KR20090116545A - Method for scanning handover signaling in hybrid indoor/outdoor wibro system and indoor cell sorting method in its - Google Patents

Abstract

PURPOSE: A base station scanning method for the handover in a portable Internet system consisting indoor/outdoor base stations and a method for classifying indoor base stations are provided to reduce the overhead and unnecessary power consumption of a terminal. CONSTITUTION: After receiving neighboring outdoor base station related information from the current outdoor base station, the scanning for outdoor base stations is performed(602). A Class A personal indoor base station is scanned(605). If the scanning fails, a common indoor base station is searched(606,607). If the search fails, a Class B personal indoor base station is searched(608,609). If the scanning fails, other outdoor base stations are scaned when necessary(610,611).

Description

A method for scanning a base station for handover and a method for classifying an indoor base station in a portable Internet system composed of indoor / outdoor base stations {method for scanning handover signaling in hybrid indoor / outdoor wibro system and indoor cell sorting method in its}

The present invention relates to a method for scanning a base station for handover, a method for classifying an indoor base station for a handover in a portable Internet system composed of indoor / outdoor base stations, and a computer-readable recording medium recording a program for implementing the methods. More specifically, in a portable Internet system in which indoor / outdoor base stations exist, the indoor base stations are classified according to characteristics (for example, the frequency of use of the user), and a terminal moving outdoors from indoors to indoor indoor base stations is used. A base station scanning method and a method of classifying an indoor base station therefor, which can efficiently scan an appropriate surrounding indoor base station when attempting a handover, and a computer-readable recording medium recording a program for implementing the methods. It is about.

In particular, the present invention provides a mobile Internet environment in which a plurality of indoor base stations exist in an outdoor base station when a terminal belonging to the outdoor base station performs a handover to an indoor base station (that is, in a mobile internet environment in which indoor / outdoor base stations exist). When the UE located in the area of the outdoor base station performs handover to the indoor base station as long as it exists in the outdoor base station, the neighboring indoor base station is efficiently scanned (the indoor base station is classified and scanned according to the classification characteristics). We search for the appropriate indoor base station among the numerous indoor base stations present in the cell, minimizing power consumption and scanning latency.

Wireless Broadband (WiBro) systems provide Internet services in a wireless environment, such as Wi-Fi, and provide broadband Internet access, such as high-speed Internet services. In terms of transmission speed, mobility, cell radius, etc., it can supplement the advantages and disadvantages in terms of transmission distance and transmission speed of current mobile communication and wireless LAN. It is a representative mobile communication technology.

The portable Internet system can obtain or utilize various information and contents by accessing the Internet at a high speed transmission speed anytime, anywhere using a portable wireless terminal (portable Internet terminal). Accordingly, like many existing cellular mobile communication systems, the portable Internet system supports handover to ensure mobility of mobile terminals.

However, in the portable Internet system, various kinds of base stations are located at the same time. These various types of base stations can be broadly divided into indoor base stations and outdoor base stations, which are divided into cell coverage perspectives and main installation sites and applications.

In general, handover includes a communication path (base station ↔ terminal communication path) so that a mobile terminal can maintain communication when entering a cell area of another base station out of the cell area of a serving base station currently communicating. This refers to changing to a target base station located in the movement direction of the terminal.

The portable Internet should be able to continuously provide QoS-guaranteed services while moving. To this end, the handover technology used in the mobile Internet uses a hard handover technology that breaks an existing call line and connects to a new base station, but recently, two or more base stations are used for reliability. Soft handover technology that can support high handover is being considered. The handover technique may be divided into a network topology acquisition procedure for periodically measuring parameter values required for handover determination and a procedure for determining and performing a handover.

Handover is a procedure for receiving a service from a neighboring base station when the terminal moves from the current base station area to the neighboring base station area in the mobile communication system.

Referring to the handover procedure with reference to FIG. 1, once the need for handover is determined through handover triggering, the mobile terminal receives scanning information for handover (101) and selects an appropriate neighbor base station for handover. A base station scanning process for searching is performed (102). In this case, if the found base station exists, a handover is requested to the base station (target base station) and handover is performed (103 to 105).

In detail, the serving base station periodically broadcasts a message informing of neighbor BS information for handover of a mobile terminal. In this case, when the terminal receives a message periodically advertised from the base station (serving base station) to which it belongs, it can obtain the ID, QoS parameters and channel information of neighboring base stations and use this information to perform a faster handover later. have.

Thereafter, the terminal scans neighbor base stations as needed, and thus, the terminal can know the signal strength of the neighbor base stations. In this case, the scanning operation is performed by the terminal transmits a message requesting Scanning Interval and Iteration to the serving base station, and is assigned through a response message. During the Scanning Interval, the UE searches whether several neighboring base stations are suitable for handover.

That is, the terminal may manage the list of candidate base stations to perform a handover by obtaining an ID list of neighbor base stations through a message periodically broadcasted by the serving base station and selecting an appropriate base station based on real-time link information acquired through scanning. .

However, the handover may be initiated by the terminal or may be performed by the base station.

First, referring to a case in which the UE starts handover, after the scanning process is finished, the UE transmits a handover request message to the serving base station to start the handover, wherein the serving base station periodically broadcasts the handover request message. Carrier to Interference and Noise Ratio (CINR) values of neighboring base stations received through the message are included.

When the handover request is received from the terminal, the serving base station informs the terminal information through a message indicating that the terminal performs handover to the candidate base stations recommended by the terminal through a backbone network, and receives a response message from the candidate base station.

After receiving the response, the serving base station checks the recommendable handover target base station, and transmits the recommended BS list in the handover response message to the terminal.

Thereafter, the terminal determines a final handover target base station among the target base stations recommended by the serving base station, and sends a handover execution message to the serving base station to finally notify the handover.

Here, the terminal determines the optimal target base station by comparing the signal strength and QoS parameters of the neighbor base stations obtained previously. That is, the terminal compares the quality of service and signal strength provided from the serving base station and transmits a list of base stations capable of handover to the serving base station in a handover request message, and the serving base station transmits a list of recommended base stations (candidate candidates). Base station) in the handover response message and returns. At this time, the serving base station may notify the candidate base stations (one of which becomes the target base station) through the backbone network and transmit the session and configuration information of the terminal in advance to shorten the time for performing the handover later. [ Handover preparation process]

After that, when the portable Internet terminal receives the handover response message and determines the target base station, the portable internet terminal sends a handover execution message to the serving base station to finally notify the handover and immediately executes the handover. [ Handover Execution Process]

Meanwhile, in the handover preparation process, the serving base station may first start the handover process by transmitting a handover request message to the terminal. That is, when the serving base station starts handover, a handover request message is transmitted to the terminal. The handover request message includes a list (recommended base station list) recommended by the serving base station, and the terminal serves the recommended base station. The handover is notified by evaluating the information obtained through the message periodically broadcasted by the base station and the information through the base station discovery and transmitting a handover execution message to the serving base station.

In the handover execution process, the serving base station receiving the handover execution message disconnects from the terminal and stops the service after the Resource Retain Time. At this time, since the UE can no longer send and receive packets through the serving base station from the time of transmitting the handover execution message, the UE quickly moves to a new network and acquires a transmission parameter and a network re-entry procedure. (Ranging) process, basic capability negotiation process, terminal authentication and key exchange process, registration process, connection establishment process, IP address allocation process, etc.]. In this case, if the target base station has already received the terminal information on the performance capability and authentication from the serving base station, the terminal may shorten the handover process by omitting the corresponding process during the network entry process. If the network entry process is successfully completed, the target base station starts the service to the terminal.

In the above, the scanning process 102 is the most important part of the overall handover process, as identification of the neighbor base station is essential for handover. However, the scanning process 102 takes a lot of time and power to determine the presence of the neighboring base station. Therefore, depending on how efficiently scanning is performed, handover related system performance such as handover delay is greatly affected.

Most existing mobile communication systems receive information from neighbor base stations for scanning prior to scanning. Since this information broadcasts information of its neighboring base stations at regular intervals, the mobile station can always receive this information.

The scanning process 102 of each existing system is summarized as follows.

A. IS-95 CDMA

A handover service provided in a direct sequence code division multiple access (DS-CDMA) mobile communication system implemented based on the International Standard-95 (IS-95) standard will be described.

In general, a code division multiple access mobile communication system divides a service area into cells and reuses used frequencies in order to efficiently use frequency resources.

As such, since the service area is divided into cellular compartments, when the mobile station (MS) moves to another cell, it starts communication with the base station (BS) that manages the new corresponding cell, which is called a "handover". do.

Handover services provided in the DS-CDMA mobile communication system based on the IS-95 standard include a "soft handover" method and a "hard handover" method.

Hard handover is a method in which a communication channel established between a current base station and a mobile terminal is changed to a channel between a neighboring base station and a mobile terminal in an instant. The call is disconnected for a short time, and soft handover is performed by two or more mobile terminals. It is a method of changing the service area without interruption of a call by maintaining a communication channel with a base station for a certain time.

For example, the soft handover method refers to a mobile terminal receiving a call channel from two base stations simultaneously while the mobile terminal is in service between a serving base station and a neighboring base station. The hard handover method is used in a serving base station and a neighboring base station. When the frequencies are different, the current frequency is disconnected and replaced with a new frequency supported by the neighboring base station to continue the call.

The soft handover procedure defined in IS-95, which is a standard of the CDMA mobile communication system, can be described with reference to FIG.

In the IS-95 system, as shown in FIG. 2, a signal of a base station or another sector belonging to the switching center is periodically checked through the rake receiver. Check if there is a pilot channel around by searching only the pilot corresponding to the integer multiple of the system parameter PILOT-INC. When the pilot channel is found, the received channel is included in a candidate set. When the signal of the current base station is weakened, a handover is performed to the base station of the candidate set. Looking at this in detail.

2 shows that as the base station A moves from the base station A, the strength of the received signal of the base station A decreases, and the strength of the received signal of the base station B gradually increases.

In Figure 2, the parameters for measuring the pilot strength used to determine the handover time is as follows.

T _add is a value of base station pilot strength that a neighbor base station must satisfy to enter a candidate base station.

T _drop is the lowest signal level value for the base station to remain in the active set.

T _comp (T _compl ) is a value for comparing the difference between the pilot strength of the candidate group, the pilot strength of the active set, and the strength difference of the pilots belonging to the active set for the base station of the candidate group to enter the active set.

T _tdrop is a channel drop timer value required for the pilot belonging to the active set to be deleted from the active set.

ADD refers to a pilot of neighbor sectors or cells added as an active set when a mobile terminal moves to a neighbor sector or cell in a code division multiple access (CDMA) handover scheme.

DROP means that the pilot existing in the active set is deleted in the code division multiple access (CDMA) handover scheme.

The pilot strength measurement message (PSMM) is a pilot strength measurement message received by the base station (BS) / base international controller (BSC) from the mobile terminal.

The Handover Direction Message (HDM) is a message used when a BS / BSC requests a handover to a mobile terminal.

Looking at the soft handover procedure with reference to Figure 2 as follows.

First, when the mobile station moves from base station A to base station B, if the pilot signal strength of base station B is greater than T _add , the mobile station transmits a pilot strength measurement message (PSMM) to the base station.

Thereafter, the base station instructs the mobile station to allocate the traffic channel of the base station B through the handover indication message (HDM) and to include the base station B's pilot in the active set. At this time, the mobile terminal simultaneously establishes a call path with the base stations A and B.

Next, as the mobile terminal gradually approaches the base station B, the strength of the pilot signal of the base station A falls below T _drop . At this time, the mobile terminal operates a timer to cause T _tdrop. After a few seconds, the pilot strength of the base station A is measured, and if the pilot strength of the base station A is still below T _drop , a pilot strength measurement message (PSMM) is transmitted to the base station to release the call path with the base station A.

Subsequently, the base station receiving the pilot strength measurement message PSMM releases the channel talking to the base station A through the handover indication message HDM to the mobile terminal, and the handover is terminated.

As shown in FIG. 2, the area where the channel is released by T _tdrop from the time T _add is referred to as a 'soft handoff area'.

As described above, if the mobile terminal does not receive the handover service due to the traffic load and the channel condition of the base station B at the time of T _add , the handover service is suspended until the time of T _comp of FIG. 2. Where T _comp The time point is a time point at which the pilot strength of the neighboring base station becomes T _comp or more than the pilot strength of the serving base station.

Therefore, since the mobile terminal, which has not been provided with the handover service, moves away from the base station A while approaching the T _comp point, the call is more likely to be disconnected when the propagation environment becomes poor.

If the mobile terminal does not receive the handover service even at the time of T _comp , the handover service failure occurs, and the call is stopped when the signal from the base station A becomes weak.

As described above, when soft handover occurs as described in IS-95 (i.e., when a mobile terminal moves from one cell to an adjacent cell (2a)), two traffic allocated from both base stations in the cell boundary region Channels are used simultaneously.

Therefore, during the soft handover, the mobile terminal forms a call path simultaneously with both base stations, thereby receiving power control of a base station having a better radio wave environment and maintaining good call quality.

This is called a soft handover method, and in this case, handover can be basically performed without information of a neighbor base station.

However, searching for the pilot channel in all cases in this case results in a large scanning delay time and increases the power consumption of the terminal when the number of cases is large, and the neighboring base stations belonging to different switching stations using different frequency resources are used. In this case, the soft handover method cannot be used. In addition, soft handover is basically applicable only to a CDMA mobile communication system based on a rake receiver, but not to a recent communication system based on OFDMA.

On the other hand, the IS-95 CDMA mobile communication system can also receive information on the neighboring base station from the existing base station can be used to perform scanning by using this. Scanning is performed in the same manner as above for neighboring base stations using other FAs.

B. 3GPP WCDMA

Like the IS-95, soft handover is performed when the FA is the same and hard handover when the FA is different. Accordingly, except in the case of searching for a pilot corresponding to an integer multiple of PILOT-INC in soft handover, the neighbor base station receives information from the current base station and performs scanning based on the information.

C. Mobile WiMAX-WiBro

Unlike the previous systems, since OFDMA is used, the soft handover method by the rake receiver cannot be applied. Therefore, as shown in FIG. 3, when receiving a MOB_NBR-ADV message (see FIG. 13) 3a with information of an adjacent base station from the current base station (301), the portable Internet terminal performs scanning by using the same. (303--305). The MOB_NBR-ADV message includes information on the frequency used by the neighboring base station, the BS ID, and downlink / uplink burst profiles used by the neighboring base station. Since the reception from the current base station should be stopped when performing the scanning (302), the scanning of the neighboring base station is performed when the current base station is not instantaneously transmitting / receiving data or when the time required for the scanning is allocated from the base station. Done.

Here, the MOB_NBR-ADV (Mobile Neighbor Advertisement) message is an IEEE 802.16e neighbor advertisement message in which the serving base station informs neighbor BS information for handover of the mobile Internet terminal. The serving base station broadcasts the property periodically. Therefore, when the mobile Internet terminal receives the MOB_NBR-ADV message periodically advertised from the base station (serving base station) to which it belongs, to obtain ID, QoS parameter and channel information of neighbor base stations to perform a faster handover later. This information is available.

Referring to FIG. 13, it can be seen that the MOB_NBR-ADV message includes information such as a 24-bit Operator ID, PHY Profile ID, FA Index, BS EIRP, BSID, etc. for N neighbors.

However, in the portable Internet system environment 4a in which indoor / outdoor base stations 12 and 13 coexist as shown in FIG. 4, the portable Internet terminal 11 is not only a handover between the outdoor base stations 12 (403) but also an indoor base station. Handover from (13) to outdoor base station 12 (401) or handover from outdoor base station 12 to indoor base station 13 frequently occurs (402). In this case, when scanning is performed based on the neighbor base station information as in the conventional system, the portable Internet terminal 11 should receive the relevant indoor base station related information from the outdoor base station 12.

However, if the existing method is applied in performing the scanning for the indoor base station 13 in such an environment, various problems arise. That is, the indoor base station 13 existing in one cell may reach tens to thousands, and it is practically impossible to transmit neighboring base station information for scanning to all indoor base stations 13 for scanning. In addition, when the outdoor base station 12 knows the location information of the indoor base station 13 and the location information in the cell of the mobile Internet terminal 11, only the indoor base station related information around the terminal is transmitted to the mobile Internet terminal 11. Although it is possible to transmit, in the current system, not only the location tracking of the mobile Internet terminal 11 is difficult, but also the management of the location information of the indoor base station 13 is considerably large if there are many indoor base stations 13 in the cell. Becomes

In order to solve this problem, the portable Internet terminal 11 stores the information of the indoor base station 13 without receiving the neighbor base station information. When the signal size of the outdoor base station 12 decreases, There is an existing method of performing a handover by scanning the content base station 13. However, this method always scans the indoor base station 13 even when it is far from the indoor base station 13, resulting in unnecessary power consumption and an increase in handover delay time. In addition, there is a possibility that the signal of the outdoor base station 12 is sufficiently caught above a predetermined level where the indoor base station 13 is present, and in this case, even when the indoor base station 13 has to be found, the indoor base station 13 (13) The situation can not be found. That is, in the situation where handover to the indoor base station 13 is to be performed, there is a problem that a handover cannot be performed because the indoor base station 13 cannot be scanned.

Therefore, while solving the above problems, there is an urgent need for an efficient scanning method for performing a handover from the outdoor base station 12 to the indoor base station 13.

As such, a scanning process is necessary for handover, and the conventional system performs scanning while receiving and using neighboring base station information for scanning. However, in the case where the outdoor base station 12 and the indoor base station 13 coexist, the portable Internet terminal 11 in the area of the outdoor base station 12 makes a handover to one indoor base station 13. Since indoor base stations 13 in one outdoor base station 12 can reach tens to thousands in a cell, it is impossible to broadcast all the scanning information of these indoor base stations 13. Accordingly, it is an object of the present invention to reduce the amount of neighboring base station scanning information transmitted from the outdoor base station 12 to a realistic level so that the portable Internet terminal 11 can efficiently scan the surrounding indoor base station 13. to be.

Therefore, in the mobile Internet environment in which a plurality of indoor base stations exist in an outdoor base station, when a terminal belonging to an outdoor base station performs a handover to an indoor base station, the nearby indoor base station is efficiently scanned (indoor base station). Scans according to the classification characteristics), and the base station scanning method and the indoor base station for searching for the appropriate indoor base station among the numerous indoor base stations existing in the cell while minimizing power consumption and scanning delay time And a computer readable recording medium having recorded thereon a program for realizing the above methods.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In order to achieve the above object, the present invention provides a method for classifying indoor base stations in a portable Internet system composed of indoor / outdoor base stations. Classifying to; And classifying the personal indoor base station into a Class A personal indoor base station and a Class B personal indoor base station according to the frequency of use of the terminal.

Meanwhile, the present invention provides a method for scanning a base station for handover in a portable Internet system composed of indoor / outdoor base stations, comprising: classifying indoor base stations according to scanning priority based on a preference of a terminal; And periodically searching for an indoor base station nearby or if the movement to the indoor is estimated, sequentially scanning the indoor base station according to the scanning priority.

In addition, the present invention, when a handover is required because the signal of the outdoor serving base station currently receiving the service is smaller than a predetermined level, receiving information of the neighboring outdoor base station, through which the neighboring outdoor base station is preferentially scanned, and the outdoor base station And sequentially scanning the corresponding indoor base station according to the scanning priority when there is no.

In order to achieve the above object, the present invention provides an indoor / outdoor portable Internet system equipped with a processor for the classification of indoor base stations, according to a type of a terminal that attempts to connect an indoor base station to a private indoor base station and a shared indoor. Classifying as a base station; And a computer-readable recording medium recording a program for realizing the function of classifying the personal indoor base station into a Class A personal indoor base station and a Class B personal indoor base station according to the frequency of use of the terminal.

On the other hand, the present invention, in the indoor / outdoor portable Internet system with a processor for scanning the base station for the handover, based on the preferences of the terminal, the function of classifying the indoor base station according to the scanning priority; And a computer-readable recording medium recording a program for realizing a function of sequentially scanning an indoor base station according to the scanning priority, when periodically searching for a nearby indoor base station or moving to an indoor location. To provide.

The present invention as described above, when the existing scanning method in the environment where there is an indoor / outdoor base station is too large because the amount of information of the adjacent base station is not practically applicable, in view of the problem that can be practically applicable by greatly reducing the amount of information of the adjacent base station. There is. That is, by dividing the indoor base station into three categories according to characteristics, and by performing a scanning technique for each case, there is an advantage that can reduce the overhead and eliminate unnecessary power consumption of the terminal.

In particular, the present invention reduces unnecessary scanning in other areas by performing scanning only in an area where a service is likely to be available for a Class A private indoor base station, and a frequency that is likely to search for an indoor base station for a Class B private indoor base station. And by searching only the preamble pattern number has the advantage of reducing the number of unnecessary scanning. In addition, there is an advantage in that it is possible to quickly find the optimal indoor base station by performing scanning in the order of indoor base stations preferred by the terminals.

The above objects, features, and advantages will become more apparent from the detailed description given hereinafter with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention pertains may share the technical idea of the present invention. It will be easy to implement. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is an example of configuration of an indoor / outdoor portable Internet (WiBro) network to which the present invention is applied.

In the mobile Internet environment in which a plurality of indoor base stations 13 exist in the outdoor base station 12 as shown in FIG. 4, the mobile Internet terminal 11 belonging to the outdoor base station 12 is an indoor base station 13. (I.e., the mobile Internet terminal 11 located in the area of the outdoor base station 12 in the mobile Internet environment in which the indoor / outdoor base stations 12 and 13 exist) in the outdoor base station 12 When there is a handover to the indoor base station 13 as long as there exists] (402), an appropriate neighbor base station is efficiently scanned.

Here, the mobile Internet terminal 11 moves indoors from indoors to indoors in a mobile Internet environment composed of an indoor base station 12 and a plurality of indoor base stations 13 existing in an outdoor base station 12. This is a terminal for performing handover. At this time, the indoor base station 13 is classified into private and shared, and classified into Class A / B according to the frequency of use. Accordingly, in order to find the surrounding indoor base station 13, the terminal 11 efficiently scans the indoor base station 13 [scanning for a Class A personal indoor base station, scanning for a Class B personal indoor base station, and shared indoors]. Scanning for the base station] and selects the indoor base station 13 to be handed over.

Here, the process of classifying the indoor base station 13 is as follows.

In the present invention, the indoor base station 13 is classified into three types according to the characteristics as shown in FIG. 5 (Claa A private indoor base station, Class B private indoor base station, and shared indoor base station).

That is, the indoor base station 13 is largely divided into a private indoor base station 14 and a shared indoor base station 15. Here, the personal indoor base station 14 is not a base station used by everyone, but the frequency of use of a specific terminal or a specific group such as a general home or office is relatively high, and the common indoor base station is a coffee shop, a plaza, or a park. Unspecified majority is used mainly.

Since the private indoor base station 14 is mainly used by a single user or a group of users, the scanning operation must be performed so that the target can be easily scanned, while the public indoor base station 15 must be available by an unspecified number. The scanning operation should be performed to easily perform the scanning by handover.

On the other hand, the personal indoor base stations 14 are classified into a Class A personal indoor base station 16 and a Class B personal indoor base station 17 according to the user. That is, for a particular user, a Class A personal indoor base station 16 refers to an indoor base station with a higher priority (eg, frequency of use) of that user, and a Class B personal indoor base station 17 refers to that user's priority. An indoor base station with a low frequency (for example, frequency of use). For example, when users A and B respectively install personal indoor base stations a and b in their own homes, for user A, personal indoor base station a is Class A personal indoor base station 16 and indoor base station b is Class B personal While it is the indoor base station 17, from the user B's point of view, the personal indoor base station b becomes the Class A personal indoor base station 16, and the personal indoor base station a becomes the Class B personal indoor base station 17.

Next, a base station scanning method according to the present invention will be described.

6 is a flowchart illustrating an embodiment of a base station scanning method according to the present invention.

According to the present invention, the scanning situation is divided into two, and according to each situation, another scanning operation (scanning operation for passing to another base station when the signal size of the current outdoor base station 12 decreases, or periodically or indoor base station ( 13) Scanning in a situation where there is a likelihood.

First, when the signal size of the current outdoor base station 12 is reduced (601), a scanning operation process for moving to another base station will be described.

As in the conventional handover scanning process, adjacent outdoor base station-related information is received from the current outdoor base station 12 and based on this, the outdoor base station 12 is scanned (602). By doing so (when the base station search is successful (603)), handover is performed to other outdoor base stations 12 around (604). The reason for preferentially scanning the outdoor base station 12 over the indoor base station 13 is that there are quite a few cases where there is no indoor base station 13 nearby, whereas scanning to the indoor base station 13 is performed. This is because the handover delay increases as the scanning delay time increases.

Accordingly, if the base station search is successful (603) by scanning the outdoor base station 12 (603), handover is performed to the outdoor base station 12 (604), and if no suitable outdoor base station 12 is found. If not (603), the indoor base station 13 (15 ~ 17) is scanned (605 ~ 611) as follows.

The scanning operation will now be discussed in addition to the periodic or indoor base station 13.

Although the signal size of the outdoor base station 12 is above a certain level (601), if there is an indoor base station 13 in the vicinity, since the indoor base station 13 is preferably serviced by the indoor base station 13 periodically Need to find In addition, when it is determined that the indoor base station 13 exists around the user's command or another estimation algorithm, the indoor base station 13 is scanned (605 to 611).

At this time, the scanning process for the indoor base station 13 first scans the Class A private indoor base station 16 (605), and if it fails to find (606) to find the common indoor base station 15 (607). If the public indoor base station 15 search also fails (608), the Class B private indoor base station 17 is searched (609). If the scanning result 610 fails, other outdoor base stations 12 may be scanned (611) or stopped if necessary.

Here, if the indoor base station 13 is found in the scanning steps 605, 607, 609 for each indoor base station (Class A private indoor base station 16, shared indoor base station 15, Class B private indoor base station 17), The lower step may be omitted and a handover may be performed immediately to one of the indoor base stations currently found (604). That is, when the Class A private indoor base station 16 is searched for, a handover is performed to the Class A private indoor base station 16 and the scanning process for the shared indoor base station 15 and the Class B private indoor base station 17 is performed. Omit. In addition, when searching for a shared indoor base station 15 without searching for a Class A private indoor base station 16, a handover is performed to the shared indoor base station 15, and a scanning process for the Class B private indoor base station 17 is performed. Omit.

When scanning is performed in this manner, first, the Class A personal indoor base station 16 which is most preferred from the standpoint of the terminal 11 can be found first and handover is performed. If not present, the next most optimal indoor indoor base station 15 is selected, and then the last preferred Class B private indoor base station 17 is selected, so that the indoor base station 13 based on the preference of the terminal 11 is selected. Preferential scanning of is possible, and finding the most preferred indoor base station 13 in the present situation has the positive effect of not having to scan another indoor base station 13.

In FIG. 6, a scanning process 605 of a Class A private indoor base station 16 is described with reference to FIG. 7.

Since the indoor base station 13 found by the terminal 11 has a high frequency of use, it is possible to store information on the indoor base station 13 in advance. Therefore, the information of the indoor base station 13 for scanning is stored in advance, and the ID of the outdoor base station 12 to which the indoor base station 13 belongs is stored together (7a). In this situation, first, it is checked whether the ID of the outdoor base station 12 to which it belongs and the ID of the outdoor base station 12 to which the stored Class A personal indoor base station 16 belongs match (701).

The check result 701, if matched (702), performs scanning for the corresponding indoor base station (i.e., Class A private indoor base station) based on the stored base station information (703), and the indoor base station (i.e., Class A) If the private indoor base station is not in the vicinity (606), scanning for the common indoor base station 15 is performed (607). If an indoor base station (ie, a Class A private indoor base station) is in the vicinity (606), handover is performed to the Class A private indoor base station 16 (604). At this time, it is determined whether the handover by looking at the signal size and other handover conditions.

If the check result 701 does not match (702), scanning for the public indoor base station 15 is performed (607).

Scanning in this manner can prevent unnecessary scanning in most areas where there are no indoor base stations (particularly, Class A private indoor base stations), thereby reducing power consumption. In addition, since the scanning can be performed without receiving the personal indoor base station-related scanning information from the outdoor base station 12, the outdoor base station 12 does not need to broadcast, and without receiving the neighbor base station information of the terminal 11. Scanning can be done immediately, reducing scanning latency.

Meanwhile, referring to FIG. 6, the scanning process 607 of the common indoor base station 15 will be described with reference to FIG. 8.

In general, the number of shared indoor base stations 15 in one cell is not expected to be realistic, and thus, a method of broadcasting existing neighbor base station information is possible.

Therefore, when the outdoor base station 12 transmits the information about the common indoor base station in the cell together with the neighboring outdoor base station information (8a), and the terminal 11 receives it (801), the common indoor base station ( 15) (802). If the shared indoor base station 15 is in the vicinity (608), handover to the shared indoor base station 15 is performed (604). At this time, it is determined whether the handover by looking at the signal size and other handover conditions.

If the shared indoor base station 15 is not in the vicinity (608), the scanning for Class B private indoor base station 17 is performed (609).

In order to scan the shared indoor base station 15 in this manner, the shared indoor base station 15 initially transmits scanning information about itself to the outdoor base station 12 to which it belongs when the network is formed, and the outdoor base station 12 Receives this information and transmits it to the neighboring base station information.

On the other hand, in Figure 6, the scanning process 607 for the Class B personal indoor base station 17 with reference to Figure 9 as follows.

Here, unlike Class A personal indoor base station 16, since the base station does not include the base station information, some of the scanning information of the base station is received and the Exhaustive search method is performed without knowing the remaining information.

The outdoor base station 12 transmits frequency band and maximum preamble pattern number difference information used by the personal indoor base station 14 together with neighboring base station information for scanning of the Class B personal indoor base station 17.

Here, referring to the frequency band used by the personal indoor base station, the outdoor base station 12 grasps the frequency used by the personal indoor base stations 14 in the cell and transmits it for scanning of the terminal 11. Since there are not many frequency bands used by indoor base stations 13, this information can be transmitted in a realistic manner.

In addition, looking at the difference in the maximum preamble pattern (Preamble Pattern), each indoor base station 13 selects one preamble pattern and performs transmission using it, the terminal 11 is a preamble used by the base station The pattern must be known or estimated before it can be received from the base station. The outdoor base station 12 estimates the maximum value of the number of the preamble patterns that can be received at a certain point in the cell and informs the terminals 11. This is expressed mathematically as Equation 1 below, where the maximum preamble pattern number difference is N _max .

Each indoor base station j informs the outdoor base station 12 of the value of n (r _j ) that can be measured at its location r _j , and the outdoor base station 12 may estimate the maximum value of these values as N _max .

The terminals 11 perform the scanning on the Class B private indoor base station 17 with the above two pieces of information.

The terminal 11 receives some information on the Class B private indoor base station 17 from the outdoor base station 12 (901), and has the lowest preamble pattern number for each candidate use frequency [f (i)]. Scanning is sequentially performed (903, 904, 908, 909), and when a suitable base station is found, it is stored as a handover base station candidate (905). Scanning is performed up to the maximum preamble pattern number (906), and the found base stations are stored as base station candidates (907).

When the scanning is completed, the process moves to the next use frequency (910) and repeats the above operation (903 to 909) to perform scanning on all the use frequencies 911.

If the Class B private indoor base station 17 is in the vicinity (610), the handover is performed to the Class B private indoor base station 17 (604). At this time, it is determined whether the handover by looking at the signal size and other handover conditions.

However, if the Class B personal indoor base station 17 is not in the vicinity (610), scanning for another outdoor base station 12 is performed (611).

Meanwhile, in the present invention, as illustrated in FIG. 10, indoor base stations 13 (that is, a private indoor base station 14 and a shared indoor base station 15) select a preamble pattern number to be used by the indoor base stations 13. When the indoor base station 13 (especially, the personal indoor base station 14) is installed (1001), the preamble pattern numbers that are not used at the current location are identified (1002), and the lowest among them is the preamble pattern number. Determine (1003). By this selection method, N _max is kept small.

When the terminal 11 detects the indoor base station 13 (particularly, the personal indoor base station 14) in the I-th preamble pattern search of one frequency when scanning, only the I + N _max th preamble pattern is detected. The search is made and scanning is interrupted (eg, step 905 and step 907 in FIG. 9). This is to minimize delay time occurring while scanning the entire preamble pattern number. In this way, all of the indoor base stations 13 (in particular, the indoor indoor base station 14) existing in the vicinity can be searched, and through this, the most optimal indoor base station 13 can be selected for handover. (1004).

An example of such a preamble pattern selection method is illustrated in FIG. 11.

As shown in FIG. 11, preamble pattern numbers 1 and 2 are used in the state in which two indoor base stations 1 and 2 (13-1 and 13-2) are in contact with each other (11a). At this time, if two indoor base stations 3, 4 (13-3, 13-4) are additionally installed (11b), indoor base station 3 (13-3) is an indoor base station 1, 2 (13-1, 13) Preamble pattern numbers 1 and 2 cannot be used because they are in contact with -2). Therefore, the preamble pattern number 3 having the smallest number is available, and indoor base station 4 (13-4) uses the lowest number preamble pattern number 1 because there is no indoor base station in contact.

If indoor base stations 5, 6 (13-5, 13-6) are installed in addition to "11b" (11c), preamble pattern numbers 1 and 2 are used according to the preamble pattern numbers used in the periphery. do. That is, since indoor base station 5 (13-5) is in contact with indoor base stations 2 and 3 (13-2 and 13-3), preamble pattern numbers 2 and 3 cannot be used. The indoor base station 6 (13-6) uses the emblem pattern number 1, and the indoor base station 6 (13-6) uses the preamble pattern number 2 having the smallest number among those available in addition to the preamble pattern number 1 of the indoor base station 4 (13-4). use.

In addition, when indoor base stations 5 and 6 (13-5, 13-6) are installed in addition to "11b" (11d), preamble pattern numbers 2 are used according to the preamble pattern numbers used in the periphery. That is, since indoor base station 5 (13-5) is in contact with indoor base stations 1,3 (13-1,13-3), preamble pattern numbers 1 and 3 cannot be used. The indoor base station 6 (13-6) uses the emblem pattern number 2, and the indoor base station 6 (13-6) uses the preamble pattern number 2 having the smallest number among those available in addition to the preamble pattern number 1 of the indoor base station 4 (13-4). use.

In FIG. 11, the indoor base station groups spaced apart (for example, indoor base stations 1,2,3 (13-1 to 13-3) and indoor base stations 4 (13-4) and 11c indoor base stations of 11b). 1,2,3,5 (13-1 to 13-3,13-5) and indoor base station 4,6 (13-4,13-6)] to preamble pattern numbers (eg, preamble at 11b). The preamble pattern numbers 1 and 2) may be equally used in the pattern number 1 or 11c because the base station groups are separated from each other so as not to interfere with each other.

For example, as shown in FIG. 12, there are three indoor base station groups, and each of the base station groups 1 to 3 is separated from each other so as not to interfere with each other, and thus the preamble pattern number is reused. In addition, all indoor base stations use the frequency f1. Here, since there is a point where both preamble pattern numbers 1, 2 and 3 are caught in the vicinity of the base station group 1, N _max becomes "3-1 = 2". Therefore, the outdoor base station 12 transmits the information that the use frequency is f1 and N _max is 2 together with the neighbor base station information (12a). When the terminal 11 scans the indoor base station 13, the terminal 11 first performs a search for the preamble pattern 1 of the frequency f1 (12b) and discovers the corresponding indoor base station 13 around the indoor base station 13. do. Subsequently, since N _max is 2, only up to the third preamble pattern number is searched (12c), and the indoor base station 13 using the third preamble pattern is found (12c). Then, a handover is performed to one of the two searched indoor base stations (that is, indoor base stations of preamble pattern numbers 1 and 3) 13. That is, when the indoor base station 13 is found in the I-th preamble pattern search of the corresponding frequency, only the I + N _max th preamble pattern is searched and the scanning is stopped, thereby scanning the entire preamble pattern number. This can reduce the delay time that occurs.

This method enables handover to indoor base station 13 (especially Class B private indoor base station 17) with realistic base station information transmission of the amount of information. Exhaustive search may be required for the preamble pattern number compared to the conventional method, but delay time and power consumption may be increased. However, since the amount of transmission of neighboring base station related information is significantly smaller than that of the conventional method, the present invention is different from the conventional method. Is applicable to indoor and outdoor base station environment. In addition, the present invention is effective in optimizing the delay time and power consumption by minimizing the number of scanning attempts through the use frequency and the N _max information.

For reference, in the IEEE 802.16e, the international standard of the mobile Internet, the terminal 11 is a mobile base station advertisement (MOB_NBR-ADV) message (IEEE 802.16e neighbor advertisement message), which is neighbor base station related information before scanning for handover. And a serving base station periodically advertises network attributes for neighboring base stations) (see FIG. 13), and then scans the neighboring base station based on the received base station.

The MOB_NBR-ADV message contains information on the frequency and preamble index used by each neighboring base station, the ID of the neighboring base station, and transmission related parameters. On the other hand, since there is no consideration of indoor / outdoor base stations 12 and 13 in the current standard, information for distinguishing indoor / outdoor base stations does not exist. In addition, the handover process of the current standard only refers to performing scanning, and there is no mention of a specific method of scanning such as stopping the scanning according to the scanning priority or condition.

Therefore, in the present invention, the indoor base station 13 is first classified into Class A and B private indoor base stations 16 and 17 and the shared indoor base station 15 according to priority (for example, frequency of use). The method of performing and stopping the scanning according to the ranking and the conditions was suggested.

In addition, in the present invention, modification of the MOB_NBR-ADV message including the existing neighbor base station information is required.

First, a field indicating whether the neighboring base station is the outdoor base station 12 or the shared indoor base station 15 is needed for each neighbor base station related information. This is simply by inserting the base station type information field independently or by distinguishing between the outdoor base station 12 and the shared indoor base station 15 when the BS ID is assigned to the base station. 15) may be able to determine whether or not. In addition, the following fields should be added for scanning of the personal indoor base station 14.

a. N_PBS_FA: the number of frequencies used by the private indoor base station 14 in the cell

b. for (j = 0; j <N_PBS_FA; j ++)

PBS_FA: Frequency that the personal indoor base station 14 is using

 (Lists N_PBS_FA frequencies)

c. N _max : The maximum difference of the index values in the set of detected preamble indexes at a point in the cell.

Lastly, for efficient scanning, the preamble index having the smallest value among the indexes of the preamble detected at the point of the indoor base station 13 is used while using the same frequency used by the personal indoor base station 14 as much as possible. The portion recommended for private indoor base stations 14 to select should be inserted into the MOB_NBR-ADV message.

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

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

The present invention can be used for an integrated portable Internet system composed of indoor / outdoor base stations.

1 is a flowchart illustrating a handover process in a mobile communication system according to the prior art;

2 is a diagram illustrating a soft handover process in an IS-95 CDMA mobile communication system according to the prior art;

3 is an explanatory diagram showing a handover scanning process and a MOB_NBR-ADV message in IEEE 802.16e according to the prior art;

4 is an exemplary configuration diagram of an indoor / outdoor portable Internet (WiBro) network to which the present invention is applied;

5 is an explanatory diagram showing a classification process and a scanning priority process of an indoor base station according to the present invention;

6 is a flowchart illustrating an embodiment of a base station scanning method according to the present invention;

FIG. 7A is an exemplary diagram illustrating a scanning process for a Class A private indoor base station in the base station scanning method of FIG. 6.

8 is a diagram illustrating an example of a scanning process for a common indoor base station in the base station scanning method of FIG. 6;

9 is a diagram illustrating an example of a scanning process for a Class B private indoor base station in the base station scanning method of FIG. 6;

FIG. 10 is a diagram for explaining a preamble pattern selection process of an indoor base station in the base station scanning method of FIG. 6;

FIG. 11 is a detailed diagram illustrating an embodiment of selecting a preamble pattern in FIG. 10; FIG.

12 is a detailed view illustrating an embodiment of a scanning process for the Class B personal indoor base station of FIG. 9;

FIG. 13 is a diagram illustrating an embodiment of a MOB_NBR-ADV message used in the present invention. FIG.

* Explanation of symbols for the main parts of the drawings

11: Mobile Internet Terminal (MS) 12: Outdoor Base Station (BS)

13: indoor base station (BS)

Claims (17)

A method of classifying an indoor base station in a portable internet system composed of indoor / outdoor base stations, Classifying the indoor base station into a private indoor base station and a shared indoor base station according to a type of a terminal attempting to access the indoor base station; And Classifying the personal indoor base station into a Class A personal indoor base station and a Class B personal indoor base station according to the frequency of use of the terminal. Classification method of the indoor base station comprising a. The method of claim 1, The common indoor base station, the Class A and Class B personal indoor base station, A classification method of an indoor base station, characterized in that it has a priority in scanning a base station for handover. The method according to claim 1 or 2, The indoor base station, A method of classifying indoor base stations, characterized in that the preamble pattern number used in the surrounding area is first identified, and then the smallest number among the remaining preamble pattern numbers except for this is selected as the preamble pattern number to be used by the base station. A base station scanning method for handover in a portable internet system composed of indoor / outdoor base stations, Classifying the indoor base station according to the scanning priority based on the preference of the terminal; And Periodically searching for indoor indoor base stations or moving indoors, sequentially scanning the indoor base stations according to the scanning priority Base station scanning method comprising a. The method of claim 4, wherein When handover is needed because the signal of the outdoor serving base station currently receiving a service becomes smaller than a predetermined level, the neighboring base station is first received through the information of the neighboring outdoor base station, and the neighboring base station is preferentially scanned. Sequentially scanning the indoor base stations according to the order The base station scanning method further comprising. The method according to claim 4 or 5, The scanning priority is in the order of Class A personal indoor base station, public indoor base station, Class B personal indoor base station, If the high priority indoor base station is found, scanning is stopped and one of the searched indoor base station candidates is selected to perform a handover. The method of claim 6, The indoor base station, For each base station group, the base station scanning method characterized in that after identifying the preamble pattern number used in the surrounding initially selected the smallest number among the remaining preamble pattern numbers except this as the preamble pattern number to be used. The method of claim 7, wherein In scanning the Class A personal indoor base station, Rather than receiving adjacent base station related information from an outdoor base station, the terminal stores scanning information of the Class A personal indoor base station and outdoor base station information to which the Class A personal indoor base station belongs in advance, and scans using the same. Base station scanning method. The method of claim 8, The terminal, If the outdoor base station to which the current terminal belongs and the outdoor base station to which the previously stored Class A personal indoor base station belongs are the same, the scanning of the Class A personal indoor base station is performed, and if there is a difference, the Class A personal indoor base station is not in the vicinity. The base station scanning method, characterized in that determining. The method of claim 7, wherein In scanning the common indoor base station, When the outdoor base station transmits the scanning information together with the neighbor base station information, the terminal extracts information on the common indoor base station from the neighbor base station information and performs the scanning through it. The method of claim 10, The common indoor base station transmits the scanning information about itself to the outdoor base station to which it belongs when the initial network is formed, And the outdoor base station receives the scanning information and transmits the received information to the neighboring base station information. The method of claim 7, wherein In scanning the Class B personal indoor base station, The base station scanning method characterized in that the terminal receives the indoor base station-related information transmitted by the outdoor base station, and performs the scanning "Exhaustive" by using this. The method of claim 12, The outdoor base station, And receiving maximum difference information of preamble pattern numbers detected at a current frequency and a current frequency from all private indoor base stations in a cell, and transmitting the same, including the neighboring base station scanning information. The method of claim 13, The terminal, Based on the maximum difference information between the use frequency and the preamble pattern numbers received from the outdoor base station, the base station characterized in that the scanning is performed only for frequencies and preamble pattern numbers that are likely to search for the Class B personal indoor base station Scanning method. The method of claim 14, The terminal, If one of the used frequencies in the neighbor base station information is selected as the scanning frequency, the preamble pattern number to be scanned starts from the lowest, and the indoor base station search is successful from one preamble pattern number from the number to the neighbor base station information. Scanning further up to the maximum difference value of the preamble pattern numbers and stop scanning for the Class B private indoor base station. In order to classify indoor base stations, indoor / outdoor portable Internet system having a processor, Classifying an indoor base station into a private indoor base station and a shared indoor base station according to a type of a terminal attempting to access the indoor base station; And Classify the personal indoor base station into a Class A personal indoor base station and a Class B personal indoor base station according to the frequency of use of the terminal. A computer-readable recording medium having recorded thereon a program for realizing this. In the indoor / outdoor portable Internet system with a processor for base station scanning for handover, Classifying the indoor base station according to the scanning priority based on the preference of the terminal; And Function to scan the indoor base stations sequentially according to the scanning priority when periodically searching for nearby indoor base stations or moving to indoors A computer-readable recording medium having recorded thereon a program for realizing this.

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