Mobile phone carriers, including NTT DoCoMo Inc., limited the number of calls that subscribers were allowed to place from late Sunday to early Monday for fear of being swamped with demand as the 21st century began, company officials said.
The KDDI-affiliated au and J-Phone group firms -- among others -- also feared a rush of New Year's greeting calls would exceed their network capacities.
As a result, some subscribers may have experienced difficulty in getting their calls through, the carriers said.
According to industry officials, the number of calls to ring in the new year is increasing with the proliferation of mobile phones. On top of that, more calls were placed this year because it heralded the beginning of a new century, they said.
Mobile carriers were also concerned that their networks would be paralyzed by a rush of e-mail sent via Internet mobile-phone services such as DoCoMo's i-mode.
DoCoMo opted to limit calls so that only one out of every eight placed during the most heavily congested time frame could be placed through some relay stations.
However, the mobile operator said there was nothing wrong with the network itself and that the congestion was likely to abate as time went by.