64,734 research outputs found
QoS in LEO satellite networks with multipacket reception
Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaLow Earth Orbit (LEO) satellite networks can improve terrestrial wireless networks to
allow global broadband services for Mobile Terminals (MT), regardless of the users' location.
In this context, hybrid telecommunication systems combining satellites with Long
Term Evolution (LTE) networks, like the LightSquared technology, are intended to provide
ubiquitous high-speed services.
This dissertation analyses the performance of a random access protocol that uses Hybrid
Network-assisted Diversity Multiple Access (H-NDMA), for a LEO satellite system
network, named by Satellite Random NDMA (SR-NDMA). The protocol also considers
a Single Carrier-Frequency Domain Equalization (SC-FDE) scheme for the uplink transmission
and a Multipacket Reception (MPR) receiver. In this scenario, the transmission
of data packets between MTs and the Base Station (BS) is made through random access
and schedule access slots, organized into super-frames with the duration of a Round Trip
Time (RTT).
A SR-NDMA simulator is implemented to measure the system performance in matters
of throughput, energy consumption, system delay and also the protocol capacity to
meet Quality of Service (QoS) requirements. A set of simulations tests were made with a
random Poisson process tra c generation to validate the analytical model. The capacity
to ful l the QoS requirements of a real-time tra c class was also tested.FCT/MEC: MPSat - PTDC/EEA-TEL/099074/2008,
OPPORTUNISTIC CR - PTDC/EEA-TEL/115981/2009, Femtocells - PTDC/EEA-TEL/120666/2010
e ADIN - PTDC/EEI-TEL/2990/201
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
An Overview and Examination of the Indian Services Sector
India’s service sector has grown rapidly since the 1990s. Domestic demand for services has increased as incomes have risen, triggering the expansion of industries such as banking, education, and telecommunications. Exports have also increased rapidly, led by information technology and business process outsourcing (IT-BPO). India’s ability to offer low-cost, high-quality IT-BPO services has made it a world leader in this industry. However, employment in services has not grown as quickly as output. The majority of India’s jobseekers are low-skilled, but demand for workers is growing fastest in higher-skill industries. The supply of highly-skilled workers has not kept pace with demand, causing wages to increase faster for these workers than for lower-skilled ones.
India’s government has supported the growth of service industries through a mix of deregulation, liberalization, and incentive programs, such as the Software Technology Parks of India. Nevertheless, burdensome regulations, poor infrastructure, and foreign investment restrictions continue to affect service firms’ ability to do business. USITC analysis suggests that additional liberalization would lead to an increase in India’s imports of services
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