Showing papers in "International Journal of Wireless and Mobile Computing in 2007"

Grain: a stream cipher for constrained environments

Abstract: A new stream cipher, Grain, is proposed. The design targets hardware environments where gate count, power consumption and memory is very limited. It is based on two shift registers and a non-linear output function. The cipher has the additional feature that the speed can be increased at the expense of extra hardware. The key size is 80 bits and no attack faster than exhaustive key search has been identified. The hardware complexity and throughput compares favourably to other hardware oriented stream ciphers like E0 and A5/1.

Interworking of 3G cellular networks and wireless LANs

Abstract: The Third Generation (3G) cellular networks provide ubiquitous connectivity but low data rates, whereas Wireless Local Area Networks (WLANs) can offer much higher data rates but only cover smaller geographic areas. Their complementary characteristics make the integration of the two networks a promising trend for next-generation wireless networks. With combined strengths, the integrated networks will provide both wide-area coverage and high-rate data services in hot spots. There are many aspects involved in their interworking, such as mobility, security and Quality of Service (QoS) provisioning. In this paper, we present a survey of most recent interworking mechanisms proposed in the literature, and outline some important open issues to achieve seamless integration.

A security solution for IEEE 802.11's ad hoc mode: password-authentication and group Diffie Hellman key exchange

Abstract: IEEE 802 standards ease the deployment of networking infrastructures and enable employers to access corporate networks while travelling. These standards provide two modes of communication called infrastructure and ad hoc modes. A security solution for the IEEE 802.11's infrastructure mode took several years to reach maturity and firmware is still been upgraded, yet a solution for the ad hoc mode needs to be specified. This paper is a first attempt in this direction. It leverages the latest developments in the area of password-based authentication and (group) Diffie Hellman key exchange to develop a provably secure key-exchange protocol for IEEE 802.11's ad hoc mode. The protocol allows users to securely join and leave the wireless group at time, accommodates either a single-shared password or pairwise-shared passwords among the group members or at least with a central server; achieves security against dictionary attacks in the ideal-hash model (i.e. random oracles). This is, to the best of our knowledge, the first such protocol to appear in the cryptographic literature.

A hybrid data mining anomaly detection technique in ad hoc networks

Abstract: Ad hoc network security mainly relies on defence mechanisms at each mobile node due to lack of infrastructure. For this reason, various intrusion detection techniques have been proposed for ad hoc networks. Developing Intrusion Detection Systems (IDS) for individual nodes in ad hoc network is challenging for a number of reasons, including resource constraints at each node and the difficulties to locate attack source for prompt response. In this paper, we propose a hybrid data mining anomaly detection technique for node-based IDS. Specifically, we incorporate two data mining techniques, that is, association-rule mining and cross-feature mining, to characterise normal behaviours of mobile nodes and detect anomalies by finding deviance from the norm. The advantage of our hybrid approach is that association-rule mining and cross-feature mining usually complement each other in time scale and sensitivity to different attack types. We investigate features of interest from both the medium access (MAC) layer and the network layer. Our intention of using the MAC layer features is to localise the attack source within one-hop perimeter. To preserve the precious energy of mobile nodes, we propose two compact feature sets, that is, direct feature set and statistical feature set, that target on short-term and long-term profiling of normal node behaviours, respectively. Considering the characteristic of audit data collected upon different feature sets, we apply association-rule mining to the short-term profiling and cross-feature mining to the long-term profiling. We validate our work through ns-2 simulation experiments. Experimental results show the effectiveness of our method.

Modelling and evaluation of the 3G mobile networks with hot-spot WLANs

Abstract: An analytical modelling and evaluation approach is developed for the integrated 3G/WLAN networks. The cell residence times of different types of users are modelled as a general distribution to adapt various mobility environments. The explicit expressions of channel occupancy times are determined by the Laplace transform approach. The horizontal and vertical handoff rates as well as some interesting performance measures are also derived and calculated by introducing an iterative algorithm. Both our analysis and our numerical results show that the performance of the 3G network is significantly increased when the integrated 3G/WLAN network is employed, especially when the WLANs are in the hot-spot areas. The method developed here is expected to be useful for the modelling and performance evaluation of other kind of networks, such as the 3G networks with the infrastructureless-mode WLANs or ad hoc networks.

Denial-of-service resistance in key establishment

Abstract: Denial of Service (DoS) attacks are an increasing problem for network connected systems. Key establishment protocols are applications that are particularly vulnerable to DoS attack as they are typically required to perform computationally expensive cryptographic operations in order to authenticate the protocol initiator and to generate the cryptographic keying material that will subsequently be used to secure the communications between initiator and responder. The goal of DoS resistance in key establishment protocols is to ensure that attackers cannot prevent a legitimate initiator and responder deriving cryptographic keys without expending resources beyond a responder-determined threshold. In this work we review the strategies and techniques used to improve resistance to DoS attacks. Three key establishment protocols implementing DoS resistance techniques are critically reviewed and the impact of misapplication of the techniques on DoS resistance is discussed. Recommendations on effectively applying resistance techniques to key establishment protocols are made.

The performance of a watchdog protocol for wireless network security

Abstract: In wireless networks, a watchdog mechanism can be a part of the security architecture used to identify nodes that fail to forward the packets they agree to forward. In this paper, we propose two protocols to address the ambiguous collision limitation of watchdogs. The Watchdog Alert (WA) and Watchdog Confirmation (WC) protocols are variants of the Carrier Sense Multiple Access with Collision Avoidance Protocol (CSMA/CA). We analyse the trade-offs between throughput and watchdog success probability of each protocol, comparing it to CSMA/CA.

Ad hoc assisted handoff for real-time voice in IEEE 802.11 infrastructure WLANs

Abstract: In this paper we propose and investigate the use of IEEE 802.11 Ad Hoc Assisted Handoff (AAHO), where a single additional ad hoc hop may be used by a Mobile Station (MS) to obtain range extension or channel quality needed to maintain its real-time voice connection. There are the versions of IEEE 802.11 AAHO. In Backward Ad Hoc Assisted Handoff (BAAHO) the additional hop uses a relay station which already has an IEEE 802.11 association with the access point that the MS is using. In Forward Ad Hoc Assisted Handoff (FAAHO) the additional hop uses a relay station whose access point is different from the one that the MS is currently associated with. Hybrid Ad Hoc Assisted Handoff (HAAHO) is a combination of the two and allows an MS to perform either BAAHO or FAAHO. The proposed AAHO designs are backward compatible, in that they can be implemented as a transparent overlay across existing IEEE 802.11 infrastructure deployments. A relaying mechanism is introduced which permits stations to control the real-time relaying of voice packets between the channels. An analytical model is developed to study the performance of the proposed AAHO schemes based on a simplified system model. Detailed simulation results show that AAHO can greatly improve the handoff connection dropping probability for an IEEE 802.11-based WLAN with incomplete AP coverage and relatively fast moving MSs and HAAHO can achieve even better performance than BAAHO. Our results also show that the proposed AAHO schemes can maintain good real-time performance, in terms of packet transmission delay, for voice transmissions.

Seamless multimedia sessions and real-time measurements in hybrid 3G and WLAN networks

Abstract: This paper addresses the issue of multimedia service provisioning in heterogeneous network environment (WLANs and 3G systems). Particular emphasis is given on the interactions between multimedia signalling, mobility management and AAA interactions. The measurements are associated with service registration/authentication, video streaming within WLAN homogeneous environments and session transfer during movement across homogeneous and heterogeneous network environments. Furthermore, the impact of mobility management on the performance of multimedia services in terms of session reestablishment and packet loss is presented.

Security mechanisms and vulnerabilities in the IEEE 802.15.3 wireless personal area networks

Abstract: The IEEE 802.15.3 specification is proposed for short-range high-speed Wireless Personal Area Networks (WPANs). Furthermore, it is proposed by the IEEE 802.15.3 a task group for Ultra-Wideband (UWB) transmission, which is an emerging wireless technology for future indoor and outdoor applications. This paper gives a survey on various security aspects and mechanisms in the IEEE 802.15.3 WPANs. It provides security analysis, points out some errors and security vulnerabilities of these networks and provides some corrections.

Mobility model used for QoS management for wireless multimedia networks

Abstract: A radio service and more particularly for multimedia services, the availability of the resources often fluctuates, according to the load, mobility of users and variation of the transmission quality. The fluctuation is a major problem for radio network operators to adapt the use of the resources considering the mobility of the users. The allocation of the bandwidth of various types of traffic is done only at fresh call arrival or for a handover. The mobility of the users has an important influence on the configuration of the network. Such intercellular handover modifies the distribution of the traffic in the system and generates additional signalling load. In this study, we consider the mobility of the users in the dimensioning network and four traffic models (voice, video, www and ftp). This mobility model allows us to determine at the cell level as well as at the entire system level, for QoS parameters, threshold values beyond which a call can be blocked.

Mobile face detection and tracking for media streaming applications

Abstract: This paper presents a method for mobile face detection and tracking in media streaming applications. To account specifics of mobile image processing and pattern recognition, the experimental benchmarking of Intel x86 and Nokia S60 platforms is done. Various aspects on mobile phone use are considered in order to record a profile on a mobile media streaming user. The profile is generated by analysing pictures of mobile phone users and screenshots of their devices. The mobile face detection model is based on the optimised version of robust real-time object detection algorithm. Our optimisation enables to reduce the computational complexity of the original version in 4 times. We also describe the tracking mode in which the system achieves a near real-time frame rate (45 12 fps depending on the video complexity). The training of the face detector is done on the databases of more than 400 hr of video and the major parameters such as FRR and FAR are evaluated on a database of 30 min of video (including more than 5000 facial images) and 200 hr of video, respectively. Face tracking is benchmarked using 20 mobile video sequences, which cover a broad range of human activities and environmental changes. We describe the construction of the low bit-rate video coder that uses face detection and tracking to segment foreground/background object and encode them with a different bit-rate. We also describe a framework for smart videoconferences and experimental results on low bit-rate image coding for this application.

Optimising uplink scheduling in an integrated 3G/WLAN network

Abstract: We propose a hybrid uplink architecture that seamlessly integrates 802.11 WLAN (ad hoc mode) and WCDMA interfaces. In our scheme, mobile stations can be dynamically appointed as a Relaying Mobile Terminal (RMT) to forward uplink traffic. The RMT terminals significantly reduce the overall transmission activity and out-of-cell interference to the neighbouring cells. To find the close approximation of the optimum RMT set, we propose a two-approximation-based heuristic algorithm that is originally used to solve a minimum vertex set. The algorithm results in low out-of-cell interference, and the selected RMT terminals have good channel quality with the base stations. We further investigate the optimum uplink traffic scheduling algorithm subject to different Quality of Service (QoS) requirements (i.e. Bit-Error-Rates (BER)) and limited power budget at the RMT terminals. To provide a fair access and also have high radio efficiency (via spatial diversity), we adopt a proportional scheduling algorithm to coordinate the transmission among RMTs. Within a RMT, packets of different BER requirements are further scheduled via link-adaptive CDMA transmission scheme. We demonstrate that power/code allocation (inside the RMT scheduler) enables the reassignment of the slack power among traffics according to their BER requirements. It is thus possible that some BER-stringent traffic can be transmitted at a higher data rate. The simulation results are promising, showing at least 28% increase in overall throughput at different traffic patterns, including performance-guaranteed multimedia streams.

Delay and traffic based on-demand routing algorithms for improving energy efficiency in mobile ad hoc networks

Abstract: Reducing power consumption and increasing battery life of nodes in an ad hoc network require an integrated power control and routing strategy. The control is better attained by new route selection mechanisms for MANET routing protocols, which we call Energy Based Time Delay Routing (EBTDR) and Highest Energy Routing (HER). These two algorithms try to increase the operational lifetime of an ad hoc network. In this paper, a couple of modifications to the basic DSR protocol are proposed so as to make it energy efficient. First, a delay is introduced in forwarding the packets by nodes, which is inversely proportional to the remaining energy level of the node (EBTDR). Second, energy information is included on the Route Request (RREQ) packet and the route is selected based on this information (HER). The energy Drain Rate (DR) is included in the cost metric to improve the fidelity of the HER algorithm as it provides an optimised solution by the link traffic in the network. Based on the simulation results obtained, it is observed that our algorithms increase the lifetime of Mobile Ad hoc Networks (MANETs), at the expense of delay in route discovery and control overhead.

Automated detection and containment of worms and viruses into heterogeneous networks: a simple network immune system

Abstract: While much recent research concentrates on propagation models, the defence against worms is largely an open problem. Classical containment strategies, based on manual application of traffic filters, will be almost totally ineffective in the wide area since the worms are able to spread at rates that effectively preclude any human-directed reaction. Consequently, developing an automated, flexible and adaptive containment strategy is the most viable way to defeat worm propagation in an acceptable time. As a case in point, we look to natural immune systems, which solve a similar problem, but in a radically different way. Accordingly, we present a cooperative immunisation system inspired in principles and structure by the natural immune system that helps in defending against these types of attacks. Our system automatically detects pathologic traffic conditions due to an infection and informs, according to a cooperative communication principle, all the reachable networked nodes about the ongoing attack, triggering the actions required to their defence. To evaluate our proposal, we formulated a simple worm propagation and containment model, and evaluated our system using numerical solution and sensitivity analysis. Our measurements show that our reaction strategy is sufficiently robust against all the most common malicious agents. We envision that the above solution will be an effective line of defence against more aggressive worms.

Robust source-adaptive real-time video transport over wireless multihop networks

Abstract: Packet video transport, including streaming, over wireless networks is expected to experience substantial performance variations. But, in wireless networks, channel state information is hard to be obtained reliably/timely. However, the source information is always available and can be obtained accurately. In this paper, we propose, instead, the use of source information alone to implement an Unequal Error Protection (UEP) approach based on adaptation to inter-frame motion. To implement our Forward Error Correction (FEC)/UEP approach, a novel cross-layer packetisation scheme is proposed. Based on Exponential Weighted Moving Average (EWMA) estimation for the motion-level information associated with video frames, a source-adaptive intra-updating rate selection is described to provide error-resilience. To combat severe bursty losses, a novel intraframe packet interleaving scheme is implemented at the applicationlayer. Our objective and subjective results demonstrate the effectiveness of our approach in dealing with the bursty packet losses occurring on wireless networks.

DDoS: design, implementation and analysis of automated model

Abstract: Earlier, we have proposed an automated model to minimise DDoS attacks in single ISP domain and extended the model to multiple ISP domains. Our approach has several advanced features to minimise DDoS attacks in the internet. The focus of this paper is twofold: firstly, to present a detailed description of the design and implementation of the proposed model and second to discuss and analyse the extensive set of results obtained from the implementation and simulations. We describe the prototype implementation of our automated model using NetProwler network intrusion detection system and HP OpenView Network Node Manager. We will also discuss the performance analysis of our model on a large scale using NS2 tool. Both prototype and simulation test results confirm that our approach offers a promising solution against DDoS problem in the internet and the model can be implemented in real time with minor modifications to the existing tools.

Design and implementation of an integrated accounting architecture for distributed UMTS and WLAN networks

Abstract: Accounting for resource and service usage in communication networks forms the basis of network operators' business, and is therefore essential. Within a heterogeneous, multidomain mobile environment of emerging new access technologies, the demand for a distributed accounting infrastructure becomes more relevant. Driven by the analysis of current accounting solutions in Universal Mobile Telecommunications System (UMTS) and Wireless Local Area Networks (WLAN) networks, the newly developed approach presents an integrated accounting architecture based on the Diameter protocol, forming a flexible basis for charging UMTS and WLAN communication services. The system developed is described, discussed and evaluated by a prototypical implementation.

Towards all-IP wireless networks: architectures and resource management mechanism

Abstract: Future wireless internet will consist of different wireless technologies that should operate together in an efficient way to provide seamless connectivity to mobile users. The integration of different networks and technologies is a challenging problem mainly because of the heterogeneity in access technologies, network architectures, protocols and service demands. Firstly, this paper discusses three architectures for an all-IP network integrating different wireless technologies using IP and its associated service models. The first architecture, called ISB, is based on a combination of Differentiated Services (DiffServ) and Integrated Services (IntServ) models appropriate for low-bandwidth 3G cellular networks with significant resource management capabilities. The second architecture, called DSB, is purely based on the DiffServ model targeted for high-bandwidth wireless LANs with little resource management capabilities. The last architecture, called AIP, combines ISB and DSB architectures to facilitate the integration of wireless LAN and 3G cellular networks towards a uniform architecture for all-IP wireless networks. Secondly, this paper proposes a flexible hierarchical resource management mechanism for the proposed All-IP Architecture (AIP) which aims at providing connection-level Quality of Service (QoS) for mobile users. Simulation results show that the proposed mechanism satisfies the hard constraint on connection dropping probability while maintaining a high-bandwidth utilisation.

Wireless video streaming over integrated 3G and WLAN networks

Abstract: Media streaming is a popular application demanding high data rates and hard delay constraints. These requirements raise great challenges in the wireless environment, where signal fading, noise interference and network congestion introduce data losses or corruptions. Today, the availability of the Third Generation (3G) wireless system and the Wireless Local Area Network (WLAN) provides a broader bandwidth to cater for multimedia application. Different characteristics of 3G and WLAN networks result in different attributes in video streaming applications. In this paper, we propose a collaborative scheme across 3G and WLAN networks for video streaming, using layered video coding and Unequal Error Protection (UEP) to improve the perceived video quality.

Adaptive semi-soft handoff for Cellular IP networks

Abstract: Various advances in technologies have led to a myriad of wireless mobile devices to ubiquitously connect to the internet. This creates a significant demand for seamless wireless network connectivity. The Cellular IP semi-soft handoff protocol has been proposed to satisfy this demand. Studies have shown that it performs better than the conventional hard handoff protocol. However, these studies are based on unrealistic assumptions of symmetrical network topologies and fixed loads. In practice, network topology can be asymmetric and network load fluctuates. Semi-soft handoff uses fixed handoff parameters for stream synchronization and mobile host's tune-in time, which may work well for the symmetrical network setups, but performs poorly with unbalanced and dynamically changing networks. This paper proposes adaptive semi-soft handoff protocol (Adaptive-SS) to address this issue by dynamically changing handoff parameters based on network conditions during handoff. Our simulation study shows that Adaptive-SS significantly reduces network traffic and packet losses/duplications during handoff, while still minimising handoff latency.

A generic architecture for 'always best connected' UTMS/WLAN mobile networks

Abstract: The 4G mobile era will be based on a heterogeneous infrastructure comprising different wireless (and wired) systems in a complementary manner, where users will enjoy ubiquitous access to applications in an 'Always Best Connected' (ABC) mode that utilises the most efficient combination of systems available (e.g. UMTS and WLAN). We analyse the 'ABC' concept in an interworked UMTS/WLAN network context and reveal important issues. Next, we identify major requirements of the 'ABC' capacity, point out the limitations of UTMS/WLAN standards and discuss key enabling technologies and research efforts. We develop an application model for 'ABC' and analyse its complexity proving that, in principle, being 'ABC' translates to a family of NP-hard problems. Next, we present the design of an object-oriented UML real-time model for an 'ABC' system and provide preliminary results from simulation scenarios. In conclusion, we summarise the advantages of our 'ABC' model and provide directions for future work.

Developing a QoS framework for media streaming over TDMA/TDD wireless networks

Abstract: Recent advances in wireless technology are enabling the design and deployment of multiservice wireless networks. In order to be able to meet the QoS requirements of the various applications, it is essential to deploy QoS provisioning mechanisms. In this paper we present a QoS framework to support various types of services in a wireless networking environment. In particular, the proposed framework is used to design various QoS provisioning mechanisms for time-constrained variable bit-rate applications. Under this QoS framework we propose various Resource Request (RR) mechanisms. We carry out a comparative study of the proposed schemes. Our simulation results show the effectiveness of the mechanisms when supporting media streaming services, such as MPEG-4 video communications.

WAQM: managing QoS in wireless networks by means of an XML-based multiagent system

Abstract: In this paper, we propose WAQM, a novel XML-based multiagent system for Quality of Service (QoS) management in wireless networks. WAQM is characterised by the following features: (i) it handles a user profile and exploits it jointly with suitable network resource management techniques to maximise user satisfaction; (ii) it is semi-automatic; (iii) it exploits XML for guaranteeing a light, versatile and standard mechanism for information representation, storing and exchange. In this paper, the basic features of the system are discussed into detail. Furthermore, the main results of a performance evaluation study aiming at comparing it with alternative agent-based approaches for handling user access to telecommunications networks are reported.

Constraint-based media content delivery over heterogeneous networks and devices

Abstract: Mobile and wireless technology has attained a great penetration in the market during the recent years. The need to deliver media content to a great variety of mobile and wireless devices is delineated as the indisputable future trend. This is instigated by the fact that wireless networks can now support the quality requirements of media streaming delivery, while mobile devices are able to present a variety of media content. This paper presents the Enamorado architecture that allows decoupling the development of mobile devices from advances in content formats and implements an intelligent system that selects the most appropriate content format in terms of for example device limitations, end-user preferences and current network conditions. This is particularly important, in cases which demand maximising the number of admitted users, without compromising the user's quality standards. Finally, this paper presents a case study to present how the system's intelligence is applied in a real network.

User assignment strategies for throughput maximisation in hierarchical wireless networks

Abstract: Hierarchical wireless networks such as the 3G/WLAN integrated networks are considered as a promising solution to effectively support next-generation wireless applications. We investigate the problem of assigning mobiles to the different layers in such networks. In this paper, we focus on the real-time application users, while the case of non-real-time users is treated in a separate paper. By real-time applications, we mean the applications which can adapt their data transmission rate (i.e. throughput) depending on the current channel conditions. The connection time (i.e. the call holding time) of these elastic applications is typically independent of their throughput. Such applications would for example include multimedia applications that can adjust the quality of the audio/video signal in order to adapt to lower network capacities. We present a generic framework under which different assignment strategies can be formulated and evaluated. Specifically, three assignment schemes which utilise the estimated velocity and/or the requested data rate of the mobiles are studied. The relative merits of these schemes are compared and it is in particular shown that, under various circumstances, the joint velocity-rate decision scheme significantly outperforms the other two schemes (i.e. velocity- and rate-only decision schemes). Extensive numerical results are presented to quantify the respective performances and to study the influence of relevant system parameters. Our main contribution is to build a generic framework for optimal user assignments, into which various wireless technologies can be plugged.

Rate adaptation for wireless video streaming based on error statistics

Abstract: This paper presents a new rate-control algorithm for live video streaming over wireless IP networks, which is based on selective frame discarding. In the proposed mechanism excess 'P' frames are dropped from the output queue at the sender using a congestion estimate based on packet loss statistics obtained from RTCP feedback and from the Data Link (DL) layer. The performance of the algorithm is evaluated through computer simulation. This paper also presents a characterisation of packet losses owing to transmission errors and congestion, which can help in choosing appropriate strategies to maximise the video quality experienced by the end user.

A rate adaptation scheme for media streaming over heterogeneous networks

Abstract: In this paper, a Rate Adaptation Scheme (RAS) for media streaming applications, appropriate for future heterogeneous networks is presented. In such environments, vertical handovers across networks with highly diverse characteristics are likely to occur. In these cases, RASs should cope with abrupt network resources variations. Existing rate adaptations mechanisms would fail to adjust, in a timely manner, to the characteristics of the new network or recognise a vertical handover event. The proposed scheme enhances an existing rate adaptation algorithm towards providing uninterrupted streaming sessions to mobile terminals, when moving across networks with diverse characteristics. Applications can adapt their rate, based not only on application level feedback (e.g. packet and frame loss rate), but also on feedback received from a terminal management entity. The proposed scheme is evaluated using extensive simulations, is implemented over an open end-to-end MPEG-4 streaming suite and it is experimentally validated.

TCP-friendly MPEG-4 streaming video in CDMA networks via power and rate control

Abstract: A power and rate adaptation scheme for CDMA networks is proposed that uses information from the TCP-friendly (TFRC) transport protocol and the type of MPEG-4 frame (i.e. Intra, Predictive or Bidirectional) together with lower layer criteria in order to optimise packet transmission over the wireless link. A multiobjective optimisation problem is formulated based on the weighted sum of two competing objectives and is solved using derivative based optimisation techniques. The first objective expresses the absolute difference between the required transmission rate as defined by the TFRC and the allocated rate and the second is the total consumed power. Furthermore, in the proposed scheme, the allocated bit-energy-to-interferencepower-spectral-density ratio, Eb/I0, depends on the type of video frame being transmitted. Based on a derived condition for optimal allocation, heuristic allocation is performed. Finally, through simulation results the proposed scheme is evaluated and possible different ramifications of the scheme are discussed.