Cyclic Designs with Block Size 4 and Related Optimal Optical Orthogonal Codes

  • Authors:
  • Marco Buratti

  • Affiliations:
  • Dipartimento di Matematica e Informatica, Università di Perugia, Via Vanvitelli 1, 06123 Perugia, Italy buratti@mat.uniroma1.it

  • Venue:
  • Designs, Codes and Cryptography
  • Year:
  • 2002

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Abstract

We prove the existence of a cyclic (4p, 4, 1)-BIBD—and hence, equivalently, that of a cyclic (4, 1)-GDD of type 4p—for any prime p \equiv 1 \pmod 6 such that (p−1)/6 has a prime factor q not greater than 19. This was known only for q=2, i.e., for p \equiv 1 \pmod 12. In this case an explicit construction was given for p \equiv 13 \pmod 24. Here, such an explicit construction is also realized for p \equiv 1 \pmod 24.We also give a strong indication about the existence of a cyclic (4p 4, 1)-BIBD for any prime p \equiv 1 \pmod 6, p7. The existence is guaranteed for p(2q3−3q2+1)2+3q2 where q is the least prime factor of (p−1)/6.Finally, we prove, giving explicit constructions, the existence of a cyclic (4, 1)-GDD of type 6p for any prime p5 and the existence of a cyclic (4, 1)-GDD of type 8p for any prime p \equiv 1 \pmod 6. The result on GDD's with group size 6 was already known but our proof is new and very easy.All the above results may be translated in terms of optimal optical orthogonal codes of weight four with λ=1.