Real Time Sensor Networks – challenges and solutions
Sandeep Kakumanu, Rajnish Kumar, Sriram Lakshmanan, Badri Narayanan, Nazanin Rahnavard, Junsuk Shin
Faramarz Fekri, Umakishore Ramachandran, Raghupathy Sivakumar
Real Time Sensor Networks
• The primary goal in designing protocols for conventional
sensor networks is to optimize energy consumption of the
sensors.
• Real time sensor networks however are dependent more
on timely delivery of data rather than energy constraints.
• Applications include multimedia sensor and time critical
sensor requirements.
Challenges of Real time sensor networks
Three main challenges of real-time sensor networks
• Timeliness
• Reliability (Packet level)
• Correctness (Application level)
These requirements must be ensured in both the
upstream and downstream directions. We work at different
layers of the network stack to address these challenges.
CRBcast
REQ, j packets
DATA, max(i,j) packets
ADV
REQ, i packets
(ii)
Objective:
• Aggregate correlated data from different sensors
(homogenous or heterogenous sensors) in order to save
bandwidth, reduce latency, reduce energy consumption
and provide application level correctness.
Motivation:
Two existing approaches for data aggregation:
1. Correlation unaware: Shortest path tree. Does not
maximize the aggregations possible.
2. Correlation aware: Steiner Tree. Complex calculations at
individual sensors. Maximal aggregations.
• Require efficient aggregation strategy that minimizes
message complexity.
Proposed scheme:
• SCT (Semantic/Spatial Correlation-aware Tree) – A
distributed coordination scheme that achieves potential
cost benefits of efficient aggregation. Can be used for
spatial, temporal or semantic correlation of data.
Information Prioritization
Objective:
• Broadcasting in multihop wireless networks
• Energy-Efficient, Reliable, Scalable
• Low Complexity: Requires no topology knowledge
Motivation:
• Updating
software
in
already
deployed
sensor/actuator networks
• Broadcasting route query packets in reactive routing
schemes
Proposed scheme:
• CRBcast – a two phase data dissemination algorithm
(employing rateless coding) that generalizes
probabilistic broadcasting to further reduce the energy
costs.
(i)
SCT
(iii)
Objective:
• Right information at the right time
Motivation:
• Moving from a centralized to a distributed solution
• Increase Information-Awareness (Cognitive-Awareness)
• Information Prioritization and Fidelity Adjustment
Proposed scheme:
• Design techniques for priority assignment to an
information in a mission-specific manner,
• Identify a measure of effectiveness (MOE) to evaluate
the prioritization algorithms,
• Design and implement algorithms for disseminating
prioritized data,
• Evaluate different prioritization algorithms to identify their
strength and limitations, and
• Fine-tune the IP stack for an efficient support of
prioritized information dissemination.
Application 1 :
• IPTV enhancement using WSN.
Illustration of application scenario
Broadband
Connection
TV
TV
User
STB
STB
User
sensor
Sink
TV
STB
TV
STB
User
User
Two principles to enhance IPTV :
1. “What you see is what you fetch”
– In cases where there is no active user but the
television is on, streams can be sent from server at
low priority, low data rate or even paused.
2. “Fetch possible next channel(s) just before the user
switches”
– Pre-fetching channels in the background to reduce the
user perceived channel switching latency.
Application 2 :
• Video Surveillance Application with information
prioritization
Principle:
• Use sensor information to prioritize data from highbandwidth video cameras.
Details of the applications can be found in the individual
posters