JPH07154856A - Mobile terminal and mobile object satellite communication system using the same - Google Patents

Abstract

PURPOSE:To improve a working rate at the time of moving through frequent shadowing area by the mobile terminal of a mobile object satellite communication system. CONSTITUTION:This mobile terminal calculates a present position from the signals of a GPS satellite in a position calculation circuit 132, predicts the position of a moving destination hereafter by a speed/acceleration sensor 138 and a bearing sensor 139, refers to the perspective map information of a communication satellite of a data base 133 and predicts a time band when communication with the communication satellite by an antenna 120 becomes possible. The communicable time band can be also obtained from the electric field intensity of signals from the communication satellite received by the antenna 110 for lookahead provided in a part more in front than the antenna 120. Message information and voice information are inputted and turned to digital data by an input/output part 180 and a voice encoder 172, are tentatively stored in a transmission buffer memory 140 and are read and transmitted to the communication satellite when the predicted communicable time band is reached. At the time, when the data are divided into the plural packets of a prescribed unit communication time length, the working rate is further raised.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile terminal device and a mobile satellite communication system using the same, and more particularly to a mobile terminal communication device mounted on a vehicle or the like mainly moving in an urban area and seeing from obstacles such as buildings accompanying the movement A mobile terminal device that performs digital two-way wireless communication such as message information and voice information with the other party through a stationary communication satellite whose quality (communication availability / non-availability) fluctuates, and a mobile satellite using this With communication systems.

[0002]

2. Description of the Related Art Inmarsat, which has the longest history and many achievements in the mobile satellite communication system, has started the service of Inmarsat-M system which can be used on land in addition to the conventional maritime service. In this system voice is digitized at a rate of 4.8 kbps.

On the other hand, there is a land mobile satellite communication system which provides a message service for encoding and transmitting a fixed text, which has been used in Japan mainly in the United States in recent years. This system uses a Ku band (14/12 GHz) fixed communication satellite, and its communication speed is, for example, 55 b.
It is as slow as ps and does not handle facsimiles or voice.

[0004]

Since Inmarsat capable of voice communication is an international communication service, its system is a worldwide network and the system usage fee is very expensive. Also, it is mainly for ships, and land services are simply portable. That is,
The mobile terminal device (mobile station) can be fixed and used at the destination where it is carried, and cannot be used from a traveling vehicle. K that can communicate messages from the moving vehicle
Although systems using u-band fixed communication satellites have also been realized, these conventional techniques have a common drawback that some areas cannot be used due to shadowing (a line of sight of communication satellites is not possible) in a city lined with skyscrapers. is there.

Therefore, an object of the present invention is to provide a mobile terminal device capable of improving the operating rate of a mobile satellite communication system in an area where shadowing frequently occurs on a communication satellite such as a dense area of buildings in a city. It is to provide a mobile satellite communication system that can provide both message communication and voice communication economically over a wide area nationwide using this mobile terminal device.

[0006]

A mobile terminal device according to the present invention is mounted on a land-based mobile unit and communicates with the other party through a stationary communication satellite whose visibility changes depending on a fixed obstacle as the mobile unit moves. A mobile terminal device that performs digital two-way wireless communication with the communication satellite; wireless transmission / reception means for transmitting / receiving digital data to / from the communication satellite by a radio signal; Input / output means for performing conversion; line-of-sight map database preset with line-of-sight map information indicating positions that can and cannot communicate with the communication satellite within the range of movement of the mobile unit; Position detecting means for detecting the current position of the moving body based on the signal of; Means for estimating a communicable time period indicating a start time and a duration for enabling communication with the communication satellite according to the movement by referring to the sight map database based on the detection outputs of the position detecting means and the movement detecting means. Communication possibility predicting means; transmission information accumulating means for temporarily accumulating information to be transmitted to the other party, which is input from the input / output means and converted into digital data; and the communication possible time predicted by the communication possibility predicting means. And transmission control means for sequentially reading out the digital data stored in the transmission information storage means in the band and transmitting the digital data to the communication satellite via the wireless transmission / reception means.

Another mobile terminal device according to the present invention is mounted on a land-based mobile unit and digitally bidirectionally communicates with a partner via a stationary communication satellite whose visibility changes depending on a fixed obstacle as the mobile unit moves. In a mobile terminal device that performs wireless communication; a first antenna that is provided at a front portion of the moving body in the moving direction and receives a radio signal from the communication satellite; and a communication satellite that is provided at a rear portion of the moving body in the moving direction. A second antenna for transmitting and receiving a radio signal to and from the first antenna
Wireless transmission / reception means for transmitting / receiving digital data to / from the communication satellite by electric wave signals, the electric field strength detecting means detecting electric field strength of the electric wave signal from the communication satellite received by the antenna; Input / output means having an interface for performing mutual conversion between the digital data and input / output information; movement detecting means for detecting the moving direction and speed of the moving body; detection of the electric field strength detecting means and the movement detecting means A communicability predicting means for predicting a communicable time zone indicating a start time and a duration time at which the second antenna can communicate with the communication satellite based on the output; and a digital data input from the input / output means. Transmission information storage means for temporarily storing the information to be transmitted to the destination, the communication predicted by the communication possible prediction means, And a transmission control means for transmitting to the communication satellite through sequentially reading said radio transceiver means of digital data stored in the transmission information storage means in time zone.

In each of the above mobile terminal devices,
The transmission control unit sets a unit communication time at which a predetermined communication possible probability is obtained within a predetermined allowable waiting time calculated by statistically processing the communication available time zone for the communication satellite that varies with the movement of the mobile body. It is possible to set in advance and divide the transmission digital data to the communication satellite into packet units that can be transmitted in the unit communication time to perform transmission and retransmission control.

Alternatively, in each of the mobile terminal devices, the input / output unit follows a predetermined coding rule for the voice input unit for inputting voice and converting it into an analog signal, and the analog signal from the voice input unit according to a predetermined coding rule. Encoding means for converting into a digital signal, decoding means for inversely converting the digital signal into an analog signal according to the predetermined encoding rule, and audio output means for converting the analog signal from the decoding means into voice and outputting it. And a key input means for inputting character, numeral and symbol data and a display means for visually displaying character, numeral and symbol data, enabling communication of voice information and message information in which fixed phrases are coded. It can be configured. Further, the encoding means uses, as the predetermined encoding law, a first encoding law having the same bit rate as the bit rate on the wireless line with the communication satellite and a speech quality inferior to that, but a low bit rate. A second coding rule; the transmission control means is configured to perform the first communication within the communicable time zone predicted by the communicability prediction means.
It is determined whether the voice information converted into digital data can be transmitted according to the encoding rule of No. 1, and if the audio information can be transmitted, the first encoding rule is designated to the encoding unit. No. 2 coding rule is designated, and the coding rule selection information indicating which coding rule is selected is selected together with the digital data of the audio information converted by the coding means and stored in the transmission information storage means. Regardless of the encoding rule, it is possible to always transmit to the communication satellite at the same bit rate as the bit rate of the first encoding rule. Furthermore, the wireless transmission / reception means has means for converting a bit rate of digital data received; the decoding means has the first coding rule and the second coding rule as the predetermined coding rule. The transmission control means includes the second rule as an encoding rule of the encoding means.
When the coding rule of No. 1 is selected, the other party converts the data into digital data according to the second coding rule.
When a radio wave signal modulated at the same bit rate as the bit rate of the encoding rule is received from the communication satellite, the bit rate of the digital data demodulated by the wireless transmission / reception means becomes the bit rate of the second encoding rule. The digital data may be converted and the decoding means may convert the digital data into analog data according to the second encoding rule.

Alternatively, in each of the mobile terminal devices, the wireless transmission / reception means has an electric field strength detection means for detecting the electric field strength of a radio signal from the communication satellite; the transmission control means has the electric field strength detection means. When it is detected that the SN ratio of the signal from the communication satellite is lower than a predetermined reference value based on the output of the means, the read bit rate of the digital data from the transmission information storage means is reduced to the read bit rate. The information can be transmitted to the communication satellite together with the information indicating that In addition, the band of the received wireless carrier signal is narrowed and SN
A narrow band filter for improving the ratio, and means for converting the bit rate of the received digital data; when the read bit rate is reduced by the transmission control means, the bit rate When a radio signal modulated by the lowered digital data is received from the communication satellite, the bit rate can be restored by demodulating the digital data through the narrow band filter.

A mobile satellite communication system according to the present invention includes: a communication satellite that is stationary in a geostationary orbit; a movement of the above-described structure that moves in an area in which the visibility of the communication satellite fluctuates due to a fixed obstacle accompanying the movement. A terminal station; and a fixed station that always looks at the communication satellite and performs two-way wireless communication of information converted into digital data with the mobile terminal apparatus through the communication satellite; Is stored in the fixed station via the communication satellite by predicting a communicable time zone according to a change in the line-of-sight of the communication satellite due to movement, and accumulating information in the predicted communicable time zone. To send to.

In the above mobile satellite communication system, each of the mobile terminal device and the fixed station statistically calculates the communicable time zone for the communication satellite that fluctuates as the mobile terminal device moves. The unit communication time that gives a predetermined probability of communication within the predetermined allowable waiting time is preset, and the digital data transmitted to the destination via the communication satellite is divided into packet units that can be transmitted in the unit communication time. Then, the transmission control and the retransmission control at the time of non-delivery of the transmission can be performed.

Alternatively, in the above mobile satellite communication system, each of the mobile terminal device and the fixed station has a first coding rule of a bit rate equal to a bit rate on a wireless link with the communication satellite, and Mutual conversion of encoding and decoding between the analog signal of the voice information and the digital data is performed in accordance with the selected one of the second coding rules having a lower speech rate but a lower bit rate. And a means for converting the bit rate of the digital data; the mobile terminal device is capable of transmitting the voice information converted into digital data according to the first coding rule within the communicable time zone. And the determination result is notified to the fixed station, and when transmission is impossible, each of the mobile terminal device and the fixed station follows the second coding rule. A configuration in which the encoded digital data is converted into a bit rate according to the first coding rule, the communication time is shortened and transmitted, and the receiving side restores the bit rate according to the second coding rule and is decoded. can do.

Alternatively, in the mobile satellite communication system, each of the mobile terminal device and the fixed station narrows a band of a radio carrier signal on a radio line with the communication satellite to improve a SN ratio. And means for converting the bit rate of digital data; the mobile terminal device determines whether the electric field strength of the radio signal from the communication satellite is below a predetermined level and notifies the fixed station of the determination result. When the mobile terminal device and the fixed station reduce the bit rate of the digital data on the wireless line when the level is lower than a predetermined level and then transmit the digital data, and the receiving side improves the SN ratio through the narrow band filter. It can be configured to restore the bit rate.

In the mobile satellite communication system having each of the above-mentioned configurations; the fixed station is connected to a plurality of user terminal stations which are provided for each user and which input and output information, and the plurality of user terminal stations through a public network. And a base station that transmits and receives information converted into digital data by radio signals to and from the communication satellite; the user terminal station connected to the communication satellite and the public network and passing through the base station. The mobile terminal device, which is a communication partner of the user terminal station, and a network management station that manages and controls a communication line between the communication satellites.

[0016]

The present invention will be described below with reference to the drawings.

FIG. 1 is a system configuration diagram of an embodiment of the present invention, showing an example applied to an information communication system for transportation business in which a plurality of users respectively manage the operation of vehicles such as trucks for freight transportation. In FIG. 1, a mobile satellite communication system according to the present embodiment is a stationary communication satellite 20 that covers the entire service area of a wide area and relays communication information such as messages and voices digitalized by radio signals.
And users A, B, C, who travel long and medium distances, including urban areas and mountainous areas, where the line-of-sight obstacle to the communication satellite 20 occurs.
Mobile stations 11, 12, 13, 14 each equipped with a mobile terminal device in a vehicle owned by D, and base stations 30, 31, 32, 33, 3 in which the line of sight to the communication satellite 20 is always secured.
4 and a network management station 40 that manages and controls the communication line (channel) of the entire system via the adjacent base station 30.
An operation management center 51, 52, 53, 54 that functions as a user terminal station and each of the users A, B, C, D manages operations such as destinations and freight collection / delivery instructions of its own vehicle, and base stations and network management. A station and a public network 60 for connecting the operation management centers and transferring communication information are provided. As the public network 60, either a telephone network transmitting analog signals or a data network transmitting digital signals can be used. User D is the base station 3
4 and is directly connected to the operation management center 54 without going through the public network 60. In the normal case, the operation management centers 51 to 53 are connected to the base stations 30 to 53, respectively.
33 is designated in advance. Here, in principle, the base stations are selected so that the communication cost in the public network 60 is the lowest, and the base stations 31, 32, 33 are designated for the operation management centers 51, 52, 53, respectively. Be present. It is possible to connect an operation management center (not shown) of another user to these base stations 30 to 33 through the public network 60 and share each other. Also,
Each user may have more than one mobile station.

FIG. 2 is a block diagram showing an embodiment of the mobile terminal device of the present invention. The mobile station 11 of the embodiment of FIG.
Used for ~ 14. In FIG. 2, a mobile terminal device 100 of the present embodiment is provided with a first antenna 110 which is attached to a front portion in a traveling direction of a vehicle and which tracks a communication satellite 20 and receives a radio signal of a Ku band (14/12 GHz), and an antenna 1.
A first receiving unit 111 that receives a signal in the Ku band from the communication satellite 20 through 10 and a first electric field intensity detection circuit 11 that detects the electric field intensity of the signal received by the receiving unit 111.
2 and a communication satellite 20 attached to the rear of the vehicle in the traveling direction.
A second antenna 120 for tracking and transmitting and receiving Ku band radio signals, and a second receiving unit 121 for receiving Ku band signals from the communication satellite 20 through the antenna 120.
A second electric field intensity detection circuit 122 for detecting the electric field intensity of the signal received by the receiving unit 121; a receiving buffer memory 123 for temporarily accumulating the baseband signal (digital data) received by the receiving unit 121; G not shown
Antenna 1 for radio signal for position measurement from PS satellite
GPS receiver 131 received through 30, a position calculation circuit 132 that calculates the current position of the vehicle based on the reception signal of the GPS receiver 131, a map regarding the road on which the vehicle is traveling and the surrounding environment such as buildings and hills. Data and the electric field strength detection circuit 112 (or 122) corresponding to this data (position and height) received electric field strength data of radio waves from the communication satellite 20 (line-of-sight information) are stored together. Database 133,
A speed / acceleration sensor 138 using a gyroscope or the like for detecting the traveling speed and speed change of the vehicle, an orientation sensor 139 using a magnetic compass or the like for detecting the traveling direction of the vehicle, and a transmission signal (digital data) is temporarily stored. A transmission buffer memory 140 for transmitting the baseband signal from the transmission buffer memory 140 to a Ku band signal and transmitting it from the antenna 120;
Also, a frequency synthesizer 150 for determining the reception / transmission frequency in the second receiving units 111 and 121 and the transmitting unit 141, and a duplexer 151 for sharing the antenna 120 between the receiving unit 121 and the transmitting unit 141.
And a control section 160 having a program-controlled microcomputer for controlling the entire apparatus to process various data and signals, and a tone signal generating circuit 1 for generating a tone signal.
61, a voice decoder 170 for performing digital / analog conversion of a voice signal, a tone synthesizing circuit 171 for synthesizing signals from the tone signal generating circuit 161 and the voice decoder 170, and a voice encoder 172 for performing analog / digital conversion of the voice signal. And a speaker 181, a microphone 182, a display device 183 and a keyboard 184, and a man-machine interface with a user (vehicle driver or the like) for inputting and outputting voice information and message information, and a facsimile signal. And a facsimile terminal 190 for transmitting and receiving. The facsimile terminal 190 may not be provided for the convenience of the user.

FIG. 3 shows the base station, network management station, and
It is a figure which shows each detailed structure of an operation management center, and connection between each other.

The base stations 30 to 34 have the same configuration with respect to the Ku band radio transmission / reception equipment, and the satellite line transmission / reception device 320 for transmitting / receiving signals to / from the communication satellite 20 through the antenna 310 and the buffer memory 340.
Operation management center and communication satellite 20 (mobile station)
Signal processing device 3 for storing and converting transmission / reception signals between
30, but a public network interface device 350 that interfaces with the public network 60 and controls transmission / reception to / from the operation management center is installed in the same place as the network management station 40 and the operation management center. Need not be provided (base stations 30, 34).

The network management station 40 interfaces with the public network 60 and controls the transmission and reception with the operation management center, the public network interface device 410, the satellite line transmission / reception device 320 of the attached base station 30, and signals. Processor 33
0 is accurately connected to the mobile stations 11 to 14 and the base stations 30 to 34, and the mobile stations 11 to 14 and the base stations 30 to 34 are instructed to know the channel use states of all the mobile stations 11 to 14 on the wireless communication line of the communication satellite 20. 14 to 14 and the operation management centers 51 to 54, a satellite line controller 420 is provided for controlling call connection, call connection, and call termination, and recording call billing information in the billing recorder 430. There is.

The operation management centers 51 to 54 have basically the same device configuration as user terminal stations, but the type of terminal can be changed according to the needs of the user.
In FIG. 3, the configuration of the user terminal station device 500 in the operation management center 51 of the user A is shown. The user terminal device 500 has a public network interface device 51 that interfaces with the public network 60 and controls outgoing / incoming calls.
0, a data communication terminal 530 such as a personal computer, a telephone terminal 540, a facsimile terminal 550, an encoder / decoder for performing analog / digital mutual conversion of voice signals, and these terminals (530 to 530) through a public network interface device 510. 550) and the network control station 40 and the communication control unit 520 which controls communication between the base stations 30 to 33. The operation management center 54 of user D
Need not be provided with the public network interface device 510, and the communication control unit 520 and the signal processing device 330 of the company's own base station 34 are directly connected.

Next, the operation will be described with reference to FIGS. The configuration and control method of the wireless line between the mobile station, the communication satellite, and the base station can be realized by an appropriate well-known technique, so detailed description is omitted. Each user A to D manages their own operation. The centers 51 to 54 manage the collection and delivery of cargoes of own vehicles (mobile stations 11 to 14) that move in or between cities, and use the user terminal device 500 to mount mobile terminals on the vehicles. It communicates with 100 to give a work instruction to a driver or a worker, and conversely receives a work report. Since the information to be communicated is often a fixed sentence, it is mainly composed of coded messages, but if more detailed information is to be communicated or if it becomes necessary to make an urgent voice contact, the communication is also made by voice.

Each of the mobile stations 11 to 14 is previously shadowed on the map / shadowing / database 133 at which point (the line-of-sight of the communication satellite 20 is poor due to the shadow of the building =
The view map information of whether or not (communication failure) occurs is stored. As this line-of-sight map information, data created by another vehicle or self-learning data by the own vehicle is used. Self-learning data is obtained as follows. As the vehicle travels, the mobile terminal device 100 calculates its own current position by the position calculation circuit 132 based on the signals from the GPS satellites received by the GPS receiver 131 (position measurement technology using GPS satellites is well known. (Detailed description is omitted), while the control unit 160 sequentially complements this current position information based on the outputs of the velocity / acceleration sensor 138 and the azimuth sensor 139, and at the same time, from the communication satellite 20 received by the receiving unit 111 through the first antenna 110. The electric field strength of the radio wave (control channel) is detected by the electric field strength detection circuit 11
It detects sequentially by 2. On the other hand, maps / shadowing /
The database 133 has map information on the traveling range of the vehicle in advance. The control unit 160 uses the position calculation circuit 132 for the map / shadowing database 133.
Received electric field intensity data (line-of-sight information) indicating whether communication with the communication satellite 20 from the electric field intensity detection circuit 112 is possible for each point on the map information corresponding to the current position information from Remember. As a learning effect, the mapping of where shadowing occurs can be done. Since the two receiving systems are provided as described above, the data (line-of-sight map information) of the map / shadowing / database 133 is created using the first antenna 110, the receiving unit 111, and the electric field strength detection circuit 112. While the second antenna 120, the receiver 121,
Also, communication information can be transmitted / received to / from the communication satellite 20 using the transmission unit 141. The communication satellite 20
The electric field strength of the radio wave from the second antenna 12 is detected.
0, the receiving section 121, and the electric field strength detection circuit 122 are also possible, and are an alternative means when a failure occurs in the first receiving system. On the contrary, the communication with the communication satellite 20 can be replaced by the first receiving system when the second receiving system fails.

In addition, each mobile station 11-14 sets the interval between the two antennas 110 and 120 appropriately,
Change in electric field strength according to vehicle traveling, that is, communication satellite 20
You can look ahead to changes in your outlook. Control unit 160
Is a speed / acceleration sensor 138 and a direction sensor 1
The traveling speed vector of the vehicle is calculated from the output of 39, and it is predicted from what time and for what time thereafter there is a line-of-sight window (communicable time period) in which communication is possible, depending on the distance between the antennas 110 and 120. For example, if the vehicle of the mobile station 10 is a long cargo truck, the distance between the first antenna 110 at the front part of the vehicle and the second antenna 120 at the rear part of the vehicle can be about 6 m or more. 40
It is possible to secure a time difference of 0.5 seconds or more in transmission and reception of radio signals with the communication satellite 20 even when traveling for km. Therefore, when the mobile station 10 travels in a building street and the visibility of the communication satellite 20 changes frequently, the detection result of the electric field strength detection circuit 112 is referred to and the visibility of the communication satellite 20 in the first antenna 110 at the front is viewed. Even if the state changes from the good state to the bad state, if the communication is within 0.5 seconds, the second antenna 120 on the rear side can be used for communication. In addition, by predicting the change in the line-of-sight to the communication satellite 20 by using the two antennas 110 and 120 in this manner, the accuracy of prediction of the available communication time zone using the map / shadowing database 133 described later is increased. be able to.

First, the operation of the present system when a call is made from a mobile station will be described by taking the case where the user A makes a call from the mobile station 11 to the operation management center 51 as an example.

The mobile station 11 has a control forward link channel (network management station 40-base station 30-communication satellite 20).
-The channel to be used is selected in accordance with the communication channel instruction from the mobile station 11), the communication path is set on the channel, and the return link (mobile station 11-communication satellite 2) is selected.
0-base station 31-public network 60-operation management center 51)
Send communication information with. Then, the communication forward link channel (operation management center 51-public network 60-base station 31-communication satellite 20-mobile station 11) receives communication information from the operation management center 51. The channel configuration for wireless communication via the communication satellite 20 is as follows, for example.

A sufficient number of channels corresponding to the number of mobile stations (50,000), for example, 200 channels of FDMA / SCPC (Frequency Divi).
sion Multiple Access / Sing
In the le Channel Per Carrier system, 10 KHz intervals, 12,200,000 + n × 1
0 KHz (n = 1, 2, ..., 200) 200 radio carriers for forward link and 14,200,000
+ N × 10 KHz with 200 waves of radio carrier for the return link. Then, 12,200,010 KHz (for forward link) and 14,200,010 KHz (for return link) of "n = 1" are used as the first channel. Similarly, “n =
A combination of "n = 3" is used as a communication channel for the 2 "and 3rd channels, and a specific channel among them is used as a control channel at the time of waiting, at the time of controlling incoming call, and at the time of controlling outgoing call. ~ 14 and base station 3
1 to 34 use the “n = m” channel designated by the network management station 40 through the control channel to transmit the radio carriers of the respective baseband signals to QPSK (Quadra).
ture Phase Shift Keying)
It modulates and transmits from each antenna, and also receives and demodulates a wireless carrier wave from the other party.

As another method of channel structure,
TDM (Time Divisi) for the forward link
on Multiplex) method, TDMA (Time Division Multiplex) for return link
le Access) method can be used. Still another method is CDMA (Cod
e Divisione Multiple Acce
The ss) method can be used.

In the mobile station 11 (mobile terminal device 100),
The control unit 160 recognizes the current position from each output of the position calculation circuit 132, the speed / acceleration sensor 138, and the azimuth sensor 139 and predicts the movement destination position with the passage of time in the future.
33, it predicts the communicable time zone indicating the start time and the duration for which communication with the communication satellite 20 becomes possible from the line-of-sight information corresponding to those positions on the map information, and inputs / outputs this prediction information. Display device 183 of section 180
To display. At this time, the information of the communicable area indicating the place where the communication with the communication satellite 20 is possible can be displayed at the same time.

When predicting the available communication time zone,
As described above, the first antenna 11 in the front part of the vehicle
It is possible to improve the prediction accuracy of the communicable time zone obtained by referring to the map / shadowing database 133 by performing the look-ahead of the line of sight of the second antenna 120 at the rear of the vehicle with respect to the communication satellite 20 using 0. Further, if the moving speed of the vehicle is low, it is possible to predict the communicable time zone only by pre-reading using the first antenna 110 without using the map / shadowing database 133.

A user such as a vehicle driver can display the display device 183.
By visually confirming the display contents of, it is judged whether the information to be transmitted can be completed within a certain waiting time,
If possible, the keyboard 184 is operated to key in the code of the desired message information, or the button for press talk is pressed and then the voice information is input by the microphone 182. Alternatively, the facsimile terminal 190 is operated to input facsimile information. If it is determined that the transmission cannot be completed within a certain waiting time, the above operation is performed after moving to a place where the transmission can be completed. At this time, if the communicable area is displayed on the display device 183, it is possible to immediately know in which direction and how much to move.

The voice information input to the microphone 182 is converted into an analog signal, and the voice encoder 172 compresses the information amount into digital data (hereinafter referred to as data) having a bit rate (codec speed) of 4.8 kbps under normal conditions. To be converted. By the way, in the case of wireless communication for transportation business, as the communication traffic requested by the user, the average hold time of voice communication is 30 seconds, and the average busy hour communication number per hour is about 3 times or less. Therefore, when performing voice communication, most requirements can be satisfied if there is a communicable time zone (line-of-sight window) that lasts about 30 seconds. Normally, the communication content is standard, and the voice information (144,000 bits =) for about 30 seconds is used.
(18,000 bytes) can be substituted by message information of 400 bytes or less. In this case, communication satellite 2
Communication information amount for 0 (transponder occupied time) is 1
/ 45 or less, the use efficiency of the expensive transponder is increased accordingly, and communication is possible even if the line-of-sight window is narrow. Further, in the case of message communication, the signal transmission speed on the wireless line with the communication satellite 20 can be set to a lower speed.
A byte can be transmitted in about 11 seconds. In this example, the transmission rate of voice data is 4.8 kbps and the transmission rate of messages and other data is 300 bps.

The control section 160 has a voice encoder 172,
In addition to the transmission data from the keyboard 184 or the facsimile terminal 190, the speed / acceleration sensor 138,
Data necessary for the operation management center 51 from the direction sensor 139, the position calculation circuit 132, or various sensors (not shown) (for example, a weight sensor for measuring the weight of a carried baggage) is sequentially stored in the transmission buffer memory 140. . In addition, the control unit 160 preliminarily sets the value of the unit communication time in which a predetermined probability of communication is obtained within a predetermined allowable waiting time calculated by statistically processing the communication time zone for each predetermined traveling range such as in an urban area. It is set. When the predicted start time of the communicable time zone arrives, the control unit 160 determines whether the data for each information type accumulated in the transmission buffer memory 140 can be completely transmitted to the communication satellite 20 within the duration, and if possible, the transmission unit. A transmission permission signal is output to 141 to instruct to read data from the transmission buffer memory 140. If it is not possible to complete the transmission within the communicable time zone, divide the data according to the unit communication time and transmit it multiple times over a plurality of communicable time zones scattered within a predetermined time period thereafter. Determines whether transmission can be completed, and if possible, outputs a transmission permission signal including the value of the unit communication time to the transmission unit 141. The value of this unit communication time may be notified to the transmission unit 141 in advance. When it is determined that the transmission cannot be completed within the predetermined time even if the data is divided, the control unit 160 displays the fact that the transmission is impossible on the display device 183 and outputs the tone sound by the tone signal generation circuit 161 from the speaker 181. And inform the user.

When the transmission unit 141 receives the transmission permission signal, the transmission unit 141 sequentially reads the data of the information from the transmission buffer memory 140, adds an error correction signal, and adds the error correction signal to the operation management center 5.
As one packet addressed to 1, the wireless carrier wave is modulated at the transmission rate according to the information type and transmitted to the communication satellite 20. At this time, if the unit communication time is designated, the data in the transmission buffer memory 140 is divided into a certain number of bytes corresponding to the information type and read so that the packet length that can be transmitted within this unit communication time is obtained. The data is packetized and transmitted to the communication satellite 20 (for example, assuming that the unit communication time is 1 second, about 600 bytes for voice information and about 30 bytes for message information). Even if the data division transmission of the voice information is performed, it is possible to perform pseudo real-time voice communication by recombining with the buffer memory on the receiving side. On the other hand, it is determined from the base station 31 via the communication satellite 20 whether the data transmitted from the transmission unit 141 to the communication satellite 20 can be normally transferred to the partner base station 31 within the time predicted to be communicable. This is performed by confirming the response in packet units through the receiving unit 121 and the control unit 160. When there is no response, the transmission unit 141 retransmits the packet. For this reason, the transmission unit 141 deletes only the portion of the read data in the transmission buffer memory 140, which corresponds to the packet which has been confirmed to be normally received and which has been transmitted, so that the packet data can be retransmitted from the beginning of the discarded packet data. .

During this transmission operation, the electric field strength detection circuit 112
When the shadowing is detected, the control unit 160 stops the output of the transmission permission signal, and the transmission unit 141 temporarily stops the reading of the data from the transmission buffer memory 140 and the transmission to the communication satellite 20. When shadowing is not detected by the electric field strength detection circuit 112 and the communication becomes possible again, the control unit 160 outputs the transmission permission signal again, the transmission unit 141 restarts the data reading from the transmission buffer memory 140, and the communication satellite is still on. The transmission is restarted from the packet whose reception confirmation is not performed in 20.

As an example of the actual conditions of communication time, probability (location rate), etc. in the urban area, the results of recent running experiments in the Tokyo city (total travel 200 km, L band (ETS-V) and K band (BS-3b) are shown. ) Use) is shown below. (Reference: (a) Proceedings of the 1993 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers (September 5th), B-163, Suzuki et al., "L band mobile satellite communication operation in the city considering waiting time""Evaluation of rate", (b) Ibid., B-179, Yoshimoto et al., "Results of Ku-band satellite mobile reception experiment in city") (1) Securing predetermined reception power with an average vehicle speed of 15 km / h A window with a visible duration of 1 second corresponds to a distance length of about 4 m, and the location rate at which further visibility continues is about 60%. Similarly, 10 seconds (about 40m), 30
The site ratios of the sight windows for seconds (about 120 m) or more are about 52% and about 40%, respectively. (2) The average moving speed of the vehicle is set to 15 km / h, and 10
The area ratio where the shadowing continues for more than a second (about 40 m) is about 30%. Similarly, 30 seconds (about 120
m), and the place ratio where the shielding continues for 70 seconds (about 290 m) or more is about 20% and 10% or less, respectively. (3) The line-of-sight ratio depends on the position of the communication satellite and the moving direction of the vehicle. 163 degree azimuth ETS-V from Tokyo
On the other hand, on a road within + -20 degrees in the east-west direction, about 6
1%, about 90 on roads within +/- 20 degrees north-south
%. With respect to BS-3b having an azimuth angle of 225 degrees, it is about 69% for roads within + -20 degrees in the east-west direction and about 84% for roads within + -20 degrees in the north-south direction. (4) Considering the time (maximum permissible waiting time) that can be waited from the start of communication until reaching the line-of-sight window, the probability of communication being possible (location rate) increases. Table 1 shows the approximate value of the communicable location ratio for each packet time length in consideration of the maximum allowable waiting time.

[0038]

[Table 1]

From Table 1, if the packet has a time length of 1 second, 70
If you wait for seconds, 90%, if you wait for 5 minutes, you can communicate almost 100%, and if you wait for 5 minutes, you can reach 90%, 1
It can be seen that if you wait 5 minutes, you will be able to communicate almost 100%.

Next, description will be made on the improvement of the communicability by changing the bit rate (decoder speed) when converting the audio information into digital data. The voice encoder 172 normally uses a bit rate (decoder speed) of 4.8 kbps.
In addition to the first coding rule of 2.4 kbps, the second coding rule of 2.4 kbps, which requires only half the amount of data (bits) even if the speech quality is poor, is provided. Therefore, if it is prepared to deteriorate the communication quality, the data encoded at 2.4 kbps is once accumulated and the data is transmitted by communicating with the communication satellite 20 at the same transmission speed as the data encoded at 4.8 kbps. The required time can be cut in half, and the probability of communication can be increased accordingly. When the user operates the input / output unit 180 to input the coding rule switching permission and it is predicted that the desired voice call time (normally, about 30 seconds) cannot be secured, the control unit 160 Is the audio encoder 17
2 is controlled, encoded at 2.4 kbps, and stored in the transmission buffer memory 140. The transmission unit 141 performs data reading from the transmission buffer memory 140 at the same 4.8 kbps as in the normal case, and the data is transmitted from the control unit 160.
The data is packetized and transmitted together with information indicating that the data has been coded according to the 4 kbps coding rule. The audio encoder 1
Even if the decoder speed of 72 is kept at 4.8 kbps and the control unit 160 processes the data in the transmission buffer memory 140 into the 2.4 kbps format, the same effect can be obtained.

Next, the improvement of the communication possibility by changing the bit rate when reading the data of the transmission buffer memory 140 will be described. Even when there is no shadowing due to a building shadow, the electric field strength of the radio signal with the communication satellite 20 deteriorates due to the influence of rainfall and the like, and the SN ratio decreases. When the user operates the input / output unit 180 to input the read speed reduction permission, the control unit 160 causes the electric field strength detection circuit 11 to operate.
When the output of 2 (or 122) detects that the SN ratio of the received signal from the communication satellite 20 is lower than a predetermined reference value, it outputs a read speed reduction instruction signal to the transmission unit 141. The transmission unit 141 reduces the bit rate for reading data from the transmission buffer memory 140 by a predetermined ratio (for example, 1/2), and packetizes and transmits it together with information indicating the bit rate reduction ratio. This increases the communication time, but the communication satellite 20
The band of the wireless carrier wave on the wireless line between and becomes narrower according to the bit rate reduction ratio, and the SN ratio is improved, so that the probability of communication can be increased. In particular, the effect becomes remarkable when used in a mobile satellite communication system using a wireless line that transmits at a high bit rate such as 9.6 kbps or 6.6 kbps.

The radio wave signal transmitted from the mobile station 11 is relayed by the communication satellite 20 and received by the satellite line transmitting / receiving device 320 through the antenna 310 of the base station 31 designated by the network management station 40. The satellite line transmitter / receiver 320 includes a narrow band filter for a wireless carrier signal, and
When the information indicating the bit rate reduction ratio is detected in the received signal from, the SN ratio is improved through the narrow band filter, and when there is no decrease in the bit rate, it is demodulated to digital data without passing through the narrow band filter. The signal is output to the signal processing device 330. The signal processing device 330 accumulates this data in the buffer memory 340 once, and if it is divided into a plurality of packets, combines them into one, and the data is read from the buffer memory 340 at a read speed inversely proportional to the bit rate reduction ratio on the mobile station 11 side. To restore the bit rate to its original value. In addition, the signal processing device 330 is the mobile terminal device 100.
Similar to 4.8 kbps coding rule and 2.4 kbp
A voice decoder and a voice encoder (both not shown) for converting between digital signals and analog signals having a coding rule of s are provided, and a 2.4 kbps coding rule is included in a received signal from the mobile station 11. When the information indicating that the data has been encoded is detected, the data is read from and decoded from the buffer memory 340 at a bit rate of 2.4 kbps, and when it is not 2.4 kbps, 4.8 kb.
Data is read and decoded from the buffer memory 340 at a bit rate of ps. Various signals such as message information, voice information, and facsimile information restored by the signal processing device 330 are converted into a signal format (digital signal or analog signal) suitable for the public network 60 by the public network interface device 350, and the public network 60 is converted. Sent to the operation management center 51 of the destination specified through
Transferred. The subscriber numbers of the operation management centers 51 to 53 corresponding to each user on the public network 60 are registered in advance in the respective base stations 30 to 33.

User terminal device 5 of operation management center 51
In 00, the communication control unit 520 receives various signals from the base station 31 through the public network interface device 510,
The data communication terminal 530 and the telephone terminal 54 according to the information type.
Either 0 or the facsimile terminal 550 is selected and output.

On the other hand, from the operation control center 51 to the mobile station 11
The information transmission to is carried out by the reverse route to the above. A signal corresponding to input information to the data communication terminal 530, the telephone terminal 540, or the facsimile terminal 550 is transferred to the base station 31 through the public network 60, converted into digital data, and temporarily stored in the buffer memory 340. At this time, 4.8 kbps coding rule is normally used for coding the voice information, and 2.4 kbps coding rule is used when the received signal from the mobile station 11 is coded according to the 2.4 kbps coding rule. To use. The signal processing device 330 is the satellite line transmitting / receiving device 32.
0 is controlled, data is sequentially read from the buffer memory 340, packetized to modulate a wireless carrier wave, and transmitted to the communication satellite 20. When the unit communication time is designated, the reading of data is divided into a predetermined number of bytes to form a plurality of packets. If the received signal from the mobile station 11 has been subjected to the bit rate reduction processing, the buffer memory 34
The read bit rate from 0 is reduced. Mobile station 11
If there is no normal reception response in packet units from, the packet is retransmitted.

The mobile station 11 receives the radio carrier signal from the base station 31 through the communication satellite 20 by the receiving section 121 having a narrow band filter built therein, and at the time of transmission, the transmission buffer memory 1
When the read bit rate reduction processing of 40 is performed, the SN ratio is improved through the narrow band filter, and when not performed, it is demodulated into digital data without passing through the narrow band filter and temporarily stored in the reception buffer memory 123. , If they are divided into a plurality of packets, combine them into one. When the read bit rate reduction process of the transmission buffer memory 140 is performed at the time of transmission, the control unit 160 reads out the data from the reception buffer memory 123 at the read speed inversely proportional to the reduction rate and restores the bit rate to the original type. Select the output destination accordingly. When the data is voice information, it is decoded (converted into an analog signal) by the voice decoder 170 based on the same coding rule as at the time of transmission, and is output as voice from the speaker 181 of the input / output unit 180. The message information and the facsimile information are output from the display device 183 and the facsimile terminal 190, respectively.

A tone signal for making a call, an incoming call, a call end, and various alarms to the user is generated by the tone signal generation circuit 161, and the tone synthesis circuit 171 outputs the tone signal to the same speaker 181 as the voice signal. Is output.

The network management station 40 monitors the communication on the channel of the communication satellite 20, and when the termination of the call from either the mobile station 11 or the base station 31 (the operation management center 51) is detected, the use of the communication channel is terminated. The mobile station 11 and the base station 31 stop the use of the channel and return to the reception (standby) state on the control channel, and the network management station 40 adds the signal to the free channel list for allocation. Register the channel. In addition, the network management station 40 records necessary charging information in the charging recording device 430.

Next, from the operation management center 51 to the mobile station 1
The operation in the case of calling 1 will be described. The user terminal device 500 of the operation management center 51 makes a call to the network management station 40 through the public network 60 and makes a call request to the mobile station 11. The satellite line controller 420 of the network management station 40 is the mobile station 1
Channel control for the base station 31 is performed in the same manner as when a call is made from 1 and the operation management center 51
To the base station 31. The operation management center 51 calls back to the base station 31 through the public network 60,
After connecting, it sends out a communication signal. After that, the mobile station 11
This is the same as when calling from.

As described above, message communication and voice communication can be performed between the administrator of the operation management center of each user and the vehicle driver of the mobile station.

In this embodiment, the carrier frequency band of the wireless line of the communication satellite 20 is Ku band (14 / 12G).
However, other frequency bands may be used. Also,
The transmission bit rates of voice data and message data are not limited to 4.8 kbps and 300 bps, respectively, and other bit rates can be used. Further, as a wireless position measurement system for detecting the current position, NAVSTAR / GPS (naviga) capable of highly accurate positioning by transmitting radio signals including time and orbit data from a plurality of satellites.
tiaon satellite time and
ranging / global positionin
g system), but equipped with appropriate receivers and position calculation circuits, respectively, to transmit position signal radio waves from a plurality of sign posts on the ground.
VM system (automatic vehicle)
monitoring system: automatic display system for vehicle position), and radio navigation system such as Loran C can be used.

[0051]

EFFECT OF THE INVENTION The mobile terminal device of the present invention has a communicable time zone indicating a start time and a duration for enabling communication with a stationary communication satellite whose visibility changes due to a fixed obstacle as the user moves. As a predictable communication possible predicting means, it is possible or impossible to communicate with the communication satellite preset in the sight map database based on the current position by the position detecting means and the movement detecting means and the destination position information with the passage of time in the future. The first means for predicting the communicable time zone by referring to the line-of-sight map information indicating the position, or the rear part in the moving direction by detecting the electric field strength of the received signal from the communication satellite by the first antenna provided in the front part in the moving direction A second antenna provided in the second antenna is provided with either one or both of the second means for prefetching the communicable time zone, and is converted into digital data. Information to be transmitted such as a message or voice that has been transmitted is temporarily stored in the transmission information storage means, and the digital data stored in the transmission information storage means is sequentially read and communicated during the communicable time period predicted by the communication possibility prediction means. Since the data is transmitted to the other party via a satellite, it is possible to improve the operating rate (communication probability) of the mobile satellite communication system in areas where shadowing frequently occurs on communication satellites, such as dense areas of buildings in cities. You can In addition, by having both the first means and the second means as the communicability prediction means, the map database can be created by self-learning while communicating information with the other party.

Further, the mobile terminal device of the present invention presets a unit communication time within which a predetermined probability of communication can be obtained within a predetermined allowable waiting time calculated by statistically processing the communication available time zone which varies with movement. Incidentally, by dividing the transmission digital data into packet units that can be transmitted in this unit communication time and performing transmission and retransmission control, it is possible to further increase the communicable probability.

In the mobile terminal device of the present invention, the first coding rule of the bit rate for which the coding means for analog / digital conversion of the voice signal is usually used and the speech quality is lower than that of the first coding rule, If the voice information that has a low second coding rule and cannot be transmitted within the predicted communicable time zone is converted into digital data by the first coding rule, the voice information is converted by the second coding rule. Is converted into digital data and is read from the transmission information storage means at the bit rate of the first encoding rule, whereby the communication required time can be shortened and the communicable probability can be further increased. further,
The receiving side from the communication satellite is provided with means for converting the bit rate such as a buffer memory, and the decoding means for performing digital / analog conversion of the audio signal also has the above-mentioned first coding rule and second coding rule. As a result, it is possible to restore the data, which has been digitized by the other party according to the second coding rule and has been shortened at the bit rate according to the first coding rule, and which has been transmitted, to the original bit rate for normal voice conversion, The probability of communication from the other party can be increased.

Further, the mobile terminal device of the present invention has an electric field strength detecting means for detecting the electric field strength of the radio wave signal from the communication satellite, and the SN ratio of the signal from the communication satellite is lower than the reference value. When detected, the read bit rate of the digital data from the transmission information storage means is reduced and transmitted, thereby narrowing the band of the wireless carrier signal on the wireless line with the communication satellite, improving the SN ratio, and further increasing the communicable probability. Can be increased. Further, by having a narrow band filter and a means for converting the bit rate such as a buffer memory on the receiving side, the SN ratio of the wireless carrier wave modulated by the digital data whose bit rate is lowered by the other party is passed through the narrow band filter. It is possible to recover the bit rate by demodulating it after the improvement, and it is possible to increase the probability of communication from the other party.

Further, in the mobile terminal device of the present invention, the communicability prediction means predicts the communicable time zone and the communicable zone indicating the place where communication with the communication satellite is possible, and the communicable time zone and the communicable zone By visually displaying the zone information on the input / output means, it becomes possible for the user to easily recognize the time and place where communication is possible and to respond promptly.

The mobile satellite communication system of the present invention is converted into digital data between the mobile terminal device having the above-mentioned communicability prediction means and transmission information storage means and the mobile terminal device through the always-observing communication satellite. It is equipped with a fixed station that performs two-way wireless communication of information, and the fixed station while moving in an area where the visibility of the communication satellites frequently fluctuates due to fixed obstacles such as urban areas where the mobile terminal devices are crowded. When communicating with a mobile terminal device, the information such as messages and voices stored as digital data is sequentially transmitted to fixed stations during the predicted communication time, so the operating rate (communication probability) is increased and the mobile terminal device can be used while moving. It is possible to economically service both message communication and voice communication over a wide area nationwide.

Further, in the mobile satellite communication system of the present invention, each of the mobile terminal device and the fixed station divides the transmission data into packet units which can be transmitted in the unit communication time set in advance, and controls transmission and transmission. By performing the retransmission control on arrival, the probability of mutual communication can be further increased.

Further, in the mobile satellite communication system of the present invention, when it is determined that the voice information cannot be transmitted by converting the voice information into data within the communicable time period predicted by the mobile terminal device according to the first coding rule. To the fixed station, and the mobile terminal device and the fixed station each convert the bit rate into the bit rate of the first coding rule by converting the data into the bit rate of the first coding rule to shorten the communication time. Then, the bit rate is returned on the receiving side, and the bit rate is decoded on the receiving side to further increase the mutual communicable probability.

Further, in the mobile satellite communication system of the present invention, when the mobile terminal device determines that the electric field strength of the radio wave signal from the communication satellite is below a predetermined level, the mobile terminal communication system notifies the fixed station of the determination result and the mobile terminal device. Each of the device and the fixed station reduces the bit rate of the data on the wireless line and transmits the data, and the receiving side improves the SN ratio through the narrow band filter and then restores the bit rate to determine the mutual communicable probability. It can be further increased.

Further, the mobile satellite communication system of the present invention comprises a plurality of user terminal stations each having a fixed station provided for each user to input and output information, and a communication satellite connected to the plurality of user terminal stations through a public network. Between the user terminal station, the mobile terminal device, and the communication satellites, which are connected to the communication satellite and the public network and pass through the base station. By providing the network management station that manages and controls the communication line of, the cost burden of the base station of the user can be suppressed, and the area can be further widened and the economy can be further improved.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment of a mobile terminal device of the present invention.

FIG. 3 is a diagram showing a detailed configuration of a base station, a network management station, and an operation management center of the embodiment of FIG. 1 and connections between them.

[Explanation of symbols]

 11, 12, 13, 14 Mobile station 20 Communication satellites 30, 31, ..., 34 Base station 40 Network management station 51, 52, 53, 54 Operation management center 60 Public network 100 Mobile terminal device 110, 120, 130 Antenna 111, 121 receivers 112 and 122 electric field intensity detection circuit 123 reception buffer memory 131 GPS receiver 132 position calculation circuit 133 map / shadowing database 138 speed / acceleration sensor 139 direction sensor 140 transmission buffer memory 141 transmission unit 160 control unit 170 voice decoder 172 voice encoder 180 input / output unit 320 satellite line transmitter / receiver device 330 signal processing device 340 buffer memory 350, 410, 510 public network interface device 500 user terminal device

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location 7605-5K H04B 7/26 A 7605-5K 109 M (72) Inventor Yoshihiro Hase 4-Kunuikitamachi, Koganei-shi, Tokyo 2-1 Ministry of Posts and Telecommunications Research Institute (72) Inventor Ichiro Izawa 1-6-19 Azabudai, Minato-ku, Tokyo 1-6-19 Ministry of Posts and Telecommunications Post Research Institute (72) Inventor Hideo Morita 5-7-1, Shiba, Minato-ku, Japan Japan Electric stock company

Claims (15)

[Claims] 1. A mobile terminal device which is mounted on a land-based mobile unit and which performs digital two-way wireless communication with a partner via a stationary communication satellite whose line-of-sight is changed by a fixed obstacle as the mobile unit moves. A wireless transmission / reception means for transmitting / receiving digital data to / from the communication satellite by a radio wave signal; an input / output means having a man-machine interface for mutually converting the digital data and input / output information; A line-of-sight map database that presets line-of-sight map information indicating positions that can and cannot communicate with the communication satellites within the range of movement, and detects the current position of the mobile unit based on signals from a wireless position measurement system. Position detecting means, movement detecting means for detecting the moving direction and speed of the moving body, the position detecting means and the A communicability predicting means for predicting a communicable time zone indicating a start time and a duration in which the communication with the communication satellite becomes possible according to the movement by referring to the sight map database based on the detection output of the movement detecting means; Transmission information storage means for temporarily storing information to be transmitted to the other party, which is input from the output means and converted into digital data, and storage in the transmission information storage means in the communication possible time zone predicted by the communication possible prediction means A mobile terminal device, comprising: a transmission control unit configured to sequentially read the generated digital data and transmit the digital data to the communication satellite via the wireless transmission / reception unit. 2. A mobile terminal device mounted on a land-based mobile body and performing digital two-way wireless communication with a partner via a stationary communication satellite whose line-of-sight is fluctuated by a fixed obstacle as the mobile body moves. , A radio signal is transmitted and received between a first antenna which is provided in a front portion of the moving body in the moving direction and receives a radio signal from the communication satellite, and a first antenna which is provided in a rear portion of the moving body in the moving direction and the communication satellite. A second antenna and an electric field intensity detection means for detecting the electric field intensity of the radio signal from the communication satellite received by the first antenna, and the digital data of the digital data is transmitted to and from the communication satellite by the radio signal. Wireless transmitting / receiving means for transmitting / receiving, input / output means having a man-machine interface for mutually converting the digital data and input / output information; And movement detection means for detecting speed, and communication indicating a start time and a duration for enabling communication with the communication satellite by the second antenna based on the detection outputs of the electric field strength detection means and the movement detection means. A communication availability predicting means for predicting an available time zone, a transmission information storage means for temporarily storing information to be transmitted to the other party, which is input from the input / output means and converted into digital data, and is predicted by the communication availability predicting means. And a transmission control unit that sequentially reads the digital data stored in the transmission information storage unit during the communicable time period and transmits the digital data to the communication satellite via the wireless transmission / reception unit. 3. The transmission control means obtains a predetermined communicable probability within a predetermined allowable waiting time calculated by statistically processing the communicable time zone with respect to the communication satellite, which fluctuates as the mobile body moves. The unit communication time to be set is set in advance, and the transmission digital data to be transmitted to the communication satellite is divided into packet units that can be transmitted in the unit communication time for transmission and retransmission control. Mobile terminal equipment. 4. The input / output unit includes a voice input unit for inputting voice and converting it into an analog signal, and an encoding unit for converting an analog signal from the voice input unit into a digital signal according to a predetermined encoding rule. Decoding means for inversely converting a digital signal into an analog signal in accordance with the predetermined coding rule, voice output means for converting the analog signal from the decoding means into voice and outputting the voice, character, numeral and symbol data. 2. A key input means for inputting, and a display means for visually displaying character, number and symbol data, enabling communication of voice information and message information in which a fixed phrase is coded. 2. The mobile terminal device according to 2. 5. The first encoding rule having the same bit rate as the bit rate on the wireless link with the communication satellite as the predetermined encoding rule by the encoding means, and the bit of which speech quality is lower than that of the first encoding rule. A second coding rule having a low rate, wherein the transmission control unit converts the voice into digital data according to the first coding rule within the communicable time period predicted by the communication communicative prediction unit. It is determined whether or not the information can be transmitted. If the information can be transmitted, the first encoding rule is designated to the encoding means, and if the information cannot be transmitted, the second encoding rule is designated. Along with the coding rule selection information indicating whether the coding rule is selected, the digital data of the audio information converted by the coding means and stored in the transmission information storage means is always the first data regardless of the selected coding rule. Encoding rule Mobile terminal apparatus according to claim 4, wherein the transmitting to the communication satellite at the same bit rate and bit rate. 6. The wireless transmission / reception means includes means for converting a bit rate of digital data received, and the decoding means uses the first encoding as the predetermined encoding rule.
Coding rule and the second coding rule, and when the transmission control means selects the second coding rule as the coding rule of the coding means, When a radio wave signal converted into digital data according to the coding rule No. 2 and modulated at the same bit rate as the bit rate of the first coding rule is received from the communication satellite, the digital data demodulated by the wireless transmission / reception means 6. The movement according to claim 5, wherein a bit rate is converted into a bit rate according to the second coding rule, and the decoding means performs analogization of the digital data according to the second coding rule. Terminal device. 7. The wireless transmission / reception means has an electric field strength detection means for detecting the electric field strength of a radio signal from the communication satellite, and the transmission control means outputs the electric field strength from the communication satellite based on the output of the electric field strength detection means. When it is detected that the SN ratio of the signal is lower than a predetermined reference value, the read bit rate of the digital data from the transmission information storage means is lowered, and the communication satellite is sent together with the information indicating the lowered read bit rate. The mobile terminal device according to claim 1, wherein the mobile terminal device is transmitted to the mobile terminal device. 8. The transmission / reception control means has a narrow band filter for narrowing the band of the received wireless carrier signal to improve the SN ratio, and a means for converting the bit rate of the received digital data. When the read bit rate is reduced by the method, when a radio wave signal modulated by the digital data whose bit rate is reduced by the other party is received from the communication satellite, the digital data is passed through the narrow band filter. 9. The mobile terminal device according to claim 7, wherein the mobile terminal device recovers the bit rate by demodulating. 9. The communication possible prediction unit predicts a communication possible zone indicating a place where communication with the communication satellite is possible together with the communication possible time zone where communication with the communication satellite is possible, The mobile terminal device according to claim 1 or 2, wherein the output means visually displays the information of the communicable time zone and the communicable zone. 10. The first transmitting / receiving means is provided at a front portion of the moving body in a moving direction and receives a radio signal from the communication satellite, and a first antenna is provided at a rear portion of the moving body in the moving direction. The mobile unit includes a second antenna that transmits and receives a radio wave signal to and from a communication satellite, and an electric field strength detection unit that detects the electric field strength of the radio wave signal from the communication satellite received by the first antenna. Of the map information within the movement range of the field of view map database in advance, and the detection output of the electric field strength detection means for each position on the map information corresponding to the current position detected by the position detection means as it moves. The line-of-sight map information is created by adding line-of-sight information indicating whether or not communication with the communication satellite is possible based on the second antenna. Mobile terminal apparatus according to claim 1, characterized in that Ri. 11. The mobile terminal device according to claim 1, wherein the communication satellite is stationary in a geosynchronous orbit, and the mobile terminal device moves in an area in which the visibility of the communication satellite changes due to a fixed obstacle as the mobile satellite moves. A fixed station that constantly views the communication satellite and performs two-way wireless communication of digitalized information with the mobile terminal device through the communication satellite, wherein the mobile terminal device inputs the input data as digital data. In addition to accumulating and storing, the communication possible time zone is predicted according to the change of the line of sight of the communication satellite due to movement, and the information accumulated in the predicted communication possible time zone is sequentially transmitted to the fixed station via the communication satellite. A mobile satellite communication system characterized by: 12. The mobile terminal device and the fixed station each have a predetermined permissible waiting time calculated by statistically processing the communicable time zone with respect to the communication satellite that varies with the movement of the mobile terminal device. A unit communication time with which a predetermined communication probability is obtained is preset, and transmission digital data to the other party through the communication satellite is divided into packet units that can be transmitted within the unit communication time, and transmission control and transmission failure 12. The mobile satellite communication system according to claim 11, wherein the retransmission control is performed at the time. 13. The mobile terminal device and the fixed station each have a first coding rule of the same bit rate as the bit rate on the wireless link with the communication satellite, and a bit rate lower than that but a bit rate. Means for performing mutual conversion of encoding and decoding between an analog signal of audio information and digital data according to a selected one of the second low encoding rules, and the bit of the digital data. Rate conversion means, the mobile terminal device determines whether or not the voice information converted into digital data according to the first encoding rule can be transmitted within the communicable time zone, and the determination result is fixed. The mobile terminal device and the fixed station, and when the transmission is impossible, the mobile terminal device and the fixed station respectively encode the digital data encoded according to the second encoding rule to the first encoding. Mobile satellite communications system of claim 11, wherein the decoding back to the second bit rate of the coding rule in converted to the bit rate transmitted by shortening the time required for communications receiver of. 14. A narrow band filter for narrowing the band of a wireless carrier signal on a wireless link with the communication satellite to improve the SN ratio, and each of the mobile terminal device and the fixed station converts a bit rate of digital data. The mobile terminal device determines whether the electric field strength of the radio signal from the communication satellite is below a predetermined level and notifies the fixed station of the determination result, and when the mobile terminal device is below a predetermined level, the mobile terminal device moves. Each of the terminal device and the fixed station lowers the bit rate of the digital data on the wireless line and transmits the digital data, and the receiving side restores the bit rate after improving the SN ratio through the narrow band filter. The mobile satellite communication system according to claim 11. 15. The fixed station is connected to a plurality of user terminal stations which are provided for each user and which inputs and outputs information, and the plurality of user terminal stations through a public network, and is connected to the communication satellite by a radio signal. It is composed of a base station that transmits and receives information converted into digital data, is a user terminal station that is connected to the communication satellite and the public network, and is a communication partner of the user terminal station through the base station. The mobile satellite communication system according to claim 11, 12, 13 or 14, further comprising a network management station for managing and controlling a communication line between the mobile terminal device and the communication satellites.