JP2970989B2 - Radio frame synchronization method and base station for 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 radio frame synchronization method and a base station for a mobile communication system, for example, a time division multiple access (TDMA) microcell system such as a personal handyphone (PHP) system. Applicable.

[0002]

2. Description of the Related Art There has been a great deal of research and study on a PHP system that enables a portable cordless telephone to be taken out of the home and used as a portable telephone. The handset of a home cordless telephone (hereinafter referred to as a PHP terminal) serving as a mobile terminal in this PHP system has a communication range of about 100 m, which is compared with the communication range (a few km) of a car phone or an existing mobile phone. And pretty narrow. However, the PHP terminal has advantages such as being capable of being used for a long time, being small in size and light in weight, since the transmission output power can be kept low as compared with a car phone or an existing mobile phone.

If the convenience of the PHP system is accepted in the world, those who use the current pager and those who do not have a mobile phone or a pager can also take the cordless telephone handset at home to the outside by taking the PHP. It is expected that the opportunity to use it as a terminal will increase.

[0004] However, since the frequency to be used is a finite resource, it is essential to make the allocated frequency band available effectively.

Since the communication range of a PHP terminal is narrow as described above, base stations must be installed at a high density. As an access method of the PHP system, T
The adoption of the DMA method has been almost decided. In a TDMA microcell system represented by the PHP system, when base stations are densely installed, transmission waves from a plurality of base stations collide with each other or transmission waves from other base stations. And radio waves from the mobile terminal may collide with each other, making it impossible to make a call. By eliminating such waste, effective use of frequency and reduction of the call loss rate can be achieved.

Synchronizing a radio frame at a certain base station (TDMA frame: a frame in a radio section between a base station and a mobile terminal) with a radio frame at a peripheral base station from the viewpoint of effective use of frequency and reduction of a call loss rate. is necessary.

[0007] As a method of synchronizing radio frames in a plurality of base stations, those described in the following documents 1 to 7 have been proposed.

Reference 1 [Shigeki Nitta, Hiroshi Kazama, Shuzo Kato,
"A Study of TDMA Frame Synchronization between Base Stations", 19
1993 IEICE Autumn Conference B-249 ”Reference 2“ Hiroki Morikawa, Masami Yabuzaki, Shinobu Kanashige, “TD between base stations”
Network Synchronization for MA Frame Synchronization ”, 1991 IEICE Spring Conference B-346” Reference 3 Akinori Hiragawa, Hitoshi Takanashi, “Study on TDMA Frame Synchronization between Base Stations in Street Microcells”, 1993 Information and Communication Engineers Autumn Meeting B-24
7 ”Document 4“ Keiji Matsuno, “Autonomous Inter-Base Station Synchronization in TDMA Cellular System”, 1993 IEICE Autumn Meeting B-248 ”Document 5“ Yoshihiko Akaiwa, Hidehiro Ando, Teruhiko Obama, “TDMA Cellular System Autonomous Mutual Synchronization Method between Base Stations ", IEICE Spring Conference 1991, B-34
4 ”Reference 6“ Nobuhiro Nishikawa, Shogo Ito, Toshihiro Nozawa, Mitsuru Murata, “Phase synchronization between stations using a reference clock”, 1993 IEICE Autumn Conference B-250 ”Reference 7“ Takeji Kori, “Mobile TDMA between base stations in communication
Examination of Synchronization Method ", 1991 IEICE Spring Conference B-343" There are roughly three types of wireless frame synchronization methods proposed so far. If the names are given, the network dependent synchronization method (References 1 and 2) and the autonomous synchronization method (References 3 and 4;
5) and a reference clock synchronization method (references 6 and 7). The network dependent synchronization method is a method in which a common synchronization signal is given to each base station from the network side to synchronize radio frames in a plurality of base stations. The autonomous synchronization method is a method of receiving radio waves from an adjacent base station completely independently of a network and directly adjusting the frame phase of air between the base stations. The reference clock synchronization method is a method of synchronizing radio frames in a plurality of base stations by providing a high-precision reference clock in each base station.

[0009]

The present invention relates to a network-dependent synchronization method among these synchronization methods, and aims to supplement the problems of the existing network-dependent synchronization method. Therefore, referring to the conceptual system configuration diagram of FIG.
The existing network dependent synchronization method will be described, and its problems will be described.

In FIG. 2, one or more base stations (C
S) 1a, 1b,..., 1n are the base stations 1a to 1n.
To a centralized control station (CCS) 2 for centralized control of
a, 3b,..., 3n. The central control station 2 includes a reference clock generator 4 and a reference frame generator 5, and the reference clock and the reference frame generated by the reference clock generator 4 and the reference frame generator 5, respectively, are connected to the wired transmission path 3a, , 3n via base stations 1a, 1b,..., 1n. Therefore, the clocks at the base stations 1a, 1b,..., 1n are dependent on the reference clock of the central control station 2, and the radio frames at the base stations 1a, 1b,. Subordinate to.

As described above, the base stations 1a, 1b,.
In the case where n radio frames are made dependent on the reference frame from the central control station (network) 2, conventionally, there is a restriction that the reference frame must be the same as the period of the radio frame or a length that is an integral multiple thereof. there were. If the reference frame is shorter than the period of the wireless frame, as shown in FIG. 3, there are a plurality of reference points that define the wireless frame within one wireless frame period, and the phase becomes indeterminate.

The central control station 2 and the base stations 1a, 1
It is practical to use a periodic signal defined by an interface between b,... 1n as a reference frame. In this case, the period of the reference frame does not always match the period of the radio frame.

Further, the central control station 2 and the base stations 1a, 1
When an existing wired standard interface is used as an interface between b,..., 1n, there is a case where there is no signal serving as a reference of a radio frame in consideration of the above conditions. In this case, a generator for exclusively forming a reference frame (a frame that can be used as it is as a radio frame) is provided, and this reference frame is separated from other signals by each base station 1a, 1b,. As a result, the system configuration becomes complicated and the cost increases.

Further, the central control station 2 and each base station 1a, 1
, 3n are present between the wired transmission paths 3a, 3b,..., 3n, and it is difficult to control the distance between the wired transmission paths 3a, 3b,. Therefore, each wire transmission path 3a,
It is necessary to consider the influence of the propagation delay time due to the distance difference of 3b,..., 3n. For example, assuming that the maximum distance difference is 7 km and the propagation delay time per unit distance is 5 nsec / m, there is a maximum 35 μsec reference frame arrival time difference between base stations. If this time difference does not cause any problem with the synchronization accuracy of the radio frame, the time difference can be left as it is, but if it becomes a problem, as shown in FIG.
Or the base stations 1a, 1b,..., 1n.
When the phase adjustment circuit 6 is installed in the central control station 2, it is necessary to install the phase adjustment circuit 6 for each of the base stations 1a, 1b,..., 1n. In the PHP system, 100
Since the base stations are installed at intervals of about m, the configuration for correcting the propagation delay time becomes considerably complicated.

The above problems occur not only in the micro cell system of the TDMA system typified by the PHP system, but also in the T system as an access system.
In a mobile communication system adopting the DMA system, the same occurs to a different extent.

Therefore, in a mobile communication system adopting the TDMA system, it is desired to ensure radio frame synchronization between adjacent base stations by a simple method for the purpose of effective frequency utilization.

[0017]

In order to solve the above-mentioned problems, according to the present invention, a reference frame is transmitted from a network side to each base station, and each base station operates in synchronization with the reference frame, so that an adjacent base station operates. A radio frame synchronization method for a mobile communication system according to a network dependent synchronization method for synchronizing radio frames between stations is as follows.

That is, for each base station, the phase of the radio frame in the surrounding space is obtained, the phase of the reference frame arriving based on the phase of the radio frame is detected, and the phase is reached according to the detected phase difference. The reference frame is shifted in phase and taken in as a synchronization reference for internal operation.

According to a second aspect of the present invention, in a radio frame synchronization method for a mobile communication system similar to the first aspect of the present invention, a phase of a radio frame of a base station belonging to a zone different from that of the base station is obtained. The base station obtains the phase shift information of the reference frame that has arrived based on the phase of the radio frame, transmits the information to the network side, and the network side determines the phase and / or frequency of the reference frame of the zone to which the transmission base station belongs, The adjustment is made according to the received phase shift.

Further, the third invention relates to a configuration of a base station for realizing the first or second invention, and relates to a radio frame phase detecting means for obtaining a phase of a radio frame in a surrounding space thereof, Phase comparison means for detecting a phase shift of the reference frame reached with reference to the phase, and phase adjustment means for shifting the reached reference frame according to the detected phase shift to be a synchronization reference for internal operation. Become.

[0021]

In any of the present inventions, a network dependent synchronization method for transmitting a reference frame from the network side to each base station, and operating each base station in synchronization with the reference frame to synchronize radio frames between adjacent base stations. And a mobile communication system according to

In this case, it may be difficult to obtain synchronization of the radio frame due to a difference in the distance from the location where the reference frame is generated to the base station, and the base station sets the reference frame according to the distance (transmission delay time). Phase shifting is performed. In this case, it is not always accurate to determine the phase shift amount by estimating the transmission delay time from the distance.

Therefore, in the first embodiment of the present invention, the phase of the received reference frame is shifted based on the phase of the radio frame in the surrounding space, so that the estimation and measurement of the transmission delay time are not required, and the Synchronization was ensured.

According to a second aspect of the present invention, the phase shift information of a received reference frame based on the phase of a radio frame of a base station in another zone is returned to the source of the reference frame to adjust the generated phase. In this way, synchronization of radio frames can be reliably obtained even in a plurality of zones.

The third invention is a configuration of a base station for realizing the first and second inventions.

[0026]

【Example】

(A) First Embodiment Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 conceptually shows a main configuration of a mobile communication system employing the TDMA system according to the first embodiment. Note that the first embodiment is expressed at a more abstract level than the second embodiment described later.

The mobile communication system according to the first embodiment, like the mobile communication system according to the conventional network dependent synchronization method, also has a centralized control station (CCS) 12 and a central control station (CCS) 12 via a wired transmission line 13i. It comprises one or more (generally a plurality) base stations (CS) 11i to be connected.

The central control station 12 includes a reference clock generator 14 for generating a clock (reference clock) serving as a reference for each base station 11i, and a reference frame for generating a frame (reference frame) serving as a reference for each base station 11i. A generator 15 is provided for distribution transmission to each base station 11i. Although the reference clock transmission line and the reference frame transmission line are shown as separate transmission lines in FIG. 1, they may be physically the same transmission line, and may be physically the same as the data transmission line. It may be a line.

Each base station 11i has a shared transmitting / receiving antenna 20, a transmitter (Tx) 21, a receiver (Rx) 22, and a control circuit 23 for communicating with a mobile terminal (PS) 16 within its own communication area. . In the first embodiment, the control circuit 23 activates the transmitter 21 and the receiver 22 in accordance with the timing of a radio frame (TDMA frame), performs time axis conversion of transmission data and reception data, and performs various processing. Is the part that executes. The reference clock from the central control station 12 is input to the control circuit 23, and the reference frame is input to the control circuit 23 via a phase adjustment circuit 30 described later. Also in the first embodiment, a network dependent synchronization method is adopted as a method of synchronizing a radio frame, and the transmitter 21, the receiver 22, and the control circuit 23 operate in accordance with the reference clock and the reference frame. .

The transmitter 21, the receiver 22, and the control circuit 23
Has a processing configuration common to each slot of a radio frame (TDMA frame) and a processing configuration unique to each slot. The processing configuration for at least one slot of the receiver 22 and the control circuit 23 (may be a configuration that functions only in the phase adjustment amount determination mode described later) is different from that of another base station (connected to The centralized control station may be the same as or different from the base station 11i) 11j
It also has the function of receiving radio waves from and performing a perch to catch a perch channel (control channel). Here, the other base station 11j may be connected to the same central control station 12 as the base station 11i, or may be connected to a different central control station.
Generally, the base station 11i captures radio waves from the mobile terminal 16, but in the case of the first embodiment, 1 or 2
Radio waves (control channels) from the above-described peripheral base stations 11j
Has been made to be able to capture. Note that a dedicated receiver for exclusively capturing radio waves (control channels) from the peripheral base station 11j may be provided, or the shared receiver may function as such.

The base station 11i communicates with the mobile terminal 1 as described above.
6 includes a phase adjustment circuit 30, a phase comparison circuit 31, a phase difference detection circuit 32, and a communication function unit 33, in addition to the communication execution configurations 20 to 23 with the P.6.

The phase adjustment circuit 30 shifts the phase of the reference frame from the central control station 12 based on the phase shift command from the phase comparison circuit 31 and inputs the phase to the control circuit 23. The phase adjustment circuit 30 is realized by, for example, a variable delay circuit. As a more specific example, a shift register that performs a shift operation by a reference clock having an output tap at each stage, and a selector that selects one from the tap output of each stage according to a phase shift amount command are provided. Can be mentioned.

The phase comparison circuit 31 is provided with (the phase information of) the reference frame output from the central control station 12, and the receiver 22 receives radio waves from another base station 11j. A wireless frame (phase information) obtained by reproducing the received signal is input. Here, the control circuit 23 may form a radio frame to be given to the phase comparison circuit 31 based on a reception signal obtained by receiving a radio wave from one specific other base station 11j. Alternatively, a radio frame to be provided to the phase comparison circuit 31 may be formed based on a plurality of received signals obtained by receiving radio waves from a plurality of other base stations 11j in the vicinity. In the latter case, for example, the phase information of the radio frame obtained from each received signal is subjected to statistical processing such as weighted averaging to include the average phase information of these radio frames (they are synchronized). A comparison radio frame is formed.

The phase comparison circuit 31 compares the phase of the reference frame and the radio frame, for example, in the phase adjustment amount determination mode, and determines the amount of phase shift in the phase adjustment circuit 30 necessary for synchronizing the reference frame and the radio frame. Then, it is given to the phase adjustment circuit 30 as a phase shift amount command. In the normal operation mode, the phase comparison circuit 31 fixes the phase shift amount command.

The phase difference detection circuit 32 includes a phase comparison circuit 31
(A part of the configuration may be shared.) The absolute value (for example, time information) of the phase difference between the reference frame and the radio frame in the phase adjustment amount determination mode is obtained, and the communication function unit 33 give.

For example, a counter that starts counting by the reference clock at the reference point of the radio frame and ends counting at the reference point of the reference frame can be used as the phase comparison circuit 31 and the phase difference detection circuit 32. Phase adjustment circuit 3
Depending on the configuration of 0, the count value may be decoded and given to the phase adjustment circuit 30 as a phase shift amount command, or the count value may be given to the communication function unit 33 as the absolute amount of the phase difference. good.

The communication function unit 33 converts the absolute amount information of the phase difference between the reference frame and the radio frame given from the phase difference detection circuit 32 immediately after the information is given, or
When requested by the central control station 12 via the control circuit 23, the data is converted into a communication form, transferred to the control circuit 23, and transmitted to the central control station 12.

Next, the operation of the mobile communication system according to the first embodiment having the above configuration will be described.

It is assumed that a new base station 11i is multiplied and installed in the mobile communication system. At this time, the radio frame related to the multiplication base station 11i is transferred to the existing peripheral base station 1
It is necessary to synchronize with the radio frame related to 1j. The installer instructs, for example, the control circuit 23 in the base station 11i to execute the operation of the phase adjustment amount determination mode by an input unit (not shown).

Thus, the control circuit 23 provides the phase comparison circuit 31 with the phase information of the radio frame in the surrounding space formed based on the reception signal of the perch channel from the other base station 11j. In the base station 11i,
At the time of this adjustment, the reference frame is also provided from the central control station 12, so that the base station 11i uses the phase comparison circuit 31 to generate the reference frame from the network with reference to the radio frame phase in the surrounding space. The phase state is detected in the form of a phase difference, and the amount of phase shift with respect to the reference frame by the phase adjustment circuit 30 is adjusted so that the phase difference disappears (more precisely, the phase difference falls within a specified value).

The information on the absolute difference between the phase of the wireless frame in the surrounding space and the phase of the reference frame is obtained from the phase difference detection circuit 32.
To the communication function unit 33 and transmitted to the central control station 12 immediately or when requested by the central control station 12.

When the operation of determining and setting the phase shift amount with respect to the reference frame by the phase adjustment circuit 30 is completed,
Transition to normal operation mode.

In the normal operation mode, the central control station 12
Is shifted by the phase shift amount set as described above by the phase adjustment circuit 30 in the base station 11i, and given to the control circuit 23.
Causes various operations to be executed at a timing based on the reference frame subjected to the phase shift adjustment and the reference clock.
The radio frame related to the base station 11i defined by such an operation is synchronized with the radio frame in the surrounding space. That is, depending on the distance of the transmission path 13i between the central control station 12 and the base station 11i,
Even if the time when the reference frame arrives is different from that of the other base station 11j, the radio frame can be synchronized with the radio frame in the surrounding space.

The network side (the central control station 12 or the like) causes the base station 11i to execute the process of the phase adjustment amount determination mode by a regular or irregular remote instruction using a signal line (not shown). This corrects the phase synchronization of the radio frame.

Therefore, according to the first embodiment, the radio frames of a plurality of base stations are synchronized according to the network-dependent synchronization method, and the radio frames of the central control station (network side) and the respective base stations are different in transmission path distance. Since the difference in the arrival of the reference frame to each base station is corrected based on the phase of the radio frame in the surrounding space, that is, at the time of initial setting, the radio frame is synchronized by a method according to the conventional autonomous synchronization method. In the subsequent normal operation, the radio frames are synchronized according to the network-dependent synchronization method, so that reliable synchronization can be obtained while ensuring that the frequency can be used effectively.

If the autonomous synchronization method is applied without discriminating between the initial setting and the normal operation, each base station must always receive a transmission wave from another base station only for synchronization. In other words, the operation of measuring the effective use of the frequency, that is, the synchronization of the radio frame, impedes the effective use of the frequency, at least partially.

According to the first embodiment, unlike the conventional network dependent synchronization method, there is no restriction that the period of the reference frame must be longer than the period of the radio frame. Even if the reference frame is shorter than the period of the radio frame, there is a problem because the reference point of the reference frame may be matched with the radio frame in the surrounding space as a reference as shown in FIG. Never. That is, since there is no constraint on the period of the reference frame,
The periodic signal of the existing interface can be appropriately applied to the reference frame, and a configuration for exclusively creating the reference frame can be omitted.

Further, according to the first embodiment, even when the operation is started, the frame synchronization state of the wireless section can be monitored by remote control, and the phase adjustment can be executed.

(B) Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. While the first embodiment is an abstract embodiment in which the type of the mobile communication system is not specified, the second embodiment is a more specific implementation in which the mobile communication system is a PHP system. It is an example. FIG. 5 shows the system configuration of the second embodiment, in which the same or corresponding parts as in FIG. 1 according to the first embodiment are denoted by the same reference numerals.

In the case of the PHP system, the centralized control station 12 and the base station 11i are typically connected by an I interface (an interface of an international standard specification).

The frame generator 15 in this embodiment
Is based on the clock from clock generator 14,
A layer 1 frame having one channel bit, B2 channel bit, D channel bit and the like is generated. Therefore,
The reference clock component supplied from the central control station 12 to the base station 11i is 192 kHz, and the reference frame (framing bit) is 8 kHz (125 μsec).

In the base station 11i, a timing extracting circuit 24 is provided.
Reference numeral 4 extracts a clock signal from the transmission signal of the AMI code given from the central control station 12 and reproduces a frame signal.

In the base station 11i, the 192 kHz clock component is extracted by being multiplied by 384 kHz and used as a clock signal in the base station 11i.

On the other hand, the 8 kHz reference frame signal extracted and reproduced by the timing extraction circuit 24 is
The phase is adjusted by the phase adjustment circuit 30 and supplied to the control circuit 23. The control circuit 23, the transmitter 21, the receiver 22 and the like in the base station 11i include the phase adjustment circuit 3
It operates based on the phase of the frame output from 0. The reference point information of the extracted and reproduced reference frame signal is provided to the phase comparison circuit 31.

The receiver 22 of the second embodiment, like the receiver of the first embodiment, transmits waves (control channels: SCCH, BCCH, PCCH, etc.) from another base station 11j.
H) via the air to perform a perch (frame synchronization). This function is called the pseudo PS function because the base station 11i has the same function as the mobile terminal 16. When the base station 11i is installed, one or more receivers 22 execute the pseudo PS function. When the control channel is received, since information on which slot the control channel is transmitting is included in the control channel, the control circuit 23 recognizes the head of the 5-ms radio frame from the information. The reference point information of the radio frame is input to the phase comparison circuit 31. The phase comparison circuit 31 measures the phase difference between the reference point of the radio frame and the reference point of the reference frame from the central control station 12, inputs a difference signal to the phase adjustment circuit 30, and determines that the difference is within the allowable range. The phase of the reproduced reference frame is adjusted to fall within the range. The adjustment work is completed when the phase is within the tolerance,
The control circuit 23 returns the receiver 22 in the pseudo PS mode to the normal mode, and the base station 11i operates according to the reference frame from the central control station 12.

For example, a code for remote start of phase adjustment is defined, and the communication function unit 33 determines that information from the central control station 12 is a code for remote start of phase adjustment addressed to the base station 11i. When the control circuit 2 recognizes
3 to start the phase adjustment operation of the reference frame.

Further, in the phase adjustment operation when the base station 11i is installed and the phase adjustment is remotely started, the absolute amount of the phase difference obtained by the phase difference detection circuit 32 is transmitted to the network side (the central control station 12). You.

As described above, in the second embodiment, the present invention
Although applied to the P system, its characteristic configuration is
This is the same as the first embodiment, and the same effects as those of the first embodiment can be obtained.

(C) Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment mainly includes a central control station 12-
A and 12-B have characteristics.

In FIG. 6, base stations 11-A2 to 11-A5 connected to central control station 12-A and base stations 11-B2 to 11-B connected to central control station 12-B.
From a state where the area with B5 does not overlap, in other words, zones A and B of the central control stations 12-A and 12-B.
It is assumed that the base station 11-A1 capable of capturing a transmission wave from another zone B is added to the central control station 12-A from the state where there is no overlap, and the phase adjustment at the time of installation is performed. Here, the base station 11-A1 transmits the absolute amount of the phase difference output from the phase difference detection circuit 32-A1 when capturing the transmission wave from another zone B to the central control station 12-A.

In the central control station 12-A, the communication function unit 40-A having received the phase difference signal transmits all the base stations 11-A1 to 11-A on the output side of the frame generator 15-A.
5 outputs a phase shift command corresponding to the received phase difference signal to the phase adjustment circuit 41-A interposed at a common position.

Thus, the reference frame output from the phase adjusting circuit 41-A matches the phases of the radio frames of both zones A and B.

As described above, the case where the phase of the reference frame output from the central control station 12-A is adjusted when the base station 11-A1 is additionally installed has been described. Is also good.

Therefore, according to the third embodiment, if at least some of the zones overlap, radio frames from base stations connected to different centralized control stations can be synchronized.

(D) Other Embodiments The present invention is particularly effective in a microcell system having a small base station area, but is also applicable to a mobile communication system in which each base station has a larger area. Similarly, there is an effect that synchronization of radio frames can be obtained with high accuracy.

In the present invention, the access method is TDMA
The present invention can be applied to any transmission method, and the type of transmission method is not limited to the time division two-way transmission method (TDD method).

In the above-described embodiment, the transmission of the absolute amount of the phase difference with respect to the radio frame to the central control station has been described. May be transmitted so that the central control station 12 can detect the frequency of the reference frame. In such a case, for example, as a modification of the third embodiment, a central control station may change not only the phase of the reference frame but also the frequency and distribute the reference frame to each base station.

Further, in the above embodiment, the detection of the phase difference and the like are performed automatically. However, the detection of the phase difference and the like may be performed manually.

[0069]

As described above, according to the present invention, the phase state of a reference frame arriving at a base station is grasped based on the phase of a radio frame in the surrounding space, and the reference frame is fetched internally. Since the phase adjustment is performed, the radio frames can be more reliably synchronized than in the related art.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of a mobile communication system according to a first embodiment.

FIG. 2 is an explanatory diagram of a conventional network dependent synchronization method.

FIG. 3 is an explanatory view of a conventional disadvantage.

FIG. 4 is an explanatory diagram showing that the defect according to FIG. 3 does not exist in the first embodiment.

FIG. 5 is a block diagram illustrating a main configuration of a mobile communication system according to a second embodiment;

FIG. 6 is a block diagram illustrating a main configuration of a mobile communication system according to a third embodiment;

[Explanation of symbols]

11i, 11j: base station, 12: central control station, 14: reference clock generator, 15: reference frame generator, 16 ...
Mobile terminal, 20: shared antenna for transmission / reception, 21: transmitter, 2
2 ... receiver, 23 ... control circuit, 30 ... phase adjustment circuit, 3
1: phase comparison circuit, 32: phase difference detection circuit, 33: communication function unit.

Claims (4)

(57) [Claims] A mobile communication according to a network dependent synchronization method in which a reference frame is transmitted from a network to each base station, and each base station operates in synchronization with the reference frame to synchronize radio frames between adjacent base stations. In the system radio frame synchronization method, for each base station, the phase of the radio frame in the surrounding space is obtained, the phase of the reference frame arriving based on the phase of the radio frame is detected, and the phase is detected according to the detected phase difference. The phase of the reference frame that has arrived is taken in as a synchronization reference for internal operation. 2. A mobile communication system according to a network dependent synchronization method in which a reference frame is transmitted from a network side to each base station, and each base station operates in synchronization with the reference frame to synchronize radio frames between adjacent base stations. In the system radio frame synchronization method, a base station that has obtained the phase of a radio frame of a base station belonging to a zone different from its own base station obtains phase shift information of the reference frame that has arrived based on the phase of the radio frame. Transmitting to the network side, and the network side adjusts the phase and / or frequency of the reference frame of the zone to which the transmission base station belongs in accordance with the received phase shift. . 3. The radio frame of a mobile communication system according to claim 1, wherein the base station operates the mobile terminal by simulating a built-in receiver, and obtains a phase of the radio frame. Synchronization method. 4. A mobile communication system according to a network dependent synchronization method in which a reference frame is transmitted from a network to each base station, and each base station operates in synchronization with the reference frame to synchronize radio frames between adjacent base stations. A base station of the system, a radio frame phase detecting means for obtaining a phase of a radio frame in the surrounding space; a phase comparing means for detecting a phase shift of the reference frame arriving with reference to the phase of the radio frame; A base station for a mobile communication system, comprising: a phase adjusting unit that shifts the phase of the reference frame that has arrived in accordance with the phase shift that has been made, and uses the phase as a synchronization reference for internal operation.