Idle channel retrieving method and cordless communications system using the same

A cordless communication system comprising:

• a plurality of cordless communication devices;
• a plurality of connection units which couple said cordless communication devices and communication lines;
• and
• a control unit which controls connection between said connection units and said cordless communication devices;
• a plurality of channels between said cordless communication devices and said connection units;
• said control unit comprising:
• means for periodically supervising all connection units and determining which connection units are idle;
• retrieval range specifying means for specifying different channel retrieving ranges within which connection units which are idle respectively retrieve idle channels so that said connection units which are idle operate together to share a retrieval procedure for retrieving idle channels from all the channels in the system;
• and
• control means for controlling said connection units so that said connection units which are idle retrieve idle channels within their respective channel retrieving ranges specified by said retrieval range specifying means.

A method for retrieving an idle channel in a system having a plurality of cordless communication devices, a plurality of connection units which couple said cordless communication devices to communication lines, and a control unit controlling said connection units, said system having a plurality of channels between said cordless communication devices and said connection units, said method comprising the steps of:

• periodically supervising all connection units and determining which connection units are idle;
• specifying, under control of said control unit, different channel retrieving ranges within which connection units which are idle respectively retrieve idle channels so that said connection units which are idle operate together to share a retrieval procedure for retrieving idle channels from all the channels in the system;
• causing said connection units which are idle to retrieve idle channels within their respective channel retrieving ranges;
• creating a map indicating which channels are idle;
• and
• specifying one of said idle channels in response to a connection request from one of the connection units while referring to said map.

A cordless communication system comprising:

• a plurality of cordless communication devices;
• a plurality of connection units which couple said cordless communication devices and communication lines;
• a control unit which controls connection between said connection units and said cordless communication devices;
• and
• a plurality of channels between said cordless communication devices and connection units,
• said control unit comprising:
• means for periodically supervising all connection units and determining which connection units are idle,
• retrieval range specifying means for specifying different channel retrieving ranges within which connection units which are idle respectively retrieve idle channels so that said connection units which are idle operate together to share a retrieval procedure for retrieving idle channels from all the channels in the system,
• control means for controlling said connection units so that said connection units which are idle retrieve idle channels within their respective channel retrieving ranges specified by said retrieval range specifying means,
• map creating means for creating a map indicating which channels are idle,
• memory means for storing said map, and
• idle channel specifying means for specifying one of said idle channels in response to a connection request from one of the connection units while referring to said map.