Asymptotically-tight bounds on the number of cycles in generalized de Bruijn-Good graphs

Asymptotically-tight bounds on the number of cycles in generalized de Bruijn-Good graphs

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Article ID: iaor1993644
Country: Netherlands
Volume: 37/38
Issue: 1/5
Start Page Number: 421
End Page Number: 436
Publication Date: Jul 1992
Journal: Discrete Applied Mathematics
Authors:
Abstract:

The number of cycles of length k that can be generated by q-ary n-stage feedback shift registers is studied. This problem is equivalent to finding the number of cycles of length k in the natural generalization, from binary to q-ary digits, of the so-called de Bruijn-Good graphs. The number of cycles of length k in the q-ary graph equ1of order n is denoted by equ2. Known results about equ3are summarized and extensive new numerical data is presented. Lower and upper bounds on equ4are derived showing that, for large k, virtually all q-ary cycles of length k are contained in equ5for equ6, but virtually none of these cycles is contained in equ7for equ8. More precisely, if equ9denotes the total number of q-ary lenth-k cycles, then for any function f(k) that grows without bounds as equ10(e.g. equ11), the bounds obtained on equ12are asymptotically tight in the sense that they imply equ13for equ14, and equ15for equ16, where equ17denotes the integer part of the enclosed number. Finally, some approximations for equ18are given that make the global behaviour of equ19more transparent.

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