JP2004032451A - Clock selection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when a wireless base station as a master connected with an upper station via a transmission line is connected with a wireless base station as a slave via another transmission line (daisy chain configuration), turing off of a selected clock from the transmission line causes the base stations to be put in a mutually synchronized state that the clock becomes dependent on each other of the base stations and the clock becomes unstable. <P>SOLUTION: The master wireless base station directly connected with the upper station, when setting a bus with the upper station, receives an instruction from the upper station, excludes the transmission line to be connected with the slave wireless base station from clock selection candidates, and relays a connection between the slave wireless base station and the upper station. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a clock slave synchronization method, and for example, to the selection of a reference clock signal to be slave synchronized in a radio base station connected to an upper station via a transmission line.
[0002]
[Prior art]
In order to perform communication between a plurality of communication stations in a communication network or the like, network synchronization using a common clock is required. As a method for this, a slave synchronization method in which a plurality of terminal stations use a reference clock of a main communication station in a dependent manner is widely used. Here, an oscillator provided in the main communication station outputs a standard clock, and this standard clock is sent to each terminal station via a transmission line. The terminal station distributes a clock dependent on the standard clock extracted from the transmission line as its own clock.
[0003]
On the other hand, the number of base stations in a daisy-chain configuration has been increasing in wireless base station apparatuses of a mobile phone system due to the coexistence with packet-compatible base station apparatuses and the like. In this configuration, some wireless base stations (slave stations) do not have a transmission line directly connected to a higher-level communication station, but are connected to a parent wireless base station via a transmission line, and are connected via the parent base station. Communicates with a communication station.
[0004]
FIGS. 5A, 5B, and 5C show examples of a line connection configuration between a wireless base station and an upper station in a mobile phone system. FIG. 5A shows a basic configuration in which a wireless base station is connected to a higher-level station via a transmission line network, for example, with a single 1.5 Mbps transmission line (1.5 M-HWY). FIG. 5B shows an example in which two transmission lines are arranged when the transmission capacity increases. FIG. 5C shows an example of the daisy chain configuration. In this configuration, each wireless base station does not have its own transmission line with the upper station, but the child wireless base station communicates with the upper communication station via the parent wireless base station. . The parent wireless base station performs not only data communication between the local station and the upper station, but also relays communication data (for example, layer 1 level) between the child wireless base station and the upper station. The parent wireless base station can recognize the second line connection destination during the startup procedure with the higher-level station. This configuration has the advantage that the transmission line cost can be reduced because a plurality of wireless base stations can consolidate the transmission lines with the upper station into one. It is also effective when there are two or more child wireless base stations.
[0005]
[Problems to be solved by the invention]
However, when a failure occurs in the transmission line, in a daisy chain configuration in which the parent base station and the child base station are connected by the transmission line, the parent base station is once the transmission line between the parent base station and the child base station. The sub-synchronization is performed in accordance with the extracted clock, and the sub-synchronization is maintained even after recovery from the failure. Unless the selected clock is turned off, the selected clock is not changed. For this reason, the clocks depend on each other between the base stations, and the reference clock of each base station becomes very unstable.
[0006]
In view of such a problem, Japanese Patent Application Laid-Open No. H11-088972 discloses that each dependent station sends the individual information of its own station and the received path information together as dependent path information to a lower dependent station, and the lower station receives the received information. A method for judging the quality of a clock corresponding to a plurality of subordinate paths and selecting a clock path is proposed. However, this method has a problem that the hardware configuration of the dependent station is complicated.
[0007]
An object of the present invention is to avoid an operation in which a generated clock becomes unstable by base stations mutually dependent on each other via a transmission line, and without changing the hardware of the base station, An object of the present invention is to make it possible to easily detect a clock path and change a setting.
[0008]
[Means for Solving the Problems]
The clock selection method according to the present invention is characterized in that, in a base station connected to a higher communication station by a transmission line, when the base station establishes a communication path between the higher communication station and the base station, the base station performs Determine the transmission line to select. Further, when there is a first base station connected to the upper communication station via the first transmission line and a second base station connected to the first base station via the second transmission line, the upper communication station The first base station that has received the command from sets the path between the higher-level communication station and the second base station via the first base station. Further, in response to a command from the upper communication station, the first base station excludes the second transmission line connected to the second base station from the transmission lines whose clocks can be selected.
[0009]
A plurality of first transmission lines can be arranged between the first base station and the upper communication station. Also, a plurality of second transmission lines can be arranged between the first base station and the second base station. Also, a plurality of second base stations can be connected to the first base station.
[0010]
After the clock selection is transferred to the lower priority transmission line among the plurality of transmission lines capable of clock selection in the first base station, even if the higher priority transmission line is restored, the transmission line to be clock selected remains unchanged. Can be maintained. Further, the base station can include a clock generation circuit.
[0011]
With such a configuration, particularly in a daisy-chain wireless base station, it is possible to reliably and easily select a clock path without changing hardware.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an example of a clock establishment procedure in the parent wireless base station having the daisy chain configuration shown in FIG. 5C. First, after the parent wireless base station apparatus is started, a start-up procedure for establishing a layer 1 path with the upper station apparatus is started. The connection line configuration of the parent wireless base station is input to the upper station in advance. When the second transmission line of the two transmission lines connected to the parent wireless base station is connected to the child wireless base station device, a daisy-chain command is sent from the higher-level station device in the startup procedure. . When accepting this daisy-chain command, the parent wireless base station apparatus recognizes that the second transmission line is connected to the child wireless base station, and based on software in the local station, the first and second transmission lines. A relay path connecting between the transmission lines is set, and the second transmission line connected to the child radio base station is excluded from the clock selection candidates in the clock selection at the own station. Thereafter, a layer 1 path is established between the child radio base station apparatus and the higher station apparatus, and a start-up procedure is executed.
[0013]
When there are a plurality of transmission lines between the upper station and the parent wireless base station, the priority order of the transmission lines for clock selection is preset in the parent wireless base station. Even when there are a plurality of transmission lines between the child wireless base station and the parent wireless base station, the child wireless base station is similarly set with the priority of clock selection in advance.
[0014]
As described above, in the above method, when the line between the upper station and the parent wireless base station is started, the parent wireless base station receives a command from the upper station and selects the clock (that is, the layer 1 path of the daisy chain). The setting and the exclusion from the clock selection of the transmission line connected to the child wireless base station) are set based on the software set in the own station. Therefore, a special hardware configuration for preventing the clock from becoming unstable on the wireless base station side is not required.
[0015]
FIG. 2 is a block diagram illustrating an example of a wireless base station device. The reference clock in the wireless base station device is generated in synchronization with the clock extracted from the transmission line. This device includes two layer 1 termination units 1-1 and 1-2 that terminate 1.5M-HWY. The clock generator 2 generates various clocks based on the 8 kHz extracted clock 3 extracted by the layer 1 termination unit. The clock generation unit 2 includes a clock generation circuit that generates a clock of 8 kHz and a clock selection circuit that selects a clock to be referred to. In the clock generating unit 2, the PLL circuit compares the phase of the selected clock with 8 kHz obtained by dividing the output clock of the VCO, and outputs the difference as a voltage value to the VCO as feedback to adjust the reference frequency. The VCO frequency is frequency-divided and generated by a frequency dividing circuit as various reference clocks.
[0016]
The wireless base station device further includes a layer 2 termination unit 4 and a main control unit 5. The layer 2 terminator 4 terminates the communication protocol with the upper station via 1.5M-HWY, and relays the message to the main controller 5. The main control unit 5 controls the execution and execution of the communication / startup procedure with the upper station via the layer 2 termination unit 4 via the control bus 6, and controls the setting of the layer 1 path for the layer 1 termination unit 1. , Performs clock selection setting change control on the clock generation unit 2, and performs other necessary control. The in-building HWY 7 is a transmission line through which a transmission / reception signal on the 1.5M-HWY is relayed and transferred via a layer 1 termination unit, and is a transmission line for layer 2 signals and the like.
[0017]
FIG. 3 is a flowchart showing an example of clock selection in the parent wireless base station connected to the two transmission lines shown in FIGS. 5B and 5C. After startup, the radio base station receives a daisy chain command from the upper station and knows the transmission line connected to the child radio base station. When there is no daisy-chain command, the radio base station determines the priority order for selecting a clock among a plurality of transmission lines according to the setting of its own station.
[0018]
In FIG. 3, first, the reference clock 1 input from the layer 1 termination unit 1-1 in FIG. 2 is selected with the first priority. Thereafter, when the reference clock 1 is cut off, the self-running clock output from the clock generation circuit of the own station is selected in the case of the daisy chain configuration, and when the reference clock 1 is restored, the reference clock 1 is again supplied. Selected.
[0019]
When the reference clock 1 is turned off in a non-daisy chain configuration, the reference clock 2 extracted from the layer 1 termination unit 1-2 is selected according to the set priority order. Thereafter, even if the reference clock 1 is restored while the reference clock 2 is being selected, the selection of the reference clock 2 is maintained to suppress frequent changes in the clock selection. When the reference clock 2 is cut off, the free-running clock is selected, and when the reference clock is restored, the reference clock is selected (when both are restored, the reference clock 1 is preferentially selected).
[0020]
FIG. 4 shows another example of connection between an upper station and a wireless base station. FIG. 4A shows an example in which a plurality of (two in this case) transmission lines are arranged between a parent wireless base station and a child wireless base station. FIG. 4B shows a case where two child wireless base stations are connected to the parent wireless base station. If there are a plurality of transmission lines on the upper side, the reliability of clock synchronization can be increased. The clock selection method of the present invention is also effective in these cases.
[0021]
【The invention's effect】
According to the clock connection method of the present invention, when a radio base station in a daisy chain configuration starts up a path with an upper station, it receives a command from the upper station and selects a transmission line connected to a child radio base station by clock selection. Since it is excluded from the candidates, it is possible to easily prevent the clock from becoming unstable on the wireless base station side, and a special hardware configuration for this purpose is not required.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a procedure for setting a path between a radio base station and an upper station.
FIG. 2 is a block diagram showing a configuration example of a wireless base station.
FIG. 3 is a flowchart showing an example of a clock selection method in a parent wireless base station.
FIG. 4 is a diagram showing another configuration example between wireless base stations.
FIG. 5 is a diagram showing an example of a connection configuration between a wireless base station and an upper station.
[Explanation of symbols]
1-1, 1-2 Layer 1 termination unit 2 Clock generation unit 3 Extracted clock 4 Layer 2 termination unit 5 Main control unit 6 Control bus 7 HWY in the rack

Claims (8)

A clock selection method in a base station connected to an upper communication station by a transmission line,
A clock selection method, comprising: determining a transmission line to be clock-selected by the base station based on a command from the upper communication station when establishing a communication path between the upper communication station and the base station. When there is a first base station connected to the upper communication station via a first transmission line, and a second base station connected to the first base station via a second transmission line, the upper communication station 2. The clock selection method according to claim 1, wherein the first base station receiving the instruction from the first base station sets a communication path between the upper communication station and the second base station via the first base station. 3. The clock selection method according to claim 2, wherein upon receiving a command from the upper communication station, the first base station excludes a second transmission line connected to the second base station from transmission lines capable of clock selection. . 3. The clock selection method according to claim 2, wherein a plurality of first transmission lines are arranged between the first base station and the upper communication station. 3. The clock selection method according to claim 2, wherein a plurality of the second transmission lines are arranged between the first base station and the second base station. 3. The clock selection method according to claim 2, wherein a plurality of second base stations are connected to the first base station. After the clock selection is shifted to the lower priority transmission line among the plurality of transmission lines capable of clock selection in the first base station, even if the higher priority transmission line is restored, the transmission line to be clock selected is changed. 5. The clock selection method according to claim 4, wherein the clock selection is maintained. 2. The clock selection method according to claim 1, wherein the base station includes a clock generation circuit.

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