752 research outputs found
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Snoop behaviour in multihop wireless networks
"© ACM, 2011. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in Proceedings of the Fifth ACM International Workshop on Performance Monitoring, measurement and Evaluation of heterogeneous wireless and wired networks 2011 http://doi.acm.org/10.1145/1868612.1868623"Snoop is one proposal for improving TCP throughput in wireless networks. We investigated the application of this protocol in wireless ad hoc networks and observed that a single hop in the ad hoc network experienced large variations in round trip time in a very short period. Without changes to the Snoop protocol to accommodate these dramatic RTT variations, Snoop was performing badly compared with regular TCP even when there were no packet losses or errors. The main cause for poor performance premature retransmissions performed by Snoop. We have modified the Snoop protocol to avoid these unnecessary retransmissions by having a higher local retransmission timeout. The results show us that Snoop benefits from this approach which has made a significant performance improvement over regular TCP in multihop wireless network
Will TCP work in mmWave 5G Cellular Networks?
The vast available spectrum in the millimeter wave (mmWave) bands offers the
possibility of multi-Gbps data rates for fifth generation (5G) cellular
networks. However, mmWave capacity can be highly intermittent due to the
vulnerability of mmWave signals to blockages and delays in directional
searching. Such highly variable links present unique challenges for adaptive
control mechanisms in transport layer protocols and end-to-end applications.
This paper considers the fundamental question of whether TCP - the most widely
used transport protocol - will work in mmWave cellular systems. The paper
provides a comprehensive simulation study of TCP considering various factors
such as the congestion control algorithm, including the recently proposed TCP
BBR, edge vs. remote servers, handover and multi- connectivity, TCP packet size
and 3GPP-stack parameters. We show that the performance of TCP on mmWave links
is highly dependent on different combinations of these parameters, and identify
the open challenges in this area.Comment: 7 pages, 4 figures, 2 tables. To be published in the IEEE
Communication Magazin
Quality of service optimization of multimedia traffic in mobile networks
Mobile communication systems have continued to evolve beyond the currently deployed Third
Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G
are expected to cater for a wide variety of services such as speech, data, image transmission,
video, as well as multimedia services consisting of a combination of these. With the air interface
being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed
Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of
3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features
such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions
in the base stations, necessitating buffering of data at the air interface which presents a
bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of
Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient
buffer management schemes are required at the air interface.
The main objective of this thesis is to propose and evaluate solutions that will address the
QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the
thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for
multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent
flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the
real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given
transmission priority; while the non-real-time component, being loss sensitive and delay tolerant,
enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session
of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the
Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow
control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia
session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide
efficient network and radio resource utilization to improve end-to-end multimedia traffic
performance. In order to allow real-time optimization of the QoS control between the real-time
and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management
algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP
incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP
is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the
stringent real-time component’s QoS requirements. The thesis presents results of extensive
performance studies undertaken via analytical modelling and dynamic network-level HSDPA
simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP
based buffer management schemes
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