Frequency Band Selection Methods and Apparatus
AssigneeTelefonaktiebolaget L M Ericsson (publ)
InventorsBela Rathonyi, Ali G. Nader
Life of this patent
Estimating the term…
Abstract
To avoid problems caused by conventional cell search algorithms, a user equipment in a mobile communication system uses knowledge of its previous geographical position and travel times together with stored information on frequency band allocations to determine the frequency band(s) it should search when it is in an out-of-service state, which can result from loss of radio coverage or from power-off.
Claims25
A method of determining a frequency band in which to search for a cell in a communication system having plural cells, wherein the method is carried out in a user equipment (UE) in the communication system, and comprises the steps of:
- checking for a cell at a frequency in a frequency band, the frequency being a frequency on which the UE previously had service from the communication system;
- if a cell is not found at the frequency, carrying out the steps of:
- determining a current location indicator, wherein determining the current location indicator comprises:
- either determining a current location based on signals transmitted in a global positioning system, or
- retrieving a stored time indicator that indicates a time at which the UE previously had service and a stored location indicator that indicates a location of the UE at the time at which the UE previously had service, determining an elapsed time since the time at which the UE previously had service, and determining at least one possible location based on the elapsed time and a set of shortest flying times from the location of the UE at the time at which the UE previously had service;
- and
- determining at least one frequency band in which to search for a cell based on the current location indicator.
An apparatus in a user equipment (UE) for determining a frequency band in which to search for a cell in a communication system having plural cells, the apparatus comprising:
- a device configured to check for a cell at a frequency in a frequency band, the frequency being a frequency on which the UE previously had service from the communication system;
- and
- a processor configured, if a cell is not found at the frequency, to determine a current location indicator either by determining a current location based on signals transmitted in a global positioning system or by retrieving a stored time indicator that indicates a time at which the UE previously had service and a stored location indicator that indicates a location of the UE at the time at which the UE previously had service, determining a current location indicator based on an elapsed time since the time at which the UE previously had service and at least one possible location based on the elapsed time and a set of shortest flying times from the location of the UE at the time at which the UE previously had service;
- and to determine at least one frequency band in which to search for a cell based on the current location indicator.
A computer-readable medium having stored instructions that, when executed by a computer, cause the computer to perform a method of determining a frequency band in which to search for a cell in a communication system having plural cells, wherein the method is carried out in a user equipment (UE) in the communication system, the method comprising the steps of:
- checking for a cell at a frequency in a frequency band, the frequency being a frequency on which the UE previously had service from the communication system;
- if a cell is not found at the frequency, carrying out the steps of:
- determining a current location indicator, wherein determining the current location indicator comprises:
- either determining a current location based on signals transmitted in a global positioning system, or
- retrieving a stored time indicator that indicates a time at which the UE previously had service and a stored location indicator that indicates a location of the UE at the time at which the UE previously had service, determining an elapsed time since the time at which the UE previously had service, and determining at least one possible location based on the elapsed time and a set of shortest flying times from the location of the UE at the time at which the UE previously had service;
- and
- determining at least one frequency band in which to search for a cell based on the current location indicator.
Dependencies are inferred from the claim text.