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A Coupled Processors Model for 802.11 Ad Hoc Networks Under Non Saturation
Get PDFIn this paper we present an analytic approach to performance analysis of ad hoc networks under non saturation conditions, which does not rely on any assumption on traffic statistics. Our approach assumes traffic to be constrained by leaky bucket arrival curves, and it relies on a coupled processors model to capture the dependencies between user achievable rates due to sharing of the wireless transmission medium. We derive sufficient conditions for stability of transmission queues in an ad hoc network, and we describe a method for the determination of a proportionally fair allocation of resources, which allows trading the fairness of the solution for computational complexity. We validate our results through simulations, showing how our approach allows deriving operating points which both increase the fairness of the allocation, and the overall average utilization of network resources, with respect to saturated models.TRUEpu
Priority Queueing with Multiple Packet Characteristics
Get PDFDOI: 10.1109/INFOCOM.2015.7218519Modern network elements are increasingly required to deal with heterogeneous traffic. Recent works consider processing policies for buffers that hold packets with different processing requirement (number of processing cycles needed before a packet can be transmitted out) but uniform value, aiming to maximize the throughput, i.e., the number of transmitted packets. Other developments deal with packets of varying value but uniform processing requirement (each packet requires one processing cycle); the objective here is to maximize the total transmitted value. In this work, we consider a more general problem, combining packets with both nonuniform processing and nonuniform values in the same queue. We study the properties of various processing orders in this setting. We show that in the general case natural processing policies have poor performance guarantees, with linear lower bounds on their competitive ratio. Moreover, we show an adversarial lower bound that holds for every online policy. On the positive side, in the special case when only two different values are allowed, 1 and V, we present a policy that achieves competitive ratio 1 + (W+2)/V, where W is the maximal number of required processing cycles. We also consider copying costs during admission.TRUEpu
NATalyser inhome NAT detection
No full textPresentation of the results that NATalyser. Project Leone (From global measurements to local management): http://leone-project.eu/.TRUEpu
An M/G/1 Model for Gigabit Energy Efficient Ethernet Links with Coalescing and Real-Trace-Based Evaluation
Get PDFIn this work we analytically model the behavior of
gigabit EEE links with coalescing using M/G/1 queues with sleep and wake-up periods. The particularity of gigabit EEE links is that energy saving operations are triggered only when links are inactive in both transmission directions. Our model approximates with a good accuracy both the energy saving and the average packet delay by using a few significant traffic descriptors.
Furthermore, we use real traffic traces to investigate on the performance of static as well as dynamic coalescing schemes. Surprisingly, our evaluation shows that dynamic coalescing does not significantly outperform static coalescing.pu
Boon and Bane of 60 GHz Networks: Practical Insights into Beamforming, Interference, and Frame Level Operation
Get PDFThe performance of current consumer-grade devices for 60 GHz wireless networks is limited. While such networks promise both high data rates and uncomplicated spatial reuse, we find that commercially available devices based on the WiHD and WiGig standards may suffer from their cost-effective design. Very similar mechanisms are used in upcoming devices based on the IEEE 802.11ad standard.TRUEpu
New Methods for Ranking Influence in Social Networks
Get PDFIn this work, propagation dynamics on social networks are studied in order to identify the most influential users. For this purpose, diffusion data has been collected during 4 weeks from a microblogging OSN (online social network) called Tumblr. Then, the propagation graph has been built and studied using the first 2 weeks data (period T1). Subsequently, this graph has been used to predict the influencers during the last 2 weeks (period T2). A ranking of influential nodes is obtained for T2, set as the ground truth. The aim is to predict this ranking using the data from T1. Based on the average spread of users’ posts, rankings obtained with several techniques are tested and compared. These techniques include classical centrality measures used in the literature, the T1 ranking itself, and new alternatives based on effective degree using local (network) information. Whilst all methods perform similarly when considering whole global ranking, differences among them appear when ranking the top influencers. For those, in general, the methods proposed here outperform the classical centrality measures.TRUEpu
A Case Study on Using Probabilistic Verification to Find Failures in a Cooperative Driving Application
No full textThis paper introduces techniques that help proving
the safety of cooperative driving applications. Most automotive applications are evaluated by means of simulations and test tracks, which cannot provide the degree of confidence that is demanded by the driving public. We introduce probability verification as an evaluation tool that provides greater degree of confidence over safety. This technique is applicable to systems with large state spaces that cannot be exhaustively verified by other model checking techniques.
We present a protocol that assists drivers in merging between other vehicles. The protocol is built on a multiple stack architecture that partitions the system into smaller manageable components that can be tested and verified individually. A module is verified assuming that the modules that it depends on have been verified. The modules in different vehicles use synchronized clocks to reduce the number of states needed to be examined in the
composite protocols that describe their interactions. We are able to show that system failures will occur with a sufficiently small probability. Since probabilistic verification is also used to verify
the operation of the modules that provide services, the residual probability of failure of these modules must be considered in the probabilistic verification of any module.TRUEpu
Adaptive Mechanism for Distributed Opportunistic Scheduling
Get PDFDistributed Opportunistic Scheduling (DOS) techniques have been recently proposed to improve the throughput performance of wireless networks. With DOS, each station contends for the channel with a certain access probability. If a contention is successful, the station measures the channel conditions and transmits in case the channel quality is above a certain threshold. Otherwise, the station does not use the transmission opportunity, allowing all stations to recontend. A key challenge with DOS is to design a distributed algorithm that optimally adjusts the access probability and the threshold of each station. To address this challenge, in this paper we first compute the configuration of these two parameters that jointly optimizes throughput performance in terms of proportional fairness. Then, we propose an adaptive algorithm based on control theory that converges to the desired point of operation. Finally, we conduct a control theoretic analysis of the algorithm to find a setting for its parameters that provides a good tradeoff between stability and speed of convergence. Simulation results validate the design of the proposed mechanism and confirm its advantages over previous proposals.pu
Dynamic Network Reconfiguration in Wireless DenseNets with the CROWD SDN Architecture
Get PDFTraffic in wireless access networks has been growing substantially in the recent years, both in terms of total volume and data rate required by individual users. The commonly agreed solution to overcome the current limitations of wireless access networks is to deploy very dense and heterogeneous wireless networks, the so-called
DenseNets. Simply scaling existing networks by orders of magnitude, as required to fulfill traffic forecasts, would bring along several problems because of the limited backhaul capacity, the increased energy consumption, and the explosion of signaling. Hence, the FP7 project CROWD proposes a novel architecture for DenseNets as a solution to tame the density of wireless networks. Within this architecture, flexible flow processing-aware controller placement supported by dynamic backhaul reconfiguration is the crucial component to both (i) maximize the amount of users that can be served simultaneously under high load, and(ii) minimize energy consumption and reduce costs for service providers. We present both approaches in detail and outline how they are integrated into the overall CROWD architecture.TRUEpu
