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When Communication is expensive

This paper explores the challenges and solutions for communication in domains with unreliable, single-channel, low-bandwidth communication. It discusses the architecture, paradigm, and implementation strategies, as well as addressing challenges such as message targeting, robustness to active interference, handling multiple simultaneous responses, robustness to lost messages, and team coordination.

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When Communication is expensive

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  1. When Communication is expensive Xiang Song

  2. Paper List • Communication in Domains with Unreliable, Single-Channel, Low-Bandwidth Communication,Peter Stone, Manuela Veloso,Computer Science Department,Carnegie Mellon University, 1997

  3. Contents • Introduction • Challenge • Architecture • Paradigm • Implementation • Conclusion

  4. Introduction

  5. Challenges

  6. Architecture Robot Internal Behavior World State World Locker-room Agreement Internal State External Behavior

  7. Architecture • Example (When a message is received) • response • response-flag • communicate-delay • if (response-flag set and communicate-delay==0) then SAY(response)

  8. Paradigm • <team-identifier> <unique-team-member-ID> <encoded-time-stamp><time-stamped-team-strategy><selected-internal-state><target><message-type><message-data>

  9. How Are Challenges Addressed? • Message targeting/distinguishing • <team-identifier> & <target> team-identifier Police Thief 1 3 2 1 2 4 5

  10. A thief is in front of me ? A thief is in front of me How Are Challenges Addressed? • Robustness to active interference

  11. A thief is in front of me(t) A thief is in front of me(t) ! How Are Challenges Addressed? • Robustness to active interference • <encoded-time-stamp> Now it is time u

  12. 1 2 3 4 5 How Are Challenges Addressed? • Multiple simultaneous responses • <message-type> • In cases b2 and b3, set communicate-delay based on the difference between <unique-team-member-ID> so that each teammate respond at different time.

  13. That’s OK How Are Challenges Addressed? • Robustness to lost messages • Agents don’t depend on communication to act

  14. My current strategy is newer. I will not change Change strategy How Are Challenges Addressed? • Team coordination • Globally accessible environmental cues as triggers • <encoded-time-stamp> & <time-stamped-team-strategy> • <selected-internal-state>

  15. Implementation • RoboCup’s 97 • Characteristics • All 22 agents (including adversaries) one same channel • Limited communication range and capacity • No guarantee of sounds getting through • Instantaneous communication • High communication cost

  16. Implementation • CMUUnited<Uniform-number><Encoded-stamp><Formation-number><Formation-set-time><Position-number><target><Message-type>[<Message-data>]

  17. Implementation CMUUnited <Uniform-number><Encoded-stamp><Formation-number><Formation-set-time><Position-number><target><Message-type>[<Message-data>] CMUUnited 8 312 1 0 7-->6 where are you? CMUUnited 6 342 1 0 5-->all I’m at 4.1 -24.5 Where? Here!

  18. 1 2 3 4 5 Implementation • Set the communication-delayIF ((myNumber > senderNumber) ((myNumber-senderNumber-1)*2 *communicate-intervalELSE (((senderNumber-myNumber-1)*2)+1) *communication-interval

  19. Implementation djklfjaldksjds • Test Result • Cost of communication • Team A: no communication • Team B: say random strings • 3.54 : 1.08 over 50 games • Ability to ignore the active interference • Team C: use <Encoded-stamp> • Team D: repeat past opponent messages • False messages are correctly ignored.One true message is incorrectly ignored.

  20. 1 2 3 4 5 Implementation • Ability to handle multiple simultaneous responses • Ability to maintain coordinated team strategies

  21. Weakness • When communication does not work • Work independently is a solution, but not the best • Probable solution: gather after some time • When every agent wants to update the team strategy • Strategies change too often. • Unique decision-make may make mistakes(because communication is unreliable)

  22. Conclusion • Low band-width, single channel, unreliable communication • 1. Message targeting/distinguishing, • 2. Robustness to active interference • 3. Multiple simultaneous responses • 4. Robustness to lost messages • 5. Team coordination

  23. Conclusion • Semi-finals of RoboCup’97

  24. Questions?

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