Satellite forward VDES channel modeling and impact on higher-layer performance

VHF data exchange system (VDES) is an emerging maritime communications standard that is meant to provide ship-to-shore, shore-to-ship, and ship-to-ship information services. VDES also includes a satellite component to extend the service coverage also to the high sea. Ships can receive important information via VDES and access this service via satellite when they are far from the shore. This paper uses data taken during a measurement campaign to develop an ON-OFF model for the VDE-SAT downlink channel taking the multipath effects caused by sea reflections into account. This model has been used to evaluate the impact of packet-level forward error correction (FEC) schemes (i.e., ideal codes, RaptorQ codes, and 2-Dimension Reed-Solomon codes) to further protect transmissions from deep fading events and to evaluate the impact at the transport level considering the possibility to adopt the transmission control protocol (TCP) for a file map delivery service.     

基于E-MBMS的大范围动态交通信息发布方法研究

在研究3G LTE E-MBMS技术的基础上,提出一种利用E-MBMS作为城市动态交通信息大范围发布平台的技术方案,分析了E-MBMS的技术优势,并针对接收端的分组数据丢失问题,研究了重播方法进行数据恢复的性能。仿真实验结果表明,E-MBMS中以喷泉码前向纠错算法为核心的应用层FLUTE协议具有较好的数据纠错能力,运算量小,信道资源利用率高,适用于单向无线信道无误码率的数据下载与传输业务。本文所提方案具备成本低、可行性强的优点,能够满足城市智能交通系统对大范围动态交通信息发布的技术需求。     

Cyclic best-effort multicasting with FEC

Cyclic best-effort multicast supports reliable multicast transport by sending information repeatedly. The authors present forward error correcting (FEC) cyclic best-effort multicast which transmits FEC encoded redundant data as well as original data. FEC cyclic multicasting reduces the number of packet transmissions at least by half compared to plain cyclic multicasting     

移动多媒体广播中的FLUTE协议及其客户端实现

介绍和分析了移动多媒体广播中的一种文件传输协议--FLUTE协议,给出了一种FLUTE协议客户端系统的软件设计和实现方案,并给出了实现结果.     

Packet Size Optimization for Improving the Energy Efficiency in Body Sensor Networks

Energy consumption is a key issue in body sensor networks (BSNs) since energy‐constrained sensors monitor the vital signs of human beings in healthcare applications. In this paper, packet size optimization for BSNs has been analyzed to improve the efficiency of energy consumption. Existing studies on packet size optimization in wireless sensor networks cannot be applied to BSNs because the different operational characteristics of nodes and the channel effects of in‐body and on‐body propagation cannot be captured. In this paper, automatic repeat request (ARQ), forward error correction (FEC) block codes, and FEC convolutional codes have been analyzed regarding their energy efficiency. The hop‐length extension technique has been applied to improve this metric with FEC block codes. The theoretical analysis and the numerical evaluations reveal that exploiting FEC schemes improves the energy efficiency, increases the optimal payload packet size, and extends the hop length for all scenarios for in‐body and on‐body propagation.     

Optimal selection of ARQ parameters in QAM channels

For a quadrature amplitude modulation (QAM) communication channel with forward error correction (FEC) and automatic repeat request (ARQ), the bit error rate (BER) is estimated as a function of the channel signal‐to‐noise ratio (SNR). A method is presented for trading off the number of allowed transmissions and the level of margin (or the line ARQ gain) applied to the channel SNR. The line ARQ gain maximizing the channel throughput is shown to be a sum of the channel SNR and some function of the bit load and FEC parameters. Using this result, we formulate a fast method of determining the optimum ARQ parameters at the actual channel conditions, based on their values at some reference conditions, the latter being either stored in the modem memory or pre‐calculated prior to channel initialization. The derivations are presented both for AWGN and slowly fading channel conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

An algorithm for the selection of effective error correction coding in wireless networks based on a lookup table structure

In this paper, we propose an adaptive Forward Error Correction (FEC) coding algorithm at the Medium Access Control (MAC) layer used in wireless networks. Our algorithm is based on the lookup table architecture, including a distance lookup table and a bit error rate lookup table. These tables will store the best value of the FEC codes based on different distances and bit error rates. Because radio channels change over time, the bit error rate is always changing, or in the case of mobile nodes, when the transmission distance changes, the bit error rate also changes, so previously proposed algorithms take longer to find the optimal value of the FEC code for data transmission. Our proposed algorithm, however, is based on 2 lookup tables, and thus, it can always quickly select an optimal FEC code during early data transmissions and achieve high performance. We compare our algorithm with other methods based on performance metrics such as the recovery overhead of FEC codes, energy efficiency, and peak‐signal‐to‐noise ratio values in the case of image transmission. Our simulation indicates that the proposed algorithm achieves better performances and proves the correctness of the proposed lookup table architecture.     

Exploring the design space of reliable multicast protocols for wireless mesh networks

Many important applications in wireless mesh networks require reliable multicast communication, i.e., with 100% packet delivery ratio (PDR). Previously, numerous multicast protocols based on automatic repeat request (ARQ) have been proposed to improve the packet delivery ratio. However, these ARQ-based protocols can lead to excessive control overhead and drastically reduced throughput. In this paper, we present a comprehensive exploration of the design space for developing high-throughput, reliable multicast protocols that achieve 100% PDR.Motivated by the fact that 802.11 MAC layer broadcast, which is used by most wireless multicast protocols, offers no reliability, we first examine if better hop-by-hop reliability provided by unicasting the packets at the MAC layer can help to achieve end-to-end multicast reliability. We then turn to end-to-end solutions at the transport layer. Previously, forward error correction (FEC) techniques have been proved effective for providing reliable multicast in the Internet, by avoiding the control packet implosion and scalability problems of ARQ-based protocols. In this paper, we examine if FEC techniques can be equally effective to support reliable multicast in wireless mesh networks. We integrate four representative reliable schemes (one ARQ, one FEC, and two hybrid) originally developed for the Internet with a representative multicast protocol ODMRP and evaluate their performance.Our experimental results via extensive simulations offer an in-depth understanding of the various choices in the design space. First, compared to broadcast-based unreliable ODMRP, using unicast for per-hop transmission only offers a very small improvement in reliability under low load, but fails to improve the reliability under high load due to the significantly increased capacity requirement which leads to congestion and packet drop. Second, at the transport layer, the use of pure FEC can significantly improve the reliability, increasing PDR up to 100% in many cases, but can be inefficient in terms of the number of redundant packets transmitted. In contrast, a carefully designed ARQ–FEC hybrid protocol, such as RMDP, can also offer 100% reliability while improving the efficiency by up to 38% compared to a pure FEC scheme. To our best knowledge, this is the first in-depth study of high-throughput, reliable multicast protocols that provide 100% PDR for wireless mesh networks.     

IPool-ADELIN: An extended ADELIN based on IPool node for reliable transport of Underwater Acoustic Sensor Networks

ADELIN (ADaptive rELIable traNsport) protocol is a reliable transport protocol only based on FEC (Forward Error Correction) for UASN (Underwater Acoustic Sensor Networks). In cooperative scenario, ADELIN improves its reliability of data packet transmission further by forwarding node redundancy, which wastes the limited energy and bandwidth of nodes. In this paper, the IPool-ADELIN protocol is proposed and shown to help reduce energy consumption. In IPool-ADELIN, by overhearing the data transmissions, the IPool node not only relays the data packets, which are not implicitly acknowledged, but also does local link maintenance when the BER (Bit Error Rate) of the monitored link is high. The results of mathematical analysis and simulations show that IPool-ADELIN has a higher data delivery ratio and lower energy consumption.     

An investigation of ARQ and hybrid FEC-ARQ on an experimental highlatitude meteor burst channel

A computer investigation of error-control-coding techniques and bit error patterns recorded on an experimental Northern latitude meteor burst link is presented. Automatic repeat request (ARQ) and hybrid forward error correction (FEC) with ARC are examined from the standpoint of probability of message delivery and encountered message delivery delays. It is demonstrated that FEC will yield substantial improvement in the number of messages deliverable within a specified time constraint. Potential gains in extending the usable time duration of a meteor burst channel are on the order of factors of four with successful message delivery percentages increased by factors of 50     

Physical and Medium Access Control criteria for the optimal Medium Access Control protocol data unit size in Automatic Repeat Request‐enabled connections in IEEE 802.16e/ WiMAX systems

In this paper, we address an aspect of the mutual influence between the physical (PHY) layer budding blocks (forward error correction (FEC) blocks) and the medium access control (MAC) level allocations in the uplink and downlink of IEEE 802.16e/WiMAX systems. In these systems, it is possible to transmit MAC level frames, denoted MAC protocol data units (PDUs), such that a PDU contains an integral number of fixed size data blocks. We compute the optimal size of a PDU according to two criteria, one related to the PHY layer and one related to the MAC layer. In relation to the PHY layer, the criterion maximizes the average number of data bits that are transmitted in a PHY slot. In relation to the MAC layer, the criterion maximizes the goodput of the PDU. The goodput depends on the success probability of the PDU, which in turn depends on the FEC blocks over which the PDU is allocated. We then compare the maximal PDU goodputs in different sizes of the FEC blocks and the data blocks. The main outcome is that the PDU goodput is sensitive in those cases in which data blocks are very large. We also give guidelines on how to choose the best modulation/coding scheme to use in a scenario where the signal‐to‐noise ratio can change significantly during transmissions, to maximize the PDU goodput. Finally, we compare between the two criteria. Copyright © 2013 John Wiley & Sons, Ltd.     

Small‐block interleaving for low‐delay cross‐packet forward error correction over burst‐loss channels

By adding the redundant packets into source packet block, cross‐packet forward error correction (FEC) scheme performs error correction across packets and can recover both congestion packet loss and wireless bit errors accordingly. Because cross‐packet FEC typically trades the additional latency to combat burst losses in the wireless channel, this paper presents a FEC enhancement scheme using the small‐block interleaving technique to enhance cross‐packet FEC with the decreased delay and improved good‐put. Specifically, adopting short block size is effective in reducing FEC processing delay, whereas the corresponding effect of lower burst‐error correction capacity can be compensated by deliberately controlling the interleaving degree. The main features include (i) the proposed scheme that operates in the post‐processing manner to be compatible with the existing FEC control schemes and (ii) to maximize the data good‐put in lossy networks; an analytical FEC model is built on the interleaved Gilbert‐Elliott channel to determine the optimal FEC parameters. The simulation results show that the small‐block interleaved FEC scheme significantly improves the video streaming quality in lossy channels for delay‐sensitive video. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance of truncated type-II hybrid ARQ schemes with noisyfeedback over block fading channels

This paper considers truncated type-II hybrid automatic repeat-request (ARQ) schemes with noisy feedback over block fading channels. With these ARQ techniques, the number of retransmissions is limited, and, similar to forward error correction (FEC), error-free delivery of data packets cannot be guaranteed. Bounds on the average number of transmissions, the average coding rate as well as the reliability of the schemes are derived using random coding techniques, and the performance is compared with FEC. The random coding bounds reveal the achievable performance with block codes and maximum-likelihood soft-decision decoding. Union upper bounds and simulation results show that over block fading channels, these bounds can be closely approached with simple terminated convolutional codes and soft-decision Viterbi decoding. Truncated type-II hybrid ARQ and the corresponding FEC schemes have the same probability of packet erasure; however, the truncated ARQ schemes offer a trade-off between the average coding rate and the probability of undetected error. Truncated ARQ schemes have significantly higher average coding rates than FEC at high and medium signal-to-noise ratio even with noisy feedback. Truncated ARQ can be viewed as adaptive FEC that adapts to the instantaneous channel conditions     

A spread slotted CDMA/ALOHA system with hybrid ARQ for satellitemultiple access

We propose and investigate a new type of satellite multiple access protocol that combines the characteristics of the spread slotted (SS)-ALOHA protocol, code division multiple access (CDMA), and the hybrid automatic repeat request (ARQ) error controlling and retransmission scheme, in order to increase the throughput by reducing the number of retransmissions and to keep the bit error rate (BER) of the satellite link low when the channel experiences heavy traffic. The main feature of our proposed system is the utilization of two different fields in the analysis of the satellite multiple access problem. Since the hub now possesses the forward error correction (FEC) capability to correct errors that appear after the CDMA despreading of the packets, the satellite does not need to ask so often for the retransmission of erroneous packets and will ask for retransmission only when the FEC error correcting capability is exceeded. This paper also presents the adaptive optimization of the balance between the CDMA processing gain and FEC coding gain in order to obtain a better throughput for the SS-CDMA/ALOHA with hybrid ARQ protocol for satellite multiple access. The optimization is made with the constraint of keeping the bandwidth of the transmitted packets constant during all times. According to this, the effective throughput of the protocol (information bits over total transmitted bits ratio) is improved by adaptively changing the CDMA and FEC codes used in the transmission. This adaptive optimization is done by observing the channel status or load and increasing or decreasing both coding schemes' gains. Computer simulations show the performance of the proposed multiple access scheme     

FEC Performance Analysis Based on Poisson and Bursty Error Patterns for SDH and OTN Systems

This paper analyses and compares the performance of International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) recommended forward error correction (FEC) for the Synchronous digital hierarchy (SDH) system and the newly ratified Optical transport network (OTN) system. The analysis and comparison are based on simulation results using Poisson and bursty error patterns. While a Poisson error pattern is a commonly studied environment for these systems, a bursty error pattern is not. The simulation results show that the FEC for both SDH and OTN support Poisson errors well. However, for bursty errors, it is found that the FEC for SDH does not work well, while the FEC for OTN is working well for short burst length only.     

Quantitative analysis of restricted reliability protocols for constant rate traffic

Restricted reliability, or limited reliability, transport layer protocols reduce but do not eliminate the packet loss probability seen by higher layers. Forward error correction (FEC) is employed to control the packet loss rate, but automatic repeat request (ARQ) is not used, either because no reverse channel exists or because it does not support the required quality of service. This paper analyzes the effect of FEC on packet loss probability and protocol delay and jitter. We demonstrate the tradeoff between parameters, showing how increased network traffic can be traded against reduced delay and jitter. The theoretical results are confirmed by simulation.     

Design of MAC-defined aggregated ARQ schemes for IEEE 802.11n networks

Based on the IEEE 802.11n standard, frame aggregation is considered one of the major factors to improve system performance of wireless local area networks (WLANs) from the medium access control (MAC) perspective. In order to fulfill the requirements of high throughput performance, feasible design of automatic repeat request (ARQ) mechanisms becomes important for providing reliable data transmission. In this paper, two MAC-defined ARQ schemes are proposed to consider the effect of frame aggregation for the enhancement of network throughput. An aggregated selective repeat ARQ (ASR-ARQ) algorithm is proposed, which incorporates the conventional selective repeat ARQ scheme with the consideration of frame aggregation. On the other hand, the aggregated hybrid ARQ (AH-ARQ) protocol is proposed to further enhance throughput performance by adopting the Reed-Solomon block code as the forward error correction (FEC) scheme. Novel analytical models based on the signal flow graph are established in order to realize the retransmission behaviors of both schemes. Simulations are conducted to validate and compare the proposed ARQ mechanisms with existing schemes based on service time distribution. Numerical results show that the proposed AH-ARQ protocol outperforms the other retransmission schemes owing to its effective utilization of FEC mechanism.     

Rate-distortion optimal video transport over IP allowing packets with bit errors.

We propose new models and methods for rate-distortion (RD) optimal video delivery over IP, when packets with bit errors are also delivered. In particular, we propose RD optimal methods for slicing and unequal error protection (UEP) of packets over IP allowing transmission of packets with bit errors. The proposed framework can be employed in a classical independent-layer transport model for optimal slicing, as well as in a cross-layer transport model for optimal slicing and UEP, where the forward error correction (FEC) coding is performed at the link layer, but the application controls the FEC code rate with the constraint that a given IP packet is subject to constant channel protection. The proposed method uses a novel dynamic programming approach to determine the optimal slicing and UEP configuration for each video frame in a practical manner, that is compliant with the AVC/H.264 standard. We also propose new rate and distortion estimation techniques at the encoder side in order to efficiently evaluate the objective function for a slice configuration. The cross-layer formulation option effectively determines which regions of a frame should be protected better; hence, it can be considered as a spatial UEP scheme. We successfully demonstrate, by means of experimental results, that each component of the proposed system provides significant gains, up to 2.0 dB, compared to competitive methods.     

A study of forward error correction for mobile multicast

3rd Generation Partnership Project (3GPP) has standardized the use of forward error correction (FEC) for the provision of reliable data transmission in the mobile multicast framework. This error control method inevitably adds a constant overhead in the transmitted data. However, it is so simple as to meet a prime objective for mobile multicast services; that is scalability to applications with thousands of receivers. In this paper, we present a study on the impact of application layer FEC on mobile multicast transmissions. We examine whether it is beneficial or not, how the optimal code dimension varies based on network conditions, which parameters affect the optimal code selection, and how this can be done. Additionally, we focus on one of the most critical aspects in mobile multicast transmission, which is power control. The evaluation is performed with the aid of a novel scheme that incorporates the properties of an evolved mobile network, as they are specified by the 3GPP. Copyright © 2010 John Wiley & Sons, Ltd.     

Protocol design for scalable and reliable group rekeying

We present the design and specification of a protocol for scalable and reliable group rekeying together with performance evaluation results. The protocol is based upon the use of key trees for secure groups and periodic batch rekeying. At the beginning of each rekey interval, the key server sends a rekey message to all users consisting of encrypted new keys (encryptions, in short) carried in a sequence of packets. We present a scheme for identifying keys, encryptions, and users, and a key assignment algorithm that ensures that the encryptions needed by a user are in the same packet. Our protocol provides reliable delivery of new keys to all users eventually. It also attempts to deliver new keys to all users with a high probability by the end of the rekey interval. For each rekey message, the protocol runs in two steps: a multicast step followed by a unicast step. Proactive forward error correction (FEC) multicast is used to reduce delivery latency. Our experiments show that a small FEC block size can be used to reduce encoding time at the server without increasing server bandwidth overhead. Early transition to unicast, after at most two multicast rounds, further reduces the worst-case delivery latency as well as user bandwidth requirement. The key server adaptively adjusts the proactivity factor based upon past feedback information; our experiments show that the number of NACKs after a multicast round can be effectively controlled around a target number. Throughout the protocol design, we strive to minimize processing and bandwidth requirements for both the key server and users.