WO1999003214A9

WO1999003214A9 - Mobile satellite system having an imrproved signaling channel

Info

Publication number: WO1999003214A9
Application number: PCT/US1998/014589
Authority: WO
Inventors: David Roos; Michael Parr; Anthony R Noerpel
Original assignee: Hughes Electronics Corp
Priority date: 1997-07-14
Filing date: 1998-07-13
Publication date: 1999-04-22
Also published as: US20010018348A1; EP0925657A1; EP0925656A1; EP0925655A1; AU8569798A; EP0925706A1; EP0925706B1; AU8405498A; WO1999004510A1; US6278876B1; AU8485798A; WO1999004510A9; WO1999003213A1; EP0925662A1; WO1999003228A9; US6282178B1; WO1999003296A1; EP0925657B1; AU8403898A; US6438386B2

Abstract

An access material for information communication including a transmitter for establishing a radio frequency link allowing the access terminal to initiate information communication via at least one of a multiplicity of communication channels of a time division multiple access (TDMA) satellite communication system. A data communication channel associated with one of the multiplicity of communication channels is provided for transmitting signaling information over the satellite communication system as a first communication channel. A second communication channel, a voice communication channel, is also associated with the communication channel, thus providing, respectively, first and second modes of communication for voice and signaling information transactions. A memory stores a protocol processing information including a signal protocol assigned to the access terminal via the satellite communication system for transmission by the transmitter using the data communication signaling channel for signaling over the radio frequencycommunication link. Robust signaling may be provided with enhanced information modulation such as binary phase shift keying or dual tone multifrequency digits for keying, enhanced noise and power margins for signaling, or a paging antenna provided with the access terminal of the like for a more robust signaling link.

Description

United States Patent Application

of

David Roos

Michael Parr and

Anthony Noerpel

MOBILE SATELLITE SYSTEM HAVING AN IMPROVED SIGNALING CHANNEL

This application claims priority to U.S. Provisional patent application Serial No. 60/052,443, of , et al.; filed July 14, 1997, for I incorporated herein by reference.

This patent document relates to a common air interface described in a series of patent documents filed concurrently herewith. Related patent documents are: U.S. Patent Application Serial No. 09/ , filed July 13,

1998, of Soleimani, et al . ; for SIGNALING MAINTENANCE FOR DISCONTINUOUS INFORMATION COMMUNICATIONS, now U.S. Patent No.

U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Joshi, et al . ; for SYSTEM AND METHOD FOR IMPLEMENTING TERMINAL TO TERMINAL CONNECTIONS VIA A GEOSYNCHRONOUS EARTH ORBIT SATELLITE, now U.S. Patent No.

U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Noerpel, et al . ; for SPOT BEAM SELECTION IN A MOBILE SATELLITE COMMUNICATION SYSTEM, now U.S. Patent No.

U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Noerpel, et al.; for PAGING RECEPTION ASSURANCE IN A MULTIPLY REGISTERED WIRELESS TRANSCEIVER, now U.S. Patent No. ;

U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Joshi, et al . ; for IMMEDIATE CHANNEL ASSIGNMENT IN A WIRELESS SYSTEM, now U.S. Patent No.

U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Joshi, et al . ; for ERROR AND FLOW CONTROL IN A SATELLITE COMMUNICATIONS SYSTEM, now U.S. Patent No.

; and U.S. Patent Application Serial No. 09/ , filed

July 13, 1998, of Roos, et al.; for SYNCHRONIZATION OF A MOBILE SATELLITE SYSTEM WITH SATELLITE SWITCHING, now U.S.

Patent No. , all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION The present invention relates to cellular and satellite communications. More particularly, the invention relates to a method and a system for providing a robust signaling channel for improving the communication of signal messaging and information transactions between a mobile access transmitter and a receiver m a mobile satellite communication system.

A mobile satellite communication system such as the Geosynchronous Earth Orbit Mobile (GEM) network discussed herein, typically includes one or more satellites, at least one fixed ground terminal such as a gateway system (GS) and several mobile access terminals (ATs). The access terminals typically communicate with the public switched telephone network (PSTN) or other mobile terminals via an air communication interface between the satellite and the gateway.

Using the mobile access terminals, the satellite system provides a variety of telephony services. Satellite telephony systems as described herein share call processing information with terrestrial systems such as the GSM cellular system to allow compatibility between the satellite, cellular, and the public switch telephone network services. The terrestrial standards such as GSM may not apply directly to the mobile satellite communication system, more particularly the satellite air interface poses physical constraints not accounted for in the GSM architecture.

A number of communication systems utilizing satellites and small mobile terminals provide voice and other information communication. In all such systems, the bandwidth and satellite power associated with the communication links may be expensive and limited resources. In addition, the mobile access terminals such as hand-held terminals (HHTs) , which are often small, hand-held devices, are constrained by power consumption and related battery life concerns . In maintaining an active voice communications channel, however, information must be transmitted on a regular basis for synchronization between the satellite and the access terminal, e.g., for timing, frequency, and power parameters. The following assumptions are made: The threshold for signaling is 2.5 dB . This will yield a packet error rate on the order of 10%. A retracted HHT antenna adds at least 15 dB of attenuation relative to a fully extended antenna pointed in the right direction. A user's body introduces approximately 6 dB of additional loss when the HHT is held close to him. A retracted HHT antenna in a HHT held close to a user's body introduces approximately 21 dB of loss. An additional HHT "paging antenna" may be hypothesized which offers more of an omnidirectional pattern with gain approximately 6 dB less than that of the extended antenna pointed in the right direction. The problem arises when an HHT is in a disadvantageous position with respect to the satellite. This disadvantaged position includes the attenuation due to the antenna being retracted as well as the attenuation due to shielding by the user's body and mispointing. Following are problem scenarios: Paging: When the HHT is not actively in use, it must receive the paging signal and engage in the call setup messaging that takes place prior to notifying the user of an incoming call. SMS delivery: The HHT must engage in the signalling necessary to accept SMS messages whenever it completes a registration or whenever it has just completed a call. Registration: When the HHT is not actively in use, it must be able to determine which beam it is in, and perform the beam selection and registration procedures. Attach/Detach: When the HHT is powered up or down, it must be able to attach or detach, respectively. Supplemental Service activation:

When an HHT is engaged in a call, but the user purposely moves it into a disadvantaged position to press buttons to activate supplemental services, the HHT must be able to successfully communicate with the gateway controlling that handset via the FACCHs . Voice mail: When an HHT is engaged in a voice call, but the user purposely moves it into a disadvantaged position to press buttons to send DTMF tones, the HHT must be able to successfully communicate those tones to the gateway. Call termination signaling: At the end of a call, when the user has moved the HHT into a disadvantaged position to press the "end" button, the HHT must engage in the call termination signaling.

From the assumptions above, a HHT with retracted antenna may not be able to perform any of the functions listed in the problem scenarios. Therefore, the HHT may become unusable with its antenna retracted: a user cannot make or receive calls or short messages, and an HHT cannot register in a new beam (or even determine that it needs to) . Even alerting will not be usable unless the HHT is turned on, the antenna extended long enough to register (or determine that it need not register) , and then the antenna retracted.

Thus, the user must extend the antenna to enable the HHT to operate at all. A typical scenario might be this: A user wakes up one day, turns on his HHT, pulls out the antenna, points it toward the satellite until it dictates that it has registered or, if it need not register, that it is ready to make or receive calls, and leaves the HHT in an orientation that allows it to see the satellite at all times, which seems unrealistic. The robust channel offers some relief to this condition.

Thus, there exists a need for a method and a system to ensure that a user terminal, when operating in a GEO system, can perform the signaling protocol required to set up and tear down calls and register when the user is not cooperating by advantageously positioning the user terminal.

SUMMARY OF THE INVENTION Accordingly, the present invention addresses a need for a Geosynchronous Earth Orbit (GEO) Mobile Satellite System wherein the channel may become impaired during the signaling phase of the call, for example call setup and tear down, relative to the conversation phase of the call because the user may no longer be expected to cooperate by advantageously orienting the phone or positioning the phone such that it has a clear view of the satellite. This is because the user does not have the continuous feedback of the voice quality of the party being conversed with. This invention is a method of overcoming the impaired link in a way that does not overly impact the capacity of the system, does not adversely effect call setup time, and yet is easy to implement in a user terminal .

The present signaling design, except as noted below, provides approximately 9.5 dB of margin over threshold (7 dB margin over voice threshold of 5 dB = 2.5 dB signaling threshold below the 5 dB voice threshold) . The present PCH margin is 6 dB higher than that above (15.5 dB margin total). The present alerting margin is 30 dB over threshold.

Briefly summarized, the present invention relates to an access terminal for information communication including a transmitter for establishing a radio frequency link allowing the access terminal to initiate information communication via at least one of a multiplicity of communication channels. In a described embodiment, a time division multiple access (TDMA) satellite communication system uses a data communication channel associated with one of the multiplicity of communication channels is provided for transmitting signaling information over the satellite communication system as a first communication channel. A second communication channel, a voice communication channel, is also associated with the communication channel, thus providing, respectively, first and second modes of communication for voice and signaling information transactions. A memory stores a protocol processing information including a signal protocol assigned to the access terminal via the satellite communication system for transmission by the transmitter using the data communication signaling channel for signaling over the radio frequency communication link. Robust signaling may be provided with enhanced information modulation such as binary phase shift keying or dual tone multifrequency digits for keying, enhanced noise and power margins for signaling, or a paging antenna provided with the access terminal or the like for a more robust signaling link.

It will be understood that both the foregoing and general description m the following detailed description are exemplary and intended to provide further explanation of the invention as claimed. The accompanying drawings provide an understanding of the invention as described in the preferred embodiments to illustrate the invention and serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of a mobile satellite communication system in accordance with the present invention; and FIG. 2 is a block diagram of a preferred embodiment of a mobile access terminal for use in the mobile satellite communication system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and particularly to

FIG. 1, a preferred embodiment of a mobile satellite communication system 10 is illustrated. The mobile communication system 10, herein a Geosynchronous Earth Orbit Mobile satellite system (GEM) includes several mobile access terminals 12 and one or more satellites 14. One or more gateway stations 16 (GS) are coupled to public switch telephone networks 18 (PSTN) . The access terminal 12 is typically a hand-held telephone or vehicle-mounted telephone, but, as described in the present embodiment, the access terminal 12 may provide operation both as a GEM access terminal and as an GSM cellular telephone. While being used with the satellite communication systems described herein, the access terminal 12 communicates over an L-band frequency with a particular spot beam 20 with the satellite 14. Each spot beam 20 is associated with a predetermined geographic region. The terrestrial gateway 16 communicates with the satellite 14 over a Ku-band frequency. As illustrated, a plurality of gateways 16 may be employed, each providing similar functions and being employed to access, for example, respective public switched networks 18.

The satellite 14 includes transponders for translating between the L-band spot beam 20 signals used by the access terminals 12 and the Ku-band 22 signals used by the gateway 16. The gateway 16 interfaces with the terrestrial telephony carrier, such as PSTN 24, and may also interface with a conventional cellular network such as GSM. Accordingly, users may place telephone calls using the access terminal 12 to either land line or cellular telephone users .

The satellite 14 provides L-band-to-L-band bent pipe single hop communications, as well as satellite switched communications to support communications between the users of the access terminals 12. At satellite 14, the L-band 20 uplink and downlink are transmitted via multiple L-band spot beams 20. Subscribers to the system 10 have unique telephone numbers allowing them to receive telephone calls when they are registered to receive pages from either the GEM or the GSM cellular network. Registration is automatic when the access terminal 12 is turned on, such that a registration procedure locates the access terminal 12 within a particular spot beam coverage area. In addition to originating calls, the access terminals 12 can receive calls from any terrestrial facility by connecting the call through the gateway station 16, at which the gateway 16 determines the location of the access terminal 12 and sends a paging message to the access terminal 12 to announce the incoming call. The system 10 uses a low rate encoded or ciphered voice transmission. In the described embodiments, the access terminals 12 are provided with dual mode operation allowing for voice communications either via satellite or via the local cellular system, e.g., GEM and GSM as discussed herein.

The gateway 16 provides for user mobility as users travel with the access terminal 12 from spot beam to spot beam. Additionally, the communication channels carried via the satellite 14 provides space segment resources used for control functions, i.e., one or more channels in each L-band spot beam 20 are control channels, e.g., the gateway 16 may place a forward control signal in each L-band spot beam 20 to allow synchronization of the access terminals 12 and to carry network control information from the gateway 16 to the access terminals 12. The forward control channels allow the access terminals 12 to acquire a satellite carrier and identify the L-band spot beam 20 and gateway station 16 which originates the signal. The gateway 16 uses the forward control channel to page access terminals 12 using unique addresses to announce mobile terminated calls. Each L-band spot beam 20 preferably contains a return direction signaling channel that access terminals 12 use to initiate and register calls with the gateway 16. During a call, in-band low data rate control channels are preferably available between the access terminals 12 and the gateway 16 for call supervision, power control, and to initiate call termination. For example, during burst communication between the access terminal 12 and the satellite 14, a threshold signal may be established relating to the strength of the transmitted burst for setting a power control bit based on a comparison of received signal strength with threshold values . In addition to such information being transmitted during active voice communications, certain information must also be transmitted during voice inactivity by keep-alive bursts (KABs) which can be categorized as one of two types, namely, explicit digital information, and implicit information in the waveforms transmitted.

Explicit digital information provided by the keep- alive bursts include a description of the background sounds present that the transmitter's microphone, and commands and status messages associated with power control. Information implicit in the waveforms transmitted include the power level of the signal, the signal quality as perceived by the receiver, and information used in tracking both carrier frequency offset and symbol timing error for synchronization between the transmitter and receiver.

The system 10 contains considerable operational flexibility both from the standpoint of network features and mobile terminal capabilities. The gateway 16 is a conventional gateway as understood in the art, which includes a mobile switching center (MSC) , base station controllers

(BSCs) , base transceiver stations (BTS) , and radio frequency units. As is understood by those skilled in the art, the MSC allows communications with the public switch telephone network or other mobile switching centers. The MSC is connected preferably with an A-interface such as a standard El or E3 line with the BSC. The BSC is then connected through a communications channel such as a Tl line to one or more BTSs which may communicate via radio frequency (RF) communications to the access terminal 12. Telephony communications may be originated with the access terminal 12 by transmitting initialization data to the satellite 14 of the space segment over a control channel which then communicates down to the gateway 16. The control channel is transmitted over a time slot within a frequency assigned to the spot beam 20 having a coverage area surrounding the access terminal 12. At the gateway 16, the call is transmitted via a radio frequency channel to the BTS assigned to the spot beam 20 servicing the access terminal 12. From the BTS the call is routed to the BSC and then to the MSC, from which the call is routed to either the PSTN or another MSC. Thereafter, a communications channel is established through the entire gateway 16 and a subscriber using the access terminal 12 may communicate over the established communications channel. Calls may also originate from either the PSTN or a GSM cellular network by entering the gateway 16 at the MSC which routes information to the BSC for paging the access terminal 12 via the appropriate BTS. After the access terminal 12 responds to the page from the BTS, a communications channel is then established.

The access terminal 12 as shown in FIG. 2 includes a satellite module 40, a satellite antenna 42, a cellular module 44, and a user interface module 46. The satellite module 40 is coupled to the user interface module 46, the cellular module 44, and the satellite antenna 42. Preferably, the satellite antenna 42 is a physically small antenna, such as a helix type antenna. The satellite module 40 includes a modem and TDMA unit 48, an RF coder and decoder (codec) 50, a burst transmitter 52, a receiver 54, and a transmit or receive (T/R) switch 56. In the preferred embodiment, the modem 48 is connected to the RF codec 50, and the RF codec 50 is connected to the burst transmitter 52 and to the receiver 54. The T/R switch 56 is connected to the burst transmitter 52, the receiver 54, and the satellite antenna 42.

Within the satellite module 40, the modem 48 converts speech or data samples to and from channel symbols using quadrature phase shift key modulation (QPSK) . QPSK is preferably performed digitally by an application-specific integrated circuit or alternatively on a commercial available digital signal processor. The RF codec 50 converts channel symbols from the modem 48 into baseband I and Q signals that are transmitted to the burst transmitter 52. In the receive direction, the RF codec 50 processes an IF signal 53 from the receiver 54 for input to the modem 48.

The burst transmitter 52 converts the I and Q signals from the RF codec 50 up to a desired frequency, preferably an L-band frequency, for transmission by the first antenna 42. Additionally, a paging antenna 43 may be provided to overcome any retracted antenna signal loss and relieve orientation problems that may be associated with use of the access terminal 12, which facilitates a more robust signaling channel. The receiver 54 converts a received L-band signal from the first antenna 42 into the IF signal 53 sent to the RF codec 50.

The T/R switch 56 allows the access terminal 12 to either transmit data or receive data. The access terminal 12 also includes a synthesizer 58 that provides a fixed local oscillator (LO) signal for the RF codec 50. The synthesizer 58 includes a variable local oscillator for channel tuning within the satellite module 40 and generates data clock signals for the modem 48. Both the fixed local oscillator and the variable local oscillator within the synthesizer 58 may be adjusted based on commands from either the gateway 16 or from another access terminal 12. In the preferred embodiment, the synthesizer 58 is connected to the receiver 54 and to the cellular module 44. The user interface module 46 includes an audio and codec unit 59, a voice processing unit 60, a controller 62, an input/output (I/O) interface 64, and a memory 66. Preferably, each element within the user interface module 46 communicates with the other user interface elements. The voice processing unit 60 includes a voice transcoder that performs source coding to compress the digital 64 Kb/s PCM signal. Specifically, an encoder running on a programmable digital signal processor, such as a low delay CELP encoder, compresses the 64 Kb/s PCM signal into approximately a 3.6 Kb/s encoded signal. Alternatively, the encoder may be a multibased excited (MBE) type 3.6 Kb/s encoder that is well known to those skilled in the art .

The controller 62 preferably provides a multitasking firmware environment for monitoring and controlling the mobile terminal hardware. The controller 62 may occupy the same processor as the voice transcoder or may optionally be disposed on a separate processor. Preferably, the controller 62 includes an I/O interface 64 that provides a communication interface with a user. The I/O interface 64 includes a keypad for data entry such as a phone number, a display, a data port for digital communication such as a facsimile transmission, and a smart card interface as specified for GSM.

The cellular module 44 allows the access terminal 12 to communicate with a cellular system over a second antenna 61. The second antenna is a linearly polarized whip meeting cellular system standards and the cellular module 44 uses standard components, such as a GSM chip set, known to those skilled m the art. Preferably, the access terminal 12 operates m a first mode where the access terminal 12 functions as a conventional cellular phone. In a second mode, the access terminal 12 preferably operates so that the access terminal 12 communicates with the satellite 14. A battery 68 is provided for portable operation of the access terminal 12. The preferred access terminal 12 has many advantages. For example, the access terminal 12 provides dual-mode operation, either cellular or satellite. Also, the access terminal 12 is mobile and provides high quality digital voice. Further, the access terminal 12 allows for paging and messaging, transmission at a 2400 or 4800 bps data rate via the data port, and provides a convenient cellular-like interface. Also, the access terminal 12 may transmit on a single channel using a single time slot within a carrier signal allowing many other access terminals 12 to transmit over the same carrier. Thus, the access terminal 12 efficiently transmits over L-band spot beam 20 frequency resources .

Following are areas which may provide improvements (in the following discussion, binary phase shift keying "BPSK" means "BPSK with each symbol offset by pi/4 radians from the last") :

1. Make the FACCH in each direction BPSK, thereby gaining 3 dB of margin. Note that we still have to send the comfort noise and power control bits. See the FACCH bit accounting below. 2. Raise the power of access grant channel (AGCHs) that are in response to BPSK random access channel (RACHs) (see below) ; leave the others at the nominal power. 3. Each other forward signaling channel can be set to levels corresponding to 12.5 dB at some increase in overhead consumption. Note that paging channel (PCH) will be reduced from its current value. 4. Make the standalone dedicated control channel

(SDCCH) in both directions BPSK, thereby gaining 3 dB of margin but at a small increase in call setup time. In addition, the SDCCH must send power control bits. 5. Make the RACH burst BPSK ONLY for RACHs not associated with HHT-originated calls. The idea is that RACHs are relatively short for all but HHT-originated calls, and HHT-originated calls will have human assistance for optimizing the orientation.

6. Create a new unique word to differentiate between the two types of RACH. The gateway will have to demodulate the RACHs in accordance with the unique words . 7. Send DTMF digits that originate in the handset keypad as FACCH messages rather than as in-band DTMF digits (ought to do this anyway on general principles) . 8. Add a "paging antenna" 43 to the hand-held terminal to overcome the retracted antenna loss and relieve somewhat the orientation problems. FACCH bit accounting: data link layer (DLL) divides radio resource (RR) packets into 7-byte packets and sends each 7-byte packet as two successive bursts with the following bit accounting:

7X8 = 56 bits of RR data +20 bits of DLL header +20 bits of CRC and FEC tail (16+4)

= 96 bits X2 rate FEC = 192 bits per 2 bursts div. 2 (two bursts) +2 spare

+4 comfort noise +4 power control +6 UW

= 112 bits per BPSK burst Overhead in the forward direction: This is worst for an all-handset network; IFSs, fixed terminals, and vehicular terminals will lessen the overhead slightly. Analysis shows that with these changes in place the aggregate overhead power is as shown in the table below. These figures assume that the nominal voice carrier power is equal to

43.11 dBW, voice activity is 40%, and total AEIRP is 70.2 dBW.

Usefulness of the proposed approach: Three levels of complexity are considered. Level I assumes all of the features listed above have been implemented except for the paging antenna. Level II assumes the paging antenna in addition. Depending on how the paging antenna is implemented, it may afford additional tolerance to mispointing for SMS and supplementary service activation.

Problem Area Effectiveness

Paging Level I: Net margin of 1 3 dB, accommodates users whose antennas are extracted but misoriented up to about + /-85 degrees with otherwise clear line- of-sight of the satellite. Level II: As for Level I, but allows for antenna retracted and up to about 7 additional dB of misorientation/obstruction (about what a user's body would introduce).

SMS delivery Level I: As for paging above. User must extract the antenna before SMS messages can be received. At the end of each call, the user must keep his antenna extracted and approximately ( + /-85 degrees, assuming line of sight) pointed toward the satellite until the SMS has been delivered. Delivery time is a few seconds per SMS message. Level II: No additional improvement, unless the paging antenna has better gain beyond + /-85 degrees.

Registration As for paging above.

It should be appreciated that a wide range of changes and modifications may be made to the preferred embodiments as described herein. Thus, it is intended that the foregoing detailed description be regarded as illustrative rather than limiting and that the following claims, including all equivalents, are intended to define the scope of the invention.

Claims

What is claimed is:

1. An access terminal for information communications, comprising: a transmitter for establishing a radio frequency communication link allowing the access terminal to initiate information communication via at least one of a multiplicity of communication channels of a satellite communication system; a voice communication channel associated with said at least one of said multiplicity of communication channels of the communication system; and a data communication channel associated with said at least one of said multiplicity of communication channels of the communication system for signaling information transactions in communication with the satellite communication system.

2. An access terminal as recited in claim 1 comprising a memory for storing protocol processing information comprising a signaling protocol assigned to the access terminal via the satellite communication system for transmission by said transmitter used by said data communication channel for signaling over the radio frequency communication link.

3. An access terminal as recited in claim 1 comprising a first antenna and a second antenna coupled to said transmitter.

4. An access terminal as recited in claim 3 wherein said voice communication channel uses said first antenna and said data communication channel uses said second antenna.

5. A system for mobile satellite communications, comprising: a radio frequency communication link for conveying multiple communication channels using time division multiple access (TDMA) ; an access terminal for information communication via at least one of said multiple communication channels, said access terminal comprising: a memory for storing protocol processing information; and a transmitter for establishing the radio frequency communication link to said receiver; said memory storing a signaling protocol assigned to said access terminal by said receiver for transmission by said transmitter.

6. A system as recited in claim 5 wherein said access terminal comprises: a voice communication channel associated with said at least one of said multiplicity of communication channels of the communication system; and a data communication channel associated with said at least one of said multiplicity of communication channels of the communication system for signaling information transactions in communication with the satellite communication system.

7. A system as recited in claim 5, comprising a paging channel for information communication with said access terminal .

8. A system as recited in claim 7 wherein said paging channel comprises a data communication channel between said access terminal and the satellite.

9. A method of maintaining information communication from an access terminal over a radio frequency communication link for conveying multiple communication channels, comprising the steps of: initiating information communication from the access terminal to a satellite communication system via at least one of the multiple communication channels; providing a first mode of communications for voice communications subsequent to said initiating step; providing a second mode of communications for signaling information transactions; assigning protocol processing information in the form of a signaling protocol for transmission by the access terminal for use in the second mode of communications; and transmitting messages from the access terminal to communicate information transactions to the satellite communication system to signal access terminal status.

10. A method as recited in claim 9 wherein said second mode of communications comprises binary phase shift keying (BPSK) to gain a three dB of margin for signaling.

11. A method as recited in claim 10 wherein said second mode of communications comprises the step of raising the power of the access grant channel (AGCHs) that respond to the random access channel (RACH) .

12. A method as recited in claim 9 wherein said second mode of communications comprises the step of providing a forward signaling channel with increased power for signaling, paging, and the like.

13. A method as recited in claim 11 wherein said random access channel (RACH) comprises the step of signaling associated with hand-held terminal (HHT) originated calls and non-HHT originated calls to provide distinct random access channels to differentiate between the type of access terminal originating the information communication.

14. A method as recited in claim 9 wherein said second mode of communications comprises the step of sending a dual tone multifrequency (DTMF) digits which originate in the hand-held terminal (HHT) as fast associated control channels (FACCHs) .

15. A method as recited in claim 9 comprising the step of providing a paging antenna to the hand-held terminal

(HHT) to overcome the retracted antenna loss and orientation problems .