Houshou Chen

Combined Selective Mapping and Binary Cyclic Codes for PAPR Reduction in OFDM Systems

In this paper, we consider reduction of PAPR in OFDM systems with BPSK subcarriers by combining SLM and binary cyclic codes. This combining strategy can be used for both error correction and PAPR reduction. We decompose a binary cyclic code into direct sum of two cyclic subcodes: the correction subcode used for error correction and the scrambling subcode for PAPR reduction. The transmitted OFDM signal is selected that achieves minimum PAPR, from the set of binary cyclic codewords. The received signal can be easily decoded without the need of any side information. Simulations show that the proposed scheme with simplex code as scrambling subcode achieves good PAPR reduction.

PAPR Reduction of OFDM Signals Using Partial Transmit Sequences and Reed-Muller Codes

This letter proposes a modified PTS technique using binary Reed-Muller (RM) codes for error correction and PAPR control in BPSK OFDM systems. A RM code is divided into the direct sum of a correcting subcode for encoding information bits and a scrambling subcode for encoding PAPR bits. The transmitted signal of the resulting OFDM sequence is selected with minimum PAPR from a number of candidates which are codewords of a coset of the scrambling subcode. We consider the RM codes in natural and cyclic orderings. Numerical results show that RM codes in cyclic ordering achieve better performance in PAPR reduction than RM codes in natural ordering.

Extended Reed-Solomon Codes for Optical CDMA

In this paper, the extended Reed-Solomon codes are modified to construct a new family of 2-D codes for asynchronous optical code-division multiple access (O-CDMA). In addition of having expanded and asymptotically optimal cardinality, these 2-D asynchronous optical codes can be partitioned into multiple tree structures of code subsets, in which code cardinality is a function of the (periodic) cross-correlation value assigned to the subset. The performance of these 2-D optical codes is analyzed and compared with that of the multilevel prime codes. Our results show that the unique partition property of the new optical codes supports a trade-off between code cardinality and performance for meeting different system requirements, such as user capacity and throughput. In addition, the multiple tree structures of the new codes potentially support applications that require rapid switching of many codewords, such as in O-CDMA-network gateway or in strategic environments where code obscurity is essential.

An embedding strategy for large payload using convolutional embedding codes

A matrix embedding (ME) code is a commonly used steganographic technique that used linear block codes to perform the embedding process. However, a lack of low-complexity maximum-likelihood decoding schemes in linear block codes limited the embedding efficiency for sufficiently large lengths. This paper proposes a novel and practical hiding algorithm for binary data based on convolutional codes. Compared to a matrix embedding algorithm that uses linear block codes, the method proposed in this study is appropriate for embedding a sufficiently long message into a cover object. The proposed method employs the Viterbi decoding algorithm for embedding to identify the coset leader of convolutional codes for large payloads. Experimental results show that the embedding efficiency of the proposed scheme using convolutional codes is substantially superior to that of the scheme using linear block codes.

Trellis Structure and Higher Weights of Extremal Self-Dual Codes

A method for demonstrating and enumerating uniformly efficient (permutation-optimal) trellis decoders for self-dual codes of high minimum distance is developed. Such decoders and corresponding permutations are known for relatively few codes.The task of finding such permutations is shown to be substantially simplifiable in the case of self-dual codes in general, and for self-dual codes of sufficiently high minimum distance it is shown that it is frequently possible to deduce the existence of these permutations directly from the parameters of the code.A new and tighter link between generalized Hamming weights and trellis representations is demonstrated: for some self-dual codes, knowledge of one of the generalized Hamming weights is sufficient to determine the entire optimal state complexity profile.These results are used to characterize the permutation-optimal trellises and generalized Hamming weights for all [32,16,8] binary self-dual codes and for several other codes. The numbers of uniformly efficient permutations for several codes, including the [24,12,8] Golay code and both [24,12,9] ternary self-dual codes, are found.

A Modified Selective Mapping with PAPR Reduction and Error Correction in OFDM Systems

This paper proposed a PAPR reduction method for BPSK OFDM systems and 16-QAM OFDM systems respectively. The strategy of the algorithms is to use a correction subcode for error control and a scrambling subcode for PAPR control. The transmitted OFDM sequence is selected with minimum PAPR from a number of candidates which form a coset of scrambling subcode for each codeword of correction subcode. In a BPSK OFDM system, the PAPR reduction is obtained by combining the SLM method with binary cyclic codes. In a 16-QAM OFDM system, the PAPR reduction is achieved by combining the SLM with block coded modulation. The received signal of the modified SLM can be decoded without the need of explicit side information and the proposed scheme achieves good PAPR reduction.

Applications and Constructions of Optical Codes With Large Cardinality and Multiple Tree Structures

Algebraic optical codes with large cardinality and unique tree structures of multiple levels of subsets of codewords for adjustable code performance and cardinality have recently been proposed. As shown in this paper, these characteristics support new network architecture and applications for rapid code switching and physical-layer security in optical code-division multiple access networks. In addition, a new “translate” method of converting “additive” error-correction codes (ECCs) into this kind of optical codes is investigated and demonstrated with four families of Reed-Solomon codes. With rich families of ECCs, our method enhances the collections of optical codes. The performances of these “tree-structured” optical codes are algebraically analyzed and verified, for the first time, using the weight distribution of ECCs.

A modified constellation extension scheme with low complexity for PAPR reduction in OFDM systems

High peak-to-average power ratio (PAPR) is one major drawback of orthogonal frequency division multiplexing (OFDM) systems. Recently, the constellation extended scheme (CES) is an active technique for reducing PAPR of OFDM signals. However, this approach needs high computational load and more inverse Fast Fourier transform (IFFT) operations for finding the transmitted signal with minimum PAPR out. Therefore, this paper proposes a modified CES with lower computational load and IFFT operations than the CES in a 16-QAM OFDM system. Our proposed method, which combines the CES with the partial transmit sequences (PTS) technique, is also called CES-PTS. When compared to PTS techniques, our proposed method has no need to transmit side information in the transmitter.

A modified genetic algorithm PTS technique with error correction for PAPR reduction in OFDM systems

This paper proposes a novel peak-to-average power ratio (PAPR) reduction method with low complexity by combining the RM-PTS scheme with the PCGA-PTS scheme, called RM-PCGA-PTS. The RM-PTS scheme not only the transmitted signal has error correction capability but also the transmitter has no need to transmit side information. However, one major drawback of the RM-PTS scheme is high computational loads which also occur in the PTS scheme for finding the transmitted signal with minimum PAPR out. Therefore, this paper investigates a suboptimal PAPR reduction method with low computational loads by using the improved genetic algorithm used the partheno-crossover operator (PCGA) as the selection mechanism of RM-PTS scheme. The GA-PTS scheme is an active PAPR reduction method, which has better PAPR performance than the GD-PTS scheme and has lower computational load than the PTS scheme and the GD-PTS scheme. Note that the GA-PTS scheme has no error correction capability and is a suboptimal PAPR reduction method. Based on the same computational loads, the RM-PCGA-PTS scheme with natural ordering has better PAPR performance than the GA-PTS scheme with adjacent partition in simulation results.

A suboptimal embedding algorithm with low complexity for binary data hiding

A novel suboptimal hiding algorithm for binary data based on weight approximation embedding, WAE, is proposed. Given a specified embedding rate, this algorithm exhibits an advantage of efficient binary embedding with reduced embedding complexity. The suboptimal WAE algorithm performs an embedding procedure through a parity check matrix. The optimal embedding based on maximal likelihood algorithm aims to locate the coset leader to minimize the embedding distortion. On the contrary, the WAE algorithm looks for a target vector close to the coset leader in an efficiently iterative manner. Given an linear embedding code C(n, k), the embedding complexity using the optimal algorithm is O(2k), while the complexity in the suboptimal WAE is reduced to O(sk) where s is the average iterations.