JPH09200855A - Mobile satellite communication and mobile communication system using ground cellular communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver coping with both ground system cellular communication and mobile satellite communication. SOLUTION: A GPS receiver 18 is used to detect a current position and the data are sent to a base station 40 via a satellite and a position discrimination device 42 in the base station discriminates which of a synchronization detection system for mobile satellite communication or a delay detection system for ground system cellular communication is more suitable based on information of a database 43. The result of discrimination is sent again to a mobile communication equipment 30, and a CPU 16 in the equipment 30 allows a changeover switch 8 to be thrown to the position of a synchronization detector 6 or a delay detector 7 selectively based on the discrimination data, then a demodulation signal adopting a proper detection system is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in mobile communication, and more particularly to a mobile communication device and a mobile communication system for demodulating a digitally modulated received wave.

[0002]

2. Description of the Related Art In a mobile communication system for performing both terrestrial cellular communication and mobile satellite communication, a demodulator of a mobile communication device receives signals received by both terrestrial cellular communication and mobile satellite communication. Will be done. In this case, the detection system of the demodulator performs the terrestrial cellular communication by using the differential detection system within the service range of the terrestrial cellular communication.

As described in Japanese Unexamined Patent Publication No. 5-252217, particularly in mobile communication, it is difficult to reproduce the reference carrier wave because severe fading occurs with the movement of the mobile body. In body communication, a differential detection method that does not require reproduction of a reference carrier is generally used.

On the other hand, in this communication system, mobile satellite communication is performed outside the service range of the terrestrial cellular communication. However, if the differential detection method suitable for the terrestrial cellular communication is used, the synchronous detection method is used. Bit error rate (Bi
This causes a problem that the (T Error Rate) characteristic is deteriorated. Conventionally, as a countermeasure against this, Japanese Patent Laid-Open No. 3-18214
As described in Japanese Patent Publication No. 4, there is a method of switching the detection method depending on the magnitude of the change in the reception level, but it is impossible to distinguish between the terrestrial cellular communication and the mobile satellite communication only by the change in the reception level, so that appropriate switching cannot be performed. It was impossible.

The PSK signal detection methods generally used in digital communication are mainly the synchronous detection method and the differential detection method as described above, and a comparison between the two will be described below.

In the synchronous detection method, a carrier wave that does not contain a modulation component or noise is reproduced from the received modulated wave, and the reproduced carrier wave is used as a reference for phase detection to perform demodulation.
Carrier recovery methods for the synchronous detection method include a frequency multiplication method, an inverse modulation method, and a remodulation method. In addition, the synchronous detection method generally uses a bit error rate (BitEr) with static characteristics.
This method is used in satellite communication because it has excellent error rate characteristics.

On the other hand, in the differential detection system, the received signal is demodulated by phase-detecting the signal one time slot before as a reference. The characteristic of the differential detection method is that it does not require carrier recovery, so the circuit can be simplified.
Stable characteristics can be obtained even on a transmission line that fluctuates significantly. In areas where mobile communication services are provided, especially in urban areas, waves such as reflected waves and diffracted waves arrive at the antennas of mobile terminals and cause fading. Under such an environment, the differential detection method is more advantageous than the synchronous detection method. Further, it is suitable for bursty transmission such as a time division multiple access (TDMA) system because of its excellent high-speed followability.

[0008]

When the communication range of a mobile communication device of the differential detection system, which is the mainstream in terrestrial communication, is expanded by satellite communication, the same C / N as that of the synchronous detection system, which is the mainstream in satellite communication, is used. (Carrier power to noise power ratio) Bit error rate per condition (Bit Error Rate)
Since the characteristics are inferior, it is disadvantageous in terms of required transmission power.

On the other hand, in the case of the coherent detection system used in satellite communication, under fading, the carrier-to-noise power ratio is deteriorated and the carrier synchronization is easily lost due to phase fluctuation. Therefore, when shared with terrestrial communication, fading that occurs in urban areas results in unstable operation compared to differential detection.

According to the present invention, the GPS (Global PB) is used to switch the differential detection system and the synchronous detection system by an appropriate system.
terrestrial cellular communication and mobile satellite communication by determining whether the current position of the mobile communication device is within or outside the terrestrial cellular communication service range by using the position information according to the positioning system) and using the database in the base station. It is an object of the present invention to provide a mobile communication device and a mobile communication system suitable for both.

[0011]

In order to achieve the above object, the present invention calculates the current position by a GPS receiver of a mobile communication device, transmits the position data to the base station, and the base station side Determines whether the current position of the mobile communication device is within the service range of the terrestrial cellular system or outside the service range, transmits the determination result to the mobile communication device, and the mobile communication device receives the determination result of the base station and determines It is characterized by comprising selection means for selecting either the first baseband signal or the second baseband signal according to the result. That is, the current position of the mobile communication device is transmitted to the base station based on the information on the database preset in the base station, and the information on the database of the base station and the current position of the mobile communication device are displayed. By comparison, if the current position of the mobile communication device is within the service range of the terrestrial cellular system, the delay detection method is used, and if it is outside the service range, the synchronous detection method is selectively switched to use the detection method. To do.

The mobile communication system of the present invention is a mobile communication device in which GPS (Global Position) is used.
Ning System) to measure the current position, transmit the measured data to the base station, and determine whether the current position of the mobile communication device is within the service range of terrestrial cellular communication or outside the service range by the database in the base station. The result is sent to the mobile communication device, and the detection circuit in the mobile communication device is used by selectively switching between the synchronous detection circuit and the delay detection circuit. In other words, in the urban area, the received electric field is high, and the differential detection method, which is advantageous in fading characteristics, is used. Then, outside the service range of the terrestrial cellular communication, the error rate (Bit Error Rate) is set by the differential detection method in order to communicate effectively via the satellite and effectively use the electric power.
A synchronous detection method with excellent characteristics is used. As a result, the demodulation signal can be obtained in a good state because the detection method suitable for the communication system is always used.

[0013]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a mobile communication system and a mobile communication device according to the present invention.

The GPS signal transmitted from the GPS satellite 100 is received by the GPS antenna 17 of the mobile communication device 30, and the current absolute position is calculated by the GPS receiver 18.

This calculation method is performed as follows.

Here, GPS (Global Position)
Ioning System) is a worldwide high-accuracy position measurement system, and is widely used for navigation and surveying of aircraft, ships and automobiles.

GPS has an orbital altitude of about 20,000 km and a cycle of about 12
Time, orbital inclination angle 55 degrees, on 6 different orbital planes,
Twenty-four satellites are arranged for optimum coverage, including three spare satellites.

The principle of GPS is that the navigation signal from the satellite is P
A PSK wave that is spread spectrum modulated with an N (Pseudo Noise) code, and is 1575.42M
Two waves of Hz (F1) and 1227.6 MHz (F2) are emitted. This code is P code (Precisi
on Code) and C / A code (Clear and
There are two types: acquisition code). P code is 10.23 Mbps, cycle is 1 week, F
Ionization can be corrected by using two waves of 1 and F2, and it is intended for precise positioning. C / A code is 1.023Mbp
s, with a period of about 1 millisecond, only F1 is used.

There is a direct method as a typical positioning method using GPS, which is used for positioning a moving body. In the present invention, by using this direct method positioning, signals are received from a plurality of satellites and the navigation information (time of the satellites, orbital elements, etc.) is detected to calculate the absolute position of the user.

The calculation result of the GPS receiver 18 (position information of the mobile communication device 30) is sent to the transmitter / receiver 21 in the mobile communication device 30 and is combined with the transmission data in the multiplex circuit (MUX) 13, Modulated by a modulator 12, an up converter (U / C) 11, a high power amplifier (HPA) 10,
The signal is transmitted from the antenna 1 through the duplexer (DUP) 3 to the base station 40 through the communication satellite 45.

Mobile communication device 30 received by base station 40
The position information of 1 is demodulated by the transmitter / receiver 41 to be a baseband signal and sent to the position determination device 42.

The position determination device 42, which has received the position information of the mobile communication device 30, collects the data of the service range of the terrestrial cellular communication and the position data of the mobile communication device which are stored in advance in the database (DB) 43. By comparison, it is determined whether or not it is within the service range of terrestrial cellular communication.

The database used here may be a CD ROM, a memory card, an EEPROM, a flash memory or the like.

The determination result obtained by the position determination device 42 is sent again to the transceiver 41 in the base station 40 and modulated,
The signal is transmitted from the antenna 44 of the base station 40, passes through the communication satellite 45, and is received again by the antenna 1 of the mobile communication device 30, and the DUP3 of the transceiver 21 and low noise increase (LN).
It is demodulated by the demodulator 22 through A) 4 and the down converter (D / C) 5.

At this time, the synchronous detection circuit 6 is selected by the changeover switch circuit 8 of the demodulator 22 in the transmitter / receiver 21 and outputs the demodulated signal.

The demodulated position determination data of the mobile communication device is then used as a control device (CPU) in the mobile communication device 30.
16 is sent.

The CPU 16 controls to switch the changeover switch circuit 8 in the demodulator 22 based on the position determination data.

That is, the changeover switch circuit 8 selects either the synchronous detection signal or the delayed detection signal and outputs it to the demultiplexing circuit (DEMUX) 9. If the current position is within the service range of terrestrial cellular communication, the delay detector 7 is selected, and if it is outside the service range, the synchronous detector 6 is selected.

The GPS antenna 17 can be shared with the antenna 1 if the characteristics of the communication antenna 1 used in the mobile communication device 30 satisfy the required antenna characteristics of the GPS receiver.

Although the base station 40 explained above transmits and receives with the mobile communication device 30 via the communication satellite 45,
It also has the function of transmitting and receiving terrestrial cellular communications.

That is, the present invention uses the same frequency band for both mobile satellite communication and terrestrial cellular communication, and
The same system configuration is used.

Therefore, the antenna 44 of the base station 40 can transmit and receive signals for not only mobile satellite communication but also terrestrial cellular communication.

Similarly, for the mobile communication device 30,
The antenna 1 can support not only mobile satellite communication but also terrestrial cellular communication.

FIG. 2 shows a synchronous detection circuit 1 according to this embodiment.
6 is a block diagram showing a configuration example of No. 6; FIG. The reception signal from the reception signal input terminal 50 is branched into two and is input to the phase detection circuit 51 and the carrier wave recovery circuit 52, respectively. The carrier wave regenerating circuit 52 removes the modulation component and noise component from the received signal to regenerate the carrier wave, and the phase detection circuit 51 performs phase detection on the received signal from the received signal input terminal 50 with reference to the carrier wave. The baseband signal is output to the timing extraction circuit 53 and the identification reproduction circuit 54.

The identification reproduction circuit 54 reproduces the baseband signal with reference to the timing signal extracted by the timing extraction circuit 53, and outputs the reproduced digital signal from the output terminal 55.

FIG. 3 shows a differential detection circuit 7 according to this embodiment.
FIG. 3 is a block diagram illustrating a configuration example of FIG. Received signal input terminal 6
The received signal from 0 is split into two and input to the phase detection circuit 62 and the 1-time slot delay circuit 61, respectively.

The phase detection circuit 62 performs phase detection with the received signal delayed by the one time slot delay circuit 63 as a reference, and outputs the obtained baseband signal to the timing extraction circuit 63 and the discrimination reproduction circuit 64. The identification reproduction circuit 64 reproduces the baseband signal with reference to the timing extracted by the timing extraction circuit 63, and outputs the reproduced digital signal from the output terminal 65.

Finally, FIG. 4 is a diagram showing the operating mode of this embodiment.

Now, the mobile communication device 30 shown in FIG. 1 is installed in the mobile station 70.

When the mobile station 70 is within the range 80 of the terrestrial cellular communication service of the base station 40, the position information from the GPS receiver 18 of the mobile communication device 30 in FIG. Base station 4 via communication satellite 45
0 to the position determination device 42.

The position determination device 42 sends the first determination signal again to the CPU 16 of the mobile communication device 30 of FIG. 1 via the satellite 45.
To the changeover switch circuit 8.

The changeover switch circuit 8 selects the demodulated signal of the delay detection circuit 7.

On the other hand, when the mobile station 71 is outside the terrestrial cellular communication service range 80 of the base station 40, in order to communicate with the base station 40 via the communication satellite 45, the base station 40 The internal position determination device 42 sends the second determination signal to the mobile communication device 30 of FIG. 1, and the changeover switch circuit 8 of the CPU 16 in the mobile communication device 30 outputs the demodulation signal of the synchronous detection circuit 6.

When it is determined that the mobile communication device 30 of FIG. 1 is clearly within the service range 80 of the terrestrial cellular communication, the changeover switch circuit 8 may output the demodulated signal of the differential detection circuit 7. It is possible.

[0046]

As described above, the mobile communication system according to the present invention measures the current position of the mobile communication device, transmits the data to the base station via the satellite, and transmits the information in the database to the base station. As a reference, it is determined whether the current position of the mobile communication device is within the service range of the terrestrial cellular communication or out of the service range, and the determination result is transmitted to the mobile communication device again, and the detection method is either a delayed detection signal or a synchronous detection signal. By selecting one of them, the detection method suitable for the system is always used as the mobile communication device, so that the demodulated signal can be obtained in a good state.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a mobile communication system and a mobile communication device of the present invention.

FIG. 2 is a block diagram showing an embodiment of a synchronous detection circuit.

FIG. 3 is a block diagram showing an embodiment of a differential detection circuit.

FIG. 4 is a schematic diagram showing an operational form of the present invention.

[Explanation of symbols]

 1 Communication Antenna 3 Duplexer 4 Low Noise Amplifier (LNA) 5 Down Converter (D / C) 6 Synchronous Detector 7 Delay Detector 8 Switching Switch Circuit 9 Demultiplexing Circuit (DEMUX) 10 High Power Amplifier (HPA) 11 Up Converter (U / C) 12 Modulator 13 Multiplex circuit (MUX) 15 I / F circuit 16 CPU 17 GPS antenna 18 GPS receiver 19 Reception terminal 20 Transmission terminal 21 Transceiver 22 Demodulator 30 Mobile communication device 40 Radio base station 41 transceiver in radio base station 42 position determination device 43 database (DB) 44 radio base station communication antenna 45 communication satellite 50 received signal input terminal 51 phase detection circuit 52 carrier recovery circuit 53 timing extraction circuit 54 identification recovery circuit 55 demodulation signal Output terminal 60 Received signal input Input terminal 61 1 time slot delay circuit 62 phase detection circuit 63 timing extraction circuit 64 identification reproduction circuit 65 demodulated signal output terminal 100 GPS satellite

Claims (9)

[Claims] 1. In a mobile communication system for connecting a mobile communication device and a base station using mobile satellite communication and terrestrial cellular communication, the mobile communication device itself measures an absolute position, and the absolute position Data is transmitted to the base station using the mobile satellite communication, and it is determined whether or not it is within the service range of the terrestrial cellular communication stored in advance in the base station, and based on the determination result. A mobile communication system using mobile satellite communication and terrestrial cellular communication, wherein the detection system of the mobile communication device is selected from differential detection and synchronous detection. 2. The mobile communication system using mobile satellite communication and terrestrial cellular communication according to claim 1, wherein positioning of the absolute position uses a global positioning system (GPS) receiver. 3. A mobile communication system for connecting a mobile communication device and a base station using mobile satellite communication and terrestrial cellular communication, wherein the mobile communication device extracts a first baseband signal from a received signal. A differential detection circuit for detecting, a synchronous detection circuit for detecting a second baseband signal from the received signal, a position detecting means for detecting a current position of the mobile communication device, and a current position of the mobile communication device. A transmitter that transmits to the base station, and a switch that receives position determination data from the base station and selects one of the first baseband signal and the second baseband signal based on the position determination data. A circuit, the base station stores a database for storing service area information of the terrestrial cellular communication, and before receiving position information transmitted from the mobile communication device. Note that the mobile communication device includes: a determination unit that determines whether or not the current position of the mobile communication device is within the service area; and a transmission unit that transmits determination data to the mobile communication device based on the determination unit. A mobile communication system using mobile satellite communication and terrestrial cellular communication. 4. The position detecting means comprises a global positioning system (GPS) receiver.
A mobile communication system using the described mobile satellite communication and terrestrial cellular communication. 5. A mobile communication system for connecting a mobile communication device and a base station using mobile satellite communication and terrestrial cellular communication, wherein the mobile communication device extracts a first baseband signal from a received signal. First detecting means suitable for detecting the terrestrial cellular communication, and detecting a second baseband signal from the received signal,
A second detecting means suitable for the mobile satellite communication; a position detecting means for detecting the current position of the mobile communication device; a transmitter for transmitting the current position of the mobile communication device to a base station; A mobile unit, comprising: a switching circuit that receives position determination data from a station and selects one of the first baseband signal and the second baseband signal based on the position determination data. A mobile communication system using satellite communication and terrestrial cellular communication. 6. The position detecting means comprises a global positioning system (GPS) receiver.
A mobile communication system using the described mobile satellite communication and terrestrial cellular communication. 7. The mobile satellite communication and terrestrial cellular system according to claim 5 or 6, wherein the first detection means comprises a differential detection circuit, and the second detection means comprises a synchronous detection circuit. Mobile communication system using communication. 8. A mobile communication system for connecting a mobile communication device and a base station using mobile satellite communication and terrestrial cellular communication, wherein the base station is a database for storing service area information of the terrestrial cellular communication. And a determination unit that receives the position information transmitted from the mobile communication device and determines whether or not the current position of the mobile communication device is within the service area, and the determination data based on the determination unit. A mobile communication system using mobile satellite communication and terrestrial cellular communication, comprising: transmitting means for transmitting to the mobile communication device. 9. The mobile satellite communication and the mobile satellite communication according to claim 1, wherein the mobile satellite communication and the terrestrial cellular communication have the same system configuration and are mutually accessible. A mobile communication system using terrestrial cellular communication.