Increase the Resistance of Digital Television to Interference

Abstract

The development of the principle of redundant information in the data stream of a digital television system is proposed.

The proposal is focused on future television systems and its essence consists in processing the bitstream using methods that originally existed in analog, discrete-analog form, and then in the form of digital filtering. To do this, redundancy is introduced into the data stream, which allows us to switch from the bitstream to its vector representation. A criterion for detecting a logical vector of a signal is proposed — it is a level that divides the detection field into two areas: the detection area of logical zero and the detection area of logical units. The width of each region takes into account the probability of a logical unit and zero, respectively. The work also proposed models of coding and decoding blocks, which were tested by modeling by the criterion with the same probabilities of occurrence of unity and zero. Simulation for two variants of the development of the principle of redundancy is performed. In the first embodiment, redundancy was introduced by fivefold transmission of the same information bit. On the receiving side, bit information was detected and converted to an analog vector. Depending on the length of the vector, a decision was made to detect and decode the received information bit.

In the second case, on the transmitting side, each information bit was encoded with a five-digit Barker code. In this case, the value of logical 1 was converted into a logical vector containing a direct Barker code, and the value of logical 0 was formed as an inverse Barker code.

On the receiver side, as in the first case, bit information was detected, logical data was converted into an analog vector, and the vector was convoluted with the reference sequence in the form of components +1 and -1, which corresponds to the deployed Barker code. The obtained value of the correlation impulse in accordance with the detection criterion was converted into informational logical 0 or 1 of the received data stream.

The advantage of the proposed principle of redundancy of information is that the implementation is feasible without interference with the radio blocks. Accordingly, the expansion of the signal spectrum is not observed. It is noted that implementation is possible without loss of transmission speed in the presence of 5 dedicated carriers (subcarriers). When transmitting within a single carrier, the image volume must be correspondingly reduced, or the transmission speed will have to be reduced by 5 times.

The simulation was performed for the case of broadcasting using the MATLAB system.

The method is not involved in radio signal but operating only before transmitting and after receiving and detecting logic part. One permits a simple realization both programmable and programmable-apparatus version.