Device for coding convolutional code


H03M13/12 -

 

(57) Abstract:

The invention relates to telecommunication and can be used in high-speed modems for encoding information signals convolutional code. The purpose of the invention is the increase in the noise generated by the device sequence signals in channels with irregular phase of the carrier wave that are multiples of 90°, by increasing the free distance between sequences of signals encoded by a convolutional code. For this purpose a device for coding convolutional code containing the first block of flash memory, the first delay element, a first adder, a second adder, the second block of the flash memory, the second delay element, a first multiplier, a third adder, a fourth adder, the third delay element, the second multiplier, the fourth delay element, the fifth adder and the fifth delay element, enter the inverters, the sixth adder and the sixth delay element. 4 Il., table 1.

The invention relates to telecommunication and can be used in high-speed modems for encoding information signals convolutional code.

A device for convolutional coding, containing the shift register p is aligned signals, containing three delay lines, two adder and the block selection signal point [2]

The disadvantages of the known devices are low immunity generated surtace-coded sequences at low signal to noise ( 20 dB), and their sensitivity to surges phase of the carrier wave, is equal to n /2, where n is 1,2,3, the presence of which in the communication channel becomes impossible to correctly decode the received sequence.

Closest to the invention by the technical nature of a device for coding convolutional code, the output signals of which are insensitive to the jumps of the phase of the carrier wave in the communication channel, a multiple of the 90about[3] containing the first block of flash memory, the first and second outlet through which the first and second delay lines connected respectively to third and fourth inputs of the first unit's permanent memory, connected in series to the third delay line, a first adder, a second adder, a fourth delay line, the third adder, the fourth adder, the fifth delay line, the second unit's permanent memory, and a fifth adder, the first multiplier and the second multiplier, the output of the fifth adder sueoka permanent memory, and the output of the fifth delay line is combined first input of the third delay line, the first multiplier and the second multiplier, the second inputs of the first multiplier and the second multiplier are respectively the output of the third adder and the second output of the first unit's permanent memory, the outputs of the first multiplier and the second multiplier connected respectively to the second inputs of the second and fourth adders, the first output of the first block of flash memory is the second input of the third adder and the third input of the second unit's permanent memory, a fourth input connected to a second output of the first unit's permanent memory, moreover, the first and second inputs of the first and second blocks of flash memory are informational inputs and outputs of the second unit's permanent memory are the outputs of the device.

The device generates signals encoded with a convolutional code, which allow for the transfer of 4 information bits (m 4), one interval modulation. Used for convolutional coding code speed R /+1 2/3 provides asymptotic coding gain from coding (AMC) 4 dB compared to the unencrypted transmission method quadrature-amplitude modulebase transmitted surtace-coded sequence of signals, equal . Signals encoded with a convolutional code, are insensitive to the jumps of the phase of the carrier wave in the communication channel, a multiple of the 90about. This is achieved at the expense made in a certain way [3] assignment of subsets of signal points obtained by partitioning [1,4] original ensemble of signals, the navigation graph States corresponding destination bit signal points of the ensemble of signals and the operation of the differential encoding.

To decode the signal sequence encoded by a convolutional code, the technique uses a maximum likelihood decoder with soft decision [5,6] decision rule such a decoder can be formulated as follows. As decisions are made, such information sequence} which would give the output of the second unit's permanent memory the sequence} is closest to the received} by Euclidean distance

- min,

this}c where C is the set of all possible sequences at the output of the second unit's permanent memory. Characteristics of "soft" decoding depend on the free distance

dfree= min,

when Sn} Pn} Sthe Euclidean distance between them dfreeoriginate, respectively, the binary posledovatelnostyun} ian'} Then the probability that instead transferred to posledovatelnostyun} is decoded posledovatelnostyun'} is defined as

Pr({ }Pn}{Sn}) Pr({}a}{an}) Q(d2), where Q is the integral of probabilities;

the standard deviation of the noise.

When the signal-to-noise tending to infinity, the probability that a solution will be adopted Sn'} located at a distance greater than dfreefrom indeed passed Sn} can be neglected compared to the likelihood that the solution will be accepted sequence at a distance of dfreeSn} So

P N(dfree)Q(dfree/2), (1) where N(dfree) the number of error sequences, located at a distance of dfreefrom indeed passed Sn} which depends on the structure of the transition graph [4]

As can be seen from (1), a determining influence on the immunity surtace-coded sequence of signals has a free distance of dfree.AMC, m is ω (abgs) on changes in phase of the carrier wave, multiples of 90aboutthe benefit of coding is greatly reduced at low and medium signal-to-noise (15-18 dB). For example, if the error probability POsh10-4the benefit of coding is about 2.5 dB.

Thus, the encoded convolutional code sequence generated by the device is a prototype, has low immunity, due to the amount of free distance.

The aim of the invention is to increase the noise generated by the device signal sequence, and hence the energy gain from coding in channels with irregular phase of the carrier wave that are multiples of 90aboutat low and medium signal-to-noise (s/n).

The aim is achieved by a device for coding convolutional code containing the first block of flash memory, the first and second inputs of which are the same information input device, the first output of the first block of the flash memory is connected through a first delay element with a third input of the first unit's permanent memory and directly with the first inputs of the first and second adders and the second unit's permanent memory, the second output pajanou memory and directly to the second inputs of the first adder and the second unit's permanent memory, the third and fourth inputs and the outputs of which are respectively of the same name information input and output device, the output of the second adder connected to the first input of the first multiplier, the output of which is connected to the first input of the third adder, the fourth adder, the output of which through the third delay element is connected to a second input of the first multiplier and the first input of the second multiplier, the fourth delay element, the output of which is connected to the first input of the fifth adder, and the fifth delay element, equipped with an additional inverter, a sixth adder and the sixth delay element, the output of the first adder is connected to a second input of the third adder, the output of which is connected to a second input of the fifth adder, the output of which is connected in series through the fifth delay element and the first inverter is connected to a second input of the second adder and the first input of the fourth adder, the inputs of the second inverter and the sixth delay element connected to the output of the third delay element, the output of the sixth delay element is connected to the input of the fourth delay element, the output of the second inverter is connected to the fifth input of the second unit's permanent memory, the input of the third inverter at the output of which is connected to the first input of the sixth adder, the second input is connected to the first output of the first unit's permanent memory, the output is connected to a second input of the fourth adder.

Comparative analysis with the prototype shows that the proposed device is characterized by the presence of new units: inverter, the sixth delay line, the sixth adder and their relationships with other elements of the schema.

Thus, the proposed device complies with the criterion of "novelty".

Comparison of the proposed solution with other technical solutions shows that the inverters, the delay line adder is widely known [7]

However, their introduction in the specified communication with other circuit elements in the proposed device for coding convolutional code is achieved by improving the noise immunity of the signals generated by the device, in channels with irregular phase of the carrier wave that are multiples of 90aboutby implementing a larger free distance between any two coded sequences of signals compared to the prototype. This allows to conclude that the technical solutions according to the criterion of "significant differences".

In Fig.1 shows a structural electrical diagram of the device for which perehodov convolutional encoder.

Device for coding convolutional code contains the first block 1 permanent memory, the first line 2 delay, the second delay line 3, which represents a differential encoder, connected in series sixth line 4 delay, the fourth delay line 5, the fifth adder 6, a fifth delay line 7, the first inverter 8, the fourth adder 9, a third delay line 10, the second inverter 11, the second block 12 permanent memory and sequentially connected to the second adder 13, the first multiplier 14, the third adder 15, and the first adder 16 and connected in series, the third inverter 17, the second multiplier 18 and the sixth adder 19.

The device operates as follows.

The information input device at time n received data bits I1n, I2n, I3nI4n(m 4). Two bits I4n, I3nproceed directly to the fourth and third inputs of the second unit's permanent memory and are referred to as Y4nand Y3nand the bits I2nand I1nserved on the first and second inputs of the differential encoder.

The table presents data describing the operation of the differential encoder.

The use of differential kopirovaniya.symantec jumps to phase carrier wave, multiple 90about. The possibility of using differential encoding is provided by special purpose bits Y4n, Y3n, Y2n, Y1n, Y0nthe signal points of the ensemble of signals. From the output of the differential encoder bits Q2n'Q1n' come on convolutional encoder, containing connected in series sixth line 4 delay, the fourth delay line 5, the fifth adder 6, a fifth delay line 7, the first inverter 8, the fourth adder 9, a third delay line 10, the second inverter 11 and connected in series to the second adder 13, the first multiplier 14, the third adder 15, and the first adder 16 and connected in series, the third inverter 17, the second multiplier 18 and the sixth adder 19. The operation of the convolutional encoder describe the following logical functional dependency

< / BR>
the sum mod 2.

They bind subsequent state W1n+1, W2n+1, W3n+1W4n+1and the output bit Y0nencoder with the current state of W1nW2nW3nW4nand the input bits of the encoder Q2n'Q1n'. These expressions are obtained by minimizing with charts of Vaca full functional dependency, due to the count of transitions and destinations is the main encoder as a state machine with memory.

Each transition leaving one state and leads to the subsequent, is assigned a certain set of signal points of the ensemble of signals, called subset. These subsets are based on the idea of display by splitting the set [1,2,4] this is consistent splitting the original extended signal set (alphabet signals) nested subsets and the distance between the elements of the subset (signal points) at each step of partitioning increases, and the number of elements decreases. As the source of the extended signal set is applied triazacyclohexane cross constellation (32-CR) (Fig.2). It is advanced because transmission m 4 unencrypted data bits over the channel during the interval modulation method quadrature-amplitude modulation (QAM) would be enough to have an ensemble of signals, consisting of 16 pixels (16-QA) (Fig.3). The use of convolutional coding to the input information bits Q2n'Q1n'(m=2) leads to the appearance of additional excess fifth bits Y0n. Therefore, the ensemble of signals must have M 2m+132 points. In this case, it is the ensemble of signals 32-CR, and generated by the device sequence signals, encoded convolutional code jumps of phase by a multiple of 90about.

The approach is based on partitioning the original signal of the set of nested subsets leads to the splitting of the original tridtsatidevyatiletnego signal set 2= 8( 2 number of input bits of the convolutional encoder) nested subsets a, b, C, D, E, F, G, H (Fig.2).

The splitting is performed in the (+1) 3 steps. In the first step of partitioning obtained two subsets (Fig.2) ABCD and EFG H (U sign Association) with the minimum Euclidean distance1= =2 whereo- minimum Euclidean distance to the original signal seto= .

In the second step, break out subsets of A U B C U D E F U, G U H2=1= 2. The last step of partitioning are eight subsets A, B, C, D, E, F, G, H3=2= 4. When the rotation signal set clockwise 90aboutsubsets A, B, C, D, E, F, G, H, go, respectively, the subsets E, F, G, H, C, D, A, B. When rotating 180aboutsubsets A, B, C, D, E, F, G, H, go, respectively, C, D, A, B, G, H, E, F, and at 270aboutin G, H, E, F, A, B, C, D. a graph of transitions was based on the following rules [3, 4]

(a) transition graph must be symmetric and all PE the future in different States, you must match the signals of one of the subsets obtained in the first step of partitioning;

b) the signals from these subsets are assigned to the transitions coming out of different States and leading to the same condition;

g) if we denote q of States of the encoder through i 0,1,q-1, then to the encoder, and as a result, the sequence of signals are transparent to the phase uncertainty in the channel binds multiple of 90aboutmust exist functions one correspondence fl:0,1,q-1} _0,1,q-1} l 1, 2, 3 such that running the following statement. For each transition from state i to state j, i, j 0,1,q-1} denote by XO group of signal elements of one of the resulting partitioning subsets, and through X1, x2 and X3 groups of signal elements derived from HO through clockwise rotation, respectively, at 90, 180 and 270about. Then each transition from state fl(i) the condition fl(j), l 1, 2, 3 is assigned to a group of signal elements Xl, l 1, 2, 3, respectively.

Transition graph shown in Fig.4. Features one correspondence have

f1: f2: f3:

For the transition graph (Fig. 4) the squared free distance RA is, the subset of A (zero state), the nearest to it is the sequence of signal points belonging to the subsets of B-D (considered lattice chart obtained by the scan of the transition graph in time). Taking into account the minimum distance between points of the subsets a and b, a and DAB= 2,AB=2 Fig.2) the squared free distance between the observed sequences is equal to dfree2AB2+AD212. If the correct sequence to select another, then there is a sequence, separated from her at a distance .

Free distance allows to estimate AMC compared to the unencrypted transmission method QAM-16. Then, taking into account the normalization by the average power for AMC have [2, 4]

Gc= 10lg 10lg 4,7712 B.

From the output of the convolutional encoder output bits, denoted as Y0n, Y1n, Y2ndo respectively 5, 2 and 1 inputs of the second unit's permanent memory, 3 and 4, the inputs of which are served noncoding information bits, denoted by Y3nand Y4n.In accordance with an input bit sequence YInI of 0.1. 4 in the block are selected for transmission over the elements of the ensemble of signals to the jumps of the phase of the carrier wave, multiple 90aboutthe purpose of the bit YInI of 0.1.4 signal elements are made in compliance with the following rules (Fig.2):

1. The signal elements in each of the 2m+1238 subsets A, B, C, D, E, F, G, H are assigned the same value bits Y2n, Y1n, Y0n.

2. The group, consisting of bits Y2n, Y1ncorresponding sets of signal elements assigned to the transitions leaving the same state of the transition graph contains all possible combinations of bits Y2nY1n.

3. Each of the four signal elements of a group in which every element can be obtained from the previous by rotating clockwise 90aboutare assigned different values of bit pairs Y2nY1n;

4. The purpose of unencrypted data bits Y4nY3nthe signal elements of the ensemble of signals can be arbitrary. In this case, the signal elements of a group consisting of four elements, obtained from the first by a rotation by 90, 180 and 270aboutclockwise, respectively, are assigned to the same bits Y4n, Y3n. The following applies to the assignment of bits Y2n, Y1n, Y0n, dovletbat differential encoder is used, the sequence 11, 10, 01, 00, consisting of a variety of bit pairs Y2nY1nand assigned according to the third paragraph of the rules above, the sequence of signal elements of a group in which every element can be obtained from the previous by rotating clockwise 90about.

In accordance with the input bits YInI of 0.1.4 in the second block 12 permanent memory is uniquely determined signal point and the output unit 12 receives signals Qnand Pncorresponding to the coordinate in-phase and quadrature components of the signal point.

The second block 12 permanent memory is a permanent storage device (ROM) that stores values of the signal elements. Input bits YIn, I= 0,1.4 for a block 12 form an address code signal element in ROM. Examples of implementation of the block 12 in Fig. 5.17, 18, S. 182, 183 [7]

The simulation results of the proposed device for coding convolutional code showed that, compared with the prototype in channels with additive white Gaussian noise at the races phase carrier wave that are multiples of 90aboutwhen small and medium-sized relations with/W (15-18 dB) it provides a significant increase Pomeranian what posledovatelnostei. For example, the code gain, in comparison with the unencrypted transmission (QAM-16) in the channel with abgs, the phase ambiguity, multiple of 90aboutand baud rate 9600 bit/s is approximately 3.6 dB at POsh10-4that about 1.1 dB more code win provided a device prototype in the same conditions.

DEVICE FOR CODING CONVOLUTIONAL CODE containing the first block of flash memory, the first and second inputs of which are the same information input device, the first output of the first block of the flash memory is connected through a first delay element with a third input of the first unit's permanent memory and directly with the first inputs of the first and second adders and the second unit's permanent memory, the second output of the first block of the flash memory is connected via a second delay element with the fourth input of the first unit's permanent memory and directly to the second inputs of the first adder and the second unit's permanent memory, the third and fourth inputs and the outputs of which are respectively of the same name information input and output device, the output of the second adder connected to the first input of the first multiplier, the output of academici connected to the second input of the first multiplier and the first input of the second multiplier, the fourth delay element, the output of which is connected to the first input of the fifth adder, the fifth delay element, characterized in that, to improve the noise generated by the device signal sequence, it introduced an inverter, a sixth adder and the sixth delay element, the output of the first adder is connected to a second input of the third adder, the output of which is connected to a second input of the fifth adder, the output of which is connected in series through the fifth delay element and the first inverter is connected to a second input of the second adder and the first input of the fourth adder, the inputs of the second inverter and the sixth delay element connected to the output of the third delay element, the output of the sixth delay element is connected to the input of the fourth delay element, the output of the second inverter is connected to the fifth input of the second unit's permanent memory, the input of the third inverter is connected to the second output of the first unit's permanent memory, the output is connected to a second input of the second multiplier, the output of which is connected to the first input of the sixth adder, the second input is connected to the first output of the first unit's permanent memory, the output is connected to a second input of the fourth adder.

 

Same patents:

The invention relates to data transmission systems for communication channels and can be used in devices for decoding by the Viterbi algorithm

The invention relates to computing and communication technology and can be used in digital communication systems using convolutional codes

The invention relates to telecommunications and is intended for use in digital transmission systems convolutional code

The invention relates to systems for the transmission of information via communication channels and can be used in devices for decoding by the Viterbi algorithm
Up!