Compression Algorithms Of Packets In Narrowband Power Line Communication

As the State is increasing the efforts to accelerate the automation and informationization construction of the grid, the role of power line carrier communication (referred to as PLC) in the field of communication is becoming more and more important. But a lot of data is produced with the fast development of the power line carrier communication, which make the power line carrier communication network have to face the problem of massive data processing. Storage and transmission of large amount of data has become a subject of concern.This subject is proposed to improve power line carrier communication packet transmission efficiency and accuracy. This paper first analyzes the power line carrier communication pacekt's characteristics, which are put into consideration during the designing of the PLC packet compression and decompression algorithms. The compression and decompression algorithms are both implemented in the Power Line Carrier Communication chip of certain company.Through access to a large number of documents and related research, this article summarizes the PLC packet, and gets the following two important features: First, the power line carrier communication packet is short, the length of which does not exceed 256 bytes, and thus it is not easy to be compressed from the perspective of statistic model. Second, the transmission rate of the PLC packet is low, so the time spent on transmission is far more than the time spent on the local processing of the packets.Based on the above two features and the existing research results home and abroad, combined with the design of the PLC chip of certain company, this paper consults large amount of relative documents, and at the same time does deep research both on the nature of data compression and the variety of compression algorithms. At last this paper chooses to utilize a universal data compression algorithm-LZ77-to design and implement one plain compression/decompression algorithm on the PLC packet. Then, with theoretical analysis and relative experiment results, this paper improves the designed compression algorithm from the following two aspects: compression scale and data structure. In the choice of compression scale, this paper compares the advantages and the disadvantages of compressing in byte degree, bit degree and semi-byte degree in order to improve compression ratio, and at last fix to compress in the scale of semi-byte. In the improvement of data structure, this paper tries to reduce the compression extra spending by firstly setting flag bit and then using a kind of compression count. In the implement of the algorithm, this paper breaks the sequence compressing order to improve compression ratio, which chooses the optimal compression combination after computing every position's longest match rather than sequentially sliding the sliding-window. In the search step of the algorithm, this paper introduces suffix array to improve the search efficiency.Finally, this paper presents and analyzes the latest power line carrier communication packet compression algorithm.This subject has a solid theoretical foundation and a relatively complete theoretical system, and the company which develops the implementation environment this paper used has reached great achievements, and produces high quality products. All the fruits above make good foundation for this subject.