JP5923761B2 - Base station apparatus and communication system - Google Patents

Description

  The present invention relates to a base station apparatus and a communication system.

  In a conventional communication system (for example, PBX (Private Branch eXchange) wireless system), a communication terminal sequentially switches base stations to be communicated among a plurality of base station apparatuses (hereinafter also simply referred to as “base stations”). Can move. Such switching of base stations is called handover. In order for the communication terminal to suitably perform handover, it is necessary for a plurality of base stations to synchronize time information with each other.

  The following methods are known as a method of synchronizing a plurality of base stations. A time information server transmits time information to a plurality of base stations via a LAN (Local Area Network). And each base station adjusts the clock generator in an own apparatus based on the reception time of time information, and time information (for example, refer patent document 1).

  Similarly, the following method is also known. The mobile station has a plurality of base stations, and the mobile station selectively connects a line with one or more base stations and communicates at a predetermined timing. Among the base stations, a base station that generates transmission timing and reception timing is set as a reference station at a higher level in the hierarchy. The base stations other than the reference station select a higher-tier base station and set transmission timing and reception timing. The base station corrects the difference between the transmission timing and the reception timing with the synchronization partner base station at a predetermined time interval (see, for example, Patent Document 2).

  Similarly, the following method is also known. The synchronization server transmits, as an IP packet, a synchronization message including information related to a periodically generated clock to each base station. Each base station receives a synchronization message from the synchronization server. Each base station calculates a clock correction value based on the time when the synchronization message is received and the information related to the clock notified by the synchronization message, and corrects the clock in each base station based on the clock correction value (for example, And Patent Document 3).

Japanese translation of PCT publication No. 2003-509973 JP 2002-165269 A JP 2004-186877 A

  Each base station receives a synchronization signal periodically in order to synchronize with other base stations during normal times. On the other hand, when each base station loses sight of the synchronization signal, the synchronization with other base stations shifts. As a result, each base station may not be able to synchronize with other base stations with accuracy other than restarting.

  In the technique of Patent Document 1, when the clock function of the time information server is stopped, a plurality of base stations cannot synchronize with each other with high accuracy. In the technique of Patent Document 2, when the timing generation function of the reference station is stopped, a plurality of base stations cannot be synchronized with each other with high accuracy. In the technique of Patent Document 3, when the function of the synchronization server stops, a plurality of base stations cannot synchronize with each other with high accuracy.

  The present invention has been made in view of the above circumstances, and provides a base station apparatus and a communication system in which a plurality of base stations can synchronize with high accuracy even when a predetermined synchronization signal is not received. For the purpose.

  The base station apparatus of the present invention is a base station apparatus that communicates with another base station apparatus by a time division method, a wireless communication unit that communicates with another communication apparatus via a wireless network, and a communication signal by the wireless communication unit A communication timing determination unit that determines a communication timing, a communication timing correction unit that corrects the communication timing determined by the communication timing determination unit, and a synchronization signal from another base station device that is a master are received at a predetermined reception timing. And a storage unit that stores base station apparatus candidates that can become a determination request destination of the synchronization state together with priority order information, and the priority order stored in the storage unit is the same layer as the base station apparatus. The priority is given to other base station devices in a higher hierarchy than the base station device, and the communication timing correction unit adds the priority order information to the priority order information. When the synchronization state response signal is received from the other base station device in response to the synchronization state confirmation signal transmitted to the other base station device determined based on the synchronization state response signal, the communication timing is corrected based on the synchronization state response signal. .

  According to this configuration, even when there is a base station apparatus that cannot determine the synchronization state, a more accurate determination result of the synchronization state can be acquired.

  According to the present invention, even when a predetermined synchronization signal is not received, a plurality of base stations can be synchronized with high accuracy.

The block diagram which shows the structural example of the communication system in embodiment of this invention. The block diagram which shows the structural example of the base station apparatus in embodiment of this invention The figure which shows the example of the time division system in the radio | wireless communication in embodiment of this invention The figure which shows an example of the transmission / reception timing of the synchronous signal in the normal state of the base station apparatus in embodiment of this invention The figure which shows the example of correction | amendment of the communication timing in the normal state of the base station apparatus in embodiment of this invention The figure which shows an example of the transmission / reception timing of the synchronous signal in the losing state of the base station apparatus in embodiment of this invention The figure for demonstrating an example of the determination process of the synchronous state in embodiment of this invention The figure for demonstrating an example of the determination process of the synchronous state in embodiment of this invention The figure for demonstrating an example of the determination process of the synchronous state in embodiment of this invention The flowchart which shows the operation example in the normal state of the base station apparatus in embodiment of this invention The figure which shows the example of correction | amendment of the communication timing which the base station apparatus in embodiment of this invention used the correction parameter. The flowchart which shows the operation example in the losing state of the base station apparatus in embodiment of this invention The flowchart which shows the operation example in the case of determining the synchronous state of the base station apparatus in embodiment of this invention The figure which shows the example of correction | amendment of communication timing and a correction parameter by the base station apparatus in embodiment of this invention by a correction parameter and network correction | amendment The figure which shows an example of the hierarchical structure of the some base station apparatus in embodiment of this invention The figure which shows an example of the transmission / reception timing of the synchronous signal in the losing state of the base station apparatus in embodiment of this invention, and the reception timing of the synchronous signal of a communication terminal

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a configuration example of a communication system 1000 according to the first embodiment of the present invention. The communication system 1000 includes a base station apparatus (CS: Cell Station) 100, a communication terminal (PS: Personal Station) 200, a SIP (Session Initiation Protocol) server 300, a telephone 400, and a router 500.

  A plurality of CSs 100 exist hierarchically in the communication system 1000. In FIG. 1, a plurality of CSs 100 are referred to as CS100M, CS100M1, and CS100M2. In FIG. 1, the CS 100M is arranged in the highest hierarchy, and is, for example, a device (Timing Master CS) serving as a reference for synchronization. The CS 100M1 and the CS 100M2 are devices (Slave CS) that are arranged in the lower hierarchy of the CS 100M and operate according to the synchronization standard of the CS 100M. CS100M1 and CS100M2 may also be arranged hierarchically. For example, the CS 100M1 is arranged in a higher hierarchy than the CS 100M2.

  PS 200 is a mobile communication terminal that operates as a slave unit and is movable. The PS 200 is, for example, a mobile phone, a personal digital assistant (PDA), or a portable sensor device. The PS 200 acquires location information using, for example, the GPS function of the PS 200, and performs handover with the CS 100 based on the acquired location information.

  The SIP server 300 uses the SIP protocol, for example, associates a telephone number with an IP address, and executes a call control process for calling and connecting a communication partner.

  The telephone 400 is, for example, an extension telephone, and communicates with another telephone device (for example, PS 200) via the SIP server 300, for example.

  The router 500 connects the communication system 1000 and the external network 600 and relays data in the communication system 1000 and data in the external network 600. Further, the router 500, the CS 100, the PS 200, the SIP server 300, and the telephone set 400 are connected via a wired network (for example, an IP network).

Next, a configuration example of the CS 100 will be described.
FIG. 2 is a block diagram illustrating a configuration example of the CS 100.

  The CS 100 includes a wireless communication unit 101, an antenna unit 102, a wired communication unit 103, a wireless communication determination unit 104, a clock generation unit 105, a communication timing determination unit 106, a communication timing correction unit 107, a synchronization state determination unit 108, and a storage unit 109. The learning processing unit 110 is provided.

  The wireless communication unit 101 communicates with other communication devices via the antenna unit 102 and the wireless network. The wireless network is a wireless communication network based on, for example, DECT (Digital Enhanced Cordless Communication).

  The wired communication unit 103 communicates with other communication devices via a wired network. The wired network is, for example, a wired LAN, a wired WAN, or a power line.

  Hereinafter, a case where CS 100 transmits and receives a synchronization state confirmation signal and a synchronization state response signal using wired communication unit 103 will be described. For example, when the wireless communication unit 101 does not receive the synchronization signal from the master CS at a predetermined timing, the wired communication unit 103 is used to check the synchronization state with another CS via the wired network. Send a synchronization status confirmation signal. In other CSs, the synchronization status confirmation signal transmitted via the wired network from the CS that cannot receive the synchronization signal is received using the wired communication unit 103.

  When another CS uses the wired communication unit 103 to transmit a synchronization state response signal that is a response to the synchronization state confirmation signal via the wired network, the CS wired communication unit 103 that has transmitted the above-described synchronization state confirmation signal The synchronization state response signal is received. That is, other CSs requested to be confirmed by the synchronization state confirmation signal determine the synchronization state by the synchronization state determination unit 108 and use the wired communication unit 103 to determine the synchronization state response signal including the determination result as the synchronization state determination. It transmits to other CS which is a request source. The synchronization state response signal includes the determination result of the synchronization state.

  The wireless communication determination unit 104 determines whether the wireless communication unit 101 has normally received the synchronization signal from the master CS. That is, the wireless communication determination unit 104 determines whether the wireless communication unit 101 has not lost the synchronization signal and has received the synchronization signal at a predetermined reception timing. Examples of cases where the synchronization signal is lost include when the power of another CS that transmits the synchronization signal to the CS is off, or when radio wave interference occurs at the reception timing of the synchronization signal.

  The clock generation unit 105 operates each unit in the CS 100 and generates a reference clock for determining the communication timing of the wireless communication unit 101.

  The communication timing determination unit 106 determines the communication timing of the communication signal by the wireless communication unit 101 based on the reference clock of the clock generation unit 105. The communication signal includes a synchronization signal for synchronizing with another CS 100.

  The communication timing correction unit 107 corrects the communication timing for the wireless communication unit 101 to communicate based on, for example, a synchronization signal acquired from another CS 100 via a wired network. The communication timing includes at least one of transmission timing and reception timing by the wireless communication unit 101.

  The radio synchronization of a certain CS 100 may be synchronized, for example, according to a synchronization signal from another CS 100 arranged in a higher hierarchy. For example, the CS 100M1 is synchronized according to a synchronization signal from the CS 100M that is the master of the CS 100M1, and the CS 100M2 is synchronized according to a synchronization signal from the CS 100M or CS 100M1 that is the master. Therefore, the communication timing correction unit 107 of each CS corrects the communication timing in accordance with the synchronization signal from the CS arranged in the upper hierarchy. When correcting the communication timing, the reference clock of CS 100 may be corrected by a clock correction unit (not shown).

  In addition, when a synchronization state determination unit 108 of a certain CS is requested to determine the synchronization state by the above-described synchronization state confirmation signal from another CS, the synchronization signal of the other CS (determination request source) is determined in a predetermined slot. Try to receive. When the synchronization signal can be received, the synchronization state determination unit 108 measures the difference between the time position of the synchronization signal and the time position of the reception slot of the synchronization state determination unit 108 and the other CS (determination request source) and the own CS ( Whether the synchronization with the determination request destination CS) is good or bad is determined. Details of this determination processing will be described later. The synchronization state determination unit 108 transmits the determination result of the synchronization state to the wired communication unit 103, and the wired communication unit 103 transmits a synchronization state response signal including the determination result to another CS that is the determination request source of the synchronization state.

  The storage unit 109 is configured by, for example, a ROM (Read Only Memory) or a RAM (Random Access Memory), and stores various types of information. For example, the storage unit 109 stores a CS candidate list together with priority order information as CS candidates that can be a determination request destination of the synchronization state.

  The storage unit 109 stores information on at least one of transmission channels and slots of synchronization signals of other CSs in the network, or information on scheduled reception timing. The information on the transmission channel and transmission slot of the synchronization signal is an example of information on the time position where the synchronization signal is transmitted. In addition, the storage unit 109 stores, for example, information on time lag or correction parameter information obtained by learning processing.

  The learning processing unit 110 determines the correction parameter for correcting the communication timing according to the learning result while sequentially learning the time lag between the own CS and the other CS in the asynchronous state. Therefore, the learning processing unit 110 has a function as a correction parameter determination unit. This correction parameter is used in a state of being lost.

  The wireless communication determination unit 104, the communication timing determination unit 106, the communication timing correction unit 107, the synchronization state determination unit 108, and the learning processing unit 110 realize each function by executing a program stored in the storage unit 109. To do.

Next, a configuration example of the PS 200 will be described.
The PS 200 includes, for example, a RAM, a ROM, and a CPU, and has functions similar to some of the functions of the CS 100. For example, the PS 200 has the same functions as the radio communication unit 101 and the synchronization state determination unit 108 of the CS 100.

Next, a configuration example of a communication frame in wireless communication will be described.
In wireless communication in the communication system 1000, for example, as shown in FIG. 3, a time division method is used in which communication is performed with 10 msec as one frame and one frame divided into 24 slots. The time-division communication includes, for example, TDMA / TDD (Time Dimension Multiple Access / Time Division Duplex) communication.

  In the example shown in FIG. 3, a time length obtained by dividing one frame (10 msec) into 24 is defined as one slot, and each communication device is assigned any slot each time communication is started. connect.

  The synchronization signal is also called a beacon signal and includes synchronization data (for example, Syncword). Syncword is a predetermined numeric string for timing synchronization, and is data of a known pattern determined in advance, which is synchronization information for synchronizing the above-described telephone device (PS200) and other slave CSs. In the DECT system, a unique Syncword is assigned to each network, and the Syncword is commonly included in signals transmitted from terminals belonging to one network.

Next, synchronization processing in the normal state of the CS 100 will be described.
FIG. 4 is a diagram illustrating an example of the transmission / reception timing of the synchronization signal in the normal state of the CS 100. FIG. 5 is a diagram illustrating an example of correcting the communication timing in the normal state of the CS 100.

  The normal state is a state in which a synchronization signal is periodically received from a predetermined CS 100 and synchronization is possible based on the synchronization signal. 4 and 5 exemplify synchronization processing among CS 100M, CS 100M1, and CS 100M2. CS100M operates as a synchronization master of CS100M1, and CS100M1 operates as a synchronization master of CS100M2.

  As shown in FIG. 4, the CS 100M transmits a synchronization signal (Dummy) at a certain interval (for example, slot 0 of the communication signal 30) (Dummy TX).

  As shown in FIG. 4, the slave CS 100M1 receives the synchronization signal from the master CS 100M (RX) and operates in synchronization with the communication timing of the CS 100M. Further, the CS 100M1 transmits its own synchronization signal at a certain interval (for example, slot 7 of the communication signal 30) (Dummy TX).

  The CS 100M2 receives the synchronization signal from the CS 100M1 (RX) and operates in synchronization with the communication timing of the CS 100M1. The CS 100M2 transmits its own synchronization signal at a constant interval (for example, the slot 15 of the communication signal 30) (TX).

  As shown in FIG. 5, when a time lag occurs between the CS 100M and the CS 100M, the CS 100M1 detects the time position of the Syncword included in the synchronization signal, and immediately determines the communication timing using the detection result. to correct. FIG. 5 illustrates a case where the communication timing of the CS 100M1 is delayed from a predetermined timing.

  In addition, when a time lag occurs between CS 100M2 and CS 100M1, CS 100M2 corrects the communication timing using the information on the time lag included in the synchronization signal. FIG. 5 illustrates a case where the communication timing of CS100M2 is advanced from a predetermined timing.

  Note that the CS 100M1 and the CS 100M2 determine a correction parameter at the time of non-synchronization according to the acquired information on the time lag and hold it in the storage unit 109.

  According to the synchronization process in the normal state, the communication timing in each CS 100 can be maintained at a predetermined timing, and synchronization can be maintained.

Next, the synchronization process in the state where CS 100 is lost is described.
FIG. 6 is a diagram illustrating an example of the transmission / reception timing of the synchronization signal when the CS 100 is lost.

  The CS 100M transmits a synchronization signal at a constant interval, for example, in slot 0 of the frame n (TX). After transmitting the synchronization signal in slot 0 of frame n, next, the synchronization signal is transmitted in slot 0 of frame n + 1 after 10 msec, and the synchronization signal is transmitted in slot 0 every 10 msec thereafter.

  The slave CS100M1 receives the synchronization signal from the CS100M (RX), and operates in synchronization with the communication timing of the CS100M. The CS 100M1 also transmits its own synchronization signal, for example, in the slot 7 at regular intervals (every 10 msec) (TX). In a normal environment, the slave CS100M2 also receives the synchronization signal from the CS100M1, and operates in synchronization with the communication timing of the CS100M1.

  In FIG. 6, the CS 100M2 cannot receive the synchronization signal for some reason and is in a state of being lost. The CS 100M2 waits for a synchronization signal from the CS 100M1 until a predetermined time elapses from a predetermined timing, but cannot receive the synchronization signal. In this case, CS 100M2 does not stop the operation even if it cannot receive the synchronization signal, and corrects the communication timing as appropriate using the correction parameter obtained by the normal learning, and maintains the communication timing with CS 100M1.

  As described above, the CS 100M2 transmits its own synchronization signal at a certain interval (for example, slot 15 of the communication signal 30) without receiving the synchronization signal from the CS 100M1 (Dummy TX). The CS 100M1 that is the master and the CS 100M that is the higher-level master may be able to receive the synchronization signal of the CS 100M2.

  In addition, when the state in which the synchronization signal from the CS 100M1 is not received continues for a while (a predetermined time or longer), the CS 100M2 transmits a synchronization state confirmation signal for requesting the determination of the synchronization state via the wired network. The CS 100M1 or CS 100M that has received the synchronization state confirmation signal via the wired network performs determination processing by the synchronization state determination unit 108, and the synchronization state response signal including the determination result (temporal deviation information) is the determination request source. Transmit to CS100M2. When the CS100M2 acquires the information on the time lag included in the synchronization state response signal via the wired network, the CS 100M2 corrects the communication timing using the acquired information on the time lag. As described above, the CS 100M2 periodically transmits the synchronization state confirmation signal while the synchronization signal cannot be received, and corrects the communication timing using the information on the time difference received via the wired network.

  The CS 100M2 operates while correcting the communication timing using the information on the time lag by periodically transmitting / receiving the synchronization status confirmation signal / synchronization status response signal via the wired network, and in parallel from the CS 100M1 by the wireless network. Try to receive the sync signal. When the CS 100M2 receives the synchronization signal by the wireless network, the CS 100M2 returns from the lost state to the normal state. When returning to the normal state, the CS 100M2 stops transmission / reception of the synchronization state confirmation signal / synchronization state response signal. Thus, by trying to automatically receive the synchronization signal while attempting to receive the synchronization signal, it is possible to prevent the network load of the wired network from increasing unnecessarily.

  When the CS 100 loses sight of the synchronization signal of the upper CS 100, the CS 100 does not immediately transmit a synchronization status confirmation signal, but tries to receive the synchronization signal from the CS 100M1 through the wireless network for a while (predetermined period). You may do it. The self-running operation refers to an operation in an asynchronous state that is not synchronized with another CS 100. For example, when CS100M1 loses sight of the synchronization signal of the upper CS, it moves to a self-running operation, and during the self-running operation, it tries to correct the communication timing based on the correction parameter accumulated in the storage unit 109 and maintain the communication timing. .

Next, the synchronization state (timing deviation) determination process will be described.
7 to 9 are diagrams for explaining the synchronization state determination processing. 7 to 9 exemplify that the CS 100M1 is a synchronization master of the CS 100M2, and the CS 100M2 may be in a normal state or in a lost state. 7 to 9, the wireless communication unit 101 of the CS 100M2 transmits using the assigned slot.

  The communication signal 30 transmitted by the CS 100M2 includes, for example, “Syncword”, “ID data”, and “voice data”. “ID data” indicates identification information of the transmission source of the communication signal 30. Note that “ID data” may be omitted. When “ID data” is included in the communication signal 30, the synchronization state determination request source can be reliably identified. When “ID data” is included in the communication signal 30, the synchronization state is determined after the ID check is performed, so that a difference occurs in the determination time of the synchronization state, and the influence of jamming radio waves can be reduced. Also, CS 100M1 may determine the synchronization state only when “ID data” included in the synchronization signal of CS 100M2 is valid.

  CS 100M1 sets reception window W1 for synchronization state determination unit 108 to receive “Syncword” of the synchronization signal from CS 100M2. The reception window W1 sets “Syncword” as a time interval of ± 2 bits of the scheduled reception timing. The ± 2 bits are an example, and the time interval may be longer or shorter. Note that the reception window W1 shown in FIGS. 7 to 9 is an example of a reception scheduled timing of a synchronization signal (for example, synchronization information).

  The scheduled reception timing can be predicted based on slot information in which the CS 100M2 is scheduled to transmit a synchronization signal. That is, the CS 100M1 performs a receiving operation in accordance with a synchronization signal that is known in advance in accordance with a slot scheduled to be transmitted, and detects a time lag (before and after) between the reception window W1 and “Syncword” that is actually received. The CS 100M1 may store the transmission channel and slot information of the synchronization signal of the CS 100M2 or the information on the scheduled reception timing in the storage unit 109 in advance.

  As shown in FIG. 7, when the Syncword reception timing is substantially at the center of the reception window W1, the synchronization state determination unit 108 of the CS 100M1 determines that the CS 100M1 and the CS 100M2 are synchronized and that there is no time lag.

  As shown in FIG. 8, when the Syncword reception timing is behind the center of the reception window W1, the CS100M1 synchronization state determination unit 108 determines that the CS100M2 communication timing is later than the CS100M1.

  As shown in FIG. 9, when the Syncword reception timing is temporally ahead of the center of the reception window W1, the synchronization state determination unit 108 of the CS 100M1 determines that the communication timing of the CS 100M2 is earlier than the CS 100M1.

  In this way, the synchronization state determination unit 108 may determine the synchronization state based on the difference between the reception timing of the synchronization information included in the synchronization signal and the scheduled reception timing of the synchronization information. As a result, the synchronization state can be determined with high accuracy.

  When the synchronization state determination request source is CS100M2, CS100 for determining the synchronization state may be CS100M, for example.

Next, an operation example of the CS 100 in a normal state will be described.
FIG. 10 is a flowchart illustrating an operation example of the CS 100 in the normal state.
The CS 100 performs the learning process in the normal state, and maintains the communication timing using the result of the learning process when the sight is lost. FIG. 10 illustrates that the slave CS 100M2 synchronizes using the synchronization signal from the master CS 100M1.

  First, the wireless communication determination unit 104 determines whether or not the wireless communication unit 101 has received a synchronization signal from the CS 100M1 at a predetermined timing (step S101). The predetermined timing is a timing at which a synchronization signal is scheduled to be received from CS 100M1.

  When the synchronization signal is not received at a predetermined timing, the CS 100M2 ends the process of FIG.

  Subsequently, the learning processing unit 110 refers to the timer and determines whether it is the learning timing for the CS 100 to learn (step S102). If it is not the learning timing, the communication timing correction unit 107 corrects the communication timing based on the synchronization signal received by the wireless communication unit 101 (step S103). For example, it is predetermined to learn 10 seconds every minute. In the process of FIG. 10, a timer (for example, RTC (Real Time Clock)) (not shown) of the CS 100 measures time.

  On the other hand, if the synchronization signal is received at a predetermined timing and the time is the learning timing (step S102: Yes), the process proceeds to step S104 as it is.

  At the learning timing, the communication timing correction unit 107 temporarily interrupts the correction after correcting the communication timing once, for example (step S104). That is, CS100M2 intentionally generates an asynchronous state (self-running state).

  Subsequently, the learning processing unit 110 measures a time lag with respect to the CS 100M1 (step S105). For example, the learning processing unit 110 measures a time lag between the reception timing of the synchronization signal from the CS 100M1 and the scheduled reception timing of the synchronization signal from the CS 100M1.

  The measured time lag information includes the direction of the time lag of the communication timing of the CS 100M2 with respect to the CS 100M1 and the degree of time lag (value of time lag). The direction of deviation indicates whether the communication timing of CS100M2 is advanced (-) or delayed (+) with respect to the communication timing of CS100M1. The value of the time difference indicates the magnitude of the communication timing difference between the CS 100M1 and the CS 100M2, and is indicated by, for example, the number of bits or time. Therefore, the information on the time lag may be represented as +1 bit or −1 bit.

  Note that the detection accuracy of the time lag is, for example, 1/12 (bit). One bit is, for example, 868 nanoseconds. The time lag value may be information on a specific number of seconds.

  Subsequently, the learning processing unit 110 stores the measured time lag information in the storage unit 109 (step S106).

  Subsequently, the learning processing unit 110 refers to the timer and determines whether or not the learning timing has ended (step S107). For example, the learning processing unit 110 determines whether 10 seconds have elapsed since the start of the learning timing. If the learning timing has not ended, the process returns to step S105.

  On the other hand, when the learning timing ends, the learning processing unit 110 determines the correction parameter for the communication timing in the self-running state based on the information on the time lag stored in the storage unit 109 at the learning timing. The correction parameter is, for example, −1 bit when the time lag information is +1 bit, and +1 bit when the information is −1 bit.

  FIG. 11 illustrates an example in which the CS 100M2 corrects the communication timing using the correction parameter by the communication timing correction unit 107. FIG. 11 shows that a time lag occurs by +1 bit per 5 seconds in the free-running state. In this case, the correction parameter is −1 bit (−1 bit / 5 sec) per 5 seconds.

  Thus, CS100M2 can correct | amend communication timing according to the tendency of the time gap of CS100 in a self-running state by determining a correction parameter by learning by the learning process part 110. FIG. Therefore, the CS 100 can stably maintain the communication timing even if the CS 100 is lost.

  FIG. 12 is a flowchart showing an example of the operation of the CS 100M1 in a lost state. FIG. 13 is a flowchart illustrating an operation example of the CS 100M that determines the synchronization state. Next, based on the flowcharts of FIGS. 12 and 13, an example of the operation of the CS 100 in the lost state will be described. Here, CS100M1 is CS100M1 in the state of losing sight, and CS100M that receives the synchronization state determination request from CS100M1 and determines the synchronization state with CS100M1 is CS100M. 12 and 13, the timer (not shown) of the CS 100 (for example, RTC (Real Time Clock)) measures time.

  In the example shown in FIGS. 12 and 13, the CS 100M1 loses sight of the synchronization signal from the CS 100M, and inquires of the CS 100M about the time difference of the CS 100M1 via the wired network. The CS 100M that has received the inquiry receives the synchronization signal of the inquiry source CS 100M1, acquires information on the time lag, and notifies the CS 100M1 of the time lag information. The CS 100M1 corrects the communication timing based on the notified information on the time difference. In the losing state, the CS 100M1 corrects the communication timing with the correction parameter determined by the learning process.

  Hereinafter, FIG. 12 will be described in detail. First, the wireless communication determination unit 104 of the CS 100M1 determines whether the CS 100M1 is in a state of being lost (step S201). For example, the wireless communication determination unit 104 determines whether or not a synchronization signal from the CS 100M has been received for a certain period or longer. If the CS 100M1 is not lost, the process ends without performing the following processing.

  When the CS 100M1 is in a state of being lost, as described above, the wired communication unit 103 transmits a synchronization state confirmation signal for requesting the determination of the synchronization state via the wired network.

  At that time, the synchronization state confirmation signal is transmitted including information on the channel (CH) and slot (SL) for transmitting the synchronization signal of CS100M1, and scanning is requested by the CH and SL (step S202). Another CS (for example, CS100M) that has received the synchronization status confirmation signal via the wired network receives the synchronization signal of the CS100M1 that is the determination request source, performs a determination process, and includes a synchronization state response signal that includes information on a time lag. Is transmitted to CS 100M1 via a wired network. Note that the channel and slot information for transmitting the synchronization signal of CS100M1 as the determination request source may be transmitted by being included in the synchronization status confirmation signal or may be transmitted by being included in another communication signal.

  Subsequently, the wired communication unit 103 of the CS 100M1 receives a synchronization state response signal sent back from another CS (for example, the CS 100M), and thereby acquires time lag information (step S203). The information on the time shift includes the direction of the time shift of the CS 100M1 with respect to the CS 100M and the value of the time shift. Further, the synchronization status response signal sent back from the CS 100M as the determination request destination also includes information on the channel and slot through which the CS 100M transmits the synchronization signal, and the wired communication unit 103 of the CS 100M1 transmits the CS 100M via the wired network. The information of the transmission channel and slot of the synchronization signal of CS100M sent from is received.

  Subsequently, the communication timing correction unit 107 corrects the communication timing based on the information on the time lag from the CS 100M (step S204). Note that the processing in steps S202 to S205 corresponds to network correction.

  Subsequently, the communication timing correction unit 107 corrects (adjusts) the correction parameter stored in the storage unit 109 based on the information on the time lag from the CS 100M (step S205).

  Subsequently, the communication timing correction unit 107 checks whether or not it matches the transmission channel and slot to be synchronized based on the received CS100M synchronization signal transmission channel and slot information, and synchronization is established. It is confirmed whether or not the transmission slot and channel are correct (step S206).

  Subsequently, as a result of checking the information on the transmission channel and slot to be synchronized, the communication timing correction unit 107 determines whether or not the information on the transmission channel and slot to be synchronized should be changed (step S207). Information on the transmission channel and slot through which the CS to be synchronized transmits a synchronization signal is stored in the storage unit 109. For example, if it should synchronize with the synchronization signal of CS100M, the communication timing correction unit 107 determines that the transmission channel and slot information of the acquired synchronization signal is different from the transmission channel and slot information stored in the storage unit 109. Determines to change the transmission channel and slot to be synchronized. Further, the communication timing correction unit 107 determines that the transmission channel and slot of the acquired synchronization signal are not changed when the information of the transmission channel and slot stored in the storage unit 109 is the same.

  If it is determined to change the transmission channel and slot information, the communication timing correction unit 107 switches the transmission channel and slot to be synchronized (step S208). The communication timing correction unit 107 stores the switched transmission channel and slot information in the storage unit 109.

  In addition, according to the process of FIG. 12, the determination of the correction parameter in the learning process can be corrected. The accuracy of the correction parameter in the learning process may be insufficient. A correction parameter with high accuracy can be obtained by correcting the correction parameter in the learning process based on the information on the time lag from the CS 100M.

Next, a description will be given based on FIG.
The wired communication unit 103 of the determination request destination CS (for example, CS100M) receives the synchronization state confirmation signal from the determination request source CS100M1 in the losing state (step S301). Further, the wired communication unit 103 of the CS 100M as the determination request destination receives the transmission channel and slot information of the synchronization signal of the CS 100M1 from the CS 100M1 (step S302). The transmission channel and slot information of the CS100M1 synchronization signal may be transmitted by being included in the synchronization state confirmation signal, or may be transmitted by being included in another communication signal. Further, when the transmission unit and slot information of the CS100M1 synchronization signal is stored in the storage unit 109 in advance, this transmission / reception may be omitted.

  Subsequently, the synchronization status determination unit 108 of the CS 100M that is the determination request destination scans the synchronization signal emitted from the CS 100M1 that is the determination request source by the wireless communication unit 101, and acquires information on the channel and slot that included the synchronization signal ( Step S303).

  Subsequently, the synchronization status determination unit 108 of the determination request destination CS 100M scans a synchronization signal issued by the determination request source CS 100M 1 based on the channel and slot information received by the wired communication unit 103. The synchronization state determination unit 108 determines the synchronization state between the CS 100M and the CS 100M1 by measuring a time lag between the reception timing of the synchronization signal received by the scan and the scheduled reception timing of the synchronization signal from the CS 100M1. . For example, the synchronization state determination unit 108 determines the synchronization state based on the temporal difference between the reception timing of the synchronization signal that can be received from the CS 100M1 and the scheduled reception timing. Based on the determination of the synchronization state, the synchronization state determination unit 108 acquires information on the time lag of the CS 100M1 with respect to the CS 100M (step S304).

  Subsequently, the wired communication unit 103 of the CS that is the determination request destination includes the information on the time lag acquired by the synchronization state determination unit 108 in the synchronization state response signal and transmits it to the CS 100M1 via the wired network (step S305). ). Further, the wired communication unit 103 of the CS 100M as the determination request destination also transmits the synchronization channel transmission channel and slot information transmitted by its own CS 100M to the CS 100M1 in the synchronization state response signal (step S306).

  As described above, according to the processing of FIG. 13, the CS 100M as the determination request destination responds to the synchronization state determination request from the request source CS 100M1 via the wired network. Information can be notified. Although the reliability of the wireless network is low because the CS 100M1 is in a state of being lost, it is possible to reliably notify the information on the time lag by using the wired network.

  FIG. 14 shows an example in which the CS 100M1 as the determination request source corrects the communication timing by the correction parameter and the network correction and corrects the correction parameter when a time lag occurs in the CS 100M1.

  In the example of FIG. 14, the correction parameter determined by the learning process in the normal state is −1 bit (−1 bit / 5 sec) per 5 seconds. While the network correction is not performed, the correction parameter is only corrected by -1 bit per 5 seconds, and the time shift gradually increases.

  Assuming that the initial time point without time lag is 0 seconds, network correction is performed every 15 seconds in the example of FIG. When the information on the time lag from CS100M is acquired by network correction, it is notified to correct -3 bits to remove +3 bits at the time of 15 seconds, but the correction parameters determined by the learning process described above Is -1 bit per 5 seconds, the communication timing correction unit 107 adds both correction values, and corrects -4 bits at the time of 15 seconds. Further, at the time of 15 seconds, the communication timing correction unit 107 corrects, for example, the correction parameter to −1 bit (−1 bit / 4 sec) per 4 seconds. By such correction parameter change, the width of the time shift is reduced.

  At the next 30 seconds, CS 100M is notified by network correction to remove -2 bits to remove +2 bits. Also in this case, since the correction parameter determined by the above-described learning process is −1 bit per 5 seconds, the communication timing correction unit 107 adds both the correction values and corrects −3 bits at 30 seconds. Is done. At the same time, the communication timing correction unit 107 corrects the correction parameter to −1 bit (−1 bit / 3 sec) per 3 seconds, for example. As a result, the time lag is almost 0 every 3 seconds, and the network correction (NW correction) is 0 bits even at 45 seconds.

  In this way, whether or not the correction parameter determined by the learning process is an appropriate parameter is determined based on the time lag between the synchronization signal scan of the determination request destination CS 100M and the reception timing of the received synchronization signal and the scheduled reception timing. It can be evaluated by measuring. Since the evaluation result (time shift information) by the CS 100M is notified to the determination request source CS 100M1, the CS 100M1 can improve the communication timing and the correction parameter.

Next, the priority order of the synchronization state determination request destination will be described.
FIG. 15 is a diagram illustrating an example of a hierarchical structure of a plurality of CSs in the communication system 1000. In FIG. 15, it is assumed that CS2 among a plurality of CSs (CS0 to CS10) is lost.

  In a normal state, CS2 synchronizes using a synchronization signal from CS1 arranged in a layer one level higher.

  When CS2 loses sight of the synchronization signal from CS1, CS2 requests CS100 in a higher hierarchy than CS2 to determine the synchronization state. Accordingly, the CS2 synchronization state determination request destination is any one of CS0, CS1, and CS4. Since CS 100 in the lower hierarchy than CS 2 is basically a device that synchronizes based on the synchronization signal of CS 2, the priority as a synchronization state determination request destination is low.

  In addition, CS2 may request the CS100 in the same hierarchy as CS2 to determine the synchronization state. As a result, the number of choices of the synchronization state determination request destination increases, and the possibility that time shift information can be increased.

  Also, in CS2, the storage unit 109 may hold in advance the priority order information of the synchronization state determination request destination as a CS candidate list. In this case, the wired communication unit 103 determines the transmission destination of the synchronization status confirmation signal based on the CS candidate list.

  For example, the priority of the request for determination of the synchronization state by CS2 is CS1-> CS4-> CS5-> CS6-> CS3. The priority of CS3 is low. If the CS1 synchronization signal with the highest priority is lost, for example, the power supply of CS1 may be off or the radio environment may be inferior. This is because there is a high possibility that it cannot be confirmed. By using the priority order information, the synchronization state can be confirmed in the order intended in advance.

  Further, when the synchronization status response signal is not obtained even if CS2 requests the determination of the synchronization status up to the CS of the predetermined order, CS2 has not yet requested the determination of the synchronization status among the CSs included in the CS candidate list. A synchronization state determination request may be broadcasted to other CSs. Thereby, CS100 which can determine a synchronous state can be discovered at an early stage, and a communication timing can be maintained at an early stage.

Next, it will be described that the CS 100 requests the PS 200 to determine the synchronization state.
FIG. 16 is a diagram illustrating the transmission / reception timing of the synchronization signal and the reception timing of the synchronization signal of the PS 200 when the CS 100M2 is lost.

  For example, the CS 100M2 may request the determination of the synchronization state via the PS 200 when the synchronization state confirmation signal from the CS 100M1 cannot be confirmed by wired communication in the lost state. This increases the possibility that the synchronization state can be determined.

  First, the wireless communication unit 101 of the CS 100M2 requests the PS 200 to determine the synchronization state. That is, CS 100M2 transmits a synchronization state confirmation signal for confirming the synchronization state to PS 200. For example, the synchronization state determination request includes information on at least one of the transmission channel and slot of the synchronization signal of CS100M2, and information on at least one of the transmission channel and slot of the synchronization signal of CS100M1 as the synchronization master. Information on at least one of the transmission channel and the slot of the synchronization signal of the CS 100M1 is stored in the storage unit 109 in advance, for example, by the CS 100M1. A wired network is not used for the synchronization state determination request.

  Subsequently, the PS 200 receives the synchronization state determination request via the wireless network, and acquires the transmission channel and slot information of the synchronization signal of the request source CS 100M2 and the request destination CS 100M1. Note that the PS 200 may make an inquiry to the CS 100M1 in order to obtain information on the transmission channel and slot of the CS100M1 synchronization signal.

  Subsequently, the PS 200 sets each reception window based on, for example, the acquired information on each transmission channel and slot. The PS 200 receives the synchronization signals of the CS 100M1 and the CS 100M2 via the wireless network.

  PS 200 determines the synchronization state between CS 100M1 and CS 100M based on the reception position of the synchronization signal in each reception window. The PS 200 notifies the time lag information including the determination result of the synchronization state to the CS 100M1 via the wireless network. The signal including time lag information transmitted by the PS 200 is an example of a synchronization state response signal.

  Therefore, the CS 100M1 can confirm the synchronization state with the other CS 100 by acquiring the information on the time lag from the PS 200 even if the wired network cannot be used with the other CS 100 (for example, the CS 100M).

  As shown in FIGS. 7 to 9, the PS 200 can identify the transmission source of the synchronization signal with high accuracy by including the ID of the CS 100 together with the Syncword in the communication frame of the synchronization signal. Accordingly, it is possible to improve the accuracy of determining the synchronization state by the PS 200.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

  INDUSTRIAL APPLICABILITY The present invention is useful for a base station apparatus and a communication system that can synchronize a plurality of base stations with high precision even when a predetermined synchronization signal is not received.

1000 Communication system 100 Base station apparatus (CS)
101 wireless communication unit 102 antenna unit 103 wired communication unit 104 wireless communication determination unit 105 clock generation unit 106 communication timing determination unit 107 communication timing correction unit 108 synchronization state determination unit 109 storage unit 110 learning processing unit 200 communication terminal (PS)
300 SIP server 400 Telephone 500 Router 600 External network

Claims (4)

A base station device that communicates with other base station devices in a time-sharing manner,
A wireless communication unit that communicates with other communication devices via a wireless network;
A communication timing determination unit for determining a communication timing of a communication signal by the wireless communication unit;
A communication timing correction unit for correcting the communication timing determined by the communication timing determination unit;
A storage unit for storing, together with priority information, candidates for base station devices that can become synchronization state determination request destinations when a synchronization signal from another base station device that is a master is not received at a predetermined reception timing; ,
The priority order stored in the storage unit is the order of priority given to other base station apparatuses in a higher hierarchy than the base station apparatus in the same hierarchy as the base station apparatus,
When the communication timing correction unit receives a synchronization state response signal from the other base station device in response to a synchronization state confirmation signal sent to another base station device determined based on the priority information, A base station apparatus that corrects the communication timing based on a synchronization state response signal. The base station apparatus according to claim 1,
It has a wired communication unit that communicates with other communication devices via a wired network,
If the synchronization signal from the other base station device is not received at a predetermined reception timing, the synchronization signal is sent by the wired communication unit,
The communication timing correction unit is a base station device that corrects the communication timing based on a synchronization state response signal received by the wired communication unit. The base station apparatus according to claim 1,
When a synchronization signal from another base station apparatus is not received at a predetermined reception timing, at least one of the transmission channel or slot of the synchronization signal of the base station apparatus that is the master of synchronization state determination via the wireless communication unit Send a synchronization status confirmation signal to the communication terminal along with the information,
A base station apparatus that corrects the communication timing based on a synchronization state response signal when received from the communication terminal. A communication system in which a plurality of base station devices including a first base station device and a second base station device communicate by a time division method,
The first base station apparatus
A wireless communication unit that communicates with other communication devices via a wireless network;
A communication timing determination unit for determining a communication timing of a communication signal by the wireless communication unit;
A communication timing correction unit for correcting the communication timing determined by the communication timing determination unit;
A storage unit that stores, together with priority order information, candidates for a second base station device that can be a synchronization state determination request destination when a synchronization signal from another base station device that is a master is not received at a predetermined reception timing And
The priority order stored in the storage unit is the order of priority given to other base station apparatuses in a higher hierarchy than the base station apparatus in the same hierarchy as the first base station apparatus,
The second base station apparatus that has received the synchronization state confirmation signal from the first base station apparatus that does not receive the synchronization signal at a predetermined reception timing receives and receives the synchronization signal generated by the first base station apparatus. A synchronization state is determined based on a difference from a scheduled timing, and a synchronization state response signal including a determination result of the synchronization state is sent to the first base station device,
The communication timing correction unit of the first base station device corrects the communication timing based on the synchronization state response signal when receiving the synchronization state response signal from the second base station device.

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