Research And Implementation Of RLL(1,10;4,6) Modulation Code Of High-density Optical Disc

In optical disc system, channel coding has a great impact on channel performance, which is one of the factors requiring careful consideration in optical disc standard, also the emphasis of intellectual property. Run-Length Limited (RLL) modulation code is widely used in optical disc. Focusing on the key technology to be solved in next generation versatile disc standard, RLL (1, 10; 4, 6) modulation code is studied, which has independent intellectual property right.On the basis of analyzing the function, application and development trend of modulation codes and RLL code, modulation is pointed out to be the fatal dependent factor of high-density optical disc. Parameter of RLL code is analyzed in brief.Diverse RLL codes are presented, including fixed-length codes, state-dependent codes, variable-word length, fixed-rate codes and look-ahead codes. The features of these different modulation codes are discussed. On the basis of above, construction method of RLL (1, 10; 4, 6) code which applies look-ahead coding is put forward, involving basic code table and substitution table. The step and flow of RLL (1, 10; 4, 6) modulation and demodulation have been designed, and the performance is analyzed in respect to channel character, principally the method of controlling direct current. Synchronization code is derived in the specific run-length limitation.Performance of RLL (1, 10; 4, 6) code is analyzed by means of software simulation, and demodulation algorithm is implemented at chip level by FPGA. The idea and theory of simulation software are introduced, especially sliding-block coding and computing the running digital sum dynamically, which help control direct current. Simulation of demodulation process is implemented in Quartus II environment.Anylization indicates that RLL (1, 10; 4, 6) modulation code, with independent intellectual property right, is fit for next generation versatile disc, and the FPGA-based algorithm has the virtue of accurate function, efficient process and reliable performance.