Abstract:
A mobile wireless terminal is configured to provide an audible alert to the user in the event of its receipt, while the terminal is on a call, of an indication of an imminent or directed handoff to a carrier or network which would charge the user for roaming. The call is automatically terminated or released within a predetermined time period after the audible alert unless the user performs an act of assent, such as pressing a predetermined key, or speaking a predetermined command, before the expiration of the time period.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a wireless terminal; more particularly, to a wireless terminal for use with wireless communications systems of different carriers, network types, or modes. 
   2. Description of the Prior Art 
   It is common for prior art wireless terminals to provide a visual indication, generally of the present roaming status when the terminal is in a standby state. However, such an indication is not generally provided when the terminal is on a call, and even if it were, such a visual indication would not be seen or noticed by the user when the terminal is in active use. Consequently, the user is not generally aware of a change from a non-roaming status to a roaming status which occurs when the terminal is moved through or in the neighborhood of a coverage area boundary while on a call, and is certainly not aware at all of an impending change to roaming status, before the actual change occurs. 
   The change to a roaming status while on a call can be particularly expensive when there is a so-called hard handoff between a digital PCS (Personal Communications Services operating at 1900 MHZ) network of the user&#39;s primary carrier to an analog cellular or AMPS (Analog Mobile Phone System operating at 800 MHZ) network of a secondary carrier that would charge the user as a roamer. In this situation, the user may incur a per minute charge that the user considers excessive, and may also incur an additional per call or per day charge. Such hard handoffs from digital PCS to analog networks while on a call are rather common, because the buildout of PCS networks in the United States is incomplete and primarily existing in densely populated areas. This leads to customer dissatisfaction with the primary PCS carrier as a result of unexpected charges due to roaming. 
   SUMMARY OF THE INVENTION 
   The present invention provides a mobile wireless terminal which provides an audible alert to the user in the event of its receipt, while the terminal is on a call, of an indication of an imminent or directed handoff to a carrier which would charge the user for roaming. The terminal may be configurable to refrain from following a handoff direction or to automatically terminate or release the call within a short predetermined time period after the audible alert unless the user performs an act of assent, such as pressing a predetermined key, or speaking a predetermined command, before the expiration of the time period. 
   In one embodiment a wireless terminal is capable of operating on a network of a primary carrier and one or more networks of secondary carriers, and is switchable from the network of a primary network to a network of a secondary carrier during an existing call in response to a handoff message when the handoff message includes information identifying the carrier or network receiving the handoff, the terminal determines whether the network receiving the handoff would result in incurring additional charges such as roaming. If additional charges will be incurred, the terminal initiates one or more actions, including the sounding of an audible alert. The terminal&#39;s user may actively indicate in response to the audible alert whether the user wishes to continue the call notwithstanding that charges would be incurred. The user may provide a response to the audible alert by pressing a predetermined key, or speaking a predetermined command or utterance. 
   In another embodiment of the invention, the terminal provides a timer that automatically terminates the call after the expiration of a predetermined time period if the call is still active and the user has not indicated that the call is to be continued. 
   In yet another embodiment of the invention, the user may actively terminate the call in response to the audible alert without waiting for the automatic termination that would occur upon expiration of the predetermined time period. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically shows an illustrative plan view of an arrangement of base stations of two different networks, in conjunction with a mobile terminal; 
       FIG. 2  is a schematic of a handset including a programmed digital processing section; and 
       FIG. 3  is a flowchart indicating a process carried out by the digital processing section in accordance with the principles of the present invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a mobile terminal or station MS, a cellular arrangement of spaced apart base stations BS 1  of a first wireless network operated by or for the primary carrier to which mobile station MS is assigned.  FIG. 1  also shows a cellular arrangement of spaced apart second base stations BS 2  of a secondary carrier via which mobile station MS may be on a call, but may incur per minute, and/or per call or per day charges as a roamer. When mobile station is on a call and travels within the confines of the coverage area of one network having base stations BS 1 , so-called soft handoffs are made between base stations to maintain the mobile station communication with the base station having the best signal strength or signal-to-noise ratio as measured by the mobile station MS. This typically results in the mobile station being in communication with the closest base station BS 1 , such as base station  60 . When mobile station is on a call via the nearest  60  of the base station BS 1  of the primary carrier and passes through a boundary B 1  of the coverage area of the arrangement of base stations BS 1 , a handoff to a nearest  70  of the base stations BS 2  of the secondary carrier is necessary in order to maintain the call. 
   Where the handoff is between networks of different types, such as from a digital PCS system operating at 1900 MHZ (digital PCS system may be any digital multiple access type including but not limited to CDMA (Code Division Multiple Access), TDMA (Time Division Multiple Access), and GSM (Global System for Mobile communications)) to an AMPS (Analog Mobile Phone System) system operating at 800 MHZ, the handoff is referred to as a “hard handoff”. Hard handoffs use an Analog Handoff Direction Message (AHDM) to initiate a handoff. The AHDM is sent from base station BS 1   60  with which mobile M is presently communicating to an identified nearest base station BS 2   70  of the secondary analog carrier. The AHDM is also sent to the mobile station. It is this type of handoff that may be particularly troublesome to the user, because there is the possibility, based on inter-carrier agreement, or lack thereof, that the user would be charged for the ongoing call as roaming. Such a roaming charge will typically include a per minute charge, and may also include a per call or per day charge. Absent steps taken to notify the user, preferably prior to the implementation of the directed handoff, the user would be unaware that additional charges were being incurred in the ongoing call. 
   While the invention is equally applicable to digital PCS terminals of the aforementioned different types, for purpose of illustration terminology applicable to CDMA is used in further description herein. 
     FIG. 2  shows a typical digital mobile terminal or station MS and includes an antenna  12  coupled for two way RF communication with a duplexer  14 , which in turn feeds a reception signal path composed of receiver/demodulator  16  and analog to digital converter  18 , and is fed by a transmission signal path composed of modulator/transmitter  20  and digital to analog converter  22 . The converters A/D  18  and D/A  22  are connected to a digital processing section  24  which includes digital signal processor (DSP)  26 , volatile Random Access Memory (RAM)  28 , Central Processing Unit (CPU)  30 , and non-volatile Read-Only Memory (ROM)  32 . Both RAM  28  and ROM  32 , or assigned parts thereof, are accessible to the DSP  26  and CPU  30 , respectively. ROM  32  contains the firmware programs and data used by DSP  26  and CPU  30  and is entirely or at least in part electrically programmable to include various information programmed at the time the mobile station MS is distributed to the user, including identities of the mobile station and of the primary carrier. 
   Among the items so programmed in ROM  32  is a database  33  (SSPR database) identifying systems of carriers with which the primary carrier has a roaming agreement, indexed by System Identifiers (SIDs), which includes a field ROAM_IND indicating whether the user will incur charges as roaming when using that system. 
   Mobile station MS also includes coupled to digital processing module  24 , a display controller  34  which drives a display  36 , which is for example a Liquid Crystal Device (LDC) panel, a digital to analog converter  38  which controls a speaker  40 , an analog to digital converter  42  which is fed from a microphone  44 , a keypad  46 , and a piezoelectric vibration unit  47 . The speaker  40 , in addition to its usual functions may be driven to provide an audible alarm providing a roaming notification to the user in accordance with the principles of the present invention. Keyboard  46 , in addition to its usual functions, may serve as input means for the user, by pressing a first determined key thereof to indicate that the user has elected to continue the call notwithstanding the notification, and to press a second predetermined key thereof to indicate that the user has selected to end the call. Alternatively, spoken commands by the user into microphone  44  may be recognized by digital processing section  24  to indicate the user&#39;s selection among these alternatives. 
     FIG. 3  shows a flowchart implemented by firmware based program instructions to CPU  30  pertaining to an additional call processing instruction module  200  provided in accordance with the principles of the present invention in addition to the usual mobile station controls on traffic channel state  100 , which occur when the mobile station is on a call, and call processing in release substate  102 , which occur when a call has ended. 
   As shown in  FIG. 3 , when an Analog Handoff Direction Message (AHDM) is received by MS control on the traffic channel control state  100 , step  202  of instruction module  200  is reached wherein the SID field in the AHDM is compared with SIDs in the SSPR database. At step  204  it is determined whether this SID is listed in the SSPR database. If not, it is assumed that the user will be charged excessively for roaming and step  206  is reached, wherein the following four actions are initiated: (It should be noted that actions b and/or c and/or d may be omitted from alternative embodiments, and that action d may be used in place of or in addition to action a.)
         a) the audible alert, such as a buzz or beep, is sounded via speaker  40 ;   b) the display  36  presents a prompt to the user of which keys to press to signify a selection to continue or to end the call;   c) a timer formed by CPU  30  is started to time a predetermined period, for example ten seconds;   d) activating a vibrating alert.       

   If, on the other hand, the SID in the AHDM is listed in the SSPR database, then step  205  is reached, wherein the corresponding ROAM_IND field is checked to see if the analog SID meets a predetermined roaming notification criteria, which may be presettable by the user. Such criteria may be defined by whether a maximum per minute charge the user has programmed as acceptable is exceeded, and/or whether an additional per call or per day charge would be incurred exceeding user programmed maximum amounts. If it is determined in step  207  that the criteria for notification of the user are met, then step  206  is reached, which step has already been described. If, on the other hand, it is determined in step  207  that the criteria for notification are not met, then step  100  is returned to in order to continue the control on Traffic Channel State. 
   After step  206 , step  208  is reached where it is tested whether the user has actively selected to continue the call, by pressing a predetermined key of keypad  46  or speaking a predetermined command into microphone  44 . If the user has selected to continue the call then step  100  is returned to, thereby continuing the control on Traffic Channel State. if on the other hand the user has not actively selected to continue the call then step  210  is reached wherein it is tested whether the predetermined or user programmed period timed by the timer has expired or elapsed. 
   If in step  210  it is determined that the predetermined time period has elapsed, then step  212  is reached wherein the call is ended and the MS Release Substate is entered with an MS release indication, after which step  102  is reached in which call processing is resumed in the Release Substate. If, on the other hand, it is determined in step  210  that the predetermined time period has not yet elapsed, then step  214  is reached wherein it is tested whether the user has actively selected to end the call by pressing a different predetermined key of keypad  46  or speaking a different predetermined command into microphone  44 . 
   If in step  214  it is determined that the user has selected to end the call, then step  212  is reached ending the call, etc. If, on the other hand, it is determined in step  214  that the user has not selected to end the call, then step  208  is again reached. It is noted that steps  208 ,  210 , and  214  form a condition monitoring loop  216  which is exited by first satisfying any of the tested conditions. If the first to occur is the user selecting to continue the call, step  100  is reached, whereas if the first to occur is either the predetermined time period of the timer elapsing, or the user selecting to end the call, then step  212 , and ultimately step  102  are reached. 
   It should now be appreciated that the objects of the invention have been satisfied by the foregoing description of the invention. While the present invention has been described in particular detail, it should also be appreciated that numerous modifications are possible within the intended spirit and scope of the invention.