Hybrid Packet FEC and Retransmission-based Erasure Recovery Mechanisms (HARQ) for Lossy Networks: Analysis and Design
Submitted by networks on Tue, 03/06/2007 - 18:08.
An End-to-End Transport Protocol for Extreme Wireless Network Environments
Submitted by networks on Tue, 03/06/2007 - 18:02.
Source:
In Proceedings of MILCOM 06, IEEE Military Communications Conference, Washington D.C, USA (2006)URL:
http://poisson.ecse.rpi.edu/~vijay/web/work/milcom.pdfAbstract:
As the Joint forces move towards the vision of network-centric warfare (NCW), it is extremely important that the network services be reliable and dependable, even under degraded network conditions. Tactical wireless and satellite based networks are prone to disruptions over multiple time-scales: bursty bit errors and packet loss (small time-scale), interference, jamming and capture effects (medium time-scale) and long-term path disruptions due to persistent channel impairments and mobility (large time-scale). TCP does not work well over such channels because it misinterprets erasure for congestion, and its reliability mechanisms become untargeted when there are disruptions. Large round-trip-times (RTT) as in satellite networks, and uncoordinated optimizations at multiple layers (PHY, MAC and transport) lead to poor performance. In this paper we describe LT-TCP, a robust transport protocol (improving TCP) that is applicable for extreme wireless environments including a mix of multi-hop ad-hoc meshed networks (MANETs), airborne networks and satellite networks. LT-TCP uses an adaptive, end-to-end hybrid ARQ/FEC reliability strategy and ECN for incipient congestion detection. The novelty lies in our adaptive methods that respond to learning about the underlying random packet loss and disruption process. The overhead of FEC or smaller segments is imposed just-in-time and targeted to maximize the performance benefit (measured as improved goodput and timeout reduction) even when the path characteristics are uncertain. We show that LT-TCP substantially improves performance over regular TCP even for packet loss rates of up to 40\% - 50\%, thus substantially extending the dynamic performance range of TCP over lossy wireless networks.Orthogonal Rendezvous Routing Protocol for Wireless Mesh Networks
Submitted by networks on Tue, 03/06/2007 - 17:59.
Source:
In Proceedings of IEEE International Conference on Network Protocols (ICNP), Santa Barbara, CA (2006)URL:
http://www.ecse.rpi.edu/Homepages/shivkuma/research/papers/ICNP2006.pdfKeywords:
Wireless Mesh Networks, Directional Routing, Free Space OpticsAbstract:
Routing in multi-hop wireless networks involves the indirection from a persistent name (or ID) to a locator. Concepts such as coordinate space embedding help reduce the number and dynamism complexity of bindings and state needed for this indirection. Routing protocols which do not use such concepts often tend to flood packets during route discovery or dissemination, and hence have limited scalability. In this paper, we introduce Orthogonal Rendezvous Routing Protocol (ORRP) for meshed wireless networks. ORRP is a lightweight, but scalable routing protocol utilizing directional communications (such as directional antennas or free-space-optical transceivers) to relax information requirements such as coordinate space embedding and node localization. The ORRP source and ORRP destination send route discovery and route dissemination packets respectively in locally-chosen orthogonal directions. Connectivity happens when these paths intersect (i.e. rendezvous). We show that ORRP achieves connectivity with high probability even in sparse networks with voids. ORRP scales well without imposing GHT-like graph structures (eg: trees, rings, torus etc). The total state information required is O(N^3/2) for N-node networks, and the state is uniformly distributed. ORRP does not resort to flooding either in route discovery or dissemination. The price paid by ORRP is suboptimality in terms of path stretch compared to the shortest path; however we characterize the average penalty and find that it is not severe.A Geography-Aware Scalable Community Wireless Network Test Bed
Submitted by admin on Tue, 03/06/2007 - 17:40.
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Source:
Proceedings of IFIP/IEEE Testbeds and Research Infrastructures for the Development of Networks and Communities (TRIDENTCOM), Trento, Italy (2005)URL:
http://www.ecse.rpi.edu/Homepages/shivkuma/research/papers/tridentcom-2005.pdfKeywords:
test bed, wireless mesh networksAbstract:
Wireless mesh networks have increasingly become an object of interest in recent years as a strong alternative to purely wired infrastructure networks and purely mobile wireless networks. Given the challenges that have arisen in construction, deployment, and maintenance of wireless mesh networks, we outline a broad experimental research program in the area of medium-to-large scale community wireless networks. Our research is conducted in the context of an operational community network built in our test bed laboratory with continual plans to expand to the town of Troy, NY (up to hundreds of nodes in a 1-2 mile radius around RPI campus). Leveraging Global Positioning System (GPS) receivers and Geographic Distributed Addressing (GDA), a novel and intuitive addressing assignment, geographic-based forwarding algorithms such as GPSR and TBF can be easily tested and traffic engineering theories implemented in a real-world environment. Our paper documents several design considerations and contributions in implementing community wireless networks including autoconfiguration, addressing structure, and antenna characteristics among other items, in addition to describing our novel test bed lab where RF effects of distances of thousands of meters can be simulated with server, antenna, and variable attenuator clusters.adult online sex cams
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