Rateless Codes Research Articles

Dynamic Coded Cooperation With Incremental Redundancy: Throughput and Diversity-Multiplexing Tradeoff Analysis

In cooperative communications, dynamic decode-and-forward transmission with rateless coding ( RC-DDF ) is most efficient in reaching/approaching channel capacity. However, it entails strict carrier synchronization among the source, relay and destination, making it hard to implement in practice. To remove the limitation, we propose a scheme named dynamic coded cooperation with incremental redundancy ( DCCIR ) where nodes transmit alternatively and thus no strict carrier synchronization is needed. Its performance is investigated in terms of both throughput and diversity-multiplexing tradeoff (DMT). Moreover, we present a subframe-based implementation structure for DCCIR ( sub-DCCIR ) to obtain the DMT of DCCIR . The results reveal performance advantages of DCCIR or sub-DCCIR over several existing schemes and its approximation to RC-DDF .

Analysis and Design of Systematic Rateless Codes in FH/BFSK System with Interference

The asymptotic analysis of systematic rateless codes in frequency hopping (FH) systems with interference is first provided using discretized density evolution (DDE) and compared with the traditional fixed-rate scheme. A simplified analysis with Gaussian assumption of initial message is proposed in the worst case of interference, which has much lower complexity and provides a very close result to DDE. Based on this simplified analysis, the linear programming is employed to design rateless codes and the simulation results on partial-band interference channels show that the optimized codes have more powerful antijamming performance than the codes originally designed for conventional systems.

Rateless-Code-Based Secure Cooperative Transmission Scheme for Industrial IoT

Integrating the Internet-of-Things (IoT) paradigm with industrial wireless sensor networks (IWSNs) has led to a technological evolution known as Industrial IoT (IIoT). To ensure reliable, secure, and low-latency communication in IIoT applications like healthcare, we use rateless codes (RCs) for forward error correction (FEC) at the physical layer (PHY) in a cooperative delay-constrainted environment. Probability of violation (Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vio</sub> ) is used as a performance metric which consists of: 1) reliability outage probability, i.e., the probability with which the information cannot be successfully decoded within the time constraint T and 2) information intercept probability, which reflects the secrecy performance. Since RC can adjust the rate on the fly, we analyze the performance when relay transmits a fraction of the message and the receiver does energy accumulation (EA). We derive a closed-form expression of Prvio in a single-relay system at a high signal-to-noise ratio (SNR) when the receiver either accumulates energy or mutual information (MI) from the received signals. Furthermore, Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">vio</sub> of various relay selection schemes is evaluated in a multirelay system. Such kind of analysis in which relay selection is done using RC for PHY-FEC is first of its kind and it is compared to fixed-rate codes. Overall, results show the significant benefits of PHY-RC for guaranteeing the Quality-of-Service (QoS) requirements essential in IIoT applications.

Rateless codes with adaptive parity allocation for satellite systems

SummaryIn this paper, we propose efficient parity allocation schemes when rateless codes are used in satellite communication systems in conjunction with an adaptive coding and modulation (ACM) scheme. ACM schemes are widely used in modern satellite communication systems to maintain the required error rate performance under channel impairment (such as rain fading observed in high‐frequency bands). The performance enhancement of ACM can be achieved by providing a good channel prediction and mode allocation method. In the case of a channel prediction or allocation error, rateless codes can be used as an effective means of retransmission to compensate for the performance degradation. After investigating the performance behaviour of rateless codes combined with ACM, we derive a mathematical formula to find the optimum parity length of the rateless code to be retransmitted to satisfy the target performance requirements. Simulation results described in this paper show that the proposed method can be used to enhance the error performance as well as spectral efficiency.

Rateless Coding Schemes Using Polar Codes: Truly “No” Rates?

In this paper, aiming to achieve rate adaptation for the rateless coding (RC) schemes of polar codes, we explore their throughput efficiency and optimize a series of rates that are set in two types of RC schemes. First, the RC scheme with incremental freezing (IF-RC) decoding is analyzed from the perspective of rate matching. Then, a new RC scheme based on extending codes and copying information bits (termed EC-RC) is developed in detail. Moreover, to overcome the drawback of an undefined rate sequence in RC transmission, rate optimization strategies are separately proposed for both IF-RC and EC-RC by maximizing throughput efficiency with dynamic programming. Closed-form expressions of throughput for these two RC methods are derived as a consequence. The optimization procedure can be realized in practice with low complexity. Finally, the numerical results and analyses demonstrate that rate adaptation of polar-coded RC can be achieved along with maximum throughput by our proposed strategies over both AWGN channels and Rayleigh fading channels. The two optimized RC schemes provide higher throughput efficiency than other existing rateless codes.

On the Age of Information in Wireless Networks Using Rateless Codes

The information freshness, quantified by the emerging idea of Age of Information (AoI), has recently received widespread attentions from both academia and industry. However, most prior works on AoI considered a single source-destination pair and provided the performance analysis merely through queueing-theoretic models, which do not lend themselves to the analysis of large-scale wireless networks. This paper focuses on the AoI analysis in a large-scale setting using random spatial models in stochastic geometry. Specifically, we first adopt rateless coding for packet delivery to improve the transmission reliability while reducing the transmission delay. Then, to quantify the enhancement of the information freshness by rateless coding, we derive the average peak age of information (PAoI) in Poisson bipolar and cellular networks, which characterizes the maximum value of AoI immediately before an update packet is received accounting for the spatial variation of network nodes and temporal dynamics of service packets. With these results, we further give the conditions that make the average PAoI to be finite in each type of the network. Numerical results show the significant benefits of rateless codes relative to the commonly used fixed-rate codes in terms of the PAoI and the feasible region of system parameters such as the traffic arrival rate, transmit probability, etc., in Poisson bipolar and cellular networks.

A Study on the Application of Rateless Coding in Non-Cellular MIMO Systems for Machine-Type Communication

For industrial applications, communication requirements are considerably different than in most other domains. Whereas in office environments and the consumer market networks are designed towards the maximum throughput, in Industry 4.0 scenarios, traffic inficts realtime requirements, demands particular high reliability and low latency. Industrial applications of the past as well as in most current production facilities are interconnected via cable. Wireless communication in this surrounding is still a big challenge, due to the mentioned communication demands. The high demands on reliability and latency require adaptations both to the MAC layer and to the baseband signal processing of the radio system being used. Of particular importance here is the error protection coding of the radio system, the investigation of which is the subject of the given work. This needs to achieve particularly high reliability but also must not consume too much computation time, while introducing only a reasonable amount of redundancy. In order to strive for this goal, this paper examines the utilization of Fountain codes (which belong to the family of rateless codes) with very short packets (in the order of less than 100 bytes). Investigated is the impact in terms of packet error rate. It is numerically shown that the joint erasure- and error-correction coding outperforms the sole usage of either one coding scheme. Interestingly, this is true in the presence of a Rayleigh channel but also in the presence of an AWGN channel. Finally, the performance of such a method is compared to that of space time block coding.

Performance of Dynamic Time Division Broadcast Protocol with Rateless Coding

Two-way relaying channel (TWRC) improves the throughput of one-way relaying channel through network coding at the relay. Time division broadcast (TDBC) is one typical protocol for TWRC, but with three time slots for one round information exchange leading to throughput loss. To enhance throughput performance, incremental redundancy transmission is usually incorporated into TDBC (i.e., TDBC-IR) by one bit feedback, indicating the successful or failed transmission. Nevertheless, TDBC-IR still suffers in throughput since it cannot fully exploit and adapt to the varying channel dynamics. In the paper, we propose a dynamic TDBC protocol with incremental redundancy in the form of rateless coding (i.e., DTDBC-RC) to fully utilizing the varying channel dynamics. In DTDBC-RC, the two sources first transmit in rateless coding way with given maximum allowable transmission time, and then the relay retransmits or not based on its decoding results. To reveal the advantages of DTDBC-RC, we analyze its performance comprehensively in terms of outage probability, expected rate, and diversity-multiplexing trade-off (DMT). We also present a subslot realization scheme for DTDBC-RC (i.e., sub-DTDBC-RC) since the DMT of DTDBC-RC cannot be obtained directly. Simulation and numerical results show the performance advantage of DTDBC-RC (or sub-DTDBC-RC) over TDBC-IR in terms of both expected rate and DMT.

Rateless Codes for Near-Perfect Load Balancing in Distributed Matrix-Vector Multiplication

Large-scale machine learning and data mining applications require computer systems to perform massive matrix-vector and matrix-matrix multiplication operations that need to be parallelized across multiple nodes. The presence of straggling nodes -- computing nodes that unpredictably slowdown or fail -- is a major bottleneck in such distributed computations. Ideal load balancing strategies that dynamically allocate more tasks to faster nodes require knowledge or monitoring of node speeds as well as the ability to quickly move data. Recently proposed fixed-rate erasure coding strategies can handle unpredictable node slowdown, but they ignore partial work done by straggling nodes thus resulting in a lot of redundant computation. We propose a rateless fountain coding strategy that achieves the best of both worlds -- we prove that its latency is asymptotically equal to ideal load balancing, and it performs asymptotically zero redundant computations. Our idea is to create linear combinations of the m rows of the matrix and assign these encoded rows to different worker nodes. The original matrix-vector product can be decoded as soon as slightly more than m row-vector products are collectively finished by the nodes. We conduct experiments in three computing environments: local parallel computing, Amazon EC2, and Amazon Lambda, which show that rateless coding gives as much as 3x speed-up over uncoded schemes.

Secure Cooperative Transmission in Rateless-Coded Environment Using TAS and Artificial Noise

In this paper, we analyse a secure transmission scheme using rateless codes (RC) in a delay constrained system. By using RC, secrecy is achieved if the legitimate receiver can accumulate required number of packets before an eavesdropper does. To achieve this, we employ transmit antenna selection (TAS) at the base station to improve the main channel and, artificial noise (AN) is generated by the use of a cooperative jammer to degrade the eavesdropper's channel. Quality of violation probability (QVP) which consists of both the delay violation probability and the intercept probability is used as a performance metric. A closed-form expression for QVP is derived. We show that using TAS for reducing QVP is effective only at lower signal to noise ratio (SNR). We also observe that on increasing number of antennas at the source ( $N_{A}$ ) while using TAS along with AN, QVP decreases for delay sensitive services, whereas, in case of delay tolerant applications, increasing $N_{A}$ is effective at low SNR.

Hamming–Luby rateless codes for molecular erasure channels

Nano-scale molecular communications encode digital information into discrete macro-molecules. In many nano-scale systems, due to limited molecular energy, each information symbol is encoded into a small number of molecules. As such, information may be lost in the process of diffusion–advection propagation through complex topologies and membranes. Existing Hamming-distance codes for additive counting noise are not well suited to combat the aforementioned erasure errors. Rateless Luby-Transform (LT) code and cascaded Hamming-LT (Raptor) are suitable for information-loss, however may consume substantially computational energy due to the repeated uses of random number generator and exclusive OR (XOR). In this paper, we design a novel low-complexity erasure combating encoding scheme: the rateless Hamming–Luby Transform code. The proposed rateless code combines the superior efficiency of Hamming codes with the performance guarantee advantage of Luby Transform (LT) codes, therefore can reduce the number of random number generator utilizations. We design an iterative soft decoding scheme via successive cancelation to further improve the performance. Numerical simulations show this new rateless code can provide comparable performance comparing with both standard LT and Raptor codes, while incurring a lower decoder computational complexity, which is useful for the envisaged resources constrained nano-machines.

A digital fountain retrospective

We introduced the concept of a digital fountain as a scalable approach to reliable multicast, realized with fast and practical erasure codes, in a paper published in ACM SIGCOMM '98. This invited editorial, on the occasion of the 50th anniversary of the SIG, reflects on the trajectory of work leading up to our approach, and the numerous developments in the field in the subsequent 21 years. We discuss advances in rateless codes, efficient implementations, applications of digital fountains in distributed storage systems, and connections to invertible Bloom lookup tables.

The End-to-End Performance of Rateless Codes in Poisson Bipolar and Cellular Networks

Rateless coding is a promising forward error correction technique to meet both delay and reliability requirements of emerging wireless applications. However, existing works on rateless codes mostly considered finite networks or ignored the traffic dynamics. In this paper, we present a comprehensive investigation of the end-to-end performance for rateless codes in Poisson bipolar and cellular networks. Specifically, we propose the notion of the end-to-end success probability , which is the success probability given an end-to-end delay requirement, to jointly evaluate the delay performance and transmission reliability of rateless codes. To fully characterize the end-to-end delay, we divide it into two parts, namely the packet waiting time and the transmission time, and provide tractable yet accurate approximations to their statistical distributions. Compared with the previous works, the proposed general framework and the end-to-end performance metric help obtain insights on the role of scheduling, queueing, and coding scheme in practical radio access networks. The approximations are verified to be effective and reliable through simulations. Overall, the results show the significant benefits of rateless codes relative to the fixed-rate codes in terms of the transmission reliability with an end-to-end delay requirement.

Raptor Codes With Descending Order Degrees for AWGN Channels

We propose a novel construction of rateless codes for the additive white Gaussian noise (AWGN) channel with high order quadrature amplitude modulation (QAM). The proposed construction is structurally similar to a Raptor code consisting of an inner Luby transform (LT)-style code and an outer low density parity check (LDPC) code. The main novelty is that the output degree distribution for the LT part is time-varying and the degree of the parity bits decreases with time, parity bits with the same degree are clustered together rather than random, which is totally different from traditional fixed degree distributions. Simulation results with a joint iterative decoding algorithm demonstrate that both the goodput and the bit error rate (BER) performance of our proposed scheme are better than those of newly reported Raptor codes for the AWGN channel in most cases.

Novel Design for Short Analog Fountain Codes

Adaptive coding and modulation in current cellular networks relies on a channel quality indicator fed back from the receiver to the transmitter. The process of acquiring channel state information at the transmitter (CSIT) is estimated to take 5–8 ms. For short-packet transmissions in machine-type communications (MTC), the data transmission of small payloads is estimated to take a fraction of a millisecond, i.e., a fraction of the end to end latency. This is especially problematic for ultra-reliable low-latency communications (URLLC) that require an end-to-end latency of 1 ms only. To this end, self-adaptive coding and modulation, aka rateless coding, is much needed to cater for these stringent requirements. In this letter, a new design is proposed for the recently proposed class of rateless codes, dubbed analog fountain codes (AFC), tailored for short-packet transmissions. The numerical results show no error floors down to block error rates of 10−7, thus meeting the ultra-high reliability requirement of URLLC.

Soft Iterative Decoding Algorithms for Rateless Codes in Satellite Systems

The satellite system is one of the most efficient means for broadcasting due to its wide service coverage as well as the fact that it can provide high data rate services by using high frequency bands. However, there are a number of problems in the satellite system, such as a long round trip delay (RTD) and heterogeneity of the channel conditions of the earth stations. Even though utilizing adaptive coding and modulation (ACM) is almost mandatory for the satellite systems using high frequency bands due to the serious rain fading, the long RTD makes it difficult to quickly respond to channel quality information, resulting in a decrease in the efficiency of ACM. A high heterogeneity of earth stations caused by a wide service coverage also makes it difficult to apply a uniform transmission mode, and thus satellite systems require receiver-dependent transmission modes. A rateless code can be an effective means to compensate for these disadvantages of satellite systems compared to terrestrial wireless systems. This paper presents soft iterative decoding algorithms for efficient application of rateless codes in satellite systems and demonstrates that rateless codes can be effectively used for hybrid automatic repeat request schemes.

Rateless Coded Uplink Transmission Design for Multi-User C-RAN.

Cloud radio access network (C-RAN) is a promising technology for the Internet of Things (IoT). In C-RAN, the remote radio head (RRH) and baseband unit (BBU) in the conventional base station are separated, and each BBU is backward centralized into a virtual BBU pool. In this paper, we consider the uplink transmission for the two-user C-RAN with two RRHs under a block fading channel. A novel rateless coded transmission scheme is designed. During each transmission round, each user keeps transmitting to the RRHs using Raptor code until the BBU pool feeds back an acknowledgement (ACK). With the proposed scheme, each user does not require the instant channel state information, which greatly reduces the system overhead. We also design the quantizer at the RRHs and the iterative multi-user detector and decoder at the BBU pool, based on the belief propagation (BP) algorithm. For the Raptor code applied at each user, we optimize the corresponding output node degree profile, based on extrinsic information transfer (EXIT) analysis for the decoding process at the BBU pool. The resulted degree profiles are optimal in an average sense under all possible channel states. The simulation results show that the rateless coded transmission scheme with the optimized degree profiles outperforms the benchmark degree profile in both bit error rate and average system throughput. Moreover, the achieved performance is close to the theoretical limit.

Multiple Access MmWave Design for UAV-Aided 5G Communications

Unmanned aerial vehicles (UAVs) have tremendous potential to improve wireless network capacity, but are challenging to operate in ultra-dense networks, mainly due to the strong interference received from the dominated lineof- sight channels of the UAVs. By forming multiple highly directional beams, millimeter-wave (mmWave) communication technology allows concurrent user transmissions via beam-division multiple access (BDMA), and thus has emerged as a promising solution to mitigate interference for the fifth generation (5G) UAV communication. However, due to the limited number of beams generated in practical mmWave communication systems, conventional BDMA cannot meet the ever increasing capacity requirement. A new multiple access technique is intensely desired. In this article, we integrate mmWave communication with UAV-aided 5G ultra-dense networks, and design a novel link-adaptive constellation- division multiple access (CoDMA) technique. We discuss key challenges in efficient multiple access technique design, and then investigate design principles on new multiplexing methods and beamwidth optimization for interference management in UAV-aided dynamic networks. We further apply flexible constellation division in rateless codes, and put forward the system-level design of CoMDA with beamwidth adaptation to unleash the multiplexing gain. Finally, we show that our design can successfully enable multiple-user access within a single beam without causing any intra-beam interference while efficiently mitigating interference from adjacent beams. We also demonstrate that the proposed design is adaptive to the UAV network dynamics, and can greatly improve the system throughput.

ICast: Fine-Grained Wireless Video Streaming Over Internet of Intelligent Vehicles

Recent years have witnessed a steep grow in the multimedia-oriented Internet of Things (IoT) over vehicular networks. Huge volume of multimedia traffic generated from the in-built IoT devices should be delivered among vehicles and immediate surroundings in real time. However, as network nodes with higher mobility, vehicles often experience more unpredictable wireless channels. Such time-frequency diversity poses substantial challenges to achieve pervasive and real-time multimedia connectivity. The hurdle lies in the inability of automatically approaching the subcarrier level channel variations in the existing video codecs. With coarse-grained traffic delivery rate, video decoding fails, and intermittent connection occurs. To break this stalemate, we propose a fine-grained wireless video streaming strategy, namely iCast, that intelligently achieves the most appropriate data rate and frame protection for multimedia traffic in highly mobile vehicular environments. The insight of iCast is a simple joint source-channel rateless code. It reaps the benefits of the frequency diversity to provide fine-grained data rate for the channel in conjunction with suitable protection for the source. Our experiments show that, by harnessing frequency diversity in mobile environments, iCast outperforms the existing competitive wireless video delivery schemes by up to 5 dB peak signal-to-noise ratio.

QVP‐based relay selection to improve secrecy for rateless‐codes in delay‐constrained systems

Rateless codes (RCs) have the ability of successfully recovering the message from any subset of the fixed number of encoded symbols, making them a good candidate for delay-tolerant systems. However, most of the applications are delay-constrained. In this study, quality of violation probability (QVP) is used as the performance metric which includes reliability, secrecy, considering delay-constraint conditions. The performance of the RC in the presence of an eavesdropper is studied, and a relay selection technique is used to minimise the QVP in a system with regenerative relays. The authors derive an expression for the QVP when adequate mutual information (MI) is obtained at the receiver, and compares it to the energy accumulation (EA) receiver. Further, based on the direct link channel state information available, relay selection scheme is analysed. They observe that MI accumulation reduces QVP significantly in comparison to the EA. It is also observed that initially on increasing the maximum number of allowed channel usages, the QVP gets reduced and later gets saturated. They observe an improvement in outage probability and intercept probability due to diversity gain. A closed-form expression of QVP for relay selection is determined for the EA and the MI accumulation receiver.