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Cognitive radio (CR) enabled dynamic spectrum access (DSA) networks are designed to detect and opportunistically utilise the unused or under-utilised spectrum bands. However, due to the open paradigm of CR networks and lack of proactive security protocols, the DSA networks are vulnerable to various denial-of-service threats. The authors propose a game-theoretic framework to study the primary user emulation attack (PUEA) on CR nodes. A non-cooperative dynamic multistage game between the secondary nodes and the adversaries generating the PUEA is formulated. The pure-strategy and mixed-strategy Nash equilibria for the secondary user and malicious attacker are investigated. Moreover, a novel belief updating system is proposed for the secondary user to learn the state of the primary user as the game evolves. Simulation results demonstrate that the proposed belief updating system achieves better performance than other models for the secondary user in terms of greater payoff, lower probability of missing primary user and better robustness to the inaccurate estimation of the primary user's state. [ABSTRACT FROM AUTHOR]

Digital communication networks are a core technology in advanced building automation systems. Building automation and control network (BACnet), a data communication protocol designed specifically for building automation and control systems, uses the master-slave/token-passing (MS/TP) protocol as one of its field-level networks. Previously, the authors introduced a basic concept of bandwidth allocation for MS/TP to improve its real-time communication capability. In this study, the authors developed a communication module that implements the proposed scheme, and used it in an experimental model to examine the validity of the bandwidth allocation scheme for MS/TP. Experimental results show that the modified MS/TP protocol satisfies the requirements for real-time communications using cyclic and life-safety messages in BACnet communication services. [ABSTRACT FROM AUTHOR]

A plethora of modifications to transmission control protocol (TCP) have recently been proposed, a major aim being to improve its performance over wireless links. Two schools of thought have emerged: the first investigates changes to the transport-layer protocol, whereas the second explores the potential to enhance the characteristics of lower layers to improve the end-to-end performance of TCP. This study focuses on the latter, and, in contrast to most research in this area, which thus-far has concentrated on a single TCP flavour, examines the case where different TCP flavours are competing over a wireless link. To this end, the authors present and assess a cross-layer solution to adapt the coding rate at the link-layer based on the detected TCP flavour, to maximise fairness among TCP flows. Through both analysis and simulation, the authors show that the proposed scheme considerably improves the fairness among different TCP flavours that compete over a wireless link. Furthermore, the proposed approach has minimal detrimental effect on the aggregate throughput of TCP flows. [ABSTRACT FROM AUTHOR]

This study studies the received buffer blocking problem caused by traditional concurrent multipath transfer protocol. The authors propose a new transport protocol, named wireless concurrent multipath transfer stream control transport protocol (WCMT-SCTP), to solve the received buffer blocking problem. It can bind certain data streams to certain paths and use multiple active paths to transfer data simultaneously. The authors evaluate the performance of WCMT-SCTP through theoretical analysis and extensive simulation. Both simulation and analysis results show WCMT-SCTP can improve the system throughput obviously and keep the independence of data streams. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Network coordinates (NC) system is an efficient mechanism for Internet distance prediction with scalable measurements. The intrinsical cause for the unsatisfactory accuracy of the simulation-based NC algorithms has been identified. Then Pharos, a fully decentralised and hierarchical scheme, is proposed to solve this problem. Pharos leverages multiple coordinate sets at different distance scales, with the right scale being chosen for prediction each time. We evaluate the performance of Pharos system with the King data set and latency data from PlanetLab, and compare it with the representative NC system, Vivaldi. The experimental results show that Pharos greatly outperforms Vivaldi in Internet distance prediction without adding any significant overhead. Our extensive evaluation results also demonstrate that Pharos can significantly improve the performance in distributed Internet applications, such as overlay multicast and server selection. [ABSTRACT FROM AUTHOR]

Top-of-the-range smart phones are among today's most desired technological status symbols. Armed to the teeth with email, highspeed Internet access, PC synchronisation, digital still photography, audio and video capture and reproduction, television reception, removable storage, contactless payment, Bluetooth, Wi-Fi .and GPS, today's smart phones are already as far removed from simple cellular voice devices as sportcars are from the humble hatchback. [ABSTRACT FROM AUTHOR]

The authors present an extensive investigation of the performance of the IEEE 802.11 medium access control (MAC) protocol, with respect to throughput and delay. For the protocol analysis, a new model, which describes the protocol's behaviour to a great extent by incorporating and extending the existing models, is proposed. The authors also present a detailed analysis of the end-to-end delay through the study of the MAC delay and the queueing delay. The authors use the Z-transform of backoff duration to obtain the mean value, the variance and the probability distribution of the MAC delay. For the queueing analysis, first the authors consider an M/G/1 queue in order to provide a first look at the queueing delay. Second, the authors modify the input process of the queue so that the packet arrival process is described by an ON–OFF model, which expresses the bursty nature of traffic. In the investigations, data rates of 1, 5.5 and 11 Mbps are assumed to highlight the effect of the bit rate on network performance for both Basic and request-to-send/clear-to-send access mechanisms. The throughput and delay analyses are validated by simulating the distributed coordination function, whereas the models are compared with the existing models based on their results. The accuracy of the analyses was found to be quite satisfactory. [ABSTRACT FROM AUTHOR]

Nonlinear dynamic behaviour of transmission control protocol (TCP) in universal mobile telecommunications system (UMTS) networks is proposed. The dynamic characteristics of TCP are explored using the fundamentals of chaos theory, and the occurrence of chaotic behaviour in relation to the feedback that is received (packet drops, packet delays) by TCP from the network is explained theoritically. To validate the concept proposed, a model of the UMTS network is built and simulated under various user traffic loads. Using standard chaos methodology, it was found that inside the UMTS the TCP exhibits aperiodicity and sensitivity to initial conditions that are inherent characteristics of chaos. In particular, simulation results illustrate that as the traffic load increases, the behaviour of the network ranges from periodically stable to chaotic, with a direct impact on the quality of service of the network. [ABSTRACT FROM AUTHOR]

In infrastructure wireless networks, the wireless hop can be considered as another hop of the transmission path. With the rapid growth of wireless traffics, the future wireless network is expected to provide services for heterogeneous data traffics with different quality of service (QoS) requirements. Most proposed schemes do not have adaptive mechanisms to deal with the environment changes. In real situation, bandwidths, error rates and loss rates of wireless links vary frequently. We will base on the differentiated service model and propose a wireless differentiation (WD) scheme for user datagram protocol (UDP) flows and a wireless differentiation with prioritised ACK scheme for connections with transmission control protocol (TCP) flows. Both schemes provide QoS support for IEEE 802.11b and do not change the basic access mechanism of IEEE 802.11b. [ABSTRACT FROM AUTHOR]

Multicast-based data communication is an efficient communication scheme especially in multihop ad hoc networks where the MAC layer is based on one-hop broadcast from one source to multiple receivers. The problem of resource allocation for a set of homogeneous multicast sessions over multihop wireless network is addressed. An iterative algorithm is proposed that achieves the optimal rates for a set of multicast sessions such that the aggregate utility for all sessions is maximised. The authors demonstrate analytically and through simulations that the algorithm achieves optimal resource utilisation while guaranteeing fairness among multicast sessions. The algorithm in network environments with asynchronous distributed computations has been further analysed. Two implementations for the algorithm based on different network settings are presented and show that the algorithm not only converges to the optimal rates in all network settings but it also tracks network changing conditions, including mobility and dynamic channel capacity. [ABSTRACT FROM AUTHOR]

The conventional layered protocols in ad hoc networks tend to suffer from the inability to distinguish between losses due to route failures and congestion because of the inflexible structure. Recently, in efforts to overcome the challenges of dynamic environment, there have been increased interests in protocols that rely on interactions between different layers. The authors propose a cross-layer multicasting scheme based on the concept of local backtracking groups and adequate buffer equipped within nodes to avoid undesired retransmission from the source and further to improve the efficiency of source-to-receivers delivery with the aid of buffer. While encountering route failure, a node can quickly restore its routing paths to multicast subscribers by exploiting the precise notification from the MAC layer and the parent group then opportunely provides it with an unacknowledged packets conserved in the buffer. It is obviously benefic that retransmission packets are issued from the parent group rather than from the source. The authors present both analytic models and simulation results that substantiate the efficiency and robust of our approach based on realistic mobility scenarios. [ABSTRACT FROM AUTHOR]

Infrastructure wireless mesh network, also named as mesh router, is one key topology for the next generation wireless networking. In this work, the performance optimisation for the infrastructure wireless mesh network is presented and the sub-optimum solution mechanism is investigated. A cross-layer design for tree-type routing, level-based centralised scheduling and distributed power control theme is proposed as the sub-optimum solution strategy. The cross-layer design relies on the channel information and the distributed transmission power control in the physical layer, and the wireless scheduling in the medium access control (MAC) layer, as well as the routing selection mechanism in the MAC upper layer. In this work, a modified distributed power control algorithm is proposed first. In addition, a tree-type routing construction algorithm for centralised scheduling is presented to improve the network throughput by jointly considering interference and hop-count to construct the routing tree. Simulation results show that the proposed cross-layer design strategy can effectively improve the network throughput performance, decrease the power consumption and achieve better performances. [ABSTRACT FROM AUTHOR]

Queue management, bandwidth share and congestion control are very important to both the robustness and fairness of the Internet. A new TCP-friendly router-based active queue management scheme, called WARD, approximates the fair queueing policy. WARD is a simple packet dropping algorithm with a random mechanism and discriminates against the flows which submit more packets per second than is allowed by their fair share. By doing this, it not only protects transmission control protocol (TCP) connections from user datagram protocol (UDP) flows, but also solves the problem of competing bandwidth among different TCP versions, such as TCP Vegas and TCP Reno. Furthermore, it is stateless and easy to implement, so WARD controls unresponsive or misbehaving flows with a minimum overhead. In this article, we present a deterministic fluid model of TCP/WARD system, and explain the UDP throughput behaviour with WARD. Also, we prove that, provided the number of TCP flows is large, the UDP bandwidth share peaks at (2e)-1=0.184 when UDP input rate is slightly larger than link capacity and drops to zero as UDP input rate tends to infinity. [ABSTRACT FROM AUTHOR]

The results of a performance analysis of mobile agents in a distributed network environment are presented. Analytical models are developed and used to compare the performance of carrying out a simple management function with mobile agents (MA) or SNMP (simple network management protocol). An examination is made of how delay is affected by the size of the management domain and how each method behaves in both a local area network (LAN) and wide area network (WAN) environment. For large domains, optimal performance is obtained if the mobile agents' size is bounded, and this may require sharing the management task among a small number of mobile agents. [ABSTRACT FROM AUTHOR]

The paper describes a new attack on the improved robust generalised MQV key agreement protocol without using one-way hash functions proposed by Zuhua Shao. [ABSTRACT FROM AUTHOR]

A Gilbert-gamma topology is proposed to model packet-loss processes in UDP connections. The proposed topology introduces state duration modelling with gamma distributions. When compared with the ordinary Gilbert model the proposed topology substantially improves the likelihood of observed packet-loss processes, and gives reductions as high as 70% in the subjective estimation of speech quality transmitted over IF networks. The results presented can be easily applied to other real-time applications such as audio and video streaming. [ABSTRACT FROM AUTHOR]

A novel statistical model, the one-dimensional hyperbolic distribution, is proposed for network traffic activity. This includes the modelling of network traffic performance and descriptive parameters, organised as probability distribution functions of activity monitored during an observation window. This model promises accurate representation in a compact manner, of particular interest in statistical anomaly intrusion detection systems. The hyperbolic distribution has been tested in modelling several performance parameters in data traces of IP traffic collected from various actual network environments, including the campus LANs of the New Jersey institute of Technology and the WAN of the Bergen County Cooperative Library Network System (BCCLNS), as well as simulated client-server LANs. By fitting the model parameters to the experimental data, it is shown that this analytic model performs significantly better than the models currently in common use, such as the Weibull, Pareto, normal and lognormal distributions. [ABSTRACT FROM AUTHOR]

A study of a prefix routing cache for Internet IP routing is presented. An output port assignment requires one cache memory access when the assignment is found in cache. The cache array is divided into sets that are of variable size; all entries within a set have the same prefix size. The cache is based on a ternary content addressable memory that matches ones, zeroes and don't care values. Our study shows that an associative ternary cache provides an output port at the speed of one memory access with a very high hit rate. For an 8K entry cache the hit rate ranges from 97.62 to 99.67% on traces of 0.2 to 3.5 million addresses. A port error occurs when the port selected by the cache differs from the port that would have been selected from the routing table. A sampling technique is introduced that reduces the worst port error rate by an order of magnitude (from 0.52 to 0.05%). [ABSTRACT FROM AUTHOR]

A system-on-a-chip is an interconnection of different pre-verified IP hardware blocks, which communicate using complex protocols. The integration of IP blocks requires some glue logic to interface otherwise incompatible datapaths. This glue logic is called a protocol converter and its manual design proves to be a tedious and time-consuming task. Automatic synthesis is therefore important, but for optimal system-level design it is necessary to consider not just the correctness, but also the quality (in terms of bandwidth and latency of data transfer) of the converter. A good solution to this problem will allow greater use of protocol-level abstraction as a design tool in system design and synthesis. Results are presented on automatic synthesis of a converter between two protocols. It is shown how converter logic which is bandwidth-optimal can be synthesised for datapaths with an arbitrary number of data ports each of which has arbitrary-size first-in first-out (FIFO) storage. An extension of the product FSM converter synthesis algorithm to include FIFO data-paths is presented. In addition the converter bandwidth is identified as a mean cycle graph problem which is solved using maximum mean cycle graph algorithms. [ABSTRACT FROM AUTHOR]

Focuses on the use of Internet Protocol (IP) to increase the available number of IP addresses while securing peer-to-peer communication. Advantage of Internet connectivity; Difficulties caused by limited address space in IP; Concerns on the limitation of IP addresses.

For the major signalling protocols SIP and H.323 in a multimedia communication session, the authors present a systematic method for designing gateways between call setup modes of the protocols using the supervisory control framework for nondeterministic discrete event systems. In particular, it is shown that the nonblockingness of a gateway to be designed is guaranteed by the nonblockingness of a language implementing a given specification described as specific messages. [ABSTRACT FROM AUTHOR]

TCP Vegas detects network congestion in its early stage and successfully prevents the periodic packet loss that usually occurs in traditional schemes. It has been demonstrated that TCP Vegas achieves a much higher throughput than TCP Reno. However, TCP Vegas cannot prevent unnecessary throughput degradation when congestion occurs on the backward path. A router-based congestion avoidance scheme for TCP Vegas is proposed. By distinguishing whether or not congestion occurs in the forward path, it significantly improves the connection throughput when the backward path is congested. [ABSTRACT FROM AUTHOR]

In the paper, a traffic engineering enhancement to the QoS-OSPF routing protocol is proposed and used as the path selection algorithm in a DiffServ-MPLS network. The proposed scheme, TE-QOSPF, exploits the use of non-shortest paths to improve load-balancing and avoid network congestion. Simulation results show that the algorithm outperforms the QoS-OSPF scheme in terms of loss ratio, link utilisation, and delay. [ABSTRACT FROM AUTHOR]

IP virtual private networks (IP VPNs) provide the emerging network and service opportunities for telecommunication operators such as BT. The use of intranets within businesses, coupled to the success and ubiquitous deployment of Internet and IP technologies, has generated a burgeoning demand for IP VPNs. [ABSTRACT FROM AUTHOR]

Analyzes the suitability of architectures for delivering service over Internet Protocol networks with the expected service quality and reliability. Adaption layer used by the SIGTRAN architecture; Features of the Stream Control Transmission Protocol that improve reliability without compromising performance; Performance for error checking and correct delivery of messages.

Assuming an opportunistic source selection strategy, a tight closed-form approximation for the outage probability of fixed-gain bidirectional cooperative networks is derived. The presented analysis allows for independent, reciprocal Nakagami-m fading channels with distinct fading parameters among the links. Simulation results are presented to corroborate the tightness of the proposed approximations. [ABSTRACT FROM AUTHOR]

An enhanced hybrid scheme of wavelength reservation for dynamic wavelength routed optical networks is proposed. The performance of a newly introduced composite-two-phase reservation protocol (C2P-RP) is evaluated and compared with the existing hybrid reservation protocol. By offering connection requests an enhanced scope of finding an end-to-end available wavelength, the C2P-RP scheme shows improved connection-request blocking performance. [ABSTRACT FROM AUTHOR]

Reports that fault-tolerance of session control systems based on the session initiation protocol (SIP) is achieved by multiplying session-stateful servers and by replicating their session states. Ability of replication to cause service inconsistency; Proposed update commit algorithm (UCA) for adaptive consistency control; Observation that UCA provides the user- and operator-tolerable consistency/performance trade-offs.

The article introduces various articles on communication systems, networks and digital signal processing (DSP), published in the special section. These articles were presented at the 5th International Symposium on Communication Systems, Networks and DSP. One paper discusses approximation methods for virtual partitioning for connection admission control. Another paper presents an investigation of the throughput and delay performance of the IEEE 802.11 MAC protocol.

Lee et al. recently presented a collection of n + 1 different n-party key agreement protocols based on multi-linear forms. Here we show that n - 2 of the protocols are completely insecure, being vulnerable to impersonation attacks. [ABSTRACT FROM AUTHOR]

A method is proposed for estimating the regulating time of PI-controlledAQM, which is closely related to the transient response time. It is shown that the regulating time of the PI-controlled AQM is explicitly related to its chosen parameter values and the network condition. Finally, comparisons show that the estimation is sufficiently accurate. [ABSTRACT FROM AUTHOR]

The presence of chatter in the connection management procedures of an Internet Draft transport protocol, the Datagram Congestion Control Protocol, is illustrated. Circumstances are identified in which the client and server repeatedly and needlessly exchange long sequences of packets. [ABSTRACT FROM AUTHOR]

Simulation of ETSI's High Performance Local Area Network Type 2 (HIPERLAN/2) is presented. MATLAB/Simulink modelling demonstrated that for 64-QAM mode, with coding rate 2/3, a data rate of 48 Mbit/s is achieved with 3.2 dB SNR improvement compared to coding rate 3/4 (with puncturing) as required for the maximum 54 Mbit/s. [ABSTRACT FROM AUTHOR]

Focuses on mobile Internet Protocol (IP). Fast growth of the demand for increased mobility; Means of connecting back to the home network when working outside the home environment; Way in which IP is used on a cellular system;

Focuses on the role of circuit emulation services over packet (CESoP ) in the transition to an eventual all-IP network. Ways in which CESoP complements voice over-Internet-protocol; Need for the inter-working functions to perform the packetisation process with the lowest possible delay to have any possibility of faithfully replicating a time division multiplex service across an asynchronous packet switch network; Importance of clock recovery for the high performance delivered by CESoP.

A novel technique for optimising the efficiency of route discovery is proposed. The optimisation aims to minimise the number of cached route replies, which is a significant source of overhead for the dynamic source routing protocol. Performance results show that the overall route discovery overhead can be reduced by more than 30% under high node mobility. [ABSTRACT FROM AUTHOR]

Recently Shim gave an attack on Harn's modified authenticated multiple-key agreement protocol. The authors point out Shim's attack is not workable. However, Harn's modified protocol is still insecure and the authors give another attack on it. Finally, the authors propose an efficient protocol that can prevent this attack. [ABSTRACT FROM AUTHOR]

Reports on the new version of the RF Module to Baseband Module interface specification from the Open Base Station Architecture Initiative (OBSAI) in Great Britain. Availability of the protocol to OBSAI members; Features of the new version; Statement of Peter Kenington, from the organization's technical work group, regarding the protocol.

Reports on the growth of wireless local area network connectivity in the U.S. Growth of wireless data market; Plan of McDonald's to launch its own Wi-Fi service.

Comments on issues related to Internet protocols, technology and applications in the U.S. Identification of the most exciting development of the Internet; Provision of equalitarian philosophy; Inclusion of the demands of Internet.

Shares ideas in response to the plan of Connexion Co., a division of Boeing Co., in installing its Wi-Fi equipment in a number of different airlines in Great Britain. Concept of the equipment; Usability; Advantages.

Reports on the impact of the approval of operating systems and even a TCP/IP computer network protocol stack to DO-178B Level A on the off-the-shelf software's move into safety-critical flight systems. Information on GreenHills Software; Design of the TCP/IP stack released by LynuxWorks Inc.