Mobile earth terminal communication device providing voice, data, facsimile, and/or roaming communication features

• US 5,815,809 A
• Filed: 04/16/1996
• Issued: 09/29/1998
• Est. Priority Date: 04/16/1996
• Status: Expired due to Fees

• Current Assignee: ATC Technology Corporation (FedEx Corporation)
• Original Assignee: Amsc Subsidiary Corp. (PetIQ, Inc.)
• Inventors: Ross, David J., Ward, Michael K., Churan, Gary G., Tisdale, William R.
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US08/634,305
• Time in Patent Office: 896 Days
• Field of Search: 455/12.1, 455/13.1, 455/33.1, 455/33.3, 455/33.4, 455/54.2, 455/56.1, 455/428, 455/432, 455/524, 455/562, 374/59, 374/100, 374/100.17, 342/352, 342/354
• US Class Current: 455/428
• CPC Class Codes: H04B 7/18567 Arrangements for providing additional services to the basic mobile satellite telephony service
• CPC Class Codes: H04B 7/18571 for satellites; for fixed or mobile stations

Abstract

In a mobile satellite system, a mobile communication system includes a user interface system, an antenna system, a transceiver system, a logic and signaling system. The logic and signaling system provides a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service. The mobile communication system also includes a digital terminal equipment unit initiating setup and release for a data call, and a facsimile interface unit initiating setup and release for a facsimile call. The facsimile interface unit generates a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel. The facsimile interface unit includes a look ahead buffer to perform early line control packet detection by looking ahead a predetermined time interval into a received satellite data stream and identifying a valid idle line control packet.

Claims

1. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising:

a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system;

an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, said antenna system including

an antenna including one of a directional and an omnidirectional configuration, a diplexer, a low noise amplifier, a beam steering unit when said antenna is of the directional configuration, and at least one of a compass and sensor to determine vehicle orientation,

a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter,

the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data,

the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data;

a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating a received signaling messages and generating codes for a signaling message to be transmitted,

said logic and signaling system providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service, wherein upon the loss of the primary service the mobile communication system waits for a first time interval before attempting to register in the alternate service and when the primary service is recovered prior to the expiration of the first time interval, the mobile communication system will not attempt to register with the alternate service,

wherein when the mobile communication system registers on the alternate service, the mobile communication system will wait a second time interval and continuously monitor the availability of the primary service, and when the primary service becomes satisfactorily available, the mobile communication system will attempt to return the registration to the primary service,

wherein when the primary service is subsequently lost a second time, the mobile communication system will wait a third time interval before attempting to register in the alternate service, and when the primary service is recovered prior to the expiration of the third time interval, the mobile communication system will not attempt registration in the alternate service,

wherein when the mobile communication system registers on the alternate service after the primary service is subsequently lost two times, the mobile communication system waits a fourth time interval and continuously monitors the availability of the primary service and when the primary service becomes satisfactorily available, the mobile communication system will attempt to return the registration to the primary service,

wherein when the primary service is subsequently lost a three or more times, the mobile communication system will wait a fifth time interval before attempting to register in the alternate service, and when the primary service is recovered prior to the expiration of the fifth time interval, the mobile communication system will not attempt registration in the alternate service,

wherein when the mobile communication system registers on the alternate service after the primary service is subsequently lost three or more times, the mobile communication system waits a sixth time interval and continuously monitors the availability of the primary service and when the primary service becomes satisfactorily available, the mobile communication system will attempt to return the registration to the primary service,

wherein when the mobile communication system has invoked any reregistration, a timer will be started for a seventh time interval, the timer being reset for each reregistration, and when the seventh time interval expires, the reregistration delay will be set to the first time interval, and when both the primary and alternate services are lost, the mobile communication system continuously monitors the primary and alternate services, and attempts to register on whichever of the primary and alternate services that is satisfactorily available first; and

power supply means for providing power to the mobile communication system.

2. The mobile communication system according to claim 1, wherein the first and second time intervals are shorter than the third and fourth time intervals, and the third and fourth time intervals are shorter than the fifth and sixth time intervals, and the fifth and sixth time intervals are shorter than the seventh time interval.

3. The method according to claim 2, wherein the first and second time intervals are shorter than the third and fourth time intervals, and the third and fourth time intervals are shorter than the fifth and sixth time intervals, and the fifth and sixth time intervals are shorter than the seventh time interval.

4. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system, an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter, the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data, the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data and a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating received signaling messages and generating codes for a signaling message to be transmitted, a method of providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service, said method comprising the steps of:

(a) determining whether the primary service has been lost a first time;

(b) waiting a first time interval before attempting to register in the alternate service when the primary service is lost the first time;

(c) when the primary service is recovered prior to the expiration of the first time interval, not attempting to register with the alternate service;

(d) when the mobile communication system registers on the alternate service, waiting a second time interval and continuously monitoring the availability of the primary service, and when the primary service becomes satisfactorily available, attempting to register on the primary service;

(e) when the primary service is subsequently lost a second time, waiting a third time interval before attempting to register in the alternate service, and when the primary service is recovered prior to the expiration of the third time interval, not attempting registration in the alternate service;

(f) when the mobile communication system registers on the alternate service after the primary service is subsequently lost two times, waiting a fourth time interval and continuously monitoring the availability of the primary service and when the primary service becomes satisfactorily available attempting to return the registration to the primary service;

(g) when the primary service is subsequently lost a three or more times, waiting a fifth time interval before attempting to register in the alternate service, and when the primary service is recovered prior to the expiration of the fifth time interval, not attempting registration in the alternate service;

(h) when the mobile communication system registers on the alternate service after the primary service is subsequently lost three or more times, waiting a sixth time interval and continuously monitoring the availability of the primary service and when the primary service becomes satisfactorily available, attempting to return the registration to the primary service;

(i) when the mobile communication system has invoked any reregistration, starting a timer for a seventh time interval, and resetting the timer for each reregistration,

(j) when the seventh time interval expires, setting the reregistration delay to the first time interval;

(k) when both the primary and alternate services are lost, continuously monitoring the primary and alternate services, and attempting to register on whichever of the primary and alternate services that is satisfactorily available first.

5. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising:

a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system;

an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, said antenna system including

an antenna including one of a directional and an omnidirectional configuration, a diplexer, a low noise amplifier, a beam steering unit when said antenna is of the directional configuration, and at least one of a compass and sensor to determine vehicle orientation,

a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter,

the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data,

the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data;

a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating a received signaling messages and generating codes for a signaling message to be transmitted, and

a facsimile interface unit, operatively connected to said logic and signaling system, said facsimile interface unit generating a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel, said facsimile interface unit comprising a look ahead buffer to perform early line control packet detection by looking ahead a predetermined time interval into a received satellite data stream and identifying a valid idle line control packet.

6. The mobile communication system according to claim 5, wherein said facsimile interface unit performs the early line control packet detection, and when the idle line control packet is preceded by either a binary coded signal connection packet or a message connection packet, the idle line control packet is substantially immediately processed and removed from the received satellite data stream when a first instead of a last bit of the idle line control packet is received, avoiding unnecessary modulation of invalid data.

7. The mobile communication system according to claim 6, wherein when the idle line control packet is substantially immediately processed and removed from the received satellite data stream, the idle line control packet does not contribute an additional 60 ms of time to an existing binary coded signal connection analog line state.

8. The mobile communication system according to claim 5, wherein when said facsimile interface unit removes the idle line control packet substantially at once instead of removing the idle line control packet over 18 data cell times, the look-ahead buffer will shrink in size as the idle line control packets are detected and removed.

9. The mobile communication system according to claim 5, wherein when said facsimile interface unit switches from demodulating to modulating, the look-ahead buffer is filled with satellite data by said facsimile interface unit receiving idle fill data over the satellite while said facsimile interface unit is demodulating.

10. The mobile communication system according to claim 5, wherein when said facsimile interface unit demodulates the received satellite data stream, said facsimile interface unit determines whether there is about at least a 75±

20 ms gap between a preamble connection line state and a preceding line state.

11. The mobile communication system according to claim 5, wherein said facsimile interface unit preserves an octet integrity of the preamble connection line state by delaying the transmission of a modulated binary coded procedural signal by a period of up to 8 data cells.

12. The mobile communication system according to claim 5,

wherein a delay through an originating facsimile interface unit through a destination facsimile interface unit is less than 1 second in either direction of data flow, and

wherein total delay includes delays associated with modulation and demodulation, the facsimile interface unit and facsimile modem interface.

13. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system, an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter, the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data, the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data and a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating received signaling messages and generating codes for a signaling message to be transmitted, a method of providing a facsimile communication function permitting the mobile communication system to transmit and receive facsimile data to and from the mobile satellite system, said method comprising the steps of:

(a) generating a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel;

(b) performing an early line control packet detection by looking ahead a predetermined time interval into a received satellite data stream and identifying a valid idle line control packet; and

(c) when the idle line control packet is preceded by either a binary coded signal connection packet or a message connection packet, substantially immediately processing and removing the idle line control packet from the received satellite data stream when a first instead of a last bit of the idle line control packet is received, thereby avoiding unnecessary modulation of invalid data.

14. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising:

a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system;

an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, said antenna system including

an antenna including one of a directional and an omnidirectional configuration, a diplexer, a low noise amplifier, a beam steering unit when said antenna is of the directional configuration, and at least one of a compass and sensor to determine vehicle orientation,

a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter,

the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data,

the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data;

a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating a received signaling messages and generating codes for a signaling message to be transmitted, said logic and signaling system providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service,

wherein upon the loss of the primary service the mobile communication system waits for a first time interval before attempting to register in the alternate service and when the primary service is recovered prior to the expiration of the first time interval, the mobile communication system will not attempt to register with the alternate service,

wherein when the mobile communication system registers on the alternate service, the mobile communication system will wait a second time interval and continuously monitor the availability of the primary service, and when the primary service becomes satisfactorily available, the mobile communication system will attempt to return the registration to the primary service; and

a digital terminal equipment unit, operatively connected to said logic and signaling system, said digital terminal equipment unit initiating a call release for said mobile communication system by issuing a release command to said logic signaling system, and when the call release is initiated by a public switched telephone network, said logic and signaling system issues a no carrier indication to said digital terminal equipment, and continuously transmits an on hook status until at least one of receiving an onhook acknowledgment and expiration of a predetermined time interval.

15. In a mobile satellite system including a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system, the mobile communication system comprising:

a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system;

an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite, said antenna system including

an antenna including one of a directional and an omnidirectional configuration, a diplexer, a low noise amplifier, a beam steering unit when said antenna is of the directional configuration, and at least one of a compass and sensor to determine vehicle orientation,

a transceiver system, operatively connected to said antenna system, including a receiver and a transmitter,

the transmitter converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, the transmitter including an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data,

the receiver accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system, the receiver including a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data;

a logic and signaling system, operatively connected to said transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received, said logic and signaling system configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controlling protocols between the mobile communication system and the mobile satellite system, and validating a received signaling messages and generating codes for a signaling message to be transmitted, said logic and signaling system providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service,

wherein upon the loss of the primary service the mobile communication system waits for a first time interval before attempting to register in the alternate service and when the primary service is recovered prior to the expiration of the first time interval, the mobile communication system will not attempt to register with the alternate service,

wherein when the mobile communication system registers on the alternate service, the mobile communication system will wait a second time interval and continuously monitor the availability of the primary service, and when the primary service becomes satisfactorily available, the mobile communication system will attempt to return the registration to the primary service;

a digital terminal equipment unit, operatively connected to said logic and signaling system, said digital terminal equipment unit initiating a call release for said mobile communication system by issuing a release command to said logic signaling system, and when the call release is initiated by a public switched telephone network, said logic and signaling system issues a no carrier indication to said digital terminal equipment, and continuously transmits an on hook status until at least one of receiving an onhook acknowledgment and expiration of a predetermined time interval; and

a facsimile interface unit, operatively connected to said logic and signaling system, said facsimile interface unit generating a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel, said facsimile interface unit comprising a look ahead buffer to perform early line control packet detection by looking ahead a predetermined time interval into a received satellite data stream and identifying a valid idle line control packet.

16. In a mobile satellite system including a satellite communication switching office for receiving/transmitting a satellite message via a satellite using a mobile communication system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office via the satellite, a method of providing a facsimile communication function permitting the mobile communication system to transmit and receive facsimile data to and from the mobile satellite system, said method comprising the steps of:

(a) generating a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel;

(b) performing an early line control packet detection by looking ahead a predetermined time interval into a received satellite data stream and identifying a valid idle line control packet; and

(c) when the idle line control packet is preceded by either a binary coded signal connection packet or a message connection packet, substantially immediately processing and removing the idle line control packet from the received satellite data stream when a first instead of a last bit of the idle line control packet is received, thereby avoiding unnecessary modulation of invalid data.

17. In a mobile satellite system including a satellite communication switching office for receiving/transmitting a satellite message via a satellite from/to a mobile communication system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office via the satellite, the mobile communication system comprising:

a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system;

an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite,

a transceiver system, operatively connected to said antenna system, converting the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, transmitting the modulated signal to said antenna system, accepting the first satellite message from the antenna system and converting the first satellite message into at least one of voice, data, fax and signaling signals for transmitting to the user interface system;

a logic and signaling system, operatively connected to said transceiver, obtaining an outbound signaling channel used for updated system information and commands and messages, and configuring said transceiver for reception and transmission of at least one of voice, data, fax and signaling messages,

said logic and signaling system providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service,

wherein upon the loss of the primary service the mobile communication system waits for a first time interval before attempting to register in the alternate service and when the primary service is recovered prior to the expiration of the first time interval, the mobile communication system will not attempt to register with the alternate service;

a digital terminal equipment unit, operatively connected to said logic and signaling system, initiating a call release for said mobile communication system by issuing a release command to said logic signaling system, and when the call release is initiated by a public switched telephone network, said logic and signaling system issues a no carrier indication to said digital terminal equipment, and continuously transmits an on hook status until at least one of receiving an on-hook acknowledgment and expiration of a predetermined time interval; and

a facsimile interface unit, operatively connected to said logic and signaling system, said facsimile interface unit generating a line control packet responsive to a line state transition indicating transmission of information associated with a new line state over a communication channel.

18. In a mobile satellite system including a satellite communication switching office for receiving/transmitting a satellite message via a satellite from/to a mobile communication system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office via the satellite, a method of providing a roam function permitting the mobile communication system to roam between the mobile satellite system and a terrestrial based communication system responsive to the user selection of a primary service and an alternate service, said method comprising the steps of:

(a) determining whether the primary service has been lost a first time;

(b) waiting a first time interval before attempting to register in the alternate service when the primary service is lost the first time;

(c) when the primary service is recovered prior to the expiration of the first time interval, not attempting to register with the alternate service;

(d) when the mobile communication system registers on the alternate service, waiting a second time interval and continuously monitoring the availability of the primary service, and when the primary service becomes satisfactorily available, attempting to register on the primary service;

(e) when the mobile communication system has invoked any registration, starting a timer for a third time interval, and resetting the timer for each registration;

(f) when the third time interval expires, setting the registration delay to the first time interval;

(g) when both the primary and alternate services are lost, continuously monitoring the primary and alternate services, and attempting to register on whichever of the primary and alternate services that is satisfactorily available first.