1,721,156 research outputs found
Limiting removal depth in the pushout scheme for ATM networks
No full textThe asynchronous transfer mode (ATM) handles cells of different classes in various ways to provide the different services with their respective quality of service requirements. To decrease the loss probability of high priority cells at the expense of cells with lower priorities, two loss priority schemes have been proposed in the literature: capped threshold and push out. Since throughput is slightly greater in the push out scheme while buffer management complexity increases when passing from threshold to push out, it seems natural to prefer the threshold scheme. A limitation of the removal depth in the push out scheme, called L push out, is proposed. The most attractive feature in limiting push out is the decrease of buffer management complexity, since only a small part of the buffer seems to be necessary to reach both loss rates (those of both the low and the high priority class) using the push out strategy. Approximation analysis was used for random traffic and simulations for bursty traffi
Performance of a reversible hierarchical cellular system
No full textIn order to provide mobile worldwidecommunication services, cellular systems can be based ona multilayered, multisized cells architecturecharacterized by the use of different technologies.Satellites can cover lightly populated areas, as well asthose areas where other means cannot be used (like thesea); fixed base stations, with different transmissionpowers and thus different cell sizes, can cover relatively highly populated areas. As a result,a given area could simultaneously be served by more thanone Base Station, and the structure of such a systemmust be carefully designed. A Hierarchical Architecture(HA) scheme is a possible solution. HA is based on amultilevel cell configuration: microcells (or evenindoor picocells) cover more densely populated areas andare given the majority of the traffic load as they are able to operate with very highcapacity, while overlaying macrocells (or satellitarcells) provide a group of overflow channels.Occasionally, when microcells are not able to satisfychannel requests, the overflow channels are consumed.HA schemes are divided in two categories: ReversibleHierarchical (RH) and Non Reversible (NRH). Thedifference is given by the handover directions between cells allowed. In a RH handover, attemptsbetween macrocells and microcells occur in bothdirections. This paper compares RH and NRH schemes bymeans of an analytical model based on birth-deathprocesses. The main performance indexes and the controloverhead are shown
Performance of queuing priority schemes based on push-out mechanism in mobile cellular systems
No full textA modified fast buffer reservation algorithm (M-FBR) for congestion control in ATM networks
No full textA reversible hierarchical scheme for microcellular systems with overlaying macrocells
No full textFuture cellular systems are expected to use multilayered, multisized cells to cover non-homogeneous populated areas. An example in literature is given by a 2 level hierarchical architecture in which an overlaying macrocell provides a group of overflow channels utilized when a microcell, which covers a densely populated area, is not able to accommodate a new call, or a handover from another microcell. The macrocell has the higher hierarchical position, meaning that it can receive handover requests from microcells, lower in the hierarchy, as well as from other macrocells. On the contrary, a call served by the macrocell cannot handover to a microcell. This paper proposes a reversible hierarchical scheme characterized by the presence of handover attempts from macrocells to microcells. The scheme is conceived so that the microcells are given the majority of the traffic load as they are able to operate with very high capacity, while the macrocells, having lower channel utilization, can better carry out their support task. An analytical study is carried out showing that the system performance can be improved, at the expense of relatively little increase of network control overhead, when compared with the classical, i.e. nonreversible hierarchical schem
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