Fremgangsmåte og apparat for datakommunikasjon

摘要

A concept of a virtual master is used in replacing a primary modulation/demodulation system between existing power line modems which are connected on the same power line. More specifically, a power line modem among a plurality of power line modems connected on a power line which has been determined to be "difficult to maintain communications quality communications in the present primary modulation system" becomes the virtual master in primary modulation system replacement processing. Such a virtual master transmits a replacement request command specifying the next primary modulation system to the other power line modems. Then, when there has been no response of a replacement refusal command from the power line modems which received the replacement request command, the virtual master replaces the primary modulation system with the next primary modulation system and transmits a replacement specification command to the other power line modems . Finally, the other power line modems which have received the replacement specification command replace the primary modulation system which they are presently using with the specification primary modulation system.