Experimental evaluation of VBR transport over optical burst switching network

In this paper, we investigate the problem of optimal power control for multiuser variable bit rate (VBR) video streaming in a cellular network with orthogonal channels. We adopt a deterministic model for VBR video traffic that incorporates video frame and playout buffer characteristics, and formulate a constrained stochastic optimization problem. We then develop a majorization-based solution approach. For the case of a single VBR video session with relaxed peak power constraint, we develop a power optimal algorithm with low complexity. We prove the power optimality of the proposed algorithm and the uniqueness of the global optimum, and demonstrate that the proposed algorithm is also smoothness optimal. For the case of multiuser VBR video streaming, we develop a heuristic algorithm that selectively suspends some video sessions when the peak power constraint is violated. The proposed algorithms are evaluated with trace-driven simulations, and are shown to achieve considerable power savings and improved video quality over a conventional lazy scheme.

A majorization approach to downlink multiuser VBR video streaming

Transmission of variable bit rate (VBR) video, because of the burstiness of VBR video traffic, has high fluctuation in bandwidth requirement. Traffic smoothing algorithm is very efficient in reducing burstiness of the VBR video stream by transmitting data in a series of fixed rates. We propose in this paper a novel segment-based bandwidth allocation algorithm which dynamically adjusts the segmentation boundary and changes the transmission rate at the latest possible point so that the video segment will be extended as long as possible and the number of rate changes can be as small as possible while keeping the peak rate low. Simulation results showed that our approach has small bandwidth requirement, high bandwidth utilization and low computation cost.

802.11e HCCA (Hybrid coordination function Controlled Channel Access) exhibits good QoS provisioning for constant bit rate (CBR) video streams in a single collision domain. However, its performance degrades significantly for variable bit rate (VBR) video streams particularly in multi-collision domains. In addition, HCCA has the disadvantage of high complexity. In this paper, we introduce a deterministic backoff (DEB) method into the HCCA mechanism, which achieves virtual polling via carrier sense on the wireless channel. DEB inherits the merit of HCCA that achieves near collision-free channel access in single collision domain. It also exhibits robust performance in multi-collision domains. Simulation results show that DEB supports well both CBR and VBR video streams.

The Scalable Video Coding (SVC) extension of H.264/AVC has higher compression efficiency and supports a wide range of scalability modes. But, due to invent of improved compression tools like motion compensated predictions and hierarchical B-frames, SVC suffers from higher bit rate variabilities as compared to the preceding encoders, making its network transport more challenging. Different mitigation techniques employed in the codecs, to eliminate such traffic variabilities, increase computational load as well as introduce extra coding delays. We propose a novel mechanism to use Optical Burst Switching (OBS) Network inherent capability of aggregating incoming packets at its ingress edge node for smoothing of SVC variable bit rate traffic thus resulting in efficient transport of SVC encoded VBR stream over the OBS core network and also reducing computational complexities of SVC codec.

The constant and rapid expansion of the Internet at such a high rate has caused its traffic to double every four to six months. A large portion of this traffic is known to be multimedia and real time traffic, which has strict requirements in term of bandwidth, delay, jitter, and loss rate. Recent studies showed that constant bit rate (CBR) and variable bit rate (VBR) traffic can reduce both the transmission and storage costs for real time traffic. Other studies showed that optical burst switching (OBS) appears to be a promising switching technique for building the next-generation Internet infrastructure. In this paper, the compatibility between the requirements of CBR and VBR traffic and the services provided by the OBS networks are investigated. Initial finding shows that there is a need for quality of service (QoS) mechanisms to guarantee the CBR and VBR traffic characteristics and contract over OBS networks. This paper also discusses the issue of providing QoS over OBS network. The result of the study shows that the current QoS over OBS is insufficient for meeting the CBR and VBR traffic requirements if carried over the OBS networks. Nevertheless, it can be a motivation for further research.

All traffic models for MPEG-like encoded variable bit rate (VBR) video can be categorized into (i) data rate models (DRMs), and (ii) frame size models (FSMs). Almost all proposed VBR traffic models are DRMs. Since DRMs generate only data arrival rate, they are good for estimating average packet-loss and ATM buffer over-flowing probabilities, but fail to identify such details as percentage of frames affected. FSMs generate sizes of individual MPEG frames, and are good for studying frame loss rate in addition to data loss rate. Among three previously proposed FSMs: (i) one generates frame sizes for full-length movies without preserving GOP-periodicity; (ii) another generates frame sizes for full-length movies without preserving size-based video-segment transitions; and (iii) the third generates VBR video traffic for news videos from scene content description provided to it presupposing a proper segmentation. In this paper, we propose two segmentation techniques for VBR videos - (a) Equal Number of GOPs in all shot classes (ENG), and (b) Geometrically Increasing Interval Lengths for shot classes (GIIL). Each technique partitions the GOPs in the video into size-based shot classes. Frames in each class produce three data-sets one each for I-, B-, and P-type frames. Each of these data-sets can be modeled with an axis shifted Gamma distribution. Markov renewal processes model interclass transitions. We have used QQ plots to show visual similarity of model-generated VBR video data-sets with original data-set. Leaky-bucket simulation study has been used to show similarity of data and frame loss rates between model-generated videos and original video. Our study of frame-based VBR video revealed GIIL segmentation technique separates the I-, B-, and P- frames in well behaved shot classes whose statistical properties can be captured by Gamma-based models.

This paper presents an online measurement-based admission control scheme on the basis that the aggregate VBR video traffic is lognormally distributed. The proposed scheme consists of two components: measurement process and admission decision. The measurement process applies a linear Kalman filter to estimate statistical parameters of aggregate VBR video traffic. The estimated statistical parameters are used to calculate the effective bandwidth for admission decision. Variable bit rate (VBR) video traffic with high data rate is expected to occupy a dominant proportion of bandwidth for future wireless broadband home networks. To guarantee quality-of-service (QoS) of such VBR video streams, while achieving a high level of channel utilization, an efficient admission control scheme is urgently required, especially for emerging wireless multimedia indoor services, such as HDTV, online video game, etc. The proposed scheme is computationally efficient and accurate without much prior traffic information. Simulation results verify its effectiveness and show that it performs well for both a small number of connections and a large number of connections.

In this work a congestion level based optical burst assembly technique is proposed to be used in optical burst switching (OBS) networks. The effect of adaptive burstification duration (time threshold) and adaptive size threshold on the performance of OBS channel scheduling is analyzed under various traffic types. The proposed burst assembly technique varies (adapts) the time and size threshold values of the virtual queues at optical nodes considering the link congestion levels. Loss rates on the optical links are used to represent congestion levels and to arrange the time threshold and the size threshold values on the nodes which are incident with them. Three alternative size-time threshold values are employed based on the congestion level. Under heavy traffic, smaller threshold values are used. As the traffic becomes lighter, the threshold values are increased to allow longer burst generation and better channel utilization. Moreover, in order to make the implementation of optical nodes simpler, only the bursts of size mumin, SThshort, SThmedium, or STh long are generated. In the OBS network, a well-known and practical OBS technique, namely Horizon, is employed. The results are evaluated in terms of byte loss rate and compared with those obtained using a static (nonadaptive) burst assembly scheme. It is observed that the proposed technique dramatically decreases the overall byte loss rate while keeping the end-to-end delay in a feasible range

Nowadays, transferring a variable bit rate (VBR) video streaming on mobile devices is getting popular and necessary. Such traffic streams usually have stringent transferring requirements and in many cases they should be indeed delivered as they were generated. Hence, the IEEE 802.11e hybrid coordination function-controlled channel access (HCCA) access method was proposed to provide better quality-of-service (QoS) requirements for a real-time traffic in the wireless network. However, the reference scheduler of HCCA offered in the standard of the IEEE 802.11e is insufficient for the VBR video stream since it only considers a few characteristics. Hence, choosing the right parameters to meet the QoS requirements of the VBR stream remains an unsolved and opened issue. In this paper, we propose a pragmatic packet scheduling policy for the VBR stream and try to enhance the transmission efficiency for the IEEE 802.11e HCCA access method. The proposed scheduler considers not only traffic characteristics, but also the queue state and the real-time information of the packet. An efficiency analysis is provided to evaluate the transmission efficiency of the proposed scheduler. The result shows that our method can reach higher transmission efficiency than the reference scheduler. Simulations on the transmission of the VBR video stream are also performed to evaluate the performance of the proposed scheme. As it turns out, our design indeed provides a better performance than the reference and other well-known schedulers.

Optical burst switching (OBS) network has been proposed as a novel network scheme which can realize IP over WDM and also been regarded as the trend of the next optical generation network. In OBS network, burst contention phenomena may often occur at the output data channel in core routers and the contention can bring on the data losing. Optical composite burst switching (OCBS) has been regarded as an efficient approach for the resolution scheme in burst contention, which segments and drops the header of contending burst, but OCBS may bring unfairness to burst dropping, this unfairness causes the OBS network can't well support quality of service (QoS). The previous works that focus on the resolution approaches for the unfairness have some limitations and also could bring unfairness to OBS network. An improved resolution approach has been proposed to solve the unfairness of burst segmentation and dropping in optical burst switching multi-hop network in this paper, this approach not only could maintain the advantage of conventional resolution approach, which could make the packets loss probability coherence in multi-hop network but also could decreases the data losing and increase the throughput for OBS network. At last, some simulations prove the validity of the proposed approach and it has the theoretic meaning to design the real OBS network in practice.

Next-generation high-speed Internet backbone networks will be required to support a broad range of emerging applications which may not only require significant bandwidth, but may also have strict quality of service (QoS) requirements. Furthermore, the traffic from such applications are expected to be highly bursty in nature. For such traffic, the allocation of static fixed-bandwidth circuits may lead to the over-provisioning of bandwidth resources in order to meet QoS requirements. Optical burst switching (OBS) is a promising new technique which attempts to address the problem of efficiently allocating resources for bursty traffic. In OBS, incoming data is assembled into bursts at the edges of the network, and when the burst is ready to be sent, resources in the network are reserved only for the duration of the burst. The reservation of resources is typically made by an out-of-band one-way control message which precedes the burst by some offset time. By reserving resources only for the duration of the burst, a greater degree of utilization may be achieved in the network. This book provides an overview of optical burst switching. Design and research issues involved in the development of OBS networks are discussed, and approaches to providing QoS in OBS networks are presented. Topics include: - Optical burst switching node and network architectures - Burst assembly - Signaling protocols - Contention resolution - Burst scheduling - Quality of service in OBS networks

Studied in this paper is the convergence performance of three typical burst assembly mechanisms in optical burst-switching (OBS) networks, namely threshold-based, timer-based, and hybrid assembly algorithms. Burst assembly is an important function implemented at edge nodes in optical burst switching (OBS) networks. It can reduce the switching burden and overheads at the optical layer, by aggregating multiple packets from client networks to create a larger optical burst for transmission through the OBS network. Furthermore, burst assembly designed properly can reduce the self-similarity of traffic as traffic shaper. The main challenge in designing burst assembly is to balance the several opposing objectives: first, increasing the burst size; second, maintaining acceptable assembly delay introduced during burst assembly; thirdly, reducing the self-similarity as possible in case of self-similar traffic. Vital parameters, such as optical burst size and assembly delay, are examined by simulations under self-similar input traffic with a measured WAN packet size distribution. The balance between the burst size and the assembly delay for hybrid assembly is also discussed. The results show that the assembly threshold always keeps the burst size near the threshold while the assembly time-limit makes the burst size scattered and even split into multiple peaks when the incoming IP packet size is discrete. In addition, the self-similarity of input traffic has little impact on the burst size and the assembly delay for all three mechanisms. For hybrid assembly, when one of the assembly threshold and the assembly time-limit parameters is fixed, the burst size and the assembly delay are hard to improve by adjusting the other parameter when greater than a certain value

The current edge assembly granularity preserved beforehand in optical burst switched (OBS) networks lacks flexibility to actual network traffic and increases assembly overhead and delay. Offset time generating mechanism after traffic shaping increase network delay and cut down its robustness. Consequently, it is significant to present an effective dynamic burstification scheme to process real-time traffic, reduce assembly delay and provide QoS guarantee for different priority traffic at edge node. This paper focuses on dynamic burst assembly at edge node in optical burst switching networks, which can be implemented to improve the performance of the whole network. Based on traffic prediction, a new dynamic adaptive assembly mechanism on load estimate, termed Dynamic Adaptive Assembly (DAA), is proposed to reduce assembly delay, estimate real-time network traffic character and dynamically adjust Burst Assembly Time (BAT) at edge node. The dynamic range of BAT for four traffic classes is introduced to make compare among current and previous prediction with different prediction time under QoS based offset time. We investigate the influence of current and previous offered load with different prediction time and offset time. Simulation studies are carried out for various traffic classes. The results show that DAA can achieve little delay and provide adaptivity, flexibility and delay fairness for burst assembly.

Among the various issues lying in optical burst switching (OBS) networks, burstification, i.e., assembling multiple IP packets into bursts, is an important one. Between the two important aspects related to burst assembly, the burst assembly algorithm aspect has been extensively studied in the literature. However, as far as we know, there is no research about the burstification queue management (BQM) aspect, which refers to how many burstification queues (BQ) we should set at each OBS edge node and how to manage these BQs. Suppose there are G destinations (egress edge nodes) and the OBS network provides S different quality of service (QoS) classes. Traditionally, it is simply regarded that each ingress edge node needs G· S queues to sort incoming packets, one for each possible destination and QoS class. For simplicity, we call this policy the static dedicate BQM (SDB) policy. The SDB policy, though simple, lacks scalability since we have to add S BQs at each OBS edge node if an extra OBS edge node is added to the OBS network. To solve this problem, we propose in this paper two BQM policies: quasi-static BQM (QSB) policy and dynamic BQM (DB) policy. For the QSB policy, we derive the packet loss probability due to lacking BQs based on a Markov chain, from which we can work out the employed number of BQs for a given packet loss probability. Based on these results, the scalability of the QSB policy is also studied. With the DB policy, we not only can dynamically assign BQs for incoming packets, but also can dynamically allocate buffer capacity for each BQ by using a least-mean-square (LMS)-based linear prediction filter. The performance of the DB policy is investigated by analysis and extensive simulations. We also compared the performance of the QSB policy and the DB policy. Results from analysis and simulation demonstrate that the DB policy is the best.