1,721,212 research outputs found
Performance evaluation of Westwood+ TCP over WLANs with local error control
No full textLink layer error control is widely adopted in wireless LANs (WLANs) to hide the unreliability of the wireless channel to higher level protocols. This allows classic end-to-end congestion control algorithms to achieve acceptable throughput even in the presence of radio links. The present work investigates the performance of Westwood+ and NewReno TCP over a noisy wireless LAN channel. In particular, the effect of local error control persistency on the end-to-end performances of Westwood+ and NewReno TCP is addressed. The investigation has been carried out by using ns-2 computer simulation. Simulation results show that (1) in the presence of uniformly distributed packet losses a well tuned local error control leads both Westwood+ and NewReno TCP to full network utilization; (2) in the presence of bursty losses Westwood+ TCP improves the good-put with respect to NewReno TCP also in the presence of local error control; in particular, Westwood+ TCP requires a smaller number of retransmissions at the link layer than New Reno to achieve full utilization of the wireless channel
Object-Oriented Image Analysis using the CNN Universal Machine: Motion Compensation, Image Synthesis and Consistency Observation
No full textAdaptive Rate Control for streaming flows over the Internet
No full textThe existing end-to-end TCP congestion control algorithm is
well suited for applications that are not sensitive to delay jitter
and abrupt changes of the transmission rate, such as FTP data
transfer, but it is not recommended for delivering video data,
whose perceived quality is sensitive to delay jitter and changes
in the sending rate. In particular, the window-based control of
Reno TCP congestion control causes burstiness in data transmission,
which not only requires large buffers at the client
side to provide a smooth playout but also may provoke bursts
of lost packets difficult to recover via forward error correction
techniques. This paper proposes an adaptive rate-based control
(ARC) algorithm that striclty mimics the real-time dynamics
of TCP and is based on an end-to-end mechanism to estimate
the connection available bandwidth. Computer simulations using
ns-2 have been developed to compare the ARC with the
Reno TCP and with the TCP-Friendly Rate Control (TFRC)
algorithm. Single- and multibottleneck scenarios in the presence
of homogeneous and heterogeneous traffic sources have
been considered. Simulations have shown that the ARC algorithm
improves fairness and is friendly toward Reno. On
the other hand, TFRC revealed itself not to be friendly toward
Reno since it mimics only the long term behaviour of Reno
TCP. Finally, simulations have shown that ARC remarkably
improves the goodput with respect to TFRC and Reno in the
presence of lossy links
Smith's Predictor and Feedforward Disturbance Compensation for ATM congestion control
No full textThis paper proposes an end-to-end congestion control algorithm for available bit rate traffic in high-speed ATM networks. The feedback control law is designed using the Smith principle. Moreover, a feedforward disturbance compensation is added to improve the performance of the control system. The control algorithm is rate based and does not require any explicit feedback from the network. We test the proposed control algorithm over the generic fairness configuration 2 scenario, which is a standard benchmark with multiple bottlenecks and large round trip delays proposed by the ATM forum. Simulation results show that the proposed algorithm provides performance indexes comparable or slightly better than those obtained by the ERICA switch algorithm, which is the leading algorithm in the ATM community, even though ERICA requires explicit support from network nodes
Controllo di congestione rate-based del traffico entrante in reti di telecomunicazioni a commutazione di pacchetto
No full textObject-Oriented Image Analysis via Analogic CNN Algorithms - Part I: Motion Estimation
No full textImage analysis algorithms are of great interest in the context of object-oriented coding schemes. In this paper a new analogic CNN algorithm for obtaining the motion estimation is illustrated, whereas the companion paper (Grassi and Grieco, 2002) focuses on the remaining steps of the object-oriented image analysis stage. Simulation results, carried out for Miss America and Claire video sequences, confirm the validity of the approach developed herei
Object-Oriented Image Analysis via Analogic CNN Algorithms - Part II: Image Synthesis and Consistency Observation
No full textIn the context of image analysis for object-oriented coding schemes, this paper presents new analogic CNN algorithms for implementing the image synthesis and consistency observation stages. Along with the motion estimation algorithm illustrated in the companion paper, the proposed approach represents a framework for implementing CNN-based real-time image analysis. Simulation results, carried out for Miss America video sequence, confirm the validity of the algorithms developed herein. For pt.I see ibid., p.172-9 (2002
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