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Small cell aims at improving the cell coverage and capacity of macrocell. Network operators investigate cell planning for improving system performance and for satisfying user requirements with minimal construction cost and least unserved users. Most of the existing literature merely considered a single objective function or investigated cell planning for small-scale and homogeneous networks. This study aims to optimise multiple objective functions of a large-scale and heterogeneous wireless network with multiple macrocells and multiple small cells. The authors formulate the multi-objective optimisation problem of cell planning for heterogeneous cellular networks. The three objects include construction cost, number of unserved users and network capacity. Then they propose the large-scale cell planning genetic algorithm (LSCPGA) to find a planning result with the lowest fitness value. Simulation results show that LSCPGA economises 9-20% construction cost, eliminates the number of unserved users from 4 to 10% and enhances 2-15% in network capacity compared to other planning algorithms.

As an important component of the intelligent transportation system, internet-of-vehicles technology has attracted considerable attention. The dissemination of event-driven emergency messages with high reliability and low delay is vital to ensure traffic safety and improve traffic efficiency in urban environment. In this study, the authors propose a reliable emergency message dissemination protocol taking into account the urban road characteristics and scalability requirements, which consists of a layout-aware ready-to-broadcast-emergency-message and clear-to-broadcast-emergency-message handshake mechanism and a redundant relay node adaptation mechanism. Finally, the simulation results confirm the feasibility and effectiveness of the proposed scheme.

Software defined networking (SDN) paradigm currently does not integrate with any debugging or diagnosing mechanism. Services through Internet connection may not work properly due to network problems, such as loop and black hole problems. The study introduces sPing, a user-centred debugging mechanism for users debugging and troubleshooting network problems in SDN. The sPing diagnoses problems in data plane by collecting and recording specific packets based on programmable capability. It not only detects network loop and black hole but also discovers the hidden information of data link layer. The discovery of layer 2 information is unachievable to existing SDN-based debuggers. The authors experiment the sPing on three different brands of SDN switches for verifying its proof of concept, and simulate it in the Mininet emulator for evaluating its performance. Results showed that the proposed sPing mechanism assists SDN users in debugging network problems and in maintaining network functionalities.

Underwater wireless sensor networks (UWSNs) have recently received a significant amount of attention. Since they have delay/disruption-tolerant networks (DTNs) characteristics, the design of any UWSN scheme must take DTN influences into account, especially in routing protocols. Many researchers have proposed various DTN routing techniques for different types of DTN routing schemes in UWSNs. The authors survey state-of-the-art DTN routing protocols, and use the definition of DTN to classify these proposals into scheduled contact, opportunistic contact and predicted contact. Furthermore, the authors analyse the detailed information in order to draw up a comparison table and also expect to inspire more research into this topic in the future.

Sensor-cloud computing is envisioned to be one of the key enabling technologies for remote health monitoring. Integration of sensed data into cloud applications in sensor-cloud will help in real-time monitoring of patients over geographically distributed locations. In this study, the authors study the optimal gateway selection problem in sensor-cloud framework for real-time patient monitoring system by using a zero-sum game model. In the proposed model, a gateway acts as the first player, and chooses the strategy based on the available bandwidth, whereas a user request acts as the second player, and follows the strategy chosen by the first player. The authors evaluate the execution time for selecting the optimal gateway through which the sensed data will be fetched to the cloud platform. In addition, the authors show how user requests are serviced by the gateways to access data from cloud platform optimally. The authors also show that by using the proposed approach, the execution time decreases, thereby helping in forming a reliable, efficient and real-time architecture for health monitoring.

In 1999, the Federal Communications Commission of the US granted 75 MHz bandwidth at 5.850-5.925 GHz frequency band for intelligent transportation system wireless communication between vehicles and roadside infrastructures to improve automotive user driving safety and comfort. For fast IPv6 global-link address auto-configuration in vehicular ad-hoc network (VANET), IEEE 1609.3 defines a frame Wireless Access effort in the Vehicular Environment (WAVE) service acknowledge to replace router advertisement (RA); however, it violates the Transmission Control Protocol (TCP)/Internet Protocol (IP)-layered design. Hence the authors propose two cross-layer designs called router RA proxy and host RA proxy for WAVE systems to achieve quick IPv6 address auto-configuration, and both the designs are simulated in OPNET.

In this study, we propose a novel evolutionary computing method that is called quantum-inspired electromagnetism-like mechanism (QEM). QEM is based on the electromagnetism theory and uses the characteristic of quantum computation. We compare with quantum-inspired evolutionary algorithms (QIEA) and the other traditional heuristic algorithms to solve 0/1 knapsack problem. Meanwhile, we can also find the shortest tour length of 16 cities travelling salesman problem (TSP). The experimental results show that the QEM can rapidly and efficiently obtain the optimal solution of combinatorial optimisation problems. To conclude, QEM is an efficient solution for optimal control and adaptive control in stochastic/hybrid systems.

Among various network topologies, tree-like networks, also known as hierarchical networks are proposed to decrease the overhead of the routing table especially for the situation involving many network nodes. Usually, the routing table size and the routing complexity are the two crucial concerns in designing a large network. Although there have been various algorithms to optimise the routing strategies for the hierarchical networks, hardly exists any work in studying and evaluating the routing table size and the routing complexity rigorously in the statistical sense. In this study, the authors generalise a new mathematical framework by applying the point process in random geometry. The new framework proposed by the authors leads to the explicit statistical measures of the routing table size and the routing complexity, which can be specified as the functions of the hierarchical network parameters including the number of the hierarchical levels and the cluster population for each hierarchical level. After the relationship between the network topology and these two network performance measures (routing complexity and routing table size) is established, a cluster-population optimisation method for hierarchical networks is presented. The simulation results are also provided to demonstrate the advantage of a hierarchical network over the associated conventional network without hierarchy.

International audience; As Internet Protocol (IP) multicast allows the efficient use of network bandwidth for multipoint communication, it is expected to be an essential communication type for delivering multimedia services to mobile nodes (MNs). In this study, the authors address an issue of consumer multicast traffic support in a Proxy Mobile IPv6 (PMIPv6) environment wherein network-based mobility management is deployed for MNs. The recently standardised PMIPv6 multicast listener support provides options for deploying multicast listener functions in a PMIPv6 domain, whereas it does not address specific optimisations and efficiency improvements of multicast routing. The authors first review the PMIPv6 multicast listener support and point out the limitations of the current approach. Then, propose an improved multicast handover procedure that optimises multicastgroup management by utilising the context of consumer's MN running multicast applications. The authors develop analytical models to evaluate the proposed multicast handover procedure compared with the base one. From the conducted analysis, it is demonstrated that the proposed multicast handover procedure minimises the service interruption time and prevents the multicast packet loss during handovers. Furthermore, in terms of signalling cost consumption, the proposed multicast handover procedure operates on an equal basis with the base one.

Over the last decade, mobile agent (MA) systems for surveillance applications in wireless sensor networks (WSNs) has gained much attention. However, a conventional MA-based WSN may have the issues of energy efficiency and task duration as the scale of the network is increased. In order to overcome the drawbacks of using a single MA, dispatching two or more MAs for data collection simultaneously is a promising alternative in a WSN. The authors first discuss the itinerary planning issues for multiple MAs: deciding the number of MAs to be dispatched, grouping of source nodes for each MA, routing of each MA for its assigned source nodes. The authors then survey the existing algorithms for these issues, and evaluate their performance by OPNET.

Based on the multiparty quantum secret sharing (QSS) protocol called Zhang–Man protocol, the authors proposed two schemes to enhance the transmission efficiency of whole protocol. In the proposed improved protocol, the dealer can transmit double amount of secret messages at a time securely instead of doing the original Zhang–Man protocol twice. Besides, the authors save a lot of cost of whole QSS system. When the amount of secret messages is large and the number of agents is more, the performance of our protocol is much better than the Zhang–Man protocol. The authors also proposed a reuse scheme, after the secret message had been deduced, the left qubits can be reused for a new round. All of the scheme the authors mentioned above could be extended to multiparty cases in practice.

More people are studying digital video stream transference via networks. However, frequent Internet use increases the requirement for copyright protection and security. As a consequence, to prevent video streams that belong to rightful owners from being intentionally or unknowingly used by others, information protection is indispensable. The authors propose a novel method for video watermarking that is specifically designed for H.264 video. For the experiment, a low-energy signal can relatively guard against low-pass filter attacks. Conversely, a high-energy signal in the host signal can relatively guard against the high-frequency noise attack. In view of these facts, the proposed system design embedding algorithm provides high-energy and low-energy blocks. The blocks in the host image frame are divided into two different groups by estimating the block energy. The existing singular value decomposition methods were employed to calculate the watermark information. In order to enhance the security, the proposed system also employs torus automorphisms to encrypt the watermark. To achieve better robustness, the encrypted results use secret image sharing technology embedded into different I-frames in the video stream.

Outliers in wireless sensor networks (WSNs) are sensor nodes that issue attacks by abnormal behaviours and fake message dissemination. However, existing cryptographic techniques are hard to detect these inside attacks, which cause outlier recognition a critical and challenging issue for reliable and secure data dissemination in WSNs. To efficiently identify and isolate outliers, this study presents a novel outlier detection and countermeasure scheme (ODCS), which consists of three mechanisms: (i) abnormal event observation mechanism for network surveillance; (ii) exceptional message supervision mechanism for distinguishing fake messages by exploiting spatiotemporal correlation and consistency and (iii) abnormal behaviour supervision mechanism for the evaluation of node behaviour. The ODCS provides a heuristic methodology and does not need the knowledge about normal or malicious sensors in advance. This property makes the ODCS not only to distinguish and deal with various dynamic attacks automatically without advance learning, but also to reduce the requirement of capability for constrained nodes. In the ODCS, the communication is limited in a local range, such as one-hop or a cluster, which can reduce the communication frequency and circumscribe the session range further. Moreover, the ODCS provides countermeasures for different types of attacks, such as the rerouting scheme and the rekey security scheme, which can separate outliers from normal sensors and enhance the robustness of network, even when some nodes are compromised by adversary. Simulation results indicate that our approach can effectively detect and defend the outlier attack.

Recently there has been a strong interest in developing networking techniques and important applications for moving vehicles, to enable wireless communication between roadside and vehicles or between vehicles. Vehicular ad hoc networks (VANETs) and vehicular sensor networks (VSNs) using all kinds of wireless technologies has recently received great attention. In the aspect of networking, there are many challenges on how to offer quality of service, build high performance routing, provide mobility management, and create secure VANETs and VSNs. The goal of this Special Issue is to explore the development of vehicular ad hoc and sensor network technologies about communication, networking, and applications.

Trust-aware recommender system (TARS) suggests the worthwhile information to the users on the basis of trust. Existing works of TARS suffers from the problem that they need extra user efforts to label the trust statements. The authors propose a novel model named iTARS to improve the existing TARS by using the implicit trust networks: instead of using the effort-consuming explicit trust, the easy available user similarity information is used to generate the implicit trusts for TARS. Further analysis shows that the implicit trust network has the small-world topology, which is independent of its dynamics. The rating prediction mechanism of iTARS is based on the small worldness of the implicit trust network: the authors set the maximum trust propagation distance of iTARS approximately equals the average path length of the trust network's corresponding random network. Experimental results show that with the same computational complexity, iTARS is able to improve the existing TARS works with higher rating prediction accuracy and slightly worse rating prediction coverage.

The rapid development in electronic commerce and information technology drives the traditional physical product trading evolved to digital product trading. With the effect of the multi-agents system in the Internet environment and the promotions of Government, digital product industry grows fast. The authors proposed a digital product transaction mechanism for electronic auction in the multi-agents system environment. The research introduced a convenient platform to protect the privacies of both buyers and sellers, and track digital product further in an electronic auction environment. In addition, by using simple cryptography techniques supplemented with encryption, the authors ensure the security of information transactions, thereby providing a mechanism of safe and fair digital product electronic auction.

In a multi-agent system, there are many intelligent agents distributed in the network. To connect with these agents easily and arbitrarily, wireless ad hoc network is a candidate. Wireless ad hoc network is a distinct network environment with characteristics in self-organisation, dynamical network topologies and easy construction. To provide such networks with secure communication, many researchers tried different ways to create the session key(s). However, there are some drawbacks in session key generation procedure, and the robust session key could not be created. The authors propose a cluster-based secure communication mechanism in wireless ad hoc networks. The proposal applies the Diffie–Hellman key exchange protocol for the session key creation. It helps the clusterhead to reduce the communication overload, to avoid the time synchronisation problem in nodes authentication and to preserve the complete secrecy requirements.

In wireless sensor networks (WSNs), the operation of sensor nodes has to rely on a limited supply of energy (such as batteries). To support long lifetime operation of WSNs, an energy-efficient way of sensor deployment and operation of the WSNs is necessary. A new controlled layer deployment (CLD) protocol to guarantee coverage and energy efficiency for a sensor network is proposed. CLD outperforms previous similar protocols in that it can achieve the same performances and guarantee full area coverage and connection using a smaller number of sensors. It can also ameliorate the ‘cascading problem’ that reduces the whole network lifetime. Finally, analysis and simulation results show that CLD can use fewer sensor nodes for coverage and also increases the lifetime of the sensor network when compared with the probing environment and adapting sleeping (PEAS) protocol.

Multi-constrained quality-of-service (QoS) routing is used to find routes in a network to satisfy multiple independent QoS constraints. This problem is considered to be NP-complete, and most existing QoS routing algorithms are based on maintaining a global network state at every node. A multi-constrained, flooding-limited, QoS routing method to deal with limited available resources and minimum computation in a dynamic environment is proposed. The solution is based on decomposition of a routing area and a restriction in the exchange of routing information. It reduces the size of the control messages, restricts the amount of routing information, minimises the overhead from the flooding of control traffic and decreases the complexity of path selection. It is also proved that the flooding-limited-path heuristic can achieve very high performance by maintaining entries in each node, which indicates that the performance of the limited-path heuristic is not sensitive to the number of constraints. Simulation results show that this protocol provides better performance than other protocols, especially with regards to end-to-end delay, throughput and packet loss.

Group communication is an important technique for many network computing applications. In group communication, a member in a group sends a message to others normally by multicast. Group signature guarantees the integrity of the exchanged data and provides source authentication. In a virtual machine (VMs) based computing system, a virtual machine monitor (VMM) allows applications to run in different VMs strongly isolated from each other. A trusted VMM (TVMM) based platform can provide stronger security protection for group signature systems than traditional computing platforms can. The authors first introduce a TVMM-based group signature architecture and a TVMM security protection mechanism for group signature components. Then, the authors propose a group signature scheme using the function of message checking based on the discrete logarithm problem. Finally, the authors prove the correctness of the group signature scheme and analyse its security in virtual computing environments.

Weighted fair queueing (WFQ) is a popular scheme because of its guaranteed bandwidth and bounded delay. To make WFQ more flexible, sliding weighted fair queueing (SWFQ) is proposed by combining priority-driven and share-driven scheduling for a real-time network. In this proposal, SWFQ can balance the share and priority-driven characteristics and can allow the application of WFQ to various network environments. This queueing algorithm can also be applied to either IPv4 or IPv6 networks as long as it can provide an adequate quality of service (QoS) support.

To provide cellular data services with QoS provisions, a shared resource scheme, based on optimisation theory and LaGrange λ-calculus, has been developed. This scheme can generate a fair schedule for a diverse mix of traffic with diverse QoS requirements in a limited radio spectrum. The authors define the acceptance indication (AI) as the QoS measurement of the shared resource scheme. The experimental results show that as much as 2.5% improvement in the mean acceptance rate is obtained relative to other existing schemes.