Project/Area Number  05650356 
Research Category 
GrantinAid for Scientific Research (C).

Research Field 
情報通信工学

Research Institution  Kyushu Institute of Technology 
Principal Investigator 
IMAMURA Kyoki Kyushu Institute of Technology, Professor, 情報工学部, 教授 (60037950)

CoInvestigator(Kenkyūbuntansha) 
UEHARA Satoshi Kyushu Institute of Technology, Assistant, 情報工学部, 助手 (90213389)

Project Fiscal Year 
1993 – 1994

Project Status 
Completed(Fiscal Year 1994)

Budget Amount *help 
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1994 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1993 : ¥1,200,000 (Direct Cost : ¥1,200,000)

Keywords  Pseudonoise sequence / Periodic sequence / Linear Complexity / Maximam Order Complexity / Onesymbol substitution / Onesymbol insertion / Onesymbol deletion / 擬似雑音系列 / complexity評価 / 1記号変更 / 1記号挿入 / 1記号削除 / Linear complexity / Maximum Order Complexity / 周期系列 / 疑似雑音系列 / m系列の最小変更 
Research Abstract 
Psudonoise sequences with large complexity, where complexity means the difficulty in identifying the sequence from its partial information, are essential in spread spectrum communications and stream ciphers. The linear complexity (LC) has been used as a convenient measure. In this reasearch we make a comparison among methods for evaluating complexity of sequences over a finite field from such a point of view as a small change of a sequence must result in a small change of complexity if the complexity is a suitable one. Our main results are 1.Unstable behaviors of LC are made clear for three kinds of minimum changes (onesymbol substitution, onesymbol insertion or onesymbol deletion per one period) of periodic sequences. 2.It is shown that in case of msequences extreme improvements can be made by using maximum order complexity (MOC) instead of LC,where MOC is a generalization of LC to the case of nonlinear difference relation. Further research is desirable on the following problems. 1.to find theoretical methods for evaluating MOC and to generalize the results on msequences to other sequences. 2.to make similar descussions for sequences over a finite ring.
