In optical packet/burst switching, fibre-loop optical buffers provide a compact and effective means of contention resolution. In case of fixed packet length, the involved loop length is typically chosen matched (equal to the packet length), and the loops are arranged in parallel, constituting a single-stage buffer. In this contribution, we investigate the performance of such a buffer in an asyn...

In this paper, we propose a new protection scheme, which we term partial path protection (PPP), to select endto-end backup paths using local information about network failures. PPP designates a different restoration path for every link failure on each primary path. PPP also allows reuse of operational segments of the original primary path in the protection path. A novel approach used in this pa...

In a typical wireless system, communications between a transmitter–receiver pair is subject to impairments such as intracell and intercell interference, as well as multipath fading. For practical wireless data transmission systems, e.g., UMTS or GPRS, it has been demonstrated by simulation and supported by real measurements that these impairments can be adequately modeled by hidden Markov model...

Perfect simulation, or coupling from the past, is an efficient technique for sampling the steady state of monotone discrete time Markov chains. Indeed, one only needs to consider two trajectories corresponding to minimal and maximal state in the system. We show here that even for non-monotone systems one only needs to compute two trajectories: an infimum and supremum envelope. Since the sequenc...

We consider a model of queues in discrete time, with batch services and arrivals. The case where arrival and service batches both have Bernoulli distributions corresponds to a discrete-time M/M/1 queue, and the case where both have geometric distributions has also been previously studied. We describe a common extension to a more general class where the batches are the product of a Bernoulli and...

We consider the optimal control problem of certain batch service queueing systems with compound Poisson arrivals and linear holding costs. The control problem involves the determination of the epochs at which the service is initiated as well as the sizes of the batches served. The service times are assumed to be independent and identically distributed, however, with a general distribution. A qu...

OBJECTIVES (1) To determine the pattern of ambulance arrivals in the emergency department (ED) and (2) to review resource allocation based on these data. METHODS All (13 697) ambulance arrivals in 1996 to the ED of Tan Tock Seng Hospital were studied and where relevant compared with the walk in and total arrivals of the same year. The following data were obtained from computer records: (a) pa...

Batch-wise production is found in many industries. A good example of production systems which process products batch-wise are the ovens found in aircraft industry and in semiconductor manufacturing. These systems mostly consist of multiple machines of different types, given the range and volumes of products which have to be handled. Building on earlier research in aircraft industry, where the p...

In this paper we present new analytical results concerning long-term staffing problem in high-level telecommunication service systems. We assume that a service system can be modelled either by a classic Mt/Mt/S queue, or Mt/Mt/S queue with batch service or Mt/Mt/S with catastrophes and batch arrivals when empty. The question under consideration is: how many servers guarantee that in the long ru...