Hand-off between ultra-wideband cell sites

Abstract

Briefly, the present invention provides a dynamic channel re-assignment capability between mobile units, base stations and sectors within base station coverage areas. The wireless devices used in the present invention may include ultra-wideband radio communication devices. Ultra-wideband bandwidth and channel allocation can be effectively managed, even though link quality generally deteriorates near the outer boundary of the base station. By maintaining dual communications with an adjoining base station, the present invention reduces the bit error rate and maintains signal strength.

1 . A method for performing a soft hand-off in an ultra-wideband cellular communication system, comprising the steps of: 
 monitoring signal strength and the bit error rate from a primary source;    monitoring signal strength and the bit error rate from a secondary source;    comparing the strength of the signal and the bit error rate from the primary source to the strength of the signal and the bit error rate from the secondary source or to predetermined levels; and    transferring data reception and transmission from the primary source to the secondary source when the strength of the signal from the secondary source is greater than the strength of the signal of the primary source or when the bit error rate of the secondary source is less than the bit error rate of the primary source or when either signal strength or bit error rate is below a pre-determined level.    
     
     
         2 . The method of  claim 1 , wherein the step of monitoring signal strength and bit error rate from the primary source is performed for at least about 0.5 seconds.  
     
     
         3 . The method of  claim 1 , wherein the step of monitoring signal strength and bit error rate from the secondary source is performed for at least about 0.5 seconds.  
     
     
         4 . The method of  claim 1 , wherein the step of monitoring is performed by a mobile unit and/or a base station.  
     
     
         5 . The method of  claim 1 , wherein the bit error rate is about 10 −3 .  
     
     
         6 . The method of  claim 1 , wherein the bit error rate is about 10 −5 .  
     
     
         7 . The method of  claim 1 , wherein the bit error rate is about 10 −10 .  
     
     
         8 . The method of  claim 1 , wherein the primary source and the secondary source are base stations, wherein the base stations have a hexagonal topology configuration with overlapping coverage; wherein a single base station is connectable to six other base stations for handoff and channel coordination.  
     
     
         9 . The method of  claim 1 , wherein the primary source is a base station, wherein the secondary source is a base station, and wherein each base station is sub-divided into six coverage sectors.  
     
     
         10 . The method of  claim 1 , wherein a base station completes a soft hand-off when a mobile unit moves from one sector to another sector.  
     
     
         11 . The method of  claim 1 , wherein the hand-off is from a base station to a receiving base station to a mobile unit.  
     
     
         12 . The method of  claim 1 , wherein the primary source is a base station, wherein the secondary source is a base station, and wherein each base station is linked to a plurality of mobile units.  
     
     
         13 . The method of  claim 1 , wherein the soft hand-off is from a mobile unit to a first base station to a second base station, wherein: 
 the mobile unit is linked to the first base station and detects an increase in bit error rate and/or a reduction in signal strength;    the mobile unit sends a request to the first base station for a hand-off;    the first base station receives the request, selects the second base station and contacts the second base station to request an initial hand-off sequence;    the second base station acknowledges the request for an initial hand-off sequence;    the second base station contacts the mobile unit, provides a channel assignment to the mobile unit and links to the mobile unit;    the mobile unit transmits a hand-off release request to the first base station; and    the first base station releases the mobile unit, and thereby completes the soft hand-off.    
     
     
         14 . A computer program product for performing a soft hand-off in an ultra-wideband code-based cellular communication system, comprising: 
 computer code for monitoring signal strength and the bit error rate from a primary source; computer code for monitoring signal strength and the bit error rate from a secondary source;    computer code for comparing the strength of the signal and the bit error rate from the primary source to the strength of the signal and the bit error rate from the secondary source or to predetermined levels; and    computer code for transferring data reception and transmission from the primary source to the secondary source when the strength of the signal from the secondary source is greater than the strength of the signal of the primary source or when the bit error rate of the secondary source is less than the bit error rate of the primary source or when either signal strength or bit error rate is below a pre-determined level.    
     
     
         15 . The computer program product of  claim 14 , wherein the soft hand-off is from a mobile unit to a first base station to a second base station, wherein: 
 the mobile unit is linked to the first base station and detects an increase in bit error rate and/or a reduction in signal strength; the mobile unit sends a request to the first base station for a hand-off; the first base station receives the request, selects the second base station and contacts the second base station to request an initial hand-off sequence;    the second base station acknowledges the request for an initial hand-off sequence, the second base station contacts the mobile unit, provides a channel assignment to the mobile unit and links to the mobile unit, the mobile unit transmits a hand-off release request to the first base station; and    the first base station releases the mobile unit, and thereby completes the soft hand-off.    
     
     
         16 . The computer program product of  claim 15 , wherein the channel comprises at least one of a sequence code in a code-division multiple access (CDMA) scheme, and an ultra-wideband radio channel.  
     
     
         17 . A base station for an ultra-wideband code based cellular communication system comprising: 
 means for monitoring signal strength and the bit error rate from the base station, which serve as a primary source:    means for comparing the strength of the signal and the bit error rate from the primary source to predetermined levels; and    means for transferring data reception and transmission to a secondary source.    
     
     
         18 . The base station of  claim 17 , wherein the soft hand-off is from a mobile unit to the base station to a second base station, wherein: 
 the mobile unit is linked to the base station and detects an increase in bit error rate and/or a reduction in signal strength;    the mobile unit sends a request to the base station for a hand-off;    the base station receives the request, selects the second base station and contacts the second b as e station to request an initial hand-off sequence;    the second base station acknowledges the request for an initial hand-off sequence;    the second base station contacts the mobile unit, provides a channel assignment to the mobile unit and links to the mobile unit;    the mobile unit transmits a hand-off release request to the base station; and    the base station releases the mobile unit, and thereby completes the soft hand-off.