JP2008017073A - Mobile communication system, base station controller, and radio base station-base station controller phase shift detecting method used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system capable of keeping a user data transmission time of a base station controller at a proper value. <P>SOLUTION: When receiving UL Synchronization from a radio base station 2, an inter-device phase difference measurement executing unit 10 compares synchronization results (arrival time difference) with an arrival time difference assumption range, and ends processing without re-measuring an inter-device phase difference by an inter-device phase difference measuring circuit 13 when the arrival time difference is within the assumption range. When the arrival time difference is not within the assumption range, the inter-device phase difference measurement executing unit 10 measures the inter-device phase difference by the inter-device phase difference measuring circuit 13 and updates an inter-device phase difference held in a storage device 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mobile communication system, a base station control device, and a phase shift detection method between a radio base station and a base station control device used therefor, and more particularly to a method of detecting a phase shift between a radio base station and a base station control device. .

  A mobile communication system represented by a mobile phone has become an information transmission means indispensable in today's information society. In this mobile communication system, user data such as voice and packets transmitted from a mobile terminal arrives at a base station control device via a radio base station. At that time, since the area where one radio base station can receive data is limited, it is possible to perform mobile communication from any location by installing a plurality of radio base stations.

  Therefore, when a mobile terminal moves over an area covered by a specific radio base station during communication and communicates with an area covered by another radio base station, communication is performed using the destination radio base station. Need will arise. At this time, in order to avoid a temporary interruption of communication at the moment when the radio base station is switched, as shown in FIG. 7, the mobile terminal 3 is connected to a plurality of radio base stations 2-1, 2-2. Is used in the vicinity of the boundary between the first and second cover areas 201 and 202, a technique is used that enables simultaneous communication with a plurality of radio base stations 2-1 and 2-2.

  The time at which user data transmitted from the plurality of radio base stations 2-1 and 2-2 to the base station control device 1 arrives at the base station control device 1 is the transmission delay time between the radio base station and the base station control device. Therefore, the base station control device 1 receives user data from the radio base stations 2-1 and 2-2 at different timings. The base station controller 1 waits for user data from each of the radio base stations 2-1 and 2-2 for the maximum transmission delay time that can be assumed between the radio base station and the base station controller, and the maximum transmission delay time. After elapses, user data is transmitted to the core network 100.

At this time, the transmission timing after the lapse of the maximum transmission delay time is
Base station controller transmission time (C)
= Radio base station transmission time (A)
+ Phase difference between radio base station and base station controller (α)
+ Maximum transmission delay (β)
(See FIG. 8). Here, the “radio base station transmission time” is the time at which the radio base stations 2-1 and 2-2 transmit user data to the base station control apparatus 1, and is transmitted to the base station control apparatus 1 together with the user data. Sent. The “phase difference between the radio base station and the base station controller” (hereinafter referred to as phase difference) is the time between the time recognized by the radio base stations 2-1 and 2-2 and the time recognized by the base station controller 1. It is a difference and is measured by a synchronization process at the time of system startup, and thereafter held by the base station control device 1.

  As a method of removing the influence of data delay due to the transmission delay between the devices as described above, a temporal variation in the arrival time of the data is detected, and an estimated arrival time of the next and subsequent data is detected from this temporal variation. There is also a method for informing that the transmission timing of data is advanced when the estimated arrival time deviates from the reception window (see, for example, Patent Document 1).

JP 2001-358793 A

  In the conventional mobile communication system described above, the base station controller uses the phase difference when the base station controller transmits user data to the core network, and controls the time recognized by the radio base station as described above. Processing to convert the time recognized by the device is performed.

  Therefore, between the phase difference held by the base station controller and the actual phase difference due to a failure in synchronization processing at the time of system setting or a clock shift between the radio base station and the base station controller after system setting. When a difference occurs, a problem arises that the base station controller cannot correctly determine the transmission timing of user data to the core network.

  When the held phase difference is smaller than the actual phase difference, the transmission timing is advanced, so that a problem arises that the transmission timing is reached before frame reception (see FIG. 9). Also, if the held phase difference is larger than the actual phase difference, the transmission timing is delayed, so the base station controller waits for data from the radio base station more than necessary, and the transfer delay is increased. Occurs (see FIG. 10).

  Since each of the above problems is a problem in the base station control device, as in the technique described in Patent Document 1, when the estimated arrival time deviates from the reception window, notification is made so as to advance the data transmission timing. Can not do it.

  Therefore, an object of the present invention is to solve the above-mentioned problems and to maintain a user data transmission time in the base station control device at an appropriate value, a mobile communication system, a base station control device, and a radio base station used for them. An object of the present invention is to provide a method for detecting a phase shift between base station controllers.

A mobile communication system according to the present invention is a mobile communication system that performs synchronization for each channel establishment between a radio base station and a base station controller,
The base station control device includes a measurement unit that measures a phase difference with the radio base station, a detection unit that detects a phase difference shift with the radio base station from the synchronization result, and the detection unit And a means for correcting the phase difference deviation based on the result of measuring the phase difference again by the measuring means when the phase difference deviation is detected.
The base station control device keeps a phase difference from the radio base station within a certain time.

A base station control apparatus according to the present invention is a base station control apparatus that performs synchronization for each channel establishment with a radio base station,
Measuring means for measuring a phase difference with the radio base station; detecting means for detecting a phase difference deviation with the radio base station from the synchronization result; and detecting the phase difference deviation with the detecting means. Means for correcting the shift of the phase difference based on the result of re-measurement of the phase difference by the measuring means when detected,
The phase difference with the radio base station is kept within a certain time.

A method of detecting a phase shift between a radio base station and a base station controller according to the present invention is a radio base station-base station used in a mobile communication system that performs synchronization every time a channel is established between the radio base station and the base station controller. A phase shift detection method between control devices,
Measurement processing in which the base station control device measures a phase difference with the radio base station, detection processing for detecting a shift in phase difference with the radio base station from the synchronization result, and the detection processing And a process of correcting the phase difference deviation based on the result of measuring the phase difference again by the measurement process when the phase difference deviation is detected in
The base station control device keeps a phase difference from the radio base station within a certain time.

  That is, the mobile communication system of the present invention detects a shift in phase difference between the base station and the base station controller from the result of synchronization performed every time the channel is established between the radio base station and the base station controller. When the phase shift is detected, the phase shift between the radio base station and the base station controller is corrected by correcting the phase shift by performing the phase difference measurement between the radio base station and the base station controller again. It becomes possible to keep within a certain time.

  Further, in the mobile communication system of the present invention, by applying the above-described phase shift detection method, base station control can be performed due to a difference in clock accuracy between the radio base station and the base station control device, a failure of the clock supply device, or the like. Even when a difference occurs in the recognition of the phase difference between the radio base station and the base station controller in the apparatus, the user data transmission time in the base station controller can be maintained at an appropriate value. As a result, it is possible to avoid the occurrence of data transmission delay due to unnecessary buffering and the loss of data due to shortened standby time, thereby improving the communication quality.

  On the other hand, when the above-described phase shift detection method is not applied, the communication quality deteriorates as the phase difference recognition shift generated in the base station control apparatus increases. Clock accuracy is required. In the above-described phase shift detection method, the phase error between the radio base station and the base station control device is recognized and the phase difference is remeasured autonomously. Become. Therefore, the cost can be reduced by reducing the clock accuracy.

  In addition, when the above-described phase shift detection method is not applied, in order to prevent deterioration in communication quality due to an increase in the phase shift recognition shift generated in the base station controller, the radio base station-base station is periodically There is a need to perform phase difference measurements between station controllers. In the above phase shift detection method, the phase error between the radio base station and the base station controller is recognized, and the phase difference is remeasured autonomously. It is possible to reduce the system load associated with.

  As a method of avoiding the above problems, the synchronization result performed every time the channel is established between the radio base station and the base station controller is monitored, the phase recognition deviation between the devices is detected from the synchronization result, and the phase difference is detected again. A method for carrying out the measurement is conceivable. By this method, it becomes possible to keep the phase recognition deviation between the radio base station and the base station controller within a certain time, and the base station controller can keep the user data transmission timing to the core network at the correct timing. Become.

  The present invention has an effect that the user data transmission time in the base station control device can be maintained at an appropriate value by adopting the configuration and operation as described above.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a mobile communication system according to an embodiment of the present invention. In FIG. 1, a mobile communication system according to an embodiment of the present invention includes a radio base station 2, a base station control device synchronization / inter-device phase difference measurement execution unit (hereinafter referred to as inter-device phase difference measurement execution unit) 10, and The base station control device includes a storage device 3 and a clock generation unit 4. In the embodiment of the present invention, since the mobile terminal and the core network are not directly related, their illustration is omitted, and the system configuration is the same as the conventional system configuration shown in FIG.

  The inter-device phase difference measurement execution unit 10 includes an UL (UpLink) Synchronization reception unit 11, a phase shift detection circuit 12, an inter-device phase difference measurement circuit 13, a phase correction circuit 14, and a DL (DownLink) Synchronization transmission unit 15. It is composed of

  The DL synchronization transmission unit 15 determines the DL synchronization transmission timing / target radio base station time from the phase difference between the radio base station and the base station controller, the maximum transmission delay amount, and the time information, and transmits the DL synchronization.

  The UL synchronization reception unit 11 receives the UL synchronization, and determines the transmission timing of DL user data from the synchronization result. The phase shift detection circuit 12 detects the phase difference between the radio base station and the base station controller recognized by the base station controller from the synchronization result (arrival time difference) and the expected arrival time difference range, and the actual radio base station and base station control. A deviation between the phase differences between devices is detected.

  The inter-device phase difference measurement circuit 13 measures the phase difference between the radio base station and the base station control device. The phase correction circuit 14 corrects the inter-device phase difference held in the storage device 3 according to the measurement result of the inter-device phase difference measurement circuit. The storage device 3 holds time information, maximum transmission delay amount, inter-device phase difference, and arrival time difference assumption range. The clock generation unit 4 updates time information.

  FIGS. 2A and 2B are diagrams showing a synchronization operation performed every time a channel between a radio base station and a base station controller is established in one embodiment of the present invention. With reference to FIGS. 2 (a) and 2 (b), a description will be given of a synchronization operation performed each time a channel between a radio base station and a base station control device is established in one embodiment of the present invention.

  When a base station controller connects to a channel, the phase difference (α) between the radio base station and the base station controller recognized by the base station controller and the maximum transmission delay (β) assumed between the radio base station and the base station controller Based on the above, at a timing before the maximum transmission delay amount from the target radio base station time (A), the target radio base station time information is added, and DL Synchronization is transmitted to the radio base station.

That is, the DL Synchronization transmission timing in the base station controller is
DL Synchronization transmission timing
= Target radio base station time (A)
+ Phase difference between radio base stations and base station controllers (α)
-Maximum transmission delay (β)
It is calculated from the formula.

The radio base station 2 that has received the DL synchronization calculates the difference between the target radio base station time information (A) given to the DL synchronization and the time (B) at which the DL synchronization was actually received, and the result is the arrival time difference. The assigned UL Synchronization is transmitted to the base station controller. Therefore, the arrival time difference is
Arrival time difference = BA
It is calculated from the formula.

The base station controller that has received the UL Synchronization calculates the transmission delay amount from the arrival time difference, and transmits the user data with the target radio time information added to the target radio base station time in consideration of the transmission delay amount during subsequent user data transmission. To do. Here, the amount of transmission delay is
Transmission delay amount = maximum transmission delay amount (β) −arrival time difference (B−A)
It is calculated from the formula.

  As described above, since the base station controller transmits DL Synchronization at a timing before the maximum transmission delay amount from the target base station time, the transmission delay amount is within a normally assumed range (several μs to the maximum transmission delay amount). If there is, the arrival time difference given by UL Synchronization is in the range of 0 to the maximum transmission delay amount. Here, if the transmission delay amount is several μs, the arrival time difference≈the maximum transmission delay amount, and if the transmission delay amount is the maximum transmission delay amount, the arrival time difference = 0.

  However, if there is a deviation between the phase difference between the radio base station and the base station controller recognized by the base station controller and the phase difference between the actual radio base station and the base station controller, the deviation If the value exceeds a certain amount, the arrival time difference is outside the range in which the transmission delay amount is normally assumed.

  FIGS. 3A and 3B are diagrams showing a case where the phase recognition of the base station controller is advanced by γ due to the phase difference recognition deviation in one embodiment of the present invention. With reference to FIGS. 3A and 3B, the operation when the phase recognition of the base station controller is advanced by γ due to the phase difference recognition deviation in one embodiment of the present invention will be described.

  In this case, the base station controller transmits DL Synchronization at a timing earlier by γ. As a result, the arrival timing at the radio base station 2 is also advanced by γ, and the arrival time difference is increased by γ. In particular, when γ is larger than the transmission delay amount, the arrival time difference is larger than the maximum transmission delay amount.

  FIGS. 4A and 4B are diagrams showing a case where the phase recognition of the base station controller is delayed by γ due to the phase difference recognition deviation in one embodiment of the present invention. With reference to FIGS. 4A and 4B, the operation when the phase recognition of the base station controller is delayed by γ due to the phase difference recognition deviation in one embodiment of the present invention will be described.

  In this case, the base station control apparatus transmits DL Synchronization at a timing delayed by γ. As a result, the arrival timing at the radio base station is also advanced by γ, and the arrival time difference is reduced by γ. In particular, when the sum of the transmission delay amount and γ is larger than the maximum transmission delay amount, the arrival time difference becomes a negative value.

  In this embodiment, the base station controller monitors the arrival time difference given to UL Synchronization, and if the arrival time difference exceeds the assumed range, the base station controller recognizes the radio base station-base station It is determined that a difference has occurred between the phase difference between the control devices and the actual phase difference between the radio base station and the base station control device, and the phase difference between the radio base station and the base station control device is measured again.

  FIG. 5 is a flow chart showing phase shift detection / inter-device phase difference update processing in one embodiment of the present invention. The phase shift detection / inter-device phase difference update processing in one embodiment of the present invention will be described with reference to FIGS.

  When receiving the UL Synchronization from the radio base station 2, the inter-device phase difference measurement execution unit 10 compares the synchronization result (arrival time difference) with the expected arrival time difference range (step S1 in FIG. 5). When the arrival time difference is within the assumed range, the inter-device phase difference measurement execution unit 10 ends the process without performing re-measurement of the inter-device phase difference by the inter-device phase difference measurement circuit 13.

  On the other hand, when the arrival time difference is outside the assumed range, the inter-device phase difference measurement execution unit 10 performs the inter-device phase difference measurement by the inter-device phase difference measurement circuit 13 (step S2 in FIG. 5) and is held in the storage device 3. The inter-device phase difference is updated (step S3 in FIG. 5). Here, the expected arrival time difference range is 0 to the maximum transmission delay amount.

  When the assumed range is set to be narrow, it is possible to keep the recognition difference of the inter-device phase difference small, but on the other hand, the operation frequency of the inter-device phase difference measurement process increases, which may increase the load on the system. On the other hand, if the assumed range is set wide, the operation frequency of the inter-device phase difference measurement process is reduced, so that the load on the system can be reduced. However, there is a concern that the detection sensitivity of the phase difference recognition deviation is lowered.

  As described above, in the present embodiment, by applying the above-described phase shift detection method, the base station control device may cause a difference in clock accuracy between the radio base station and the base station control device or a failure of the clock supply device. Even when a shift occurs in the phase difference recognition between the radio base station and the base station controller, the user data transmission time in the base station controller can be kept at an appropriate value.

  As a result, in this embodiment, it is possible to avoid the occurrence of data transmission delay due to unnecessary buffering and the loss of data due to shortened standby time, thereby improving the communication quality.

  In addition, when the above-described phase shift detection method is not applied, the communication quality deteriorates as the phase difference recognition shift generated in the base station control apparatus increases, which is higher than the base station control apparatus. Clock accuracy is required. On the other hand, in the present embodiment, since the above-described phase shift detection method is applied, the phase error between the radio base station and the base station control device is recognized, and the phase difference is remeasured autonomously. Therefore, high clock accuracy is not required for the base station controller. Therefore, in this embodiment, the cost can be reduced by reducing the clock accuracy.

  Further, when the above-described phase shift detection method is not applied, in order to prevent deterioration in communication quality due to an increase in the phase difference recognition shift generated in the base station controller, the radio base station-base station is periodically There is a need to perform phase difference measurements between station controllers. On the other hand, in the present embodiment, since the above-described phase shift detection method is applied, the phase error between the radio base station and the base station control device is recognized, and the phase difference is remeasured autonomously. Therefore, periodic phase difference measurement is not required, and the system load accompanying the phase difference measurement can be reduced.

  FIG. 6 is a flowchart showing phase shift detection / inter-device phase difference update processing in another embodiment of the present invention. A mobile communication system according to another embodiment of the present invention has the same configuration as that of the mobile communication system according to the embodiment of the present invention shown in FIG. 1, and therefore, referring to FIGS. A phase shift detection / inter-device phase difference update process in another embodiment of the present invention will be described. In this embodiment, the number of phase shift detections is counted, and a phase shift detection threshold is set in advance.

  When receiving the UL Synchronization from the radio base station 2, the inter-device phase difference measurement execution unit 10 compares the synchronization result (arrival time difference) with the expected arrival time difference range (step S11 in FIG. 6). When the arrival time difference is within the assumed range, the inter-device phase difference measurement execution unit 10 clears the number of phase shift detections (step S13 in FIG. 6), and ends the process without performing the re-measurement of the inter-device phase difference.

  On the other hand, when the arrival time difference is outside the assumed range, the inter-device phase difference measurement execution unit 10 increments the number of phase shift detection (step S12 in FIG. 6), and determines whether the number of phase shift detection exceeds the phase shift detection threshold. (FIG. 5, step S14). If the number of phase shift detections does not exceed the phase shift detection threshold, the inter-device phase difference measurement execution unit 10 ends the process without performing re-measurement of the inter-device phase difference.

  The inter-device phase difference measurement execution unit 10 determines that a phase shift has occurred if the number of phase shift detections exceeds the phase shift detection threshold and clears the number of phase shift detections (step S15 in FIG. 6). Then, the inter-device phase difference is measured (step S16 in FIG. 6), and the inter-device phase difference is updated (step S17 in FIG. 6). Here, the expected arrival time difference range is 0 to the maximum transmission delay amount.

  As described above, in this embodiment, the number of phase shift detections is counted, and the phase shift detection threshold value is set in advance, thereby avoiding the operation of the apparatus phase difference measurement process due to erroneous detection of the phase shift. Can do.

It is a block diagram which shows the structure of the mobile communication system by one Example of this invention. (A), (b) is a figure which shows the synchronous operation implemented whenever the channel between the wireless base station-base station control apparatus in one Example of this invention is established. (A), (b) is a figure which shows the case where the phase recognition of a base station control apparatus advances by (gamma) by the phase difference recognition deviation in one Example of this invention. (A), (b) is a figure which shows the case where the phase recognition of a base station control apparatus is delayed by (gamma) by the phase difference recognition deviation in one Example of this invention. It is a flowchart which shows the phase shift detection / phase difference update process between apparatuses in one Example of this invention. It is a flowchart which shows the phase shift detection / phase difference update process between apparatuses in the other Example of this invention. It is a figure which shows the flow of the user data in the conventional mobile communication system. It is a figure which shows the transmission timing in the base station control apparatus when there is no conventional phase error. It is a figure which shows the transmission timing in the base station control apparatus when the phase error of the conventional negative direction generate | occur | produces. It is a figure which shows the transmission timing in the base station control apparatus when the conventional phase error of the positive direction generate | occur | produces.

Explanation of symbols

2 wireless base station 3 storage device 4 clock generation unit 10 base station control device synchronization / inter-device phase difference measurement execution unit 11 UL synchronization signal receiving unit 12 phase shift detection circuit 13 inter-device phase difference measurement circuit 14 phase correction circuit 15 DL synchronization transmission Part

Claims (9)

A mobile communication system that performs synchronization for each channel establishment between a radio base station and a base station controller,
The base station control device includes a measurement unit that measures a phase difference with the radio base station, a detection unit that detects a phase difference shift with the radio base station from the synchronization result, and the detection unit And a means for correcting the phase difference deviation based on the result of measuring the phase difference again by the measuring means when the phase difference deviation is detected in
The mobile communication system, wherein the base station control device keeps a phase difference from the radio base station within a certain time.   The base station controller compares the synchronization result with a preset arrival time difference assumption range, and measures the phase difference again by the measurement means when the synchronization result is outside the arrival time difference assumption range. The mobile communication system according to claim 1.   The detection means counts the number of detections of the phase difference deviation, and detects the occurrence of the phase difference deviation when the number of detections exceeds a preset phase deviation detection threshold. The mobile communication system according to claim 1 or 2. A base station controller that performs synchronization with a radio base station every time a channel is established,
Measuring means for measuring a phase difference with the radio base station; detecting means for detecting a phase difference deviation with the radio base station from the synchronization result; and detecting the phase difference deviation with the detecting means. Means for correcting the shift of the phase difference based on the result of re-measurement of the phase difference by the measuring means when detected,
A base station control apparatus, characterized in that a phase difference from the radio base station is kept within a certain time.   5. The comparison between the synchronization result and a preset expected arrival time difference range is performed, and the phase difference is measured again by the measuring means when the synchronization result is outside the expected arrival time difference range. The base station controller described.   The detection means counts the number of detections of the phase difference deviation, and detects the occurrence of the phase difference deviation when the number of detections exceeds a preset phase deviation detection threshold. The base station control apparatus according to claim 4 or 5. A method of detecting a phase shift between a radio base station and a base station control device used in a mobile communication system that performs synchronization for each channel establishment between a radio base station and a base station control device,
Measurement processing in which the base station control device measures a phase difference with the radio base station, detection processing for detecting a shift in phase difference with the radio base station from the synchronization result, and the detection processing And a process of correcting the phase difference deviation based on the result of measuring the phase difference again by the measurement process when the phase difference deviation is detected in
A method of detecting a phase shift between a radio base station and a base station control device, wherein the base station control device keeps a phase shift from the radio base station within a predetermined time.   The base station controller compares the synchronization result with a preset arrival time difference assumption range, and measures the phase difference again by the measuring means when the synchronization result is outside the arrival time difference assumption range. The method of detecting a phase shift between a radio base station and a base station controller according to claim 7.   In the detection process, the base station controller counts the number of detections of the phase difference deviation, and detects the occurrence of the phase difference deviation when the number of detections exceeds a preset phase deviation detection threshold. 9. The method for detecting a phase shift between a radio base station and a base station controller according to claim 7 or claim 8, wherein:

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