Reliable Routing in Wireless Ad Hoc Networks: The Virtual Routing Protocol

A novel routing protocol for wireless, mobile ad hoc networks is presented. This protocol incorporates features that enhance routing reliability, defined as the ability to provide almost 100% packet delivery rate. The protocol is based on a virtual structure, unrelated to the physical network topology, where mobile nodes are connected by virtual links and are responsible for keeping physical routes to their neighbors in the virtual structure. Routes between pairs of mobiles are set up by using information to translate virtual paths discovered in the virtual structure. Route discovery and maintenance phases of the protocol are based on unicast messages travelling across virtual paths, with sporadic use of flooding protocol. Most flooding is executed in the background using low priority messages. The routing protocol has been evaluated and compared with the Dynamic Source Routing protocol and with the Zone Routing Protocol by means of simulation.

A Self-selection Technique for Flooding and Routing in Wireless Ad-hoc Networks

There is a fundamental difference between wireless and wired networks, since the latter employ point-to-point communication while the former use broadcast transmission as the communication primitive. In this paper, we describe an algorithm, called self-selection, which takes advantage of broadcast communication to efficiently implement the basic operation of selecting a node possessing some desired properties among all the neighbors of the requestor. Self-selection employs a prioritized transmission back-off delay scheme in which each node’s delay of transmitting a signal is dependent on the probability of the node’s ability to best perform a pertinent task, and in turn, enables the node to autonomously select itself for the task. We demonstrate the benefits of self-selection in two basic wireless ad hoc network communication algorithms: flooding and routing. By relating back-off delay to the signal strength of a received packet, we design an efficient variant of conventional flooding called Signal Strength Aware Flooding. By using distance-to-destination to derive back-off delay, we design a novel and fault-tolerant wireless ad hoc network routing protocol named Self-Selective Routing.

Routing protocols in wireless mesh networks: challenges and design considerations

Wireless Mesh Networks (WMNs) are an emerging technology that could revolutionize the way wireless network access is provided. The interconnection of access points using wireless links exhibits great potential in addressing the “last mile” connectivity issue. To realize this vision, it is imperative to provide efficient resource management. Resource management encompasses a number of different issues, including routing. Although a profusion of routing mechanisms has been proposed for other wireless networks, the unique characteristics of WMNs (e.g., wireless backbone) suggest that WMNs demand a specific solution. To have a clear and precise focus on future research in WMN routing, the characteristics of WMNs that have a strong impact on routing must be identified. Then a set of criteria is defined against which the existing routing protocols from ad hoc, sensor, and WMNs can be evaluated and performance metrics identified. This will serve as the basis for deriving the key design features for routing in wireless mesh networks. Thus, this paper will help to guide and refocus future works in this area.

Quick patching: an overlay multicast scheme for supporting video on demand in wireless networks

Many overlay multicast schemes have been proposed recently at the application level to support video-on-demand service over the Internet. With the proliferation of mobile devices and the increasing coverage of high speed wireless networks, such services are likely to be extended to support clients connected to the Internet through a wireless last hop. However, existing application level multicast schemes are not designed to handle the characteristics of the noisy wireless links. In this paper we propose an overlay multicast scheme called Quick Patching which arranges additional patch streams to clients under poor link conditions to improve their clients’ viewing quality. We demonstrate through extensive simulation experiments that Quick Patching is not only scalable, but can also sustain the required viewing quality under different network conditions including fluctuating error conditions as well as heterogeneous user viewing quality requirements.

On scheduling and clustering in hierarchical TH-PPM UWB wireless ad hoc networks

Ultra wideband (UWB) systems are considered as the key wireless infrastructure platforms for efficient short-range communications. In particular, the UWB based mobile computing systems are envisioned to be attractive solutions to various ad hoc networking applications. However, due to UWB’s unique physical characteristics, the traditional resource management schemes for ad hoc networks cannot be applied to UWB based systems directly. In this paper, we consider the bandwidth scheduling problem in a UWB based hierarchical wireless ad hoc network, which is typically used in an enterprise-scale mobile computing environment. Based on the mathematical analysis and the computer simulations, it is demonstrated that our proposed scheduling scheme exhibits close-to-optimal performance governed by the proportional fairness (PF) constraint. Moreover, a novel self-organized clustering method is designed to improve the system throughput while meeting the PF constraint. Simulation results suggest that the proposed clustering method is effective under various system configurations.

A Minimum Cut Interference-based Integrated RWA Algorithm for Multi-constrained Optical Transport Networks

Advances in optical technologies have enabled the deployment of wavelength division-multiplexed (WDM) transmission systems capable of providing huge amounts of bandwidth across long distances. In this scenario, dynamic routing for direct provisioning of optical paths at the WDM layer becomes a challenging problem. Any distributed algorithm for routing dynamic traffic demands on optical transport infrastructures should be simple, flexible, efficient and scalable. The contribution of this paper is a novel integrated routing and grooming scheme for setting-up bandwidth guaranteed paths on hybrid wavelength and label switched networks. Our proposal exploits and refines the minimum interference routing idea according to an improved and re-optimized resource and traffic-aware approach, where critical links are detected and weighted according to a low complexity all-pairs minimum cut strategy that substantially reduce the overall number of calculations and hence the computational cost. The valuable results achieved in the comparison against other well-known reference techniques clearly demonstrate that our algorithm is very time-efficient while performing better in terms of blocking probability.

Incentive mechanism for the CoopNet network

Selfish behavior and the limited time peers stay connected to the system are two major factors which significantly impact the efficiency of peer-to-peer networks with media streaming. This paper introduces an incentive mechanism to the CoopNet Network, which employs multiple distribution trees for the delivery of media streams, in order to address both problems. The mechanism comprises a barter trade economy-based component and a reputation-based remuneration component. Several questions are addressed in the paper such as the percentage of cooperative peers necessary to provide quality of service and whether or not it is worthwhile increasing the duration of sessions in order to reduce disruptions in multicast trees. Simulation results show that the barter trade component is essential to make peer-to-peer networks feasible for the provisioning of video on demand services, while the reputation component is advantageous only when arrival rates are reasonably high.

A hybrid multicast connectivity solution for multi-party collaborative environments

In multi-party collaborative environments, a group of users can share multiple media streams via IP multicasting. However, despite of the efficiency of IP multicast, it is not widely available and alternative application-layer multicast approaches are introduced. Application-layer multicast is advantageous, however, it incurs additional processing delays. In this paper, we present a new hybrid-style application-layer multicast solution that satisfies both network efficiency and easy deployment. We achieve this goal by connecting multicast islands through UDP tunnels employing UMTP (UDP multicast tunneling protocol). We also design a MPROBE protocol to remove multicast loop among multicast island in real Internet. We verify the feasibility of the proposed solution by implementing a prototype tool, AG Connector, that works on Access Grid multi-party collaborative environment.

EPCRTT-based smoothing and multiplexing of VBR video traffic

Applying video smoothing techniques to real-time video transmission can significantly reduce the peak rate and rate variability of compressed video streams. Moreover, statistical multiplexing of the smoothed traffic can substantially improve network utilization. In this paper we propose a new smoothing scheme, which exploits statistical multiplexing gain that can be obtained after smoothing of individual video streams. We present a new bandwidth allocation algorithm that allows for responsive interactivity. The local re-smoothing algorithm is carried out using an iterative process. In the proposed scheme the smoothed video streams are divided into fixed intervals and then a new transmission schedule for each interval is calculated. The problem of applying an optimal transmission schedule for aggregated smoothing video streams is shown to be NP-hard problem. Partitioning the whole stream into sections enables parallel processing of the smoothing algorithm in real-time before transmission. This approach allows partial transmission of the multiplexed stream while smoothing other intervals. The simulation results show a significant reduction in peak rate and rate variability of the aggregated stream, compared to the non-smoothing case. Therefore the proposed scheme allows us to increase the number of simultanusally-served video streams.

An address assignment for the automatic configuration of mobile ad hoc networks

Mobile ad hoc networks (MANETs) are infrastructure-less, multi-hop wireless networks, which can be deployed without any pre-existing setup. MANETs are mobile in nature and any node can join and leave the network at any time. Due to mobility, MANETs must be able to configure themselves without human intervention. Configuration (such as address assignment) of a node in such a network is an important issue. In this paper, we present a solution for address assignment, which is distributed in nature and can be used for IP address configuration in MANETs. Each node can allocate the address independent of others. Although our solution uses broadcast messages, results show that by fixing a few parameter values we can reduce the number of broadcast messages. We simulate the protocol and results show that our solution yields better performance those of the earlier algorithms.

EMMA: Epidemic Messaging Middleware for Ad hoc networks

The characteristics of mobile environments, with the possibility of frequent disconnections and fluctuating bandwidth, have forced a rethink of traditional middleware. In particular, the synchronous communication paradigms often employed in standard middleware do not appear to be particularly suited to ad hoc environments, in which not even the intermittent availability of a backbone network can be assumed. Instead, asynchronous communication seems to be a generally more suitable paradigm for such environments. Message oriented middleware for traditional systems has been developed and used to provide an asynchronous paradigm of communication for distributed systems, and, also for some specific mobile computing systems recently. In this paper, we present our experience in designing, implementing, and evaluating Epidemic Messaging Middleware for Ad hoc networks (EMMA), an adaptation of Java Message Service (JMS) for mobile ad hoc environments, discussing in detail the design challenges and the solutions that have been adopted.

A new model for time-series forecasting using radial basis functions and exogenous data

In this paper, we present a new model for time-series forecasting using radial basis functions (RBFs) as a unit of artificial neural networks (ANNs), which allows the inclusion of exogenous information (EI) without additional pre-processing. We begin by summarizing the most well-known EI techniques used ad hoc, i.e., principal component analysis (PCA) and independent component analysis (ICA). We analyze the advantages and disadvantages of these techniques in time-series forecasting using Spanish bank and company stocks. Then, we describe a new hybrid model for time-series forecasting which combines ANNs with genetic algorithms (GAs). We also describe the possibilities when implementing the model on parallel processing systems.

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Detecting repeats for video structuring

Television daily produces massive amounts of videos. Digital video is unfortunately an unstructured document in which it is very difficult to find any information. Television streams have however a strong and stable but hidden structure that we want to discover by detecting repeating objects in the video stream. This paper shows that television streams are actually highly redundant and that detecting repeats can be an effective way to detect the underlying structure of the video. A method for detecting these repetitions is presented here with an emphasis on the efficiency of the search in a large video corpus. Very good results are obtained both in terms of effectiveness (98% in recall and precision) as well as efficiency since one day of video is queried against a 3 weeks dataset in only 1 s.

Optimized scalable cache management for video streaming system

An important research issue in video streaming is how to efficiently utilize the network resources to provide clients instant access to multiple video objects. Caching strategy and transmission scheme are the two essential points inside the video streaming framework. Recent research efforts on them are not sufficient due to their inflexible support for scalable encoded video streams and heterogeneous requests from clients. In this paper, we propose an optimized caching strategy (OCS) and a scalable transmission scheme (STS) for scalable coded video streaming. By exploring the characteristics of video streaming workload and system design objectives, OCS and STS work efficiently to minimize both network bandwidth cost and user access latency. Firstly, we analyze the caching problem for the proxy-assisted video streaming system and derive a maneuverable caching scenario. Secondly, we develop an efficient transmission scheme for scalable coded videos. Thirdly, we formulate a multi-objective optimization model with closed-form expressions to obtain the optimized caching strategy. Finally, with designed algorithms, an excellent compromise between two competing objectives (minimizing the bandwidth cost and the access latency) is achieved. We start our evaluation by studying the optimized caching strategy for a single video object. Then we apply the strategy to multiple video objects and illustrate the tradeoff between the optimization objectives. Our evaluation results show that compared with other caching strategies, the proposed optimized scalable caching strategy can achieve a significant reduction in bandwidth cost with even a small proxy cache size. Meanwhile, the best performance (in terms of bandwidth cost) is obtained together with the proposed scalable batch-patching transmission scheme.

Hardware supported multicast in fat-tree-based InfiniBand networks

The multicast operation is a very commonly used operation in parallel applications. It can be used to implement many collective communication operations as well. Therefore, its performance will affect parallel applications and collective communication operations. With the hardware supported multicast of the InfiniBand Architecture (IBA), in this paper, we propose a cyclic multicast scheme for fat-tree-based (m-port n-tree) InfiniBand networks. The basic concept of the proposed cyclic multicast scheme is to find the union sets of the output ports of switches in the paths between the source processing node and each destination processing node in a multicast group. Based on the union sets and the path selection scheme, the forwarding table for a given multicast group can be constructed. We implement the proposed multicast scheme along with the OpenSM multicast scheme and the unicast scheme on an m-port n-tree InfiniBand network simulator. Several one-to-many, many-to-many, many-to-all, and all-to-many multicast cases are simulated. The simulation results show that the proposed multicast scheme outperforms the unicast scheme for all simulated cases. For one-to-many case, the performance of the cyclic multicast scheme is the same as that of the OpenSM multicast scheme. For many-to-many and all-to-many cases, the cyclic multicast scheme outperforms the OpenSM multicast scheme. For many-to-all case, the performance of the cyclic multicast scheme is a little better than that of the OpenSM multicast scheme.

Routing Management in the PSTN and the Internet: A Historical Perspective

Two highly visible public communication networks are the public-switched telephone network (PSTN) and the Internet. While they typically provide different services and the basic technologies underneath are different, both networks rely heavily on routing for communication between any two points. In this paper, we present a brief overview of routing mechanisms used in the PSTN and the Internet from a historical perspective. In particular, we discuss the role of management for the different routing mechanisms, where and how one is similar or different from the other, as well as where the management aspect is heading in an inter-networked environment of the PSTN and the Internet where voice over IP (VoIP) services are offered.

Adaptive two-way uniform partition for multicast routing problem with separate paths in ad hoc networks

Finding a near-optimal routing solution for multicast requests is a challenge for supporting different multicast applications including video and group communications over wireless ad hoc networks. A heuristic partitioning algorithm for solving the multicast routing problem with separate paths in ad hoc networks is presented. We consider scheduling a set of multicast requests which may have a source node with multiple destinations respectively through a wireless network. Our heuristic method for partitioning arbitrary routing requests is both effective in finding a near-optimal solution, and efficient to solve large multicast requests. Our simulation shows that the average overall latency reduces up to 38%. We also find that the handling scales up well from 8 nodes to 64 nodes.     

Efficient video encryption scheme based on advanced video coding

A video encryption scheme combining with advanced video coding (AVC) is presented and analyzed in this paper, which is different from the ones used in MPEG1/2 video encryption. In the proposed scheme, the intra-prediction mode and motion vector difference are encrypted with the length-kept encryption algorithm (LKE) in order to keep the format compliance, and the residue data of the macroblocks are encrypted with the residue data encryption algorithm (RDE) in order to keep low cost. Additionally, a key distribution scheme is proposed to keep the robustness to transmission errors, which assigns sub-keys to different frames or slices independently. The encryption scheme’s security, time efficiency and error robustness are analyzed in detail. Experimental results show that the encryption scheme keeps file format unchanged, is secure against replacement attacks, is efficient in computing, and is robust to some transmission errors. These properties make it a suitable choice for real-time applications, such as secure IPTV, secure videoconference or mobile/wireless multimedia, etc.

An economic incentive model for encouraging peer collaboration in mobile-P2P networks with support for constraint queries

In mobile ad hoc peer-to-peer (M-P2P) networks, economic models become a necessity for enticing non-cooperative mobile peers to provide service. M-P2P users may issue queries with varying constraints on query response time, data quality of results and trustworthiness of the data source. Hence, we propose ConQuer, which is an economic incentive model for the efficient processing of constraint queries in M-P2P networks. ConQuer also provides incentives for peer collaboration in order to improve data availability. The main contributions of ConQuer are three-fold. First, it uses a broker-based economic M-P2P model for processing constraint queries via a Vickrey auction mechanism. Second, it proposes the CR*-tree, a dynamic multidimensional R-tree-based index for constraints of data quality, trust and price of data to determine target peers efficiently. The CR*-tree is hosted by brokers, who can sell it to other peers, thereby encouraging the creation of multiple copies of the index for facilitating routing. Third, it provides incentives for peers to form collaborative peer groups for maximizing data availability and revenues by mutually allocating and deallocating data items using royalty-based revenue-sharing. Such reallocations facilitate better data quality, thereby further increasing peer revenues. Our performance study shows that ConQuer is indeed effective in answering constraint queries with improved response time, success rate and data quality, and querying hop-counts.

Adaptive training of video sets for image recognition on mobile phones

We present an enhancement towards adaptive video training for PhoneGuide, a digital museum guidance system for ordinary camera-equipped mobile phones. It enables museum visitors to identify exhibits by capturing photos of them. In this article, a combined solution of object recognition and pervasive tracking is extended to a client–server-system for improving data acquisition and for supporting scale-invariant object recognition. A static as well as a dynamic training technique are presented that preprocess the collected object data differently and apply two types of neural networks (NN) for classification. Furthermore, the system enables a temporal adaptation for ensuring a continuous data acquisition to improve the recognition rate over time. A formal field experiment reveals current recognition rates and indicates the practicability of both methods under realistic conditions in a museum.

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