Liuguo Yin

LDPC-based joint source-channel coding scheme for multimedia communications

Joint source-channel coding schemes have been proven to be effective ways for reliable multimedia communications. In this paper, we develop a joint source-channel coding scheme that well combines the hidden Markov source (HMS) estimation and the powerful low-density parity-check (LDPC) codes with an iterative estimation/decoding scheme. With this coding method, the source redundancy could be accurately extracted by the hidden Markov estimation without using any priori information about the source. Moreover, the interleaver that is likely used to separate the source coding and channel coding is exempted by exploiting the randomizing property of the LDPC codes, while the channel decoding procedure may be implemented in parallel, resulting in good performance with a fairly low decoding complexity and delay. Simulation results have shown that the proposed scheme may achieve a much better performance than that of the standard coding scheme over the binary input additive white Gaussian noise (BIAWGN) channels.

Design of irregular LDPC codec on a single chip FPGA

A novel implementation of irregular low density parity check (LDPC) codec on a single chip Xilinx FPGA is presented in this paper. The encoder and decoder are accomplished by partial parallel architectures with very low complexity. Specifically, details including the decoder and encoder structures, memory management, and required computation units to realize the variable/check node decoding and the parity-check bits generation are discussed. It is verified that the error-correcting capability of the codes with the proposed scheme is kept the same as that by random generation method, while highly parallel encoding/decoding scheme may be realized with ease. Thereby, the proposed design approach for the complex LDPC codec is very promising for real applications.

UEP Video Transmission Based on Dynamic Resource Allocation in MIMO OFDM System

This paper presents a novel unequal error protection (UEP) video transmission scheme based on dynamic resource allocation in a MIMO-OFDM system in order to improve the video transmission performance over wideband wireless channels. In this new scheme, a low density parity code (LDPC) is combined with a complexity reduced power reallocation algorithm to utilize the excess powers which margin from the powers necessary to meet the modulation level selected under a certain BER constraint. Furthermore, by taking full advantage of the residual excess powers, unequal error protection on important bits of video streams is provided by the LDPC code. Accordingly, the transmission efficiency and quality are both increased. Simulation results have shown that the proposed scheme may achieve great improvement in both systems with or without perfect channel estimation.

CodeHop: physical layer error correction and encryption with LDPC-based code hopping

This paper proposes a novel scheme named CodeHop, which provides both information reliability and security using code hop ping based on low-density parity-check (LDPC) codes. In contrast to traditional systems that perform error correction and encryption at different layers, CodeHop combines these two operations into a single step at physical layer, such that each plaintext message is jointly encoded and encrypted by a hopping parity-check matrix. According to a pseudo-random number generator (PRNG), the hopping matrix may rapidly switch among a sequence of LDPC parity-check matrices, which is randomly generated by a structured-random protograph expanding technique. Simulations show that reliable communication can be achieved by CodeHop with good error-correcting performance. In the meantime, CodeHop may improve the security of traditional systems such as GSM. Taking the A5/1 stream cipher used in GSM as the PRNG, it is shown that CodeHop is resistant to existing chosen-plaintext attacks that break A5/1 cipher already. Moreover, the security of CodeHop will be enhanced in the presence of channel errors as well.

Design of Efficient Joint eIRA-Coded MSK Modulation Systems for Space Communications

An efficient scheme of extended irregular repeat-accumulate (eIRA-) coded minimum shift keying (MSK) is presented. Based on an extrinsic information transfer (EXIT) chart, it is designed as an eIRA code, incorporating a continuous-phase encoder (CPE) decomposed from MSK. Our scheme and a contrasting scheme of another eIRA-coded MSK are simulated in an additive white Gaussian noise (AWGN) channel. Simulation results show that our scheme outperforms the contrasting scheme by about 2 dB at a bit error rate (BER) of and has the same performance of an optimal eIRA-coded binary phase shift keying (BPSK). In addition, our scheme obtains lower complexity and less decoding latency because all differential encoders in the eIRA code are eliminated, while adding some differential decoders. Thus, the two-level Tanner graph-based decoding in the contrasting scheme is reduced. Therefore, the proposed scheme can be efficiently applied to satellite and deep space communications.

Combined hidden Markov source estimation and low‐density parity‐check coding: a novel joint source–channel coding scheme for multimedia communications

Joint source–channel coding schemes have been proven to be very effective for reliable multimedia communications. In this paper, we develop a joint source–channel coding scheme that combines the hidden Markov source (HMS) estimation and the low-density parity-check (LDPC) codes with an iterative estimation/decoding scheme. With this innovative combination, multimedia source redundancy could be accurately extracted by the hidden Markov estimation without any a priori information about the source. Moreover, the interleaver that is usually used to separate the source coding and channel coding can be avoided by exploiting the randomizing property of the LDPC codes. Furthermore, the channel decoding procedure may be implemented in parallel, resulting in good performance with a fairly low decoding complexity and delay. Simulation results have shown that the proposed scheme can achieve much better performance than the standard coding scheme over the binary input additive white Gaussian noise (BIAWGN) channels. Copyright

An Energy-Efficient Routing Protocol for Event-Driven Dense Wireless Sensor Networks

The routing energy efficiency of a wireless sensor network is a crucial issue for the network lifetime. In this article, we propose MICRO (MInimum Cost Routing with Optimized data fusion), an energy-efficient routing protocol for event-driven dense wireless sensor networks. The proposed routing protocol is an improvement over the formerly proposed LEACH and PEGASIS protocol, which is designed to be implemented mainly with node computations rather than mainly with node communications. Moreover, in the routing computation the proposed scheme exploits a new cost function for energy balancing among sensor nodes, and uses an iterative scheme with optimized data fusions to compute the minimum-cost route for each event-detecting sensor node. Compared to the PEGASIS routing protocol, MICRO substantially improves the energy-efficiency of each route, by optimizing the trade-off between minimization of the total energy consumption of each route and the balancing of the energy state of each sensor node. It is demonstrated that the proposed protocol is able to outperform the LEACH and the PEGASIS protocols with respect to network lifetime by 100–300% and 10–100%, respectively.

An LDPC coded MIMO-OFDM system with simple detection and channel estimation scheme

Multiinput multioutput (MIMO) technology may be used to increase the wireless transmission rate without increasing transmission power or bandwidth. The complex detection and channel estimation algorithm are often used to achieve an acceptable performance. In this paper, irregular low density parity check (LDPC) codes are well combined with the zero-forcing (ZF) detection algorithm, leading to a novel soft-decision detection and channel estimation scheme. In particular, the implementation complexity is significantly decreased since most likely the channel estimator works without pilots, while the detector decouples a multidimensional symbol detection into multiple one-dimensional symbol detections. Simulation results show that the performance of the proposed system may be greatly improved compared with that of system with convolutional code.

Efficient encoding of cycle codes on graphs with large girths

Low-density parity-check (LDPC) codes of column weight two, also called cycle codes, can be constructed based on connected simple graphs. In this paper, efficiently encodable cycle codes and modified Repeat-Accumulate codes based on Hamiltonian graphs with large girths are devised. Specifically, the Hamiltonian property of the graphs is exploited to obtain efficient encoder structures and a concise description for the Hamiltonian graph named LCF (Lederberg-Coxeter-Frucht) notation is used to reduce the complexity of the encoders, especially the storage requirement. Then, using the Hamiltonian property and the LCF notation, structured cycle codes with large girths and low encoding complexity are devised. Simulation results also reveal that the proposed structured codes exhibit better performance compared with other structured cycle codes.

Energy-efficient route optimization for adaptive MPSK-based wireless sensor networks

We study a certain route configuration problem via optimization theory. We consider the optimal bit error rate (BER) and transmission rate allocations on each hop, subject to overall BER and delay constraints for a designated route. The pivot of the problem lies in the delay constraint, which divides the problem into two cases—the loose and the tight delay case. In the former, analytical solutions are obtained by applying the Karush-Kuhn-Tucker (KKT) theorem. Specifically, we discover in this case that for a given target BER, the optimum solutions are only related to the hop lengths in the route. When the delay constraint is tight, a mapping can be used to reduce the dimension of the problem by a factor of two; a numerical optimization algorithm has to be used to find the optimum. Simulation results show that by optimally configuring a chosen route, substantial energy savings could be obtained, especially under tight delay constraints. Simulation also reveals that a performance limit is reached as the number of hops increases. A parameter determining this limit is defined, and physical explanations are given accordingly.