# US 8,571,558 B1 · Mobile communication device initiated hand-off based on air interface metrics > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,571,558 B1 - Document ID: US8571558B1 - Status: Granted - Kind: B1 - Application number: 13/281,427 - Filed: 2011-10-25 - Granted: 2013-10-29 - Earliest claimed: 2008-08-19 - Assignees: Clearwire IP Holdings LLC - Applicants: Esmail Hejazi Dinan; Jong-hak Jung; Swati Tiwari; Hemanth Balaji Pawar; Krishna D. Sitaram - Inventors: Esmail Hejazi Dinan; Jong-hak Jung; Swati Tiwari; Hemanth Balaji Pawar; Krishna D. Sitaram - Web page: https://patentgrep.com/patent/US8571558B1 ## CPC - H04W 36/22: for handling the traffic - H04W 36/302: {due to low signal strength} - H04W 28/18: Negotiating wireless communication parameters - H04W 36/08: Reselecting an access point - H04W 36/36: by user or terminal equipment - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A mobile communication device wirelessly transfers user communications to a first wireless base station. The mobile communication device determines a first metric based on a load indicator for the first base station. The mobile communication device identifies a second wireless base station and determines a second metric based on a load indicator for the second base station. If the second metric is superior to the first metric, the mobile communication device determines if the second base station has sufficient performance characteristics for communication with the device. If the performance is sufficient, the mobile communication device initiates a hand-off from the first base station to the second base station. The mobile communication device may use additional factors to determine the first and second metrics. ## Claims ### Claim 1 A method of operating a mobile communication device comprising: transferring, by the mobile communication device, user communications to a first wireless base station through a wireless communication link; obtaining, by the mobile communication device, a first base station signal strength, a first base station signal-to-noise ratio, and a first base station round trip delay, and determining, by the mobile communication device, a first air interface metric for the first base station based on a combination of the first base station signal strength, the first base station signal-to-noise ratio, and the first base station round trip delay for a signal directly to and from the first base station; identifying, by the mobile communication device, a second wireless base station; obtaining, by the mobile communication device, a second base station signal strength, a second base station signal-to-noise ratio, and a second base station round trip delay, and determining, by the mobile communication device, a second air interface metric for the second base station based on a combination of the second base station signal strength, the second base station signal-to-noise ratio, and the second base station round trip delay for a signal directly to and from the second base station; comparing the first air interface metric to the second air interface metric; determining, by the mobile communication device, whether the second wireless base station has sufficient performance characteristics for wireless communication with the mobile communication device based on at least one of the parameters associated with the combination for determining the second air interface metric, when the second air interface metric is superior to the first air interface metric; and initiating a hand-off from the first wireless base station to the second wireless base station, stopping the wireless transfer of the user communications to the first wireless base station, and wirelessly transferring additional user communications to the second wireless base station, when the second air interface metric is superior to the first air interface metric and the second wireless base station has sufficient performance characteristics. ### Claim 2 (depends on 1) The method of claim 1 wherein: determining the first air interface metric further comprises obtaining a first communication load indicator for the first base station, and the combination for determining the first air interface metric further comprises the first communication load indicator; and determining the second air interface metric further comprises obtaining a second communication load indicator for the first base station, and the combination for determining the second air interface metric further comprises the second communication load indicator. ### Claim 3 (depends on 2) The method of claim 2 wherein: determining the first air interface metric further comprises determining a communication service being provided by the mobile communication device, determining the first base station's quality-of-service for a communication service, and the combination for determining the first air interface metric further comprises first base station's quality-of-service for the communication service; and determining the second air interface metric further comprises determining the second base station's quality-of-service for the communication service and the combination for determining the second air interface metric further comprises the second base station's quality-of-service for the communication service. ### Claim 4 (depends on 3) The method of claim 3 wherein: the combination for determining the first air interface metric further comprises a first base station's current base station priority; and the combination for determining the second air interface metric comprises a second base station's current base station priority. ### Claim 5 (depends on 1) The method of claim 1 wherein identifying the second wireless base station comprises wirelessly receiving a base station list. ### Claim 6 (depends on 1) The method of claim 1 wherein determining whether the second wireless base station has the sufficient performance characteristics for the mobile communication device comprises, in response to determining that the second air interface metric is superior to the first air interface metric, comparing the signal-to-noise ratio to a threshold. ### Claim 7 (depends on 1) The method of claim 1 wherein determining whether the second wireless base station has the sufficient performance characteristics for the mobile communication device comprises, in response to determining that the second air interface metric is superior to the first air interface metric, comparing the second base station signal strength to a threshold. ### Claim 8 A mobile communication device comprising: a wireless communication interface configured to transfer user communications to a first wireless base station through a first wireless communication link and to transfer additional user communications to a second wireless base station through a second wireless communication link; and a processing system configured to: determine a first air interface metric for the first base station based on a first base station signal strength, a first base station signal-to-noise ratio, and a first base station round trip delay for a signal directly to and from the first base station; determine a second air interface metric for the second base station based on a second base station signal strength, a second base station signal-to-noise ratio, and a second base station round trip delay for a signal directly to and from the second base station; determine if the second wireless base station has sufficient performance characteristics for wireless communication with the mobile communication device based on at least one of the parameters associated with the determining the second air interface metric, when the second air interface metric is superior to the first air interface metric; and initiate a hand-off from the first wireless base station to the second wireless base station and direct the wireless communication interface to stop the wireless transfer of the user communications to the first wireless base station and to start the wireless transfer of the additional user communications to the second wireless base station, when the second wireless base station has sufficient performance characteristics and the second air interface metric is superior to the first air interface metric. ### Claim 9 (depends on 8) The mobile communication device of claim 8 wherein the processing system is further configured to determine the first air interface metric based further on a first communication load indicator for the first base station and to determine the second air interface metric based on a second communication load indicator for the second base station. ### Claim 10 (depends on 8) The mobile communication device of claim 8 wherein the processing system is further configured to determine the first air interface metric based further on a first base station's current quality-of-service for a current communication service being provided by the mobile communication device and to determine the second air interface metric based further on a second base station's current quality-of-service for the current communication service being provided by the mobile communication device. ### Claim 11 (depends on 10) The mobile communication device of claim 10 wherein the processing system is further configured to determine the first air interface metric based further on a first base station's current base station priority and to determine the second air interface metric based further on a second base station's current base station priority. ### Claim 12 (depends on 8) The mobile communication device of claim 8 wherein: the wireless communication interface is further configured to wirelessly receive a base station list identifying the second base station; and the processing system is further configured to determine the second air interface metric in response to identifying the second base station on the base station list. ### Claim 13 (depends on 8) The mobile communication device of claim 8 wherein: the processing system is further configured, in response to determining that the second air interface metric is superior to the first air interface metric, to compare the second base station signal-to-noise ratio to a threshold and to determine that the second wireless base station has sufficient performance characteristics for wireless communication with the mobile communication device when the second base station signal-to-noise ratio is higher than the threshold. ### Claim 14 (depends on 8) The mobile communication device of claim 8 wherein: the processing system is further configured, in response to determining that the second air interface metric is superior to the first air interface metric, to compare the second base station signal strength to a threshold and to determine that the second wireless base station has sufficient performance characteristics for wireless communication with the mobile communication device when the second base station signal strength is higher than the threshold.