Wireless communication handoffs within a macrocell

Abstract

Handoffs within a wireless communication system ( 20 ) include using a common cell definition code for each of a plurality of microcell BTSs ( 30, 40, 50 ) to facilitate handoffs between a macrocell ( 26 ) and any one of the microcells. In a disclosed example, a common cell definition code such as a PN offset or a scrambling code is used to trigger a handoff from the macrocell ( 26 ) to any one of the microcell BTSs ( 30, 40, 50 ). A mobile station locate feature identifies which of the BTSs is involved in the handoff. Another common cell definition code is used in one example to trigger all handoffs from any one of the microcells ( 30, 40, 50 ) to the macrocell ( 26 ). Soft handoff and hard handoff examples are disclosed.

1 . A method of communicating, comprising: 
 using a common cell definition code for a plurality of microcells within a single macrocell to facilitate a handoff between the macrocell and at least one of the microcells.    
   
   
       2 . The method of  claim 1 , comprising 
 using the common cell definition code to facilitate a handoff from the macrocell to at least one of the microcells.    
   
   
       3 . The method of  claim 2 , comprising 
 using a second common cell definition code to facilitate a handoff from at least one of the microcells to the macrocell.    
   
   
       4 . The method of  claim 1 , wherein the microcell definition code comprises at least one of a pseudo random noise offset or a scrambling code.  
   
   
       5 . The method of  claim 1 , wherein each of the microcells corresponds to a building and comprising 
 using a first common cell definition code as an indicator that a mobile station is entering a building; and    using a second common cell definition code as an indicator that a mobile station is exiting a building.    
   
   
       6 . The method of  claim 1 , comprising at least one of 
 maintaining a neighbor list having only one identifier of the macrocell at each of a plurality of base stations serving the plurality of microcells, respectively; or    maintaining a neighbor list at a base station serving the macrocell having the common cell definition code for each of the plurality of microcells within the macrocell as the only entry identifying the entire plurality of microcells.    
   
   
       7 . The method of  claim 1 , comprising 
 determining if a mobile station currently communicating with a base station serving the macrocell detects the common cell definition code;    taking a power measurement from the mobile station at each of the plurality of microcells; and    identifying one of the microcells to which the mobile station should be handed off based upon the taken power measurement.    
   
   
       8 . The method of  claim 7 , comprising 
 determining whether the mobile station detects a corresponding pilot signal strength that exceeds a selected threshold before taking the power measurement.    
   
   
       9 . The method of  claim 7 , comprising 
 receiving a power measurement from the mobile station at only the identified microcell to which the mobile station should be handed off.    
   
   
       10 . The method of  claim 7 , wherein the macrocell and the identified microcell use the same frequency for communicating with the mobile station.  
   
   
       11 . The method of  claim 7 , wherein 
 the plurality of microcells is a first plurality;    there is at least one second plurality of microcells within the macrocell having a second, different common cell definition code;    and comprising    taking the power measurement at only the plurality of microcells corresponding to the common cell definition code detected by the mobile station.    
   
   
       12 . The method of  claim 7 , comprising 
 maintaining a neighbor list for the base station serving the macrocell that does not include the common cell definition code.    
   
   
       13 . The method of  claim 1 , comprising 
 determining if a mobile station currently communicating with a base station serving the macrocell detects the common cell definition code;    locating a reverse pilot signal from the mobile station on a frequency used by the macrocell and the mobile station; and    identifying one of the microcells to which the mobile station should be handed off based upon the located reverse pilot signal.    
   
   
       14 . The method of  claim 13 , comprising 
 transmitting the common cell definition code near an interface between the microcell and the macrocell on the frequency used by the macrocell.    
   
   
       15 . The method of  claim 1 , comprising 
 determining if a mobile station within one of the microcells detects the common cell definition code; and    obtaining a radio frequency measurement report associated with the common cell definition code from the mobile station; and    handing off the mobile station from the one of the microcells to a frequency of the macrocell responsive to the obtained radio frequency measurement report.    
   
   
       16 . The method of  claim 15 , comprising 
 maintaining a neighbor list for a base station serving the microcell that does not include the macrocell; and    mapping at least one cell definition code from the base station serving the microcell to at least one cell definition code of the macrocell for initiating the handoff.    
   
   
       17 . The method of  claim 1 , comprising 
 detecting the common cell definition code when approaching an interface between at least one of the microcells and the macrocell; and    reporting the detected common cell definition code.    
   
   
       18 . The method of  claim 17 , comprising at least one of 
 detecting the common cell definition code when approaching the macrocell from within at least one of the microcells; or    detecting the common cell definition code when approaching at least one of the microcells from within the macrocell.    
   
   
       19 . The method of  claim 17 , comprising 
 responding to a request for at least one of a power measurement or a radio frequency measurement associated with the detected common cell definition code.    
   
   
       20 . The method of  claim 1 , wherein the plurality of microcells comprise in-building wireless service coverage areas.