Interest in underwater acoustic networking research has grown rapidly in the past few years. Fundamental differences between underwater acoustic propagation and terrestrial radio propagation call for new criteria for the design of communications systems and networking protocols. In this talk, we will provide an overview of the main challenges posed by the underwater acoustic propagation environment, with special emphasis on networking and protocol design issues, and provide novel insights that are useful in guiding both protocol design and network deployment. We will then address in more detail some specific examples of how the unique features of underwater propagation and acoustic modems affect protocol design. In particular, we will (1) focus on the energy consumption profile of acoustic modems and its impact on the design of topology control mechanisms and on the trade-off between sleep cycles and wake-up modes, and (2) present a novel energy-efficient routing protocol for underwater networks that explicitly accounts for the relationship between hop distance, bandwidth, and energy consumption.

The peer-to-peer paradigm shows the potential to provide the same functionality like client/server based systems, but with much lower costs. One substantial limitation of p2p systems are missing guarantees on the quality of service, as the whole infrastructure is based on unreliable peers. In order to control the quality of peer-to-peer systems, monitoring and management mechanisms need to be applied. Both tasks are challenging in large-scale networks with autonomous, unreliable nodes.

According to most technology pundits, progress in wireless and sensor networks will lead us into a world of ubiquitous computing, in which myriads of tiny, untethered sensors and actuators will communicate with each other. Information technology will thus deliver its most encompassing and pervasive accomplishment to mankind, promptly taking care of the needs and wishes of everyone.

Mobile communications networks have been evolved through multiple technologies over a period of several decades, to a stage that they become very complicated in the context of resource control and management. The heterogeneous next generation mobile network (NGMN) now includes a variety of network technologies and topologies incorporating with one another to provide a wide range of services; operate in a variety of channel conditions and environments; and within a single universal end user device. NGMN will need to be offered as an integrated system, and to promote interoperability among networks, offer global coverage and seamless mobility, enable the use of a universal handheld terminal, and enhance service quality compared to current wired networks. NGMN will be the infrastructure of the true mobile Internet.

Wireless mesh networks are becoming popular alternatives to wireless LANs and for cost-effective use in varied application environments. There are several technical challenges that must be addressed for mesh networking to be as effective as any other form of broadband networking. Much of these challenges relate to multi-hop wireless communication and limited capacity. The goal of this informal presentation is to facilitate further discussions on these challenges.

"ADSL is becoming the standard form of residential and small-business broadband access to the Internet due, primarily, to its low deployment cost. These ADSL residential lines are often deployed with Access Points (AP) that provide wireless connectivity. While the ADSL technology has showed evident limits in terms of capacity, the short-range wireless communication can guarantee a similar or higher capacity. Even more important, it is often possible for a residential wireless client to be in range of several other APs belonging to nearby neighbors with ADSL connections. We introduce ClubADSL, a prototype wireless station that can connect to several multi-frequency APs in range and aggregate their available ADSL bandwidth. ClubADSL achieves a fair bandwidth among the concurrent stations and minimizes the impact of end-to-end latency on the system performance. We show the feasibility of such a system in seamlessly transmitting TCP traffic, and validate its experimental implementation over commodity hardware in controlled scenarios."

Mobility is, without doubt, one of the major new paradigms of the current Internet, and this is driving most of the research activity in networking throughout the World. We are gradually evolving from a network where most end-systems have a fixed or quasi-fixed point of attachment, towards a global network where end systems seamlessly move from network to network and where networks themselves change their connection point to the Internet. In spite of this there is still a long way to go before user and network mobility – at IP level – become a reality, as several technological and research challenges persist.

Normal TCP/IP operation is for the routing system to select a best path that remains stable for some time, and for TCP to adjust to the properties of this path to optimize throughput. A multipath TCP would be able to either use capacity on multiple paths, or dynamically find the best performing path, and therefore reach higher throughput. By adapting to the properties of several paths through the usual congestion control algorithms, a multipath TCP shifts its traffic to less congested paths, leaving more capacity available for traffic that can't move to another path on more congested paths. And when a path fails, this can be detected and worked around by TCP much more quickly than by waiting for the routing system to repair the failure.

Sorry, this entry is only available in Español.  Instructor:  Lugar:  Fecha: 12th May, 2009, 10:00 – 11:00 Organización: