Stochastic traffic engineering for live audio/video delivering over energy-limited wireless access networks

Part 4: Energy Efficiency International audience We study the Stochastic Traffic Engineering (STE) problem arising from the support of QoS-demanding live (e.g., real time) audio/video applications over unreliable IP-over-wireless access pipes. First, we recast the problem to be tackled in the form of a suitable nonlinear stochastic optimization problem, and then we develop a goodput analysis for the resulting IP-over-wireless pipe that points out the relative effects of fading-induced errors and congestion-induced packets losses. Second, we present an optimal resource-management policy that allows a joint scheduling of playin, transmit and playout rates. Salient features of the developed joint scheduling policy are that: i) it is self-adaptive; and, ii) it is able to implement reliable Constant Bit Rate (CBR) connections on the top of unreliable energy-limited wireless pipes. Document type: Part of book or chapter of boo

Jointly Optimal Source-Flow, Transmit-Power, and Sending-Rate Control for Maximum-Throughput Delivery of VBR Traffic over Faded Links

Emerging media overlay networks for wireless applications aim at delivering Variable Bit Rate (VBR) encoded media contents to nomadic end users by exploiting the (fading-impaired and time-varying) access capacity offered by the "last-hop" wireless channel. In this application scenario, a still open question concerns the closed-form design of control policies that maximize the average throughput sent over the wireless last hop, under constraints on the maximum connection bandwidth available at the Application (APP) layer, the queue capacity available at the Data Link (DL) layer, and the average and peak energies sustained by the Physical (PHY) layer. The approach we follow relies on the maximization on a per-slot basis of the throughput averaged over the fading statistic and conditioned on the queue state, without resorting to cumbersome iterative algorithms. The resulting optimal controller operates in a cross-layer fashion that involves the APP, DL, and PHY layers of the underlying protocol stack. Finally, we develop the operating conditions allowing the proposed controller also to maximize the unconditional average throughput (i.e., the throughput averaged over both queue and channel-state statistics). The carried out numerical tests give insight into the connection bandwidth-versus-queue delay trade-off achieved by the optimal controller

QoS Stochastic Traffic Engineering for the wireless support of real-time streaming applications

In this work, the Stochastic Traffic Engineering (STE) problem arising from the support of QoS-demanding real-time (e.g., delay and delay-jitter sensitive) media-streaming applications over unreliable IP-over-wireless pipes is addressed. Two main contributions are presented. First, we develop an optimal resource-management policy that allows a joint scheduling of the source rate, transmit energy and playout rate. Salient features of the proposed scheduling policy are that: (i) it is self-adaptive; and, (ii) it is able to provide hard (i.e., deterministic) QoS guarantees, in terms of hard limited playout delay, playout rate-jitter and pre-roll delay. Second, by referring to power and bandwidth limited access scenarios, we develop a traffic analysis of the underlying IP-over-wireless pipes that allows us to analyze the effects of both fading-induced errors and congestion-induced packet's losses on the end-to-end performance of the proposed scheduler. © 2011 Elsevier B.V. All rights reserved

Stochastic traffic engineering for real-time applications over wireless networks

In this work, we focus on the Stochastic Traffic Engineering (STE) problem arising from the support of QoS-demanding real-time media-streaming applications over fading and congestion affected TCP-friendly/IP multiantenna wireless pipes. First, after recasting the tackled STE problem in the form of a suitable cross-layer nonlinear stochastic optimization problem, we develop a traffic analysis of the overall underlying multiple-input multiple-output (MIMO) wireless pipe that points out the relative effects of both fading-induced errors and congestion-induced packet losses on the goodput offered by the resulting end-to-end connection. Second, we develop an optimal cross-layer resource management policy that allows a joint scheduling of the media encoding rate (i.e., playin rate), transmit energy and delivery rate (i.e., playout rate) of each end-to-end connection active over the considered access network. Salient features of the presented joint scheduling policy are that: (i) it is self-adaptive: (ii) it is able to provide hard (i.e., deterministic) QoS guarantees, in terms of hard limited playout delay and playout rate-jitter; and (iii) it explicitly accounts for the performance interaction of the protocols implemented at all layers of the considered stack. (C) 2011 Elsevier Ltd. All rights reserved

Joint control of bandwidth and playout-delay for streaming traffic over faded links (Best Paper Award)

In this paper we develop an optimized control strategy for the connection bandwidth maximization over a time varying wireless channel, by jointly controlling the adaptive source rate and the client/playout buffering policy with constraints on the maximum connection bandwidth allowed at the Application (APP) layer, the queue-capacities available at the Data-Link (DL) layer and the average and peak transmit energies sustained by the Physical (PHY) layer. The main feature of the approach we follow lies in the fact that the maximization of the throughput is performed with respect to the channel state information as well as the occupancies of the transmitter and receiver buffers, taking into account also for the need to optimize the playout buffer service so to reduce the stream-jitter provided to the final user. The resulting optimal controllers operate in a Cross-Layer (CL) fashion that involves the APP, DL and PHY layers of the underlying protocol stack. Via a parameter-depending optimization we are able to handle the jitter of the stream provided to the final user without significant impact on the bandwidth performances. The carried out numerical tests give insight into the tradeoff among average throughput, delay and jitter attained by the optimized controllers. ©2010 IEEE

Optimized joint bandwidth and playout control for streaming-traffic over wireless-channels

to be published on Communication in Applied and Industrial Mathemathics

Dermoscopy of congenital melanocytic nevi: a ten-year follow-up study and comparative analysis with acquired melanocytic nevi arising in prepubertal age

Dermoscopic characteristics of congenital melanocytic nevi (CMN) have been reported, however, dermoscopic variation during long-term follow-up and direct comparative analyses with acquired melanocytic nevi (AMN) are poorly documented. To assess dermoscopic changes of CMN (including lesions present at birth or appearing within the first two years of age) after a long-term period and evaluate possible dermoscopic differences with AMN arising during prepubertal age. We re-analysed clinical and dermoscopic features of CMN, investigated ten years earlier. New findings were compared with those previously recorded, as well as with those of AMN appearing before puberty in the same group of patients. In total, 493 lesions (86 CMN and 407 AMN) from 71 patients were examined. Except for a greater size (median area: 73.9 vs 22.8\ua0mm(2); p0.05). The follow-up of CMN revealed that dermoscopic pattern changed in only four lesions (4.7%) (from globular to globular-reticular or reticular) after ten years, though lesions with a globular architecture presented several "local" changes, namely an increase in circumscribed reticular areas (from 20.0% to 41.5%; p\ua0=\ua00.030), irregularly distributed globules (from 15.6% to 34.1%; p\ua0=\ua00.045), and large globules (from 46.7% to 68.3%; p\ua0=\ua00.043). The dermoscopic appearance of CMN is significantly stable during childhood and is similar to that of AMN arising before puberty, thus supporting a possible link between such types of nevi

A cross-layer approach to the optimal flow, power and rate control for maximum-throughput delivery of VBR traffic over wireless connections

The delivering of variable bit rate (VBR) encoded media contents to nomadic end-users through the 'last-hop' wireless connection, rises up several challenges related to the fading-impaired and time-varying nature of the wireless medium itself. In detail, a still open question concerns the closed-form design of cross-layer control policies to maximise the average throughput while taking into account constraints comprising layers of the protocol stack from the physical (PHY) up to the application (APP) one. To overcome the computational cost entailed by dynamic programming solutions, the approach we follow aims at the maximisation (on a per-slot basis) of the throughput averaged over the fading statistic and conditioned on the queuestate. To show the performance of the proposed controller, (tight) upper and lower bounds have been derived for the average throughput and numerical tests have been presented to give insight into the connection bandwidth vs. queuedelay tradeoff. Copyright © 2011 Inderscience Enterprises Ltd