380 research outputs found
An efficient data transmission policy in an integrated voice-data ds-cdma network
CDMA schemes appear to be promising access techniques for coping with the requirements of third-generation mobile systems, mainly because of their flexibility. This paper proposes an adaptive S-ALOHA DS-CDMA access scheme as a method for integrating non-real time (i.e. Internet applications) and real-time (i.e. voice) services, by exploiting the potentials of CDMA under time-varying conditions. The adaptive component terminals autonomously change their transmission rate according to the total (voice+data) channel occupancy, so that the minimum possible data delay is almost always achieved.Peer ReviewedPostprint (published version
Multiple Access Protocols for Data Communications via VSAT Networks
One of the most significant advantages of VSAT Networks is the ability to link together many terminals at remote sites under a single manageable network and to adapt the performance characteristics of the network to the requirements of the type of data traffic presented to the network
Interference Calculation in Asynchronous Random Access Protocols using Diversity
The use of Aloha-based Random Access protocols is interesting when channel
sensing is either not possible or not convenient and the traffic from terminals
is unpredictable and sporadic. In this paper an analytic model for packet
interference calculation in asynchronous Random Access protocols using
diversity is presented. The aim is to provide a tool that avoids time-consuming
simulations to evaluate packet loss and throughput in case decodability is
still possible when a certain interference threshold is not exceeded. Moreover
the same model represents the groundbase for further studies in which iterative
Interference Cancellation is applied to received frames.Comment: This paper has been accepted for publication in the Springer's
Telecommunication Systems journal. The final publication will be made
available at Springer. Please refer to that version when citing this paper;
Springer Telecommunication Systems, 201
Future benefits and applications of intelligent on-board processing to VSAT services
The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
Can Multiple Subchannels Improve the Delay Performance of RTS/CTS-based MAC Schemes?
We analyze the delay performance of RTS/CTSbased
(Request-To-Send/Clear-To-Send) multi-channel MAC
(Medium Access Control) schemes for wireless networks. These
schemes usually employ multiple data subchannels for data
transmission and one control subchannel to send the RTS/CTS
dialogue for channel reservation. Through theoretical analysis
and simulations, we show that, in fully-connected networks, such
multi-channel MAC schemes suffer longer delays than the corresponding
single channel MAC scheme, that puts the RTS/CTS
dialogue on the same channel as data packet transmissions. This
conclusion holds even when data packets have different priorities
and higher priority traffic is sent ahead of lower priority traffic
MSAT-X: A technical introduction and status report
A technical introduction and status report for the Mobile Satellite Experiment (MSAT-X) program is presented. The concepts of a Mobile Satellite System (MSS) and its unique challenges are introduced. MSAT-X's role and objectives are delineated with focus on its achievements. An outline of MSS design philosophy is followed by a presentation and analysis of the MSAT-X results, which are cast in a broader context of an MSS. The current phase of MSAT-X has focused notably on the ground segment of MSS. The accomplishments in the four critical technology areas of vehicle antennas, modem and mobile terminal design, speech coding, and networking are presented. A concise evolutionary trace is incorporated in each area to elucidate the rationale leading to the current design choices. The findings in the area of propagation channel modeling are also summarized and their impact on system design discussed. To facilitate the assessment of the MSAT-X results, technology and subsystem recommendations are also included and integrated with a quantitative first-generation MSS design
- …