[Nrg-l] NRG resumes this week

Niky Riga inki at cs.bu.edu
Tue Jul 19 11:32:35 EDT 2005

On this week's NRG Hany will present a paper that appeared in SenSys 04.
The title of the paper is :
"Energy-Efficient Forwarding Strategies for Geographic Routing in Lossy 
Wireless Sensor Networks". (http://nile.usc.edu/~seada/Sensys.pdf 
The NRG will take place on Wednesday (July 20th) at 4:00pm at the grad 
The abstract follows.



Recent experimental studies have shown that wireless links in real 
sensor networks can be extremely unreliable, deviating to a large extent 
from the idealized perfect-reception within-range models used in common 
network simulation tools. Previously proposed geographic routing 
protocols commonly employ a maximum-distance greedy forwarding technique 
that works well in ideal conditions. However, such a forwarding 
technique performs poorly in realistic conditions as it tends to forward 
packets on lossy links. We identify and illustrate this weak-link 
problem and the related distance-hop trade-off, whereby energy efficient 
geographic forwarding must strike a balance between shorter, 
high-quality links, and longer lossy links. The study is done for 
scenarios with and without automatic repeat request (ARQ). Based on an 
analytical link loss model, we study the distance-hop trade-off via 
mathematical analysis and extensive simulations of a wide array of 
blacklisting/link-selection strategies; we also validate some strategies 
using a set of real experiments on motes. Our analysis, simulations and 
experiments all show that the product of the packet reception rate (PRR) 
and the distance traversed towards destination is the optimal forwarding 
metric for the ARQ case, and is a good metric even without ARQ. Nodes 
using this metric often take advantage of neighbors in the transitional 
region (high-variance links). Our results also show that reception based 
forwarding strategies are more efficient than purely distance-based 
strategies; relative blacklisting schemes reduce disconnections and 
achieve higher delivery rates than absolute blacklisting schemes; and 
that ARQ schemes become more important in larger networks.

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