Methods and apparatus for performing handoff based on the mobility of a subscriber station
View Patent ↗In a wireless communication system, a mobility factor is used to influence handoff. If a subscriber station has been in a low mobility state for some period of time, the system may handoff operation from a first service type to a second service type. If the mobility factor indicates that the subscriber station is moving, the system may handoff operation from the second service type back to the first service type.
1. A method of handoff in a wireless system having a base station that communicates with a subscriber station, the method comprising:
establishing, at the base station, a service with the subscriber station in a licensed spectrum;
determining, at the base station, a first value of a mobility factor indicative of a relative motion of the subscriber station;
transferring, at the base station, the service from the licensed spectrum to a non-licensed spectrum associated with the base station if the first value of the mobility factor indicates that the subscriber station has been in a low mobility state for at least a predetermined period of time.
2. A subscriber station comprising:
a front end module configured to establish a service with a base station in a licensed spectrum; and
a mobility monitoring module configured to:
determine a first value of a mobility factor indicative of a relative motion of the subscriber station communicating using the licensed spectrum; and
determine an availability of the service from the base station via a non-licensed spectrum; and
wherein the front end module is further configured to initiate transfer of the service to the non-licensed spectrum associated with the base station if the first value of the mobility factor indicates that the subscriber station has been in a low mobility state for at least a predetermined period of time.
3. The method of claim 1 , further comprising: receiving, at the base station, the first value of the mobility factor from the subscriber station.
4. The method of claim 1 , wherein at least one value of the mobility factor is based, at least in part, on correlating pilot signals of at least two distinct Orthogonal Frequency Division Multiplex (OFDM) symbols separated by a time offset.
5. The method of claim 1 , wherein at least one value of the mobility factor is based, at least in part, on a change in a frequency offset relative to a desired receive frequency over a time period by determining a product of symbol samples from an Orthogonal Frequency Division Multiplex (OFDM) symbol with corresponding samples from a cyclic prefix from the OFDM symbol.
6. The method of claim 1 , wherein at least one value of the mobility factor is based, at least in part, on a change in an average power of received Orthogonal Frequency Division Multiplex (OFDM) symbols.
7. The method of claim 1 , wherein at least one value of the mobility factor is a composite mobility factor based, at least in part, on a quantized combination of a plurality of distinct mobility factors.
8. The method of claim 1 , wherein at least one value of the mobility factor indicates one of a limited number of discrete mobility states.
9. The method of claim 1 , wherein at least one value of the mobility factor is based, at least in part, on a wireless signal received by the subscriber station.
10. The method of claim 9 , further comprising:
determining an operating state based at least in part on information carried on the wireless signal,
wherein at least one mobility factor is based, at least in part, on the operating state.
11. The subscriber station of claim 2 , wherein the front end module is further configured to transmit a scan request message to the base station to determine the availability of the service via non-licensed spectrum.
12. The subscriber station of claim 2 , wherein the mobility monitoring module is further configured to determine a second value of the mobility factor indicative of relative motion of the subscriber station communicating using the non-licensed spectrum, and wherein the front end module is further configured to initiate transfer of the service to the licensed spectrum associated with the base station if the second value of the mobility factor indicates that the subscriber station has been in a high mobility state for at least a second predetermined period of time.
13. A subscriber station comprising:
a front end module configured to establish a service with a base station via a non-licensed spectrum;
a mobility monitoring module configured to:
determine a first value of a mobility factor indicative of a relative motion of the subscriber station communicating using the non-licensed spectrum; and
determine an availability of the service from the base station via a licensed spectrum; and
wherein the front end module is further configured to initiate transfer of the service to the licensed spectrum associated with the base station if the first value of the mobility factor indicates that the subscriber station has been in a high mobility state for at least a predetermined period of time.
14. The subscriber station of claim 13 , wherein the mobility monitoring module is further configured to determine a second value of the mobility factor indicative of relative motion of the subscriber station communicating using the licensed spectrum, and wherein the front end module is further configured to initiate transfer of the service to the non-licensed spectrum associated with the base station if the second value of the mobility factor indicates that the subscriber station has been in a low mobility state for at least a second predetermined period of time.
15. The subscriber station of claim 13 , wherein the front end module is further configured to transmit a scan request message to the base station to determine the availability of the service via licensed spectrum.
16. A method of handoff in a wireless system having a base station that communicates with a subscriber station, the method comprising:
establishing, at the base station, a service with the subscriber station in a non-licensed spectrum;
determining, at the base station, a first value of a mobility factor indicative of a relative motion of the subscriber station;
transferring, at the base station, the service from the non-licensed spectrum to a licensed spectrum associated with the base station if the first value of the mobility factor indicates that the subscriber station has been in a high mobility state for at least a predetermined period of time.
17. The method of claim 15 , further comprising:
determining, at the base station, a second value of the mobility factor inidicative of the relative motion of the subscriber station; and
transferring, at the base station, the service from the licensed spectrum to the non-licensed spectrum associated with the base station if the second value of the mobility factor indicates that the subscriber station has been in a low mobility state for at least a second predetermined period of time.
18. The method of claim 1 , further comprising:
determining, at the base station, a second value of the mobility factor inidicative of the relative motion of the subscriber station; and
transferring, at the base station, the service from the non-licensed spectrum to the licensed spectrum associated with the base station if the second value of the mobility factor indicates that the subscriber station has been in a high mobility state for at least a second predetermined period of time.