1. Context-aware Adaptive Routing for Delay Tolerant Networking
Mirco Musolesi
Joint work with Cecilia Mascolo
Department of Computer Science
University College London
Delay Tolerant Networks Research Group Meeting
65th IETF Meeting - Dallas, 23 March 2006

2. Outline of this Talk
Overview of the Context-aware Adaptive Routing (CAR) protocol
Extension to hybrid networks
Integration with the DTN reference implementation
Current research directions

3. Context-aware Adaptive Routing (CAR)
Routing protocol for delay tolerant networks initially designed for delay tolerant mobile ad hoc networks
Extension to hybrid networks, where some nodes are fixed or act as gateways for interconnecting different regions
Context-aware routing designed for scenarios where:
Deterministic routing information is not available
No geographical information (like GPS coordinates) are available
Definition of context
Adaptive Routing for Intermittently Connected Mobile Ad Hoc Networks
Mirco Musolesi, Stephen Hailes and Cecilia Mascolo
In Proceedings of 6th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM'05). Taormina, Italy. June 2005.

4. Overview of the Protocol
Based on host(s) acting as carrier(s) for asynchronous delivery of messages to hosts that can be:
Final recipient of the message/bundle
Gateways between regions (fixed or mobile, such as mobile sinks)
Choice of the best carrier(s) based on the evaluation of the context information
Host colocation
Host mobility
Battery level …

5. The Novelty of Our Approach
Novelty of our approach: store-and-forward decisions based on the prediction of the evolution of the DTN scenario
In particular, we use Time Series Analysis based on State Space Models (Kalman Filter) to keep history into account and to predict the evolution of DTN scenarios

6. Asynchronous Delivery: An ExampleB P C A M R D E N F L I Q H O

7. Calculation of the Host Utility
Host utility calculated using multi-criteria decision theory
A utility is associated to each context attribute (i.e., a utility associated to host colocation
Utilities are then composed using a weighted functions

8. Calculation of the Host Utility
We tested the algorithm considering two attributes
Colocation with a certain host (that may be the final recipient of the message or a gateway)
Change degree of connectivity

9. Kalman Filter Prediction
Very lightweight
Only information about the current state must be maintained
Suitable for resource-constrained devices
No “learning” phase is necessary
Fast convergence of the filter
Different prediction models (considering trends and seasonal/periodic behavior)

10. Context-aware Adaptive Routing Protocol
Host utilities are calculated by each host and are sent to the others together with the routing tables (in our implementation DSDV)
Based on local calculations
Adaptive refresh interval based on the context variability
If the carrier of the message gets in reach with a host that can guarantee a better delivery probability, the message is transferred to that host
Local decisionsless traffic
DSDV

11. Predictability of Context Information
Key issue for CAR: predictability of context information
Forecasting model cannot provide accurate predictions due to the inherent characteristics of the time series (for example randomness)
Design of an autonomic component that is able at runtime to analyze the predictability of the time series of the context information
If context information is not predictable, alternative routing strategies can be adopted:
Intelligent epidemic routing …
Evaluating Context Information Predictability for Autonomic Communication
Mirco Musolesi and Cecilia Mascolo
In Proceedings of 2nd IEEE Workshop on Autonomic Communications and Computing (ACC'06). Niagara Falls, NY. June To appear.

12. Integration of CAR in the DTN Reference Implementation
Implementation in the DTN2 reference implementation in process (testing phase)
Porting to resource-constrained devices
Integration of DTN reference implementation in a hybrid environment
DTN reference implementation for gateways?
Integration with other DTN systems for constrained devices (Bluetooth equipped mobile phones, sensor networks).

13. CAR Implementation in DTN2

14. CAR for Multi-Regions DTNs
Based on deterministic and probabilistic mechanisms
For example a server connected to the Internet has delivery probability equal to 1 for the smtp domain.
Message ferries will have a delivery probability equal to 1 to hosts that are on their pre-defined paths
Host utilities used to measure
The probability of delivering message to the recipients of the message for intra-region communication
the probability of delivering messages to gateways (or sinks in sensor networks) for inter-regions communication
Deployed on heterogeneous devices: mobile phones and WiFi APs (in progress), sensor networks (planned)

15. Our Current Research Directions
Implementation of a system based on CAR for inter-regions communications
CAR for sensor networks with mobile sinks
Porting of DTN for Contiki (SICS, Sweden)
Content based routing based on CAR
Design of realistic mobility models
based on social networks theory
validated using real traces
SCAR: Context-aware Adaptive Routing in Delay Tolerant Mobile Sensor Networks
Cecilia Mascolo and Mirco Musolesi
CS-UCL Research Note. January 2006.Submitted for Publication.

16. Questions? Mirco Musolesi
Adaptive Routing for Intermittently Connected Mobile Ad Hoc Networks
Mirco Musolesi, Stephen Hailes and Cecilia Mascolo
In Proceedings of 6th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM'05). Taormina, Italy. June 2005
Evaluating Context Information Predictability for Autonomic Communication
Mirco Musolesi and Cecilia Mascolo
In Proceedings of 2nd IEEE Workshop on Autonomic Communications and Computing (ACC'06). Niagara Falls, NY. June To appear.
SCAR: Context-aware Adaptive Routing in Delay Tolerant Mobile Sensor Networks
Cecilia Mascolo and Mirco Musolesi
CS-UCL Research Note. January 2006.Submitted for Publication.
Mirco Musolesi
Department of Computer Science University College London