Novel joint encoding/decoding algorithms of fountain codes for underwater acoustic communication

Fountain codes are considered to be a promising coding technique in underwater acoustic communication（UAC） which is challenged with the unique propagation features of the underwater acoustic channel and the harsh marine environment. And Luby transform（LT） codes are the first codes fully realizing the digital fountain concept. However, in conventional LT encoding/decoding algorithms, due to the imperfect coverage（IC） of input symbols and short cycles in the generator matrix, stopping sets would occur and terminate the decoding. Thus, the recovery probability is reduced,high coding overhead is required and decoding delay is increased.These issues would be disadvantages while applying LT codes in underwater acoustic communication. Aimed at solving those issues, novel encoding/decoding algorithms are proposed. First,a doping and non-uniform selecting（DNS） encoding algorithm is proposed to solve the IC and the generation of short cycles problems. And this can reduce the probability of stopping sets occur during decoding. Second, a hybrid on the fly Gaussian elimination and belief propagation（OFG-BP） decoding algorithm is designed to reduce the decoding delay and efficiently utilize the information of stopping sets. Comparisons via Monte Carlo simulation confirm that the proposed schemes could achieve better overall decoding performances in comparison with conventional schemes.

Improving Low Bitrate Video Coding via Computation Incorporating A Priori Information

The growing number of mobile users, as well as the diversification in types of services have resulted in increasing demands for wireless network bandwidth in recent years. Although evolving transmission techniques are able to enlarge the network capacity to some degree, they still cannot satisfy the requirements of mobile users. Meanwhile, following Moore's Law, the data processing capabilities of mobile user terminals are continuously improving. In this paper, we explore possible methods of trading strong computational power at wireless terminals for transmission efficiency of communications. Taking the specific scenario of wireless video conversation, we propose a model-based video coding scheme by learning the structures in multimedia contents. Benefiting from both strong computing capability and pre-learned model priors, only low-dimensional parameters need to be transmitted; and the intact multimedia contents can also be reconstructed at the receivers in real-time. Experiment results indicate that, compared to conventional video codecs, the proposed scheme significantly reduces the data rate with the aid of computational capability at wireless terminals.

Design and analysis of a network coding algorithm for ad hoc networks

Network coding is proved to have advantages in both wireline and wireless networks. Especially, appropriate network coding schemes are programmed for underlined networks. Considering the feature of strong node mobility in aviation communication networks, a hop-by-hop network coding algorithm based on ad hoc networks was proposed. Compared with COPE-like network coding algorithms, the proposed algorithm does not require overhearing from other nodes, which meets confidentiality requirements of aviation communication networks. Meanwhile, it does save resource consumption and promise less processing delay. To analyze the performance of the network coding algorithm in scalable networks with different traffic models, a typical network was built in a network simulator, through which receiving accuracy rate and receiving delay were both examined.The simulation results indicate that, by virtue of network coding, the proposed algorithm works well and improves performance significantly. More specifically, it has better performance in enhancing receiving accuracy rate and reducing receiving delay, as compared with any of the traditional networks without coding. It was applied to both symmetric and asymmetric traffic flows and, in particular, it achieves much better performance when the network scale becomes larger. Therefore, this algorithm has great potentials in large-scale multi-hop aviation communication networks.

Efficient Helicopter-Satellite Communication Scheme Based on Check-Hybrid LDPC Coding

When implementing helicopter-satellite communications, periodical interruption of the received signal is a challenging problem because the communication antenna is intermittently blocked by the rotating blades of the helicopter. The helicopter-satellite channel model and the Forward Error Control（FEC） coding countermeasure are presented in this paper. On the basis of this model, Check-Hybrid（CH） Low-Density Parity-Check（LDPC）codes are designed to mitigate the periodical blockage over the helicopter-satellite channels. The CH-LDPC code is derived by replacing part of single parity-check code constraints in a Quasi-Cyclic LDPC（QC-LDPC） code by using more powerful linear block code constraints. In particular, a method of optimizing the CH-LDPC code ensemble by searching the best matching component code among a variety of linear block codes using extrinsic information transfer charts is proposed. Simulation results show that, the CH-LDPC coding scheme designed for the helicopter-satellite channels in this paper achieves more than 25% bandwidth efficiency improvement, compared with the FEC scheme that uses QC-LDPC codes.

Practical Polar Code Construction For Degraded Multiple-Relay Networks

In this paper, based on the characteristics of polar codes, a new decode-and-forward strategy called generalized partial information relaying protocol is proposed for degraded multiple-relay networks with orthogonal receiver components(MRNORCs). In such a protocol, with the help of partial information from previous nodes, each relay node tries to recover the received source message and re-encodes part of the decoded message for transmission to satisfy the decoding requirements for the following relay node or the destination node. In order to construct practical polar codes, the nested structures are developed based on this protocol and the information sets corresponding to the partial messages forwarded are also calculated. The proposed scheme is proved to be capable of achieving the theoretical capacity of the degraded MRN-ORCs while still retains the low-complexity feature of polar codes. We perform simulations to testify the practicability of the proposed scheme and compare polar codes by using successive-cancellation list decoder(SCLD) with traditional low-density parity-check(LDPC) codes. The results show that the obtained polar codes provide significant gain.

Parametric array differential Pattern time delay shift coding underwater acoustic communication in the under-ice environment

In order to meet the demands of underwater acoustic communication in under ice environment,a differential Pattern time delay shift coding underwater acoustic communication method based on parametric array is introduced in this paper.The under ice underwater acoustic channel is characterized by heavy multipath transmission.Under this model,a parametric array emission method of Pattern signal is derived and the system performance is analyzed.A broadband low frequency sound waves with narrow beam-pattern,which will reduce the interface reflections and suppress the effects of multipath transmission,can be obtained by the emission method.The Songhua River under ice trial results show that there is an anti-multipath property and a higher data rate in the under-ice acoustic channel in proposed approach.

Deep space multi-file delivery protocol based on LT codes

A deep space multi-file delivery protocol（DSMDP） based on LT codes is proposed to reduce the influence of long delay and a high bit error rate（BER） in deep space communication. The protocol increases sending redundancy by LT codes to improve the success rate of file delivery, and adopts different protective strategies for different situations of packet loss. At the same time, the multi-file united delivery strategy is adopted to make full use of the retransmission time to reduce the end-toend transmission delay. Furthermore, the protocol determines the quantity of encoded packets according to the feedback for controlling redundancy. The simulation results show that the proposed protocol can significantly reduce the transmission delay of files, which would be effectively suitable for deep space communication environment of high BER and long delay.

Windowed overlapped frequency domain block filtering approach for direct sequence signal acquisition

This study applies a windowed frequency domain overlapped block filtering approach to acquire direct sequence signals. As a novel viewpoint, the windows not only allow pulse shaping without front-end pulse-shaping filter, but also increase the performance of the spectrum sensing unit, which can efficiently be implemented into this frequency domain receiver and may further be used for spectrum sensing in cognitive radios or narrowband interference cancellation in military radios. The proposed receiver is applicable for the initial time synchroni- zation of different signals containing a preamble. These signals include single carrier, constant envelope single carder, multicarrier, and even generalized multicarrier signals, making the proposed receiver structure a universal unit. Furthermore, the receiver can be used to perform filtering with long codes and compute the sliding correlation of an unknown periodic preamble. The receiver can further be modified to handle large Doppler shifts. We will also demonstrate herein the computational complexity and analysis of the acquisition performance in Rayleigh and Rician fading channels.

Multilevel photon communication on BPPM with convolutional coding

Multilevel photon combined with binary pulse position modulation(BPPM)(Manchester pulsed signals), is introduced in this letter. Initially, error probability derivation and explanation for four-level photon communications with that BPPM is presented. Next, the 2-level photon communications matching with BPPM is proposed. For performance comparison, it is done with that the conventional scheme by fxing the background noise and also increasing number of photon per slot. Successfully with applying convolutional coding for system improving, the proposed multilevel photon on BPPM with this coding scheme achieves higher gain. Finally, this work also benefts to improving for further performance when considering with multilevel error control coding as well.

A study on pattern time delay shift coding underwater acoustic communication

The high rate digital acoustic communication technique for horizontal channels has been studied in this article. It is called as 'Pattern Time Delay Shift Coding (PDS) communication system.' The aim of the PDS is to improve the quality of communication in shallow water. The open water experiments shoe that at the condition of 2 kHz bandwidth, the communication rate is more than 300 bit/s and error rate is at the level of 10-4. The details of PDS technique will be shown, including: principle of PDS coding, the model of Anti-multipath illterference and open water experimenis

Iterative Noncoherent Block Detection of Coded MPSK for Cooperative Relay Systems

Maximum likelihood(ML) noncoherent block detection techniques are investigated for block-coded MPSK modulation in cooperative decode-and-forward relay systems over slow fading channels.A decision-directed iterative Viterbi algorithm(IVA) is derived for a suboptimal ML noncoherent detection.Simulation results show that the IVA can approach the error performances of the exhaustive detection method but at a lower complexity.

Log Likelihood Ratio-Based Relaying for Distributed Turbo Codes

A distributed turbo codes（ DTC） scheme with log likelihood ratio（ LLR）-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the relay,where imperfect decoding occurs,is considered in the proposed scheme. By employing a LLR-based threshold at the relay in the proposed scheme,the reliability of decoder-LLRs can be measured. As a result,only reliable symbols will be forwarded to the destination and a maximum ratio combiner（ MRC） is used to combine signals received from both the source and the relay. In order to obtain the optimal threshold at the relay,an equivalent model of decoderLLRs is investigated,so as to derive the expression of the bit error probability（ BEP） of the proposed scheme under binary phase shift keying（ BPSK） modulation. Simulation results demonstrate that the proposed scheme can effectively mitigate error propagation at the relay and also outperforms other existing methods.

A LARGE CLASS OF BINARY ZCZ SEQUENCE FAMILIES CONSTRUCTED BY PERIOD DOUBLING

In an Approximately Synchronized Code Division Multiple Access (AS-CDMA) commu-nication system,a family with large number of Zero Correlation Zone (ZCZ) sequences is desired,which can satisfy the rapid increase of users. This paper presents a method to generate a (2L ,2M ,Zc' z )-ZCZsequence family from an original (L ,M ,Z cz)-ZCZsequence family,where Z c' z =Zcz if Z czis even and Z c' z = Zcz 1if Z czis odd. This method can also recursively act on a ZCZ sequence family to construct a series of ZCZ sequence families with large sequence number and zero correlation zone length identical to or one less than that of original ZCZ sequences.

Wireless sensing system for environmental humidity and temperature monitoring

Aiming at the actual demand for monitoring environmental information,a wireless sensing system for temperature and relative humidity(RH)monitoring based on radio frequency(RF)technology and mobile network was designed.This paper introduces the architecture of the system.The system uses AVR micro controller unit(MCU),KYL-1020U RF module and SHT71 to complete real-time temperature and humidity monitoring,and uses SIM900A module to realize remote alarming and monitoring with short message system(SMS)through global system for mobile communication(GSM).Experimental results show that the designed system has good stability of measurement and real-time performance,and it can be used in some small temperature and humidity monitoring occasions.