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FPGA bitstream compression and decompression based on LZ77 algorithm and BMC technique

In this paper, we propose a FPGA bitstream compression method based on LZ77 algorithm and Bitmask-based Compression(BMC) Technique. In order to improve the compression ratio, we optimize LZ77 by encoding the variable `length' with golomb code and simplifying the encoding output. We develop appropriate adding strategy and choose proper cost-benefit parameters of BMC, and combine the BMC with LZ77 to further improve the compression ratio. Experiment results shows that our method has 12.9% improvement in compression ratio over fixed dictionary approach and 9.3% over LZSS on an average. Our compression method also has good compatibility. A decompressor which has two look-ahead buffers is designed for decompression. The pipeline architecture of the decompressor improves the throughput. The decompression throughput reaches 1692Mb/s according to Xilinx ISE report. We have verified the decompressor on a Virtex-5 FPGA.