JPH04354213A - Synchronization system in mobile communication system utilizing still satellite - Google Patents

Abstract

PURPOSE:To provide the synchronization system utilizing a still satellite in which the synchronization of the entire mobile communication system is attained without revision of a synchronization system of a ground system. CONSTITUTION:A reference burst generator 102 generates a reference burst a synchronization reference level of the system by using a clock from a highly stable reference clock oscillation source 101 mounted on a still satellite 100 and plural satellite line base stations 200 of zone configuration through a TDMA line are subjected to multiple address communication. The satellite line base station 200 establishes the clock synchronization and the frame synchronization of ground system based on the reference burst and a clock and a synchronizing signal are fed to a mobile communication base station 300 of small zone configuration. The mobile communication base station 300 manages mobile stations 400 of each zone.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization system in a mobile communication system using geostationary satellites.

0002

BACKGROUND OF THE INVENTION As terrestrial mobile communication systems, automobile and mobile phone systems with small zone configurations are becoming mainstream. This method can improve the frequency utilization rate of mobile communications. A base station is installed in each cell, which is a wireless zone, and controls calls within the cell. TDMA communication systems are becoming mainstream in cellular systems with small zone configurations, and in this TDMA communication system, clock synchronization and frame synchronization at each base station are important. However, in a wide-area mobile communication system that spans several countries, the clock supplied to each base station uses a terrestrial network, so even if adjacent base stations are on different networks, It is difficult to synchronize the entire system because there are cases where the system is out of synchronization. As a result, it becomes necessary to perform resynchronization when switching channels during a call, resulting in a momentary interruption in the call or forcing unnecessary steps. Furthermore, when a terrestrial network is used, the synchronization signal is transmitted through multiple stages of relaying before being sent to the base station, which tends to cause time differences and errors.

0003

[Problems to be Solved by the Invention] The present invention provides a synchronization method for a mobile communication system using geostationary satellites, which enables synchronization of the entire mobile communication system without changing the ground system synchronization system. This is what we provide.

0004

[Means for Solving the Problems] A terrestrial mobile communication system having a small zone configuration and a geostationary communication satellite are combined to perform system synchronization. A highly stable reference clock source is mounted on a communication satellite, and a signal that serves as a synchronization reference for the system is created on the satellite from that clock and broadcast to a central base station on the ground. Based on this synchronization standard, terrestrial clock synchronization and frame synchronization will be realized. In the case of this synchronization, frame synchronization is corrected in consideration of the difference in propagation delay between the respective central base stations. Each central base station synchronizes the entire system by supplying clocks and synchronization signals to the base stations it controls.

[0005]

Embodiment A synchronization method in a mobile communication system using a geostationary satellite according to the present invention will be explained with reference to the embodiment shown in FIG. In the figure, this system has a basic configuration of a geostationary satellite 100, a satellite line base station 200 serving as the central base station, a mobile communication base station 300, and a mobile station 400. Performs satellite communication and system synchronization. In addition, a mobile communication base station 300, a mobile station 4
00 is the basic configuration of the mobile communication system. This system consists of a highly stable reference clock source 10 on a geostationary satellite 100.
As shown in FIG. 4, the reference burst generated by the reference burst generator 102 using the reference burst generator 102 using the satellite line downlink 108 is transmitted to each satellite line base station 200 on the ground using the satellite line downlink 108. Send by broadcast to.

[0006] An example in which the satellite lines 107 (up link line) and 108 (down link line) are realized by TDMA lines will be explained below. The satellite line base station 200 is
A synchronization signal is detected from the received reference burst, clock synchronization and frame synchronization are performed, and the clock and synchronization information is provided to the mobile communication base station 300. The mobile communication base station 300 performs system synchronization for mobile communication using the clock and synchronization information. Here, a plurality of satellite line base stations 200 can be installed on a satellite, and a plurality of mobile communication base stations 300 may be connected to one satellite line base station 200. .

In the geostationary satellite 100, a highly stable reference clock source 101 generates a highly stable clock required by the system, operates a reference burst generator 102, and creates a frame period and a reference burst. TD satellite line
When used on M line, a frame period and a frame period flag are created. The reference burst generator 102
The reference burst generated at is modulated to an intermediate frequency by a modulator 103, converted to a radio frequency by a transmitter 105,
Uplink link 10 from geostationary satellite receiver 104
It is broadcast from the antenna 106 to the satellite line base station 200 via the down link line 108 along with the data No. 7.

[0008] In the satellite line base station 200, the down link line signal inputted from the satellite line antenna 201 is converted from a radio frequency to an intermediate frequency by a receiver 202.
A demodulator 203 demodulates the baseband signal to obtain demodulated data. The demodulated data is input to a received signal processing device 213 and a synchronization signal detector 212, and the synchronization signal detector 212 detects synchronization signals of the reference burst and other bursts, and outputs the detected synchronization signals to a reception control device 217. The reception control device 217 establishes frame synchronization based on the timing of the detected synchronization signal. Further, the data reproduced by the received signal processing device 213 is connected to the terrestrial network via the terrestrial line interface 216 when it is necessary to connect to the terrestrial line. Furthermore, when communicating data from a terrestrial network via a satellite line, the data from the terrestrial line interface 216 is converted into a format for the satellite line by the transmission signal processing device 214.

[0009] Furthermore, the transmission signal processing device 215 manages the transmission timing and the format conversion, and the format-converted data is modulated to an intermediate frequency by the modulator 205 and converted to a radio frequency by the transmitter 204. It is transmitted from antenna 201 to the satellite via an uplink line.

Furthermore, in the automatic frequency control device 211,
Frequency and phase control is performed using frequency error information such as the carrier and clock from the demodulator 203 and a timing signal from the reception control device 217, and synchronization is performed with the highly stable clock source 101 on the satellite 100. Here, the received signal processing device 213, synchronization signal detector 212, reception control device 217, automatic frequency control device 211, transmission signal processing device 214, and transmission control device 215 are collectively referred to as the satellite line base station line control unit 210. .

On the other hand, the mobile communication base station 300 receives clocks and synchronization signals from the automatic frequency control device 211 and reception control device 217 of the satellite line base station 200 to perform control in synchronization with the satellite line. Mobile communication base station 300
The transmission control device 315 controls the timing of data input from the mobile communication line synchronization signal and the terrestrial line interface 316, and controls the transmission signal processing device 314.
Convert to the mobile communication line format. The modulator 305 converts the format-converted data to an intermediate frequency, and the transmitter 304 converts it to a radio frequency for mobile communication, and transmits the data from the antenna 301 to the mobile station 4.
00 to manage the mobile communication line 401.

Data from the mobile station 400 is converted from a radio frequency to an intermediate frequency by a receiver 302 via an antenna 301, and demodulated into a baseband signal by a demodulator 303. The reception control device 317 uses the synchronization signal detected from the demodulated baseband signal and the transmission control device 31
The received signal processing device 313 and the terrestrial line interface 316 are controlled using the timing signal from 5. The received signal processing device 313 also performs format conversion and outputs the converted signal to the terrestrial line interface 316. Here, the received signal processing device 313, the reception control device 31
7. The transmission signal processing device 314, the transmission control device 315, and the terrestrial line interface 316 are collectively referred to as the mobile communication base station line control unit 310.

[0013] Next, an example of a system in which the TDMA system is adopted for both the satellite line and the terrestrial line in the synchronous connection of the satellite line and the terrestrial line will be described. Figure 2 shows
An example format of a system using the TDMA method is shown. In this format, the TDMA frame of the satellite line and the frame period of the mobile communication line are the same and synchronized. However, the internal structure of one frame may be different. As shown in Fig. 2, one frame of the satellite line consists of a synchronization burst SB and a data burst DB, and one frame of the mobile communication line is divided equally into m slots and divided into m slots. Configure the slots, and the first slot has a synchronous burst SB for mobile line.
Assign. In the satellite line, the frame period is synchronized by detecting the synchronization signal in the synchronization burst, and synchronization over the frame period is established by the frame number. Further, in the mobile communication line, frame period synchronization is performed by detecting the training sequence within the synchronization burst, and synchronization over the frame period is established using frame number information within the control data.

By the way, the reference burst SB transmitted from the satellite is transmitted through the satellite line down link 1 as shown in FIG.
Although the information is broadcast to the satellite line base station 200 at 08, for example, the satellite line base stations A and B have an error in the reception timing due to a propagation delay difference due to the difference in distance from the satellite. Therefore, each of the satellite line base stations A and B performs base station synchronization correction based on the position of the satellite and the position of its own base station. As shown in FIG. 3, the mobile communication base stations belonging to the areas of each satellite link base station A and B calculate and correct the frame synchronization error correction value, transmit the corrected reference burst, and
Frame synchronization of the mobile line is performed based on this corrected reference burst, and the mobile communication down link 401 (Fig. 1
) system synchronization with the mobile station 400 is performed.

[0015] Normally, a terrestrial line is used to communicate control information, data, etc. with other base stations and to connect to a public line network. In addition to the above, the satellite lines 107 and 108
It is also possible to exchange control signals and data signals by communicating between each base station using (FIG. 1). In this case, it is effective in terrain and conditions where connection with a terrestrial line is difficult. Further, it is also possible to establish links and synchronization not only with TDMA lines but also with TDM lines.

[0016]

According to the present invention, synchronization of the entire mobile communication system is possible without changing the terrestrial synchronization system. Since the signals for clock synchronization and frame synchronization are broadcast from the satellite, there is little error in clock synchronization between base stations, and correction for frame synchronization is also necessary because of the propagation delay between base stations via the satellite. It is easy to multiply because the difference can be easily obtained. Furthermore, since satellite lines and terrestrial lines can be used in combination, base stations can be easily installed even in areas where it is difficult to connect terrestrial lines, making it easier to develop the system.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a synchronization method according to the present invention.

FIG. 2 is a diagram showing an example of a frame configuration.

FIG. 3 is an explanatory diagram of frame synchronization error correction.

FIG. 4 is a diagram showing an example of a zone configuration of a satellite line base station.

[Explanation of symbols]

100...Geostationary satellite 101...Highly stable reference clock source 102...Reference burst generator 200...
・Satellite line base station 300...Mobile communication base station 4
00...Mobile station

Claims (1)

[Claims] 1. A highly stable reference clock source mounted on a satellite, means for creating on the satellite a signal that serves as a synchronization reference for a system from the clock of the reference clock source, and a signal that serves as a synchronization reference for the system. a plurality of terrestrial control base stations that establish clock synchronization and frame synchronization of the terrestrial system based on the signal that serves as the synchronization reference, and a small zone to which clocks and synchronization signals are supplied from each of the control base stations. 1. A synchronization method in a mobile communication system using a geostationary satellite, characterized by comprising a mobile communication base station of the configuration.