On Channel Sharing Policies in LEO Mobile Satellite Systems

We consider a low earth orbit (LEO) mobile satellite system with "satellite-fixed" cells that accommodates new and handover calls of different service-classes. We provide an analytical framework for the efficient calculation of call blocking and handover failure probabilities under two channel sharing policies, namely the fixed channel reservation and the threshold call admission policies. Simulation results verify the accuracy of the proposed formulas. Furthermore, we discuss the applicability of the policies in software-defined LEO satellites

Journal of Telecommunications and Information Technology, 2018, nr 1

We consider a two-link system that accommodates Poisson arriving calls from different service-classes and propose a multirate teletraffic loss model for its analysis. Each link has two thresholds, which refer to the number of in-service calls in the link. The lowest threshold, named support threshold, defines up to which point the link can support calls offloaded from the other link. The highest threshold, named offloading threshold, defines the point where the link starts offloading calls to the other link. The adopted bandwidth sharing policy is the complete sharing policy, in which a call can be accepted in a link if there exist enough available bandwidth units. The model does not have a product form solution for the steady state probabilities. However, we propose approximate formulas, based on a convolution algorithm, for the calculation of call blocking probabilities. The accuracy of the formulas is verified through simulation and found to be quite satisfactory

Proceedings of the Fifth International Mobile Satellite Conference 1997

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments

Journal of Telecommunications and Information Technology, 2018, nr 1

kwartalni

SIMULATION OF A MULTIPROCESSOR COMPUTER SYSTEM

The introduction of computers and software engineering in telephone switching systems has dictated the need for powerful design aids for such complex systems. Among these design aids simulators - real-time environment simulators and flat-level simulators - have been found particularly useful in stored program controlled switching systems design and evaluation. However, both types of simulators suffer from certain disadvantages. An alternative methodology to the simulation of stored program controlled switching systems is proposed in this research. The methodology is based on the development of a process-based multilevel hierarchically structured software simulator. This methodology eliminates the disadvantages of environment and flat-level simulators. It enables the modelling of the system in a 1 to 1 transformation process retaining the sub-systems interfaces and, hence, making it easier to see the resemblance between the model and modelled system and to incorporate design modifications and/or additions in the simulator. This methodology has been applied in building a simulation package for the System X family of exchanges. The Processor Utility Sub-system used to control the exchanges is first simulated, verified and validated. The application sub-systems models are then added one level higher_, resulting in an open-ended simulator having sub-systems models at different levels of detail and capable of simulating any member of the System X family of exchanges. The viability of the methodology is demonstrated by conducting experiments to tune the real-time operating system and by simulating a particular exchange - The Digital Main Network Switching Centre - in order to determine its performance characteristics.The General Electric Company Ltd, GEC Hirst Research Cent, Wemble

Spectrum Rights in the Telecosm to Come

The spectrum of electromagnetic frequencies impact the way individuals and society communicate. The discussion involves reforming the structures governing the spectrum, a debate that centers on the benefits of public versus private control over the resources. This article focuses on articulating governmental standards for managing and regulating public or private control of the spectrum. However, standards will not be easy to establish given the difficult cost assessments necessary to balance the public interest against communication. A regulatory agency can better govern spectrum management that accommodates both commonly and privately owned spectrum. Spectrum conflicts can be remedied easily by defining a class of per se nuisances. The article concludes by encouraging attentiveness to the costs of dispute resolution, the regulators? roles in reducing these costs, and the policy choices inherent in spectrum management. Any regulator agency that is established must play a role in resolving spectrum conflicts

Mau Mau crucible of war: Statehood, national identity and politics in postcolonial Kenya

The postcolonial African state has been the subject of extensive study and scrutiny by various scholars of great repute such as Colin Legum, Crawford Young, Robert H. Jackson and Carl G. Rosberg, Pierre Englebert and Jean-Francois Bayart to name but a few. Crawford Young\u27s work is especially interesting because of the manner in which he treats the process of state formation. Crawford Young traces the process to the early beginning of European colonization and focuses on the legacy of the colonial state after independence. Colonial appendages of old European states were, for some metropolises, no longer economically viable or sustainable and/or consistent with new post-world War I and II principles such as the right of all peoples to self-determination and decolonization, and were, thus, abandoned. Overall, however, perhaps because of the simplicity of the process of state formation in Africa through European agency, the everyday realities of the nature of the African state and lived experiences remain rather elusive still. Nevertheless, this body of work that has benefitted disproportionately from the contribution of political scientists cannot be underestimated. At the same time though, the manner in which this process has been approached by such authors employs methodological perspectives in political science that overlook or undermine attempts at determining the manner in which the making, or unmaking, and evolution of post-colonial African states is viewed and contested from below. Historians employing empirical information based on archival evidence can make such a bottom-up analysis that is cognizant of popular views or dissent affecting the political evolution of these states possible. While there have been a few country-specific studies, there\u27s room for more scrutiny of how African states have evolved since independence paying closer attention to popular forces from below. This study demonstrates that the late colonial experience in Kenya was the foetal crucible of the postcolonial state. It does this with specific reference to the Mau Mau war. This follows from the argument that the Mau Mau decade was Kenya\u27s defining moment marked by widespread societal rupture embodied by the Mau Mau conflict. This war represented a caesura in which Kenya\u27s future was contested between competing imperial and indigenous ideological constructions of the state: colonial liberal and conservative, and indigenous dissent borne of an existential struggle for survival. The study examines these ideological strands, but focuses more acutely on the basic convictions and moral thought or subliminal ideology of Mau Mau while, at the same time, touching on both its immediate and long-term practical (land, labour, institutional and political) policy implications. Lastly, it is an analytical catalogue of the legacy of Mau Mau dissent in post-independent Kenya. As such, it is an analysis of its bequest to the present and, thus, considers the war as an unresolved philosophical conflict. By so doing, this study suggests a lineage of political demands or grievance and socioeconomic struggle in Kenya today couched on the basic need for survival, which harks back to the Mau Mau political dissent and war