder 407 adds the output signal of the second selector 406 and a quadrature signal component of Y_{k}and gives a soft value of the fourth demodulated symbol. In addition, the value of Z_{k}calculated by the first calculator 401, issued as a soft value of the third demodulated symbol.

The second calculator 411 calculates Z'_{k}=|X_{k}|-2a using the in-phase signal component of X_{k}the received signal R_{k}and the distance 2A between two demodulated symbols on the same axis table display and outputs the value Z'_{k}. The multiplier 412 multiplies Z'_{k}with the second transmitter 411 -1 to invert the sign of the Z'_{k}. The third block 413 selection MSB selects the MSB of the in-phase signal component of X_{k}and supplies it to the third selector 415, and the fourth block 414 selection MSB selects MSB Z'_{k}with the second transmitter 411 and supplies it to the fourth selector 416. A third selector 415 accepts Z'_{k}with the second transmitter 411 and ' - Z'_{k}" with the second multiplier 412 and selects one of two inputs respectively to the select signal from the third block 413 selection MSB. The fourth selector 416 receives the output signal of the third selector 415 and "0" and selects one of two inputs respectively to the select signal from the fourth block 414 selection MSB. The second sums the tor 417 adds the output signal of the fourth selector 416 and the in-phase signal component of X_{
k}and gives a soft value of the second demodulated symbol. In addition, the value of Z'_{k}calculated by the second calculator 411, issued as a soft value of the third demodulated symbol.

Below is a comparison between a known procedure to obtain soft values and a new procedure to obtain soft values in the sense of achievable efficiency.

In the case of a calculator, the values of the soft decision using the procedure metric double minimum, sold by the equation (5), such a conventional method of determining a soft decision requires dozens of operations of squaring and comparison, while new demodulator symbols in figure 4 contains 4 adders, 2 multipliers and 4 multiplexer, which contributes to considerable reduction in time and complexity of the transmitter. Table 12 illustrates the comparison between equation (4) and equations (9)-(10) in terms of the type and number of operations i∈ {0,1,2,3}.

Table 12 | |||

Equation (4) | Equations (9) and (10) | ||

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

Summation | 3× 16+4=52 | Summation | 4 |

Squaring | 2× 16=32 | Multiplication | 2 |

Comparison | 7× 2× 4=56 | Multiplexing | 4 |

In the end, the present invention displays a Table 6-11 from equations (6)-(8) the process according to Tables 1-5, in order to reduce the delay time and the complexity that can occur when equation (4) is known procedures metric double minimum, or equation (5)obtained by the simplified metric double minimum, are implemented using a 16-hexadecimal quadrature amplitude modulation (QAM). In addition, the present invention provides the equations (9) and (10)representing the new formulas that are used to implement procedures for the metric dual of a minimum of 16 hexadecimal QAM. In addition, the present invention provides a device implemented by the hardware based on equations (9) and equation (10).

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 16 hexadecimal QAM, provides a simple and fast computations for obtaining the same result as in the case of using the known formulas. The transmitter Myagkov the values implemented in hardware, greatly reduces the working time and the complexity of the demodulator.

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 16 hexadecimal quadrature amplitude modulation (QAM) 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 the soft values Λ(S_{k,0}), Λ(S_{k,1}), Λ(S_{k,2}and Λ(S_{k,3}for input signal R_{k}(X_{k},Y_{k}by using the soft decision containing the first block definition soft values for determining the soft values Λ(S_{k,0}and Λ(S_{k,1}the first and second demodulated symbols from 4 demodulated symbols according to the following equations:

where Λ(S_{k,0}) denotes the soft value of the first demodulated symbol, Λ(S_{k,1}) train ACHAT soft value of the second demodulated symbol,
MSB means most significant bit or sign bit, |X_{k}| denotes the absolute value of the inphase component of X_{k}and 2A denotes the distance between two demodulated symbols on the same axis table display;

and the second block for determining the soft values for determining the soft values Λ(S_{k,2}and Λ(S_{k,3}) the third and fourth demodulated symbols from 4 demodulated symbols according to the following equations:

where Λ(S_{k,2}) denotes the soft value of the third demodulated symbol, Λ(S_{k,3}) denotes the soft value of the fourth demodulated symbol, |Y_{k}| denotes the absolute value of the quadrature component Y_{k}and 2A denotes the distance between two demodulated symbols on the same axis in the grid display.

2. The device according to claim 1, characterized in that the first unit determining the soft values includes a first calculator to calculate Z'_{k}=|X_{k}|-2A using the in-phase component X_{k}and the distance 2A between two demodulated symbols on the same axis table display and issuing Z'_{k}as the soft value of the first demo is Ulyanova symbol;
the first selector to obtain Z'_{k}from the first transmitter and the inverted signal Z'_{k}and select one of these two input signals respectively significant bit in-phase component X_{k}; a second selector for receiving the output signal of the first selector and the signal "0" and select one of these two input signals respectively significant bit Z'_{k}and the first adder for summing the output signal of the second selector and the in-phase component X_{k}and issuance of the soft value of the second demodulated symbol.

3. The device according to claim 1, characterized in that the first unit determining the soft values includes a second calculator for calculating Z_{k}=|Y_{k}|-2A using quadrature component Y_{k}and the distance 2A between two demodulated symbols on the same axis table display and issuance of Z_{k}as the soft values of the third demodulated symbol; a third selector for receiving Z_{k}from the second transmitter and the inverted signal Z_{k}and select one of these two input signals respectively sign bit of the quadrature component Y_{k}; a fourth selector for receiving the output signal of the third selector and the signal "0" and select one of these two input signals respectively significant bit of Z_{k}and the Torah adder for summing the output signal of the fourth selector and the quadrature component Y_{
k}and issuing soft values of the fourth demodulated symbol.

4. The demodulation device 16 hex quadrature amplitude modulation (QAM) 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 the soft values Λ(S_{k,0}), Λ(S_{k,1}), Λ(S_{k,2}and Λ(S_{k,3}for input signal R_{k}(X_{k},Y_{k}by using the soft decision containing a first calculator for determining a soft value Λ(S_{k,2}) of the third demodulated symbol from 4 demodulated symbols by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the absolute value |Y_{k}| quadrature component Y_{k}; a second calculator for determining a soft value Λ(S_{k,2}fourth demodulated symbol by calculating Y_{k}+α·Z_{k}using the first variable αdefined soft value of the third demodulated symbol and the sign bit of the quadrature component Y_{k}where Z_{k}- soft value of the third demodulated symbol; a third calculator for determining a soft value Λ(S_{k,0}the first demodulated symbol by the subtraction distance 2A from the absolute values |X_{
k}| in-phase component X_{k}; a fourth calculator for determining a soft value Λ(S_{k,1}the second demodulated symbol by calculating X_{k}+α·Z_{k}using the second variable βdefined soft value of the first demodulated symbol and the sign bit in-phase component X_{k}where Z'_{k}- soft value of the first demodulated symbol.

5. The device according to claim 4, characterized in that the second computer sets the first variable α "0"if the soft value of Z_{k}the third demodulated symbol has a negative value, sets the first variable α -1, if Z_{k}has a positive value and the quadrature component Y_{k}has a negative value, and sets the first variable α 1 if Z_{k}has a positive value and the quadrature component Y_{k}has a positive value.

6. The device of claim 4, wherein the fourth computer sets a second variable β "0"if the soft value Z'_{k}the first demodulated symbol has a negative value, sets a second variable β -1, if Z'_{k}has a positive value and the in-phase component X_{k}has a negative value, and ustanavli is no second variable β
on 1 if Z'_{k}has a positive value and the in-phase component X_{k}has a positive value.

7. The way demodulation of 16 hexadecimal quadrature amplitude modulation (QAM) 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 the soft values Λ(S_{k,0}), Λ(S_{k,1}), Λ(S_{k,2}and Λ(S_{k,3}for input signal R_{k}(X_{k},Y_{k}by using the soft decisions, including the steps

calculating soft values Λ(S_{k,0}and Λ(S_{k,1}the first and second demodulated symbols from 4 demodulated symbols according to the following equations:

where Λ(S_{k,0}) denotes the soft value of the first demodulated symbol, Λ(S_{k,1}) denotes the soft value of the second demodulated symbol MSB means most significant bit or sign bit, |X_{k}| denotes the absolute value of the inphase component of X_{k}, 2a denotes the distance between two demodulated symbols on the same axis table display; and

calculating soft values Λ(S_{k}
and Λ(S_{k,3}) the third and fourth demodulated symbols from 4 demodulated symbols according to the following equations:

where Λ(S_{k,2)}denotes the soft value of the third demodulated symbol, Λ(S_{k,3}) denotes the soft value of the fourth demodulated symbol, |Y_{k}| denotes the absolute value of the quadrature component Y_{k}, 2a denotes the distance between two demodulated symbols on the same axis in the grid display.

8. The method according to claim 1, characterized in that the first step of calculating soft values includes the steps of calculating Z'_{k}=|X_{k}|-2a using the in-phase component X_{k}and the distance 2A between two demodulated symbols on the same axis table display and outputting the calculated Z'_{k}as the soft value of the first demodulated symbol;

selecting as the first selected signal soft Z'_{k}the first demodulated symbol or the inverted signal of the soft values of Z'_{k}the first demodulated symbol, respectively significant bit in-phase component X_{k};

selecting as the second selected signal is and the first selected signal or signal "0", respectively significant bit soft values Z'_{
k}the first demodulated symbol and

summation of the second selected signal and the common mode component of X_{k}and issuance of the soft value of the second demodulated symbol.

9. The method according to claim 7, characterized in that the second step of calculating soft values includes the steps

Z_{k}=|Y_{k}|-2a using quadrature component Y_{k}and the distance 2A between two demodulated symbols on the same axis table display and issuance of Z_{k}as the soft values of the third demodulated symbol;

selecting as the third selected signal soft values of Z_{k}the third demodulated symbol or the inverted signal of the soft values of Z_{k}the first demodulated symbol respectively sign bit of the quadrature component Y_{k};

selection as the fourth selected signal of the third selected signal or signal "0", respectively significant bit of Z_{k}and

summation of the fourth selected signal and the quadrature component Y_{k}and issuing soft values of the fourth demodulated symbol.

10. The way demodulation signal 16 hex quadrature amplitude modulation (QAM) for receiving the input signal R_{k}(X_{k},Y_{k})containing the k-th quadrature stood the Commissioner, Y_{
k}and k-th in-phase component X_{k}and to generate the soft values Λ(S_{k,0}), Λ(S_{k,1}), Λ(S_{k,2}and Λ(S_{k,3}for input signal R_{k}(X_{k},Y_{k}by using the soft decisions, including the steps

(a) calculating soft values Λ(S_{k,2}) of the third demodulated symbol from 4 demodulated symbols by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the absolute value |Y_{k}| quadrature component Y_{k},

(b) determining a soft value Λ(S_{k,3}fourth demodulated symbol by calculating Y_{k}+α·Z_{k}using the first variable αdefined soft value of the third demodulated symbol and the sign bit of the quadrature component Y_{k}where Z_{k}- soft value of the third demodulated symbol;

(c) calculating soft values of A(S_{k,0}the first demodulated symbol by subtracting a distance 2A from the absolute values |X_{k}| in-phase component X_{k}and

(d) determining a soft value Λ(S_{k,1}the second demodulated symbol by calculating X_{k}+β·Z'_{k}using the second variable βdefined me is Kim the value of the first demodulated symbol and the sign bit in-phase component X_{
k}where Z'_{k}- soft value of the first demodulated symbol.

11. The method according to claim 10, wherein step (b) involves the installation of the first variable α "0"if the soft value of Z_{k}the third demodulated symbol has a negative value, setting the first variable α -1, if Z_{k}has a positive value and the quadrature component Y_{k}has a negative value, and set the first variable α 1 if Z_{k}has a positive value and the quadrature component Y_{k}has a positive value.

12. The method according to claim 10, wherein step (d) involves the installation of the second variable β "0"if the soft value Z'_{k}the first demodulated symbol 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

install the second variable β 1 if Z'_{k}has a positive value and the in-phase component X_{k}has a positive value.

13. The method of demodulating a received signal in a data transmission system that uses a modulation technique for separating the output sequence of the channel encoder 4 bits and the mapping of bits in a particular one of the 16 SIG is real points,
having in-phase component X_{k}and the quadrature component Y_{k}including milestones

calculating soft values of Z_{k}the third demodulated symbol by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the level |Y_{k}| quadrature signal component Y_{k};

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

determining a soft value of the fourth demodulated symbol by calculating Y_{k}+α·Z_{k}using quadrature component Y_{k}soft values of Z_{k}and the first variable α;

calculating soft values of Z'_{k}the first demodulated symbol by subtracting the distance 2A between two demodulated symbols on the same axis in the grid display of the absolute values |X_{k}| in-phase signal component of X_{k};

installation vtoro the 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; and

determining a soft value of the second demodulated symbol by calculating X_{k}+β·Z'_{k}using the in-phase component X_{k}soft Z'_{k}and the second variable β.

**Same patents:**

FIELD: radio communications; digital communication systems.

SUBSTANCE: proposed spectrum-division frequency modulator that incorporates provision for using frequency-modulated signals of high modulation index in communication systems where frequency resources are limited has two multipliers, two phase shifters, smoothing-voltage generator, two amplitude-phase modulators, carrier generator, adder, and frequency shift control unit.

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FIELD: communication systems using variable transfer process; optimizing modulation process and code repetition frequency in given hardware environment.

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29 cl, 6 dwg, 1 tbl

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FIELD: physics.

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29 cl, 15 dwg

FIELD: information technologies.

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