Broadcast Latency Research Articles

R-Code: Network coding-based reliable broadcast in wireless mesh networks

Broadcast is an important communication primitive in wireless mesh networks (WMNs). Applications like network-wide software updates require reliable broadcast to ensure that every node in the network receives the information completely and correctly. With underlying unreliable wireless links, a key challenge in implementing reliable broadcast in WMNs is to achieve 100% information reception rate at every node with high communication efficiency and low latency. Recently, network coding has emerged as a promising coding scheme in terms of communication efficiency especially for one to many communication patterns. In this paper, we put forward R-Code, a network coding-based reliable broadcast protocol. We introduce a guardian–ward relationship between neighboring nodes that effectively distributes the responsibility of reliable information delivery – from the global responsibility of the source to the localized responsibilities of guardians to their corresponding wards. We use a link quality-based minimum spanning tree as a backbone to guide the selection of guardians adaptively and the transmission of coded packets accordingly. Opportunistic overhearing is also utilized to improve the performance of the protocol. Extensive simulation results show that R-Code achieves 100% packet delivery ratio (PDR), while enjoying significantly less transmission overhead and shorter broadcast latency, compared with a state-of-the-art reliable broadcast protocol, AdapCode.

Analysis and Design of a Novel Randomized Broadcast Algorithm for Scalable Wireless Networks in the Interference Channels

In this paper, we study the minimum-latency broadcast scheduling problem in the probabilistic model. We establish an explicit relationship between the tolerated transmission-failure probability and the latency of the corresponding broadcast schedule. Such a tolerated transmission-failure probability is calculated in the strict sense that the failure to receive the message at any single node will lead to the entire broadcast failure and only if all nodes have successfully received the message do we consider it a success. We design a novel broadcast scheduling algorithm such that the broadcast latency is evaluated under such a strict definition of failure. The latency bound we derive is a strong result in the sense that our algorithm achieves a low broadcast latency under this rather strict broadcast-failure definition. Simulation results are also provided to justify our derived theoretical latency bound.

An efficient approximation for minimum latency broadcast in multi-channel multi-hop wireless networks

In this paper, we discuss the minimum latency broadcast problem (MLB) in multi-channel multi-hop wireless networks (MLB-MC). This problem is NP-hard since its special version, MLB in single-channel network (MLB-SC) is proved to be NP-hard . We design an efficient approximation for MLB-MC, analyze its approximation ratio, and evaluate its performance via numerical experiments. Furthermore, we give a general theorem as an upper bound to compare the performance between approximations for MLB-MC and MLB-SC.

Improved algorithm for broadcast scheduling of minimal latency in wireless ad hoc networks

A wide range of applications for wireless ad hoc networks are time-critical and impose stringent requirement on the communication latency. One of the key communication operations is to broadcast a message from a source node. This paper studies the minimum latency broadcast scheduling problem in wireless ad hoc networks under collision-free transmission model. The previously best known algorithm for this NP-hard problem produces a broadcast schedule whose latency is at least 648(rmax/rmin)2 times that of the optimal schedule, where rmax and rmin are the maximum and minimum transmission ranges of nodes in a network, respectively. We significantly improve this result by proposing a new scheduling algorithm whose approximation performance ratio is at most (1 + 2rmax/rmin)2 + 32. Moreover, under the proposed scheduling each node just needs to forward a message at most once.

Minimum Latency Broadcasting in Multiradio, Multichannel, Multirate Wireless Meshes

This paper addresses the problem of "efficientrdquo broadcast in a multiradio, multichannel, multirate wireless mesh network (MR <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MC WMN). In such an MR <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MC WMN, nodes are equipped with multiple radio interfaces, tuned to orthogonal channels, that can dynamically adjust their transmission rate by choosing a modulation scheme appropriate for the channel conditions. We choose "broadcast latency,rdquo defined as the maximum delay between a packet's network-wide broadcast at the source and its eventual reception at all network nodes, as the ldquoefficiencyrdquo metric of broadcast performance. We study in this paper how the availability of multirate transmission capability and multiple radio interfaces tuned to orthogonal channels in MR <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -MC WMN nodes can be exploited, in addition to the medium's ldquowireless broadcast advantagerdquo (WBA), to improve the ldquobroadcast latencyrdquo performance. In this paper, we present four heuristic solutions to our considered problem. We present detailed simulation results for these algorithms for an idealized scheduler, as well as for a practical 802.11-based scheduler. We also study the effect of channel assignment on broadcast performance and show that channel assignment can affect the broadcast performance substantially. More importantly, we show that a channel assignment that performs well for unicast does not necessarily perform well for broadcast/multicast.

An enhanced client-centric approach for efficient video broadcast

Periodic broadcast is a cost-effective solution for large-scale distribution of popular videos. Regardless of the number of video requests, this strategy guarantees a constant worst service latency to all clients, making it possible to serve a large community with a minimal amount of broadcast bandwidth. Although many efficient periodic broadcast techniques have been proposed, most of them impose rigid requirements on client receiving bandwidth. They either demand clients to have the same bandwidth as the video server, or limit them to receive no more than two video streams at any one time. In our previous work, we addressed this problem with a Client-Centric Approach (CCA). This scheme takes into consideration both server broadcast bandwidth and client receiving bandwidth and allows clients to use all their receiving capability for prefetching broadcast data. As a result, given a fixed broadcast bandwidth, a shorter broadcast period can be achieved with an improved client communication capability. In this paper, we present an enhanced version of CCA to further leverage client bandwidth for more efficient video broadcast. The new scheme reduces the broadcast latency up to 50% as compared to CCA. We prove the correctness of this new technique and provide an analytical evaluation to show its performance advantage as compared with some existing techniques.

An Efficient Framework for Scalable Defect Isolation in Large Scale Networks of DNA Self-Assembly

This paper proposes and evaluates an approach for defect isolation of DNA self-assembled networks made of a large number of processing nodes. The complexity of DNA self-assembled networks makes impractical to add a large amount of redundancy and employ inefficient and unscalable defect tolerant schemes. A previous framework based on a broadcast algorithm isolates defective nodes without incorporating redundancy for nodes. However, its disadvantage is the limited scalability, thus making it unsuitable for extremely large scale networks built by DNA self-assembly. The proposed framework improves upon the previous framework by involving three algorithmic tiers; namely, 1-hop wave expansion, efficient via placement, and unsafe node detection. The performance of the proposed framework is evaluated and compared with the original framework by considering large scale networks (up to 2,000 × 2,000 nodes), and a novel gross defect model (as well as a conventional random defect model as assumed in previous works). Simulation results indicate that the proposed framework outperforms the original framework in broadcast latency and efficiency and shows excellent scalability for DNA self-assembled nano-scale networks.

Minimizing Broadcast Latency and Redundancy in Ad Hoc Networks

Network wide broadcasting is a fundamental operation in ad hoc networks. In broadcasting, a source node sends a message to all the other nodes in the network. In this paper, we consider the problem of collision-free broadcasting in ad hoc networks. Our objective is to minimize the latency and the number of transmissions in the broadcast. We show that minimum latency broadcasting is NP-complete for ad hoc networks. We also present a simple distributed collision-free broadcasting algorithm for broadcasting a message. For networks with bounded node transmission ranges, our algorithm simultaneously guarantees that the latency and the number of transmissions are within O(1) times their re spective optimal values. Our algorithm and analysis extend to the case when multiple messages are broadcast from multiple sources. Experimental studies indicate that our algorithms perform much better in practice than the analytical guarantees provided for the worst case.

Advances and Challenges with Data Broadcasting in Wireless Mesh Networks

Wireless mesh networks have become a promising means to provide low-cost broadband access. Many WMN applications require broadcasting data (IPTV etc.) over the WMN. This article studies how efficient data broadcast, measured in terms of broadcast latency, can be realized by exploiting two features of WMNs: the use of multiple transmission rates at the link layer and the use of multiple radio interfaces on each node. We demonstrate that by exploiting these features, broadcast latency can be reduced severalfold compared to the current default practice in wireless LANs of using the lowest transmission rate for broadcast traffic. We also discuss two important insights we have gained from our investigation. First, we find that when multiple radio interfaces are used, a channel assignment algorithm designed for unicast traffic may often perform poorly for broadcast flows. Second, we find that the efficiency of a transmission rate for reducing broadcast latency can be reasonably predicted by the product of the transmission rate and its coverage area.

An Interactive Media Platform Scheme for DTV Receiver Compliant with MHP

The interactive media platform(IMP) scheme proposed here provides an efficient solution for interactive digital TV in back-end. The platform actually integrates traditional TV guide system, interactive application execution system and digital video recorder(DVR) system together. The IMP consists of hardware infrastructures and middleware-based system software. This paper addresses a reference solution for interactive digital TV receiver that compliant with DVB-MHP. The architecture of IMP is proposed. The hardware architecture and middleware-based system software architecture are also presented respectively. In broadcast networks, all data including service information and interactive applications are transmitted from front-end to back-end periodically. Thus, broadcast latency is introduced to the platform while receivers processing broadcast data. Considering that broadcast latency has great influences to the platform performance, optimized strategies to reduce such latency while implementing is described in detail. The proposed platform has been implemented and the experimental result shows a good performance .

Low-Latency Broadcast in Multirate Wireless Mesh Networks

In a multirate wireless network, a node can dynamically adjust its link transmission rate by switching between different modulation schemes. In the current IEEE802.11a/b/g standards, this rate adjustment is defined for unicast traffic only. In this paper, we consider a wireless mesh network (WMN), where a node can dynamically adjust its link-layer multicast rates to its neighbors, and address the problem of realizing low-latency network-wide broadcast in such a mesh. We first show that the multirate broadcast problem is significantly different from the single-rate case. We will then present an algorithm for achieving low-latency broadcast in a multirate mesh which exploits both the wireless multicast advantage and the multirate nature of the network. Simulations based on current IEEE802.11 parameters show that multirate multicast can reduce broadcast latency by 3-5 times compared with using the lowest rate alone. In addition, we show the significance of the product of transmission rate and transmission coverage area in designing multirate WMNs for broadcast

Performance of deterministic and adaptive broadcast algorithms in multicomputer networks

This paper examines the performance of broadcast communication on multicomputer networks. Unlike many existing works, this study considers a number of key factors/prosperities, including scalability, parallelism and routing scheme that could greatly affect the service provided by the network to broadcast messages. Both deterministic and adaptive routing schemes have been included in our analysis. Unlike the previous works, this study considers the issue of broadcast latency at both the network and node levels across different traffic scenarios. Extensive simulation results show that both our suggested adaptive and deterministic algorithms exhibit superior performance characteristics under a wide range of traffic conditions.

High Performance Broadcast Support in La-Mpi Over Quadrics

LA-MPI is a unique MPI implementation that provides end-to-end reliable message passing between application processes. LA-MPI collective operations are implemented on top of its point-to-point operations, using generic spanning tree-based collective algorithms. The performance of the collective operations scales in a logarithmic order over that of the point-to-point operations. Thus, it is desirable to provide more efficient and more scalable collective operations while maintaining the end-to-end reliability. To this end, we investigate the feasibility of utilizing Quadrics hardware broadcast in this paper. We explore several challenging issues such as broadcast buffer management, broadcast over arbitrary processes, retransmission and reliability. Accordingly, a low-latency, highly scalable, fault-tolerant broadcast algorithm is designed and implemented over Quadrics hardware broadcast. Our evaluation shows that this implementation reduces broadcast latency and achieves higher scalability relative to the generic version of this operation. In addition, we observe that the performance of our implementation is comparable to that of the high performance implementation by Quadrics Supercomputers World for MPICH, and HPs for Alaska MPI, while providing fault tolerance to network errors not provided by these.

Performance modelling of broadcast communication in multicomputer networks

Over the past few years, many algorithms have been proposed to support collective communication operations for large-scale multicomputers. When proposing any new such algorithm operation, it is critical to determine its precise scope and evaluate it with accurate modelling of the underlying routing and communication mechanisms. However, there has been comparatively little activity in the area of analytical modelling of these operations. As a result, most existing studies have relied on simulation to evaluate the performance merits of collective communication algorithms. This paper presents a new analytical model for predicting broadcast latency in the wormhole-routed torus, which is one of the most common networks used in multicomputers. The broadcast algorithm considered in this study is based on the Bose's broadcast algorithm [Bose, B., Broeg, B., Younggeun, K. and Ashir, Y., 1995, Lee distance and topological properties of k-ary n-cubes, IEEE Transaction on Computers, 44(8), 1021–1030]. Results obtained through simulation experiments show that the model exhibits a good degree of accuracy in predicting message latency under different working conditions.

An analytical model of wormhole-routed hypercubes under broadcast traffic

A large number of algorithms have been proposed to support collective communication operations for scalable parallel systems over the past few years. When proposing a new algorithm for a collective communication operation, it is critical to determine its precise scope and evaluate it with accurate modelling of the underlying routing and communication mechanism. However, there has been comparatively little activity in the area of analytical models of these operations. As a result, most existing studies have relied on simulation to evaluate the performance merits of collective communication algorithms. This paper presents a new analytical model for predicting unicast and broadcast latency in the wormhole-routed hypercube. Results obtained through simulation experiments show that the model exhibits a good degree of accuracy in predicting message latency under different working conditions.

Modified staircase data broadcasting scheme for popular videos

In a broadcasting scheme, the user's latency is a very important parameter. The harmonic broadcasting scheme has been found to have the best performance for user's latency and staircase broadcasting scheme has been found to have the best performance for local storage as well as for disk transfer rates. In this paper a modified staircase scheme has been proposed which shows that if the video data is downloaded with lesser speed which would save the local storage and hence the disk transfer rate, the users still can be provided with the video in a continuous manner without any jerk or jitter. Further, if the downloading rate of the video is reduced after 3.25 channels, the users' services for viewing the videos does not get affected. In particular, for employing bandwidth of about 40 mbps, the modified staircase data scheme shows the performance for user latency about 29% better and the local storage is same but disk I/O transfer rates are slightly higher (4%) in comparison to staircase scheme. In comparison to harmonic scheme, user's latency is 24% higher but buffer storage and disk I/O transfer rates are about 35% and 30%, respectively, better for the same bandwidth. However the values of the performance parameters converge to those of harmonic scheme as the bandwidth is increased.

Analytical modelling of broadcast in adaptive wormhole-routed hypercubes

Many analytical models of wormhole-routed networks have been proposed over the past few years. Most of these models, however, have been developed for unicast (or point-to-point) communication. There has been comparatively little activity in the area of analytical models of collective communication, such as broadcast. As a result, most existing studies have relied on simulation to evaluate the performance merits of collective communication algorithms. This paper presents a new analytical model for predicting broadcast latency in the hypercube. The broadcast algorithm considered in this study is based on the unicast-based approach and described [IEEE Trans. Parallel Distrib. Syst. 5 (1994) 1252]. Results obtained through simulation experiments show that the model exhibits a good degree of accuracy in predicting message latency under different working conditions.