1. Adaptive RLL Constrained Coding Seong Taek Chung Dec. 17. 2000 Stanford University

2. Background Near Field in Infrared Wireless Channel decoding error, time synchronization error RLL (Run Length Limited) Constrained Coding : d : the minimum # of 0 between 1’s k : the maximum # of 0 between 1’s  the maximum # of 01’s or 10’s

3. Project Topic Current RLL (d,k |  ) : the same RLL code is used once the system is implemented. Proposed RLL (d,k |  ) : different RLL codes are used according to the status of infrared wireless channel.

4. Issues What to adapt ? d? k?  How to adapt?

5. What to adapt? Adaptation of d is sufficient !

6. How to adapt? Transmitter Encoding using RLL chosen at Receiver Receiver Choosing RLL based on infrared channel Feedback the decision on RLL

7. Performance Measure The capacity of adapted RLL : C 0 p 0 + C 1 p 1 C 0 : capacity when RLL (d=0) is used p 0 : probability that RLL (d=0) can support channel ( > 0) C 1 : capacity when RLL (d=1) is used p 1 : probability that only RLL (d=1) can support channel ( > 0)

8. Performance Measure The capacity of non-adaptive RLL : C 1 (p 1 + p 0 ) C 0 p 0 The performance improvement factor    capacity of adapted RLL) / max(capacity of non-adaptive RLL ) = (C 0 p 0 + C 1 p 1 ) / max(C 1 (p 1 + p 0 ), C 0 p 0 )

9. Result 35% improvement when p 0 = 0.65, p 1 =0.35 !

10. Conclusions For infrared wireless channel of our interests, adapting d is sufficient. Adaptive RLL constrained coding improves the capacity up to 35%.