SOJOURN TIME ANALYSIS OF DQDB MAN FOR LANs INTERCONNECTION

The Distributed Queue Dual Bus(DQDB) Metropolitan Area Network(MAN) is a promising solution for the evolution from current networks to B-ISDN. The performance of the DQDB MAN for Local Area Networks(LANs) interconnection is analyzed. The effects of message length, traffic load of upstream and downstream nodes and the parameters of bandwidth balancing mechanism and network counters on the sojourn time of message in the buffer are investigated, which present a valuable reference for the implementation of the DQDB MAN.

A novel QC-LDPC code based on the finite field multiplicative group for optical communications

A novel construction method of quasi-cyclic low-density parity-check(QC-LDPC) code is proposed based on the finite field multiplicative group,which has easier construction,more flexible code-length code-rate adjustment and lower encoding/decoding complexity.Moreover,a regular QC-LDPC(5334,4962) code is constructed.The simulation results show that the constructed QC-LDPC(5334,4962) code can gain better error correction performance under the condition of the additive white Gaussian noise(AWGN) channel with iterative decoding sum-product algorithm(SPA).At the bit error rate(BER) of 10-6,the net coding gain(NCG) of the constructed QC-LDPC(5334,4962) code is 1.8 dB,0.9 dB and 0.2 dB more than that of the classic RS(255,239) code in ITU-T G.975,the LDPC(32640,30592) code in ITU-T G.975.1 and the SCG-LDPC(3969,3720) code constructed by the random method,respectively.So it is more suitable for optical communication systems.

Construction of a new regular LDPC code for optical transmission systems

A novel construction method of the check matrix for the regular low density parity check （LDPC） code is proposed. The novel regular systematically constructed Gallager （SCG）-LDPC（3969,3720） code with the code rate of 93.7% and the redundancy of 6.69% is constructed. The simulation results show that the net coding gain （NCG） and the distance from the Shannon limit of the novel SCG-LDPC（3969,3720） code can respectively be improved by about 1.93 dB and 0.98 dB at the bit error rate （BER） of 10s, compared with those of the classic RS（255,239） code in ITU-T G.975 recommendation and the LDPC（32640,30592） code in ITU-T G.975.1 recommendation with the same code rate of 93.7% and the same redundancy of 6.69%. Therefore, the proposed novel regular SCG-LDPC（3969,3720） code has excellent performance, and is more suitable for high-speed long-haul optical transmission systems.

MZI-based wavelength interrogation system with tunable-FBG

We proposed a scheme of fiber Bragg grating （FBG） sensor interrogation system based on all fiber Mach-Zehnder Interferometer （MZI） edge filter and tunable-FBG. The equal power signals from FBG sensor and tunable FBG are coupled into port 1 and port 2 of MZI respectively. The experimental results show that the interrogation precision of the proposed system is 0.02 nm in a range of I nm. Furthermore, the precision can be improved by adjusting the two interference arms of the filter.

A novel decoding algorithm based on the hierarchical reliable strategy for SCG-LDPC codes in optical communications

An effective hierarchical reliable belief propagation(HRBP)decoding algorithm is proposed according to the structural characteristics of systematically constructed Gallager low-density parity-check(SCG-LDPC)codes.The novel decoding algorithm combines the layered iteration with the reliability judgment,and can greatly reduce the number of the variable nodes involved in the subsequent iteration process and accelerate the convergence rate.The result of simulation for SCG-LDPC(3969,3720)code shows that the novel HRBP decoding algorithm can greatly reduce the computing amount at the condition of ensuring the performance compared with the traditional belief propagation(BP)algorithm.The bit error rate(BER)of the HRBP algorithm is considerable at the threshold value of 15,but in the subsequent iteration process,the number of the variable nodes for the HRBP algorithm can be reduced by about 70%at the high signal-to-noise ratio(SNR)compared with the BP algorithm.When the threshold value is further increased,the HRBP algorithm will gradually degenerate into the layered-BP algorithm,but at the BER of 10-7and the maximal iteration number of 30,the net coding gain(NCG)of the HRBP algorithm is 0.2 dB more than that of the BP algorithm,and the average iteration times can be reduced by about 40%at the high SNR.Therefore,the novel HRBP decoding algorithm is more suitable for optical communication systems.

A novel BTC decoding algorithm based on the genetic algorithm in optical communication systems

Combining the advantages of both the genetic algorithm(GA) and the chase decoding algorithm, a novel improved decoding algorithm of the block turbo code(BTC) with lower computation complexity and more rapid decoding speed is proposed in order to meet the developing demands of optical communication systems. Compared with the traditional chase decoding algorithm, the computation complexity can be reduced and the decoding speed can be accelerated by applying the novel algorithm. The simulation results show that the net coding gain(NCG) of the novel BTC decoding algorithm is 1.1 dB more than that of the traditional chase decoding algorithm at the bit error rate(BER) of 10-6. Therefore, the novel decoding algorithm has better decoding correction-error performance and is suitable for the BTC in optical communication systems.

OCDMA SystemSignature Code Design Theory Via Finite Projective Geometry

Optical orthogonal code is the main signature code employed by optical CDMA system. Starting from modern mathematics theory, finite projective geometry and Galois theory, the essential connection between optical orthogonal code designing and finite geometry theory were discussed; find out the corresponding relationship between the parameter of OOC and that of finite geometry space. In this article, the systematic theory of OOC designing based on projective geometry is established in detail. The designing process and results of OOC on projective plane PG(2,q) and on m-dimension projective space are given respectively. Furthermore, the analytical theory for the corresponding relation between OOC with high cross-correlation and k-D manifold of projective space is set up. The OOC designing results given in this article have excellent performance, whose maximum cross-correlation is 1, and the cardinality reaches the Johnson upper bound, i.e. it realizes the optimization in both MUI and system capacity.

A new probability decoding scheme based on genetic algorithm for FEC codes in optical transmission systems

Based on the genetic algorithm(GA),a new genetic probability decoding(GPD) scheme for forward error correction(FEC) codes in optical transmission systems is proposed.The GPD scheme can further offset the quantification error of the hard decision by making use of the channel interference probability and statistics information to restore the maximal likelihood transmission code word.The theoretical performance analysis and the simulation result show that the proposed GPD scheme has the advantages of lower decoding complexity,faster decoding speed and better decoding correction-error performance.Therefore,the proposed GPD algorithm is a better practical decoding algorithm.