Talk given at the 9th International Conference on Artificial Immune Systems (ICARIS), 2010, Edinburgh, UK

1. Modular RADAR: Immune System
Inspired Strategies for Distributed
Systems
Soumya Banerjee and Melanie Moses
University of New Mexico

2. Outline
• Distributed systems and the natural immune system (NIS)
operate under similar constraints
• Effect of body size on NIS search and response times
• Scale invariant detection and response
• Hypothesis: architecture of the lymphatic system leads to
invariant search and response times
• Modular RADAR strategy
• Number and size of lymph nodes increases with organism
size
• Distributed systems
– P2P system
– Multi-robot control
• Future directions

3. Properties of Distributed Systems
• Physical space is important
• Resource constrained (power, bandwidth)
• Performance scalability is a desirable feature

4. Properties of the Natural Immune
System (NIS)
• Operates under constraints of physical space
• Resource constrained (metabolic input,
number of immune system cells)
• Performance scalability is an important
concern (mice to horses)

5. Problems Faced by the NIS
• Only a few NIS
cells are specific
to a particular
pathogen (1 in
6
10 T-cells)

6. Search Problem
• They have to
search
throughout the
whole body to
locate small
quantities of
pathogens

7. Response Problem
• Have to respond
by producing
antibodies

8. West Nile Virus infection
 25 species of birds and 4
species of mammals infected with
WNV
• Bunning et al. (2002)
• Komar et al. (2002)
 Unimodal peak at ~ 2 to 4 days
post infection
 Immune response rates and
times are not correlated with host
mass
• assuming immune response
causes peak
• B-cell response in mice ~ 4
days
Komar et al. 2002

9. Nearly Scale-Invariant Search and
Response
• Experimental data
indicates that the
NIS can search for
pathogens and
respond by
producing antibodies
in time invariant of
organism body size

10. Nearly Scale-Invariant Search and
Response
• How does the
immune system
search and
respond in
almost the same
time irrespective
of the size of the
search space?

11. Solution: Lymph Nodes (LN)
• A place in which IS cells and the pathogen can
encounter each other in a small volume
• Form a decentralized detection network
Crivellato et al. 2004

12. Modular RADAR
• Search is now
– modular
– efficient
– parallel
We call this a modular RADAR (Robust
Adaptive Decentralized search Automated
Response)

13. Hypothesis
• Architecture of the immune system is
responsible for nearly scale-invariant search
and response properties
• We now focus on West Nile Virus
www.lymphadvice.com

14. Lymph Node Dynamics

15. Lymph Node Dynamics

16. Lymph Node Dynamics

18. DC DC cTcell,DC
T t detect t migrate t detect trecruit

19. Scaling of LN Size and Number
T t local t global
DC DC DC,cTcell
T t detect t migrate t detect t recruit
After minimizing we have
4 /7
N M ,where N is the number of LNs
3/7
VLN M ,where VLN is the size of a LN
• this is in qualitative agreement with data
• need more data
Banerjee and Moses 2010, Swarm Intelligence (under review)

22. Modular RADAR Architecture
T t local t global M1/ 7

23. Summary
• There are increasing costs to global
communication as organisms grow bigger
• Semi-modular architecture balances the opposing
goals of detecting pathogen (local
communication) and recruiting IS cells (global
communication)
• This leads to scale invariant detection and
response
• Can we emulate this modular RADAR strategy in
distributed systems?

24. Peer-to-Peer Systems
• Used to provide distributed services like
search, content integration and administration
• Computer nodes store data or service
• No single node has complete global
information
• Decentralized search using local information
to locate data

25. Semantic Small World (SSW) P2P
Overlay Network
• Represents objects by a collection of attribute values
derived from object content
• Aggregates data objects with similar semantics close
to each other in clusters in order to facilitate efficient
search
• It maintains short and long-distance connections
between clusters.
• The long-distance connections follow a precise
probability distribution making the whole overlay
network small-world (Kleinberg 2000)
* M. Li et al. 2004

26. Semantic Small World (SSW) P2P
Overlay Network
adapted from M. Li et al. 2004

27. Bounds for Efficient Decentralized
Search in SSW
• Average search path length for search across
clusters is
2
log (n /c)
tglobal O
l
where n is the total number of nodes,
c is the number of nodes in a cluster,
l is the number of long-distance
connections per node
M. Li et al. 2004

28. SSW with Modular RADAR
• Our contribution is to
– vary the cluster size
– vary the number of long-distance connections
as
l log(n /c) log(numclusters)
t global O(log(n /c))
– such densification is seen as an emergent
property of technological networks (Kleinberg
2004) and also incorporates redundant paths

29. Time to Search in SSW with
Modular RADAR
T t local t global
1/ 2
T 1c 2 log(n /c)
minimizing by differentiating with respect to c
we have
c O(log 2 n)
T O(log n log log n)

30. SSW with Modular RADAR

31. Wireless Mobile Devices: Original
System
adapted from Nair et al. 2008

32. Tradeoffs
• Potential communication bottlenecks
– local communication between robots and
computer servers
– global communication between computer servers
• If both local and global communication are
constrained, then sub-modular architecture balances
tradeoff

33. System modified with modular
RADAR

34. Future Directions
• Strategy is widely applicable
• A modular RADAR strategy can be used to augment
– Intrusion Detection Systems (Hofmeyr and Forrest
1999)
– Multi-Robot Control
– Wireless Sensor Networks
– Wireless Devices (Specknets: Hart and Davoudani
2009)
– Collective Robotic Systems using Artificial Lymph
Node Architectures (Mokhtar, Timmis, Tyrrell and Bi
2008)

35. Summary
• The NIS and distributed systems operate under similar
constraints
• Physical space of organism body constrains NIS search and
response times
• The NIS has evolved a sub-modular RADAR architecture in
which LN numbers and sizes increase with organism body
size
• This balances the tradeoff between local communication
(pathogen detection) and global communication (antibody
production); this leads to scale invariant detection and
response
• Similar tradeoffs also exist in distributed systems
• Such a modular RADAR approach is shown to improve
search times in P2P and multi-robot control systems
• Can be applied in other distributed systems

36. Acknowledgements
• Dr. Melanie Moses • SFI Complex Systems
• Dr. Alan Perelson Summer School
• Dr. Stephanie • Travel grants from
Forrest PIBBS (Dept. of
Biology, UNM)
• Dr. Jedidiah Crandall
• Travel grants from
• Dr. Rob Miller
RPT and SCAP
• Dr. Sam Loker (UNM)
• NIH COBRE CETI
grant (RR018754)