Mh Barton

Ad-hoc wireless networking: contention free multiple access using token passing

Discusses mobile broadband communications with project groups such as ETSI RES 10 and ESPRIT LAURA providing much of the input. The immediate application of such systems would hope to provide high speed data links for users within a small location area and as such would have to be capable of overcoming the significant problems that the radio channel imposes. The authors discuss LANs and MAC protocols.

Ensuring interoperability in a home networking system: a case study

One of the main problems in home networked systems is the wide diversity of technologies, application requirements and cost allowance for devices and systems in general. This is translated to a division into different islands of technology that goes down to single manufacturer systems, thus blocking the way to the system integration as the main reason for the existence of the network. It is widely accepted that achieving the interworking is the most important aspect of a system specification. Object-oriented modelling associated with proper application management mechanisms for trading and binding provides the best approach to standardisation work on home systems interworking. We take here as an example the work toward an interoperability specification for an energy management system. The system described spans several communication media and brings together several consumer and producer entities. The system aims to provide increased comfort while either minimising the usage of resources or their cost for the same level of usage. Results from installed and running systems show the success of the approach.

Effectiveness of qos provided by ieee 802.11e for different traffic types

IEEE 802.11e defines Medium Access Control (MAC) enhancements for Quality of Service (QoS). The QoS is implemented using the concept of different traffic types having varying levels of service. The improved QoS for voice and video provided by 802.11e has been shown by other researchers. However, concerns on using 802.11e for data services in heavily loaded networks are pointed out in this paper. Different levels of QoS provided to the different traffic types are demonstrated through an IEEE 802.11e model using the OPNET Modeler. The simulations are done using the 802.11a PHY and with the default values of MAC access parameters defined in the IEEE 802.11e draft. The impact of the interframe spaces and contention window sizes on the performance of different traffic types is analysed. The pros and cons of 802.11e for different traffic types are presented under different network traffic loads. The inborn retransmission problem in 802.11e is also highlighted along with its effect on radio efficiency and overall system performance.

Management of services differentiation and guarantee in IEEE 802.11e wireless LANs

In this paper, we study the management and control of service differentiation and guarantee based on enhanced distributed function coordination (EDCF) in IEEE 802.11e wireless LANs. Backoff-based priority schemes are the major mechanism for quality of service (QoS) provisioning in EDCF. However, control and management of the backoff-based priority scheme are still challenging problems. We have analysed the impacts of backoff and inter-frame space (IFS) parameters of EDCF on saturation throughput and service differentiation. A centralised QoS management and control scheme is proposed. The configuration of backoff parameters and admission control are studied in the management scheme. The special role of access point (AP) and the impact of traffic load are also considered in the scheme. The backoff parameters are adaptively re-configured to increase the levels of bandwidth guarantee and fairness on sharing bandwidth. The proposed management scheme is evaluated by OPNET. Simulation results show the effectiveness of the analytical model based admission control scheme.

Toward assessing subjective quality of service of conversational mobile multimedia applications delivered over the internet: a methodology study

Some recent publications have proposed methodologies to assess the performance of multimedia services in introducing subjective estimate of the end-to-end quality of various applications. As a general statement, in order to obtain meaningful subjective results, the experiments must be repeatable and the elements of the whole chain of transmission between users must be restricted to a minimum number of objective quality metrics. This paper presents the approach to specifying the minimum quality required by the deaf when using a sign language videotelephony application over the Internet with standard off the shelf equipment.

Architecture of Achieving QoS for Multiple Flows per Node in WLANs

This paper proposes an effective architecture to achieve QoS in distributed WLANs when multiple traffic streams are present and flowing through every single station. The 802.11e standard specifies a multiple-state-machine (MSM) structure in the medium access control (MAC) to address this QoS concern. However, our research indicates that the MSM structure was suboptimal. It increases the collision rate and weakens the stability of the network. Instead, we propose a QoS scheduler over the MAC state machine (called local scheduler multi flow, LSMF): the proposed LSMF architecture prevents every flow in a node from initiating its own contention simultaneously, consequently, improves the overall network throughput and stability. We evaluate the performance of our LSMF model through mathematical analysis and simulations in comparison with the 802.11e MSM model, and prove the LSMF architecture is superior in both QoS effectiveness and flexibility for multiple flows per node case.

Key Factor and Interaction for Network Performance in Mobile Ad Hoc Networks

In this paper, we present a comprehensive statistical experiment and identify the key factors and interactions that impact network performance over mobile ad hoc networks. We use the design of experiments software named Design-Ease to establish the mathematical model for analyzing the set of simulation results from ns2. A variety of important parameters for network performance including routing protocol, node density, node speed, traffic load and pause time are considered to capture the vital factors and interactions for network performance by measuring the packet delivery ratio, average delay, discovery time and recovery time in which latter two are the crucial metrics for ad hoc self-organising performance measurement. With the simulation and analysis results, we conclude the key factors and interactions which influence the specific network performance and suggest which aspects the designers should focus on for improving the given network performance

The formalization and analysis of CCR protocol and service

Commitment, Concurrency and Recovery protocol and service defined by ISO are studied by representing them in the notation of CCS. The behaviour of the CCR protocol and service is investigated on the Concurrency Workbench, and desirable properties of CCR are expressed and analyzed in the modal mu-calculus. The formulae are checked on the Concurrency Workbench.

WIN with OSI, the sequel: A Case Study of TETRA Digital Private Mobile Radio.

The increasing deployment of computer-networking services in fixed networks motivates the provision of similar services in wireless networks. In the case of PMR systems there are already several types of data communications service (MOBITEX, MPT1327, Motorola RD-LAP for example).