KR20000015168A - Method for compensating delay of pilot signal in mobile telecommunication system - Google Patents

Abstract

PURPOSE: A method for compensating delay of pilot signal in a mobile telecommunication system is provided to smoothly perform hand-off without blocking of a call by compensating for time delay of pilot signal due to the delay of transmission medium. CONSTITUTION: The method comprises the steps of: designating a first compensated pilot pseudo noise offset for compensating for time delay of pilot signal due to the delay of transmission medium by altering database; when transmitting telecommunication signal from multi-sector base station to a micro-base station, by allowing the multi-sector base station to process the telecommunication signal using the altered database, the first compensated pilot pseudo noise offset parameter, compensating the time delay due to the transmission medium and the time delay of the pilot signal. Thus, the method compensates for time delay due to the optical fiber transmission, periodically or by operator's request, thereby enhancing the reliability of the system.

Description

Pilot signal delay compensation method in mobile communication system

The present invention compensates the time delay of a pilot signal due to a time delay of a transmission medium (Optical Fiber, etc.) in a micro cellular mobile communication system using a code division multiple access (CDMA) method. The present invention relates to a pilot signal delay compensation method capable of improving call quality by smoothly performing handoff without disconnection.

1 is a diagram illustrating an exemplary mixed operation configuration of an existing cellular mobile communication system and a micro cellular mobile communication system of a general code division multiple access (CDMA) scheme.

The micro cellular mobile communication system is a system for increasing the frequency use efficiency and stably providing high-speed data service in the future by providing a mobile communication service centering on a small cell of several hundred meters radius. Base station (mBS) 17, multi-sector BTS (or base station (RF-less BTS) except radio frequency signal processing unit in existing base station (BTS) 12)) 16, control station (BSC) 13), an operating station (BSM) 15, and a switching center (MSC) 14.

The mobile station (MS) 11 wirelessly communicates with the micro base station 17, transmits and receives call connection and traffic messages, and connects a user to the micro base station 17 to signal processing functions for voice conversion and incoming / outgoing calls. Do it.

The micro base station (mBS) 17 is a base station having only a radio frequency signal processing unit, i.e., an up-and-down frequency converter, an amplifier, a filter, an antenna, etc., and transmits a signal transmitted through an optical fiber from the multi-sector base station 16 through a CDMA. It converts the frequency into a band and transmits the signal, or converts the signal of the CDMA band received by the mobile station 11 and transmits the signal to the multi-sector base station 16 through the optical fiber to serve as an interface with the mobile station 11. .

The multi-sector BTS 16 is a part of the existing base station 12 excluding a radio frequency (RF) signal processing unit, and is a digital unit for modulating and demodulating a CDMA signal and a control station 13. Interface unit, control processor, Global Positioning System (GPS) unit to provide timing and system reference clock, adapter unit to convert electrical signals from multi-sector base station 16 into signals suitable for transmission media called optical fiber Unlike the existing three sectors, the base station has a function of adding sectors to operate more than four sectors.

The multi-sector base station 16 performs a call control function such as call connection and transmission / reception of traffic data with the mobile station 11 through the micro base station 17 at a remote location using an optical fiber, and is connected to the control station 13 by wire. The mobile station 11 transmits a call connection or traffic message to the control station 13 or a message transmitted from the control station 13 to the mobile station 11 to the mobile station 11 through the micro base station 17. Function to transmit. It also communicates with the control station 13 for signal processing and the operating station 15 to perform maintenance processing.

The control station (BSC) 13 is connected to the multisector base station 16 to perform call processing functions such as an incoming / outgoing call function and a handoff between the multisector base station 16 and the switching station 14, and is connected to the operating station 15. To perform a processing function for maintenance of the base station 12.

The management station (BSM) 15 manages the database while communicating with the control station 13 and the multisector base station 16, and performs maintenance and statistical management functions of the control station 13 and the multisector base station 16. Perform.

The switching center (MSC) 14 is connected to the control station 13, the Public Switched Telephone Network (PSTN) and other switching stations to handle mobile communication subscriber calls, call setting and release functions of the mobile station 11, etc. It performs various functions related to call processing and additional service. That is, the mobile telephone call processing process, handoff processing, system maintenance, and operation management functions.

2 is an exemplary cell configuration when a mobile station is located in a handoff area between a conventional base station (BTS) and a micro base station (mBS).

Since the micro base station 17 only serves to relay the processed CDMA signal based on the system reference time received from the multi-sector base station 16 from the GPS, the signal transmitted from the micro base station 17 is based on the system reference time. The time delay is generated by the transmission time in the optical fiber (or coaxial cable).

Therefore, conventionally, the mobile station 11 is located in the handoff area between the micro base stations 17 having different lengths of optical fibers, or in particular, the mobile station 11 is located in the handoff area between the micro base station 17 and the existing base station 12. When located, time lag occurred due to the optical fiber (or coaxial cable). In addition, when the length of the optical fiber (or coaxial cable) exceeds a certain range, it fails to synchronize with the pilots of the adjacent base stations, and thus handoff is not made and call drop occurs.

3 is an explanatory diagram showing a reason for a call disconnection in the conventional handoff region, in which "3a" is a mobile station reference time and "3b" is a pilot pseudo noise of a micro base station received in a neighbor list message. Position of the offset (Pilot_PN_Offset), "3c" is the search window size (SRCH_WIN_N: Search Window Size) received from the System Parameter Message, and "3d" is the time-delay caused by the fiber transmission time. Each of the pilot signals (Pilot Signal) of the actual micro base station taking into account the position. Here, the delay due to the distance on the air and the delay by other elements are not considered.

Referring to FIG. 3, assuming that the delay in the optical fiber is 5 μsec per km and the length of the optical fiber is 10 km (61.5 chip delay), the pilot intention of the micro base station received in the neighbor base station list message is shown. The position (3b) of the noise offset (Pilot_PN_Offset) is `60 (= 3840Chip) ', the search window size (SRCH_WIN_N) (3c) received in the system parameter message is` 7 (= 40Chip)', The position (3d) of the pilot signal of the actual micro base station considering the time-delay caused by the transmission time is '60 + time-delay (= 3840 + 62Chip = 3902Chip) '. .

When the mobile station 11 is in the service area of the existing base station 12 and comes to the handoff area with the micro base station 17, the mobile station 11 receives the micro base station received in the neighbor list message (Neighbor List Message). Based on the pilot pseudo-noise offset (Pilot_PN_Offset) of 17), the pilot signal of the micro base station 17 is found and synchronized within the search window size SRCH_WIN_N received in the system parameter message.

However, the pilot signal of the micro base station 17 is actually located outside the area of the search window size (SRCH_WIN_N) 3c due to the time delay caused by the optical fiber, so that the mobile station 11 fails to find the pilot signal. Failure will result in a call break.

On the other hand, the same phenomenon occurs when the mobile station 11 is in the service area of the micro base station 17 and then enters the handoff area with the existing base station 12. In this case, however, the position of the actual pilot signal of the existing base station 12 comes in front of the search window size (SRCH_WIN_N) 3c (ie, left).

4 is a structural diagram of a database in a conventional cellular mobile communication system.

As shown in FIG. 4, the existing base station BTS_A processes the transmission signal using the pilot pseudo noise offset (Pilot_PN_Offset) parameter of the sector data type (St_sector_data_type) item of the database, and the neighbor base station list message data type for handoff. Has a pilot pseudo noise offset of adjacent base stations (such as BTS_B) as a parameter.

If the mobile station 11 is in the service area of the existing base station BTS_A and enters the handoff area with the neighboring base station BTS_B, the mobile station 11 receives the neighboring base station BTS_B received from the neighbor base station list message. Handoff is performed in synchronization with the pilot signal of the neighboring base station BTS_B using the pilot pseudo noise offset.

As described above, in the CDMA micro-cellular mobile communication system, a transmission signal is generated by the multi-sector base station 16 and transmitted to the micro base station 17 through an optical fiber.

Therefore, conventionally, when the mobile station 11 moves the service area between the micro base stations 17 or between the micro base station 17 and the existing base station 12, due to the time delay of the optical fiber, the pilot signal of the micro base station 17 as a result. There was a problem in that the mobile station 11 failed to synchronize with the pilot signal in the handoff region and thus failed in handoff and a call break occurred.

In order to solve the above problems, the present invention sets a pilot pseudo noise offset (Compensated_Pilot_PN_Offset) parameter that is compensated by changing a database in a mobile communication system, and with reference to these parameters, a pilot due to time delay of a transmission medium. An object of the present invention is to provide a pilot signal delay compensation method for smoothly performing handoff without disconnection by compensating for signal delay.

1 is a diagram illustrating a mixed operation configuration of an existing cellular mobile communication system and a micro cellular mobile communication system of a general code division multiple access (CDMA) scheme.

2 is an exemplary cell configuration when a mobile station is located in a handoff area between a conventional base station (BTS) and a micro base station (mBS).

3 is an explanatory diagram showing a reason for a call disconnection in the conventional handoff region.

4 is a structural diagram of a database in a conventional cellular mobile communication system.

5A is an exemplary view illustrating a database structure of a micro cellular mobile communication system according to the present invention.

Figure 5b is another exemplary embodiment showing a database structure of a micro-cellular mobile communication system according to the present invention.

6 is an explanatory diagram for determining a compensated pilot pseudonoise offset according to the present invention.

7 is a flowchart illustrating a pilot signal delay compensation method according to the present invention.

8 is a flowchart illustrating an embodiment of a database change determination process according to the present invention.

* Explanation of symbols for the main parts of the drawings

11: Mobile Station (MS)

12: Base station transceiver subsystem (BTS)

13: control station (BSC: Base Station Controller)

14 Exchange Center (MSC: Mobile Switching Center)

15: Station (BSM: Base Station Manager)

16: Multi-Sector BTS

17: micro base station (mBS)

In order to achieve the above object, the present invention provides a pilot signal delay compensation method applied to a mobile communication system, comprising: a first compensated pilot pseudo compensation for correcting a time delay of a pilot signal according to a time delay caused by a transmission medium by changing a database; A first step of setting a noise offset (Compensated_Pilot_PN_Offset); And when transmitting a transmission signal from the multisector base station to the micro base station, by processing the transmission signal using the modified database and the first compensated pilot pseudo noise offset parameter in the channel element of the multisector base station, And a second step of compensating the time delay and thereby compensating the time delay of the pilot signal.

In addition, the present invention provides a second compensated pilot pseudo noise offset which automatically measures and calculates a time delay caused by the transmission medium in the multi-sector base station when the transmission signal is processed, initialized, or periodically requested by a user. Comparing a first compensated pilot pseudonoise offset and changing the database according to the comparison result; And a fourth step of notifying the channel element, the control station and the operating station of the change of the database.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

5A is an exemplary diagram illustrating a database structure of a microcellular mobile communication system according to the present invention.

As shown in FIG. 5A, the present invention provides an existing pilot for processing a forward link signal belonging to the micro base station 17 in a channel element of a digital unit of the multisector base station 16. Instead of using a pseudo noise offset (Pilot_PN_Offset), a value compensated for the time delay caused by the optical fiber, that is, a compensated pilot pseudo noise offset (Compensated_Pilot_PN_Offset = Pilot_PN_Offset-Optical Fiber Delay) is used.

In addition, the present invention uses the original pilot pseudonoise offset that does not compensate for the time delay in the pilot_noise_offset parameter of the neighbor base station list message of the neighboring micro base station.

In conclusion, in the micro cellular mobile communication system, a unique pilot pseudo noise offset (Pilot_PN) is used to distinguish the micro base station 17. The present invention uses the database of FIG. Instead of giving the same value to the pilot pseudo-noise offset of the neighbor base station list message of the neighboring base station, the channel element is created and assigned a compensated pilot pseudo-noise offset (Compensated_Pilot_PN_Offset) compensated for the optical fiber time delay by using the database of FIG. 5A. The element is used when processing a transmission signal belonging to the micro base station 17, and the original uncompensated pilot pseudo noise offset is allocated to a parameter of a neighbor base station list message of a neighboring micro base station.

Accordingly, the present invention conceptually uses a method of adjusting signal transmission time by compensating for time delay when processing a transmission signal in a channel element.

5B is another exemplary view illustrating a database structure of a micro cellular mobile communication system according to the present invention.

As shown in FIG. 5B, when the multi-sector base station 16 gives a pilot pseudo noise offset (Pilot_PN_Offset) and an optical fiber delay parameter related to the micro base station 17 as a channel element, The compensated pilot pseudonoise offset can also be calculated and used to process the transmitted signal belonging to the micro base station.

FIG. 6 is an explanatory diagram for determining a compensated pilot pseudonoise offset according to the present invention, in which "6a" is a reference time (ie, GPS reference time) of the multi-sector base station 16, and "6b" is shown in FIG. Uncompensated pilot pseudonoise offset (ie, pilot pseudonoise offset of the micro base station 17 used in the neighbor list message of the neighboring base station), " 6c " 6d " represent the compensated pilot pseudonoise offsets 6b-6c used when processing the transmission signal belonging to the micro base station 17 in the channel element of the multisector base station 16, respectively.

As shown in Fig. 6, when the mobile station 11 enters the handoff area between the existing base station 12 and the micro base station 17, the transmission signal from the multi-sector base station 16 to which the micro base station 17 belongs is located. When using the pseudo pseudo noise offset that does not compensate for the time delay due to the optical fiber, the handoff fails after the handoff fails as shown in FIG. 3, but the compensated pilot pseudo noise offset that compensates for the time delay due to the optical fiber is generated. In this case, the pilot signal is present at the position 6b expected by the mobile station, that is, at the position of the pilot pseudo noise offset of the micro base station 17 received in the neighbor base station list message. Synchronization is achieved so that handoff is successful without disconnection.

7 is a flowchart illustrating an embodiment of a pilot signal delay compensation method according to the present invention.

In the present invention, the multi-sector base station 16 transmits when the mobile station 11 moves the service area between the micro base stations 17 or between the micro base station 17 and the existing base station 12 in the CDMA micro cellular mobile communication system. A pilot pseudo noise offset (Compensated_Pilot_PN_Offset) is compensated by changing a database to compensate for delay in the pilot signal of the micro base station 17 due to the time delay that occurs as a result of the time delay that occurs. ) The new compensated pilot pseudo-noise offset and the existing compensated pilot are calculated by automatically measuring the time delay caused by the optical fiber transmission in the multi-sector base station 16 by smoothly performing the handoff without the call disconnection. Compare pseudonoise offsets to determine whether to alter the database As such, the optical fiber time delay is automatically compensated at the operator's request or periodically.

As shown in FIG. 7, in the pilot signal delay compensation method according to the present invention, first, the micro base station 17 is physically connected and initialized to the multi-sector base station 16 through an optical fiber (701).

Then, after measuring the optical fiber time delay to the micro base station 17 by using the time delay measurement algorithm in which the multi-sector base station 16 is embedded (702), in addition to the measured value, the time delay value of the amplifier element is considered. To determine the compensated pilot pseudo noise offset (703).

Next, it is determined whether to change the database of the multi-sector base station 16 (704), and the changed content is notified to the channel element (CE) of the embedded digital unit when the database is changed (705). Further, the control station 13 is notified of the changed contents (706).

Subsequently, after the notified control station 13 modifies the database in the control station 13 (707), it notifies the operating station 15 of the modified contents (708).

Thereafter, after receiving the notification, the operator station 15 modifies the database of the operator station 15 (709), and outputs the result to the operator as necessary (710).

As described above, the pilot signal delay compensation method according to the present invention uses the time delay measurement algorithm in which the multi-sector base station 16 is built in or periodically by the operator's request. In the process of measuring 702, the process of outputting the result to the operator 710 may be performed as necessary.

FIG. 8 is a detailed flowchart illustrating a database change determination process according to the present invention, and the database change determination process 704 in the multi-sector base station 16 when the database is changed periodically or at the request of the operator of FIG. 7. ) Is a detailed flowchart.

As shown in Fig. 8, the database change determination process 704 according to the present invention is first performed by the operator in the multi-sector base station 16 or periodically calculated by the operator or newly calculated compensated pilot with the optical fiber time delay value. If the pseudonoise offset is received, the difference between the new compensated pilot pseudonoise offset and the existing compensated pilot pseudonoise offset is calculated (801) and analyzed whether the difference is greater than the threshold (802).

As a result of the analysis, if the difference between the newly compensated pilot pseudonoise offset and the existing compensated pilot pseudonoise offset is greater than the threshold, the database is changed (803). If the difference is less than or equal to, the database is not changed (804).

The pilot signal delay compensation method according to the preferred embodiment of the present invention as described above can be similarly applied to not only an optical fiber transmission medium but also a coaxial cable or a microwave transmission medium. It is self-evident.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention compensates the time delay caused by the optical fiber transmission of a transmission signal in a CDMA micro cellular mobile communication system by adding an appropriate parameter through a change of the database, so that the mobile station is existing between the micro base station or the micro base station. Even when the service area is moved between base stations, handoff is smoothly performed without disconnection, thereby improving call quality. In addition, the present invention has the effect of improving the reliability and efficient operation of the system by automatically compensating the time delay due to optical fiber transmission periodically or at the request of the operator.

Claims (7)

In the pilot signal delay compensation method applied to a mobile communication system, A first step of changing a database to set a first compensated pilot pseudo noise offset (Compensated_Pilot_PN_Offset) that compensates for a time delay of a pilot signal due to a time delay due to a transmission medium; And When transmitting a transmission signal from a multisector base station to a micro base station, time due to the transmission medium by processing the transmission signal using the modified database and the first compensated pilot pseudo noise offset parameter in the channel element of the multisector base station. A second step of compensating for the delay and thereby compensating for the time delay of the pilot signal Pilot signal delay compensation method comprising a. The method of claim 1, A second compensated pilot pseudonoise offset and the first compensated pilot that automatically measure and calculate the time delay due to the transmission medium at the multisector base station upon processing, initialization, or user request or periodically Comparing a pseudonoise offset and changing the database according to the comparison result; And A fourth step of notifying the channel element, the control station and the operating station of the change of the database. Pilot signal delay compensation method further comprises. The method of claim 2, The third step, After measuring the time delay of the transmission medium from the multi-sector base station to the micro base station, determining the second compensated pilot pseudo noise offset in consideration of the time delay value of an amplifier element or the like in addition to the measured value; ; A sixth step of calculating, by the multisector base station, a difference between the second compensated pilot pseudonoise offset and the first compensated pilot pseudonoise offset and analyzing whether the difference is greater than a predetermined threshold; And As a result of the analysis in the sixth step, when the difference between the second compensated pilot pseudonoise offset and the first compensated pilot pseudonoise offset is greater than a threshold, the database is changed; step Pilot signal delay compensation method comprising a. The method of claim 3, wherein The fourth step, An eighth step of notifying the channel element embedded in the multi-sector base station when the database is changed; A ninth step of the multisector base station notifying the control station of the change of the database, and after the control station changes the database in the control station, notifying the operating station of the changed content; And A tenth step in which the operating station changes the database in the operating station and outputs the result to the operator as necessary. Pilot signal delay compensation method comprising a. The method according to any one of claims 1 to 4, Each of the compensated pilot pseudo noise offsets is Pilot signal delay compensation method characterized in that the value of the conventional pilot pseudo-noise offset minus the time delay of the transmission medium. The method of claim 5, Each transmission medium, A pilot signal delay compensation method comprising an optical fiber, a coaxial cable, and a microwave. On your computer, A first function of changing a database to set a first compensated pilot pseudo noise offset (Compensated_Pilot_PN_Offset) that compensates for a time delay of a pilot signal due to a time delay due to a transmission medium; And When transmitting a transmission signal from a multisector base station to a micro base station, time due to the transmission medium by processing the transmission signal using the modified database and the first compensated pilot pseudo noise offset parameter in the channel element of the multisector base station. A second function of compensating for the delay and thereby compensating for the time delay of the pilot signal A computer-readable recording medium having recorded thereon a program for realizing this.