Wireless communication handoffs within a macrocell
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, wherein each of the microcells corresponds to a building;
determining if a mobile station currently communicating with a base station serving the macrocell detects the common cell definition code;
commanding respective base stations of the plurality of microcells to request a power measurement from the mobile station after determining that the mobile station detected the common cell definition code;
taking the requested power measurement from the mobile station at each of the plurality of microcells;
receiving the power measurement from the mobile station at only one of the microcells;
identifying the only one of the microcells that received the power measurement as the microcell to which the mobile station should be handed off;
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.
2. The method of claim 1 , comprising
initiating a handoff from the macrocell to the only 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 , 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.
6. The method of claim 1 , comprising
determining whether the mobile station detects a corresponding pilot signal strength that exceeds a selected threshold before taking the power measurement.
7. The method of claim 1 , wherein the macrocell and the identified microcell use the same frequency for communicating with the mobile station.
8. The method of claim 1 , 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.
9. The method of claim 1 , comprising
maintaining a neighbor list for the base station serving the macrocell that does not include the common cell definition code.
10. The method of claim 1 , wherein the plurality of microcells comprise in-building wireless service coverage areas.
11. 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, wherein the plurality of the microcells respectively correspond to a building;
determining if a mobile station currently communicating with a base station serving the macrocell detects the common cell definition code;
after determining that the mobile station detected the common cell definition code, using respective base stations of the plurality of microcells to locate a reverse pilot signal from the mobile station by tuning to an uplink frequency used by the macrocell and the mobile station;
detecting the reverse pilot signal at only one of the microcells;
identifying the only one of the microcells as the microcell to which the mobile station should be handed off;
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.
12. The method of claim 11 , comprising
transmitting the common cell definition code near an interface between the microcell and the macrocell on the frequency used by the macrocell.
13. The method of claim 11 , comprising
initiating a handoff from the macrocell to the only one of the microcells.
14. The method of claim 11 , comprising
using a second common cell definition code to facilitate a handoff from at least one of the microcells to the macrocell.
15. The method of claim 11 , wherein the microcell definition code comprises at least one of a pseudo random noise offset or a scrambling code.
16. The method of claim 11 , 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.
17. The method of claim 11 , 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 the method comprises
taking the power measurement at only the plurality of microcells corresponding to the common cell definition code detected by the mobile station.
18. The method of claim 11 , comprising
maintaining a neighbor list for the base station serving the macrocell that does not include the common cell definition code.