1,720,998 research outputs found
Stability analysis of an adaptive packet access scheme for mobile communication systems with high propagation delays
No full textIn this paper, we investigate a packet access scheme that is able to support mixed traffics in the presence of high propagation delays. Referring to a Time-Code Division Multiple Access air interface, we propose a Medium Access Control (MAC) protocol based on a random access scheme. A successful attempt grants the use of a slot-code resource. This protocol is named Adaptive Time Code-Packet Reservation Multiple Access (ATC-PRMA), since the access parameters are changed, depending on the traffic load conditions, so as to fulfil Quality of Service requirements. Numerical examples are carried out for the Low Earth Orbit (LEO)-Mobile Satellite System (MSS) scenario, but all these considerations could be applied to High-Altitude Platform Stations (HAPSs) as well. In both cases, high propagation delays prevent an immediate feedback to users. An analytical approach is proposed to study the stability of our MAC scheme. Accordingly, we define a criterion for optimizing system performance. The predicted ATC-PRMA behaviour is supported by simulation results. Finally, we show the performance improvement of ATC-PRMA with respect to a MAC protocol not employing adaptive parameters
Stability analysis of an access scheme for mixed traffics in LEO and MEO systems
No full textThis paper deals with the stability analysis of a packet access scheme able to support efficiently three traffic classes (voice, Web interactive and short messaging) in LEO and MEO mobile satellite systems. This study permits to select optimized permission probability values; accordingly, our access scheme has been named Optimized Packet Reservation Multiple Access (O-PRMA). Its good performance has been also shown in the presence of a GOOD-BAD channel model
Maximal Independent, Analytic Sets In Abelian Polish Groups
No full textThe paper deals with the questions:
(a) whether a topological module admits maximal linearly independent subsets
that are analytic;
(b) whether an Abelian topological group admits maximal independent subsets
that are analytic;
(c) whether a topological field extension admits transcendence bases that are
analytic
Energy-efficient packet access scheme for MF-TDMA in non-GEO satellite systems
No full textThis paper deals with the proposal of an access protocol for the MF-TDMA air interface (i.e., resources in the time-frequency domain) to support multiple packet traffic classes in LEO and MEO satellite systems. A random access phase based on a persistency probability is adopted for each traffic class to gain the reservation of resources. We propose an optimization process for our packet access scheme where control parameters are selected to save the energy of the terminals. Comparisons with an energy-unaware access scheme has permitted to highlight that our protocol entails a significant reduction of energy consumption, accepting a small performance degradation. This work has been carried out within both the SHINES Project (Prin 2002) and the SatNex Network of Excellence (n. 507052)
A novel approach for optimizing packet access schemes in non-geostationary satellite systems
No full textThis paper deals with an optimized packet access scheme depending on traffic load conditions that is able to support efficiently three traffic classes (voice, Web interactive and short messages) in non-geostationary mobile satellite systems. We adopt the equilibrium point analysis in order to study the stability of our scheme. This allows identifying optimal values for the protocol control parameters. Extensive comparisons have been performed with other techniques in the literature showing the good results achieved by our protocol
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