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The failure of legacy packet markers, such as the Single Rate Three Color Marker (SRTCM) and the Two Rate Three Color Marker (TRTCM), to protect important data from being dropped, renders a poor delivery of video quality over Differentiated Services (DiffServ) networks due to the hierarchical structure of MPEG video. Therefore, we propose a content-aware packet marking scheme, which we call Two Markers System (TMS), to improve the delivery quality of MPEG video streams. TMS places marker modules at both the video source and the edge of a DiffServ network. The source marking modules act at the application-level to set an importance indicator in the IP header of the MPEG frame packet by evaluating the contribution of the packet to the expected picture quality perceived by an end user. Meanwhile, at the edge of the DiffServ network, the Enhanced Token Bucket Three Color Marker (ETBTCM) is proposed to perform packet marking at the network-level in accordance with the pre-assigned importance of individual video frame packets. When the traffic flow is measured as out-of-profile, the less important packets will be marked with higher probability than the more important ones. Therefore, in the event of network congestion, less important frame packets can be dropped before more important ones. Consequently, a better delivered video quality can be provided. Further, due to the convenience offered by wireless networks, more users choose mobile devices to connect to the Internet. Therefore, a Video Differentiator is suggested, placed at the entry to the IEEE 802.11e wireless network, to provide traffic differentiation and better service for video traffic. We use authentic MPEG4 video traffic traces to evaluate this framework. Results show that better video quality can be delivered over our proposed new framework.

Recent developments in hardware, software and communication technologies have resulted in increasing interest in the use of wireless local area networks (WLANs). Mobile devices with embedded WLAN functionality are becoming increasingly popular. Such devices must be designed to support applications that require high quality of service (QoS) and have favorable to maximize battery capacity. The resources of queues in IEEE 802.11e networks may be wasted by the transmission of information that is useless to the receiver. This work develops a frame-based mapping mechanism (FBM) that exploits a different method to process I/P/B video frame packets. FBM refers to the dropping of arriving packets if the preceding packets in the same video frame have been dropped. When fragmented packets of a single frame are allocated to different access categories (AC) queues, out-of-order delivery may occur. Hence, FBM tries to treat all fragmented packets of each video frame equally and allocates them to the same AC queue if possible. The simulation results demonstrate that transmission by the FBM is more efficient than that by other mechanisms, such as EDCA (Enhanced Distributed Channel Access), static mapping and adaptive mapping, suggesting that the energy of a device is not wasted in the transmission of useless video data in WLANs.

Due to the very large and quick growth of the wireless network and increasing demand for multimedia information on the web, video transmission over the wireless network has received tremendous attention from academe and industry. Transmission of ...

In this study, we develop a hierarchical packet predropping (HPPD) approach that exploits different methods to process intra-coded (I)/predictive-coded (P)/bidirectionally predictive-coded (B) video frame packets to improve the video transmission quality in heavily loaded IEEE 802.11e wireless local area networks (WLANs). It is not easy to transmit packets in WLANs with a heavy traffic load. Efficient transmission of video packets is important for improving the quality of video transmission. If the network becomes congested, important packets may be dropped. Further, video packets tend to be affected considerably more than data packets. Therefore, controlling the traffic of insignificant packets to avoid the transmission of useless data can improve the quality of video transmission. On the basis of this concept, in this paper, we propose a strategy that is different from the approaches proposed in earlier studies. First, identification of the dependence of video frames in a group of pictures (GOP) can prevent the transmission of useless data. Thus, the transmission channel resources are economized by avoiding the transmission of undecodable video frames. Second, in heavily loaded WLANs, it is not sufficient to utilize the queues to transmit important video frame packets. HPPD adopts the method of an aggressive drop of unimportant packets to retain the transmission channel resources for important video packets. Experiments have demonstrated that in heavily loaded WLANs, the Peak Signal to Noise Ratio (PSNR) for the case when the HPPD mechanism is adopted is better than that when enhanced distributed channel access (EDCA), adaptive mapping, or a novel mapping mechanism is used.

In multimedia communications, different characteristics of wireless channel error models lead to different effects on the delivered video quality level. In this paper, we analyze the effects of wireless channel errors on the quality of MPEG video stream. First, we use ...

Software-defined networking offers numerous benefits against the legacy networking systems through simplifying the process of network management and reducing the cost of network configuration. Currently, the management of failures in the data plane is limited to two mechanisms: proactive and reactive. Such failure recovery techniques are activated after occurrences of failures. Therefore, packet loss is highly likely to occur as a result of service disruption and unavailability. This issue is not only related to the slow speed of recovery mechanisms, but also the delay caused by the failure detection process. In this paper, we define a new approach to the management of fault tolerance in software-defined networks where the goal is to eliminate the convergence process altogether, rather than speed up failure detection and recovery. We propose a new framework, called Smart Routing, which works based on the forewarning signs on failures in order to compute alternative paths and isolate the risky links from the routing tables of the data plane devices. We validate our framework through a set of experiments that demonstrate how the underlying model runs.

The failure of legacy packet markers, such as the Single Rate Three Color Marker (SRTCM) and the Two Rate Three Color Marker (TRTCM), to protect important data from being dropped, renders a poor delivery of video quality over Differentiated Services (DiffServ) networks due to the hierarchical structure of MPEG video. Therefore, we propose a content-aware packet marking scheme, which we call Two Markers System (TMS), to improve the delivery quality of MPEG video streams. TMS places marker modules at both the video source and the edge of a DiffServ network. The source marking modules act at the application-level to set an importance indicator in the IP header of the MPEG frame packet by evaluating the contribution of the packet to the expected picture quality perceived by an end user. Meanwhile, at the edge of the DiffServ network, the Enhanced Token Bucket Three Color Marker (ETBTCM) is proposed to perform packet marking at the network-level in accordance with the pre-assigned importance of individual video frame packets. When the traffic flow is measured as out-of-profile, the less important packets will be marked with higher probability than the more important ones. Therefore, in the event of network congestion, less important frame packets can be dropped before more important ones. Consequently, a better delivered video quality can be provided. Further, due to the convenience offered by wireless networks, more users choose mobile devices to connect to the Internet. Therefore, a Video Differentiator is suggested, placed at the entry to the IEEE 802.11e wireless network, to provide traffic differentiation and better service for video traffic. We use authentic MPEG4 video traffic traces to evaluate this framework. Results show that better video quality can be delivered over our proposed new framework.

This paper addresses the QoS support issue of IEEE 802.11e in multirate networks. Prior researches focused on the "performance anomaly" problem without QoS consideration. We show the QoS support is insufficient in the current 802.11e standard and related methods make it worse by using NS-2 simulation tests. We propose a hybrid method that maintains the quality of highest priority traffic and enhance the system performance concurrently. We also compare its performance with other proposed methods. Our results demonstrate that our proposed hybrid method can efficiently support the time constraints of voice flows in various network conditions. Moreover, the system throughput is improved by the hybrid method when compared to the IEEE 802.11e standard.

Robotic devices are increasingly a research focus for liberation of humans from time-consuming traditional tasks, but the cost and complexity of such devices remain a daunting issue. This paper proposes a simple and cost-effective demonstration prototype system composed of a wireless module, sensors and a mobile robotic cart which prowls the target environment, for example a home or professional healthcare room for the elderly. Using low cost off-the-shelf components, the presented system is configured as a fire detector/alarm/extinguisher, but is adaptable to many other configurations. It demonstrates that, with adequate planning and forethought, sophisticated robotic performance at low material and developmental cost can be obtained for common household, healthcare and industrial applications.

IEEE 802.11e has been introduced to support quality of service (QoS) in WLANs by allocating different traffics to four access categories. Cross-layer design is a method to improve the transmission quality of multimedia over wireless networks. However, when the fragmented packets of a single frame are allocated to different AC queues, out-of-order delivery may occur. Then the receiving node requires more buffer space to absorb the outof-order packets. Therefore, even with a significance classification mechanism, the quality of the video transmission may still be limited due to the occurrence of out-of-order delivery and the transmission of information that becomes useless to the receiver. Therefore, this work developed a novel mapping mechanism (NMM) to improving the quality of MPEG-4 video delivery over IEEE 802.11e networks. The NMM considers the action that was taken on packet of the video frame that had been previously transmitted to resolve the out-of-order delivery by allocating them to the same AC queue as the previously process if possible. Furthermore, the proposed mechanism NMM takes more aggressive scheme to protect more important frame packets from being dropped. In order to evaluate the quality of MPEG-4 video delivery over IEEE 802.11e networks by the proposed mechanism, this work adopted two evaluation metrics, which is called Peak to Signal Noise Ratio (PSNR) and the ratio of frames loss. The simulation results demonstrate that, in terms of both PSNR and the ratio of frames loss, the proposed scheme outperforms exiting schemes such as EDCA (Enhanced Distributed Channel Access) and adaptive mapping.

Video streaming has emerged as a killer application in today's Internet, delivering a tremendous amount of media contents to millions of users at any given time. Such a heavy traffic load demands an effective routing method. In this paper, an effective routing method, named GA-SDN, is developed based on software defined network (SDN) technique. To facilitate the researchers in this field to evaluate the video delivery quality over SDN, an evaluation framework and its associated source codes are provided. The framework integrates the H.264 Scalable Video coding streaming Evaluation Framework (SVEF) with the Mininet emulator. Through this framework, video processing researchers can evaluate their proposed coding algorithms in an SDN-enabled network emulator, while network operators or executives can evaluate the impact of real video streams on the developing network architectures or protocols. Experiment results demonstrate the usefulness of myEvalSVC_SDN and prove that GA-SDN outperforms traditional Bellman-Ford routing algorithm in terms of packet drop rate, throughput, and average peak signal-to-noise ratio.

An advanced metering infrastructure (AMI) consists of a meter data management system, a concentrator, and a meter. Each component can communicate with all other components, through either wired or wireless connections. In an AMI local area networks, various protocols, such as Zigbee, WiFi, and power-line communication, have the potential for used in AMI communication. Of these protocols, Zigbee offers self-constructing networks, low costs, and superior safety levels. Zigbee is adopted as the LAN communication protocol because of these advantages in this study. In a LAN, a concentrator may encounter many emergent situations, any of which might cause the concentrator to lose its network connection function. Consequently, additional time is required for network construction, which tends to reduce the reliability of smart grids with LANs of this type. To solve these issues, this paper proposes fast join process (FJP) and enhanced FJP to shorten the time of Zigbee network construction. The strategy employed in this paper is to let every meter join a specified concentrator. The proposed FJP does not scan unnecessary channels. By simplifying association message exchange, we further propose a new method called the enhanced FJP. Using these methods, not only can message flow be managed easily, but the time of network construction can also be improved.

Data center networks (DCNs) are the backbone of many cloud and Internet services. They are vulnerable to link failures, that occur on a daily basis, with a high frequency. Service disruption due to link failure may incur financial losses, compliance breaches and reputation damage. Performance metrics such as packet loss and routing flaps are negatively affected by these failure events. We propose a new Bayesian learning approach towards adaptive path allocation that aims to improve DCN performance by reducing both packet loss and routing flaps ratios. The proposed approach incorporates historical information about link failure and usage probabilities into its allocation procedure, and updates this information on-the-fly during DCN operational time. We evaluate the proposed framework using an experimental platform built with the POX controller and the Mininet emulator. Compared with a benchmark shortest path algorithm, the results show that the proposed methods perform better in terms of reducing the packet loss and routing flaps.

The rapid evolution of information technology has compelled the ubiquitous systems and computing to adapt with this expeditious development. Because of its rigidity, computer networks failed to meet that evolvement for decades, however, the recently emerged paradigm of software-defined networks gives a glimpse of hope for a new networking architecture that provides more flexibility and adaptability. Fault tolerance is considered one of the key concerns with respect to the software-defined networks dependability. In this paper, we propose a new architecture, named THRIFTY, to ease the recovery process when failure occurs and save the storage space of forwarding elements, which is therefore aims to enhance the fault tolerance of software-defined networks. Unlike the prevailing concept of fault management, THRIFTY uses the Edge-Core technique to forward the incoming packets. THRIFTY is tailored to fit the only centrally controlled systems such as the new architecture of software-define...

Software Defined Networking is a new networking paradigm that has emerged recently as a promising solution for tackling the inflexibility of the classical IP networks. The centralized approach of SDN yields a broad area for intelligence to optimise the network at various levels. Fault tolerance is considered one of the most current research challenges that facing the SDN, hence, in this paper we introduce a new method that computes an alternative paths reactively for centrally controlled networks like SDN. The proposed method aims to reduce the update operation cost that the SDN network controller would spend in order to recover from a single link failure. Through utilising the principle of community detection, we define a new network model for the sake of improving the network's fault tolerance capability. An experimental study is reported showing the performance of the proposed method. Based on the results, some further directions are suggested in the context of machine learning towards achieving further advances in this research area.

With continuing advances in network and video and audio techniques, and the proliferation of mobile applications, the demand for multimedia streaming has grown exponentially in recent years. This study therefore proposes a multipath transmission scheme, designated as Weighted Stochastic Multipath (WSMP) scheme, for enhancing the efficiency of multimedia streaming transmissions by utilizing the data flow control ability in Software Defined Networks (SDNs). The proposed method searches for multiple transmission paths meeting the imposed QoS constraints, and then uses the stochastic switching mechanism based on the OpenFlow protocol in SDNs to transmit the data packets of single data flows through the multiple paths. In addition, the Analytic Hierarchy Process (AHP) method is used to set the transmission weights of the different paths in such a way as to optimize the transmission performance. Thus, the proposed multipath transmission scheme not only can avoid single path interruptions ...

Due to intra-flow and inter-flow interference problems, the throughput performance decreases dramatically in a multi-hop wireless network. These two kinds of bandwidth unfair sharing problems could cause serious collisions and congestion, hence affecting the performance of multi-hop wireless networks. That is to say, data packets that need to traverse more hops to arrive at the destination will get lower throughput and result in the interflow fairness problem. Furthermore, the quality of video transmission is especially poor in traditional multi-hop wireless network environments. Therefore, in this paper, we propose a virtual queue management scheme that does not require the modification of any communication protocol. According to the number of flows, it adjusts the queue management scheme to achieve each flow's fair sharing of channel resource. It also improves the quality of video transmission. Through NS2 simulations, the results show that our proposed scheme can mitigate the inter-flow fairness problem and effectively improves the quality of video transmission.

The increasing complexity of modern day networked applications and the massive demand on the Internet resources has reignited interest and concern in the underlying networking infrastructures and their ability to cope with such complexity and adapt to the demands of the business applications, particularly where such applications require a high degree of robustness and reliability. As a result, software-defined networking has emerged as a promising approach to the definition of network architectures that could carry a high degree of adaptability and robustness reminiscent of the future Internet. Fault tolerance and network updates are considered two of the current research challenges that hamper the growth of software-defined networking in this area. Therefore, this paper represents a step toward tackling these two issues in the context of single link failures. Our main contribution lies in the definition of new algorithms that aim to enhance the problem of finding alternative paths in large-scale networks with minimal cost and time-to-update factors. The new solution aims at increasing the efficiency of flow operation reduction during link failures. We evaluate our framework and show how its implementation results in improved efficiency.