Download - Dongjin Son, Bhaskar Krishnamachari and John Heidemann Presented by Anandha Gopalan Nov. 3, 2004
Experimental study of the effects of Transmission Power Control and
Blacklisting in Wireless Sensor Networks
Dongjin Son, Bhaskar Krishnamachari and John Heidemann
Presented by Anandha Gopalan
Nov. 3, 2004
Outline
IntroductionExperiments Transmission Power Control (TPC) with
blacklistingConclusion and Future work
Introduction
Zikes !!! Yet another paper on power-management
This one has a slightly different take about it Thank goodness for that
So, what’s different ??? Simulations usually assume idealized link conditions
Experimentally evaluate the effect of transmission power on link conditions
Sometimes, increasing TP may help Aha !!! that’s a bit different
Experiments
Effects of unreliable wireless linksEffects of TPCExperimental study of varying TP on a
single wireless link One receiver and multiple transmitters One transmitter and multiple receivers Wireless link distance Node location (Multi-Path and Interference) Time (Environment change)
Experiments
Testbed PC104 testbed with mica2 motes Directed diffusion routing S-MAC MAC protocol
Weak link Packet Reception Rate (PRR) < Threshold
Asymmetric link PRR > Threshold in only one direction
Experiments
Effect of unreliable wireless links Having unreliable links is worse than having any
links at all They tend to be utilized
Convert unreliable links to good links or prevent them from being used
Experiments
Effects of TPC Increased TP leads to more good links
Unreliable links can be converted to good links New communication links can be discovered
and used for packet delivery Problem: May lead to new unreliable links
Taken care of by blacklisting Problem: May use up more network capacity
Experiments
New definitions: Weak link
Packet Reception Rate (PRR) < Threshold, even after TPC
Asymmetric link PRR > Threshold in only one direction, even after
TPC
Experiments
One receiver and multiple transmitters Difference is not obvious at close distances Difference b/w node 27 and nodes (30,20)
noticed after a distance of 17m Difference b/w nodes 30 and 20 noticed after a
distance of 23m
Experiments
One transmitter and multiple receivers In the TP range b/w -3 and 6 dBm, the link
quality is different at the same TP level, while different TP is required for each link to reach the same PRR level
Range of TP that generates this kind of variation is called unreliable transmission power range (UTPR)
UTPR can be avoided in two ways: Assign a TP high enough for every link to be outside
UTPR Assign a distinct TP for each link
Experiments
Effect of wireless link distance Clear line of sight b/w transmitter and receiver Distance b/w transmitter and receiver is varied Experiments show that new reliable,
communication links that are not available at default TP can be generated with TPC
Experiments
Effect of node location No clear line of sight b/w the sender and
receiver Receiver is placed in six different locations in
the same indoor environment Results:
Multi-path interference effect are severe indoors, where signal is weak
Severe link quality variation can be expected with small movement of sensor nodes
Experiments
Effect of surrounding environment change Variation in link quality is observed at different
times of the day and night Results:
Variation in link quality observed during the day due to change in surrounding environment
The difference in link quality is only b/w the TP of -7 to 2 dBm
TPC with blacklisting (PCBL) - Characteristics
TPC for link quality control Convert unreliable links to reliable links
Packet-based TPC TP is assigned to each packet based on its
destination and type of packet, considering link quality requirement
Metric-based link quality estimation Link quality is measured based on PRR
PCBL - Characteristics
Blacklisting at adjusted TP level Not all links can be converted to a good link
with TPC New weak or asymmetric links can be
generated at adjusted TP level Blacklisting is used with TPC to remove
remaining unreliable links after TPC
PCBL - Algorithm
1. Collect link statistics in PRR metric2. Select a unicast power for each link3. Blacklist unreliable links4. Select a broadcast power for each node
PCBL - Algorithm
1. Collect link statistics PRRs at pre-selected transmission power levels
are collected
2. Select a unicast power for each link Select a link quality control threshold (THLQ) Unicast power for each link is assigned such
as: Ui->j = P where PRRpi > THLQ and P = min pi, otherwise Ui->j is set to maximum TP (Pmax)
PCBL - Algorithm
3. Blacklist unreliable links Links that cannot be converted to good links
based on the blacklist threshold (THBL) are blacklisted and not used for any packet transmission or reception
4. Select a broadcast power for each node Broadcast transmission power of node i (Bi) is
selected to be max (Ui->j ) Ensures that broadcast packets reach every node
with a good wireless link
PCBL Algorithm – On-demand optimization for Long-lived Routing
1. Collect link statistics only at the maximum transmission power level
2. Blacklist unreliable links before using a routing protocol
3. Find a delivery path with a routing protocol
4. Identify unicast transmission powers to use only for links in the delivery path
PCBL – Analysis for Single Data Flows
Packet Delivery Rates PCBL is better than TPP-P0, TPP-P5 and TPP-
P10, but worse than M-BL
Energy Consumption PCBL consumes more than TPP-P0
Energy consumption per packet PCBL consumes less than TPP-P0
PCBL – Analysis for Multiple Data Flows
Packet Delivery Rates PCBL is better than M-BL for flows 1&2, but is
slightly worse for flow 3 Improvement in flows 1&2 due to the saturation
of the wireless link around node 11 for M-BL
Conclusion and Future work
Presented an experimental study of the effects of TPC on wireless link quality
A TPC scheme with blacklisting for link quality control was proposed
Analysis of the proposed scheme was carried out using experiments
Optimizations for the proposed algorithm is to be studied for future work
Issues with the paper
Overhead of collecting link statistics ???How are the statistics collected ???Comparing PCBL with TPP-P0, TPP-P5
and TPP-P10 for multiple flowsHow do you get the threshold values ???Mistakes in the paper
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