Parity-based loss recovery for reliable multicast transmission

We investigate how forward error correction (FEC) can be combined with automatic repeat request (ARQ) to achieve scalable reliable multicast transmission. We consider the two scenarios where FEC is introduced as a transparent layer underneath a reliable multicast layer that uses ARQ, and where FEC and ARQ are both integrated into a single layer that uses the retransmission of parity data to recover from the loss of original data packets. To evaluate the performance improvements due to FEC, we consider different loss rates and different types of loss behavior (spatially or temporally correlated loss, homogeneous or heterogeneous loss) for up to 10⁶ receivers. Our results show that introducing FEC as a transparent layer below ARQ can improve multicast transmission efficiency and scalability. However, there are substantial additional improvements when FEC and ARQ are integrated     

基于机会式网络编码的低时延广播传输算法

为了提高无线网络中数据包广播传输的效率,本文提出了一种基于机会式网络编码的广播传输算法.该算法在发送端按一定顺序选择不同终端的丢包,并采用异或运算编码重传包,在终端采用从重传包中解码数据包的方法恢复丢包.该算法优先恢复时间重要性较高的丢包,并使多个终端同时从单个重传包恢复其丢包,因此有效地提高了广播传输效率并降低了传输...     

An efficient network coded ARQ for multisource multidestination relay networks over mixed flat fading channels

This paper proposes a new reliable automatic repeat request (ARQ) transmission protocol for wireless multisource multidestination relay networks over mixed fading channels. Conventional application of ARQ protocols to retransmit lost or erroneous packets in relay networks can cause considerable delay latency with a significant increase in the number of retransmissions when networks consist of multiple sources and multiple destinations. To address this issue, a new ARQ protocol based on network coding (NC) is proposed where the relay detects packets from different transmission sources, then uses NC to combine and forward lost packets to their destinations. An efficient means for the retransmission of all lost packets is proposed through two packet-combination algorithms for retransmissions at the relay and sources. The paper derives mathematical formulation of transmission bandwidth for this new NC-based ARQ protocol and compares analytical and simulation results with some other ARQ protocols over both mixed Rayleigh and Rician flat fading channel. The mixed fading model permits investigation of two typical fading scenarios where the relay is located in the neighbourhood of either the sources or the destinations. The transmission bandwidth results show that the proposed NC-based ARQ protocol demonstrates superior performance over other existing ARQ schemes.     

A Weighted Scheduling Mechanism to Reduce Multicast Packet Loss in IPTV Service over EPON

This letter proposes a weighted scheduling mechanism for Internet protocol television (IPTV) to improve the loss performance of multicast transmission over an Ethernet passive optical network (EPON). We propose a new weight policy from the number of multicast receivers to proportionally allocate the downstream bandwidth of IPTV traffic. The proposed mechanism is used in an optical line terminal to decrease lost packets of favorite IPTV services because the lost multicast packets are proportional to the number of receivers. The total proportion of lost multicast packets is reduced by up to 73% in an EPON.     

Reliable Multicast in Multi-Access Wireless LANs

Multicast is an efficient paradigm for transmitting data from a sender to a group of receivers. In this paper, we focus on multicast in single channel multi-access wireless local area networks (LANs) comprising several small cells. In such a system, a receiver cannot correctly receive a packet if two or more packets are sent to it at the same time, because the packets collide. Therefore, one has to ensure that only one node sends at a time. We look at two important issues. First, we consider the problem of the sender acquiring the multi-access channel for multicast transmission. Second, for reliable multicast in each cell of the wireless LAN, we examine ARQ-based approaches. The second issue is important because the wireless link error rates can be very high.We present a new approach to overcome the problem of feedback collision in single channel multi-access wireless LANs, both for the purpose of acquiring the channel and for reliability. Our approach involves the election of one of the multicast group members (receivers) as a leader or representative for the purpose of sending feedback to the sender. For reliable multicast, on erroneous reception of a packet, the leader does not send an acknowledgment, prompting a retransmission. On erroneous reception of the packet at receivers other than the leader, our protocol allows negative acknowledgments from these receivers to collide with the acknowledgment from the leader, thus destroying the acknowledgment and prompting the sender to retransmit the packet.Using analytical models, we demonstrate that the leader-based protocol exhibits higher throughput in comparison to two other protocols which use traditional delayed feedback-based probabilistic methods. Last, we present a simple scheme for leader election.     

中继协作无线网络中不完美反馈下基于网络编码的重传方案

无线广播网络传输过程中,目的节点反馈信息丢失或部分丢失导致发送节点不能了解目的节点的真实接收状态.为提高不完美反馈下无线网络的重传效率,本文提出中继协作无线网络中不完美反馈下基于网络编码的重传方案.本方案基于部分可观察马尔科夫决策过程对不完美反馈下的重传过程进行建模.发送节点根据系统观测状态和最大置信度更新系统估计状态,根据数据包发送顺序,优先选择最早丢失且能够恢复最多丢包的编码包重传.目的节点缓存不可解编码包以提升编解码机会.重传过程中源节点关注目的节点请求包需求,相同情况优先选择传输可靠性较高的中继节点,以提升传输有效性.仿真结果表明,在不完美反馈下相对于传统方案,本方案可有效提高重传效率.     

反馈信道下基于LT码的空间网络广播传输策略设计

由于其特有的广域宽覆盖等特点,数据广播业务一直是空间网络的主要业务。然而空地间信道由于受到远距离、天气变化及遮挡等因素影响,数据传输时延长且丢包率较高。为进一步提高数据广播的性能,该文将反馈信息与LT码相结合,提出一种新的空间网络数据广播传输策略。与传统的数据广播策略相比较,新的传输策略利用反馈信息估计信道丢包率,并在此基础上引入信道状态矩阵和数据包选择权重向量,设计了数字喷泉新的编码方法,进而使得数据在重传阶段能够根据信道状态和重传概率实时调整。仿真结果表明,新的数据广播策略能够实现传输较少数据包的基础上实现原始数据的可靠接收。     

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.     

Scalable reliable multicast using multiple multicast channels

We examine an approach for providing reliable, scalable multicast communication, involving the use of multiple multicast channels for reducing receiver processing costs and reducing network bandwidth consumption in a multicast session. In this approach a single multicast channel is used for the original transmission of packets. Retransmissions of packets are done on separate multicast channels, which receivers dynamically join and leave. We first show that protocols using an infinite number of multicast channels incur much less processing overhead at the receivers compared to protocols that use only a single multicast channel. This is due to the fact that receivers do not receive retransmissions of packets they have already received correctly. Next, we derive the number of unwanted redundant packets at a receiver due to using only a finite number of multicast channels, for a specific negative acknowledgment (NAK)-based protocol. We then explore the minimum number of multicast channels required to keep the cost of processing unwanted packets to a sufficiently low value. For an application consisting of a single sender transmitting reliably to many receivers we find that only a small number of multicast channels are required for a wide range of system parameters. In the case of an application where all participants simultaneously act as both senders and receivers a moderate number of multicast channels is needed. Finally, we present two mechanisms for implementing multiple multicast channels, one using multiple IP multicast groups and the other using additional router support for selective packet forwarding. We discuss the impact of both mechanisms on performance in terms of end-host and network resources     

最小化重传次数的无线网络编码广播重传算法

提出了一种最小化重传次数的无线网络编码广播重传算法。针对无线广播网络,本文首先引入了缓存网络编码（C-IDNC）的概念,在接收端,正确接收但不能解码的网络编码数据包将被缓存起来等待将来的解码机会而不是简单的丢弃该编码包。其次,通过对基于IDNC重传策略的问题描述,分析了不同因素对重传次数的影响,并把这些影响因子量化为可度量的数值。随后,构造了IDNC图 ,用于表征所有可行编码和编码增益,并把最小化重传次数问题转化为最大权重搜寻问题,给出了寻找最优解的编码方法。同时,为降低算法复杂度和计算量,提出一种启发式的最大权重搜寻算法（CI-MWSA）。仿真结果表明,与传统方案相比,提出的策略和算法能有效提高重传效率、减少重传次数。      

A reliable overlay video transport protocol for multicast agents in wireless mesh networks

A new video transport protocol for multicast agents in wireless mesh networks (WMNs) is proposed in this paper. The proposed protocol enables a significant reduction in the transmission overhead, while providing reliable communication for its use in multicast applications. This proposed reliable protocol provides a practical approach for an overlay peer‐to‐peer multicast facility supported within the application layer. This obviates the need to give upgraded routers capable of handling multicast broadcasting or modify the existing protocol stack. The protocol tolerates partial losses in multimedia transmissions, while supporting control of the delay sensitivity of such transmissions in WMNs. The key issue in this protocol is the ability to detect packet loss, anticipate retransmission requests, and use the anticipated retransmission requests to transmit the lost packets prior to requests from other receiving agents. The proposed protocol allows for the receiver to determine if retransmission of lost packets is required, ensuring the greatest flexibility needed for a reliable multicast protocol. Copyright © 2009 John Wiley & Sons, Ltd.     

PEEC: a channel-adaptive feedback-based error

Reliable transmission is a challenging task over wireless LANs since wireless links are known to be susceptible to errors. Although the current IEEE802.11 standard ARQ error control protocol performs relatively well over channels with very low bit error rates (BERs), this performance deteriorates rapidly as the BER increases. This paper investigates the problem of reliable transmission in a contention free wireless LAN and introduces a packet embedded error control (PEEC) protocol, which employs packet-embedded parity symbols instead of ARQ-based retransmission for error recovery. Specifically, depending on receiver feedback, PEEC adaptively estimates channel conditions and administers the transmission of (data and parity) symbols within a packet. This enables successful recovery of both new data and old unrecovered data from prior transmissions. In addition to theoretically analyzing PEEC, the performance of the proposed scheme is extensively analyzed over real channel traces collected on 802.11b WLANs. We compare PEEC performance with the performance of the IEEE802.il standard ARQ protocol as well as contemporary protocols such as enhanced ARQ and the hybrid ARQ/FEC. Our analysis and experimental simulations show that PEEC outperforms all three competing protocols over a wide range of actual 802.11b WLAN collected traces. Finally, the design and implementation of PEEC using an adaptive low-density-parity-check (A-LDPC) decoder is presented.     

Error control using retransmission schemes in multicast transportprotocols for real-time media

We analyze different retransmission (ARQ) schemes for error control in multicast protocols geared toward real-time, multimedia applications. We discuss why retransmission schemes are not inappropriate for such applications, but in fact can be quite effective. We present a quantitative analysis of such schemes, as well as simulation results, taking into account four different parameters (and not just the source throughput): (1) the probability of dropping a packet due to limited time for retransmissions; (2) the average time required to deliver a packet correctly to end receivers; (3) the number of times a packet will be retransmitted; and (4) the cost to the network, in terms of packet duplications, of retransmitting a packet. We reach the counter-intuitive conclusion that the optimum scheme, in terms of all four of the above parameters, in the most general scenarios (where several hosts with widely varying propagation delays and `quality of connections' are participating in the session) is to immediately retransmit packets-preferably multicast-upon reception of a NACK from any receiver. We also demonstrate, again through quantitative analysis, the circumstances under which it would be beneficial (as well as those under which it would be counter-productive) to multicast control messages in the hope of suppressing duplicates and preventing the source from being overwhelmed by control messages     

RT Oblivious Erasure Correcting

An erasure correcting scheme is rateless if it is designed to tolerate any pattern of packet loss and reveal the transmitted information after a certain number of packets is received. On the one hand, transmission schemes that use rateless erasure correcting schemes do not usually use a feedback channel. However, they may require significant amount of additional processing by both the sender and the receiver. On the other hand, automatic repeated request protocols use a feedback channel to assist the sender, and do not usually require information processing. In this work we present a combined approach, where a lean feedback channel is used to assist the sender to efficiently transmit the information. Our Real-Time oblivious approach minimizes the processing time and the memory requirements of the receiver and, therefore, fits a variety of receiving devices. In addition, the transmission is real-time where the expected number of original packets revealed when a packet is received is approximately the same throughout the entire transmission process. We use our end-to-end scheme as a base for broadcast (and multicast) schemes. An overlay tree structure is used to convey the information to a large number of receivers. Moreover, the receivers may download the information from a number of senders or even migrate from one sender to another.     

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     

一种基于机会式网络编码的高效广播重传方法

为了提高无线广播网络中数据传输的效率,该文提出了一种新颖的基于机会式网络编码的重传方法。将机会式网络编码技术应用于丢包的重传,并采用高效的丢包组合策略生成重传包。根据网络终端的丢包情况,首先创建丢包的哈希表,再根据哈希表快速选择满足一定编码条件的丢包以生成重传数据包,从而在提高重传性能的同时,有效地降低了重传方法的复杂度。仿真结果表明该方法相比已有算法能有效地减少重传次数,并提高重传包发送和接收的效率。     

On stochastic learning in predictive wireless ARQ

Traditional automatic repeat request (ARQ) protocols are channel unaware. That is, they react to channel errors by simply retransmitting erroneous packets and do not proactively decide whether or not to transmit a packet in a given slot based on past channel conditions. Clearly, ARQ protocols operating in this mode are not energy efficient. For example, continuously retransmitting erroneous packets when the wireless channel is in deep fade would cause significant wastage of transmission energy. In this paper, we present a stochastic learning automaton‐based wireless channel state aware ARQ protocol. The learning automaton learns to predict and track the time‐varying wireless channel conditions based on past observations. A Markov chain model for the channel state transitions is used. No a priori knowledge about the state transition probabilities is required by this predictor. Stochastic convergence of the learning algorithm is proved. The proposed ARQ protocol utilizes the predictions to compute transmission/retransmission policies in an online fashion. No pilot (training) symbols are used by the protocol for channel state prediction thereby avoiding any energy wastage due to the transmission of these symbols. Simulation results show that depending on the channel memory significant energy savings can be attained when compared with standard ARQ protocols. We also discuss the transmission energy versus delay trade‐off. Copyright © 2007 John Wiley & Sons, Ltd.     

A digital fountain approach to asynchronous reliable multicast

The proliferation of applications that must reliably distribute large, rich content to a vast number of autonomous receivers motivates the design of new multicast and broadcast protocols. We describe an ideal, fully scalable protocol for these applications that we call a digital fountain. A digital fountain allows any number of heterogeneous receivers to acquire content with optimal efficiency at times of their choosing. Moreover, no feedback channels are needed to ensure reliable delivery, even in the face of high loss rates. We develop a protocol that closely approximates a digital fountain using two new classes of erasure codes that for large block sizes are orders of magnitude faster than standard erasure codes. We provide performance measurements that demonstrate the feasibility of our approach and discuss the design, implementation, and performance of an experimental system.     

Throughput analysis of some ARQ protocols in the presence offeedback errors

Automatic-repeat-request (ARQ) protocols have been analyzed for quite some time, but the issue of errors in the feedback channel has not received much attention. In some applications, such as digital mobile communications, this issue can be important. Accordingly, this paper examines the effect of feedback errors on the throughputs of the stop-and-wait (SW), go-back-N (GBN), and selective repeat (SR) ARQ protocols for the ease of a point-to-point channel under some feedback information assumptions. It is shown that the deleterious effects of feedback errors on the throughputs of continuous (e.g., GBN and SR) ARQ protocols can be greatly reduced by a simple modification in the retransmission operation, provided that the “complete state” of the receiver is sent back with each acknowledgment