This paper studies an M/G/1 queue where the idle time of the server is utilized for additional work in a secondary system. As usual, the server is busy as long as there are units in the main system. However, as soon as the server becomes idle he leaves for a “vacation.” The duration of a vacation is a random variable with a known distribution function. Two models are considered. In the first, upon termination of a vacation the server returns to the main queue and begins to serve those units, if any, that have arrived during the vacation. If no units have arrived the server waits for the first arrival when an ordinary M/G/1 busy period is initiated. In the second model if the server finds the system empty at the end of a vacation, he immediately takes another vacation, etc. For both models Laplace-Stieltjes transforms of the occupation period, vacation period and waiting time are derived and generating functions of the number of units in the system are calculated. The two models are then compared to each other, and for some special cases the optimal mean vacation times are found.
This paper explores the use of replicated databases for management of customer data (e.g., mobility data, call routing logic) in global, intelligent and wireless networks. We propose and analyze two, full and partial, data replication schemes -which are compatible with industry protocol standards -and compare them with the traditional, centralized database scheme. By identifying a set of key teletraffic and mobility parameters, we develop a modeling framework based on queueing models, and apply it to assess the relative performance and merits of these schemes.Our results reveal that the full replication scheme outperforms the centralized one over a range of parameters. Furthermore, if customers update some of their data frequently (such as location data for highly mobile customers in wireless networks) and each call launches multiple queries into the databases, the partial replication scheme offers further performance improvement.unique personal telephone number (referred to as Personal Telecommunication Number, PTN) on any fixed or mobile terminal, irrespective of its geographical location throughout the world. Calls destined for a PTN can be routed to the customer's home, office, car, or answering service according to the routing logic specified by the customer. Such personal mobility is the defining attribute of the UPT service [FW92]. In order for the network to support the service, it has to rely on the extensive use of databases for call routing and other signaling functions. It is worth noting that each of the originating and receiving ends of a UPT call can be a wireless or wired terminal.Our focus here is to consider such mobility services across multiple, international networks. To make our ideas concrete, we assume in this paper that global customers are based in the U.S. and possibly traveling in a foreign country. A centralized design, where the customer location information is stored in a centralized database physically located in the U.S, is shown in Figure 1. In order to make this design feasible, it requires that customers traveling abroad register from the visited country so that their home network is informed of their current locations (e.g., in terms of POTS numbers in wired networks, or network identity and temporary numbers in wireless networks). In addition, every time a customer changes location, the location data for the customer in the database is updated. Such database updates can be initiated: a) explicitly by customers connected to a wired network, as similar to the current AT&T 500 services, or b) automatically by the wireless network at which the customers are located. When a call is destined for a customer located either in the U.S. or abroad, the signaling network queries the centralized database for the location information for call setup and other signaling functions. Figure 1: Centralized Database ArchitectureThe centralized database architecture can be generalized into a distributed database design. In this distributed design, customer records are partitioned and stored (but n...
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