Jen-Fa Huang

Learn More
In this paper, we proposed a novel method for constructing quasi-cyclic low-density parity-check (QC-LDPC) codes based on circulant permutation matrices via a simple quadratic congruential equation. The main advantage is that QC-LDPC codes with a variety of block lengths and rates can be easily constructed with no cycles of length four or less. Simulation(More)
The propagation channel of a mobile radio system exhibits severe signal shadowing and multipath fading, which results in wide variation of signal-to-interference ratio (SIR) at the receiver. To tackle this problem, power control is used to maintain the desired link quality and thus achieve higher capacity. In order to mitigate the channel variation effect(More)
New wavelength/time code families constructed with short code lengths are proposed for optical code-division multiple- access networks. Since the code matrices inherit correlation properties from the underlined one-dimensional codes, much effort for codeword searching and code property validation is saved. In addition, since the proposed code matrices with(More)
One approach for designing the one-coincidence sequence (OCS) low-density parity-check (LDPC) codes of large girth is investigated. These OCS-LDPC codes are quasi-cyclic, and their parity-check matrices are composed of circulant permutation matrices. Generally, the cycle structures in these codes are determined by the shift values of circulant permutation(More)
Residue stuffed quadratic congruence (RSQC) codes are proposed for radio-over-fiber (RoF) scheme based on spectral-amplitude-coding (SAC) optical code-division multiple-access (OCDMA) networks. These new codes generated from residue method can enlarge the code space, and the decoder of this new code is cost-effective and suitable for realization. The error(More)
A fiber Bragg grating (FBG) encoder/decoder scheme based on correlation subtractions of nearly orthogonal M-sequence codes is presented. With proper coder design, a receiver can reject interfering users and obtain quasi-orthogonality between optical code-division multiple-access (CDMA) users in the network. However, optical CDMA networks may be degraded by(More)
This paper presents an enhanced security mechanism to protect spectral-amplitude-coding optical code-division multiple-access networks against eavesdropping. This study proposes an alternative to huge code-space size techniques such as wavelength hopping/time spreading or spectral-phase coding for network protection against eavesdropping by exploiting the(More)
Two codeword families and the corresponding encoder/decoder schemes are present for spatial/frequency optical code-division multiple-access communications. These 2-D codewords have multiple weights per row and can be encoded/decoded via compact hardware. With the proposed decoding mechanism, the intended user will reject interfering users and(More)
A new two-dimensional frequency/spatial code for spectral-amplitude coding a optical code-division multiple-access system is proposed. The corresponding coder/decoder pairs are based on the tunable fiber-Bragg gratings cooperating with optical splitters/combiners, and multiple-access interference can be eliminated through the proposed decoding mechanism.(More)
A modified Welch-Costas (MWC) code family for the spectral-amplitude-coding (SAC) optical code-division multiple-access (OCDMA) system is proposed. On utilizing the property of the MWC codes, more compact coder/decoders can be realized via waveguide and fiber gratings. This system has a superior performance as compared to the previous Walsh-Hadamard-coded(More)