A mobility-transparent deterministic broadcast mechanism for ad hocnetworks

Broadcast (distributing a message from a source node to all other nodes) is a fundamental problem in distributed computing. Several solutions for solving this problem in mobile wireless networks are available, in which mobility is dealt with either by the use of randomized retransmissions or, in the case of deterministic delivery protocols, by using conflict-free transmission schedules. Randomized solutions can be used only when unbounded delays can be tolerated. Deterministic conflict-free solutions require schedule recomputation when topology changes, thus becoming unstable when the topology rate of change exceeds the schedule recomputation rate. The deterministic broadcast protocols we introduce in this paper overcome the above limitations by using a novel mobility-transparent schedule, thus providing a delivery (time) guarantee without the need to recompute the schedules when topology changes. We show that the proposed protocol is simple and easy to implement, and that it is optimal in networks in which assumptions on the maximum number of the neighbors of a node can be made     

Resource assignment for integrated services in wireless ATM networks

The task of supporting integrated multirate multimedia traffic in a bandwidth-poor wireless environment poses a significant challenge for network designers. In this paper we propose a novel bandwidth allocation strategy which partitions the available bandwidth amongst the different traffic classes in a manner that ensures quality-of-service guarantees for digital video while minimizing the maximum blocking probability for voice and data connections. At the connection level, near-optimum utilization of the reserved bandwidth for video traffic is achieved through an intra-frame statistical multiplexing algorithm, while at the system level the delicate task of partitioning the bandwidth between voice, video and data is accomplished by developing an efficient algorithm which uses traffic parameters consisting only of the aggregate traffic load and the total available bandwidth. The algorithm, built on non-trivial mathematical results is robust, easy to implement and has a geometric rate of convergence which ensures that the partitioning points are found quickly. These properties make it well suited for practical implementations, even for cases where changes in the aggregate traffic loads cause bandwidth allocations to be recomputed frequently. © 1998 John Wiley & Sons, Ltd.     

Analytical generalized results for handoff probability in wirelessnetworks

We present analytical results for handoff probability for wireless networks under assumption that the call holding time and the cell residence time are all generally distributed. Easily computable formulas can be obtained for cases when the call holding time and cell residence time have rational Laplace transforms     

Call Blocking Performance Study for PCS Networks under More Realistic Mobility Assumptions

In the micro-cell-based PCS networks, due to the high user mobility, handoffs occur more frequently. Hence, the classical assumptions, such as the exponential assumptions for channel holding time and call inter-arrival time, may not be valid. In this paper, we investigate the call blocking performance for PCS networks using a semi-analytic and semi-simulation approach. We first construct a simulation model as the base for our performance study, using which the handoff traffic is studied. Then we present a few possible approximation models from which analytical results for call blocking performance metrics can be obtained and compared with the simulation results. We show that for a certain parameter range, such approximations may provide appropriate results for call blocking performance. Finally, using the simulation model, we investigate how various factors, such as the high moments, the variance of cell residence time, mobility factors and the new call traffic load affect the call blocking performance. Our study shows that all these factors may have a significant impact on call blocking performance metrics such as call blocking probability, call incompletion probability and call dropping probability. This research provides a strong motivation for the necessity of reexamining the validity of analytical results obtained from classical teletraffic theory when dealing with the emerging wireless systems.     

An Energy-Efficient Method for Nodes Assignment in Cluster-Based Ad Hoc Networks

One of the most critical issues in wireless ad hoc networks is represented by the limited availability of energy within network nodes. Thus, making good use of energy is a must in ad hoc networks. In this paper, we define as network lifetime the time period from the instant when the network starts functioning to the instant when the first network node runs out of energy. Our objective is to devise techniques to maximize the network lifetime in the case of cluster-based systems, which represent a significant sub-set of ad hoc networks. Cluster-based ad hoc networks comprise two types of nodes: cluster-heads and ordinary nodes. Cluster-heads coordinate all transmissions from/to ordinary nodes and forward all traffic in a cluster, either to other nodes in the cluster or to other cluster-heads. In this case, to prolong the network lifetime we must maximize the lifetime of the cluster-heads because they are the critical network element from the energy viewpoint. We propose an original approach to maximize the network lifetime by determining the optimal assignment of nodes to cluster-heads. Given the number of cluster-heads, the complexity of the proposed solution grows linearly with the number of network nodes. The network topology is assumed to be either static or slowly changing. Two working scenarios are considered. In the former, the optimal network configuration from the energy viewpoint is computed only once; in the latter, the network configuration can be periodically updated to adapt to the evolution of the cluster-heads energy status. In both scenarios, the presented solution greatly outperforms the standard assignment of nodes to cluster-heads, based on the minimum transmission power criterion.     

Internet of things: Vision,applications and research challenges

The term “Internet-of-Things” is used as an umbrella keyword for covering various aspects related to the extension of the Internet and the Web into the physical realm, by means of the widespread deployment of spatially distributed devices with embedded identification, sensing and/or actuation capabilities. Internet-of-Things envisions a future in which digital and physical entities can be linked, by means of appropriate information and communication technologies, to enable a whole new class of applications and services. In this article, we present a survey of technologies, applications and research challenges for Internet-of-Things.     

Effects of Erlang call holding times on PCS call completion

This paper studies personal communications services (PCSs) channel allocation assuming the Erlang call holding time distribution (a generalization of the exponential distribution) to investigate the effect of the variance of the call holding times on the call completion probability. Our analysis indicates that the call completion probability decreases as the variance of the call holding times decreases. This effect becomes more pronounced as the variance of the cell residence times decreases     

Teletraffic analysis and mobility modeling of PCS networks

Channel holding time is of primary importance in teletraffic analysis of PCS networks. This quantity depends on user's mobility which can be characterized by the cell residence time. We show that when the cell residence time is not exponentially distributed, the channel holding time is not exponentially distributed either, a fact also confirmed by available field data. In order to capture the essence of PCS network behaviour, including the characterization of channel holding time, a correct mobility model is therefore necessary. The new model must be good enough to fit field data, while at the same time resulting in a tractable queueing system. We propose a new mobility model, called the hyper-Erlang distribution model, which is consistent with these requirements. Under the new realistic operational assumption of this model, in which the cell residence time is generally distributed, we derive analytical results for the channel holding time distribution, which are readily applicable to the hyper-Erlang distribution models. Using the derived analytical results we demonstrate how the distribution of the cell residence time affects the channel holding time distribution. The results presented in this paper can provide guidelines for field data processing in PCS network design and performance evaluation     

A Multiaccess Protocol for Multihop Radio Networks

We describe an adaptive multiaccess channel protocol for use in radio networks with an arbitrary distribution of stationary hidden nodes, which provides the nodes with controlled, collision-free access to the channel. The protocol can be considered to belong to the BRAM [5] protocol family, but differs in significant ways from BRAM. In this paper we describe the tenets of the protocol, then develop the protocol, and finally develop analytic expressions for its expected throughput and delay performance. Given these delay-throughput expressions, we show how protocol "delay" optimization can be achieved by dynamic adjustment of a protocol parameter as the network traffic load changes.     

A linear solution to queueing analysis of synchronous finite buffernetworks

An approximate solution to slotted communication systems with finite population and finite buffer capacity is presented. The authors assume symmetric systems and present for the first time a linear solution involving linear equations whose number is a linear function of the total buffer capacity. They show that the model can be applied to existing multiaccess channel protocols in which a single successful transmission can be affected per slot. They further show that, unlike solutions based on existing nonlinear models, the proposed solution can be extended to communication systems in which several successful transmissions can take place in parallel, such as multibus communication networks and multichannel satellite systems