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A new code for Spectral Amplitude Coding - Optical Code Division Multiple Access (SAC-OCDMA) is proposed and is called Flexible Cross-correlation (FCC) code. The FCC code possesses various advantages; including easy code construction using Tridiagonal matrix compared to other SAC-OCDMA codes such as MDW, MQC and MFH, shorter code length and the important properties of this code is the flexible cross-correlation. Our results reveal that FCC code can effectively alleviated Phase Induced Intensity Noise (PIIN) and allows large cardinality and improve the bit error rate performance.

Block Data Transmission Systems (BDTS) are used in high-speed wireless communication systems with time dispersive channel characteristics. In such systems, blocks of data are separated by zeros to mitigate the effect of Inter-Symbol-Interference (ISI) between the blocks. An optimal detection process employs the Maximum Likelihood Block Detection (MLBD) technique on each block individually in the presence of ISI and Gaussian noise based on the Euclidean distance as an objective function. The detection process is computationally expensive therefore Genetic Algorithms have been used to reduce the overall design complexity. In this work, three types of Genetic Algorithms have been incorporated in the detection process i.e. the conventional GA, Micro GA(µGA), and Hybrid µGA to reduce computational load. In particular, a novel training method for Hybrid µGA has been proposed. Simulation results at 10dB channel SNR for the BDTS with Hybrid µGA executes as low as 3,750 number of objective functions evaluation for a block size of 20. The Bit Error Rate (BER) performance of this system is relatively good i.e. around 1dB inferior to the BDTS using the Exhaustive Search method that requires as many as 220 number of objective functions evaluation.

In this paper, an improvement of achievable system capacity Avalanche photodiode (APD) performance of spatial/spectral modified double weight (MDW) code for cardinality, bit error rates (BER) and noise interference is analyzed. The results in very good agreement indicate that 61% cardinality improvements compare to 2-D MDW code with PIN. The effective transmitted power (P sr ) for 2-D MDW-APD (M=135, N=3) improves by 8.5dBm at 10−9 error floor. At low gain BER value is mitigated through suppressing PIIN. Apparently, performance of the proposed system improves substantially with APD.

This paper presented a code with non-zero in-phase cross- correlation Spectral Amplitude Coding Optical Code Division Multiple Access (OCDMA) system. The proposed code called Modified Non Zero Cross Correlation (MNZCC) code. The MNZCC code can be constructed easily for any given number of users, weights and cross correlation (λmax) using tridiagonal matrix properties. MNZCC code will be demonstrated in simulation using OptiSys.6.0. The results indicated that MNZCC code is truly performed better with the presence of noise. We find that the performance of MNZCC code is better than OCDMA codes such as MDW and MFH. Finally, in term of systems complexity, MNZCC code introduced cost effectiveness due to less number of filter with direct detection scheme.

This paper presented a new class of code called Modified Non-Zero Cross Correlation (MNZCC) Code for Spectral-Amplitude Coding Optical Code Division Multiple Access. The MNZCC code can be constructed easily for any given number of users, weights and cross correlation (λmax) with tridiagonal matrix properties. We find that the performance of MNZCC code is better than OCDMA codes such as MDW and MFH. In term of performance, systems with MNZCC code had shown superior performance, where the Bit Error Rate (BER) of MNZCC code is significantly better than OCDMA codes such as MDW and MFH. Fiber Brag Grating filter has been used for the implementing SAC-OCDMA systems. Finally, in term of systems complexity system with MNZCC code with direct detection scheme introduced cost effectiveness due to less number of filter in decoder as well encoder.

This paper presented the novel of a new class of code with Non-Zero Cross-Correlation for Spectral-Amplitude Coding in Optical Code Division Multiple Access (OCDMA) systems. A new code namely Modified Non-Zero Cross Correlation Code (MNZCC). MNZCC code can be constructed easily for a given number of users K, weights and for a given cross correlation (λmax). The proposed code was demonstrated in simulation using OptiSys. 6.0 to observe the system performance. The results shown, that, the proposed code has superior performance in term of spectrum efficiency and reducing the effect of MAI and suppressing the effects of PIIN, with better bit error probability. The results are obtained for the MNZCC were compared with others existing optical codes such as DW code.

A new technique for constructing the Quasi Cyclic Low density Parity Check (QC-LDPC) codes based on splitting rows into sub rows method is proposed. The proposed QC-LDPC code, at BER of 10−6 achieves 0.1dB coding gain over the PEG-LDPC codes. Moreover, in the high E b / N 0 region, the proposed code with girths 16 and 20 respectively, achieve 0.056 dB and 0.27 dB at a BER of 10−5 over the randomly constructed code. Simulation results portray that large girth QC-LDPC codes achieve a 0.1dB coding gain over randomly constructed codes and perform 1.3dB from the Shannon-limit at a BER of −6 with a code rate of 0.89 for block length of 1332.

A new family of spectral/spatial spectral amplitude-coding (SAC) optical code division multiple access (OCDMA) scheme using Modified Double Weight (MDW) code is developed. The new codes are derived from Modified Double Weight codes with good cross correlation. This proposed system can suppress the phase-induced intensity noise (PIIN) by using multiuser interference (MUI) cancellation property. The proposed 2-D OCDMA MDW can offer a much larger capacity compare to the 1-D OCDMA MDW Code.

This paper proposes a new technique for constructing the Quasi-Cyclic low density parity check (QC-LDPC) codes based on row division method. The new codes offer more flexibility in term of girth, code rates and codeword length. In this method of code construction, the rows are used to form as the distance graph. Then they are transformed to a parity-check matrix in order to acquire the desired girth. The new QC-LDPC codes show good bit-error rate performance as compared to the renowned Mackay codes for given values of E b /N o by 0.12 dB at BER of10-7 .

In this paper, a multicarrier frequency hopping spread spectrum (MCFH-SS) system with girth-six low-density parity-check (LDPC) codes is developed as forward error correction scheme to improve its anti-jamming (AJ) capabilities. The paper also evaluates the bit error rate (BER) of girth-six LDPC codes with a column weight 3 for the given values of fractional bandwidth (ρ). It is found that the performance of MCFH-SS system with LDPC codes is significantly better than the system employing fast frequency hopping spread spectrum (FFH-SS) with girth-six LDPC codes in the presence of partial band noise jamming (PBNJ) over Additive White Gaussian Noise (AWGN) channel. At ρ =1, the BER of MCFH-SS and FFH-SS system is approximately 10−3 and 10−2 , respectively. This shows the effectiveness of MCFH-SS system with girth-six LDPC codes.

To cut down the hardware implementation cost this paper presents an efficient method to construct large girth Quasi-Cyclic low density parity check (QC-LDPC) codes. The row groups are paired two times the row weight, which has the complexity as compared to the connection of individual columns and rows. The complexity of directing within groups estimates on the transposition employed to connect rows and columns between groups. The newly obtained codes are incorporated with diversity techniques and are employed as a forward error correction codes to cater for some anti-jamming (AJ) competences in the presence of partial band noise jamming (PBNJ). The robustness of two girth-twelve QC-LDPC codes is evidenced by comparing it with randomly constructed LDPC codes and QC-LDPC codes proposed in [14].

This paper presents a memory efficient version of set partitioning in hierarchical tree (SPIHT). The proposed coder termed as memory efficient SPIHT (MESH), uses a single re-usable list instead of three continuously growing linked lists as in conventional SPIHT. The list is re-initialized at the beginning of each bit-plane (coding pass) and is exhausted within that bit-plane itself. Another feature of the proposed coder is that it uses a single pass for each bit-plane by merging the sorting and refinement passes of conventional SPIHT together. The reinitialization of the list in each bit-plane makes the proposed coder inherently error resilient. The performance of the proposed coder is measured in terms of coding efficiency and the worst case memory requirements for list entries in each bit-plane. The performance comparison with SPIHT shows that the proposed algorithm results in 50-70% memory saving while retaining a coding efficiency comparable to SPIHT.