The Application Of The Data Compression Technology To The Communication

As an important problem in the information science, the data compression technology has been given widly attention. The main purpose of data compression is to represent the origin information sent by the information resource with minimum data, thus to decrease the storage space of the information, and to increase the transport speed of it. To some special data, the compressing ratio of the existing arithmetics may be very high, but to others, it may be very low. So, in order to find arithmetic with good integrated capability, it is essential to compare arithmetics according to all factors in application.The noise coding and noiseless coding are main parts of data compression technology. In this paper, the latter is studied.Some arithmetics such as HUFFMAN. ARITHMETIC. LZSS series (LZSS and LZSSB,LZSSD and LZHUF which were improved on the base of LZSS) and LZW series(LZW and ILZW improved on the base of LZW) are studied.Acrodding to these arithmetics, some C programs are written to simulate the compressing status of different arithmetics .In the end, for its high compressing ratio, the LZSSB arithmetic is selected and is applied to the existing communication plat.According to the characteristic of the communication plat, the program is improved as follows:(1) The conversion of bits. The data in the storage space can't be visited by the unit of 8bit on the choosen DSP. But if 16 bit. 32bit. or 48bit is choosen as the comparing unit, the compressing ratio will decrease. So two buffers of different size are setup to convert the outside data to meet the request of DSP, and through this method, the compressing ratio is increased.(2) Deal with the end sign of the datum. Two methods are selected to judge the end of data from the data source: one is to monitor the control signal of the data end, the other is to test the change of buffer pointer.(3) Deal with the dictionary. In this paper, two methods are selected to deal with the dictionary. One is updating it as setting up. Another is updating the dictionary after the data in the buffer are dealt with. The second method debases the compressing ratio, but it decreases the runing time of the program because it lessens the complication of the program. Through this, the other programs can get bigger running space.(4) Other improvements. To enhance the agility of the program, the setup of buffer is not in program but decided by communication system. In the begining of the program, the program read the buffer_size in some address. The buffer_size must be transported before the compressed data, thus the expanding program can read out the size in it. So the consistency of compression andPIexpanding model can be ensured.Through these improvments, the arithmetic of LZSSB is succeeded in the running on the existing communication plat. Its compressing ratio and real-time are all meet the need of the project.