Efficient unequal error protection for online fountain codes

In this paper,an efficient unequal error protection(UEP)scheme for online fountain codes is proposed.In the buildup phase,the traversing-selection strategy is proposed to select the most important symbols(MIS).Then,in the completion phase,the weighted-selection strategy is applied to provide low overhead.The performance of the proposed scheme is analyzed and compared with the existing UEP online fountain scheme.Simulation results show that in terms of MIS and the least important symbols(LIS),when the bit error ratio is 10-4,the proposed scheme can achieve 85%and 31.58%overhead reduction,respectively.

Joint Network and Fountain Codes Design for RelayAssisted Multi-User System

In relay-assisted multi-user system, relay coding is important to enhance the robustness and reliability of cooperative transmission. For better adaptability and efficiency, two joint network and fountain coding(JNFC) schemes are proposed. When the condition of all direct channels is worse, JNFC scheme based on distributed LT(DLT) codes is used. Otherwise, JNFC scheme based on multi-dimensional LT(MD-LT) codes is suited. For both two above-mentioned schemes, the united degree distribution design method for short-length fountain codes is proposed. For the latter scheme, MD-LT codes are proposed for equal error protection(EEP) of each user. Simulation results and analysis show that the united degree distribution need less decoding overhead compared with other degree distribution for short-length fountain codes. And then, all users are protected equally in despite of asymmetric uplinks.

A NOVEL APPROACH OF LIMITED-RANDOMNESS FOUNTAIN CODES IN DEEP SPACE COMMUNICATION

Digital fountain is applied into deep space communication for its rateless and non-feedback forward error correction.However,the long code length and encoding overhead are confined factors to guarantee a considerable recovery probability as power and buffer-limited equipment in deep space environment.At the same time,the typical fountain decoding is sub-optimum decoding algorithm.We propose a new approach,Dependent Sequences Compensation Algorithm(DSCA),to improve the encoding efficiency by restricting the randomness in fountain encoding.While decoding algorithm is also optimized by redundant information in stopping set.The results show that the optimized method can obtain a 10-4 decoding failure rate with overhead under 0.20 for code length 500,which indicates the usefulness of the proposed approach in deep space communication.

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.

A Feedback Scheme for Fountain Codes Based Transport Protocol in Space Communications

This paper proposed a practical- feedback scheme for fountain codes based transportprotocol in space communications. In the proposed scheme, the sender is signaled by two types of acknowledgment （ACK） packets.Before decoding, packet loss probability isestimated on the receiver side and encapsulated intoa soft ACKand sent to the sender.After decoding,decoding results are encapsulated into hard ACKsandsent to the sender. There are two contributionsin the proposed scheme： 1. Empl layer calculation instead layer statistics to estimate oying physical of application the packet loss probability of space channel, which can improvethe accuracy and practicality. 2. A cascade overhead-failure probability relationship between the sender and the receiver has been analyzed to help determine the exact numberof packetsneeded byfountain decoding.Simulations show that for space communications,compared with the existing space transport protocols, fountain codes based transport protoeolwith the proposed schemecan not only ensure transmission reliability, but also greatly improvelink utilization.

Anti-Jamming Performance of Fountain Coded Differential Frequency Hopping Systems in AWGN

Based on the anti-jamming performance of differential frequency hopping （DFH） systems in Additive White Gaussian Noise （AWGN） channel, Fountain code is introduced to the DFH systems as the outer error correcting code in this paper to investigate the improvements against partial-band jamming over AWGN channel. The performance of Fountain coded DFH is theoretically analyzed and numerically simulated. The total frequency of hopping in the simulation is 16, and results show that, on one hand, when exact jamming state information （JSI） is available, and the number of jamming frequency is n= 16, the bit error rate （BER） of 10~3 is achieved with the signal to interference ratio （SIR） approximately 7.5 dB over AWGN channel, and the performance improves about 1-1.5dB compared with the no-coded system. When the number of jamming frequency is n=2, the performance increases 15-17dB. On the other hand, when JSI is unavailable, a joint JSI estimation and decoding algorithm is proposed. The BER of 10 3 is achieved with jamming-frequency n 16, SIR=8dB and signal noise ratio （SNR） 10dB over AWGN channel. It＇s proved that this algorithm provides robust anti-jamming pertbrmance even without JSI. The anti-jamming performance of Fountain coded DFH systems is obviously superior to no-coded DFH systems.

Performance Analysis and Parameter Optimizing Rules of LT Codes

As a new class of forward error correcting encoding algorithm,Luby Transform codes are suitable for the erasure channel environment based on the packet communication.The encoding,decoding algorithms and the implementation of LT codes are summarized in the paper.Meanwhile simulations of the ideal soliton distribution and robust soliton distribution are conducted to evaluate the performance of LT codes in terms of successful decoding probability,mean degree and decoding time over the erasure channel.The parameter optimization rules of LT codes are deeply discussed and proposed in the paper.The research results are of great practical importance for improving the real time performance in the erasure correction applications.

Implementation of LT codes based on chaos

Fountain codes provide an efficient way to transfer information over erasure channels like the Internet. LT codes are the first codes fully realizing the digital fountain concept. They are asymptotically optimal rateless erasure codes with highly efficient encoding and decoding algorithms. In theory, for each encoding symbol of LT codes, its degree is randomly chosen according to a predetermined degree distribution, and its neighbours used to generate that encoding symbol are chosen uniformly at random. Practical implementation of LT codes usually realizes the randomness through pseudo-randomness number generator like linear congruential method. This paper applies the pseudo-randomness of chaotic sequence in the implementation of LT codes. Two Kent chaotic maps are used to determine the degree and neighbour（s） of each encoding symbol. It is shown that the implemented LT codes based on chaos perform better than the LT codes implemented by the traditional pseudo-randomness number generator.

Feedback-based unequal error protection fountain code over device-to-device broadcast

To enhance encoding efficiency, an unequal error protection （UEP） broadcast scheme based on one additional feedback is proposed. Different from the equal probability selection for source packets in traditional fountain encoding, the proposed scheme calculates the packet loss ratio （PLR） according to the feedback results in systematic broadcast phase （SBP） and then optimizes the selection probability for source packets to guarantee higher level error protection for those source packets with larger PLRs. Thus the amount of unnecessarily redundant encoded packets during encoding broadcast phase （EBP） is decreased significantly. Numerical results show that the proposed scheme can recover 60% more packets than the traditional non-feedback broadcast scheme at the ex- pense of tolerably only one feedback procedure.

Performance Enhancement and Utility Maximization for TCP in Wireless Mesh Networks

In Wireless Mesh Networks (WMNs),the performance of conventional TCP significantly deteriorates due to the unreliable wireless channel.To enhance TCP performance in WMNs,TCP/LT is proposed in this paper.It introduces fountain codes into packet reorganization in the protocol stack of mesh gateways and mesh clients.Furthermore,it is compatible with conventional TCP.Regarded as a Performance Enhancement Proxies (PEP),a mesh gateway buffers TCP packets into several blocks.It simultaneously processes them by using fountain encoders and then sends them to mesh clients.Apart from the improvement of the throughput of a unitary TCP flow,the entire network utility maximization can also be ensured by adjusting the scale of coding blocks for each TCP flow adaptively.Simulations show that TCP/LT presents high throughput gains over single TCP in lossy links of WMNs while preserving the fairness for multiple TCPs.As losses increase,the transmission delay of TCP/LT experiences a slow linear growth in contrast to the exponential growth of TCP.

AeroMTP:A fountain code-based multipath transport protocol for airborne networks

Airborne networks（ANs） are special types of ad hoc networks that can be used to enhance situational awareness, flight coordination and flight efficiency in civil and military aviation.Compared to ground networks, ANs have some unique attributes including high node mobility, frequent topology changes, mechanical and aerodynamic constrains, strict safety requirements and harsh communication environment.Thus, the performance of conventional transmission control protocol（TCP） will be dramatically degraded in ANs.Aircraft commonly have two or more heterogeneous network interfaces which offer an opportunity to form multiple communication paths between any two nodes in ANs.To satisfy the communication requirements in ANs, we propose aeronautical multipath transport protocol（Aero MTP） for ANs, which effectively utilizes the available bandwidth and diversity provided by heterogeneous wireless paths.Aero MTP uses fountain codes as forward error correction（FEC） codes to recover from data loss and deploys a TCP-friendly rate-based congestion control mechanism for each path.Moreover, we design a packet allocation algorithm based on optimization to minimize the delivery time of blocks.The performance of Aero MTP is evaluated through OMNe T＋＋ simulations under a variety of test scenarios.Simulations demonstrate that Aero MTP is of great potential to be applied to ANs.

Dynamic(2, 3) Threshold Quantum Secret Sharing of Secure Direct Communication

In this paper, we show that a(2, 3) discrete variable threshold quantum secret sharing scheme of secure direct communication can be achieved based on recurrence using the same devices as in BB84. The scheme is devised by first placing the shares of smaller secret pieces into the shares of the largest secret piece, converting the shares of the largest secret piece into corresponding quantum state sequences, inserting nonorthogonal state particles into the quantum state sequences with the purpose of detecting eavesdropping, and finally sending the new quantum state sequences to the three participants respectively. Consequently, every particle can on average carry up to 1.5-bit messages due to the use of recurrence. The control codes are randomly prepared using the way to generate fountain codes with pre-shared source codes between Alice and Bob, making three participants can detect eavesdropping by themselves without sending classical messages to Alice. Due to the flexible encoding, our scheme is also dynamic, which means that it allows the participants to join and leave freely.

Serial decoding of rateless code over noisy channels

Rateless code usually generates a potentially infinite number of coded packets at the encoder and collects enough packets at the decoder to ensure reliable recovery of multiple information packets.The conventional rateless decoder usually works in a parallel manner which needs to initiate a new belief propagation (BP) decoding procedure upon each newly received collection of coded packets,thereby resulting in prohibitive decoding complexity in practice.In this paper,we present a novel serial decoding algorithm,i.e.,the serial storage belief propagation (SS BP) algorithm,for rateless codes over noisy channels.Specifically,upon receiving a new group of coded packets,the decoder initiates a new attempt to decode all the packets received so far,using the results of the previous attempt as initial input.Moreover,in each iteration of the new attempt,the decoder serially propagates the messages group by group from the most recent one to the earliest one.In this way,the newly updated messages can be propagated faster,expediting the recovery of information packets.In addition,the proposed serial decoding algorithm has significantly lower complexity than the existing parallel decoding algorithms.Simulation results validate its effectiveness in AWGN,Rayleigh,and Rician fading channels.