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Intelligent Transport System (ITS) provides an efficient solution to road safety traffic. To support safety applications, cellular vehicle-to-everything (C-V2X) is developed by third generation partnership project (3GPP). C-V2X support two modes of communication as mode 3 and mode 4. In mode 4, vehicles reserve the resources based on their local observations using semi-persistent scheduling (SPS). If two vehicles, simultaneously select the same resources, it will lead to resource contention. This arises the consensus problem. To overcome this, in this paper we proposed the multi agent collaborative deep reinforcement learning based scheme. A single deep Q network (DQN) is trained for each zone. Each zone is preconfigured with resources which constitute a resource pool. A reward function is shared between the vehicles that belong to the same pool. This approach makes the vehicles to collaborate rather than compete in selecting the resources for their transmission. The proposed scheme is compared with the random resource allocation in C-V2X. The results show that the proposed scheme outperforms even in dense vehicular environment.

The smart home is extensively preferred, as it improves the residents’ lifestyles involving many disciplines, i.e., security, lighting, etc. The wide expansion of smart home increases size and complexity in network, therefore, it is crucial to tackle the numerous challenges associated to data loss attributable to efficient energy and interference management. In this research article, a specific smart home control system is proposed using ZigBee based on co-coordinator. The proposed system is composed of three components: 1) interference controlling system to control wireless interference among heterogeneous devices, 2) advanced energy management system to optimize the energy utilization and integrated the light source with sunlight, and 3) management control agent to manage the electronic devices and time efficiently. The efficient computer simulation is also executed to test the efficiency of the proposed scheme. The analysis and results reveal that the proposed system is efficient enough to reduce the power consumption of smart home devices. Moreover, it is further experienced that the proposed scheme is less affected by the interference.

Recently, as interest in IoT (Internet of Things) increase, research and standardization of a new protocol which reflects the characteristics of IoT has progressed. Among them, RPL(IPv6 for Low-Power Lossy Network) is a standardized routing protocol for IoT. RPL utilizes DIO (DODAG Information Object) messages which is flooded from the sink node to the whole network for path establish and maintenance. However, in large scale networks, not only a long time is required to propagate the DIO message to the whole networks but also a bottleneck effect around the sink node is occurred. Multi-sink based approaches which take advantage of reducing routing overhead and bottleneck effect are widely used to solve these problems. In this paper, we define 'unnecessary path update problems' that may arise when applying the RPL protocol to the multi sink based IoT networks and propose two methods namely Routing Metric based Path Update Decision method and Immediate Successor based Path Update Decision method for selective routing update.

Underwater Wireless Sensor Networks (UWSNs) have distinctive characteristics due to the use of acoustic signals as its physical medium for communications, including high propagation delay, limited bandwidth and high error rates. Hence, designing communication protocols, particularly, an efficient routing protocol for UWSNs is a challenging issue. Routing protocols can take advantage of the localization of sensor nodes. However, the localization itself is not impeccable in UWSNs. In this paper, we therefore propose a localization-free routing protocol named MRP (multi-layered routing protocol) for UWSNs. MRP utilizes super nodes in order to eliminate the need of localization. MRP works in two phases: Layering phase and Data forwarding phase. During layering phase, different layers are formed around the super nodes. In data forwarding phase, data packets are forwarded based on these layers. Through simulation study using NS-2 simulator, we proved that MRP contributes significant performance improvements against representative routing protocols.

One of principal design issues of a Wireless Sensor Network (WSN) for medical information systems is to classify received packets based on their priorities and guarantees so that they can be transmitted reliably, thus satisfying QoS requirements. In addition, when the target WSN requires multi-hop communications and the traffic load increases significantly, it is challenging to support both load balancing and suitable QoS at the same time. In this paper, we propose a new reliable protocol termed Cross-layer Channel Access and Routing (CCAR), which simultaneously supports both MAC and routing operations for medical-grade QoS provisions. CCAR initially determines the routing path with the lowest traffic load and low latency using newly defined channel quality factors. Concurrently, the source node allocates the predefined QoS Access Category to each packet and reserves the channel along the route. In addition, CCAR introduces an effective route maintenance scheme to avoid link failures in bottlenecked intermediate nodes, which prevents unnecessary packet drops and route rediscovery evocations. Finally, through both simulation studies and real test-bed experiments, we evaluate the performance of CCAR by comparing it with other conventional protocols, demonstrating that the proposed protocol can more efficiently support medical-grade QoS packets, especially when the network is heavily loaded.

The most well-known high-energy physics collaboration, the Large Hadron Collider (LHC), which is based on e-Science, has been facing several challenges presented by its extraordinary instruments in terms of the generation, distribution, and analysis of large amounts of scientific data. Currently, data distribution issues are being resolved by adopting an advanced Internet technology called software defined networking (SDN). Stability of the SDN operations and management is demanded to keep the federated LHC data distribution networks reliable. Therefore, in this paper, an SDN operation architecture based on the distributed virtual network operations center (DvNOC) is proposed to enable LHC researchers to assume full control of their own global end-to-end data dissemination. This may achieve an enhanced data delivery performance based on data traffic offloading with delay variation. The evaluation results indicate that the overall end-to-end data delivery performance can be improved over multi-domain SDN environments based on the proposed federated SDN/DvNOC operation framework.

Various needs of new network services have rapidly proliferated over the past few years. To catch up with major requirements, that is, time-to-research and time-to-collaboration, we propose a fast virtual dedicate network generation algorithm based on network abstraction with pruning strategy, unification of multiple links, and an improved spanning tree algorithm.

The potentials of Internet of Things (IoT) are unlimited and a lot of IoT based applications have been recently explored. In IoT networks, anything can be enabled with network connectivity anytimes, and at anyplace. Path establishement from the source to the sink is an integral part of the IoT network. IPv6 Routing protocol for Low-power and Lossy networks (RPL) is a promising routing protocol for the constrained IoT networks. It establishes a robust upward paths towards the sink, however, the downward paths depend on source routing techniques implemented by the sink. In RPL, two operational modes are defined for intermediate nodes, i.e., storing mode and non-storing mode. A node working in storing mode can provide local repair and partial source routing in case of next-hop failure. However, due to the limited memory and computation power of the nodes, most of the nodes operate in non-storing mode. In this paper, we propose a method to optimize the operational mode decision of the nodes in the downward paths.

Hybrid network infrastructure has been deployed as the most important technology for the advanced research networking community such as Internet2, SURFnet, etc. However, further research needs to be performed in terms of feasible design and implementation of architecture for inter-domain collaborative network infrastructure, which is essential to end-to-end collaborative research based on high-end applications. In this paper, we suggest a framework for distributed and virtual network operations based on hybrid research networks and efficient cooperation between multi-domain hybrid networks, which aims to provide collaborative network environment for high-end applications. Suggested framework is designed to adopt decentralized model of multi-domain hybrid research network management. A collaborative and distributed virtual model that is characterized by cooperation among hybrid research networks that insist on maintaining their autonomy and control, can also contribute for researchers and other end-users to manage and operate their own virtual networks.

In this paper, we propose a routing protocol for WMNs to provide passengers in public transportation vehicles (e.g., bus and tram) with Internet access service. In order to support end users with a reliable Internet connection despite the mobility of vehicles, we assume that mesh router, called mobile mesh router (MMR), is installed in a vehicle and manages a route to Internet Gateway (IGW). We therefore propose an efficient routing protocol and its routing metric, called ETT-TR, considering trajectory information of vehicle as well as link quality in order to find a route between them. Using NS-2 simulations, we observe that our proposed routing protocol reduces the end-to-end delay and improves throughput performance.

In vehicular ad hoc networks, most of critical applications involved with safety rely on reliable broadcast communications with low latency. Recently, repetition-based protocols have been proposed to meet the requirements of timeliness and reliability for broadcasting. In these protocols, a sender repeatedly retransmits the broadcast message during the lifetime of the message. However, existing protocols face serious problems such as deterioration of the signal quality caused by wireless fading. In particular, since excessive repetitions might cause network congestion and waste channel resources, reliability of broadcasting should be achieved with as small a number of repetitions as possible. In this paper, we therefore propose a novel repetition-based broadcast protocol which exploits a cooperative diversity technique (called RB-CD) making a small number of repetitions robust for wireless fading. To support this cooperative diversity, neighboring nodes transmit the same message almost simultaneously (that is, using the same repetition pattern for each other) in order to form a virtual antenna array. The virtual antenna array achieves a diversity gain at the receivers. In the RB-CD protocol, the virtual antenna array consists of the source and some of its neighbors (called relays) which participate in repeating the transmission of a broadcast message. In addition, a new distributed relay selection algorithm is introduced in the RB-CD protocol. From the ns-2 simulation results, we verified that RB-CD provides a more reliable broadcasting service due to its capability of exploiting cooperative diversity.

Mobile computing has become very pervasive, where the number of electronic devices equipped with wireless capabilities has increased significantly in recent years. This poses serious demands on wireless, mobile and self-organizing networks. Despite the fact that devices are getting smaller and more powerful, advances in battery technology have not yet reached the stage where devices can autonomously operate for days. Therefore, devices for self-organizing networks will strongly rely on the efficient use of their batteries. We present a cluster-based low-complexity routing algorithm for self-organizing networks of mobile nodes. Our proposed algorithm, called Cluster-based Energy-saving Routing Algorithm (CERA), allows mobile nodes to autonomously create clusters to minimize the power consumption. CERA is implemented as two separate protocols: the intra-cluster data-dissemination protocol, and the inter-cluster routing protocol. We present an extensive analysis of the overall protocol architecture by varying the critical factors related to protocol behavior. As a result, the CERA implementation generally saves up to 25% of energy, while keeping the overhead, in terms of energy consumption, acceptably low.

The Grid is an infrastructure to connect heterogeneous resources that are scattered over areas with high-speed network and to cooperate with each other. To support Grid applications, network resources should be managed, since the network has to be safe and reliable. The Grid Monitoring Architecture Working Group (GMAWG) of the Global Grid Forum (GGF) proposed an effective architecture to be scalable across wide-area networks and encompass a large number of heterogeneous resources. In this paper, we describe the design and implementation of Grid network monitoring system based on the GMA for practical network management. By this system, network operations center can form a management system flexibly and scalably for Grid network.

Recently, the Delay Tolerant Networks (DTN) have been utilized in various operational communication paradigms. This includes the communication scenarios that are subject to disruption and disconnection as well as the scenarios with high delay and frequent partitioning, i.e., Vehicular Ad hoc Networks (VANETs). Due to several characteristics match, a new research paradigm named as Vehicular Delay Tolerant Network (VDTN) is introduced. Through relays and store-carry-forward mechanisms, messages in VDTNs can be delivered to the destination without an end-to-end connection for delay-tolerant applications. However, the choice of routing algorithms in VDTNs is still under study. Numerous routing protocols have been proposed to meet requirements of many applications. In this paper, we therefore provide some detailed study of recently proposed routing schemes for VDTNs. We also perform comparative analysis on the basis of unique criterion such as forwarding metrics with their implementations. In addition, open challenges and future directions are provided to make room of interest for the research community.

Although the IEEE 802.15.4a network provides accuracy localization for sensor nodes, it still suffers from congestion and bottleneck problems since the data traffic tends to concentrate on a certain intermediate node due to the shortest path first criteria when it utilizes a greedy routing method. Furthermore, the limited network bandwidth and node mobility features exacerbate this problem in wireless sensor networks with tiny sensor platforms. In this paper, we propose a new dynamic load aware geographical routing protocol, named DLAG, which periodically monitors the channel condition of each node and forwards a packet to the neighboring node with the least traffic load by defining new buffer threshold values for controlling the congestion. In addition, the proposed protocol also introduces traffic adaptive backoff and frame retransmission tuning techniques to provide prioritized channel access for congested nodes. In order to verify the performance of the proposed protocol, we conduct simulation verification experiments and the results show that the proposed protocol provides better performance than the legacy geographical routing schemes in terms of packet delivery ratio, end-to-end delay, network lifetime, and so forth.

Energy efficiency in Underwater Acoustic Sensor Network (UASN) is a key challenge for extending network lifetime. Base on analysis of energy consumption for LEACH in underwater channel, we propose a novel clustering scheme for UASN based on grouping nodes to ensure that nodes balance energy load by considering residual energy of candidate nodes. We introduce a formation of small clusters (groups) within clusters named as Nested Clustering (NC). Our Energy Efficient Nested Clustering (EENC) scheme divides each cluster into small groups and nodes in each of those small groups switch their operation modes (idle and awake) to achieve energy efficiency. Through simulation results, it is observed that our proposed EENC scheme has better network lifetime and optimized data duplication as compared to the existing clustering schemes.

Multicasting is a desired function in both wired and wireless networks. Currently, multicasting‐based applications have pervasive presence and influence in our Internet. Wireless ATM aims to support different traffic types over a high speed wireless network. In particular, traditional approaches towards multicasting in wired networks cannot be directly applied to mobile ATM networks. This includes the mechanism proposed to handle mobility in wired networks. In this paper, we address the issues behind multicasting in wireless ATM networks and the underlying mechanisms to support handoffs of both unicast and multicast connections. Through simulation, we evaluated the performance of optimal core‐based tree (CBT), late‐joined CBT, optimal source‐based tree (SBT), and late‐joined SBT during changing multicast host membership conditions. In addition, we evaluated the impact of multicast receivers' migration on the total link cost of the resultant multicast tree. Simulation results revealed that source‐based trees incur more total link costs under both dynamic host membership and receivers' migration scenarios. However, it generates less control messages than the distributed CBT and SBT approaches.

Previously, we proposed the Directional Flooding-based Routing (DFR) protocol where the flooding area is updated according to link quality to provide reliable packet transmissions in loss-prone underwater wireless sensor networks (UWSNs). However, since the original DFR was designed to have static system parameters to consider a QoS requirement, it cannot meet the QoS requirement if the network condition changes dynamically which is inherent in UWSNs. We therefore propose two enhanced versions of DFR which control the number of forwarding nodes through an entire or partial path, based on feedback information from the sink.

Stability and lifetime of Wireless Sensor Networks (WSNs) mainly depend on energy of each node in the network. Hence, it is necessary for a WSN to be energy efferent. There are different methods to preserve energy in WSNs and clustering is one of those methods. Clustering techniques divide whole network into small blocks, each having a managing node, called cluster head (CH) and rest of the nodes within that block act as members. In this paper, we propose a distributed clustering scheme, called Modified VIKOR model based Clustering (MVC) protocol. This technique uses multiple criteria i.e. residual energy, node degree, distance to the base station and average distance between a node and its neighbors, to select a cluster head. Each node shares those parameters within its transmission range and decides which CH is suitable within that region. Modified VIKOR method is used to outrank the potential nodes as CHs by considering the conflicting criteria. The realistic multi-hoping communication model is used in both, inter-cluster and intra-cluster communication, instead of single hop as in previous schemes. Simulation results show that our purposed technique performs much better than those previous methods in terms of energy efficiency, network life time, less CH deformation and control overhead.

Cyber world and physical world were considered as two different entities in the past decade. However, researchers have found that these two entities are closely correlated with each other after integration of sensor/actuators in the cyber systems. Cyber systems became responsive to the physical world by enabling real time control emanating from conventional embedded systems, thus emerging a new research paradigm named Cyber Physical System (CPS). In this article, we investigate major challenges in the integration of cyber world with physical world and its applications. In addition, we propose an architecture which contains several modules supporting the CPS. We found that every module in our proposed architecture has its own significance and can be applied to various applications.

In Underwater Wireless Sensor Networks (UWSNs), many flooding-based routing protocols have been proposed because of their low routing overhead. However, they rely on the location information and current underwater localization techniques cannot provide the exact location information to all sensor node. Therefore, we need a new routing protocol which considers the characteristics of underwater localization in order to support packet transmissions from both localized nodes and unlocalized nodes to the sink. In this paper, we therefore propose an Underwater Hybrid Routing Protocol (UHRP) which has the hybrid features of flooding-based routing protocols and reactive ad-hoc routing protocols, based on our new routing metric. In addition, the expanded ring search technique is revised to be applied to reduce routing overhead in underwater environment.

This article presents an alternative scheme, called Xcast6+, which is an extension of explicit multicast (Xcast) for an efficient delivery of multicast datagrams over IPv6 networks. The mechanism incorporates MLDv2 and a new control plane into existing Xcast6 (Xcast for IPv6) and not only does it provide the transparency of traditional multicast schemes to sources and recipients, but it also enhances the routing efficiency in networks. Since intermediate routers do not have to maintain any multicast states, it results in a more efficient and scalable mechanism to deliver traditional multicast datagrams. Furthermore, the seamless integration of Xcast6+ in Mobile IPv6 can support multicast efficiently for mobile nodes over IPv6 networks by avoiding tunnel avalanches and tunnel convergence. Our simulation results show distinct performance improvements of our approach. This approach can reduce network resources in many "medium size groups" multicast, particularly as the number of recipients in a subnet increases (i.e., "subnet-dense groups").

The Intelligent Transportation System (ITS) can be considered the most representative example of Machine-to-Machine (M2M) applications in a standardization and commercial market. To support the applications, utilizing multiple network interfaces and providing appropriate network connectivity to them are the key issues in order to meet different network requirements of M2M applications on ITS devices. Moreover, different from applications which are controlled by a human operator, the ITS device with M2M application is required to decide the appropriate air interface and network for each application by itself according to the predefined policy and network status. In this paper, we therefore propose a novel multiple network interface management framework for ITS devices with M2M applications having their different requirements and constraints based on the CALM architecture. This can provide the M2M applications with extensible and flexible system environments based on the CALM architecture.

In this paper, we propose a distance-adaptive robust communication scheme which is based on existing IEEE 802.15.4 protocol without additional control frame overhead. The key mechanism of the proposed scheme provides the dynamic tuning of the BE value and frame retransmission opportunities according to the hop distance to the sink node. We also propose a new robust route maintenance scheme for avoiding and mitigating congested nodes during communication sessions.

In wireless sensor networks, clustering expedites many desirable functions such as load balancing, energy savings, and distributed key management. For secure clustering, it is very important to find compromised nodes and remove them during the initial cluster formation process. If some nodes are compromised and survive the censorship process, they can make some nodes have a different cluster view and can split a cluster into multiple clusters to deteriorate cluster quality as a whole. To resolve these problems, we propose a robust scheme against such attacks in this paper. First, our scheme generates large-sized clusters where any two nodes are at most two hops away from each other to raise the quality of clusters. Second, our scheme employs the verification of two-hop distant nodes to preserve the quality of the large-sized clusters and refrains from splitting the clusters. Last, our scheme prefers broadcast transmissions to save the energy of nodes. Security analysis proves that our scheme can identify compromised nodes and preserves the cluster membership agreement against the compromised nodes. In addition, simulation results prove that our scheme generates fewer clusters and is more secure and energy efficient than the scheme producing only small-sized clusters.

In underwater wireless sensor networks, asynchronous duty-cycle MAC protocols and gradient based routing protocols can be used in order to extend network lifetime and provide network scalability, respectively. However, in asynchronous duty-cycle MAC protocols, the advertisement message which is essential in gradient based routing protocols cannot be broadcasted efficiently. In this paper, we propose a unicast-based gradient routing protocol (UGRP) in order to get along with asynchronous duty-cycle MAC protocols. Especially, in UGRP, each node makes own gradients maintained by unicast transmissions.

Wireless sensor networks have been assumed to consist of a single sink and multiple sensor nodes which do not have mobility. In these networks, sensor nodes near the sink dissipate their energy so fast due to their many-to-one traffic pattern, and finally they die early. This uneven energy depletion phenomenon known as the hot spot problem becomes more serious as the number of sensor nodes (i.e., their scale) increases. Recently, multi-sink wireless sensor networks have been envisioned to solve the hot spot problem. Gradient routing protocols are known to be appropriate for the networks in that network traffic is evenly distributed to multiple sinks to prolong network lifetime and they are scalable. Each node maintains its gradient representing the direction toward a neighbor node to reach one of the sinks. In particular, existing protocols allow a sensor node to construct its gradient using the cumulative traffic load of a path for load balancing. However, they have a critical drawback that a sensor node cannot efficiently avoid using the path with the most overloaded node. Hence, this paper introduces a new Gradient routing protocol for LOad-BALancing (GLOBAL) with a new gradient model to maximize network lifetime. The proposed gradient model considers both of the cumulative path load and the traffic load of the most overloaded node over the path in calculating each node's gradient value. Therefore, packets are forwarded over the least-loaded path, which avoids the most overloaded node. In addition, it is known that assigning a unique address to each sensor node causes much communication overhead. Since the overhead increases as the network scales, routing protocols using an address to indicate the receiver in forwarding a packet are not scalable. Thus, GLOBAL also includes an addressing-free data forwarding strategy. Through ns-2 simulation, we verify that GLOBAL achieves better performance than the shortest path routing and load-aware gradient routing ones.

Federated network operations become more and more important and the central challenge for Future Internet testbeds around the world. This paper presents a framework that federates and operates the autonomous distributed networks (ADNs) in the perspective of virtual network operations and end-user oriented network management on end-to-end slices. In addition, we propose a virtual federated network (VFN) environment as a common federation interface between ADNs, associated with three key functionalities, that is, core network resource schema and representation, operational data exchanges, and federated network operations.

In Underwater Wireless Sensor Networks (UWSNs), developing an energy efficient routing protocol is a challenge due to the peculiar characteristics of UWSNs. In this paper, we therefore propose an energy-efficient routing protocol, called ERP2R (Energy-efficient Routing Protocol based on Physical distance and Residual energy). ERP2R is based on a novel idea of utilizing the physical distances of the sensor nodes towards the sink node. ERP2R also takes into account the residual energy of the sensor nodes in order to extend the network life-time. Sensor nodes make a local decision of packet forwarding according to their physical distance and the residual energy information. Using the ns-2 simulator, we proved that the ERP2R protocol performs better than a representative protocol (i.e. DBR) in terms of energy efficiency, end-to-end delay and network lifetime.

Underwater Wireless Sensor Networks (UWSNs) have peculiar characteristics such as high propagation delay, limited bandwidth and high error rates. Therefore, communication protocols for UWSNs are highly required to cope with them. Specifically, the design of an efficient routing protocol for UWSNs is one of the most important challenges. The routing protocols can take advantage of the localization of sensor nodes. However, the localization itself is a crucial issue in UWSNs, which remains to be solved yet. Hence, the design of a non-localization based routing protocol is a preferable alternative. In this paper, we therefore propose a non-localization based routing protocol named MRP (Multi-layered Routing Protocol) for UWSNs. In MRP, the concept of super nodes is employed. The super nodes are the nodes having high capacity such as high energy and transmission power. Our proposed protocol, MRP, consists of two phases: layering and data forwarding phases. During the layering phase, multiple layers are formed by the super nodes, whereas, in the data forwarding phase, data packets are forwarded based on these layers. Based on the simulations using NS2, we observe that our proposed routing protocol, MRP, contributes to the performance improvements.

Vehicular ad hoc network (VANET) is a new type of network that has promised countless applications including safety, comfort, infotainment, etc. The high mobility of vehicles in VANET makes routing protocol design a challenging task. Geographic routing is considered a suitable approach for VANET. The proposed geographic routing protocols for VANET, primarily, differ in the forwarding strategy. In this article we classify state-of-the-art unicast geographic routing protocols on the basis of forwarding strategies. We describe each protocol in terms of some qualitative metric. Finally the selected unicast geographic routing protocols are analyzed through a comparative discussion.

Recently, multi-sink wireless sensor networks (WSNs) are envisioned to solve the hot spot problem caused by traditional single-sink WSNs. Routing protocols should be able to distribute network traffic evenly to multiple sinks to prolong network lifetime and they should be scalable. Gradient-based routing protocols are known to be suitable for the networks, where each node maintains its gradient representing the direction toward a neighbor node to reach a sink. In particular, existing protocols allow a sensor node to construct its gradient using the cumulative traffic load of a path for load-balancing. However, they have a critical drawback that a sensor node cannot efficiently avoid using the path with the most overloaded node. Hence, this paper introduces a new gradient-based routing protocol for load-balancing (GLOBAL) with a new gradient model to maximize network lifetime. In GLOBAL, the least-loaded path which also avoids the most overloaded sensor node is selected for forwarding. Through ns-2 simulation, we verify that GLOBAL achieves better performance than the shortest path routing protocol and load-aware gradient-based routing one.

Distributed Virtual Network Operations Center (dvNOC) presents virtualized network management framework on hybrid research networks for both network operators and end-users (e.g. researchers) to monitor and manage their own virtual networks. Another purpose of dvNOC is to meet the network demands of advanced applications on hybrid research networks, e.g. very high bandwidth, no datagram loss, almost zero jitter with strict traffic isolation. Based on hierarchical architecture consisting of dNOC (distributed NOC) and vNOC (virtual NOC), users can acquire three functionalities, multi-domain network awareness, efficient NOC-to-NOC cooperation, and user-oriented virtual network management, which are essential elements to achieve automated and virtual network management based on users, over multi-national and inter-domain hybrid research networks.

In delay tolerant networks (DTNs) with frequent network partitioning, routing packets is a challenge, because the successful establishment of an end-to-end path between source and destination nodes is not guaranteed. Typical routing protocols for DTNs depend on data replications over multiple paths for reliable data delivery. Since they invoke a lot of replicated packets, our previous work introduced a Vector Routing protocol utilizing the vector of node movement in order to reduce such replications. In this paper, we extend the previous work and propose a more efficient Vector Routing protocol to exploit some features of history-based routing protocols where packets are forwarded to nodes with higher probability to meet their destination nodes. Unlike the existing protocols where the number of nodal encounters is used to calculate the probability of forwarding, our proposed protocol allows a node to maintain the vector information of other nodes that it has met and share this information with other nodes. Using the history information, a node predicts the location area of each packet's destination node in order to perform more accurate forwarding. The ns-2 simulations using Random Waypoint and Manhattan Mobility models verify that our protocol achieves better perfor- mance in terms of less amount of traffic incurred without loss of packet delivery ratio.

Nowadays, with the exponential growth of Internet, the network complexity has been increased because of various network equipment and protocols. It makes network configuration management so hard. In order to settle out these problems, we propose the Topology Discovery Algorithm and the Self-Configurable Diagnosis Algorithm on Isolation network. We defined an Isolation Network as the unit of self-configurable network. The novelty of the former algorithm is the simplicity and decentralization of itself. And the latter algorithm diagnoses simultaneously node faults and links faults and doesn’t need to use another network management protocols such as SNMP and TL1 to diagnose network configuration. Essentially this is divide-and-conquer strategy for larger and complex network. Through simulations we verified the effect on the network by traffic, which is generated by Topology Discover Algorithm. These algorithms can be directly adapted to IP routing network or lambda exchange network.

Recently, much research work has paid attention to delay tolerant networks (DTNs), which are networks with a frequent occurrences of network partitioning. Since the successful establishment of an end-to-end path between source and destination nodes is not guaranteed in these networks, routing is a challenging issue. In typical routing protocols for DTNs such as epidemic routing, they depend on data replication techniques over multiple paths for reliable data delivery. However, they invoke a large number of duplicated packets in the network. This paper therefore proposes an efficient routing (called vector routing) by utilizing the vector of node movements. In vector routing, the direction and velocity of nodes are calculated from the location information of nodes, and then nodes efficiently decide which nodes should take replicated packets as well as the number of packets to replicate. Using ns-2 simulation with two different mobility models, namely random waypoint and manhattan mobility models, we verify that vector routing performs better than epidemic routing in terms of less amount of traffic incurred without loss of packet delivery ratio.

In wireless ad hoc networks, utilizing multiple interfaces as well as multiple channels at MAC layer is known as one of key techniques to improve network capacity. Since the existing multi-channel MAC protocols like MMAC and SSCH assume that a single interface is used, a protocol such as HMCP was proposed in order to make the best use of multiple interfaces. However, a fixed specific channel is assigned to an interface in HMCP. In addition, HMCP requires one interface to accomplish an exclusive purpose of either transmission or reception. To address these shortcomings, we propose a multi-channel multi-interface MAC (MM-MAC) protocol, which dynamically assigns channels to each interface of the nodes and reserves the transmission times of nodes on these selected channels. The scheduled transmission of packets also enables our MM-MAC protocol to reduce the number of channel collisions and the overhead of exchanging control messages. Through extensive study using the ns-2 simulator, we observe that our MM-MAC protocol performs better than the existing protocols such as MMAC and HMCP.

In delay tolerant networks (DTNs) such as wireless ad hoc networks, frequent and long-duration partitioning of networks causes continuous end-to-end connectivity to be non-guaranteed. Hence, in order to enable legacy applications to run in this DTN environment,the communication protocol stack should be modified to transparently provide applications with the service connectivity. In this paper, therefore, we propose a DTN service architecture and its corresponding protocols, where cross-layering techniques between transport and network layers are exploited. Using ns-2 simulator, we verify that our approach enables end-to-end applications to resume their communication after service disruption. It also has low routing overhead, as compared to the existing approach without this DTN service functionality.

In a mobile ad-hoc network (MANET), in order to route a packet between any nodes, nodes should have their unique IP address in the network. In our previous work, we introduced and compared three IP assignment mechanisms, namely RADA, LiA, and LiACR. In RADA, a randomly-selected IP address in a specified address space is assigned to a joining node, which results in poor utilization of the address space with a great deal of address conflict. LiA allows a joining node to be assigned to the current maximum address + 1, that is, linearly from the address space. Although LiA utilizes the address space better, it takes a long time to complete address assignments due to address conflict in case that several joining nodes require the same IP address. LiACR allows simultaneously joining nodes to have their IP addresses according to the node ID-based order. However, it relies on reliable exchange of control messages in the wireless network. Since broadcasting is inherently unreliable, we therefore propose an enhanced version of the LiACR protocol, called E-LiACR, which copes with the unreliable broadcasting through the help of neighbor nodes. Through ns-2 simulations, we show that E-LiACR performs better than LiACR in terms of IP address allocation time, number of address conflicts, and control message overhead.

In a mobile ad-hoc network (MANET), in order to route a packet between any two nodes, nodes should have their own unique IP address in the network. We introduce an address auto-configuration mechanism that utilizes a clustering technique, called CBA (Cluster-Based Address auto-configuration). Until now, most of existing clustering techniques have been applied to routing protocols. This paper, however, is the first trial that allows address auto-configuration to take advantage of the clustering technique. We propose a novel 2-level hierarchy cluster construction mechanism and present how to utilize clusters for the purpose of efficient address auto-configuration. We evaluate our proposed CBA through NS-2 simulations and prove that CBA is more suitable for a network with a large number of nodes which are joining/leaving at the same time.

IP auto-configuration in mobile ad hoc networks has attracted much attention. Efficient DAD (duplicate address detection) techniques should be devised to provide each node with its unique address in the network. Generally, DAD schemes can be categorized into two classes: (a) active DAD and (b) passive DAD. In this paper, we focus on passive DAD schemes over on-demand ad-hoc routing protocols such as AODV and DYMO. In order to improve the accuracy of detecting address conflicts, we propose several schemes using additional information including sequence, location, or neighbor information

A MANET (mobile ad hoc network) requires an efficient network-wide broadcasting service in route discovery as well as in many applications. Recently, many broadcasting protocols have been proposed to avoid the well-known broadcast-storm problem, or to provide reliability over wireless broadcast media. However, since it is assumed that all nodes in the network have the same radio ranges (i.e. homogeneous radio ranges), the protocols do not work in a realistic environment where all nodes have different fixed radio ranges or they use dynamic radio ranges intentionally to save their energy in the network (i.e. heterogeneous radio ranges). We therefore propose an efficient stateless broadcasting technique to support the heterogeneous radio ranges. An additional area covered through a node's rebroadcasting is calculated by considering different radio ranges of nodes. Then, nodes with larger coverage area will rebroadcast earlier than other nodes with smaller area. When determining rebroadcasting schedule, the DFD (dynamic forwarding delay) concept introduced in DDB (dynamic delayed broadcasting) is exploited in our protocol. Extensive simulation using ns-2 proves that our scheme is more suitable for a realistic environment.

IETF MANET (mobile ad hoc network) working group has standardized AODV (ad hoc on-demand distance vector) and OLSR (optimized link state routing) as its reactive and proactive routing protocols, respectively. In addition, from the transport layer's perspective, TCP (transmission control protocol) is still needed for MANET since it is widely used in the current Internet and suitable for smooth integration with the fixed Internet. Particularly, TCP has its variants, namely TCP-Reno and TCP-Vegas. However, there has been no research work on extensive performance comparison of TCP-Reno and TCP-Vegas over AODV and OLSR. Through extensive simulations, we found that the selected routing protocols is more important than the selected TCP variant, because the performance difference between TCP-Reno and TCP-Vegas over any selected routing protocol is not relevant.

Multiple paths have been used to provide loadbalancing of traffic and resilience to node failures in mobile ad-hoc networks or sensor networks. In addition, the energy expenditure can be distributed among nodes over the multiple paths. However, most existing multi-path routing protocols require their complex procedures such as local repair or periodic reconstruction of the multiple paths, during which much loss of packet is even experienced. In this paper, we therefore propose two versions of an Energy efficient Data Gathering technique using Multiple paths (EDGM), which are more suitable for highly populated wireless sensor networks in terms of having more simple and resilient features than other existing techniques. One of them is to make use of the multiple shortest paths strictly. The other is to use a neighbor node’s path towards the sink node at the expense of using much longer paths to provide more resilience to node failures. By simulation using ns-2simulator, we prove that EDGM versions achieve two goals satisfactorily: energy-saving and resilience to node failure.

As an example of implementing the pervasive computing, we developed an application framework to deploy an easy, spontaneous, and infrastructureless network. We selected the Bluetooth technology with the peer-to-peer (P2P) concept to develop an experimental application which enables peers to exchange their resources. Overall network architecture and the prototype application are presented. We selected a small test-bed and simulation to evaluate the overall performance and system behaviour. We measured and present our findings in term of the duration of inquiry procedure and the throughput, according to various experimental parameters such as physical distance between nodes and their speeds.

Multiple paths have been used to provide load- balancing of traffic and resilience to node failures in mobile ad-hoc networks or sensor networks. In addition, the energy expenditure can be distributed among nodes over the multiple paths. However, most existing multi-path routing protocols re- quire their complex procedures such as local repair or periodic reconstruction of the multiple paths, during which much loss of packet is even experienced. In this paper, we therefore propose an energy-efficient data gathering technique using multiple paths, which is more suitable for highly populated wireless sensor net- works in terms of having more simple and resilient features than other existing techniques. By simulation using ns-2 simulator, we prove that it achieves two goals satisfactorily: energy-saving and resilience to node failure.

Overlay multicast has been proposed as an alternative scheme to provide one-to-many or many-to-many data delivery on Internet. However, since data delivery is entirely dependent on replications on each group member, if one member node fails, none of its children receives data. Furthermore, the higher the failed node's level is, the more the dead nodes occur. In this paper, we give a detailed framework for resilience in overlay multicast. Unlike previous efforts in providing reliable data delivery, our scheme constructs reliable overlay data delivery tree (DDT) and adaptively reconstructs it based on the number of missed packets while guaranteeing end-to-end delay bound. Through practical simulation results, we analyzed packet delivery ratio, control overhead, end-to-end delay and number of replicated packets.

In this paper, we give a framework to reduce delivery failure influence in overlay multicast. Unlike previous efforts based on duplicated forwarding, our scheme builds another type of overlay data delivery tree (DDT), which is adaptively reconstructed based on the number of measured packet delivery ratio while guaranteeing end-to-end delay bound. Through practical simulation results, we analyzed packet delivery ratio, control overhead, end-to-end delay and number of replicated packets.