Over the last decade a large number of routing protocols has been designed for achieving energy efficiency in data collecting wireless sensor networks. The drawbacks of using a static sink are well known. It has been argued in the literature that a mobile sink may improve the energy dissipation compared to a static one. Some authors focus on minimizing Emax, the maximum energy dissipation of any single node in the network, while others aim at minimizing Ebar, the average energy dissipation over all nodes. In our paper we take a more holistic view, considering both Emax and Ebar. The main contribution of this paper is to provide a simulation-based analysis of the energy efficiency of WSNs with static and mobile sinks. The focus is on two important configuration parameters: mobility path of the sink and duty cycling value of the nodes. On the one hand, it is well known that in the case of a mobile sink with fixed trajectory the choice of the mobility path influences energy efficiency. On the other hand, in some types of applications sensor nodes spend a rather large fraction of their total lifetime in idle mode, and therefore higher energy efficiency can be achieved by using the concept of reduced duty cycles. In particular, we quantitatively analyze the influence of duty cycling and the mobility radius of the sink as well as their interrelationship in terms of energy consumption for a well-defined model scenario. The analysis starts from general load considerations and is refined into a geometrical model. This model is validated by simulations which are more realistic in terms of duty cycling than previous work. It is illustrated that over all possible configuration scenarios in terms of duty cycle and mobility radius of the sink the energy dissipation in the WSN can vary up to a factor of nine in terms of Emax and up to a factor of 17 in terms of Ebar. It turns out that in general the choice of the duty cycle value is more important for achieving energy efficiency than the choice of the mobility radius of the sink. Moreover, for small values of the duty cycle, a static sink turns out to be optimal in terms of both Emax and Ebar. For larger values of the duty cycle, a mobile sink has advantages over a static sink, especially in terms of Emax. These insights into the basic interrelationship between duty cycle value and mobility radius of a mobile sink are relevant for energy efficient operation of homogeneous WSNs beyond our model scenario.

Two recent trends are major motivators for service component migration: the upcoming use of cloud-based services and the increasing number of mobile users accessing Internet-based services via wireless networks. While cloud-based services target the vision of Software as a Service, where services are ubiquitously available, mobile use leads to varying connectivity properties. In spite of temporary weak connections and even disconnections, services should remain operational. This paper investigates service component migration between the mobile client and the infrastructure-based cloud as a means to avoid service failures and improve service performance. Hereby, migration decisions are controlled by policies. To investigate component migration performance, an analytical Markov model is introduced. The proposed model uses a two-phased approach to compute the probability to finish within a deadline for a given reconfiguration policy. The model itself can be used to determine the optimal policy and to quantify the gain that is obtained via reconfiguration. Numerical results from the analytic model show the benefit of reconfigurations and the impact of different reconfigurations applied to three service types, as immediate reconfigurations are in many cases not optimal, a threshold on time before reconfiguration can take place is introduced to control reconfiguration.

A three-tier information management architecture for mobile grid environments and ad-hoc networks is presented in this paper. We address a key challenge in such highly dynamic environments with a high degree of fluctuation in the hardware infrastructure: how to store information consistently, persistently, and at the same time efficiently. Most currently available approaches are based on replication strategies. These strategies achieve persistency even in highly dynamic environments, but have to pay a high price in terms of redundancy. Our proposed architecture is based on the adaptation of fault-tolerant data distribution strategies utilizing erasure codes, such as RAID or Reed-Solomon, and thus combines consistency and persistency with high storage efficiency.

Congestion in wireless sensor networks leads to the degradation of communication links that result in decreased throughput and waste of energy which is one of the scarcest resources of a sensor node. Various techniques have been proposed to cope with data congestion, such as data aggregation techniques, multi hop routing techniques and flow control techniques. Although these techniques help to avoid or control congestion, they do not address the issue of data persistency effectively. This paper presents an adaptive self configuring in-network storage model for data persistency in wireless sensor networks. The model is built on a clustered sensor field where we have utilized dense node deployment in the vicinity of the routing nodes to act as data buffers during congestion periods in order to avoid data loss. We show that the in-network storage model can be used in combination with congestion avoidance/control techniques to develop data persistent congestion avoidance/control strategies

We propose and analyse an extension of the concept of RSVP to guarantee the service quality of mobile Internet-based applications. Our Mobile RSVP protocol provides an advanced resource reservation mechanism in a wireless cellular environment. Furthermore, we propose the dynamic resource sharing algorithm to make better use of network resources in those cells, where advance reservation takes place. We analyse our proposed protocol and the corresponding dynamic resource sharing algorithm by simulating the behaviour of distinct call types in a single cell. We also investigate the effect of user mobility behaviour on the performance of future resource reservation protocols with mobility support. By analysing the pattern of user mobility as well as possible application priorities, we hope to be able to put constraints to the scope of service provision.

We propose and analyze an extension of the concept of RSVP to guarantee the service quality of mobile Internet-based applications. Our Mobile RSVP protocol provides an advanced resource reservation mechanism in a wireless cellular environment. Furthermore, we propose the dynamic resource sharing algorithm to make better use of network resources in those cells, where advance reservation takes place. We analyze our proposed protocol and the corresponding dynamic resource sharing algorithm by simulating the behavior of distinct call types in a single cell. We also investigate the effect of user mobility behavior on the performance of future resource reservation protocols with mobility support. By analyzing the pattern of user mobility as well as possible application priorities, we hope to be able to put constraints to the scope of service provision.

Any performance evaluation study requires a concise description of the workload under which the performance of the system is to be evaluated. Also, the repeatability of the experiments for different workload profiles, requires that the workload models generate the workload profiles parametrically. Such a model, should preferably be time-invariant, consistent and generative. We view the networkload as a sequence that can be generated from the rules of a Context Free Grammar (CFG). Our approach combines the established practice of viewing the workload as “consisting of a hierarchy” and the CFG description, to produce a generative networkload model. The networkload model is applied to a SingleServer-MultipleClients network by deriving the networkload model parameters from an operational SingleServer network of personal computers. The time-invariance and generative nature are verified experimentally. The usefulness of such a description of the networkload to study the resource management problems of a network, like the optimal allocation of clients to servers, is explored by using the generative model as input descriptor to a queueing network model of SingleServer network.

This paper describes the general methodology of specifying parallel systems within the PAPS (Performance Analysis of Parallel Systems) toolset and presents a case study that shows the applicability and accuracy of the Petri net based performance prediction tools contained in the toolset. Parallel systems are specified in the PAPS toolset by separately defining the program workload, the hardware resources, and the mapping of the program to the hardware. The resource parameterization is described in detail for a multiprocessor computer with a store & forward communication network. The Gaussian elimination algorithm is taken as a workload example to demonstrate how regularly structured parallel algorithms are modelled with acyclic task graphs. Three different program specifications with various levels of model accuracy are developed and their parameterization is described. The predicted execution time is compared with the measured execution times of the real program on the parallel hardware. It is shown that the Petri net based performance prediction tools provide accurate performance predicitons.

Abstract The paper deals with strategies to implement comfort classes and with fixed optimization criteria.

Abstract This paper gives a survey of methods used for the realization of extended control structures, FORTRAN is taken as an example language. A proposal is made whose concept is to extend a language dynamically by control structures which are composed from elements of an extendable set of structural components.

A new computer system is required to replace the existing UNIVAC 494 system for the universities at Graz. A synthetic jobstream matching the real batch load of the existing system was constructed using Buchholz's job (which was modified and transferred to FORTRAN). This synthetic jobstream was used for comparison of different computer systems as well as for the selection evaluation process itself. The construction of this synthetic jobstream is described in detail in this paper. The problems of characterising the real load are discussed explicitly. Special attention was given to the question of which parameters should be used, together with the decisions on the form of the scale and the sub-division of the range of the parameter values. Furthermore a procedure is given for an optimum of determination of the parameter values of the synthetic jobstream.