Method and system of handover based on channel quality and loading
View Patent ↗A base station may decide to initiate a handover of a communication with a mobile station from a first wireless link to a new wireless link and identify one or more wireless links for the handover. For each identified wireless link, the base station may then determine a channel-quality metric, a wireless-link loading metric, and perhaps a coverage-area loading metric. In turn, the base station may then select the new wireless link based on the channel-quality metric and one or both of the wireless-link loading metric and the coverage-area loading metric. For example, the base station may apply a linear function that includes as variables the channel-quality metric and the wireless-link loading metric, and the base station may select the identified wireless link that best satisfies this function. The base station may then facilitate the handover of the communication from the first wireless link to the selected new wireless link.
1. A method of handing over a communication with a mobile station between wireless links of an access network, the method comprising:
an access network deciding to initiate a handover of a communication with a mobile station from a first wireless link to a new wireless link;
the access network identifying a plurality of wireless links available for the handover, wherein the plurality of wireless links includes at least one wireless link serving a coverage area that is also served by one or more other wireless links;
for each identified wireless link, the access network (a) determining a channel-quality metric that indicates a channel quality of the identified wireless link and a wireless-link loading metric that indicates a loading of the identified wireless link and (b) applying a linear function that takes the form of −aQ WL +bL WL ≦c, wherein Q WL is the channel-quality metric, L WL is the wireless-link loading metric, and a, b, and c are configurable parameters;
the access network selecting the new wireless link based on the application of the linear function for each identified wireless link; and
the access network facilitating the handover of the communication from the first wireless link to the selected new wireless link.
2. The method of claim 1 , wherein deciding to initiate a handover of the communication from the first wireless link to a new wireless link comprises deciding to initiate a handover of the communication from the first wireless link to a new wireless link in response to the access network receiving a handover request from the mobile station.
3. The method of claim 1 , wherein deciding to initiate a handover of the communication from the first wireless link to a new wireless link comprises deciding to initiate a handover of the communication from the first wireless link to a new wireless link in response to the access network determining that the first wireless link is overloaded.
4. The method of claim 1 , wherein the channel-quality metric comprises a carrier-to-interference noise ratio received from the mobile station.
5. The method of claim 1 , wherein the wireless-link loading metric for each identified wireless link comprises an average percentage of assigned resources to total resources on the identified wireless link.
6. The method of claim 1 , wherein the configurable parameters are selected based on a frequency with which the mobile station changes coverage areas of the access network.
7. The method of claim 1 , wherein the first base station selecting the new wireless link based on the application of the linear function for each wireless link comprises:
selecting, as the new wireless link, the identified wireless link that best satisfies the linear function.
8. The method of claim 1 , further comprising:
before selecting the new wireless link based on the application of the linear function for each wireless link, the access network eliminating from consideration any identified wireless link having one or both of a channel-quality metric below a first threshold and a wireless-link loading metric above a second threshold.
9. A method of handing over a communication with a mobile station between wireless links of an access network, the method comprising:
an access network deciding to initiate a handover of a communication with a mobile station from a first wireless link to a new wireless link;
the access network identifying a plurality of wireless links available for the handover, wherein the plurality of wireless links includes at least one wireless link serving a coverage area that is also served by one or more other wireless links;
for each identified wireless link, the access network determining a channel-quality metric that indicates a channel quality of the identified wireless link, a wireless-link loading metric that indicates a loading of the identified wireless link, and a coverage-area loading metric that indicates a loading of the coverage area served by the identified wireless link;
the access network assigning a priority level to each identified wireless link based on the coverage-area loading metric for the identified wireless link;
for each identified wireless link having been assigned a highest priority level, the access network applying a linear function that takes the form of −aQ WL +bL WL ≦c, wherein Q WL is the channel-quality metric, L WL is the wireless-link loading metric, and a, b, and c are configurable parameters;
the access network selecting the new wireless link based on the application of the linear function for each identified wireless link having been assigned the highest priority level;
and the access network facilitating the handover of the communication from the first wireless link to the selected new wireless link.
10. The method of claim 9 , wherein deciding to initiate a handover of the communication from the first wireless link to a new wireless link comprises deciding to initiate a handover of the communication from the first wireless link to a new wireless link in response to the access network receiving a handover request from the mobile station.
11. The method of claim 9 , wherein deciding to initiate a handover of the communication from the first wireless link to a new wireless link comprises deciding to initiate a handover of the communication from the first wireless link to a new wireless link in response to the access network determining that the first wireless link is overloaded.
12. The method of claim 9 , wherein the channel-quality metric for each identified wireless link comprises a carrier-to-interference noise ratio received from the mobile station.
13. The method of claim 9 , wherein the wireless-link loading metric for each identified wireless link comprises an average percentage of assigned resources to total resources on the identified wireless link.
14. The method of claim 9 , wherein the coverage-area loading metric for a given identified wireless link serving a given coverage area that is also served by one or more other wireless links comprises a combination of the wireless-link metric for the given identified wireless link and a respective wireless-link metric for each of the one or more other wireless links.
15. The method of claim 9 wherein the configurable parameters are selected based on a frequency with which the mobile station changes coverage areas.
16. The method of claim 9 , further comprising:
before assigning a priority level to each identified wireless link based on the coverage-area loading metric for the identified wireless link, eliminating from consideration any identified wireless link having one or more of a channel-quality metric below a first threshold, a wireless-link loading metric above a second threshold, and a coverage-area loading metric above a third threshold.
17. A base station comprising:
an antenna structure for communicating with one or more mobile stations operating in an access network over at least a first wireless link;
a communication interface for communicating with one or more entities in an access network;
a processor;
data storage; and
program instructions stored in the data storage and executable by the processor for:
deciding to initiate a handover of a communication with a mobile station from the first wireless link to a new wireless link of the access network;
identifying a plurality of wireless links available for the handover, wherein the plurality of wireless links includes at least one wireless link serving a coverage area that is also served by one or more other wireless links;
for each identified wireless link, (a) determining channel-quality metric that indicates a channel quality of the identified wireless link and a wireless-link loading metric that indicates a loading of the identified wireless link and (b) applying a linear function that takes the form of −aQ WL +bL WL ≦c, wherein Q WL is the channel-quality metric, L WL is the wireless-link loading metric, and a, b, and c are configurable parameters;
selecting the new wireless link based on the application of the linear function for each identified wireless link; and
facilitating the handover of the communication from the first wireless link to the selected new wireless link.