High density cellular mobile radio communications

In a mobile communication system for serving a multiplicity of mobile units from a plurality of cell sites each equipped with signal strength measuring apparatus and adapted to process mobile unit signal strength measurements to generate a message including a hand-off candidate list of cell sites and associated channel groups, a method for transferring control of communications with a mobile unit from one cell site to another, comprising the steps of:

• storing in a control data base state indicators specifying which channels are available for use at said cell sites;
• responsive to reception of said message including a hand-off candidate list, selecting one of said available channels associated with a member of said candidate list, using said control data base to determine availability;
• and
• transmitting a hand-off message sequence including the identification of said selected available channel.

In a plural channel mobile communication system for serving mobile units from a plurality of cell sites each equipped with signal strength measuring apparatus and each having one or more antenna/channel groups, a method for transferring control of communications with a mobile unit from one antenna/channel group at one cell site to another antenna/channel group, comprising the steps of:

• storing in a local cell site data base at each of said cell sites first and second lists of nearby cell sites and first and second lists of candidate hand-off antenna/channel groups and associated primary and secondary signal strength thresholds;
• first ascertaining at said one cell site when the signal strength of said mobile unit drops below a primary prespecified threshold;
• responsive to said signal strength ascertaining step, accessing said local cell site data base to obtain said first list of nearby cell sites and transmitting a first command to said signal strength measuring apparatus of said nearby cell sites on said first list to measure and report the signal strength of said mobile unit;
• responsive to the receipt of said reports from said signal strength measuring apparatus of said nearby cell sites on said first list, selecting from said accessed data base first candidate list those antenna/channel groups associated with signal strength reports above said associated primary signal strength threshold;
• responsive to said first selecting step, if said first selecting step selects no antenna/channel groups, further ascertaining at said one cell site whether the signal strength of said mobile unit is below a secondary prespecified threshold;
• and
• responsive to said second ascertaining step, accessing said local cell site data base to obtain said second list of nearby cell sites and transmitting a second command to said signal strength measurement apparatus of said nearby cell sites on said second list to measure and report the signal strength of said mobile unit.

ln a plural channel mobile communication system for serving mobile units from a plurality of cell sites each equipped with signal strength measuring apparatus and each having one or more antenna/channel groups, a method for transferring control of communications with a mobile unit from one antenna/channel group at one cell site to another antenna/channel group, comprising the steps of:

• storing in a data base for said one cell site, first and second lists of nearby cell sites and first and second lists of candidate hand-off antenna/channel groups and associated primary and secondary signal strength thresholds;
• first ascertaining at said one cell site when the signal strength of said mobile unit drops below a primary prespecified threshold;
• responsive to said signal strength ascertaining step, accessing said data base for said one cell site to obtain said first list of nearby cell sites and transmitting a first command to said signal strength measuring apparatus of said nearby cell sites on said first list to measure and report the signal strength of said mobile unit;
• responsive to the receipt of said reports from said signal strength measuring apparatus of said nearby cell sites on said first list, selecting from said accessed data base first candidate list those antenna/channel groups associated with signal strength reports above said associated primary signal strength threshold;
• responsive to said first selecting step, if said first selecting step selects no antenna/channel groups, further ascertaining whether the signal strength of said mobile unit is below a secondary prespecified threshold;
• and
• responsive to said second ascertaining step, accessing said local cell site data base to obtain said second list of nearby cell sites and transmitting a second command to said signal strength measurement apparatus of said nearby cell sites on said second list to measure and report the signal strength of said mobile unit.