JP2011087126A - Wireless base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless base station that has an appropriate number of stations with GPS, which are transmission start points of synchronous signals, and saves system cost if synchronization is established among a plurality of wireless base stations. <P>SOLUTION: The wireless base station is provided with a synchronous error acquisition unit which acquires a synchronous error between the previous wireless base station and the station itself, and a controller which adds the synchronous error acquired by the synchronous error acquisition unit to an integrated synchronous error value received from the previous wireless base station to update the integrated synchronous error value and determines whether the station itself requires a GPS receiver based on the updated integrated synchronous error value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

 The present invention relates to a radio base station.

Conventionally, the following three methods are known as methods for establishing synchronization between a plurality of radio base stations.
(1) A GPS (Global Positioning System) receiver is provided in each radio base station, and synchronization between the radio base stations is established based on a one-second pulse synchronized from the global standard time transmitted from a GPS satellite.
(2) Connection between wireless base stations using a standard protocol (for example, IEEE1588) for connecting between wireless base stations via a network such as Ethernet (registered trademark). Establish.
(3) Establishing synchronization between radio base stations by connecting radio control devices (REC: Radio Equipment Control) provided in each radio base station and synchronizing between RECs (for example, the following patents) Reference 1).

Special table 2007-523570 gazette

  In the above method (1), since the GPS receiver is expensive, GPS mounting stations are arranged at predetermined intervals while a plurality of radio base stations are connected in multiple stages (chain connection), and the GPS mounting station is followed by GPS. System configuration that establishes synchronization between radio base stations by transmitting a synchronization signal to a non-implemented station and repeating a process of transmitting a synchronization signal from a GPS non-implemented station that has received the synchronization signal to a subsequent GPS non-implemented station By doing so, the system cost was reduced.

 When a plurality of wireless base stations are connected in this way, the synchronization signal is delayed according to the communication speed between the stations, so that a synchronization error is accumulated each time the synchronization signal is transmitted / received between the stations. . Therefore, it is necessary to determine the arrangement of the GPS mounting stations so that this synchronization error falls within the allowable range. However, if the location of the GPS implementation stations is determined so that the synchronization error is within the allowable range, simply by theoretical calculation, the number of GPS implementation stations becomes more than necessary, and the system cost cannot be reduced as expected. There is sex.

  The present invention has been made in view of such circumstances, and in the case of establishing synchronization between a plurality of radio base stations, the number of GPS mounting stations that serve as transmission start points of synchronization signals is suppressed to an appropriate number, and the system cost is reduced. It is an object of the present invention to provide a radio base station capable of reducing the above.

  In order to achieve the above object, a radio base station according to the present invention includes a synchronization error acquisition unit that acquires a synchronization error between a preceding radio base station and the own station, and a synchronization received from the preceding radio base station. The synchronization error integration value is updated by adding the synchronization error acquired by the synchronization error acquisition unit to the error integration value. Based on the updated synchronization error integration value, the local station detects the GPS receiver. And a control unit that determines whether or not it is necessary.

  In the radio base station, when the control unit determines that the local station does not require a GPS receiver, the control unit transmits the updated synchronization error integrated value to the subsequent radio base station. Is determined to require a GPS receiver, the updated synchronization error integrated value is initialized and transmitted to a subsequent radio base station.

  In the radio base station, the control unit transmits the updated synchronization error integrated value to the subsequent radio base station regardless of a determination result of whether or not the own station requires a GPS receiver. In addition, if it is determined that the own station requires a GPS receiver, the synchronization correction is performed for the radio base station determined to require the GPS receiver before the own station based on the updated synchronization error integrated value. It is characterized by determining whether a GPS receiver can be deleted by performing.

  Further, in the above radio base station, the control unit is the updated base station obtained at the radio base station two before the radio base station determined to require a GPS receiver before the own station. When the difference between the synchronization error integrated value and the updated synchronization error integrated value obtained at the local station satisfies a predetermined condition, the radio base station determined to require a GPS receiver before the local station. Among them, the radio base station immediately before determines that the GPS receiver can be deleted.

Further, in the above radio base station, when the control unit determines that the GPS receiver can be deleted, the control unit determines a correction target base station that requires the synchronization correction, and synchronizes with the correction target base station. The correction value is notified.
In the radio base station, the control unit notifies the base station management apparatus of a determination result as to whether or not the GPS receiver can be deleted.
In the radio base station, the control unit notifies the base station management apparatus of a determination result as to whether or not the own station needs a GPS receiver.
Further, in the above radio base station, the synchronization error acquisition unit obtains a known maximum synchronization error corresponding to an error factor such as a communication line rate determined at the time of establishing communication between the radio base station in the previous stage and the own station. It is acquired as a synchronization error.

 According to the present invention, it is possible to determine whether or not the own station requires a GPS receiver according to the actual installation conditions of each radio base station. As a result, the system cost can be reduced.

FIG. 2 is a block configuration diagram of a radio base station B (i) according to the first embodiment of the present invention. It is an operation | movement flowchart of the radio | wireless control apparatus 20 in radio base station B (i). It is a figure which shows the arrangement | positioning of the GPS implementation station determined using the theoretical method, and the arrangement | positioning of the GPS implementation station determined using radio | wireless base station B (i) in this embodiment. It is a 1st operation | movement flowchart of the radio | wireless control apparatus 20 in 2nd Embodiment. It is a 2nd operation | movement flowchart of the radio | wireless control apparatus 20 in 2nd Embodiment. It is explanatory drawing regarding the synchronization timing correction based on the synchronization correction value Tc2 implemented in the correction target base station.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a block configuration diagram of a radio base station B according to the first embodiment of the present invention. As shown in FIG. 1, the radio base station B (i) includes a radio device (RE: Radio Equipment) 10 and a radio control device (REC: Radio Equipment Control) 20. The radio base station B (i) is connected to other radio base stations in multiple stages (chain connection), and i in the code indicates the base station number assigned to each radio base station in the order of connection. ing. That is, the radio base station B (i) means the i-th radio base station.

  The radio apparatus 10 performs signal processing of radio signals. Specifically, the radio control apparatus 20 performs town conversion of a radio band reception signal received via the antenna 10a to a baseband band. A processable reception baseband signal is generated, and the reception baseband signal is output to radio control apparatus 20. In addition, the radio apparatus 10 generates a transmission signal that can be transmitted by radio by up-converting the transmission baseband signal input from the radio control apparatus 20 into a radio band, and transmits the transmission signal to the radio wave via the antenna 10a. Send.

The radio control apparatus 20 performs baseband signal processing. Specifically, the radio control apparatus 20 generates a transmission baseband signal to be transmitted and outputs the transmission baseband signal to the radio apparatus 10 while being input from the radio apparatus 10. Predetermined signal processing is performed based on the received baseband signal. In addition, the radio control device 20 includes a radio control device (not shown) of the radio base station B (i-1) installed in the front stage and a radio control of the radio base station B (i + 1) installed in the rear stage. It is chain-connected so that it can communicate with a device (not shown).
In FIG. 1, since the configuration of the radio base station B (i-1) at the front stage and the radio base station B (i + 1) at the rear stage are the same as those of the radio base station B (i), the illustration is simplified. Yes.

  Furthermore, the radio network controller 20 includes a synchronization error acquisition unit 20a that acquires a synchronization error between the preceding radio base station B (i-1) and its own station, and a previous radio base station B (i + 1). The synchronization error integration value is updated by adding the synchronization error acquired by the synchronization error acquisition unit 20a to the received synchronization error integration value, and the local station receives GPS based on the updated synchronization error integration value. And a control unit 20b for determining whether or not a machine is required. Details of the functions of the synchronization error acquisition unit 20a and the control unit 20b will be described later.

Next, the operation of the radio base station B (i) configured as described above, in particular, the operation for determining whether or not the own station needs a GPS receiver will be described in detail.
FIG. 2 is a flowchart showing the operation of the radio network controller 20 in the radio base station B (i). As shown in FIG. 2, the synchronization error acquisition unit 20a of the radio network controller 20 acquires the synchronization error Tei between the preceding radio base station B (i-1) and its own station (step S1).

 Specifically, the synchronization error acquisition unit 20a is configured to detect a known maximum synchronization error corresponding to an error factor such as a communication line rate determined when establishing communication between the preceding radio base station B (i-1) and its own station. Is acquired as a synchronization error Tei. That is, the internal memory of the wireless control device 20 stores table data indicating a correspondence relationship between an error factor such as a communication line rate and the maximum synchronization error, and the synchronization error acquisition unit 20a is determined when communication is established. A maximum synchronization error corresponding to an error factor such as a communication line rate is read from the table data and acquired as a synchronization error Tei.

 Then, the control unit 20b of the radio control device 20 adds the synchronization error acquired by the synchronization error acquisition unit 20a to the synchronization error integrated value Te [i-1] received from the preceding radio base station B (i-1). The synchronization error integrated value Te [i-1] is updated by adding Te (step S2). The updated synchronization error integrated value is Te [i] (= Te [i-1] + Tei).

 Subsequently, the control unit 20b determines whether or not the updated synchronization error integrated value Te [i] is larger than Tt / 2 (step S3). Here, Tt is an allowable standard value of synchronization error between base stations. That is, when Te [i] ≦ Tt / 2, since the synchronization error accumulated up to the own station is included in the allowable standard value, it can be determined that the GPS receiver is not necessary for the own station. On the other hand, when Te [i]> Tt / 2, since the synchronization error accumulated up to the local station exceeds the allowable standard value, it can be determined that the local station needs a GPS receiver.

 In the above step S3, in the case of “Yes”, that is, when Te [i]> Tt / 2 and it is determined that the GPS receiver is necessary for the own station, the control unit 20b does not accept the determination result. The base station management apparatus shown in the figure is notified (step S4). This base station management apparatus determines that a GPS receiver is necessary because it is connected to the first (ie, first) radio base station B (1) via a backhaul (wired communication network). The th radio base station B (i) is connected to the first radio base station B (1) through the backhaul from the previous (i-1) th radio base station B (i-1) to the first radio base station B (i). The determination result is notified (transmitted) to the base station management apparatus.

Then, as described above, the control unit 20b notifies the base station management device of the determination result that the own station needs a GPS receiver, and then sets the updated synchronization error integrated value Te [i] to “0”. Is transmitted to the radio base station B (i + 1) at the subsequent stage (step S5).
On the other hand, in the case of “No” in Step S3, that is, when Te [i] ≦ Tt / 2 and it is determined that the GPS receiver is not required for the own station, the control unit 20b The synchronization error integrated value Te [i] is transmitted to the subsequent radio base station B (i + 1) without being initialized (step S6).

By executing the processing of steps S1 to S6 as described above, each of the radio base stations B (i) connected in a chain, the base station management apparatus, and thus the system administrator, can determine what radio base station B (i ) To know if a GPS receiver should be installed.
Hereinafter, in comparison with a method for theoretically determining a radio base station (GPS implementation station) on which a GPS receiver is to be mounted, in this embodiment, each radio base station B (i) performs the processing of steps S1 to S6. A specific description will be given of how the GPS implementation station is determined by executing.

First, theoretically, from the value of n obtained by substituting the theoretical maximum value Temax of the synchronization error between base stations and the allowable standard value Tt of the synchronization error between base stations into the following equation (1), the chain If a GPS receiver is mounted every n stations in a plurality of connected radio base stations, it is possible to keep the synchronization error of the non-GPS mounting stations existing between the GPS mounting stations within the allowable standard value Tt. .
n = int (Tt / 2 · Temax) +1 (1)
FIG. 3A is a diagram showing an arrangement of GPS mounting stations determined using the above equation (1). As shown in FIG. 3 (a), when the first radio base station B ₁ and GPS implementations station, n-th radio base station B _n is determined as the next GPS implementations station, 2n-th radio base station B _2n is determined as the next GPS implementation station.

In the above-described theoretical method, if n calculated from the above equation (1) is used and a plurality of radio base stations connected in a chain simply installs GPS receivers every n stations, GPS non-synchronization is possible. The synchronization error of the mounting station can be kept within the allowable standard value Tt. However, as can be seen from the fact that this theoretical method uses the theoretical maximum value Temax of the synchronization error between base stations in the above equation (1), the synchronization error of the GPS non-implemented station is always obtained under any condition. Is a method of determining the GPS mounting station so that it falls within the allowable standard value Tt, and is a method that is largely shifted to the safe side.
Therefore, in this theoretical method, since there is a possibility that the number of GPS mounting stations may be reduced depending on the installation conditions of the radio base station, the GPS mounting stations are always arranged every n stations. There is room for improvement in terms of cost reduction.

  On the other hand, in the present embodiment, each of the radio base stations B (i) connected in a chain executes the processing of steps S1 to S6, so that the updated synchronization error integrated value Te [i] obtained by the own station is obtained. The radio base station B (i) that satisfies the condition that is greater than Tt / 2 is determined as the GPS implementation station. FIG. 3B is a diagram showing an arrangement of GPS mounting stations determined by the radio base station B (i) in the present embodiment executing the processes of steps S1 to S6. In FIG. 3B, i = 1, that is, the first radio base station B (1), the jth radio base station B (j), and the kth radio base station B (k) are implemented by GPS. The case where it is determined as a station is illustrated.

  The updated synchronization error integrated value Te [j] obtained at the j-th radio base station B (j) is the synchronization error Tei (Te2 to Tej obtained at the radio base stations B (2) to B (j). ) Are all added. Since these synchronization errors Tei are synchronization errors between the own station and the preceding radio base station, they differ depending on the installation conditions of the own station and the preceding radio base station. Specifically, since the communication line rate determined at the time of establishing communication differs depending on the installation conditions of the own station and the radio base station in the preceding stage, the synchronization error Tei obtained corresponding to the communication line rate also varies depending on the installation conditions. .

In other words, in the present embodiment, whether or not the own station needs a GPS receiver is determined according to the actual installation conditions of each radio base station B (i). The base station number j of the radio base station B (j) determined to be necessary by the GPS receiver can be made smaller than n by the theoretical method (the same applies to the radio base station B (k)).
Therefore, according to the present embodiment, it is possible to determine whether or not the own station needs a GPS receiver according to the actual installation conditions of each radio base station B (i). It is possible to suppress the number of GPS mounting stations serving as transmission starting points to an appropriate number, and as a result, it is possible to reduce the system cost.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Note that the radio base station B (i) in the second embodiment is different only in the operation of the radio network controller 20, so that the following description will focus on the operation of the radio network controller 20 and other apparatus configurations. The description of these will be omitted.
FIG. 4 is a flowchart showing the operation of the radio network controller 20 in the second embodiment. As shown in FIG. 4, the synchronization error acquisition unit 20a of the radio network controller 20 acquires the synchronization error Tei between the preceding radio base station B (i-1) and its own station (step S11).

 Then, the control unit 20b of the radio control device 20 adds the synchronization error acquired by the synchronization error acquisition unit 20a to the synchronization error integrated value Te [i-1] received from the preceding radio base station B (i-1). The synchronization error integrated value Te [i] is updated by adding Te, and the updated synchronization error integrated value Te [i] is obtained (step S12). Subsequently, the control unit 20b determines whether or not the updated synchronization error integrated value Te [i] is larger than Tt / 2 (step S13).

In the above-described step S13, if “Yes”, that is, Te [i]> Tt / 2 and it is determined that a GPS receiver is necessary for the own station, the control unit 20b determines that the determination result is not valid. The base station management apparatus shown in the figure is notified (step S14).
Then, as described above, the control unit 20b notifies the base station management apparatus of the determination result that the GPS station is necessary for the own station, and then transmits the updated synchronization error integrated value Te [i] Transmit to the base station B (i + 1) (step S15).
On the other hand, in the case of “No” in Step S13, that is, when Te [i] ≦ Tt / 2 and it is determined that the GPS receiver is not necessary for the own station, the control unit 20b The synchronization error integrated value Te [i] is transmitted to the subsequent radio base station B (i + 1) (step S16).

  Thus, compared with steps S1 to S6 in the first embodiment, the above steps S11 to S16 are obtained at the local station regardless of whether or not the local station requires a GPS receiver. The difference is that the updated synchronization error integrated value Te [i] is transmitted to the radio base station B (i + 1) at the subsequent stage. In other respects, Steps S11 to S16 correspond to Steps S1 to S6 in the first embodiment.

  In addition, after step S15, the control unit 20b integrates the updated synchronization error obtained in the two previous radio base stations among the radio base stations determined to require the GPS receiver before the own station. The difference Ted between the value and the updated synchronization error integrated value Te [i] obtained at the local station is calculated (step S17). Then, the control unit 20b determines whether the difference Ted satisfies the condition of Tt ≦ Ted ≦ Tt + Temax, and requires a GPS receiver before the own station on the assumption that the synchronization correction is performed. It is determined whether or not the determined radio base station can delete the GPS receiver by the previous radio base station (step S18).

  In step S18, in the case of “Yes”, that is, on the assumption that the synchronization correction is performed, the radio base station immediately before the radio base station determined to require the GPS receiver before the local station receives the GPS reception. When it is determined that the machine can be deleted, the control unit 20b notifies the base station management apparatus of the determination result (step S19). In the above-described step S18, in the case of “No”, that is, among the radio base stations determined to require the GPS receiver before the own station, the radio base station immediately before can delete the GPS receiver. If not determined, the control unit 20b ends the process of FIG.

Then, the control unit 20b determines a correction target base station that requires synchronization correction, and notifies the correction target base station of the synchronization correction value Tc2 (step S20). Specifically, the control unit 20b determines radio base stations B (i-1) to B (i-nout-1) as correction target base stations that require synchronization correction. Note that nout is expressed by the following equation (2), and the synchronization correction value Tc2 is expressed by the following equation (3).
nout = int ((Ted−Tt / 2) / Temax) +1 (2)
Tc2 = Ted−Tt / 2 (3)

  By executing the processes of steps S11 to S20 as described above, each radio base station B (i) performs synchronization correction from the radio base stations that have been determined to require a GPS receiver once. As a premise, it is possible to determine a radio base station from which a GPS receiver can be deleted.

  For example, each radio base station B (i) performs the processes of steps S11 to S16, so that the first radio base station B (1) and the jth radio are transmitted in the same manner as in FIG. Assume that the base station B (j) and the k-th radio base station B (k) are determined as GPS-implemented stations (see FIG. 6).

At this time, as viewed from the k-th radio base station B (k), the radio base station that is determined to require a GPS receiver before its own station is the first radio base station. The base station B (1) is indicated, and the radio base station immediately before is the j-th radio base station B (j).
Therefore, in step S17 of the radio base station B (k), the difference Ted is calculated from the updated synchronization error integrated value Te [k] obtained by the own station by two radio base stations (that is, the radio base station B). It can be calculated by subtracting the updated synchronization error integrated value Te [1] obtained in (1)).

  Here, in step S18 of the radio base station B (k), when the difference Ted satisfies the condition of Tt ≦ Ted ≦ Tt + Temax, it is between the radio base station B (k) and the radio base station B (1). A certain radio base station B (j) is determined as a radio base station from which the GPS receiver can be deleted. However, since it is a premise of deleting the GPS receiver that the synchronization correction is performed, in step S20 of the radio base station B (k), the radio base stations B (k-1) to B (k-nout-1) The correction target base stations that require synchronization correction are determined, and the radio base station B (k) notifies the correction target base stations of the synchronization correction value Tc2 and the list of correction target base stations.

  On the other hand, the correction target base station performs the following processing according to the flowchart of FIG. That is, as shown in FIG. 5, the control unit 20b of the correction target base station determines whether or not the synchronization correction value Tc2 has been received (step S31). The synchronization timing is corrected using Tc2 (step S32), and the synchronization correction value Tc2 is transmitted to the preceding correction target base station (step S33). If “No” in step S31, the control unit 20b ends the process in FIG. 5 without performing the processes in steps S32 and S33. As described above, when each correction target base station performs synchronization correction based on the synchronization correction value Tc2, as shown in FIG. 6, the synchronization timing of each correction target base station falls within the allowable standard value.

  As described above, according to the radio base station B (i) in the second embodiment, the GPS receiver is assumed to perform synchronization correction from the radio base stations that have been determined to require the GPS receiver once. Therefore, it is possible to determine radio base stations that can be deleted, and therefore, it is possible to further reduce the number of GPS-implemented stations as compared with the first embodiment, thereby greatly reducing the system cost.

In addition, this invention is not limited to the said embodiment, The following modifications are mentioned.
(1) In the above embodiment, when it is determined that the GPS receiver is necessary for the own station, the case where the determination result is notified to the base station management apparatus is exemplified. However, it is determined that the GPS receiver is not necessary. Even in such a case, the determination result may be notified to the base station management apparatus. Further, the control unit 20b may be provided with a function for displaying the determination result on whether or not the GPS receiver is necessary for the own station on the display unit installed in the own station.

(2) In the above embodiment, when it is determined that there is a radio base station that can delete the GPS receiver among the radio base stations that have been determined to require a GPS receiver, Although the case of notifying the management apparatus has been exemplified, even when it is determined that there is no radio base station capable of deleting the GPS receiver, the determination result may be notified to the base station management apparatus. Further, the control unit 20b may be provided with a function for displaying a determination result on whether there is a radio base station from which the GPS receiver can be deleted on a display unit installed in the own station.

(3) In the above embodiment, the case where the known maximum synchronization error corresponding to the communication line rate determined at the time of establishing communication between the radio base station in the previous stage and the own station is acquired as the synchronization error Tei is exemplified. The method of acquiring Tei is not limited to this, and the synchronization error Tei may be acquired using another method. In the above embodiment, the case where the synchronization error detection unit 20a and the control unit 20b are provided on the wireless control device 20 side is illustrated. However, if the wireless device 10 can perform arithmetic processing, these synchronization error detection units 20a are provided. One or both of the control unit 20b and the control unit 20b may be provided in the wireless device 10.

(4) The operation of the flowchart in the above embodiment may be performed according to an instruction from the base station management apparatus, for example, when the base station is added or removed.

  B (i): wireless base station, 10: wireless device, 10a: antenna, 20: wireless control device, 20a: synchronization error acquisition unit, 20b: control unit

Claims (8)

A synchronization error acquisition unit for acquiring a synchronization error between the radio base station in the previous stage and the own station;
The synchronization error integrated value is updated by adding the synchronization error acquired by the synchronization error acquisition unit to the synchronization error integrated value received from the previous-stage radio base station, and the updated synchronization error integrated value is obtained. A control unit for determining whether or not the local station requires a GPS receiver,
A radio base station comprising:   When determining that the own station does not require a GPS receiver, the control unit determines that the own station requires a GPS receiver while transmitting the updated synchronization error integrated value to a subsequent radio base station. 2. The radio base station according to claim 1, wherein the updated synchronization error integrated value is initialized and transmitted to a subsequent radio base station.   The control unit transmits the updated synchronization error integrated value to the subsequent radio base station regardless of the determination result of whether or not the own station requires a GPS receiver, and the own station receives the GPS receiver. If it is determined that a GPS receiver is required, the GPS receiver can be deleted by performing a synchronization correction on the radio base station determined to require a GPS receiver before itself based on the updated synchronization error integrated value. The radio base station according to claim 1, wherein it is determined whether or not.   The control unit includes the updated synchronization error integrated value obtained in the two previous radio base stations among the radio base stations determined to require a GPS receiver before the own station, and the own station. When the difference from the obtained synchronization error integrated value after the update satisfies a predetermined condition, the radio base station immediately before the radio base station determined to require a GPS receiver before the own station 4. The radio base station according to claim 3, wherein the radio base station determines that the GPS receiver can be deleted.   When determining that the GPS receiver can be deleted, the control unit determines a correction target base station that needs the synchronization correction, and notifies the correction target base station of a synchronization correction value. The radio base station according to claim 3 or 4.   The radio base station according to any one of claims 3 to 5, wherein the control unit notifies a base station management apparatus of a determination result as to whether or not a GPS receiver can be deleted.   The radio base station according to any one of claims 1 to 6, wherein the control unit notifies the base station management apparatus of a determination result as to whether or not the own station requires a GPS receiver. .   The synchronization error acquisition unit acquires a known maximum synchronization error corresponding to a communication line rate determined when communication between the radio base station in the previous stage and the own station is established as the synchronization error. The radio base station as described in any one of -7.

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