KR20060012210A - Method for association between neighbor base-station and mobile terminal in broadband wireless access system - Google Patents

Abstract

Since the present invention notifies the target base station to be associated with the fact that a specific mobile terminal will attempt the association in advance, the target base station can allocate resources for the association in advance and perform a quick association. In addition, the present invention allows the mobile station to select an association target base station in consideration of the signal strength with the target base station, the support service level of the target base station, and the available resources of the target base station, so that the association procedure can be performed more effectively. Association method according to the present invention comprises the steps of measuring the channel quality of the adjacent base stations; Determining an association target base station by referring to channel quality and resource information of the neighbor base stations, and notifying the determined target base stations to be associated; According to a predetermined order, a process of performing an association procedure with an association target base station in turn is performed.

Handover, Association, Ranging

Description

METHODS FOR ASSOCIATION BETWEEN NEIGHBOR BASE-STATION AND MOBILE TERMINAL IN BROADBAND WIRELESS ACCESS SYSTEM}

1 is a diagram illustrating a neighboring base station scanning process according to the prior art.

2 is a view showing an association procedure according to the prior art.

3 illustrates an association procedure according to the present invention.

The present invention relates to a broadband wireless access system, and more particularly, to an association procedure performed to support fast handover by simplifying a handover procedure.

In a broadband wireless access system, in order for a mobile station to register with a network for the first time or to re-register with a new base station during handover, the mobile station must synchronize with the base station and assign a management connection ID. This is called initial ranging. . In addition, the mobile station receives a signal from a neighbor base station (Neighbor Base-Station) to measure the signal quality before the mobile station performs the handover.

At this time, if the signal quality is more than a certain level and the base station is superior to the serving base station, the mobile station requests a handover to the serving base station. When the handover response signal is received from the serving base station, initial ranging with the handover target base station is performed to re-register with the actual handover target base station.

In the prior art, before performing the actual handover, in order to reduce the handover time, by measuring the signal quality of the neighboring base stations in the scanning process and performing the initial ranging in advance, the ranging parameters can be reused during the actual handover. How to use. This method is called association (pre-handover).

As such, the preprocessing process for handover of a mobile station in a broadband wireless access system includes a network topology advertisement process of broadcasting information related to a neighboring base station in a base station and informing the mobile stations, and based on the neighboring base station information. There is a MSS scanning of neighbor BS process to measure the channel quality of a neighbor BS, and association procedures for initially matching the neighbor UE with an initial terminal power value and a time difference value for synchronization.

* Network Topology Advertisement

The service base station transmits the information related to the network configuration information to all mobile terminals in the cell through a MAC management message (MOB-NBR-ADV) by broadcasting to inform the mobile terminal in the cell of the neighbor base station information.

* MSS scanning of neighbor BS                         

The mobile station needs to search for the neighboring base station for handover. The mobile station requests the serving base station through the scanning request message (MOB_SCN-REQ) to search for the neighboring base station. A message (MOB-SCN-RSP) is transmitted to allocate a period for the mobile station to search for a neighboring base station. In addition, the serving base station may transmit a scanning response message (MOB_SCN_RSP) directly without request of the mobile station (Unsolicited request). At this time, the search period allocated by the service base station and the offset unit for starting the search are all allocated in units of frames.

Association Procedures

The association process (hereinafter, referred to as an Assiciation process) is performed by the mobile terminal to perform an initial ranging process with a neighboring base station (a mobile terminal obtains basic information for communication from the base station), so that the basic information necessary for communication with the neighboring base station is preliminary. Obtaining, storing, and setting communication with the target base station, which is one of the neighboring base stations, in advance during the actual handover through pre-stored information, so as to reduce the delay time for the handover, the mobile terminal searches for the neighboring base station. If a new base station is selected, the association process is performed. The association transmits the RNG-REQ MAC message to the mobile station, and the base station transmits the RNG-RSP MAC message to the mobile station to set the uplink power offset value and the uptime timing offset value of the mobile station to appropriate values. The transmission of the RNG-REQ / RSP message by the mobile station and the base station (initial ranging operation) is the most basic operation of the IEEE802.16 system. In addition, the mobile terminal becomes a basic operation for performing a network entry process.

The association process is competition based. That is, a plurality of mobile terminals competitively request initial ranging from the base station through a predetermined time and radio resources, and the base station sets Ranging parameters (upward time correction, frequency correction, connection identifier, etc.) through the initial ranging response. Deliver to mobile terminal. If the mobile station does not receive a Ranging response for a predetermined time after the initial Ranging request, it attempts initial ranging again after a predetermined time (Random Backoff time). When the mobile station stores Ranging parameters obtained through the initial Ranging result, the mobile station is successfully associated with the base station.

1 is a diagram illustrating a neighboring base station scanning process according to the prior art.

Table 1 below shows the format of the scanning request message (MOB-SCN-REQ) shown in FIG.

Table 2 below shows the format of the scanning response message (MOB-SCN-RSP) of FIG.

Referring to Fig. 1 and Tables 1 and 2, the related art scanning related operation is as follows.

In order to measure the channel quality of the neighbor BSs BS2 and BS3, the MSS transmits a scanning request message (MOB-SCN-REQ, see Table 1) to the serving BS BS to request scanning. In response to the scanning request of the mobile station, the serving base station determines the scan duration, the start frame, the scan iteration, and the interleaving interval. Information in a scanning response message (MOB-SCN-RSP, see Table 2). Sent to the mobile station, the mobile station periodically measures the channel quality of the neighboring base station based on this information. Information about the start time, number of searches, and search periods which the service base station informs the mobile station may be transmitted in response to the request of the mobile station, or the service base station may be transmitted without the request of the mobile station.

During the period in which the mobile station measures the channel quality of the neighboring base station, if the data to be transmitted to the mobile station is generated, the service base station does not send the data to the mobile station and stores the data, but the mobile station does not measure the channel quality of the neighboring base station. Transmit during intervals.

The serving base station may determine the handover of the mobile station by using the channel quality measurement result of the mobile station or in order to adjust network load in the base station. In this case, the serving base station may request the mobile station to measure the channel quality with the neighboring base station in order to determine the need for handover. The channel quality measurement request to the mobile station may be generated according to the needs of the base station, and the mobile terminal receiving the request transmits the measurement result of the channel quality of the neighboring base station to the service base station.

There are two methods of transmitting the measured channel quality information: a periodic report regardless of a measurement time point or a period, and a report each time channel quality is measured in a mobile terminal. The method of reporting the measurement result of the mobile terminal may be selected by the base station or the mobile terminal. As shown in [Table 2], the base station may select the measurement result reporting method by giving an identifier to the channel quality measurement command message (e.g. MOB-SCN-RSP).

The mobile station may not report the measured result according to the identifier in the channel quality measurement command message received from the base station, may report it periodically, or may report it every time it is measured. In the case of reporting the measurement results periodically, the measurement report period may be set separately. The mobile station does not need to send an acknowledgment message (ACK) for the periodic search and measurement result report message (e.g. MOB-SCN-RSP) received from the base station. When the mobile station performs an operation different from the command of the base station, the base station determines that the neighbor base station search and measurement result report message is incorrectly transmitted, and transmits the neighbor base station search and measurement result report message as needed. On the other hand, when the mobile station performs a procedure for searching for a neighboring base station and reporting a measurement result, and receives a message requesting a search for a new neighboring base station and reporting a measurement result from the base station, the mobile station ignores all current measurement and reporting procedures, and measures and results. Start a new reporting process.

Repeated scan durations and interleaving intervals for data transmission and reception may be stopped at any time by the request of the base station. To this end, the base station may inform by filling a specific field area (SCAN DURATION, Interleaving Interval, SCAN ITERATION) of the MOB-SCN-RSP message with a value of zero.

The repeated scan duration and interleaving interval may be stopped at any time by the request of the mobile terminal. To this end, the mobile station can inform the specific field area (SCAN DURATION, Interleaving Interval, SCAN ITERATION) of the MOB-SCN-REQ message by filling it with a value of zero.

2 is a diagram illustrating an association procedure according to the prior art.

Referring to Figure 2, looking at the conventional Association procedure as follows.

The service base station BS1 periodically transmits channel information of neighboring base stations BS2 & BS3 to the MAC management message (MOB-NBR-ADV) to the mobile station (MSS).

When the mobile station receives the MAC management message (MOB-NBR-ADV), the mobile station transmits a scanning request message (MOB-SCN-REQ) including scanning duration information to the service base station BS1. After receiving the scanning request message (MOB-SCN-REQ), the service base station loads the information on the scanning start time and the scanning period into the scanning response message (MOB-SCN-RSP) and transmits the information to the mobile station.

Thereafter, when scanning starts, the mobile station synchronizes downlink with the neighboring base station and measures the signal quality of the neighboring base stations. During the scanning interval, the mobile station performs an initial ranging with each base station and forms an association. At this time, since the initial ranging is based on competition, it takes a lot of time to perform.

At the end of the scanning period, the mobile station disconnects from the neighboring base station and synchronizes up and down with the serving base station, thereby enabling data transmission and reception with the serving base station.

There are two problems with this conventional association procedure.

First, since the conventional association is performed in the scanning process, there is no specific criterion for which base station the mobile terminal performs association with. For this reason, the mobile station performs association with all neighboring base stations, and thus it takes a lot of time for handover including scanning.

Second, since the conventional Association performs initial ranging based on contention, there is a possibility that the association execution time may be long, and it is difficult to set a scanning period in the scanning request. If the scanning period is shortened, there is a possibility that the association cannot be performed within that period, so that the association is not guaranteed. On the other hand, if the scanning period is set too long, downlink traffic that should be delivered to the mobile station during the period will cause the problem of staying at the base station. And it causes a waste of radio resources.

The present invention is to solve the problems described above, the object is,

An object of the present invention is to provide an association method for newly defining a message transmitted and received between a mobile station and a base station in a preprocessing process for handover.

In order to achieve the above object, Association method according to the present invention is

Before performing the handover procedure, the mobile station of the broadband wireless access system, the method comprising: measuring channel quality of neighboring base stations; Determining an association target base station by referring to channel quality and resource information of the neighbor base stations, and notifying the determined target base stations to be associated; According to a predetermined order, a process of performing an association procedure with an association target base station in turn is performed.

Preferably, the step of informing that the association is to be performed includes: informing the serving base station of a specific mobile station of association by a serving base station according to a request of the mobile station; The predetermined target base stations informing their service base station of their supportable quality of service information; The service base station is characterized in that the process of transmitting the information of the association target base station of the mobile terminal to the corresponding mobile terminal.

Preferably, the procedure of performing an association procedure with the target base stations of the mobile terminal includes: informing the service base station of association with the target base stations of the corresponding sequence; The mobile terminal performing a ranging procedure with the target base station of the corresponding sequence to form an association; When the ranging procedure is terminated, the target base station of the corresponding sequence is configured to notify the end of the ranging procedure to the serving base station.

Preferably, when the serving base station informs the target base station that a specific mobile station will be associated, the target base station allocates resources for ranging of the mobile station.

3 illustrates an association procedure according to the present invention.

Hereinafter, the Association procedure according to the present invention will be described in detail with reference to FIG. 3.

First, MSS measures the channel quality of neighboring base stations BS2, BS3, and BS4 for the purpose of handover. (Step ①) At this time, the neighboring base stations BS2, BS3, and BS4 are the targets. It may be the base stations notified through the MAC management message (MOB-NBR-ADV).

The mobile station requests the service base station for the association (Type = 1) and the identifier of the target base station through the scanning request message (MOB-SCN-REQ). The selection is based on the channel quality obtained in the above process (Step ①) and the resource information (available radio resource ratio, supportable service quality, handover support degree) of the neighboring base station found through the MAC management message (MOB-NBR-ADV). can do.

The serving base station sends a back-bone message (ASC-Notification) to the base stations associated with the association, informing the fact that a specific mobile terminal will attempt the association. (Step ③) At this time, the backbone message (ASC-Notification) Contains information on the MSS ID of the mobile station and the required QoS required by the mobile station.

Subsequently, the association target base station that receives the backbone message (ASC-Notification) informs the service base station of the quality of service (QoS) that it can support to the mobile station as a response message (ASC-Notification-response) (Step ④).

The service base station that receives the response message (ASC-Notification-response) informs the mobile station of the base station to which the mobile station will perform the association through the scanning response message (MOB-SCN-RSP). At this time, the serving base station informs the mobile terminal of the start time for performing association. In addition, the service base station may selectively inform the degree of service that the association target base station can support. The order of association target base stations informed by the serving base station is the order of base stations to which the mobile station should associate.                     

In addition, the serving base station transmits an ASC-Notification to the first target base station of the association, informing the fact that a specific mobile terminal will attempt the association. (Step 6) At this time, the target base station performs the ranging when the mobile terminal performs ranging. In order not to compete with other mobile stations, resources (time and frequency) for ranging of the mobile station are allocated.

Thereafter, the mobile station performs a ranging procedure to the first target base station of the association. (Step ⑦) The RNG-REQ message transmitted by the mobile station is transmitted through a resource allocated from Fast_UL_raging_IE in UL_MAP of the target base station. Ranging can be avoided.

Then, the mobile terminal establishes an association with the corresponding base station by storing information (time correction information, power correction information, frequency correction information, connection separator, etc.) obtained through the ranging process with the first target base station.

By transmitting the ranging response to the mobile station, when the ranging procedure with the mobile station is completed, the target base station informs the serving base station that the ranging procedure was successfully performed. (Step⑨)

The serving base station, which has received the completion of the ranging procedure between the first target base station and the mobile station, sends a backbone message (ASC-Notification) to the second target base station of the association, indicating that the specific mobile station will attempt the association. Again, the target base station allocates resources (time and frequency) for ranging of the mobile station so that the mobile station does not compete with ranging.                     

Thereafter, the mobile station performs a ranging procedure with the second target base station of the association. (Step ⑪) The RNG-REQ message transmitted by the mobile station is transmitted through a resource allocated from Fast_UL_raging_IE in the UL_MAP of the target base station. Can be avoided.

Then, the mobile terminal establishes an association with the base station by storing information (time correction information, power correction information, frequency correction information, connection separator, etc.) obtained through the ranging process with the second target base station.

By transmitting the ranging response to the mobile station, when the ranging procedure of the mobile station is completed, the target base station notifies the serving base station that the ranging procedure has been successfully performed.

If the mobile station fails to associate with the association base station during the association process, the mobile station returns to a normal operation state that can communicate with the serving base station. At this time, the target base station that failed the association sets the action of the backbone message (ASC-Notification-response) to 2 and informs the serving base station, and the serving base station informs other base stations that are going to perform the association to perform the action of the backbone message (ASC-Notification). Set to 2 to indicate that the Association request has been canceled.

As above, the serving base station notifies the association base stations of the fact that a specific mobile terminal will perform the association, and the mobile station performs the association to the target base stations in turn.                     

In the above procedure, the message exchange between the serving base station and the base stations associated with the mobile station may be performed directly or through a management node such as a base station controller (BSC).

Table 3 below shows an example of the scanning request message (MOB-SCN-REQ) format. (The underlined parts are newly added items to the conventional scanning request message (MOB-SCN-REQ).)

The mobile station informs the base station whether to scan or associate through the Type field (0 or 1). If the type is the scanning mode (0), the scanning request is performed in the same manner as in the related art. In the case of the association mode (1), the identifier of the base station that is the target of the association is transmitted to the service base station, and the association target base station is configured for the association. Allows preparation (allocation of resources for non-competitive based ranging).                     

Table 4 below shows an example of the MOB-ASC-RSP format. (The underlined items are newly added to the conventional MOB-SCN-RSP.)

The base station informs the mobile station whether to scan or associate through the type field (0 or 1). When the type is the scanning mode (0), the mobile terminal is scanned in the same manner as in the prior art. In the association mode (0), the mobile station transmits an identifier of the target base station to actually perform the association. When the serving base station informs the mobile station of the base station that is the target of association by the request of the mobile station, the service base station provides a service of the mobile station among the target base stations that the mobile station requested association through a scanning request message (MOB-SCN-REQ). Only the target base station that can be supported can inform the mobile station.                     

Table 5 below shows an example of the backbone message (ASC-Notification) format. (The underlined part is the newly added item.)

Through the backbone message (ASC-Notification) informs that the serving base station can attempt association of a specific mobile terminal (MSS unique ID) to the association target base station. If the value of the Action field is 0, the target base station is informed about the bandwidth and the quality of service required by the mobile station. If the value of the Action field is 1, it means that a specific mobile station attempts association soon and allocate uplink radio resources for a specific mobile terminal.                     

Table 6 below shows an example of the backbone response message (ASC-Notification-response) format. (The underlined part is a newly added item.)

Through the backbone response message (ASC-Notification-response), Association base station responds to the backbone message (ASC-Notification) of the serving base station. When the Action field value is 0 for a specific mobile station (MSS unique ID), the target base station informs the mobile station of information about bandwidth and quality of service that can be supported. When the Action field value is 1, it indicates that the association procedure of a specific mobile terminal is completed.                     

The uplink radio resource for the association of a specific mobile station in the target base station is allocated through the Fast Ranging IE of the following [Table 7] also used in the prior art. The information in Table 7 is included in the UL_MAP message periodically broadcasted by the target base station.

The above messages illustrate an example for explaining the operation of the present invention, and other types of messages for the same purpose may be used.

As described above, the present invention informs the target base station to be associated with the fact that the specific mobile terminal will attempt the association in advance, so that the target base station can allocate resources for the association in advance and perform a quick association. have.

In addition, according to the present invention, when the target base station allocates resources for the association, the mobile station allocates the resources immediately before attempting the association, thereby efficiently using the resources of the target base station.

In addition, the present invention allows the mobile station to select an association target base station in consideration of the signal strength with the target base station, the support service level of the target base station, and the available resources of the target base station, so that the association procedure can be performed more effectively.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (7)

In performing the association before the mobile station of the broadband wireless access system starts the handover procedure, Measuring channel quality of neighboring base stations; Determining an association target base station by referring to channel quality and resource information of the neighbor base stations, and notifying the determined target base stations to be associated; Association method comprising the step of performing the association procedure in turn with the base stations to be subjected to association in a predetermined order. The method of claim 1, wherein the resource information Association method characterized in that it includes the available radio resource rate, supportable quality of service, and handover support information. The process of claim 1, wherein the step of informing that the association will be performed Informing the serving base station of association with the determined target base stations according to the request of the mobile terminal; The predetermined target base stations informing their service base station of their quality of service information; And the service base station transmits the determined target base station information to the mobile terminal. The method of claim 3, wherein the information of the target base stations delivered to the mobile terminal Association method comprising information on the order of the target base station to be associated. The process of claim 3, wherein the informing that the association will be performed The association method, characterized by transmitting the identifier information of the mobile station and the quality of service (QoS) required by the mobile terminal through a backbone message. The method of claim 1, wherein the association procedure with the target base stations is performed. Informing the serving base station that the serving base station will associate with the corresponding target base station; Performing a ranging procedure by the mobile terminal to the target base station of the corresponding sequence and establishing an association; And when the ranging procedure ends, a step in which the corresponding target base station informs the serving base station of the termination of the ranging procedure. 7. The method of claim 6, wherein when the serving base station informs the target base station that it will associate, the target base station allocates resources for ranging of the mobile station.

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