RU2427088C1 - Method of transmitting information in feedback system - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: in a feedback system, a data sequence is encoded by a noise-immune code at the transmitting side. The obtained data packet is transmitted to a communication channel. The encoded data sequence is extracted from the received data packet at the receiving side of the communication system and then decoded. Error grouping factors in the channel are calculated. The length and number of frequency subchannels of the data packet are then corrected to a value whereby the data transmission rate for the current state of the communication channel is maximum, after which a new value of the length of the data packet is transmitted over a feedback channel to the transmitting side. Correction of the number of subchannels and the length of the data packet is repeated when the error grouping factor changes relative its previous value by more than 10%.

EFFECT: high rate of transmitting information in a communication channel owing to reduced flow of retransmitted channel units.

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Description

The invention relates to telecommunications, and in particular to methods for transmitting discrete information. The method can be used to transmit information from digital sources over decameter range radio communication channels, as well as through other channels with non-stationary parameters formed using multichannel systems.

A known method of transmitting messages in a feedback system (patent US 5,490,168, IPC H04L 1/18, 1/16, 1/00, H04J 3/24, H04B 017/00, G06F 011/00, publ. 06.02.1996), consisting in the fact that the packet of data of the original length transmitted by the transmitting part is received by the receiving part of the system. After receiving, the receiving part counts the number of words received with errors, and if this number exceeds the permissible level, a decision is made and a command is sent to the transmitting part to change the length of the data packet to a second value. After that, the transmission and reception of information is carried out on these parameters. If the number of words received with errors calculated in the receiving part is within the acceptable level, the receiving part makes a decision and sends a command to the transmitting part to change the length of the data packet to the initial state.

The disadvantage of this method is the relatively low speed of information transfer in the communication channel due to the use of only two values of the lengths of the information packet.

Also known is a method of transmitting messages in a feedback system (application No. 1120932 EPO, IPC 7 H04L 1/00, H04L 1/20, published 01.08.2001), which consists in the fact that the information packet is encoded with an error-correcting code on the transmitting side of the communication system , then service information is added to the error-correcting code and the obtained information sequence is transmitted to the communication channel. On the receiving side of the communication system, a noise-tolerant code is extracted from the received information sequence and decoded. Based on the results of decoding the error-correcting code, the number of errors in the information packet and the average probability of errors per bit in the communication channel characterizing the quality of the communication channel are estimated. Depending on the average probability of errors per bit in the communication channel, the optimal length of the information packet is determined, which ensures the maximum transmission rate of useful information in the communication channel and the new value of the length of the information packet on the feedback channel is brought to the transmitting side of the communication system.

The disadvantage of this method is the relatively low speed of information transfer in the communication channel due to the low accuracy of determining the parameters of the communication channel and the error in choosing the length of the information packet.

The closest analogue in its technical essence to the proposed method is a message transmission method (patent RU 2259636, IPC Н04L 1/100, 1/12, 1/20, publ. 03/10/2004), the prototype method consists in the fact that the transmitting side of the communication system, the information sequence is encoded with a noise-resistant code, then the service information is included in the encoded information sequence and the received data packet of length L _{i is} transmitted to the communication channel, on the receiving side of the communication system, the encoded is extracted from the received data packet th information sequence, decode it and calculate the error grouping index in channel α ₁ , for which the frequency of packets λ received without error is calculated, the average error probability P _{Оsh is} calculated, and the error grouping index α _{1 is} calculated from the obtained values of λ, P _Ош and L _i , then corrected data packet length L _i to a value L _k, in which the data transmission rate for the current channel is maximum communication state, and transmitting the new length information packet on the feedback channel to transmit hundred ONU. The new value of the length of the information packet is selected using the functional dependence specified in the table.

This method provides the choice of the optimal length of the information packet depending on the quality of the communication channel that provides grouping of errors within one packet, however, the disadvantage of the prototype method is the relatively low speed of information transfer when operating a multi-channel modem operating on N frequency subchannels, because the number of subchannels for transmitting the packet is always 1 and is not adjusted depending on the change in the state of the communication channel.

The aim of the invention is to develop a method of transmitting information in a feedback system, including N frequency subchannels, providing an increase in the speed of information transmission in the communication channel by reducing the flow of retransmitted channel blocks.

This goal is achieved by the fact that in the known method of transmitting information in a feedback system, namely, on the transmitting side of the communication system, the information sequence is encoded with an error-correcting code, service information is included in the encoded information sequence, the received data packet of length L _{i is} transmitted to the channel communication, on the receiving side of the communication system, the encoded information sequence is extracted from the received data packet and decoded, the indicator is calculated ruppirovaniya errors in the channel α _1, which is counted packets frequency X, received without error, calculating an average error probability P _err and obtained values of λ, P _err and L _i is calculated error grouping index α _1, then adjust the length L _i of the data packet to the value of L _k , at which the information transfer rate for the current state of the communication channel is maximum, after which a new value of the information packet length is transmitted via the feedback channel to the transmitting side. For a multi-channel system including N frequency subchannels, a data packet is transmitted over N frequency subchannels by sequentially distributing the bits of the packet over subchannels 1 through N. The error grouping index α _{f is} calculated for N frequency subchannels. The calculated value of α _f adjust the number of subchannels n≤N, where n = 1,2, ..., N, for transmitting information packets. Repeated adjustment of the number of subchannels n is repeated when the index of error grouping a _f changes relative to its previous value by more than 10%. The values of the length L _k and the number of subchannels n for transmitting information packets after changing the state of the communication channel are adjusted using a predefined table-function dependence.

Thanks to the new set of essential features, when implementing the claimed method, an adjustment is provided, depending on the state of the communication channel, both the size of the channel block in length and the number of frequency subchannels allocated to this channel block, as a result of which error grouping is achieved within one channel block using a multi-channel modem operating on N frequency subchannels, which ensures the achievement of the stated goal.

The claimed method is illustrated by drawings:

Figure 1 is a diagram illustrating a method of forming a signal-code structure when transmitting messages;

Figure 2 is a diagram illustrating a method of generating a signal-code structure when receiving messages.

The proposed method for transmitting messages in communication systems is implemented as follows.

On the transmitting side, the source information packet is encoded with an error-correcting code, for example, an error-correcting cyclic code.

Next to the word error-correcting code add service information, such as a synchronization sequence. As a synchronization sequence, a binary sequence of suitable length with good synchronizing properties is selected, for example, a Barker sequence or a sequence of maximum length (1st-order Reed-Muller code).

Further, the symbols of the output information sequence enter the communication channel. In the communication channel due to interference, distortion of the transmitted signal is possible. This can lead to the fact that the transmitted information sequence will be received with errors.

On the receiving side of the communication system, the error-correcting code is cyclically synchronized first. To do this, in the information sequence of characters received at the input of the receiving part, detect the synchronizing sequence.

After the establishment of cyclic synchronization, the error-correcting code is selected in the received information sequence. Next, decoding the error-correcting code with error detection is performed. In the process of decoding the error-correcting code, either the correct reception of the message, or transformation (false reception) of the message, or erasure (rejection of decoding) of the message is possible. When decoding the error-correcting code, the frequency 2 of receiving code words is counted, during decoding of which no errors were detected.

For a channel with grouping of errors, the probability of erroneous reception of a block of symbols is calculated according to the well-known formula (Khilko V.O. Some aspects of the use of OFDM technology in mobile communication systems. Mobile systems, issue 7. 2007)

From the formula, if there are statistics on the reception of error-free code words for two different block lengths of symbols L _i1 , and L _i2 and two different sizes of the channel block in frequency n ₁ and n ₂ , we write a system of two nonlinear equations that allows us to determine the parameters of the communication channel α _l and α _f

α ₁ and α _f - indicators grouping errors, calculated by the formulas

where λ ₁ and λ ₂ are the frequencies of error-free reception of blocks of various lengths, respectively, L _i1 and L _i2 and, correspondingly, the channel block sizes in frequency n ₁ and n ₂ .

The parameters α _l and α _f determine the quality of the communication channel. Depending on the quality of the communication channel, a new value of the channel block size is determined at which the information transfer rate for the current state of the communication channel is maximum.

The speed of information transfer is expressed by the formula

where L = (L _i * n) is the total number of characters in the channel block;

S is the number of service symbols in the channel block;

(L-S) - the number of information symbols in the channel block.

Next, choose such values of n and L _k that will provide the maximum of function C. These values determine the optimal option for the size of the channel block, that is, n is the number of frequency subchannels occupied by the channel block, L _k is the length of the channel block.

The found parameters n and L _{k are} brought to the transmitting side, which uses them in further information exchange.

Channel block sizes for DCM channels with various parameters DKM channel parameters Channel Block Parameters Baud rate α _l α _f p _osh n L _k L FROM 0.1 0.1 5 · 10 ^-2 7 7 49 0.996 0.2 0.2 5 · 10 ^-2 8 10 80 0.999 0.3 0.3 5 · 10 ^-2 four 37 148 0.992 0.4 0.4 5 · 10 ^-2 8 43 344 0.998 0.5 0.5 5 · 10 ^-2 22 fifty 1100 0.995 0.6 0.6 5 · 10 ^-2 60 60 3600 0.794 0.7 0.7 5 · 10 ^-2 56 54 3024 0.332 0.8 0.8 5 · 10 ^-2 53 fifty 2650 0.145 0.9 0.9 5 · 10 ^-2 42 49 2058 0.064 0.1 0.9 5 · 10 ^-2 21 35 735 0.998 0.2 0.8 5 · 10 ^-2 13 42 546 0.997 0.3 0.7 5 · 10 ^-2 fourteen 47 658 0.98 0.4 0.6 5 · 10 ^-2 eighteen fifty 900 0.997 0.6 0.4 5 · 10 ^-2 23 58 1334 0.999 0.7 0.3 5 · 10 ^-2 36 26 936 0.98 0.8 0.2 5 · 10 ^-2 36 24 864 0.996 0.9 0.1 5 · 10 ^-2 38 10 380 0.998

Thus, by changing the length of the channel block and the number of frequency subchannels allocated for transmission of the channel block, depending on the state of the communication channel, error grouping within one channel block is ensured, as a result, the number of channel blocks transmitted repeatedly is reduced, thereby increasing the information transfer rate .

Claims (3)

1. The method of transmitting information in a feedback system, namely, that on the transmitting side of the communication system, the information sequence is encoded with an error-correcting code, then service information is included in the encoded information sequence and the received data packet of length L _{i is} transmitted to the communication channel, on the receiving side communication systems extract the encoded information sequence from the received data packet, decode it, and calculate the error grouping index in the channel α _l , for which calculate the frequency of the packets λ received without error, calculate the average probability of error R _os and, using the obtained values of λ, R _os and L _i calculate the error grouping index α ₁ , then adjust the length of the data packet L _i to the value L _k at which the information transfer rate for the current state of the communication channel is maximum, and a new value of the length of the information packet is transmitted via the feedback channel to the transmitting side, characterized in that for a multi-channel system including N frequency subchannels, the data packet is transmitted in N cha -frequency subchannels by sequential bit allocation package subchannels 1 through N, wherein the error index grouping α _f N is calculated for the frequency subchannels, further, based on the calculated corrected value α _f number of subchannels n≤N, where n = 1,2, ... , N for transmitting information packets, moreover, the adjustment of the number of subchannels n is repeated when the value of α _{f is} changed relative to its previous value. 2. The method according to claim 1, characterized in that the repeated adjustment of the number of subchannels n is repeated when the index of error grouping α _{f is} changed relative to its previous value by more than 10%. 3. The method according to claim 1, characterized in that the values of the length L _k and the number of subchannels n for transmitting information packets after changing the state of the communication channel are adjusted using a predetermined tabular functional dependence.

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