2.2. Research of a data transmission system with the bch codes when using the Gaussian channel
It is necessary for execution of this part of laboratory operation:
to make model on the basis of a reference sample with use of the BCH codes;
using modulator and demodulator , to turn system with noise proof code to the channel with Gaussean noise.
to carry out comparison of channel without excess code and channel with encoding
to decorate the results in the form of graph.
Using a command commlibv1, to call a structural scheme of communicaton channel to the screen and to activate a coding block of information Error control coding. To activate a block Modulation and on the opening window Library: com_modu to click block Digital modem twice. A window of digital modems is opened. On this window it is necessary to activate the green block MASC demo with double click and to to keep the opened window on the screen of monitor for the following virtual oscilograph.
Figure 2. Example of the screen with table of BCH code.
For carrying out of the given part of laboratory work it is necessary.
For the preparing of necessary model in the window Library: com_modu to activate a green demonstrative block S - QASK demo2 and to gather model by a sample representing in Figure 4.
Figure 3. A model for researching of BCH code in QAM modulation
In given model is used quadratic –amplitude modulation on 16 positions is used. A source of signals transmission data in the form of decade sequence from 0 to 15, which are formed to binary vectors processed in communication channels. A cause of such approach is contained in necessity of speed of transmission 23 information in existed limited on energetic filling frequency stripe. A new element in model is application Display block. This block can be used for output both scalar both vector size .if display size is vector, then initial window changes automatically, about what it is justified appearance of small black triangle on the right low corner of block. For each vector elements is created its mini window, but to become visible it is necessary to extend the figure of block. For this it should divide block, the figure of the block so as black triangle disappears. .
Hence, a number of informational elements, offloaded by the source of information to the system must be valet to the number 4 information source in system, should be multiple to number 4. In the course of the work it is necessary to study parameters of each block and changing probability of symbol distortion in gauss communication channel to research possibilities BCH code in different length but similar correcting capacity. In this model for its initiation it is necessary on the line of the main menu to m choose Simulation and then Start. To install attributes of model to install proceeding from experience work with obligatory reflection in a protocol and in a report.