Ακαδημαϊκά Νέα

16ο Πανελλήνιο Συνέδριο Πληροφορικής (PCI 2012)

October 5 – 7, 2012
University of Piraeus, Greece
http://pci2012.unipi.gr

The Greek Computer Society (ΕΠΥ), the Department of Informatics and the Department of Digital Systems, of the University of Piraeus organize the 16th Panhellenic Conference on Informatics (PCI 2012) in Piraeus, Greece, on 5 – 7 October 2012.
The PCI is an event established by the Greek Computer Society. The 1st Conference took place in Athens 1984. Subsequent events took place in Thessaloniki (1988), Athens (1991, 1993, 1995, 1997), Ioannina (1999), Nicosia Cyprus (2001), Thessaloniki (2003), Volos (2005), Patras (2007), Samos (2008), Corfu Island (2009), Tripoli (2010), and Kastoria (2011).

DC-free Run-Length Limited Modulation Codes: new techniques and results

Run-Length Limited (RLL) coding is used as modulation codes in virtually all optical disks (CD, DVD, Blu-Ray) and magnetic media, such as hard drives. It involves binary sequences that have a minimum and maximum length of same-polarity physical symbols. These two values (minimum and maximum  run-length) are referred to as (d,k) RLL constraints. It’s theory dates back to Shannon himself, who first calculated the capacity of a channel under such constraints. DC-free, or – in general – minimum low-frequency content RLL codes is the most popular class of these codes. Immink designed the popular eight-to-forteen modulation (EFM) used by Compact Disks in the 80s and EFM+ used by DVDs in the 90s. The former is a block-code while the later is a state-dependent coding scheme. We will present the theory and background of RLL codes, together with some recent results regarding: state-dependent codebook optimization; enhanced error resilience through maximum likelihood and Viterbi decoding; an improved metric used for encoding; the effect of look-ahead encoding and the applicability of stack-algorithm in look-ahead encoding. Finally, a new theoretical result on (d,k) RLL coding channel capacity and the comparison to (d,k,c) RLL coding.