Showing papers in "International Journal of Communication Networks and Distributed Systems in 2012"

Decentralised reinforcement learning for energy-efficient scheduling in wireless sensor networks

Abstract: We present a self-organising reinforcement learning (RL) approach for scheduling the wake-up cycles of nodes in a wireless sensor network. The approach is fully decentralised, and allows sensor nodes to schedule their active periods based only on their interactions with neighbouring nodes. Compared to standard scheduling mechanisms such as SMAC, the benefits of the proposed approach are twofold. First, the nodes do not need to synchronise explicitly, since synchronisation is achieved by the successful exchange of data messages in the data collection process. Second, the learning process allows nodes competing for the radio channel to desynchronise in such a way that radio interferences and therefore packet collisions are significantly reduced. This results in shorter communication schedules, allowing to not only reduce energy consumption by reducing the wake-up cycles of sensor nodes, but also to decrease the data retrieval latency. We implement this RL approach in the OMNET++ sensor network simulator, and illustrate how sensor nodes arranged in line, mesh and grid topologies autonomously uncover schedules that favour the successful delivery of messages along a routing tree while avoiding interferences.

Future wireless networks: key issues and a survey (ID/locator split perspective)

Abstract: Future wireless networks (FWNs) are expected to be a convergence of different kinds of wireless technologies, such as cellular technologies, wireless local area networks (WLANs), wireless metropolitan area networks, wireless sensor networks, and traditional wired networks. The internet protocol (IP) will be potentially adopted as the common networking protocol for diverse networking technologies including the next generation of cellular networks using system architecture evolution (SAE). However, the IP architecture has several known challenges, such as mobility, multihoming, routing scalability, location privacy, path preference selection, etc. One of the greatest problems preventing the networks from overcoming these challenges is that the IP address is contextually overloaded, both as locators and identifiers. As a result, in this paper, we describe the issues of all-IP wireless networks, and survey recent proposals focusing on IP address overloading that can be applied to FWNs.

A taxonomy of secure data aggregation in wireless sensor networks

Abstract: Recent advances in wireless sensor networks (WSNs) have led to several new promising applications including habitat monitoring and target tracking. However, data communication between nodes consumes a large portion of the entire energy consumption of the WSNs. Consequently, data aggregation techniques can significantly help to reduce the energy consumption by eliminating redundant data travelling back to the base station. The security issues such as data integrity, confidentiality, and freshness in data aggregation become crucial when the WSN is deployed in a remote or hostile environment where sensors are prone to node failures and compromises. There is currently research potential in securing data aggregation in WSNs. With this in mind, the security issues in data aggregation for the WSN will be discussed in this article. After that, the |state-of-the-art| in secure data aggregation schemes will be surveyed and then classified into two categories based on the number of aggregator nodes and the existence of the verification phase.

Local key management in opportunistic networks

Abstract: Opportunistic networks are a new and specific type of mobile peer-to-peer networks where end-to-end connectivity cannot be assumed. These networks present compelling challenges, especially from a security perspective, as interactive protocols are infeasible in such environments. In this article, we focus on the problem of key management in the framework of content-based forwarding and opportunistic networks. After analysing this issue and identifying specific security threats such as Sybil attacks, we propose a specific key management scheme that enables the bootstrapping of local, topology-dependent security associations between a node and its neighbours along with the discovery of the neighbourhood topology, thanks to the use of pseudonym certificates and encapsulated signatures.

OFDM/OQAM modulation for efficient dynamic spectrum access

Abstract: The cognitive radio idea consists in the exploitation of spectral resources that are unused by a licensed user within a telecommunication standard. After having detected these available frequency bands by some sensing technique, our work takes a stand on the spectrum access problem. This issue requires some constraints on the modulation that must be taken into account. The flexibility in frequency offered by a multicarrier modulation (MCM) then represents a strong advantage which, in addition, can be fully exploited by the OFDM/OQAM modulation. Indeed, the fact that well localised frequency pulse shapes can be employed makes this modulation attractive for an optimised dynamic spectrum insertion. OFDM/OQAM and OFDM-based solutions are finally tested considering two different transmission scenarios. In both scenarios, it is shown that, for OFDM/OQAM, the time-frequency localisation criterion leads to a short prototype filter, satisfying a good compromise in terms of complexity/performance and also leads at the same time to a better peak-to-average power ratio (PAPR) distribution when compared to an analogue windowed OFDM scheme.

A continuous-time Markov chain model and analysis for cognitive radio networks

Abstract: Cognitive radio concept has been widely researched to improve the spectrum usage efficiency. Appropriate modelling of the spectrum occupancy by both licensed and unlicensed users is necessary to do clear system analysis in a cognitive framework. In this paper, a continuous-time Markov chain model is developed to better describe the radio spectrum usage. The state space vector and the transition rate matrix that completely describe the system are obtained; a steady-state analysis is performed and the stationary state probability (SSP) vector is derived. In addition, we take into account the inaccuracy of the existing spectrum sensing model (missed opportunities), and derive an improved expression for the maximum throughput of secondary users as a function of the primary user traffic parameters and the achieved opportunity ratio (AOR). The optimum sensing period that maximises AOR is also analytically obtained. The proposed model and the derived expressions were examined through numerical analysis and compared with the existing models. This model is very general and applicable to systems with N secondary users in the vicinity of the primary user.

The top ten cloud-security practices in next-generation networking

Abstract: Next-generation networking is moving out of the LAN and adopting cloud computing increasingly. Virtual machines and clouds mask the hardware infrastructure from the LAN administrator as well. Cloud architecture will be ubiquitous and in the future clouds will drop the unnecessary distinction of platform as a service, leaving a slightly larger infrastructure as a service (IaaS) level and an application level (SaaS). Provisioning costs will get lower but the costs of data breaches will continue to climb. This paper explores the security ramifications of cloud-adoption by reviewing the literature and presenting a collection of best-practices for security in the cloud.

Analytical evaluation of P2P reputation systems

Abstract: Despite widespread use of reputation mechanisms in P2P systems, little has been done in the area of analytical evaluation of these mechanisms. Current approaches for evaluation involve simulation and experimentation. These approaches provide evaluation of the mechanism in a few settings in which the experiment is designed; however, it is difficult to use these simulations for direct comparison of reputation mechanisms over a large number of systems and attacker models. In this paper, we present several analytical metrics and a utility-based method for evaluating reputation mechanisms. Further, we provide a case study of an evaluation of the EigenTrust reputation mechanism to demonstrate the use of these metrics and methods.

A seamless handover scheme for vehicles across heterogeneous networks

Abstract: Next generation heterogeneous networks require an effective handover scheme, optimised specially to support network mobility The paper proposes an architecture to support seamless mobility of mobile networks across heterogeneous networks We consider the vehicular scenario where a vehicle is provided with mobility through different internet service providers (ISPs) and propose to use multiple mobile routers-based handover scheme in vehicles The multiple mobile routers architecture is extended to include multiple home agents (HAs) where each HA belongs to different administrative domains We carry out comparative performance evaluation of the handover performance of the proposed scheme in regard to UDP and TCP throughput, service disruption time, and signalling overhead Moreover, we analyse the impact of vehicle speed and overlapping distance of access routers on packet loss during handover period The simulation results show that the proposed scheme provides a mobile network with seamless mobility across heterogeneous networks The overlapped reception of packets from different access routers significantly minimises packet losses during handover even without reducing handover latency

End-to-end modelling and performance analysis for network virtualisation in the next generation internet

Abstract: Coordinating heterogeneous networking systems to meet diverse application requirements has become a significant issue in the future internet. Network virtualisation provides a promising approach to solving this problem. Understanding the end-to-end service performance in future internet is a significant opening topic, which requires modelling and analysis on service provisioning in network virtualisation. Network heterogeneity and resource abstraction in network virtualisation bring new challenges on service modelling and analysis. The research presented in this paper addresses these challenges. The main contributions made in this paper include a new model for end-to-end network service delivery systems in network virtualisation environments, and the techniques for analysing end-to-end performance of service delivery in the virtualisation-based internet. The model and techniques developed in this paper are general and independent of network architectures and implementation technologies; therefore can be applied to analyse the performance of various heterogeneous networking systems converged in the next generation internet.

Fuzzy logic-based transmission power control algorithm for energy efficient MAC protocol in wireless sensor networks

Abstract: In this paper, we investigate the impact of a fuzzy logic control-based transmission power control in a wireless sensor network on the quality of service aspects like average power, energy efficiency, throughput and average end-to-end delay. The transmission power control algorithm is implemented in the medium access control layer as an enhancement for wireless MAC Standard IEEE 802.15.4. For a given fading channel, observations are made regarding received signal strength variations and link quality variations for different distances of separation between transmitter and receiver. The membership functions for the fuzzy logic are then formulated for efficient transmission power control. The transmission power of the source node along with the received signal strength indicator and link quality indicator values measured at the receiving node is used for deciding the required transmission power. The performance of this fuzzy logic-based transmission power control (FTPC_MAC) scheme is compared with the standard IEEE 802.15.4 MAC protocol (IEEE_MAC) and also with location prediction-based transmission power control (LPTPC_MAC). Analytical and simulation results show that fuzzy logic-based transmission power control performs better than the other two MAC protocols.

Security analysis of public cloud computing

Abstract: Cloud computing is in its infancy and continues to evolve. As this evolution proceeds, there are a number of privacy and security concerns emerging from the cloud computing model that need to be addressed before broad acceptance occurs. This paper is an initial literature survey of cloud computing security, which promises to be a challenging research area. Although cloud computing security research inherits previous research from its elemental technologies, this paper will limit its focus on surveying cloud computing targeted research. By performing a systematic analysis of the security aspects of the cloud model, this work seeks to succinctly clarify why security continues to be a significant impediment for cloud adoption.

Task scheduling in heterogeneous distributed systems with security and QoS requirements

Abstract: Heterogeneous distributed systems are continuously being deployed, e.g., P2P and military command, control, communications, computers, and intelligence (C4I). Many of these applications trade-off quality of service (QoS) and security. In this paper, we study the problem of allocating and scheduling a set of dependent tasks with security and QoS requirements on a set of heterogeneous sites. This problem is at least as hard as the basic NP-hard problem of scheduling a directed acyclic graph (DAG) on multiple processors. In particular, we make the following contributions: 1) we formulate the problem as an optimisation problem; 2) we use a branch and bound (BB 3) we propose a heuristic algorithm to provide a near optimal solution for the scheduling of the assigned tasks on a site to maximise the QoS provided by this site in a polynomial time; 4) we evaluate the heuristic algorithm and compare it with some baseline algorithms using variations of synthetic workloads.

Energy efficient automotive networks: state of the art and challenges ahead

Abstract: Rising fuel prices, challenging emission standards and the introduction of electric powertrains lead car manufacturers to explore every possible way to design energy efficient vehicles. Apart from increasing powertrain efficiency, e.g., by downsizing and optimising mechanical components as well as primary aggregates, the development of energy efficient Electric/Electronic-architectures will also contribute towards this goal. However, current architectures support none or only rudimentary power saving mechanisms. Furthermore, system design decisions made in the past such as broadly implementing a cyclic communication paradigm prevent the implementation of simple and straightforward power saving strategies. This paper surveys current in-vehicle Electric/Electronic-architectures and their energy efficiency and outlines new hardware and software approaches that allow for an easy and backwards compatible migration strategy.

Algorithmic approach for clandestine localisation and tracking in short-range environments

Abstract: Target tracking applications have recently evolved becoming essential intelligence and law enforcement tools. Traditionally, long-range communications, such as cellular networks, have been used for this purpose. Such conventional tracking approach, however, usually suffers from several accuracy implications due to location measurement errors. This is exemplified in densely cluttered and indoor environments where measurements are severely affected by excessive environmental and physical noise. Additionally, most localisation and tracking mechanisms today are based on active approach where targets actively cooperate in the tracking process, or at least are aware of it. Clearly, such approach is not suitable for law enforcement applications where targets are suspects or criminals. In this paper, we adopt an algorithmic approach to build an agent-based passive tracking system. We develop a number of algorithms to initiate and maintain this tracking system while consistently preserving passivity.

A hierarchical approach to improve performance of unstructured peer-to-peer system

Abstract: Unstructured overlays have the disadvantage that queries may take a long time to find required data or it does not guaranty to locate an existing data item. We present an organised network architecture for unstructured peer-to-peer systems where nodes are added to the network in a systematic way to efficiently utilise the node resources. This network architecture is characterised by O(log

On the throughput performance of cluster-based cognitive radio networks

Abstract: This paper addresses effect of reporting channel bandwidth on cognitive radio (CR) networks. A cluster based approach is considered where the secondary base station is replaced by a fusion center and a global reporting channel is used instead of local ones. A new approach to select the fusion center based on the general centre scheme in graph theory is proposed. The minimal dominating set (MDS) clustering approach is used to minimise the set of clusters that keeps the network connected. The effect of various parameters such as cluster size and number, quality of the reporting channel and sensing time on sensing efficiency, accuracy and per node throughput are investigated. Results show cluster based cooperative sensing throughput outperforms conventional cooperative sensing especially when the reporting channel has high probability of error. Systematic ways to determine optimum number of clusters and optimum sensing time are developed.

On the improvement of the enhanced distance-based broadcasting algorithm

Abstract: Energy efficiency has attracted a lot of attention during the recent years, especially in mobile ad hoc networks where devices rely on batteries. Moreover, in this kind of networks the cooperation among devices forwarding packets or acting as a router is crucial for the network performance. Thus, reducing the energy consumption of each sending is a key feature that has been widely studied. In this paper we extend the study made for EDB, an enhanced distance-based broadcasting algorithm that aims at minimising the transmission power needed to broadcast a message in the network, by adding different network densities and values for the thresholds. Results showed that reducing the transmission power does not cause any detriment in the network connectivity but it can also increase the performance of the dissemination process.

Cross-layer design in opportunistic spectrum access-based cognitive radio networks

Abstract: Cognitive radio is considered as one of the most important enablers for achieving enhanced spectral efficiency in wireless communications. In this work, we present a cross-layer design for reliable data transmission over a cognitive radio network which combines adaptive modulation at the physical layer and hybrid automatic repeat request at the data link layer. The cognitive radio network follows the principles of opportunistic spectrum access that utilises an optimal power adaptation policy for channel allocation. The obtained numerical results denote that the considered approach achieves significant spectral efficiency improvement and therefore it could be deployed in wireless communication networks that encompass cognitive capabilities. Furthermore, we assess the introduced interference and we show that it can be kept within levels that do not jeopardise our design.

Outage analysis in presence of correlated interferers in a cognitive radio CDMA network

Abstract: In this paper, the outage performance of a primary user (PU) is evaluated analytically in presence of a large number of secondary users (SUs) in an underlay spectrum sharing architecture. We consider cognitive users in ad hoc mode using the spectrum licensed for a cellular CDMA network. We develop an analytical framework for evaluation of downlink interference in our proposed cognitive radio CDMA (CR-CDMA) networking model. A closed form expression for the probability of outage for a PU assuming correlation amongst interferences caused by co-channel BSs and SUs has been derived. We study the impact of SUs and several other parameters (of channel and network) on the outage probability for a PU. Analytical results are validated with simulation results.

SPA-based task scheduling for hypercubic P2P grid systems

Abstract: Most of the existing solutions on task scheduling and resource management in grid computing are based on the traditional client/server model, enforcing a homogeneous policy on making decisions and limiting the flexibility, unpredictable reliability and scalability of the system. Thus, we need a well organised system architecture to provide high system availability with resource scheduling scheme for grid environment. In this paper, we integrate grid with P2P on to the hypercube topology with additional neighbourhood links for task scheduling and load balancing, which gives better makespan and balances the load. We propose the SPA-based task scheduling methodology in order to enhance system performance in hypercubic P2P grid (HPGRID). The simulation results show that the SPA-based min-mean scheduling minimises the makespan along with load balancing and guarantees the high system availability in system performance. At last, the min-mean algorithm is compared with min-min and max-min algorithm using SPA, by simulate experimentation, and it shows that the new algorithm has a better quality of system load balancing and the utilisation of system resources.

Using contracts to induce cooperation in large scale P2P communication networks: algorithms, stability and applications

Abstract: Embedding incentive mechanisms into networking applications (e.g., P2P) is becoming more important for large-scale networking applications since incentive mechanisms can encourage nodes, either end hosts or routers, to cooperate so as to provide a high performance and scalable service. In this paper, we consider a new and novel paradigm of using 'contract' (e.g., an agreement between two communicating parties) to encourage and maintain cooperation. We formally define the notion of contract in a network setting and illustrate its dynamics. We formally show under what conditions a 'balanced' and 'stable' contract can be formed so all participating nodes will have the incentive to contribute. We also propose both centralised and distributed algorithms to find and implement a stable and balanced contract with fairness and security constraints. To illustrate, we show how contracts can be applied to P2P-VoD systems and ISPs networks. In summary, contract can serve as a new genre of incentive mechanism for large scale networking applications.

Multi-layer hybrid wired-cum-wireless sensor network design

Abstract: Sensor networks with sensing, data processing and communicating capabilities have a broad spectrum of applications. Based on application requirements, various network configurations can be designed. One such robust configuration is a hybrid wired-cum-wireless sensor network that is composed of a wireless sensor network and a wired backbone which are inter-connected via access points. In this paper, the joint problem of configuring a hybrid wired-cum-wireless sensor network, position-constrained cluster head and access point placement is proposed. The design considers real wireless communication limitations, optimum locations of access points and cluster heads, and hybrid transmission structure of the network with the objective of minimising the network configuration cost. The problem is formulated as a mixed integer linear programming and solved using 'CPLEX'. Numerical results show that hybrid configuration is more cost effective than the wireless networks and leads to a longer lifetime at the expense of a more complex design.

Efficient detection of primary users in cognitive radio networks

Abstract: This paper proposes an approach to detect the primary user during the communication of the secondary users, using the concept of interference detection in the presence of a desired signal. The detection problem is first formulated as a multi-class classification problem. The pattern with medium bit error rate (BER) and low interference to signal power ratio (ISR) is identified as the most difficult case. A classifier based on a support vector machine (SVM) is proposed to solve this problem. Simulation results yield 76% classification accuracy with ISR larger than -10 dB and a heterogenous channel condition between the primary link and secondary link. Both the channel vacation time and the usage of idle time can be reduced by the proposed approach.

Differentiated service provisioning in the MAC layer of cognitive radio mesh networks

Abstract: MAC protocols utilising the enhanced distributed channel access in IEEE 802.11-2007 can provide differentiated QoS in wireless networks. However, the performance of high priority traffic can be seriously degraded in the presence of strong noise over the wireless channels. Schemes utilising adaptive modulation and coding technique have also been proposed for QoS provisioning. They can provide limited protection in the presence of noise but are ineffective in a high noise scenario. Although multiple non-overlapped channels exist in the 2.4 GHz and 5 GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel at anytime and cannot fully exploit the aggregate bandwidth available in the radio spectrum. By identifying vacant channels through the use of cognitive radios technique, the noise problem can be mitigated by distributing network traffic across multiple vacant channels to reduce the node density per transmission channel. In this paper, we propose the MAC-layer QoS provisioning protocol which combines adaptive modulation and coding with dynamic spectrum access. Simulation results demonstrate that MQPP can achieve better performance in terms of lower delay and higher throughput.

Enhanced service differentiation using priority-based MAC protocol for MANETs

Abstract: MAC layer plays an important role for providing quality of service in mobile ad hoc networks. Accordingly, a real-time data frame should be provided with higher channel access priority than that of a best-effort data frame. This paper proposes a strict priority-based variant of the IEEE 802.11 DCF for QoS provision at the MAC layer of MANETs. The service differentiation is achieved by two mechanisms: a) a priority-based non-overlapping contention window selection, so that smaller backoff timer values are assigned to real-time data frames to reduce their channel access delay; b) a priority-based queue management and packet scheduling to improve the intra-node service differentiation. Performance of the proposed scheme is investigated for single hop scenarios using a Markov chain model whose accuracy is validated through simulation. Furthermore, simulation studies in multihop scenarios show suitability of the proposed scheme to provide an enhanced level of service differentiation, especially in terms of end-to-end delay and throughput, for supporting QoS at MAC layer of MANETs.

Neuro-fuzzy-based hand-off and opportunistic spectrum access for cognitive cooperative network

Abstract: This paper investigates neuro-fuzzy (NF)-based opportunistic spectrum access and spectrum hand-off (HO) for a cognitive cooperative network (CCN). The main aim is to increase the average throughput of the CCN. Secondary users (SUs) in the CCN are scheduled using α-proportional scheduling. The NF α-based algorithm enables each SU to determine the most appropriate channel for its data transmission. SUs keep their transmission power below the interference temperature through power control and do not interfere with the normal operation of primary radio network (PRN). If the quality of service (QoS) of the SU is not obtained, a HO occurs. Mamdani-adaptive neuro-fuzzy inference system (M-ANFIS) is used to construct spectrum access and HO controllers. The proposed algorithm is compared with the existing algorithms. Performance evaluations clearly reveal that the outage probability is reduced and average throughput of the CCN is increased.

A mobile middleware to solve interoperability problems in VOIP streaming session

Abstract: SIP, H.323 and Jingle have been widely used as VoIP protocols. As the session establishment period differs in these protocols and their different implementations, interoperability problems occur. This paper presents a middleware on mobile devices with a generic framework supporting the three protocols and their different implementations. The applications (rmobvoip, rmoblog, mobrmi, mobcorba) implement distributed protocols to solve interoperability problems and to overcome the scarce resources of mobile devices. A peer with this middleware is provided with three options (SIP, H.323 and Jingle) and it can choose any of the protocols or implementations depending on the protocol type used by other peer of the session.

SSO password-based multi-server authentication protocol

Abstract: User's password verification information stored on the server is main point of vulnerability and remains attractive target for attacker. Proposed protocol uses two-server architecture so that password verification information is distributed between two servers known as authentication server and control server. In this paper, we present single sign-on (SSO) password-based multi-server authentication protocol that issues the ticket to the user for a specific time period. Ticket issued for one authentication server can be used by the peer user for its authentication to another authentication server that is under the control of same control server. It distributes password verification information between the authentication server and the control server based on peer-to-peer (P2P) computing. Therefore, the proposed protocol is more resistant to dictionary attack as compared to existing single-server password based authentication protocols. The proposed protocol does not use public key that causes computation and communication burden in resource constraint environment.

Analysis of mobile-oriented energy consumption for heterogeneous connections in hybrid wireless networks

Abstract: While more and more mobile devices are equipped with both cellular and WLAN interfaces for internet access, the energy consumption aspect of these connections has not been studied in depth in the literature. In this paper, a hybrid network with three alternative wireless connections, namely, a cellular component, a combined component with a mixed ad hoc and cellular link, or an infrastructure-based WLAN component, is investigated. A distance-based analysis on the energy consumption of a mobile station has been performed for each alternative wireless connection, and corresponding numerical results have been obtained. The results suggest that, to increase link throughput while maintaining minimal power consumption, the remaining energy of the mobile station as well as the amount of bytes communicated over a link should be taken into consideration for connection selection. Furthermore, the remaining battery level of the mobile station could also be used as the criterion for handover decision, from both the mobile station's and the network operator's perspectives.