Hamilton Institute Seminars (iPod / small‪)‬ Hamilton Institute

Speaker: Dr. S. Sergeev Abstract: It is well known that the sequence of max-algebraic powers of irreducible nonnegative matrices is ultimately periodic. We express this periodicity in terms of CSR-representations and give new bounds on the transient time after which the max-algebraic powers become periodic.

Speaker: Prof. L. Rizzo Abstract: In this talk I will give a survey of solutions and tools that we have developed in recent years to achieve extremely high packet processing rates in commodity operating systems, running on bare metal and on virtual machines. Our NETMAP framework supports processing of minimum size frames from user space at 10 Gbits per second (14.88 Mpps) with very small CPU usage. Netmap is hardware independent, supports multiple NIC types, and it does not require IOMMU or expose critical resources (e.g. device registers) to userspace. A libpcap library running on top of netmap gives instant acceleration to pcap clients without even the need to recompile applications. VALE is a software switch using the netmap API, which delivers over 20 Mpps per port, or 70 Gbits per second with 1500 byte packets. Originally designed to interconnect virtual machines, VALE is actually very convenient also as a testing tool and as a high speed IPC mechanism. More recently we have extended QEMU, and with a few small changes (using VAEL as a switch, paravirtualizing the e1000 emulator, and with small device driver enhancements), we reached guest to guest communication speeds of over 1 Mpps (with socket based clients) and 5 Mpps (with netmap based clients). NETMAP and VALE are small kernel modules, part of standard FreeBSD and also available as add-on for Linux. QEMU extensions are also available from the author and are being submitted to the qemu-devel list for inclusion in the standard distributions.

Speaker: C. Lancia Abstract: Consider the arrival process defined by t_i=i + \xi_i, where \xi_i are i.i.d random variables. First introduced in the 50's, this arrival process is of remarkable importance in Air Traffic Flow Management and other transportation systems, where scheduled arrivals are intrinsically subject to random variations; other frameworks where this model has proved to be capable of a good description of actual job arrivals include health care and crane handling systems. This talk is ideally divided in two parts. In the first half, I will show through numerical simulations two of the most important features of the model, namely, the insensitivity with respect to the nature (i.e. the law) of the delays \xi_i and the extremely valuable goodness of fit of simulated queue length distribution against the empirical distribution obtained from actual arrivals at London Heathrow airport. Further, I will show that the congestion related to this process is very different from the congestion of a Poisson process. This is due to the negative autocorrelation of the process. In the second part, I will restrict the analysis to the case where the delays \xi_i are exponentially distributed. In this context, I will show some preliminary results on a possible strategy to find the stationary distribution of the queue length using a bivariate generating function.

Speaker: Dr. M. Dohler Abstract: The unprecedented communication paradigm of machine-to-machine (M2M), facilitating 24/7 ultra-reliable connectivity between a prior unseen number of automated devices, is currently gripping both industrial as well as academic communities. Whilst applications are diverse, the in-home market is of particular interest since undergoing a fundamental shift of machine-to-human communications towards fully automatized M2M. The aim of this presentation is thus to provide academic, technical and industrial insights into latest key aspects of wireless M2M networks, with particular application to the emerging smart city and smart grid verticals. Notably, I will provide an introduction to the particularities of M2M systems. Architectural, technical and privacy requirements, and thus applicable technologies will be discussed. Notably, we will dwell on the capillary and cellular embodiments of M2M in smart homes. The focus of capillary M2M, useful for real-time data gathering in homes, will be on IEEE (.15.4e) and IETF (6LoWPAN, ROLL, COAP) standards compliant low-power multihop networking designs; furthermore, for the first time, low power Wifi will be dealt with and positioned into the eco-system of capillary M2M. The focus of cellular M2M will be on latest activities, status and trends in leading M2M standardization bodies with technical focus on ETSI M2M and 3GPP LTE-MTC. Open technical challenges, along with the industry’s vision on M2M and its shift of industries, will be discussed during the talk.

Speaker: Prof. R. Vinter Abstract: Estimates on the distance of a nominal state trajectory from the set of state trajectories that are confined to a closed set have an important unifying role in optimal control theory. They can be used to establish non-degeneracy of optimality conditions such as the Pontryagin Maximum Principle, to show that the value function describing the sensitivity of the minimum cost to changes of the initial condition is characterized as a unique generalized solution to the Hamilton Jacobi equation, and for numerous other purposes. We discuss the validity of various presumed distance estimates and their implications, recent counter-examples illustrating some unexpected pathologies and pose some open questions.

Speaker: Prof. L. Tassiulas Abstract: Increased replication of information is observed in modern wireless networks either in pre-planned content replication schemes or through opportunistic caching in intermediate relay nodes as the information flows to the final destination or through overhearing of broadcast information in the wireless channel. In all cases the available other node information might be used to effectively increase the efficiency of the information delivery process. We will consider first an information theoretic perspective and present a scheme that exploits the opportunistically available overheard information to achieve the Shannon capacity of the broadcast erasure channel. Then we will consider information transport in a multi-hop flat wireless network and present schemes for spatial information replication based on popularity, in association with any-casting routing schemes, that achieve asymptotically optimal performance.