An RLL code design that maximises channel utilisation

Comprehensive (d,k) sequences study is presented, complemented with the design of a new, efficient, Run-Length Limited (RLL) code. The new code belongs to group of constrained coding schemas with a coding rate of R = 2/5 and with the minimum run length between two successive transitions equal to 4. Presented RLL (4, oo) code uses channel capacity highly efficiently, with 98.7% and consequently it achieves a high-density rate of DR = 2.0. It is implying that two bits can be recorded, or transmitted with one transition. Coding techniques based on the presented constraints and the selected coding rate have better efficiency than many other currently used codes for high density optical recording and transmission

An Optimal Unequal Error Protection LDPC Coded Recording System

For efficient modulation and error control coding, the deliberate flipping approach imposes the run-length-limited(RLL) constraint by bit error before recording. From the read side, a high coding rate limits the correcting capability of RLL bit error. In this paper, we study the low-density parity-check (LDPC) coding for RLL constrained recording system based on the Unequal Error Protection (UEP) coding scheme design. The UEP capability of irregular LDPC codes is used for recovering flipped bits. We provide an allocation technique to limit the occurrence of flipped bits on the bit with robust correction capability. In addition, we consider the signal labeling design to decrease the number of nearest neighbors to enhance the robust bit. We also apply the density evolution technique to the proposed system for evaluating the code performances. In addition, we utilize the EXIT characteristic to reveal the decoding behavior of the recommended code distribution. Finally, the optimization approach for the best distribution is proven by differential evolution for the proposed system.Comment: 20 pages, 18 figure

M-ary run length limited coding

This thesis consists of two parts: 1) a result of the rationality of channel capacity for the M -ary (d, k) constraint, and 2) a software package which has been designed to aid in the development of efficient, high density channel encoders for M -ary (d, k) constrained recording code. It has been written for the platforms of IBM PC or PC compatible and Sun Workstations. The designed software in this thesis involves three steps. The first step is to calculate the capacity of a RLL code after the user has chosen (M,d,k) . The channel capacity specifies the maximum ratio of information ( p ) bits/codeword ( q ) bits achievable in implementing these codes and gives options of code choice for any specific task. The second step is to find a code efficiency (eta) = R/C by choosing p and q , and display the state transition matrix of finite state transition diagram and finite state transition diagram of the code. The last step is to aid the user in the generation of a code, by using state splitting algorithm of R. Adler, D. Coppersmith and M. Hassner [10]

Variable- and fixed-length balanced runlength-limited codes based on a Knuth-like balancing method

Abstract: A novel Knuth-like balancing method for runlengthlimited words is presented, which forms the basis of new variableand fixed-length balanced runlength-limited codes that improve on the code rate as compared to balanced runlength-limited codes based on Knuth’s original balancing procedure developed by Immink et al. While Knuth’s original balancing procedure, as incorporated by Immink et al., requires the inversion of each bit one at a time, our balancing procedure only inverts the runs as a whole one at a time. The advantage of this approach is that the number of possible inversion points, which needs to be encoded by a redundancy-contributing prefix/suffix, is reduced, thereby allowing a better code rate to be achieved. Furthermore, this balancing method also allows for runlength violating markers which improve, in a number of respects, on the optimal such markers based on Knuth’s original balancing method

Adding RLL Properties to Four CCSDS LDPC Codes Without Increasing Their Redundancy

This paper presents the construction of Run Length Limited (RLL) Error Control Codes (ECCs) from four Low Density Parity Check (LDPC) Codes specified by Consultative Committee for Space Data Systems (CCSDS). The obtained RLL-ECCs present a practical alternative to the CCSDS codes with pseudo-randomizers. Their advantage is that the maximal runlengths of equal symbols in their codeword sequences are guaranteed, which is not the case if the common approach with pseudo-randomizers is used. The other advantages are that no additional redundancy is introduced into encoded codewords and that the encoding and decoding procedures of the original error control CCSDS codes do not have to be modified in the following cases. In the first case if hard decoding is used and the transmission channel can be modeled as a Binary Symmetric Channel (BSC) or in the second case if soft decoding and coherent Binary Phase Shift Keying (BPSK) modulation is used and the appropriate transmission channel model is an Additive White Gaussian Noise (AWGN) channel