KR20000008898A - Apparatus for combining symbols of a mobile station and method of utilizing an asynchronous mode and a synchronous mode between base stations using the apparatus - Google Patents

Abstract

PURPOSE: An apparatus which combines the plurality of symbols considering both a difference between transmission delays and an error of transmission start time and controls an asynchronous mode base station and a synchronous mode base station to facilitate convenience in a practice and a cell design and a method thereof are provided. CONSTITUTION: An apparatus for combining a plurality of symbols of a mobile station includes; searching means (901) for searching multiple routs when a base band signal from a base station is received to determine one among the multiple routs; plurality of demodulation means (902 through 905) for demodulating symbols of the base band signal on the multiple routs determined by the searching means; rout selecting means (906) for selecting each rout of symbols, each of which is demodulated by the plurality of demodulation means; first symbol combining means (908) for delaying the demodulated symbols for a transmission delay time period and for combining the delayed symbols at every routs; plurality of buffering means (909, 910) for compensating both a difference between transmission delays and an error of transmission start time; and second combining means (908) for combining the symbols from the plurality of buffering means. According to the apparatus, by combining the plurality of symbols considering both a difference between transmission delays and an error of transmission start time and controlling base station with an asynchronous mode and a synchronous mode, the cells can be more effectively designed.

Description

Symbol combining device of mobile station and mixed operation mode between asynchronous mode and asynchronous mode using base station

The present invention combines symbols during handover of a mobile station in a mobile communication system and the like, which is convenient for the installation and operation of a synchronous mode base station, a base station, an underground space, and a microcell and picocell in a building. The present invention relates to a symbol combining apparatus of a mobile station for improving the convenience of cell design and operation by operating a mixed base station, and a method of operating a mixed mode and asynchronous mode between base stations using the same.

In a conventional code division multiple access (CDMA) mobile communication system, a synchronous method has been commonly used between base stations, and a synchronous method or an asynchronous method is independently used for a next generation mobile communication system. Is being applied. That is, in the CDMA mobile communication system, a synchronous method using absolute time information or an asynchronous method using no absolute information has been used separately.

Therefore, in order to increase convenience in cell design and operation of mobile communication system and reduce installation cost of microcells and picocells, it is advantageous to install and operate microcells and picocells in underground spaces and buildings in a synchronous manner. There is a need for a method capable of mixing asynchronous methods.

In the conventional synchronous mode base station using only the synchronous method individually, since the transmission start time point is the same, the mobile station can combine the data considering only the difference in the transmission delay, but the mixed mode in which the synchronous mode and the asynchronous mode between base stations are mixed and operated. In the base station, a symbol combining apparatus capable of combining symbols in consideration of an error in transmission start time is essentially required.

The present invention devised to meet the demand as described above, in the mobile communication system, such as adding a symbol in the handover of the mobile station to combine a plurality of symbols in consideration of the difference in transmission delay and the transmission start time, and the synchronization mode base station It is an object of the present invention to provide a symbol combining device of a mobile station and a method of operating a mixed mode and asynchronous mode between base stations using the same to increase the convenience in cell design and operation by mixing and operating asynchronous mode base stations.

1 is an explanatory diagram showing operation mode determination and mode switching of a mobile station according to the present invention;

2 is a flowchart illustrating an embodiment of a method for mixing and operating asynchronous mode and asynchronous mode between base stations according to the present invention.

3 is a cell structure diagram of a mobile communication system which uses a synchronization mode and an asynchronous mode between base stations used in the present invention.

4 is an explanatory diagram showing a relationship between a cluster pilot and a cell pilot used in the present invention.

5 is a diagram of a forward channel structure in the case of using a cluster pilot and a cell pilot used in the present invention.

6 is a transmission frame structure diagram of a cluster pilot and a cell pilot used in the present invention.

7 is a flowchart of an embodiment of a handover processing method according to the present invention;

8 is an explanatory diagram showing frame time alignment in a mobile station during handover used in the present invention;

9 is a structural diagram of an embodiment of a symbol combining apparatus of a mobile station in handover according to the present invention;

* Explanation of symbols for the main parts of the drawings

11: Synchronous mode 12: Asynchronous mode

901: Searchers 902 to 905: Finger

906: path selector 907 908 911: symbol combiner

909,910 buffer

The apparatus of the present invention for achieving the above object comprises: search means for determining a path by receiving a baseband signal from a base station to search for multipath; A plurality of demodulation means for demodulating a symbol of a baseband signal in a multipath designated by said search means; Path selection means for selecting a path of each symbol demodulated by the plurality of demodulation means; A plurality of first symbol combining means for delaying a demodulated symbol by a difference in transmission delay and combining the demodulated symbols for each path selected by the path selecting means; A plurality of buffering means for receiving the outputs of the plurality of symbol combining means and compensating for the error of the symbol transmission start time and the transmission delay between the base stations; And second symbol combining means for combining each symbol whose error is compensated for in the plurality of buffering means.

The method of the present invention includes an inter-base station operating method applied to a wireless communication system, comprising: a first step of analyzing a mode assigned to a mobile station and searching for a pilot of a mode base station assigned to the mobile station; A second step of communicating with a designated base station upon successful pilot acquisition as a result of the search of the first step; And a third step of communicating with the switched base station by switching the mode when the pilot acquisition fails, as a result of the search of the first step.

The method further includes a fourth step of switching the communicating base station from the handover area to the same mode base station or another mode base station.

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

1 is an explanatory diagram showing operation mode determination and mode switching of a mobile station according to the present invention.

In the synchronous mode 11 and the asynchronous mode 12 mixed operation scheme according to the preferred embodiment of the present invention, the synchronous mode 11 base station and the asynchronous mode 12 base station are mixed and operated. It works in a synchronous way. That is, all base stations operate in a synchronized state by obtaining time information from an absolute time information source such as a global positioning system (GPS).

In the case of using a synchronization method between base stations, each base station uses the same pseudo noise (PN) sequence and is distinguished by different phase offsets.

The synchronous mode (11) base station has many advantages such as simply acquiring a pilot or easily aligning data frames during handover, but there may be disadvantages in the installation cost and failure or use of the GPS receiver, and underground space. There may be an area where reception is not possible, such as.

Therefore, it should be possible to operate by switching from the synchronous mode 11 base station to the asynchronous mode 12 base station in an area or a situation where reception is impossible.

In order to operate a synchronous and asynchronous method between base stations, the mode of the base station and the base station controller must be controlled by the exchange. In addition, the mobile station must be capable of finding pilots in the synchronous mode 11 base station and in the asynchronous mode 12 base station.

Referring to FIG. 1, a method of mixing and operating synchronous and asynchronous methods between base stations operates in a mode of a base station when the mobile station acquires a pilot of the base station, and a mode currently in operation can switch modes during a call in a handover region. Do.

Looking at this in detail.

First, when the mobile station is powered on, the pilot signal of the synchronous mode 11 base station is searched for.

If the pilot signal of the base station in the synchronous mode 11 is not obtained, the pilot signal of the base station in the asynchronous mode 12 is searched. If the pilot signal of the base station in the synchronous mode 11 is acquired, the base station communicates with the base station in the synchronous mode 11.

On the other hand, if the pilot signal of the asynchronous mode 12 base station is not obtained, the pilot signal of the synchronous mode 11 base station is searched, and if the pilot signal of the asynchronous mode 12 base station is acquired, it communicates with the asynchronous mode 12 base station.

FIG. 2 is a flowchart illustrating an embodiment of a mixed operation between a base station and an asynchronous mode according to the present invention, and illustrates an operation procedure of a mobile station when the base station 11 is mixed with the base station 12 in asynchronous mode. .

First, when the mobile station is powered on (201), the mode assigned to the mobile station is analyzed (202).

As a result of the analysis, if the designated mode is the synchronization mode 11, the synchronization mode 11 searches for a pilot signal of the base station (203) and determines whether a pilot signal has been obtained (204).

As a result of the determination, when the pilot signal of the base station in synchronization mode 11 is obtained, the base station communicates with the base station in synchronization mode 11 (205).

Then, the active mode can be switched during the call in the handover area, so it is checked in real time whether handover is required (206). If no handover is necessary, the same mode of synchronization (11) continues to communicate with the base station (205). If handover is needed, it is analyzed whether to handover to another synchronous mode 11 base station or to asynchronous mode 12 base station (207).

As a result of the analysis, if there is a need to handover to another synchronous mode 11 base station, handover to another synchronous mode 11 base station (208), and if it is necessary to handover to a base station, asynchronous mode 12 After handing over to the base station (209), it communicates with the handed over base station (215).

If the mode designated to the mobile station is asynchronous mode 12 or the synchronous mode 11 does not acquire the pilot signal of the base station, the asynchronous mode 12 searches for the pilot signal of the base station 210 to check whether the pilot signal is obtained ( 211).

As a result of the check, when the pilot signal of the asynchronous mode 12 base station is acquired, the asynchronous mode 12 communicates with the base station (212). If the pilot signal of the asynchronous mode 12 base station is not obtained, the mode designated to the mobile station is analyzed (202). ).

Next, since the mode can be switched even during a call in the handover area in real time (213), if the handover is not necessary, it continuously communicates with the same asynchronous mode (11) to the base station (212). If handover is needed, it is determined whether to handover to the synchronous mode 11 base station or to another asynchronous mode 12 base station (214).

As a result of the determination, if there is a need for handover to the synchronous mode 11 base station, the handover to the synchronous mode 11 base station is performed (208), and if it is necessary to handover to another asynchronous mode 12 base station, another asynchronous mode 12 is required. After handing over to the base station (209), it communicates with the handed over base station (215).

Fig. 3 is a cell structure diagram of a mobile communication system which uses a synchronization mode and an asynchronous mode between base stations used in the present invention, in which " 31 " is a microsynchronous mode base station, " 32 " Represents a synchronous mode base station.

Referring to FIG. 3, the synchronous mode 11 base station is distributed in the form of macrocells and microcells 31 and 33, and the asynchronous mode 12 base station is overlayed on the synchronous mode 11 cell, It exists as a cell 32 in some areas.

For example, the asynchronous mode 12 base station may be disposed in a subway or underground parking lot to easily provide a mobile communication service even in an area where a GPS signal does not reach. In addition, a private mobile communication network may be constructed by overlaying an asynchronous mode 12 base station on a cell in the synchronous mode 11 cell in an office or the like.

Looking at the channel structure for the asynchronous mode 12 between the base station for the mixed operation of the synchronous and asynchronous method as follows.

Since each cell of the asynchronous mode 12 is not distinguished by the PN sequence itself as in the synchronous mode 11, but is separated by the PN sequence itself, as in the synchronous mode 11, the base station in the synchronous mode 11 is a conventional method. In the asynchronous mode 12, since the base stations are divided into different codes, a long time is required to obtain a cell pilot.

Accordingly, a fast base station search method is required. In this embodiment, the base station search is performed using two pilot signals (ie, a cluster pilot and a cell pilot). The relationship between the cluster pilot and the cell pilot is illustrated in FIG. 4.

Referring to FIG. 4, the mobile station divides several base station PN codes (ie, cell pilots) into groups to form one cluster pilot for fast cell search when operating in the asynchronous mode 12. , Entire service area) consists of several cluster pilots.

Therefore, the pilot of each cell is composed of a cluster pilot and a cell pilot, so it can be known which cell of which cluster. The forward channel structure when using these two pilots is as shown in FIG.

FIG. 5 is a diagram of a forward channel structure using two pilots used in the present invention, and shows a forward channel structure for transmitting a pilot transmitted by a CDMA base station to a pilot channel for transmitting cluster information and a pilot channel for transmitting cell information.

Cluster pilots are distinguished by cluster pseudo-noise codes (C` <sub>I</sub> , C` _Q ), and cell pilots and remaining channels (ie, traffic) are distinguished by cell pseudo-noise codes (C _I , C _Q ).

The cluster pilot and the cell pilot use the same orthogonal code W ₀ , and the cell pilot and the remaining channels are distinguished by different orthogonal codes W _k , respectively. In this case, the structure of the frame transmitted by the cluster pilot and the cell pilot is as shown in FIG.

Referring to FIG. 6, the cluster pilot is a short period PN sequence, and the cell pilot is a long period PN sequence, and the starting point is aligned with the cluster pilot.

Therefore, the mobile station can first search for a cluster pilot having a short period and search only a cell pilot designated by the found cluster pilot in a short time by using the cluster pilot and the cell pilot aligned, thereby reducing the search time.

For example, a cluster pilot with a short period PN sequence may have a cycle of "2304 chips gold sequence," and a cell pilot with a long period of PN sequence may have a cycle pilot of 16 cycles. 36864 chips m sequence "(2304 x 16).

7 is a flowchart illustrating a handover processing method according to the present invention, and illustrates a handover processing procedure for a mixed mode in which a synchronous mode 11 and an asynchronous mode 12 are mixed.

In general, mobile communication systems provide multiple base stations in a service area due to problems such as frequency usage efficiency and power consumption, and provide services by dividing into sectors within the same base station. In this case, if the mobile station moves during a call, a handover function is required to constantly connect with a radio channel of another base station or another sector to maintain continuity of the call.

Therefore, even in this embodiment, when the mobile station is making a call in the synchronous mode 11 or the asynchronous mode 12, the mobile station should have the ability to handover to the same mode or another mode in order to maintain continuity of the call.

In the mixed mode, the handover from the synchronous mode 11 to the synchronous mode 11, the handover from the synchronous mode 11 to the asynchronous mode 12, the handover from the asynchronous mode 12 to the synchronous mode 11, or the like. There is a case of handover from the asynchronous mode 12 to the asynchronous mode 12.

Therefore, in order to accommodate handover for four modes at the mobile station, the originating base station must broadcast a neighbor list including the base stations in the synchronous mode 11 or the asynchronous mode 12.

The mobile station searches for a destination base station when the power of the originating base station is less than a predetermined upper threshold, and handover between modes is a base station of the same mode in which the handover between modes is greater than a predefined lower threshold. Find only when there is no. Here, the mobile station must be able to find other PN codes with different offsets in order to find the destination base station in another mode.

As described above, the handover is performed from the synchronous mode 11 to the asynchronous mode 12, the handover from the asynchronous mode 12 to the synchronous mode 11, or the asynchronous mode 12 from the asynchronous mode 12. In case of handover), there may be a large misalignment between the originating base station frame and the receiving base station frame.

Thus, in order to obtain a diversified handover gain, the mobile station must measure the misalignment of the frames and match the data frames received from the originating base station with the data frames received from the destination base station in the time axis (see FIG. 8 described later). For this purpose, the mobile station should have a buffer for storing data received from the originating base station and the terminating base station.

Looking at the handover process as described above in detail as follows.

First, in a call state between the mobile station and the originating base station (701), if the mobile station requests handover to the originating base station (702), the originating base station transmits a response message to the handover request to the mobile station (703).

Thereafter, when the receiving pilot channel is received from the destination base station to the mobile station (704), since frame originming is different between the originating base station and the destination base station, frame misalignment is measured by the mobile station (705).

Next, when the mobile station transmits the handover request and related information to the base station controller (706), the base station controller transmits the handover request and related information from the mobile station to the destination base station (707).

Subsequently, if the base station controller transmits the incoming base station information to the originating base station (708), the originating base station transmits the received terminating base station information to the mobile station (709). At this time, the mobile station searches for traffic and pilot to obtain a destination base station (710).

Thereafter, when the destination base station transmits the downlink to the mobile station (711), the mobile station is synchronized with the destination base station (712).

Next, uplinks are synchronized at the destination base station (713), and frames are combined at the mobile station (714).

Finally, in the data combination state in which the frames of the mobile station are aligned, the base station controller receives the data of the originating base station and the destination base station and selectively combines the best quality data (715).

8 is an explanatory diagram showing frame time alignment in a mobile station during handover used in the present invention, in which "a" represents an originating base station transmission frame (Origination BTS Frame Tx) and "b" represents a destination base station transmission frame (Destination). BTS Frame Tx), " c " denotes an Origination BTS Frame Rx in MS in a mobile station, " d " denotes a Destination BTS Frame Rx in MS, and " e " Frame alignment in MS states (i.e., combination data) are respectively shown.

Referring to FIG. 8, data symbols transmitted from base stations that are not synchronized with each other arrive at mobile stations with a time interval as much as a difference due to a transmission delay is added to different base station transmission start time differences.

Normal base stations with synchronization between base stations have the same transmission start time, so the mobile station considers only the difference in transmission delay and combines the data. However, when the synchronous and asynchronous methods are used in a mixed operation, the mobile station starts transmission to match the frame time. A symbol combining device capable of combining symbols in consideration of time error should be provided.

9 is a structural diagram of an embodiment of a symbol combining apparatus of a mobile station during handover according to the present invention, and shows a structure of a baseband signal processing unit of the mobile station.

The symbol combining apparatus of the mobile station according to the preferred embodiment of the present invention receives a baseband signal from the outside, and is a searcher 901 and a searcher 901 for determining a base station search, a multipath search of a base station, and a base station handover condition. First to fourth fingers 902 to 905 and demodulated symbols of the first to fourth fingers 902 to 905 for demodulating the symbols of the baseband signals in the multipath specified in the sub-paths. A path selector 906 for selecting a path, an originating base station symbol combiner 907 and a destination base station symbol combiner 908 for delaying and combining the demodulated symbols for each base station selected by the path selector 906 by a transmission delay difference. And the outputs of the originating base station symbol combiner 907 and the destination base station symbol combiner 908, the error of the symbol transmission start time and the transmission delay between the base stations. It includes first and second buffers (909 910) and the first and second buffers (909 910), symbol combiner 911 for combining each of the symbols, to which the error is compensated by the source and destination for a base station in a perishable.

The source base station symbol combiner 907 delays and combines the demodulated symbols for each source base station selected by the path selector 906 by the difference in transmission delay, and the destination base station symbol combiner 908 receives the call selected by the path selector 906. The demodulated symbols for each base station are delayed and combined by a difference in transmission delay.

The first buffer 909 receives the output of the originating base station symbol combiner 907 to compensate for the error of the symbol transmission start time and the transmission delay between the base stations for each originating base station, and the second buffer 910 is the destination base station symbol. The output of the combiner 908 is input to compensate for the error of the symbol transmission start time and the transmission delay between the base stations for each destination base station.

The mobile station performs handover from the synchronous mode 11 to the synchronous mode 11, from the synchronous mode 11 to the asynchronous mode 12, or according to the size of the first and second buffers 909 and 910. The handover to the synchronous mode 11 in 12) or the handover to the asynchronous mode 12 in the asynchronous mode 12 is possible.

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 has the effect of increasing the convenience of cell design and operation of the mobile communication system by reducing the installation cost of the microcell and picocell by operating the synchronous and asynchronous methods.

Claims (15)

Search means for receiving a baseband signal from a base station and searching for multipaths to determine a path; A plurality of demodulation means for demodulating a symbol of a baseband signal in a multipath designated by said search means; Path selection means for selecting a path of each symbol demodulated by the plurality of demodulation means; A plurality of first symbol combining means for delaying a demodulated symbol by a difference in transmission delay and combining the demodulated symbols for each path selected by the path selecting means; A plurality of buffering means for receiving the outputs of the plurality of symbol combining means and compensating for the error of the symbol transmission start time and the transmission delay between the base stations; And Second symbol combining means for combining each symbol whose error is compensated for in the plurality of buffering means; Symbol combining apparatus of the mobile station comprising a. The method of claim 1, The plurality of first symbol combining means, Source base station symbol combining means for delaying a demodulated symbol by a difference in transmission delay and combining the demodulated symbols for each source base station selected by the path selection means; And Incoming base station symbol combining means for delaying the demodulated symbol by the difference in transmission delay and combining each of the destination base stations selected by the path selection means. Symbol combining apparatus of the mobile station comprising a. The method of claim 2, The plurality of buffering means, First buffering means for receiving an output of the originating base station symbol combining means and compensating for an error in transmission start time and transmission delay between symbols between originating base stations; And Second buffering means for receiving an output of the destination base station symbol combining means and compensating for an error in a symbol transmission start time and a transmission delay between destination base stations; Symbol combining apparatus of the mobile station comprising a. The method according to any one of claims 1 to 3, The symbol combining device, And a plurality of symbols combined at the time of handover between the mixed mode base station in which the synchronous mode base station and the asynchronous mode base station are mixed and the mobile station. In the inter-base station operating method applied to a wireless communication system, Analyzing a mode assigned to the mobile station and searching for a pilot of a mode base station assigned to the mobile station; A second step of communicating with a designated base station upon successful pilot acquisition as a result of the search of the first step; And A third step of communicating with the switched base station by switching modes when pilot acquisition fails as a result of the search of the first step Mixed base station synchronous mode and asynchronous mode mixed operation method comprising a. The method of claim 5, A fourth step of switching the communication mode base station from the handover area to the same mode base station or another mode base station; Mixing operation method between the base station synchronous mode and asynchronous mode further comprising. The method of claim 6, The fourth step, A fifth step of checking whether switching of the communicating base station is necessary; A sixth step of continuing communication with the communicating base station if no mode change is necessary as a result of the inspection of the fifth step; And A seventh step of handover to the same mode base station or the other mode base station if a mode change is necessary as a result of the check in the fifth step Mixed base station synchronous mode and asynchronous mode mixed operation method comprising a. The method of claim 7, wherein The handover process of the seventh step, An eighth step in which the mobile station requests handover to the originating base station in a communication state between the mobile station and the originating base station; A ninth step of the originating base station transmitting a response message to the mobile station in response to a handover request; A tenth step of, when the receiving base station receives a reception pilot channel, the mobile station measures frame misalignment because the originating base station and the destination base station have different frame timings; An eleventh step of the mobile station transmitting a handover request and related information to the destination base station through a base station controller; A twelfth step of the base station controller transmitting the destination base station information to the mobile station through the originating base station; A thirteenth step, wherein the mobile station searches for traffic and pilot to obtain the destination base station; A fourteenth step of synchronizing the mobile station with the destination base station when the destination base station transmits a downlink to the mobile station; A fifteenth step of synchronizing an uplink by the called base station; The sixteenth step of the mobile station aligning frames to combine data; And A seventeenth step in which the base station controller receives data of the originating base station and the destination base station and selectively combines data having the largest pilot strength; Mixed base station synchronous mode and asynchronous mode mixed operation method comprising a. The method according to any one of claims 5 to 8, The mode is, Method for operating a mixed mode and asynchronous mode between the base station, characterized in that the synchronous mode (Synchronous Mode) or asynchronous mode (Asynchronous Mode). The method of claim 9, The second step, An eighteenth step of analyzing a mode assigned to the mobile station; A nineteenth step of searching for a pilot signal of a synchronous mode base station if the designated mode is the synchronous mode as a result of the analysis in the eighteenth step; A twentieth step of communicating with the synchronous mode base station when the pilot signal acquisition of the synchronous mode base station is successful; A twenty-first step of searching for a pilot signal of an asynchronous mode base station if the designated mode is the asynchronous mode as a result of the analysis of the eighteenth step; And A twenty-second step of communicating with the asynchronous mode base station when the pilot signal acquisition of the asynchronous mode base station is successful; Mixed base station synchronous mode and asynchronous mode mixed operation method comprising a. The method of claim 10, The third step, A twenty-third step of communicating with the asynchronous mode base station by switching modes when the pilot signal acquisition failure of the synchronous mode base station is failed as a result of the search of the nineteenth step; And A twenty-fourth step of communicating with the synchronous mode base station by switching modes when a pilot signal acquisition failure of the asynchronous mode base station is not obtained; Mixed base station synchronous mode and asynchronous mode mixed operation method comprising a. The method of claim 11, Each cell of the asynchronous mode base station, PN (Pseudo Noise) The base station between the synchronous mode and asynchronous mode mixed operating method, characterized in that distinguished by itself. The method of claim 11, Each pilot is Inter-base station synchronization, characterized in that the cluster pilot (PN) sequence of short periods and the cell pilot (Sell Pilot) aligned with the cluster pilot starting point in the long period of the pseudo noise (PN) sequence Mixed mode and asynchronous mode of operation. The method of claim 13, Each mobile station, A method of combining synchronous mode and asynchronous mode between base stations, characterized in that a symbol combiner capable of combining symbols by considering not only an error of transmission delay but also an error of transmission start time in order to match a frame time. The method of claim 14, Each mobile station, When the power of the originating base station is less than a predefined upper threshold, the called base station is found, and only when there is no called base station of the same mode that is larger than a predefined lower threshold when handover between modes. And searching for different pseudonoise (PN) codes having different offsets to find the destination base station in the other mode.