JP3189316B2 - Mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system capable of position measurement using multiple beams.

[0002]

2. Description of the Related Art A multi-beam type mobile communication system shown in FIG. 8 has been proposed as a mobile communication system supporting communication between each mobile unit and a ground station. The mobile communication system shown in this figure includes a ground station 101 provided on the ground side, and a communication satellite 102 arranged far above the ground. A feeder link is provided between the ground station 101 and the communication satellite 102. In addition, communication is performed between them, and the respective areas 104a to 104n of the cover area 103 are irradiated with the respective spot beams 105a to 105n by the communication satellite 102 so that the respective areas 104a to 104n are irradiated.
The communication between the mobile unit 107 and the ground station 101 is performed by performing communication with the mobile unit 107 (see FIG. 9) existing within 4n.

In the mobile communication system based on the multi-beam system, since the beam is narrowed down to a narrow range using the large-diameter antenna 106, the antenna gain of the communication satellite 102 is reduced as compared with the case of the single beam. It is considered that the mobile communication system 107 will be the mainstream of the satellite communication system in the future because it can improve the size of the mobile unit 107 and increase the communication capacity.

[0004]

However, in the above-mentioned conventional mobile communication system, as shown in FIG. 9, a plurality of areas 104a to 104n are adjacent to the area 104a where the mobile 107 is located. 104b-1
04g, the moving body 107 is in one area 104a.
When moving from to the other region 104b to 104g, the beam used on the moving body 107 side must be switched to a beam corresponding to the next region. Traditionally,
Switch to a certain procedure in advance, for example, from 104a to 104b
If switching is not successful, switch to 104c
Switching according to a predetermined procedure
I was However, this method of beam switching is
Switching is not always successful the first time.
Beam switching may be repeated many times until switching is successful
However, it was not an efficient method.

An object of the present invention, when the switching of the beam used in the moving body side is required, seek priority in accordance with the position of the moving body, by switching the beam according to the priority, efficiency beam It is an object of the present invention to provide a mobile communication system capable of performing a good switching.

[0006]

In order to achieve the above object, a mobile communication system according to the present invention communicates with a ground station.
Communication satellites communicate with each other,
Irradiates the mobile terminal and the ground in each area.
A mobile communication system designed to communicate with a superior
System detects that a beam switch is required.
Detecting means for detecting the position information of the mobile terminal.
Information acquisition means and the mobile terminal
Priority for which beam to switch to best
And determining priority determining means, Bee by the detecting means
When it is detected that switching of the
Switch beams according to priority until switching is successful
A mobile communication system comprising: a beam switching unit for switching.

[0007] In the above configuration, when the need to switch the beam moving body uses to communicate has occurred, to determine the priority of the switched beam based on the position information of the movable body,
By switching beams based on this priority,
Thus, beam switching can be performed efficiently.

[0008]

FIG. 1 is a block diagram showing an example of a mobile communication system of the RDSS system to which an embodiment of the beam switching system according to the present invention is applied. The mobile communication system shown in FIG. 1 includes a ground station 1 installed on the ground, a plurality of geostationary satellites 2a and 2b arranged in the sky, and a mobile terminal 3 mounted on a vehicle running on the ground. To support spread spectrum communication between the ground station 1 and the mobile terminal 3 using the respective geostationary satellites 2a and 2b, and at the same time, the propagation of radio waves transmitted and received via the respective geostationary satellites 2a and 2b. When the position of the mobile terminal 3 is calculated from the time and the position information of each of the geostationary satellites 2a and 2b and the beam switching on the mobile terminal 3 side becomes necessary, the area to which the mobile terminal 3 is directed is Then, the beam is selected in descending order of the probability, and the beam is switched efficiently.

In this case, in the spread spectrum communication system used in this mobile communication system, the transmitter 5 side operates the first-stage balanced modulator 7 based on the input information signal as shown in FIG. After balanced modulation of the carrier signal, the pseudo-noise signal (P
In N), spread spectrum modulation is performed again to generate a spread spectrum modulated wave signal, which is transmitted from the transmitting antenna 9. On the receiver side, when a spread spectrum modulated wave signal is received by the receiving antenna 10, the signal is amplified by a high frequency amplifier (RF. AMP) 15 and detected by the acquisition circuit 11 to be detected by the PN generator. 12 while outputting a pseudo noise signal (PN) from DL
An L circuit 13 is operated to despread the spread spectrum modulated wave signal based on the pseudo noise signal, and then demodulated by a demodulator 14 and included in the spread spectrum modulated wave signal received by the receiving antenna 10. Play back the information signal that is being played.

[0010] Thus, the PN code in the received spread spectrum modulated wave signal and the PN code generated on the receiving side are shifted by one chip or more, and the received spread spectrum modulated signal is processed as simple noise. The information signal contained in the wave signal is reproduced.

FIG. 3 is a block diagram showing an example of a transceiver provided on the moving body side based on such an operation principle.

The transceiver shown in FIG.
A keyboard / display circuit 30 used as a machine interface; a baseband processor circuit for processing data output from the keyboard / display circuit 30 and processing received data; Modem 32 that performs convolution processing and spread spectrum processing on the received data and despreads the received data.
And an up-converter circuit 33 for converting a spread spectrum signal output from the modem 32 into a transmission frequency signal.
And a high power amplifier circuit 34 for amplifying the transmission frequency signal output from the up-converter circuit 33, and radiating the transmission frequency signal output from the high power amplifier circuit 34 as a radio wave or receiving the received radio wave. An antenna 35 for converting the signal into a frequency signal, a low-noise amplifier circuit 36 for amplifying the reception frequency signal output from the antenna 35, and a reception-frequency signal output from the low-noise amplifier circuit 36 Down-converter circuit 37 for supplying the modem 32
And

In this case, as shown in FIG. 4, the modem 32 encodes data output from the baseband processor circuit 31 and an encoder circuit 40 which spreads the data output from the encoder circuit 40 by spectrum spreading. A spread spectrum circuit 41 that outputs to the up-converter circuit 33, an A / D converter circuit 42 that digitizes the intermediate frequency signal output from the down-converter circuit 37, and data output from the A / D converter circuit 42. A digital matched filter circuit 43 which takes a correlation with a preset PN code and generates a synchronizing signal when these correlations exist, and the A / D converter based on the synchronizing signal output from the digital matched filter circuit 43. The digital signal output from the converter circuit 42 is inverted A delay locked loop circuit 44 for tram diffusion, the delay locked loop circuit 44
And a forward error correction circuit 46 for performing error correction on the digital signal output from the Costas loop circuit 45.

When a user inputs a message from the keyboard of the keyboard / display circuit 30, the message is transmitted to the baseband processor circuit 31.
Is processed in accordance with a preset protocol, and is passed to the modem 32. Then, after the convolutional coding and the spread spectrum processing are performed by the modem 32, it is converted into the transmission frequency by the up-converter circuit 33, amplified by the high power amplifier circuit 34 and transmitted from the antenna 35 to the geostationary satellites 2 a and 2 b. It is radiated toward.
Conversely, when receiving a message, the radio wave received by the antenna 35 is amplified by the low noise amplifier circuit 36 and converted to an intermediate frequency signal by the down converter circuit 37. Thereafter, the digital signal is converted into a digital signal by the A / D converter circuit 42 of the modem 32, and the digital matched filter circuit 43 correlates with a preset PN code. Is generated and supplied to the delay locked loop circuit 44.

Thus, the digital matched filter circuit 43 is provided by the delay locked loop circuit 44.
The internal PN code generator is synchronized based on the synchronizing signal output from, and the received signal is despread to generate a despread signal, which is decoded by the Costas loop circuit 45 and the forward error correction circuit 46. Baseband processor circuit 31 as data of a predetermined format
Passed to.

The baseband processor circuit 31 performs a process corresponding to the content of the data, for example, if the received content is a message, a process of displaying the content on the keyboard / display circuit 30.
If the received content is the designation of the switching beam, a process of storing the priority of the beam in the internal register of the baseband processor circuit 31 is performed.

In this embodiment, the chips of the PN codes of the beams A to G used in the adjacent regions 20a to 20g are shifted as shown in FIG.
By shifting the frame (one cycle of the PN code) timing for each of the adjacent beams A to G as shown in FIG.
Even if ~ G overlaps, the beam other than the transmitted / received beam is treated as noise, and when the beam is switched, the generation timing of the PN code is simply shifted by the known frame offset value between the beams. so,
Select the next beam.

Next, the beam switching operation of this embodiment will be described with reference to FIGS. Now, each area 20a to 20g in the cover area and each beam A to
5, the mobile terminal 3 to be communicated is located in the central area 20a, and the PN code of the beam A transmitted and received by the mobile terminal 3 and the mobile terminal 3 It is assumed that the information is demodulated in perfect synchronization with the PN code generated in step (1).

In this state, when the mobile terminal 3 moves in the direction of the beam B area 20b, each of the geostationary satellites 2a, 2a
Since the connection state with b changes and the noise margin decreases,
The bit error rate of the beam A received by the mobile terminal 3 deteriorates, and this appears as a change in the state metric value of the Viterbi decoder provided on the mobile terminal 3 side.

Then, the bit error rate of the mobile terminal 3 becomes worse than the preset threshold level Th1 as shown in FIG. 7, and the mobile terminal 3 detects this and detects the switching priority order request command. Is generated and transmitted, the ground station 1 receives this via each geostationary satellite and transmits the propagation time for each geostationary satellite 2a, 2b and the geostationary satellite 2a, 2b
The position of the mobile terminal 3 is calculated from the position information.

After that, the ground station 1 determines from the position information of the mobile terminal 3 which area the mobile terminal 3 has the highest probability of going to next, and based on the determination result, in the descending order of the probability of going. , And calculates the priority of the beam, and notifies the mobile terminal 3 of the priority information obtained by this calculation operation via the geostationary satellite 2a.

When the priority information is stored by the mobile terminal 3 and the bit error rate becomes lower than a preset threshold level Th2,
The beam is switched based on the priority information.

When the mobile terminal 3 generates and transmits a command indicating that the beam switching has succeeded and the beam switching has succeeded, the ground station 1
a, 2b to receive each of the geosynchronous satellites 2a, 2b.
The position of the mobile terminal 3 is calculated from each propagation time and the position information of each of the geosynchronous satellites 2a and 2b, and the contents of the database in which the data for calculating the priority of beam switching is calculated from the position information. Update.

As described above, in this embodiment, the propagation time for each satellite line generated when communication is performed between the mobile terminal 3 and the ground station 1 via the geostationary satellites 2a and 2b, The position information of the mobile terminal 3 is calculated based on the position information of the geostationary satellites 2a and 2b, and based on the calculation result, the priority of the beam to be used next is determined in the order in which the mobile terminal 3 is likely to proceed. Thus, when it is necessary to switch the beam used on the mobile terminal 3 side, it is possible to obtain the priority of the beam to be switched according to the position of the mobile terminal 3 and efficiently switch the beam.

In the above-described embodiment, the beam switching is performed using only the position information of the mobile terminal 3. However, the vector information is created in consideration of the moving direction and speed of the mobile terminal 3. And use this,
Beam switching is performed by using information on the coverage areas 20a to 20g of the beams A to G and information for optimizing beam switching such as a switching method of the beams A to G. The accuracy of the performed beam switching priority calculation may be improved.

In this case, a terrestrial magnetism sensor is mounted on the mobile terminal 3 to detect the direction in which the mobile terminal 3 is facing, and the traveling direction information is created based on the detection result, and the mobile terminal 3 is mounted. When speed information is taken out from a speedometer of a vehicle or the like, vector information is created, this is stored in the mobile terminal 3, and when communicating with the ground station 1, the vector information is transmitted together with a switching priority order request command. Then, the ground station 1 receives the signal.

In the above-described embodiment, the bit error rate on the mobile terminal 3 side is set to the threshold level Th.
When the bit error rate becomes worse than 1, the beam priority calculation is performed, and the bit error rate becomes equal to the threshold level Th2.
When the bit error rate becomes worse than the threshold level Th1, the beam priority is calculated, and the beam is switched at the same time. You may do it.

Further, the number of threshold levels may be set to three or more to further divide the processing steps.

In the above embodiment, the ground station 1 calculates the optimum beam to be used next by the mobile terminal 3 from the position information of the mobile terminal 3. This calculation may be performed on the mobile terminal 3 side, or information necessary for the calculation may be stored on the mobile terminal 3 side.

In the above embodiment, the RDS
Although the present invention is described by taking the S system as an example, the beam switching according to the present invention is applied to a mobile communication system provided with a means for obtaining position information using another system, for example, another positioning system such as a GPS. A method may be applied.

In the above-described embodiment, the communication is performed by the spread spectrum communication method.
The difference between the characteristics of adjacent beams A to G is known,
It is self-evident that the present invention can be applied to any communication system that can switch beams simply by specifying the method of switching beams A to G.

[0032]

As described above, according to the present invention, when it is necessary to switch the beam to be used on the moving body side, the priority of the beam to be switched is determined according to the position of the moving body, and the efficiency of the beam is determined. Can be switched well.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a mobile communication system of an RDSS system to which an embodiment of a beam switching system according to the present invention is applied.

FIG. 2 is a block diagram showing an outline of a spread spectrum communication system used in the mobile communication system shown in FIG.

FIG. 3 is a detailed block diagram showing an example of a transceiver provided in a mobile terminal used in the mobile communication system shown in FIG.

FIG. 4 is a block diagram showing a detailed configuration example of the modem shown in FIG. 3;

FIG. 5 is a schematic diagram showing a relationship example between each area and a beam in the mobile communication system shown in FIG.

FIG. 6 is a schematic diagram showing an example of a synchronization relationship between each beam and a receiver in the mobile communication system shown in FIG.

FIG. 7 is a schematic diagram showing an example of a beam switching timing in the mobile communication system shown in FIG. 1;

FIG. 8 is a block diagram showing a configuration example of a conventionally proposed multi-beam type mobile communication system.

9 is a schematic diagram showing a beam switching method in the mobile communication system shown in FIG.

[Description of Code] 1 Ground Station 2a, 2b Geostationary Satellite 3 Mobile Terminal 20a-20g Area A-G Beam

Continuation of the front page (56) References JP-A-58-150340 (JP, A) JP-A-60-90441 (JP, A) JP-A-2-171039 (JP, A) JP-A-2-121418 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H04B ^7/ 14-7/26 102 H04Q ^7/ 00-7/38

Claims (1)

(57) [Claims] 1. A communication between a ground station and a communication satellite.
The satellite irradiates each area on the ground with a beam, and
Communication between the mobile terminal and the ground station
In the mobile communication system made in the above, detecting means for detecting that beam switching is required, position information obtaining means for obtaining position information of the mobile terminal, and the mobile terminal using the position information Which is next
To determine if switching to a system is optimal
Beam switching is required by the priority determination means and the detection means.
When a beam is detected, the above priority is applied until beam switching is successful.
Beam switching means for switching beams according to the order
A mobile communication system comprising: