Adaptive RLL Constrained Coding Seong Taek Chung Dec Stanford University

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

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.

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

What to adapt? Adaptation of d is sufficient !

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

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)

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 )

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

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