Total Bandwidth Requirement Research Articles

Optimizing Virtual Network Embedding for Avionics with Time-Triggered Traffic Scheduling

Network virtualization technology abstracts the nodes and links resources in the physical network, and enables multiple virtual networks (VNs) to share the substrate network (SN) resources through the Virtual Netw ork Embedding (VNE) method. For time-triggered Ethernet (TTE) used in avionics, a time-triggered traffic scheduling oriented virtual network embedding (TT-VNE) method is proposed. While meeting the total resource constraints of traditional VNE problem, it ensures the strict periodicity of time-triggered (TT) traffic. During the solution process, the method sorts the virtual nodes according to the TT traffic bandwidth requirements and the total bandwidth requirements of the links connected to the virtual nodes, embeds the virtual nodes using the breadth first search algorithm, and plans the virtual links in candidate shortest path aggregation. If the TT traffic in the current virtual link is not schedulable, the iterative design of local virtual node re embedding and path planning is carried out. The simulation shows that the request acceptance rate of TT-VNE is not lower than that of existing methods, and when the number of virtual network requests in the star topology exceeds 30 , its request acceptance rate is about 14.3%higher than the VNE-NTANRC-D method which only considers the network topology and resource attributes.

The strategy of path determination and traffic scheduling in private campus networks based on SDN

Important businesses in private campus networks need sufficient bandwidth to guarantee their quality of service. Setting port queues ignores the possibility of total bandwidth requirement exceeding the link capacity while OpenFlow-based path-planning with bandwidth guarantee (OPPBG) algorithm cannot guarantee bandwidth for multiple businesses with different requirements. We propose an improved path determination and traffic scheduling strategy based on Software Defined Networking (SDN). This method firstly obtains an ideal path for each flow by optimizing the path selection algorithm, and then sets port queues on switches along the path. The experiment compares the proposed algorithm with queue-setting method and OPPBG algorithm using four scenarios respectively. The results show that our strategy can meet the bandwidth requirements of each business, prevent them from interrupting others and improve the network’s performance and robustness.

Iterative Quantum-Assisted Multi-User Detection for Multi-Carrier Interleave Division Multiple Access Systems

With the proliferation of smart-phones and tablet PCs, the data rates of wireless communications have been soaring. Hence, the need for power-efficient communications relying on low-complexity multiple-stream detectors has become more pressing than ever. As a remedy, in this paper we design low-complexity soft-input soft-output quantum-assisted multi-user detectors (QMUD), which may be conveniently incorporated into state-of-the-art iterative receivers. Our design relies on extrinsic information transfer charts. Our QMUDs are then employed in multi-carrier interleave-division multiple-access (MC-IDMA) systems, which are investigated in the context of different channel code rate and spreading factor pairs, whilst fixing the total bandwidth requirement. One of our QMUDs is found to operate within 0.5 dB of the classical maximum a posteriori probability MUD after three iterations between the MUD and the decoders, while requiring only half its complexity, at a BER of $10^{-5}$ in the uplink of a rank-deficient MC-IDMA system relying on realistic imperfect channel estimation at the receiver, while supporting 14 users transmitting QPSK symbols.

Analytical memory bandwidth model for many-core processor based systems

Many-core processor based systems gain popularity in high-performance parallel embedded applications. Estimating memory bandwidth requirement, i.e. external memory bandwidth, given various cache size for target parallel applications requires a prohibitively large simulation time. In this work, we propose an analytical model to quickly estimate the memory bandwidth for a given cache size and help exploring trade-offs between cache sizes and memory bandwidth requirement. We model the stochastic behavior of cache misses for a single cache as a random process. Using central limit theorems for identically or non-identically distributed random processes, we accurately estimate the collective cache misses from hundreds of processor cores and thus the total memory bandwidth requirement for the whole system. The results show that our model improves a speed of simulation time up to 200.4 times for 200 cores whereas its estimated results achieve less than 0.01% difference from the simulated ones for 200 cores in terms of accuracy.

Managing Power Saving Classes in IEEE 802.16 Wireless MANs: A Fold-and-Demultiplex Method

In IEEE 802.16, power management at the Mobile Subscriber Station (MSS) side is always an important issue. The standard defines three types of power saving classes (PSCs). A PSC can bind one or multiple traffic flows. However, given multiple flows in an MSS, the standard does not define how to form PSCs, how to organize the cooperation of multiple PSCs to obtain better energy efficiency, and how to guarantee QoS of these flows. Given a set of flows and their QoS parameters, the objective of this paper is to define multiple PSCs and their listen-and-sleep-related parameters and packet-scheduling policy such that the unavailability intervals of the MSS can be maximized and the QoS of each flow can be guaranteed. To achieve this, we propose a novel fold-and-demultiplex method for an IEEE 802.16 network with PSCs of types I and II together with an earliest-next-bandwidth-first packet scheduler. Given a set of traffic flows in an MSS, the fold-and-demultiplex method first gives each flow a tentative PSC satisfying its bandwidth requirement. Then we fold them together into one long series so as to calculate the total bandwidth requirement. Finally, we demultiplex the series into multiple PSCs, each supporting one or multiple flows. It ends up with high energy efficiency of MSSs while meets flows' bandwidth requirements. Furthermore, our packet scheduler ensures that real-time flows' delay constraints can be met. To the best of our knowledge, this is the first result offering bounded packet delays under MSS's sleep-and-listen behaviors.

Efficient cache placement scheme for clustered time-shifted TV servers

A cost-effective approach for enhancing availability of clustered system is to cache popular data across the memories of servers so as to alleviate disk I/O bandwidth bottleneck. The cache placement problem is complicated for the fact that video popularity changes over time. Moreover, as a new multimedia streaming service, time-shifted TV introduces new challenges to the problem. In this article, we investigate the crucial problem of the clustered time-shifted TV system. We formulate it as a multi-objective optimization problem based on the time-based popularity model. We propose a classification replication algorithm and a novel cache placement algorithm, named as cost-aware least load proportion first (CALLF). The algorithms focus on the time-varying nature of time-shifted TV, and explore previous stored information to reduce the cost of redeploying. We also present a dual-threshold reconfigure scheme to further balance the load of servers dynamically. Simulation reveals that the proposed algorithms are efficient on improving the performance of time-shifted TV system in terms of total outgoing bandwidth requirement.

Piecewise Patching for Time-shifted TV Over HFC Networks

In video-on-demand (VOD) systems, a number of sophisticated architectures have been proposed to provide instantaneous services through the use of multicast technology. Most of the architectures focus on minimizing bandwidth requirements under the assumption that clients play from beginning to end, but this assumption is not suitable for time-shifted TV. Moreover, they have been proposed on an IP network, and failed to make full use of the broadcasting property of hybrid fiber coaxial (HFC) network. In this paper, we propose a novel delivery scheme, named as piecewise patching (PP), to tackle these problems. The piecewise patching scheme provides the video data for the users in a piecewise mode instead of a whole patching stream which includes all missing data. The former user can utilize the data from the later users' patching stream whose playback time is in advance of the former user's patching stream. In the proposed scheme, each client receives the data simultaneously from arbitrary channels which broadcast the same content. Simulation results show that the proposed scheme improves the performance of time-shift TV service significantly in terms of total server bandwidth requirement.

Admission control with advance reservations in simple networks

In the admission control problem we are given a network and a set of connection requests, each of which is associated with a path, a time interval, a bandwidth requirement, and a weight. A feasible schedule is a set of connection requests such that at any given time, the total bandwidth requirement on every link in the network is at most 1. Our goal is to find a feasible schedule with maximum total weight. We consider the admission control problem in two simple topologies: the line and the tree. We present a 12 c-approximation algorithm for the line topology, where c is the maximum number of requests on a link at some time instance. This result implies a 12 c-approximation algorithm for the rectangle packing problem, where c is the maximum number of rectangles that cover simultaneously a point in the plane. We also present an O ( log t ) -approximation algorithm for the tree topology, where t is the size of the tree. We consider the loss minimization version of the admission control problem in which the goal is to minimize the weight of unscheduled requests. We present a c-approximation algorithm for loss minimization problem in the tree topology. This result is based on an approximation algorithm for a generalization of set cover, in which each element has a covering requirement, and each set has a covering potential. The approximation ratio of this algorithm is Δ, where Δ is the maximum number of sets that contain the same element.

Downlink Throughput Maximization in CDMA Wireless Networks

We investigate optimum rate assignment scheme maximizing network throughput on the downlink of a multirate CDMA wireless network. Systems employing orthogonal variable spreading factor (OVSF) codes as well as systems employing multiple codes have been studied. Our objective is to maximize the network throughput under constraints on total transmit power, total bandwidth and individual QoS requirements specified in terms of minimum rates. First, users are ordered based on their transmit energy per bit requirements to achieve the target received energy per bit to interference power spectral density ratio at the receivers. Based on the initial ordering, we prove that for systems employing multiple codes, greedy rate assignment yields maximum network throughput. For systems employing variable spreading codes, we show that greedy rate assignment is optimal if the minimum rate requirement of a user is larger than or equal to the minimum rate requirement of any other user with a larger transmit energy per bit requirement. Simulation results verify the superiority of the greedy algorithm under various system and channel assumptions

Multi-path routing versus tree routing for VPN bandwidth provisioning in the hose model

In this paper we study the bandwidth provisioning of VPN service in the hose model with multi-path routing and tree routing. We have investigated the bandwidth efficiency and blocking performance of these two routing schemes. Our study shows that without any restriction on the maximum fraction of traffic on a path (MFTP), multi-path routing often turns out to be single path routing, and only reduces the total bandwidth requirement slightly at rare combination of network topologies and hose parameters. In order to alleviate the overprovisioning problem of the hose model, we propose the concept of sub-provisioning and study the blocking performance using static reduced provisioning. The results show that with full provisioning, the two routing schemes have almost the same blocking performance. However, with sub-provisioning and the variation of the MFTP constraint, multi-path routing is capable of delivering a significant improvement in blocking performance, often better than tree routing by a few orders of magnitude. The improvement is attributed to the multiple alternative paths brought in by the MFTP constraint. With sub-provisioning, the link bandwidth availability becomes the restricting factor in admitting a connection. Having multiple paths, a connection request is able to explore available bandwidth more thoroughly in the network, thus increasing its chances of being admitted. We employ both analytical model and discrete event simulation for the blocking performance study. The analytical model is developed based on the multi-rate reduced load approximation technique and the simulation is carried out using the OPNET simulator. The close agreement between analytical and simulation results indicate the validity of the approach.

Adaptive segment-based patching scheme for video streaming delivery system

In on-demand video streaming system, periodic broadcast technique scheme has been shown to be very effective for serving a popular video in reducing the demand on server bandwidth. On the contrary, reactive server transmission approach is more suitable for the video that is not popular enough. However, the level of demand on a video may change by time. In this paper, we propose a segment-based patching scheme which allocates adaptively transmission resources according to the varying client request rate. Our technique smoothly adjusts itself to cope with the changing workloads. The scheme tries to dynamically search the optimal number of channels assigned to the video by the newly updated request rate so as to minimize the bandwidth requirement. We also show how to seamlessly perform the transition of changing the number of channels with the guarantee that the clients viewing this video will not experience any disruption. Simulation results indicate that the scheme adapts very well to the changing client request rate and improves the system performance significantly in terms of the total server bandwidth requirement.

ATF: an Adaptive Three-layer Framework for inter-stream synchronization of SMIL multimedia presentations

In this paper, we propose an Adaptive Three-layer Framework (ATF) to guarantee the inter-stream synchronization, which is called as the APplication Quality of Service (APQoS) in this paper, of World Wide Web Consortium (W3C) Synchronized Multimedia Integration Language (SMIL) presentation. This ATF framework, which is composed of the Framework Control Layer (FCL), the Quality Guarantee Layer (QGL) and the Media Control Layer (MCL), functions as the middleware between underlying best-effort network protocol stacks and the SMIL client/server applications. The FCL at the SMIL client periodically monitors underlying network bandwidth and delay for the QGL to verify whether the total bandwidth requirements of all concurrent objects to meet the APQoS of the SMIL presentation can be satisfied with the available bandwidth, which is the sum of the monitored bandwidths of all concurrent objects. The QGL executes the novel Intra-SMIL Bandwidth Reallocation (ISBR) scheme to dynamically adjust bandwidth allocations among concurrent SMIL objects, according to their Media Importance (MI) values calculated by the MCL. If the available bandwidth is not enough, the ISBR scheme gracefully degrades the layer-encoded objects that have the smallest MI values and only allocate the necessary bandwidth for their base layer (BL) streams instead. Oppositely, it aggressively upgrades the degraded layer-encoded objects that have the largest MI values and allocate the necessary bandwidth for both the BL and enhancement layer (EL) streams. These bandwidths are then feedback to the remote media servers to modify the transmission rates accordingly. With the quantitative analysis for the SMIL presentation quality, this ATF framework achieves the APQoS with the best SMIL playback quality.

Providing VCR Functionality in Multicast Video-on-Demand Systems Using Adaptive Batching

The adaptive batching technique is shown to have better performance than the static scheme in terms of total bandwidth requirement and customer reneging probability in multicast video-on-demand (VoD) systems. In this paper, we first analyze the performance of providing VCR functions in the multicast VoD system using adaptive batching. The result shows that the system may not take any advantage from the adaptive approach if VCR operations are incorporated. In view of this, we then explore the buffer reservation and VCR resume delay to further improve the adaptive system. The trade-off among the buffer size, resume delay, and stream requirement is extensively investigated. It is found that a 30-s resume delay or 20% buffer reservation can significantly reduce the batching stream requirement in the adaptive multicast VoD system.

Delimiting the range of effectiveness of scalable on-demand streaming

Previous analyses of scalable streaming protocols for delivery of stored multimedia have largely focused on how the server bandwidth required for full-file delivery scales as the client request rate increases or as the start-up delay is decreased. This previous work leaves unanswered three questions that can substantively impact the desirability of using these protocols in some application domains, namely: (1) Are simpler scalable download protocols preferable to scalable streaming protocols in contexts where substantial start-up delays can be tolerated? (2) If client requests are for (perhaps arbitrary) intervals of the media file rather than the full-file, are there conditions under which streaming is not scalable (i.e., no streaming protocol can achieve sub-linear scaling of required server bandwidth with request rate)? (3) For systems delivering a large collection of objects with a heavy-tailed distribution of file popularity, can scalable streaming substantially reduce the total server bandwidth requirement, or will this requirement be largely dominated by the required bandwidth for relatively cold objects? This paper addresses these questions primarily through the development of tight lower bounds on required server bandwidth, under the assumption of Poisson, independent client requests. Implications for other arrival processes are also discussed. Previous work and results presented in this paper suggest that these bounds can be approached by implementable policies. With respect to the first question, the results show that scalable streaming protocols require significantly lower server bandwidth in comparison to download protocols for start-up delays up to a large fraction of the media playback duration. For the second question, we find that in the worst-case interval access model, the minimum required server bandwidth, assuming immediate service to each client, scales as the square root of the request rate. Finally, for the third question, we show that scalable streaming can provide a factor of log K improvement in the total minimum required server bandwidth for immediate service, as the number of objects K is scaled, for systems with fixed minimum object request popularity.

Adaptive batching scheme for multicast video-on-demand systems

In this paper, an adaptive algorithm is developed for providing true video on demand (VoD) services in a multicast environment. In conventional batching schemes, the batching time of the system is fixed and the performance of such static schemes is highly dependent on the selection of the batching time. If the batching time is wrongly estimated, the performance of the system will be greatly degraded. Our algorithm tries to dynamically find the optimal batching time by the newly updated arrival rate so as to minimize the bandwidth requirement. The results show that the system performance of the adaptive approach is always better than the static scheme in terms of total bandwidth requirement and customer reneging probability, especially in using long batching time for the high arrival rate.

Awareness-based communication management in the MASSIVE systems

The MASSIVE-1 and MASSIVE-2 distributed virtual environment systems are based on an explicit model of user communication requirements known as the spatial model of interaction; this model addresses the general issue of managing communication in large space-based systems such as DVEs. The goals of the spatial model are to guide the distribution and presentation of information in a way which facilitates collaboration between participants (based on observed patterns of interaction in real-world environments) and which is also efficient and appropriate. The MASSIVE-1 system emphasized the spatial model's `aura' concept as the basis for a distinct shared service in an otherwise wholly unicast peer-to-peer system. This approach was effective for relatively small systems but could not be extended to make general use of multicast communication (to reduce total bandwidth requirements). The MASSIVE-2 system added the concept of `third-party objects' which support the definition and management of multiple multicast groups for updates and continuous media distribution.

Flexible transmission bandwidth management with effective channel reservation techniques for NGSO MSS networks

This paper describes efficient transmission bandwidth management based on flexible channel assignment and effective grade of service (GOS) control methods for nongeostationary orbit mobile satellite service (NGSO MSS) networks. Our basic approach for the flexible channel assignment is to use linear programming (FLEXCA-LP), and to apply the column generation technique for further reduction of the total bandwidth requirement. These methods efficiently assign channels, taking account of moving spot beam coverage and dynamic traffic load variation for large-scale networks. The GOS is investigated for the channel assignment by FLEXCA-LP to make the GOS of ongoing calls better than that of fresh calls as stipulated in ITU-T Recommendations. We propose a few effective means to improve the results of FLEXCA-LP by reducing the disruption possibility of ongoing calls. One is to add channels utilizing a hysteresis concept. The others are effective use of GOS control techniques for NGSO MSS networks. These techniques are evaluated by a simulation study to identify promising techniques. Under time-variant conditions, we show that a reliable channel assignment plan is generated first by FLEXCA-LP considering the traffic load of fresh calls only and then by GOS control techniques to improve handover failure and call disruption rates.

Signal matrixing for directional reproduction of sound

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