Method and apparatus for coordinating transmission of short messages with hard handoff searches in a wireless communications system

Abstract

A method and apparatus for coordinating the time at which a mobile station performs searches for alternative systems to which a hard handoff will occur. The mobile station receives a command which instructs the mobile station as to when to tune to alternative frequencies in order to search for indicates of the presence of an alternative system. In another system which includes the present invention, predetermined times are defined with respect to a reference point in time that is common to both the origination base station and a mobile station. The mobile station tunes to alternative frequencies to perform searches only during these predetermined times. In addition, the mobile station coordinates the transmission of reports, which indicate the results of searches for alternative systems such that these reports are only transmitted from the mobile station when the mobile station is tuned to the origination frequency.

We claim:  
     
         1 . A method for coordinating times at which a mobile station monitors alternative frequencies with times at which an origination base station transmits short messages, comprising the steps of: 
 a) determining at an origination base station when a mobile station will be tuned to receive frequencies other than an origination frequency; and    b) transmitting short messages only at times when the mobile station is known to be tuned to receive the origination frequency based on the knowledge of when the mobile station will be tuned to frequencies other than the origination frequency.    
     
     
         2 . The method of  claim 1 , wherein the step of determining when the mobile station will be tuned to frequencies other than the origination frequency includes sending a message which commands the mobile station to tune to a frequency other than the origination frequency at a particular time.  
     
     
         3 . The method of  claim 1 , wherein the step of determining when the mobile station will be tuned to frequencies other than the origination frequency includes sending a message which commands the mobile station to tune to a frequency other than the origination frequency at any time within a particular period in time.  
     
     
         4 . A method for coordinating times at which a mobile station monitors alternative frequencies with times at which an origination base station transmits short messages, comprising the steps of: 
 a) receiving commands from the origination base station indicating when the mobile station can be tuned to receive frequencies other than an origination frequency; and    b) selecting times during which the mobile station will be tuned to frequencies other than the origination frequency based upon the commands received from the origination base station.