JPH11285060A - Method for detecting out of synchronism of radio frame in mobil radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect a deviation from synchronism of a radio frame in a short time. SOLUTION: A CPU 18 reads a slot number and a channel number from a nonvolatile memory 19 when a synchronism deviation is detected and checks whether or not a UW detector 14 receives a UW(unique word) in the slot, and discriminates whether or not a deviation from its own station timing is within a tolerance based on phase shift information received from synchronism deviation detector 17 when the UW detector detects the UW. When the deviation is out of the tolerance, the CPU 18 discriminates occurrence of synchronism deviation and advances to re-synchronization processing. On the other hand, when within the tolerance, the CPU 18 discriminates it is in synchronism and terminates the synchronism deviation detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA (Time Division Multiple Acceleration) requiring radio synchronization between base stations.
The present invention relates to a ESS) -TDD (Time Division Duplex) mobile radio communication system, and more particularly to a radio synchronization loss detection method for a mobile radio communication system for automatically performing radio frame resynchronization between base stations during system operation.

[0002]

2. Description of the Related Art PHS (Personal Handyphone System)
Is based on an autonomous decentralized system and does not require radio frame synchronization. However, in reality, the base stations are installed in a relatively dense state due to an increase in the number of base stations and an increase in spots for measures against blind spots, so that radio interference occurs.

For this reason, it is necessary to reduce interference by performing radio frame synchronization. Also, wireless frame synchronization is indispensable for effective use of wireless resources.

[0004] Examples of the conventional inter-base station synchronization method are disclosed in Japanese Patent Application Laid-Open Nos. 8-280059 and 8-280061.
According to the contents, when a UW (unique word) received from a peripheral mobile station or a peripheral base station is received in a head slot and a tail slot of a transmission frame in the same frame, The transmission and reception frames of the base station can be detected.

As another example, a received signal from a partner base station to be synchronized (or a dedicated frame synchronization signal transmitting base station) is analyzed to determine an absolute slot number, and a head of a frame is calculated based on the information. Then, there is a method of performing radio frame synchronization.

[0006]

However, the above-mentioned conventional system has the following problems. During operation of the system, it is necessary to periodically detect out-of-synchronization of the radio frame in order to ensure synchronization accuracy. However, Japanese Patent Application Laid-Open Nos. 8-280059 and 8-2
According to the system disclosed in Japanese Patent No. 80061, when a UW (unique word) received from a peripheral mobile station or a peripheral base station is received in the first slot and the last slot of a transmission frame in the same frame, a transmission / reception frame of the base station can be detected. Therefore, at the time of the out-of-synchronization detection operation, the above condition must be satisfied, and it cannot be said that the detection can be reliably performed.

Further, in both of the above-mentioned prior arts, it is necessary to set the reception state in all the slots, and it is inevitable that the system operation is stopped during that time. However, in order to ensure the synchronization accuracy, when the synchronization operation is performed unconditionally without detecting the out-of-synchronization, in a PHS having a large number of base stations and a possibility that the base station arrangement may change daily,
Since there is a high possibility that the system will not be converged and become unstable, and the system operation may be stopped, detection of the loss of synchronization is indispensable.

[0008] The present invention has been made in view of the above-mentioned circumstances, and is provided with a slot position of a reference signal (such as a control channel) transmitted from a counterpart base station (or a dedicated frame synchronization signal transmission base station) synchronized in advance. Is stored, and the reception operation is periodically performed only for the slot, so that U
An object of the present invention is to provide a method for detecting radio synchronization loss in a mobile radio communication system that can easily detect radio frame synchronization loss in a short time by detecting W (unique word).

[0009]

According to the first aspect of the present invention, there is provided a mobile radio communication system including at least a radio base station requiring radio frame synchronization between base stations. Receiving a unique word at the position of the partner slot used when synchronization was completed last time and the channel number at that time, and generating a frame timing according to the slot head timing of the received unique word. And comparing the phase of the frame timing of the own station and the phase of the generated frame timing,
If the result of the comparison indicates that the mutual phase difference is out of the allowable range, determining that the synchronization has been lost.

[0010] According to the second aspect of the present invention, in the first aspect,
In the method for detecting out-of-synchronization of a mobile radio communication system described above, the series of steps are automatically operated at a preset time.

According to the present invention, the radio base station has a nonvolatile memory for storing the slot position and the channel number used as a reference at the time of the previous synchronization, and the radio base station can always determine the frame timing at any slot position in the past. We can know whether it was decided. Therefore, it is possible to determine whether or not the current frame timing and the reference frame timing are shifted only by periodically performing the UW (unique word) reception operation only at the stored slot position. Further, in this case, since the receiving operation only needs to be performed at a specific slot position, it is possible to automatically realize the operation without stopping the operation of the system. Therefore, in a mobile radio communication system that requires radio frame synchronization, the detection of radio frame out-of-synchronization can be easily performed without stopping the system operation, and the resynchronization operation can be performed only for the minimum necessary number of base stations. Wireless frame synchronization accuracy can be ensured.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. A. Configuration of Embodiment FIG. 1 is a block diagram showing a PHS communication system according to an embodiment of the present invention. In the figure, a mobile terminal station 1 and base station apparatuses 2a to 2c are respectively connected by wireless lines. Each of the base station apparatuses 2a to 2c is connected to the exchange 3 by a digital wired line. Here, FIG. 4 is a conceptual diagram showing a normal slot usage method. The base station transmission slot is composed of four slots A to D. Slot A is a control channel for transmission, and slots B to D are mobile stations PS1, PS2, respectively.
Used for the communication channel with PS3. The base station reception slot is composed of four slots A ′ to D ′, where slot A ′ is a control channel for reception and slots B ′ to
D 'is used as a communication channel with the mobile units PS1, PS2, and PS3, respectively. In this system, the base station device 2a
2c is synchronized with a reference signal transmitted from the reference base station 4 and realized. However,
The reference base station 4 may be replaced with any of the base station devices 2a to 2c.

Next, FIG. 2 is a block diagram showing the internal configuration of the base station device for explaining the operation of the base station devices 2a to 2c. In FIG. 2, an antenna 10 is used for transmitting and receiving radio waves. The RF switch 11 is appropriately switched during transmission and reception, is connected to a transmission system during transmission, and is connected to a receiver during reception.
5 is controlled. The receiver 12 amplifies the signal received by the antenna 10, performs a filtering process, and supplies the signal to the demodulator 13. The demodulator 13 demodulates the signal received and amplified by the receiver 12, converts the demodulated signal into a digital signal, and supplies the digital signal to a UW (unique word) detector 14. The UW detector 14 detects a UW (unique word) from the received data, generates a slot head timing,
It is supplied to the wireless control unit 15 and the frame head position detector 16. The wireless control unit 15 is on the wireless side (transmitting system, receiving system)
Is performed, and data is exchanged with a wired control unit 21 described later.

Next, the UW (unique word) detection signal changeover switch SW1 is normally in the OFF state, and is controlled to the ON state by the wireless control unit 15 only when performing the out-of-synchronization detection operation. Frame head position detector 16
Generates a frame timing from the slot head timing received from the UW detector 14 and supplies the frame timing to the out-of-synchronization detector 17. The out-of-synchronization detector 17 detects a phase shift between the frame timing of the own station received from the wireless control unit 15 and the frame received from the frame head position detector 16 and supplies the same to the CPU 18.

The CPU 18 controls the entire base station. In particular, the CPU 18 starts an out-of-synchronization detection operation at a time set in advance by a program (or a parameter that can be arbitrarily changed), instructs each unit of an opportunity to perform the out-of-synchronization detection, and outputs the out-of-synchronization detector 1
7, it is determined whether or not the phase shift obtained by comparing the frame timing of the own station with the frame timing supplied from the frame head position detector 16 is within an allowable range. The out-of-synchronization detection operation will be described later.

The non-volatile memory 19 stores in which slot position the signal transmitted from the reference base station synchronized in advance is, and what the channel number is. The non-volatile memory 19 previously stores the slot position of the partner and the channel number received when receiving from the reference base station when the base station is activated or when resynchronization is completed. The transmission system 20 modulates and amplifies the transmission data supplied from the wireless control unit 15,
Send from. The wired system control unit 21 controls the wired side and exchanges data with the wireless control unit 15. The DSU 22 terminates a physical interface with the exchange 3.

B. Next, the operation of this embodiment will be described in detail. FIG.
Is a flowchart for explaining a basic operation.
First, during normal operation, the retry counter t is set to 0 in step S1. The retry counter t is U
This is the number of repetitions of the out-of-synchronization detection operation when W cannot be detected. Next, in step S2, it is periodically checked whether the resynchronization execution time has arrived. Here, when it is detected that the resynchronization execution time has arrived, the process proceeds to step S3 to start the out-of-synchronization detection operation. In step S3, the CPU 18 reads the slot number and the channel number from the nonvolatile memory 19. Thereafter, the process proceeds to step S4, and notifies the wireless control unit 15 and the wired line control unit 21 that an out-of-synchronization detection operation is to be performed.

Next, in step S5, it is checked whether UW has been received in the corresponding slot. Here, FIG. 5 shows an example of the use state of the slot when the out-of-synchronization is detected. In FIG. 5, synchronization is detected at the position of slot B of the base station transmission slot. Then, the UW detector 14
If (unique word) cannot be detected, the process proceeds to step S6, where it is determined whether t = s, that is, whether the retry counter t has reached a preset allowable number of retries s, If not, step S
In step 7, the retry counter t is incremented by "1", and the process returns to step S4. Thereafter, the reception operation retry in the corresponding slot is repeated up to the preset allowable number of retries s. This is for the purpose of relieving in consideration of the case where reception becomes impossible for a moment due to the influence of fading or the like. If retry-out has occurred, it is determined that synchronization has been lost, the process proceeds to step S10, and the process proceeds to resynchronization processing.

On the other hand, if the UW detector 14 can detect the UW within the allowable number of retries s, the process proceeds to step S8, where the CPU 18 determines the timing of its own station based on the phase shift information received from the out-of-sync detector 17. Is determined to be within the allowable range. At this time, if it is out of the allowable range, it is determined that synchronization has been lost, and step S10 is performed.
The process proceeds to resynchronization processing. Here, FIG. 6 shows a timing chart when the out-of-synchronization occurs. If it is within the allowable range, it is determined that synchronization is not lost, and the process proceeds to step S9. Here, FIG. 7 shows a timing chart when no out-of-synchronization occurs. In step S9, the wireless controller 15 and the wired line controller 21 are notified that the out-of-synchronization detection operation has been completed,
After resetting the retry counter t, the process returns to step S1, and the above-described steps S1 to S10 are continued as a basic operation.

Further details will be described below. In the above-described step S4, when the CPU 18 recognizes the time at which the out-of-synchronization is to be detected, the CPU 18 reads out the position of the partner slot used when the previous synchronization was completed and the channel number at that time from the non-volatile memory 19, and reads out only the relevant slot. Radio control unit 1 so that the receiving operation can be performed with the set channel number.
5 and the wired control unit 21 are notified. Therefore, when the corresponding slot timing comes, the wireless control unit 15 turns on the UW detection signal changeover switch SW1 and gives the slot head timing to the frame head position detector 16. Thereafter, the frame head position detector 16 generates a frame timing according to the slot head timing received from the UW detector 14 and supplies the timing to the out-of-synchronization detector 17.

At the same time, the out-of-synchronization detector 17 receives the frame timing of the own station from the radio control unit 15, and the frame timing of the own station and the frame head position detector 1
The phase is compared with the frame timing supplied from step 6. The phase shift is transferred to the CPU 18 and it is determined whether or not the phase shift is within an allowable range. That is, if the phase shift is equal to or larger than the allowable value, it is determined that a synchronization loss has occurred, and resynchronization processing is performed.

As described above, in the above-described embodiment, the slot position synchronized last time is stored, and the receiving operation is performed only in the corresponding slot. Is possible.
In this embodiment, since the resynchronization execution time is set automatically in advance, the resynchronization is performed automatically, so that the wireless frame synchronization state can be always maintained. Furthermore, since the out-of-synchronization detection time can be set arbitrarily, if time is required depending on the resynchronization method, it can be set to be performed at midnight with low traffic (for example, around AM 3:00 to AM 5:00). It is.

[0023]

As described above, according to the present invention,
The following effects can be obtained. (1) Since the slot position of the partner synchronized in the past is stored, the receiving operation is performed only in the corresponding slot and the UW is detected, so that the wireless synchronization loss detection can be performed while the communication call is continued. The advantage that it can be obtained is obtained. (2) The resynchronization process is not performed in all the base stations unconditionally, and the resynchronization process can be performed only in the necessary base station by detecting the radio synchronization loss according to the present invention. The advantage is obtained that the operation stop can be prevented from occurring. (3) When detecting out-of-synchronization, the presence or absence of out-of-synchronization can be determined only by detecting the UW in the partner slot, so that the scale of software and hardware can be reduced, and the advantage of reducing the cost of the base station can be obtained. . (4) Since the start timing of the out-of-synchronization detection operation can be automatically set by setting the start time in each base station, the operation can be automatically performed even in a PHS having a relatively large number of base stations. The advantage that the above load can be reduced is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a system configuration in a PHS.

FIG. 2 is a block diagram illustrating a configuration of a PHS base station device.

FIG. 3 is a flowchart for explaining an out-of-synchronization detection algorithm;

FIG. 4 is a conceptual diagram showing an example of a normal slot usage method.

FIG. 5 is a conceptual diagram showing an example of synchronous detection at the position of a B slot.

FIG. 6 is a timing chart showing an example of a case where no synchronization shift has occurred.

FIG. 7 is a timing chart showing an example of a case where a synchronization shift has occurred.

[Explanation of symbols]

 Reference Signs List 1 mobile station 2a to 2c base station 3 exchange 4 reference base station 10 antenna 11 switch 12 receiver 13 demodulator 14 UW detector 16 frame header detector 17 synchronization shift detector 15 wireless control unit SW1 changeover switch 18 CPU 19 nonvolatile Memory 20 Transmission system 21 Wired control unit 22 DSU

Claims (2)

[Claims] 1. A method for detecting a radio synchronization loss of a mobile radio communication system comprising at least a radio base station requiring radio frame synchronization between base stations, comprising the steps of: Receiving a unique word with the channel number at that time; generating a frame timing according to the slot start timing of the received unique word; and comparing the phase of the frame timing of the own station with the generated frame timing And determining if the phase difference is out of an allowable range as a result of the comparison, that the synchronization is out of synchronization. 2. The method according to claim 1, wherein the series of steps automatically operate at a preset time.