This paper proposes a heterogeneous wireless network with handover in the application layer. The proposed network requires no upgrade of wireless infrastructure and mobile terminals to convert the present homogeneous networks to the proposed heterogeneous network. Only installing application programs on the content server side and the mobile terminal side is required. The performance of the proposed network has been evaluated in a field trial using a mobile broadband wireless access (MBWA) air interface with wide coverage and a wireless local area network (WLAN) air interface with high throughput. The field trial results show that the maximum value of the handover outage time is only 170 ms. The proposed heterogeneous wireless network is promising since both high throughput and wide coverage area are attained by a combination of the proposed handover scheme with the present homogeneous wireless networks.

In cognitive radio networks, secondary users exchange control information to utilize the available channels efficiently, to maintain connectivity, to negotiate for data communication such as sender-receiver handshakes, for neighbor discovery etc. This task is not trivial in cognitive radio networks due to the dynamic nature of network environment. Generally, this problem is tackled by using two famous approaches. The first one is the use of common control channel (CCC) and the second one is using channel hopping (a.k.a sequence-based protocols). The use of CCC simplifies the processes of MAC protocols. However, it may not be feasible in cognitive radio networks as the available channels, including control channel, are dynamically changing according to primary user activities. Channel hopping approaches can tolerate the failure of network due to primary user activities. But it causes significant amount of channel access delay which is known as time to rendezvous (TTR). In this paper, we propose a hybrid protocol of these two mechanisms. This hybrid protocol can maintain connectivity and it can guarantee the secondary users to be able to exchange necessary control information in dynamic environment. In our hybrid protocol, we use multiple control channels. If some control channels are unavailable in case of primary user appearances, secondary users still can communicate on different control channels, so it can be more tolerable primary user activities than normal CCC approaches. Channel hopping is performed only for control channels, so it provides relatively small amount of channel access delay.

To provide scalability against group size, Global Location Search based Hierarchical Geographic Multicast Protocols (GLS-HGMPs) have recently been proposed for wireless sensor networks. To reduce the communication overhead imposed by the global location search and prevent the multicast data detour imposed by the hierarchical geographic multicasting in GLS-HGMPs, this letter proposes Local Location Search based Progressive Geographic Multicast Protocol (LLS-PGMP). Simulation results show that LLS-PGMP is superior to GLS-HGMPs.

An adaptive rate controller (ARC) based on an adaptive neural fuzzy inference system (ANFIS) is designed to autonomously adjust the data rate of a mobile heterogeneous network to adapt to the changing traffic load and the user speed for multimedia call services. The effect of user speed on the handoff rate is considered. Through simulations, it has been demonstrated that the ANFIS-ARC is able to maintain new call blocking probability and handoff failure probability of the mobile heterogeneous network below a prescribed low level over different user speeds and new call origination rates while optimizing the average throughput. It has also been shown that the mobile cognitive wireless network with the proposed CS-ANFIS-ARC protocol can support more traffic load than neural fuzzy call-admission and rate controller (NFCRC) protocol.

Network-on-Chips (NoCs) have been proposed as a solution for addressing the global communication challenges in System-on-Chip (SoC) architectures that are implemented in nanoscale technologies. For the use of NoCs to be feasible in today's industrial designs, a custom-tailored, power- efficient NoC topology that satisfies the application characteristics is required. In this work, we present a design methodology that automates the synthesis of such application-specific NoC topologies. We present a method which integrates partitioning into floorplanning phase to explore optimal clustering of cores during floorplanning with minimized link and switch power consumption. Based on the size of applications, we also present an Integer Linear Programming and a heuristic method to place switches and network interfaces on the floorplan. Then, a power and timing aware path allocation algorithm is carried out to determine the connectivity across different switches. We perform experiments on several SoC benchmarks and present a comparison with the latest work. For small applications, the NoC topologies synthesized by our method show large improvements in power consumption (27.54%), hop-count (4%) and running time (66%) on average. And for large applications, the synthesized topologies result in large power (31.77%), hop-count (29%) and running time (94.18%) on average.

In this paper, we propose a novel scheme to optimize the allocation of continuous queries in a sensor network with multiple sinks. The existing scheme compares the coverage areas of given queries and estimates the amount of sharing among them. It tries to allocate queries to the optimal sink that maximizes the amount of sharing and reduces the communication costs among sensor nodes and sinks. However, it inefficiently allocates continuous queries. The amount of sharing among continuous queries depends not only on their coverage area but also on their time-parameters like time-duration and time-interval. We define a new cost estimator with time-parameters for continuous queries and optimize their allocation in the sensor network. Simulation results show that our scheme performs the allocation of continuous queries efficiently and reduces the communication cost.

It is important to optimize aggregation schemes for heterogeneous wireless networks for maximizing communication throughput utilizing any available radio access networks. In the heterogeneous networks, differences of the quality of service (QoS), such as throughput, delay and packet loss rate, of the networks makes difficult to maximize the aggregation throughput. In this paper, we firstly analyze influences of such differences in QoS to the aggregation throughput, and show that it is possible to improve the throughput by adjusting the parameters of an aggregation system. Since manual parameter optimization is difficult and takes much time, we propose an autonomous parameter tuning scheme using a machine learning algorithm for the heterogeneous wireless network aggregation. We implement the proposed scheme on a heterogeneous cognitive radio network system. The results on our experimental network with network emulators show that the proposed scheme can improve the aggregation throughput better than the conventional schemes. We also evaluate the performance using public wireless network services, such as HSDPA, WiMAX and W-CDMA, and verify that the proposed scheme can improve the aggregation throughput by iterating the learning cycle even for the public wireless networks. Our experimental results show that the proposed scheme achieves twice better aggregation throughput than the conventional schemes.

Link prediction in social networks, such as friendship networks and coauthorship networks, has recently attracted a great deal of attention. There have been numerous attempts to address the problem of link prediction through diverse approaches. In the present paper, we focus on the temporal behavior of the link strength, particularly the relationship between the time stamps of interactions or links and the temporal behavior of link strength and how link strength affects future link evolution. Most previous studies have not sufficiently discussed either the impact of time stamps of the interactions or time stamps of the links on link evolution. The gap between the current time and the time stamps of the interactions or links is also important to link evolution. In the present paper, we introduce a new time-aware feature, referred to as time score, that captures the important aspects of time stamps of interactions and the temporality of the link strengths. We also analyze the effectiveness of time score with different parameter settings for different network data sets. The results of the analysis revealed that the time score was sensitive to different networks and different time measures. We applied time score to two social network data sets, namely, Facebook friendship network data set and a coauthorship network data set. The results revealed a significant improvement in predicting future links.

Recently, the GMPLS controlled WSON has emerged as a promising optical transport network. In order to guarantee the optical signal transmission feature without deformation, the optoelectronic 3R regenerators still need to be sparsely placed in the network, termed as translucent networks. The growing size and complexity of the translucent network requires a transition of control plane to move from the traditional centralized model to a fully distributed architecture in the future. However, centrally designed routing, wavelength assignment, and 3R regenerator allocation approaches become unfeasible under the distributed paradigm due to the outdated and inconsistent network state information. A common solution is to accelerate the update frequency of network state, but the fundamental problem remains that the inaccurate state information is still inevitable. Furthermore, it adds a significant increase to the control traffic volume which adversely degrades the performance and scalability of the network control system. In order to mitigate the impact of having inaccurate state information on network performance in the distributed systems, a novel RWA approach is proposed in this paper, termed as routing and distributed wavelength assignment with top ranked probing wavelength set computation. In our proposal, the wavelength assignment is performed by signalling process with a set of carefully preselected probing wavelengths. This set is dynamically computed based on the resource utilization each time the network state is refreshed. The PCE module is adopted in WSON control plane to be responsible for the computation of RWA and 3R allocation. The performance of the proposed approach is studied by extensive simulations. The experiment results reveal that by employing the proposed scheme, without loss on the blocking performance the inaccuracy of the wavelength availability information can be well tolerated, and the set-up delay in lightpath provisioning can be kept at a low level.

This letter investigates the problem of distributed channel selection in cognitive radio ad hoc networks (CRAHNs) with heterogeneous spectrum opportunities. Firstly, we formulate this problem as a local congestion game, which is proved to be an exact potential game. Then, we propose a spatial best response dynamic (SBRD) to rapidly achieve Nash equilibrium via local information exchange. Moreover, the potential function of the game reflects the network collision level and can be used to achieve higher throughput.

We propose a Junction-Based Traffic Aware Routing (JTAR) protocol for Vehicular Ad Hoc Networks (VANETs) in sparse urban environments. A traffic aware optimum junction selection solution is adopted in packet-forwarding, and a metric named critical-segment is defined in recovery strategy. Simulation results show that JTAR can efficiently increase the packet delivery ratio and reduce the delivery delay.

This paper considers the power allocation (PA) problem for three-node decode-and-forward (DF) relay communication systems, where the aggregate transmit power constraint is imposed on the source and the relay and the optimization target is to maximize the system's instantaneous information rate. Since the relay is equipped with multiple antennas, the receiver and transmitter beamforming strategies are generally adopted. In this paper, we start by proposing a closed-form solution for the frequency-flat (FF) fading environment, then give a bisection algorithm with low complexity to obtain an optimal solution for the frequency-selective (FS) fading scenario. Finally, simulations validate the proposed methods.

In this letter, we consider a cognitive radio based multihop network under the spectrum sharing underlay paradigm. By taking into account the interference constraints, we present an exact closed-form expression for outage probability, which is valid for the whole signal-to-noise ratio regime. In addition, some numerical examples of interest that study the effect of the number of hops and/or the interferer threshold on primary users are illustrated and discussed. Numerical results show that multihop systems still offer a considerable gain as compared to direct transmission under the same limit of interference.

In this letter, we introduce two different resource allocation and Tx power management schemes, called resource control and fixed power (RCFP) and fixed resource and power control (FRPC), in an LTE-Advanced femtocell network. We analyze and compare the two schemes in terms of the system throughput for downlink and energy consumption of home evolved NodeB (HeNB) Tx power according to the number of HeNBs and home user equipment (HUE)'s user traffic density (C). The simulation results show that the FRPC scheme has better performance in terms of system throughput for macro user equipments (MUEs) and energy consumption in low C.

In next-generation networks, ultra-high speed transfer capability will become necessary to support a variety of advanced multimedia services. The Optical Wavelength Division Multiplexing (WDM) network is seen as one of promising networks. To deal with various multimedia services, the network should support not only unicast transmission but also multicast transmission. However, IP multicast has several problems, for example, all routers must have multicast functions. IP multicast needs routers with high overheads and excessive energy consumption. Hence, optical multicasting in optical WDM networks is a promising solution for future internet services. A tree-shared multicasting concept has been proposed to support multicast transmissions in optical WDM networks. This method assembles multiple multicast traffic streams into one burst and the burst is delivered using a shared-tree. However, this method can not be applied to dynamic multicasting. This paper proposes a novel WDM multicast design method for dynamic traffic demand using multiple shared-trees, which includes shared-tree generation/selection and wavelength assignment, for the purpose of simplifying the routing process and receiving multicast traffic efficiently. We evaluate its performance from the viewpoints of the burst loss probability and the number of redundant and useless transfers whose data is discarded at the egress edge nodes.

In this paper, a decentralized concurrent transmission strategy in shared channel in Ad Hoc networks is proposed based on game theory. Firstly, a static concurrent transmissions game is used to determine the candidates for transmitting by channel quality threshold and to maximize the overall throughput with consideration of channel quality variation. To achieve NES (Nash Equilibrium Solution), the selfish behaviors of node to attempt to improve the channel gain unilaterally are evaluated. Therefore, this game allows each node to be distributed and to decide whether to transmit concurrently with others or not depending on NES. Secondly, as there are always some nodes with lower channel gain than NES, which are defined as hunger nodes in this paper, a hunger suppression scheme is proposed by adjusting the price function with interferences reservation and forward relay, to fairly give hunger nodes transmission opportunities. Finally, inspired by stock trading, a dynamic concurrent transmission threshold determination scheme is implemented to make the static game practical. Numerical results show that the proposed scheme is feasible to increase concurrent transmission opportunities for active nodes, and at the same time, the number of hunger nodes is greatly reduced with the least increase of threshold by interferences reservation. Also, the good performance on network goodput of the proposed model can be seen from the results.

In this paper, we suggest a new technology called Content Anycasting, and we show our design and evaluation of it. Content Anycasting shows how to utilize the capabilities of one of the candidate future Internet technologies that is the Flow-based network as in OpenFlow to giving new opportunities to the future internet that are currently not available. Content Anycasting aims to provide more flexible and dynamic redirection of contents. This would be very useful in extending the content server's capacity by enabling it to serve more clients, and in improving the response of the P2P networks by reducing the time of joining P2P networks. This method relies on three important ideas which are; the content based networking, decision making by the network in a similar manner to anycast, and the participation of user clients in providing the service. This is done through the use of the flow-based actions in flow-based network and having some modifications to the content server and client.

This paper proposes a low latency MAC protocol that can be used in sensor networks. To extend the lifetime of sensor nodes, the conventional solution is to synchronize active/sleep periods of all sensor nodes. However, due to these synchronized sensor nodes, packets in the intermediate nodes must wait until the next node wakes up before it can forward a packet. This induces a large delay in sensor nodes. To solve this latency problem, a clustered sensor network which uses two types of sensor nodes and layered architecture is considered. Clustered heads in each cluster are synchronized with different timing offsets to reduce the sleep delay. Using this concept, the latency problem can be solved and more efficient power usage can be obtained.

Vehicular ad hoc networks have been attracting the interest of both academic and industrial communities on account of their potential role in Intelligent Transportation Systems (ITS). However, due to vehicle movement and fading in wireless communications, providing a reliable and efficient multi-hop broadcast service in vehicular ad hoc networks is still an open research topic. In this paper, we propose FUZZBR (FUZZy BRoadcast), a fuzzy logic based multi-hop broadcast protocol for information dissemination in vehicular ad hoc networks. FUZZBR has low message overhead since it uses only a subset of neighbor nodes to relay data messages. In the relay node selection, FUZZBR jointly considers multiple metrics of inter-vehicle distance, node mobility and signal strength by employing the fuzzy logic. FUZZBR also uses a lightweight retransmission mechanism to retransmit a packet when a relay fails. We use computer simulations to evaluate the performance of FUZZBR.

The IEEE 802.15.4 protocol is considered a promising technology for low-cost low-power wireless personal area networks. Researchers have discussed the feasibility of voice communications over IEEE 802.15.4 networks. To this end, the personal area network (PAN) coordinator allocates guaranteed time slots (GTSs) for voice communications in the beacon-enabled mode of IEEE 802.15.4. Although IEEE 802.15.4 is capable of supporting voice communications by GTS allocation, it is impossible to accommodate voice transmission beyond two hops due to the excessive transmission delay. In this paper, we propose a GTS allocation scheme for bidirectional voice traffic in IEEE 802.15.4 multihop networks. The goal of our proposed scheme is to achieve low end-to-end delay and packet drop ratio without a complex allocation algorithm. Thus, the proposed scheme allocates GTSs to devices for successful completion of voice transmission in a superframe duration. The proposed scheme also considers transceiver switching delay. This is relatively large compared to a time slot due to the low-cost and low-gain antenna designs. We analyze and validate the proposed scheme in terms of average end-to-end delay and packet drop ratio. Our scheme has lower end-to-end delay and packet drop ratio than the basic IEEE 802.15.4 GTS allocation scheme.