Oshima;
National;
College;
of;
Maritime;
Technology,;
Yamaguchi;
742-2193,;
Japan,;
Chugoku;
Bureau;
of;
Telecommunications,;
Ministry;
of;
Internal;
Affairs;
and;
Communications,;
Naka-ku.;
Hiroshima;
730-8795,;
Japan;
National;
Institute;
of;
lnformatics,;
Tokyo;
101-8430,;
Japan;