JPWO2020213047A1 - Wireless communication systems, wireless base stations, control circuits, and storage media - Google Patents

Abstract

In the wireless communication system (1) in which the frame timings are synchronized based on the synchronization message received from the adjacent wireless base stations (10) by each of the plurality of wireless base stations (10), the plurality of wireless base stations (10) The amount of correction for each frame timing is set between the presence or absence of the wireless base station (10) communicating with the wireless terminal, the wireless base station (10) communicating with the wireless terminal, and each wireless base station (10). It is characterized in that it is determined based on the number of radio base stations.

Description

The present invention relates to a radio communication system and a radio base station that synchronize between radio base stations.

The wireless base station that constructs the wireless communication system is a peripheral wireless base station in order to avoid interference between the wireless base stations and to realize a handover that the wireless mobile terminal seamlessly switches the wireless base station to be communicated with. It is necessary to synchronize between them.

For example, not only wireless communication services using the TDMA (Time Division Multiple Access) method, but also wireless communication services such as frequency hopping and CDMA (Code Division Multiple Access) that share time or frequency between wireless base stations or wireless mobile terminals. Then, it is necessary to synchronize the frame timing of transmission between the radio base stations.

Patent Document 1 discloses a technique for reducing the frame timing difference by notifying the frame timing correction information when a large frame timing difference occurs between the radio base stations. If the amount of frame timing correction is large, the service quality may deteriorate, such as communication interruption or handover failure. Therefore, in Patent Document 1, the influence on the service quality is suppressed by executing the correction of the small frame timing in a plurality of times.

Japanese Unexamined Patent Publication No. 2008-160618

However, the technique disclosed in Patent Document 1 has a problem that it may take time for the frame timing to be corrected to the extent that synchronization with an adjacent wireless base station is established, depending on the area status of the wireless terminal. was there.

The present invention has been made in view of the above, and an object of the present invention is to obtain a wireless communication system capable of shortening the time until synchronization is established while suppressing deterioration of service quality.

In a wireless communication system in which frame timings are synchronized based on synchronization messages received from adjacent wireless base stations by each of a plurality of wireless base stations according to the present invention in order to solve the above-mentioned problems and achieve the object. The amount of correction for each frame timing of multiple wireless base stations is determined by the presence or absence of the wireless base station communicating with the wireless terminal, the wireless base station communicating with the wireless terminal, and the wireless base station between the wireless base stations. It is characterized in that it is determined based on the number.

The wireless communication system according to the present invention has an effect that it is possible to shorten the time until synchronization is established while suppressing the deterioration of service quality.

The figure which shows the structure of the wireless communication system which concerns on Embodiment 1 of this invention. The figure which shows the functional structure of the radio base station shown in FIG. The figure which shows the hardware configuration of the radio base station shown in FIG. The figure which shows the detailed functional configuration of the radio base station shown in FIG. The figure which shows the modification of the hardware composition of the wireless base station shown in FIG. The figure for demonstrating an example of the synchronization message sent and received by the radio base station shown in FIG. The figure for demonstrating the scene assumed in the wireless communication system shown in FIG. A flowchart for explaining the operation of the radio base station shown in FIG. A flowchart for explaining the details of step S107 of FIG. The figure which shows the wireless communication system in the state which there is no wireless base station communicating with a wireless terminal. The figure which shows the wireless communication system in the state that the wireless base station communicating with a wireless terminal exists only in the transmission path of one side with respect to the wireless base station of the 2nd region. The figure which shows the wireless communication system in the state which the wireless base station communicating with a wireless terminal exists in the transmission path on both sides with respect to the wireless base station of a 2nd region. The figure which shows an example of the frame timing correction of the wireless communication system shown in FIG.

Hereinafter, the wireless communication system and the wireless base station according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration of a wireless communication system 1 according to a first embodiment of the present invention. The wireless communication system 1 has a plurality of wireless base stations 10-1 to 10-9. Hereinafter, when it is not necessary to distinguish between radio base stations 10-1 to 10-9, it is simply referred to as radio base station 10.

The radio base stations 10-1 to 10-3 are installed in the first region 121. Radio base stations 10-4 to 10-6 are installed in the second area 122. Radio base stations 10-7 to 10-9 are installed in the third area 123. Each radio base station 10 transmits a synchronization message 111 to an adjacent radio base station 10, and synchronizes the frame timing based on the synchronization message 111.

FIG. 2 is a diagram showing a functional configuration of the radio base station 10 shown in FIG. The radio base station 10 includes an antenna unit 201, a radio communication unit 202, a base station control unit 203, a frame timing difference measurement unit 204, a correction amount calculation unit 205, and a communication status determination unit 206.

The antenna unit 201 radiates a radio signal into the air at the time of transmission, and captures the radio signal propagating in the air at the time of reception. The wireless communication unit 202 performs reception processing and transmission processing of wireless signals. The receiving process includes, for example, a demodulation process and a decoding process. The transmission process includes, for example, a transmission data coding process and a modulation process.

The base station control unit 203 is connected to a wireless base station control station provided outside the wireless base station 10 via a wired network, and transmits and controls information input via the wired network, and the received signal is demolished. And output the decrypted information to the wired network. Further, the base station control unit 203 has a function of correcting the transmission and reception frame timings of the radio base station 10 according to the frame timing correction amount notified from the correction amount calculation unit 205.

The frame timing difference measuring unit 204 calculates the difference between the received frame timing of the signal received by the wireless communication unit 202 and its own transmission frame timing, and manages the calculated frame timing for each of the plurality of wireless base stations 10. Further, when a plurality of synchronization messages are received, the frame timing difference measurement unit 204 calculates the frame timing difference between the plurality of synchronization messages. The frame timing difference measuring unit 204 outputs the calculated frame timing difference to the correction amount calculation unit 205.

The correction amount calculation unit 205 calculates the correction amount of the frame timing of the radio base station 10 and the correction amount of the frame timing of the adjacent radio base station 10. Specifically, when the frame timing difference is equal to or greater than a predetermined threshold value, the correction amount calculation unit 205 determines the determination result of the communication status determination unit 206, which will be described later, and the wireless base station 10 and the wireless base station 10 communicating with the wireless terminal. The frame timing correction amount is calculated based on the number of radio base stations between the radio base stations 10. The correction amount calculation unit 205 notifies the base station control unit 203 of the calculated correction amount.

The communication status determination unit 206 determines the presence or absence of the wireless base station 10 communicating with the wireless terminal. Specifically, the communication status determination unit 206 determines the presence or absence of the wireless base station 10 communicating with the wireless terminal based on the communication status information included in the synchronization message. The communication status information indicates the presence or absence of the wireless base station 10 communicating with the wireless terminal and the number of wireless base stations between the wireless terminal and the wireless base station 10 communicating with the wireless terminal on the transmission path of the synchronization message.

FIG. 3 is a diagram showing a hardware configuration of the radio base station 10 shown in FIG. The wireless base station 10 includes an antenna 301, a wireless communication module 302, a CPU (Central Processing Unit) 303, a memory 304, a wired network interface 305, and a power supply 306.

The wireless communication module 302 includes a high-frequency circuit for wireless communication, a modulation / demodulation circuit, and the like. The CPU 303 can realize various functions by reading and executing a computer program stored in the memory 304. The memory 304 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EEPROM (Erasable Programmable ROM), or an EEPROM (registered trademark) (Electrically EPROM). Magnetic discs, flexible discs, optical discs, compact discs, mini discs, DVDs (Digital Versatile Disk), etc.

By reading and executing the program corresponding to the processing of each component stored in the memory 304 by the CPU 303, the base station control unit 203, the frame timing difference measurement unit 204, the correction amount calculation unit 205, and the communication status determination unit The function of 206 is realized. The memory 304 is also used as a temporary memory in each process executed by the CPU 303.

The wired network interface 305 is an interface for connecting to a wired network. The power supply 306 supplies power for driving to each part of the wireless base station 10 such as the wireless communication module 302, the CPU 303, the memory 304, and the wired network interface 305.

FIG. 4 is a diagram showing a detailed functional configuration of the radio base station 10 shown in FIG. The base station control unit 203 includes a frame timing adjustment unit 203a, a correction information message generation unit 203b, and a synchronization message generation unit 203c.

The frame timing difference measurement unit 204 includes a frame timing difference detection unit 204a, a frame timing difference calculation unit 204b, and a frame timing difference storage unit 204c. The correction amount calculation unit 205 includes a correction amount detection unit 205a, a first correction amount calculation unit 205b, and a second correction amount calculation unit 205c. The communication status determination unit 206 includes a communication status detection unit 206a, a communication status storage unit 206b, and a communication status determination unit 206c.

The frame timing detection unit 204a determines the frame timing of the adjacent wireless base stations 10 that need to be synchronized between the adjacent wireless base stations 10 from the synchronization messages such as the synchronization-only control message and the neglected information message received by the wireless communication unit 202. To detect. The frame timing difference calculation unit 204b calculates the frame timing difference between the frame timing of its own station and the frame timing detected by the frame timing detection unit 204a. The frame timing difference storage unit 204c stores the frame timing difference calculated by the frame timing difference calculation unit 204b for each radio base station 10.

The communication status detection unit 206a detects the communication status with the wireless terminal from the synchronization message received by the wireless communication unit 202. Specifically, the synchronization message includes communication status information indicating the presence or absence of the wireless base station 10 communicating with the wireless terminal on the transmission path of the synchronization message, and the communication status detection unit 206a includes the communication status detection unit 206a. Detects the communication status with the wireless terminal based on the communication status information. The communication status storage unit 206b stores the communication status with the wireless terminal detected by the communication status detection unit 206a for each wireless base station 10. The communication status determination unit 206c determines the communication status information to be added to the synchronization message based on the communication status stored in the communication status storage unit 206b. The communication status determination unit 206c notifies the synchronization message generation unit 203c of the determined communication status information.

The correction amount detection unit 205a detects the correction amount of the frame timing transmitted from the adjacent radio base station 10 received by the wireless communication unit 202. The first correction amount calculation unit 205b determines the correction amount detected by the correction amount detection unit 205a, the frame timing difference stored in the frame timing difference storage unit 204c, and the communication status stored in the communication status storage unit 206b. Based on this, the first correction amount, which is the correction amount of the frame timing of the adjacent radio base station 10, is calculated. The second correction amount calculation unit 205c determines the correction amount detected by the correction amount detection unit 205a, the frame timing difference stored in the frame timing difference storage unit 204c, and the communication status stored in the communication status storage unit 206b. Based on this, the second correction amount, which is the correction amount of the frame timing of the own station, is calculated. The correction amount calculation unit 205 notifies the base station control unit 203 of the first correction amount and the second correction amount. Specifically, the first correction amount calculation unit 205b notifies the correction information message generation unit 203b of the first correction amount, and the second correction amount calculation unit 205c adjusts the frame timing of the second correction amount. Notify unit 203a.

The frame timing adjustment unit 203a adjusts the transmission and reception frame timings to the wireless communication unit 202 according to the second correction amount determined by the second correction amount calculation unit 205c. The correction information message generation unit 203b generates a correction information message indicating the correction amount determined by the first correction amount calculation unit 205b, and the generated correction information message is generated by using the wireless communication unit 202 and the antenna unit 201. It transmits to the adjacent radio base station 10, which is the radio base station 10 that needs to be synchronized. The synchronization message generation unit 203c generates a synchronization message including communication status information indicating the communication status determined by the communication status determination unit 206c, and uses the wireless communication unit 202 and the antenna unit 201 to generate the generated synchronization message. , Transmit to the adjacent radio base station 10.

FIG. 5 is a diagram showing a modified example of the hardware configuration of the radio base station 10 shown in FIG. In the configuration shown in FIG. 4, the correction information message generation unit 203b transmits the correction information message to the adjacent radio base station 10 via the radio communication path by using the radio communication unit 202 and the antenna unit 201. Further, in the configuration shown in FIG. 4, the synchronization message generation unit 203c uses the wireless communication unit 202 and the antenna unit 201 to transmit a synchronization message to the adjacent wireless base station 10 via the wireless communication path. .. On the other hand, in the configuration shown in FIG. 5, a correction information message and a synchronization message are transmitted to the adjacent radio base station 10 via the wired network. Since other functional configurations are the same as those of the radio base station 10 shown in FIG. 4, detailed description thereof will be omitted here.

FIG. 6 is a diagram for explaining an example of a synchronization message transmitted / received by the radio base station 10 shown in FIG. Each of the radio base stations 10-1 to 10-5 transmits the synchronization message to the adjacent radio base station 10 in a bucket relay manner while updating the information included in the synchronization message. The information updated by each radio base station 10 is the communication status information and the number of radio base stations between the radio terminal and the radio base station 10 in communication.

In the example of FIG. 6, the radio base station 10-2 is communicating with the radio terminal 20. In this case, the radio base station 10-2 updates the communication status information of the synchronization message 621 received from the radio base station 10-1 to a value indicating that there is a terminal communicating with the radio terminal 20 for synchronization. A synchronization message 622 in which the number of radio base stations between the radio terminal of message 621 and the radio base station 10 in communication is set to "1" is transmitted to the adjacent radio base station 10-3. Since the wireless base station 10-3 is not communicating with the wireless terminal 20, when the synchronization message 622 is received, the communication status information of the synchronization message 622 is maintained, and the wireless base station 10 is communicating with the wireless terminal. The synchronization message 623, which is obtained by incrementing the number of radio base stations in the above and setting the value to "2", is transmitted to the adjacent radio base stations 10-4. Further, when the radio base station 10-4 receives the synchronization message 623, the radio base station 10-4 maintains the communication status information, increments the number of radio base stations between the radio terminal and the radio base station 10 in communication, and sets the value to ". The synchronization message 624 set to "3" is transmitted to the adjacent radio base station 10-5.

By transmitting the synchronization message as described above, each wireless base station can grasp the communication status not only with the adjacent wireless base station 10 but also with the wireless terminal 20. The transmission of the synchronization message may be unicast or broadcast.

FIG. 7 is a diagram for explaining a scene assumed in the wireless communication system 1 shown in FIG. It is assumed that each of the radio base stations 10-1 to 10-9 does not move. Each of the radio base stations 10-1 to 10-9 synchronizes with the adjacent radio base station 10. Information on the radio base station 10 to be synchronized is set in advance in each of the radio base stations 10-1 to 10-9.

The radio base stations 10-1 to 10-3 are installed in the first region 121. Radio base stations 10-4 to 10-6 are installed in the second area 122. Radio base stations 10-7 to 10-9 are installed in the third area 123. The radio base stations 10-1 to 10-3 installed in the first area 121 and the radio base stations 10-7 to 10-9 installed in the third area 123 are in an operating state. The operating state means that the wireless base station 10 is in a state where it can provide a wireless communication service to a wireless terminal. The radio base stations 10-4 to 10-6 installed in the second area 122 are in an operation stopped state. In such a situation, for example, after starting the radio base stations 10-1 to 10-9 of the first region 121, the second region 122, and the third region 123 at the same timing, the second region 122 This can occur when the radio base stations 10-4 to 10-6 of the above are stopped. After starting the radio base stations 10-1 to 10-3 and 10-7 to 10-9 in the first region 121 and the third region 123 first, the radio base stations 10-4 to the second region 122 to A similar situation can occur when 10-6 is started for the first time.

FIG. 8 is a flowchart for explaining the operation of the radio base station 10 shown in FIG. When the radio base station 10 installed in the area 122 is activated, the radio base station 10 searches for a synchronization message of the surrounding radio base stations 10 that have been set (step S101).

The radio base station 10 determines whether or not a desired synchronization message has been received (step S102). If the desired synchronization message cannot be received (step S102: No), the radio base station 10 returns to the process of step S101. When even one desired synchronization message is received (step S102: Yes), the radio base station 10 determines the frame timing of its own station based on the received synchronization message (step S103). The radio base station 10 starts transmitting the synchronization message to the adjacent radio base station 10 and continues the search for the synchronization message (step S104). At this time, the wireless base station 10 updates the communication status information included in the received synchronization message and the number of wireless base stations between the wireless terminal and the wireless base station 10 in communication, and sends the updated synchronization message. Send.

The radio base station 10 determines whether or not all the desired synchronization messages have been received (step S105). If there is a synchronization message that has not been received (step S105: No), the radio base station 10 returns to the process of step S104. When all the synchronization messages have been received (step S105: Yes), the radio base station 10 determines whether or not the frame timing difference between the received plurality of synchronization messages is equal to or greater than the allowable value (step S106). .. For example, when the radio base station 10-5 receives the synchronization message from the radio base stations 10-4 and 10-6, the radio base station 10-5 calculates the frame timing difference between the two synchronization messages. ..

When the frame timing difference is equal to or greater than the permissible value set in advance in the radio base station 10 (step S106: Yes), the radio base station 10 determines the amount of frame timing correction and notifies the adjacent radio base station 10. (Step S107). Details of the calculation of the frame timing correction amount will be described later. The permissible value of the frame timing difference may be determined based on the performance value of the physical layer of wireless communication. The correction amount may be notified by using a dedicated message, by using a beacon, or by using a wired network. When the frame timing difference is less than the permissible value (step S106: No), the radio base station 10 starts operation (step S108).

FIG. 9 is a flowchart for explaining the details of step S107 of FIG. The radio base station 10 determines whether or not all of the communication statuses included in the received plurality of synchronization messages are "none" (step S201).

When all the communication conditions included in the received synchronization message are values indicating that there is no wireless base station 10 communicating with the wireless terminal 20 (step S201: Yes), the wireless base station 10 is calculated. The correction amount is 1/2 of the frame timing difference (step S202).

FIG. 10 is a diagram showing a wireless communication system 1 in a state where there is no wireless base station 10 communicating with the wireless terminal 20. When the communication status information of the synchronization message is a value indicating "none", it indicates that there is no wireless base station 10 communicating with the wireless terminal on the transmission path of the synchronization message. For example, when the radio base station 10-5 receives a synchronization message from each of the adjacent radio base stations 10-4 and 10-6, and the communication status information of the two synchronization messages is a value indicating "none". , As shown in FIG. 10, on the transmission path of the synchronization message via the radio base stations 10-1, 10-2, 10-3, 10-4, and the radio base stations 10-9, 10-8, 10. It indicates that there is no wireless base station 10 communicating with the wireless terminal 20 on the transmission path of the synchronization message via -7 and 10-6. Therefore, no matter which radio base station 10 is made to correct the frame timing, it is unlikely that the communication with the wireless terminal 20 will be affected, and the frame timing is set so that the convergence speed of the frame timing is the shortest. 1/2 of the difference can be used as the correction amount.

Returning to the description of FIG. When all of the communication statuses in the received synchronization message are not "none" (step S201: No), the radio base station 10 determines whether or not the communication status of only one synchronization message is "yes". Determine (step S203). When the communication status of only one of the synchronization messages is "Yes" (step S203: Yes), the radio base station 10 on the transmission path with the wireless terminal communication does not correct the frame timing or corrects the amount. 0 is notified, and the frame timing difference is used as the correction amount for the radio base station 10 on the transmission path on which the wireless communication terminal is not provided (step S204).

FIG. 11 is a diagram showing a wireless communication system 1 in a state in which a wireless base station 10-2 communicating with a wireless terminal 20 exists only in one transmission path with respect to the wireless base station 10 in the second region 122. be. The radio base station 10-5 receives a synchronization message from the radio base stations 10-4 and 10-6. At this time, the communication status information in the synchronization message received from the radio base station 10-4 is a value indicating "Yes", and the communication status information in the synchronization message received from the radio base station 10-6 is "None". Is a value indicating. In this case, if the frame timings of the wireless base stations 10-1, 10-2, 10-3, and 10-4 are corrected, there is a high possibility that the communication with the wireless terminal 20 will be affected, whereas the wireless base station Even if the frame timings of 10-6, 10-7, 10-8, and 10-9 are corrected, it is unlikely that the communication with the wireless terminal 20 will be affected. Therefore, the radio base station 10-5 does not notify the radio base station 10-4 of the frame timing correction amount, or notifies the radio base station 10-6 of the correction amount 0, and the radio base station 10-6 is corrected for the frame timing difference. Notify as.

Returning to the description of FIG. When both of the communication status values of the synchronization message are "Yes" (step S203: No), the radio base station 10 is based on the number of relay radio base stations from the radio base station 10 communicating with the radio terminal 20. The frame timing correction amount is determined (step S205). At this time, the wireless base station 10 increases the correction amount as the distance from the wireless base station 10 communicating with the wireless terminal 20 increases, and decreases the correction amount as the distance is shorter.

FIG. 12 shows a state in which wireless base stations 10-2 and 10-7 communicating with wireless terminals 20-1 and 20-2 exist in transmission paths on both sides of the wireless base station 10 in the second region 122. It is a figure which shows the wireless communication system 1 of. The radio base station 10-5 receives a synchronization message from the radio base stations 10-4 and 10-6. At this time, the communication status information of the synchronization message received from the radio base stations 10-4 and 10-6 is a value indicating "Yes" in both cases. In this case, the radio base station 10-5 is communicating with the radio terminal 20 based on the number of radio base stations between the radio terminal and the radio base station 10 in communication included in the synchronization message. The closer the distance from, the smaller the correction amount. This is because the closer the distance from the wireless base station 10 that is communicating with the wireless terminal 20 is, the higher the possibility that the communication with the wireless terminal 20 will be affected. The number of radio base stations between the radio terminal of the synchronization message received by the radio base station 10-5 from the radio base station 10-4 and the radio base station 10 in communication is "3", and the radio base station 10- The number of radio base stations between the radio terminal of the synchronization message received from the radio base station 10-6 and the radio base station 10 in communication is "2". In this case, the radio base station 10-5 makes the correction amount notified to the radio base station 10-6 smaller than the correction amount notified to the radio base station 10-4.

Subsequently, an example of frame timing correction will be described. Here, the case where the radio base station 10-5 shown in FIG. 10 triggers the frame timing correction will be shown. FIG. 13 is a diagram showing an example of frame timing correction of the wireless communication system 1 shown in FIG. The arrow symbols shown in FIG. 13 indicate the reference time of the frame timing of each radio base station 10. Arrow 1401 indicates the frame timing of the radio base stations 10-1 to 10-4, and arrow 1402 indicates the frame timing of the radio base stations 10-6 to 10-9. If the difference between the arrows of the adjacent radio base stations 10 is less than a certain value, it indicates that the timing synchronization between the radio base stations 10 is established.

When correcting the frame timing, it is not necessary that the frame timings of all the radio base stations 10 match, and the frame timing difference between the radio base stations 10 to be synchronized may be within the allowable value.

First, the radio base station 10-5 sets the frame timing of the radio base station 10-5 to a weighted average value for the arrows 1401 and 1402 in consideration of the communication status with the radio terminal 20. For the weighted average, the number of radio base stations between the radio terminal and the radio base station 10 in communication is used. For example, the frame timing reference values of the arrows 1401 and 1402 are t ₁₄₀₁ and t ₁₄₀₂ , respectively, and the radio base station 10 communicating with the radio terminal notified from the radio base station 10-4 and the radio base station 10-6. _Assuming that the number of radio base stations between is d _{1401 and d 1402} , respectively, the arrow 1403, which is the frame timing reference value of the radio base station 10-5, is t ₁₄₀₃ = (d ₁₄₀₁ × t ₁₄₀₁ + d ₁₄₀₂ × t _1402). ) / (D ₁₄₀₁ + d ₁₄₀₂ ). Then, the correction amounts of the radio base stations 10-4 and 10-6 are determined so that the timing is within the permissible value 1431 of the frame timing difference from the median value. Arrow 1403 indicates the frame timing of the radio base station 10-5 after weighting, arrow 1404 indicates the frame timing of the radio base station 10-4, and arrow 1405 indicates the frame timing of the radio base station 10-6. Shows the frame timing of. As described above, the correction amount 1422 of the radio base station 10-6 is larger than the correction amount 1421 of the radio base station 10-4. The radio base station 10-5 notifies the radio base station 10-4 of the correction amount 1421, and the radio base station 10-6 notifies the radio base station 10-6 of the correction amount 1422.

Subsequently, the radio base station 10-4 calculates the correction amount of the frame timing of the radio base station 10-3. Specifically, the radio base station 10-4 determines the frame timing of the radio base station 10-3 so as to be within the permissible value 1431 of the frame timing difference from the frame timing indicated by the arrow 1404. Arrow 1406 indicates the frame timing of radio base station 10-3. The radio base station 10-4 notifies the radio base station 10-3 of the correction amount 1423.

Further, the radio base station 10-6 calculates the correction amount of the frame timing of the radio base station 10-7. At this time, the frame timing of the radio base station 10-7 is determined so as to be within the permissible value 1431 of the frame timing difference from the frame timing indicated by the arrow 1405. Arrow 1407 indicates the frame timing of the radio base station 10-7. The radio base station 10-6 notifies the radio base station 10-7 of the correction amount 1424.

Subsequently, the radio base station 10-3 calculates the correction amount of the frame timing of the radio base station 10-2. Specifically, the radio base station 10-3 determines the frame timing of the radio base station 10-2 so as to be within the permissible value 1431 of the frame timing difference from the frame timing indicated by the arrow 1406. Arrow 1408 indicates the frame timing of the radio base station 10-2. The radio base station 10-3 notifies the radio base station 10-2 of the correction amount 1425.

Further, the radio base station 10-7 calculates a correction amount of the frame timing of the radio base station 10-8. Specifically, the radio base station 10-7 determines the frame timing of the radio base station 10-8 so as to be within the permissible value 1431 of the frame timing difference from the frame timing indicated by the arrow 1407. Arrow 1409 indicates the frame timing of the radio base station 10-8. The radio base station 10-7 notifies the radio base station 10-8 of the correction amount 1426.

By repeating the same operation in order, the frame timing correction amount is gradually reduced. Since the frame timing difference between the radio base station 10-2 and the radio base station 10-1 is the allowable value 1431 or less, the radio base station 10-2 does not notify the radio base station 10-1 of the correction amount. .. The radio base station 10-2 may notify the radio base station 10-1 that the correction amount is 0.

The radio base station 10-8 calculates the amount of correction for the frame timing of the radio base station 10-9. Specifically, the radio base station 10-8 determines the frame timing of the radio base station 10-9 so as to be within the permissible value 1431 of the frame timing difference from the frame timing indicated by the arrow 1409. Arrow 1410 indicates the frame timing of the radio base station 10-9. The radio base station 10-8 notifies the radio base station 10-9 of the correction amount 1427.

As described above, according to the first embodiment of the present invention, the presence / absence of a wireless base station communicating with the wireless terminal, the wireless base station communicating with the wireless terminal, and the wireless base between the wireless base stations. The amount of frame timing correction is determined based on the number of stations. Therefore, it is possible to shorten the time required to establish synchronization while suppressing the deterioration of service quality.

Further, in the wireless communication system 1, the wireless base station 10-5 that has received the plurality of synchronization messages calculates the frame timing correction amount when the frame timing difference between the plurality of synchronization messages is equal to or greater than the threshold value. , The calculated correction amount is notified to the adjacent radio base stations 10-4 and 10-6, respectively. The radio base station 10-4 notified of the correction amount from the radio base station 10-5 calculates the correction amount of the adjacent radio base station 10-3, and notifies the radio base station 10-3 of the calculated correction amount. do. Similarly, the radio base station 10-6 calculates the correction amount of the adjacent radio base station 10-7, and notifies the radio base station 10-7 of the calculated correction amount. By calculating the correction amount of the adjacent radio base stations 10 in this way, it is possible to sequentially correct the frame timing so that the adjacent radio base stations 10 can be synchronized with each other.

Further, when each of the plurality of wireless base stations 10 included in the wireless communication system 1 is communicating with the wireless terminal 20, between the wireless terminal and the communicating wireless base station 10 included in the synchronization message. The number of wireless base stations is set to zero, and communication status information indicating that communication with the wireless terminal 20 is being performed is added to the synchronization message and transmitted to the adjacent wireless base station 10. Further, each of the plurality of wireless base stations 10 maintains the communication status information of the received synchronization message when not communicating with the wireless terminal 20, and the wireless base station between the wireless terminal and the wireless base station 10 in communication. A synchronization message obtained by incrementing the number is transmitted to the adjacent radio base station 10. As a result, for each transmission path of the synchronization message, communication status information indicating the presence or absence of the wireless base station 10 communicating with the wireless terminal 20 and the number of wireless base stations between the wireless terminal and the wireless base station 10 communicating with the wireless terminal 20 are provided. And can be generated.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 Wireless communication system, 10,10-1 to 10-9 wireless base station, 20,20-1,20-2 wireless terminal, 111,621-624 synchronization message, 121 first area, 122 second area , 123 3rd region, 201 antenna unit, 202 wireless communication unit, 203 base station control unit, 203a frame timing adjustment unit, 203b correction information message generation unit, 203c synchronization message generation unit, 204 frame timing difference measurement unit, 204a Frame timing detection unit, 204b frame timing difference calculation unit, 204c frame timing difference storage unit, 205 correction amount calculation unit, 205a correction amount detection unit, 205b first correction amount calculation unit, 205c second correction amount calculation unit, 206 Communication status determination unit, 206a communication status detection unit, 206b communication status storage unit, 206c communication status determination unit, 301 antenna, 302 wireless communication module, 303 CPU, 304 memory, 305 wired network interface, 306 power supply, 1401-1410 arrows, 1421-1427 Correction amount, 1431 Allowable value.

Claims (7)

In a wireless communication system in which frame timings are synchronized based on synchronization messages received from adjacent wireless base stations by each of a plurality of wireless base stations.
The amount of correction of the frame timing of each of the plurality of radio base stations is determined by the presence or absence of the radio base station communicating with the radio terminal and the radio between the radio base station communicating with the radio terminal and each radio base station. A wireless communication system characterized in that it is determined based on the number of base stations. When the difference in frame timing between the plurality of synchronization messages is equal to or greater than the threshold value, the radio base station that has received the plurality of synchronization messages calculates the frame timing correction amount, and the calculated correction amount is calculated. The wireless communication system according to claim 1, wherein the wireless base station is notified of the above. The synchronization message includes communication status information indicating the presence or absence of a wireless base station communicating with the wireless terminal, and the number of wireless base stations between the wireless terminal and the wireless base station communicating with the wireless terminal. Item 2. The wireless communication system according to Item 1 or 2. Each of the plurality of radio base stations
When communicating with a wireless terminal, the number of wireless base stations between the wireless terminal and the wireless base station being communicated, which is included in the synchronization message, is set to zero to indicate that the communication is being performed with the wireless terminal. The status information is added to the synchronization message and transmitted to the adjacent wireless base station.
When not communicating with the wireless terminal, the communication status information of the received synchronization message is maintained, and the synchronization message obtained by incrementing the number of wireless base stations between the wireless terminal and the wireless base station communicating with the wireless terminal is adjacent. The wireless communication system according to claim 3, wherein the wireless communication system is transmitted to a wireless base station. The radio according to any one of claims 1 to 4, wherein the correction amount is reduced as the number of radio base stations communicating with the radio terminal and the number of radio base stations between the radio base stations is small. Communications system. Any one of claims 1 to 5, wherein each radio base station determines the correction amount of a plurality of adjacent radio base stations based on the synchronization message received from each radio base station. The wireless communication system according to the section. A frame timing difference measuring unit that measures the frame timing difference between multiple synchronization messages received from adjacent radio base stations, and a frame timing difference measuring unit.
A communication status determination unit that determines the presence or absence of a wireless base station that is communicating with a wireless terminal,
Based on the determination result of the communication status determination unit and the number of wireless base stations communicating with the wireless terminal and the number of wireless base stations between the wireless base stations, the correction amount of the frame timing of the adjacent wireless base station is determined. Correction amount calculation unit and
A base station control unit that notifies a plurality of adjacent radio base stations of the determined correction amount, and
A radio base station characterized by being equipped with.

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