KR20100082332A - A method for scanning neighborhood base station in broadband wireless access system - Google Patents

Abstract

PURPOSE: A method for scanning neighboring base stations which is applied to a broadband wireless access system is provided to enable a mobile station to measure the quality of a physical channel necessary for handover and transmit the measurement result to a base station. CONSTITUTION: A serving base station transmits the information relating to a neighboring base station to a mobile terminal. In addition, the serving base station transmits a scan response message to the mobile terminal. The scanning response message includes a report mode corresponding to scan duration, scan iteration number, interleaving interval and scanning result report. In addition, the scanning response message is transmitted to the serving base station without the request of the mobile terminal.

Description

A Method for Scanning Neighborhood Base Station in Broadband Wireless Access System

The present invention relates to a neighbor base station scanning method applied to a broadband wireless access system, and more particularly, to a scanning method that can perform scanning more efficiently without repeatedly transmitting and receiving a scanning request message and a scanning response message. It is about.

The IEEE802.16e system, which is undergoing international standardization for broadband wireless access system, does not have a hierarchical structure such as HLR, VLR, MSC, BSC, RNC, etc. unlike the existing second generation or third generation mobile communication systems. A mobile subscriber station (MSS), a base station (BS) and an authentication service authorization server (hereinafter, referred to as an 'ASA server') are formed. A common physical (PHY) layer and a medium access control (MAC) layer are defined between the base station and the mobile station.

1 is a diagram illustrating an embodiment of a handover operation in a data plane in a broadband wireless access system.

2 is a diagram illustrating an embodiment of a handover operation in a control plane in a broadband wireless access system.

1 and 2, in a broadband wireless access system, handover is performed through the following process. Hereinafter, a handover process according to the conventional IEEE802.16e will be described.

1. Preprocessing for Handover

The pre-processing process for handover of IEEE802.16e includes a process of notifying neighboring base stations by broadcasting information related to neighbor base stations (Network Topology Advetisement) and measuring channel quality of neighboring base stations based on this information. MSS scanning of neighbor BS, and optionally association procedures for matching power of neighboring base station and initial mobile station, and time difference value for synchronization.

① Network Topology Advetisement

The base station broadcasts the information related to the network configuration information to all mobile stations in the cell through the MOB_NBR-ADV MAC message to inform all mobile stations in the cell of the neighbor base station.

② MSS scanning of neighbor BS

The mobile station needs to scan the neighbor base station for handover. The mobile station requests a scanning interval for scanning the neighbor base station through the MOB_SCN-REQ MAC message, and the base station responds to the MOB_SCN-RSP MAC. Send a message to allocate a period during which the mobile station can scan neighboring base stations. In addition, the base station may transmit a MOB_SCN_RSP MAC message directly without the mobile station's request (Unsolicited request). At this time, the scanning period allocated by the base station and the offset unit for scanning start are all allocated in the frame unit.

Association Procedures

Association procedures are processes in which a mobile station normally joins a cell by performing a ranging process with the base station (the mobile station acquires basic information for communication from the base station). That is, when the mobile station scans the base station and selects a new base station, 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 set the power offset value and the timing offset value of the mobile station to appropriate values. Transmitting the RNG_REQ MAC message is called initial ranging operation. This is a basic operation for the mobile station to perform a network entry process. A target base station, which accepts a new mobile station at handover, transmits the association of a specific mobile station to its cell to a serving base station to which the mobile station previously belonged. Will save the information.

2. Handover process

The mobile station starts the handover based on the channel quality information with the neighbor base station obtained in the handover preprocessing.

① Cell Selection

3 is a flowchart illustrating an embodiment of a cell selection process of a mobile station. Cell selection operates before the mobile station normally registers with the cell, and selects the SINR of the signal that is superior to the Signal to Interference Noise Ratio (SINR) of the signal transmitted by the mobile station at the current cell's base station. In order to newly register as a base station that can be received, the cell is changed. At this time, since the mobile station has not performed the registration process, the base station is in a state where the mobile station is not known.

② HO initiation

Handover initiation can be performed by both the base station and the mobile station. That is, when the base station requests a handover, the base station transmits a MOB_BSHO-REQ MAC message to the mobile station. However, when the mobile station requests a handover, the mobile station transmits a MOB_MSSHO-REQ MAC message to the base station.

When the mobile station sends the MOB_MSSHO-REQ MAC message, it first transmits the SINR of the signal received from the neighboring base station to the base station. Through this, the candidate base station (Candidate BS), which may be the target base station during handover, is transmitted to the current service providing base station.

An acknowledgment signal for handing over a specific mobile station from a neighboring base station before the base station receives a MOB_MSSHO-REQ MAC message from the mobile station or transmits a MOB_BSHO-REQ MAC message transmitted by the base station to handover the mobile station; After confirming 'ACK'), handover of the mobile station is allowed. The mobile station or the base station receiving the MOB_BSHO / MSSHO-REQ message transmits a MOB_MSSHO / BSHO-RSP MAC message to inform the target base station to perform the handover.

③ HO cancellation

After the mobile station or the base station sends the MOB_MSSHO / BSHO-REQ MAC message to perform the handover, the mobile station can cancel the handover. At this time, the mobile station sets a specific field of the MOB_HO-IND MAC message (HO_Type = 01) and transmits it to the base station, and the base station receiving the mobile station cancels the handover in progress.

④ Termination with the serving BS

The mobile station sends a MOB_HO-IND MAC message to the serving base station to inform that the handover is completed normally, and completes the handover operation. At this time, the mobile station sets a specific field of the MOB_HOIND MAC message (HO Type = 00) to transmit to the serving base station that the handover is normally completed. The base station receives the MOB_HOIND MAC message from the mobile station and terminates all connections related to MAC state machine, automatic reqeat request (ARQ) connection, and data transmission that were assigned to the mobile station that performed the handover immediately. do.

⑤ HO rejection

The mobile station may reject the handover recommended by the base station. At this time, the mobile station sets a specific field of the MOB_HO-IND MAC message (HO Type = 10) and transmits it to the base station. When the base station receives a reject message from the mobile station, the base station re-identifies the target BS and retransmits the MOB_BSHORSP message to the mobile station.

3. Adjacent Base Station Scanning Procedure

4 is a flowchart illustrating a neighboring base station scanning method according to the prior art. Referring to FIG. 4, a service providing base station connected to a mobile station broadcasts information on an adjacent base station to all mobile stations in a base station area.

The information on the neighbor base station is delivered in the MOB-NBR-ADV message. Table 1 shows an example of the configuration of the MOB-NBR-ADV message.

Syntax Size Notes MOB-NBR-ADV_Message_Format () {  Management Message Type = 49 8 bits  Operator ID 24 bits Unique ID assigned to the operator  N_NEIGHBORS 8 bits  For (j = 0; j <N_NEIGHBORS; j ++) {   Neighbor BS-ID 48 bits   Physical Frequency 32 bits   Configuration Change Count 8 bits   Hysteresis threshold 8 bits   MAHO report period 8 bits   TVL Encoded Neighbor information Variable TLV specific  } }

As shown in Table 1, the MOB-NBR-ADV message includes the number of neighboring base stations, an identifier of neighboring base stations, frequencies used by neighboring base stations, channel information of neighboring base stations, and the like.

Upon receiving this message, the mobile station temporarily stops receiving data transmitted from the serving base station and transmits a MOB-SCN-REQ message to the base station to obtain time for measuring channel quality from the neighboring base station. Table 2 shows an example of the configuration of the MOB-SCN-REQ message.

Syntax Size Notes MOB_SCN_REQ_Message_Format () {  Management Message Type = 50 8 bits  Scan Duration 12 bits Units are frames  Reserved 4 bits  }

While the mobile station measures the channel quality of the adjacent base station, the serving base station may stop transmitting data to the mobile station and transmit the data after the scanning time requested by the mobile station. The serving base station sends a MOB-SCN-RSP message to the mobile station in response to the MOB-SCN-REQ. Table 3 shows an example of the configuration of the MOB-SCN-REQ message.

Syntax Size Notes MOB-SCN-RSP_Message_Format () {  Management Message Type = 50 8 bits  Scan Duration 12 bits Units are frames  Start frame 4 bits  }

As indicated in the MOB-SCN-REQ message, the base station guarantees the scanning duration requested by the mobile station, and the mobile station waits for a start frame time before starting the base station scanning.

According to the neighbor base station scanning method according to the prior art as described above, there are the following problems.

The mobile station may initiate a handover in order to be provided with disconnection free service from the base station. Alternatively, the base station can command the mobile station to handover for load balancing. In this case, the mobile station performs scanning for neighbor base stations to determine whether to perform handover. Therefore, when handover is necessary, it is necessary to continuously scan neighboring base stations. However, in the conventional method, since the mobile station needs to transmit a scanning request message each time to receive the neighboring base station to obtain channel quality information and receive a scanning response message accordingly, the mobile station not only continuously occupies limited radio resources but also receives the message. There is a problem in that power of a mobile station required for transmission and reception is unnecessarily consumed.

An object of the present invention is to provide a neighboring base station scanning method for more efficiently measuring the quality of a physical channel required for handover by a mobile station and transmitting the result to a base station in a broadband wireless access system.

In one aspect of the present invention, a method for supporting scanning of a neighboring base station in a wireless communication system includes a step of a serving base station transmitting information related to at least one neighboring base station to a mobile terminal and a serving base station scanning interval; (scan duration), the scan iteration associated with the number of repetitions of repeating scanning to at least one neighboring base station, the interleaving interval interleaved between the scanning intervals, and the report on the scanning of the mobile terminal ( and transmitting a scanning response message including a report mode corresponding to the frequency of the report to the mobile terminal. In this case, the scanning response message may be transmitted from the serving base station without request of the mobile station.

In another aspect of the present invention, a serving base station supporting scanning of a neighboring base station in a wireless communication system includes: a means for transmitting information related to at least one neighboring base station to a mobile terminal and a serving base station scanning a scanning interval; duration, scan iteration associated with the number of iterations of repeating scanning to at least one neighboring base station, interleaving intervals interleaved between each scanning operation, and reporting of the scanning of mobile terminals Means for transmitting a scanning response message to the mobile terminal including a report mode indicating a method. In this case, the scanning response message may be transmitted from the serving base station without request of the mobile station.

In aspects of the invention, the reporting mode is a no report mode in which the mobile station does not report, a periodic report mode in which the mobile station reports periodically, and a report in which the mobile terminal is driven by an event. It may indicate one of event-triggered report modes.

In embodiments of the present invention, the report mode may be represented by 2-bit information. At this time, if the report mode is displayed as '00', it indicates no report mode. If the report mode is displayed as '01', it indicates periodic report mode. If the report mode is displayed as '10', the event is displayed. Indicates the event-triggered report mode.

The serving base station may receive a scan report message transmitted by the mobile terminal according to a report mode included in the scanning response message. In this case, the scan report message may include a measurement result for at least one neighboring base station.

In the embodiments of the present invention, when the reporting mode indicates the periodic reporting mode, the scanning response message may further include a reporting period parameter indicating a period for reporting the measurement result. In addition, the event trigger report mode may instruct the mobile station to report the measurement results for at least one neighboring base station to the serving base station after each measurement.

According to the present invention, when a mobile station performs scanning of neighboring base stations in a broadband wireless access system, scanning can be performed more efficiently without repeatedly transmitting and receiving a scanning request message and a scanning response message.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory diagram of a handover operation in a data plane in a broadband wireless access system.
FIG. 2 is a diagram illustrating an embodiment of handover operation in a control plane in a broadband wireless access system. FIG.
3 is an embodiment flow diagram illustrating a cell selection process of a mobile station.
Figure 4 is a flow diagram of an embodiment of a neighbor base station scanning method according to the prior art.
5 is a flowchart illustrating an embodiment of a neighboring base station scanning method according to the present invention;

In order to achieve the above object, the present invention provides a method for scanning a neighbor base station applied to a broadband wireless access system, the scanning duration, the number of scan iterations, and a general function. And transmitting a scanning request message including information on an interleaving interval to the base station, and repeatedly scanning neighboring base stations during the scanning interval for each of the general function execution intervals.

The above-mentioned objects, features and advantages will become more apparent from the following detailed description in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

When a mobile station requests a base station for a scanning duration for measuring channel quality of an adjacent base station, the base station provides information to the base station about the period of scanning and the number of repetitions for scanning so that the base station can periodically perform scanning. send. In the case of periodically scanning the neighboring base stations, the period of performing the scanning is equal to the time between each scanning execution interval, that is, the interleaving interval for transmitting data between the mobile station and the base station. Therefore, hereinafter, a period for performing scanning will be expressed as a general function interleaving interval.

The channel quality information measured at the mobile station may be a signal-to-noise ratio, a bit error rate, a quality identifier of a service, and the like received from a neighboring base station. Table 4 shows an example of the configuration of a scanning request message according to the present invention.

Syntax Size Notes MOB-SCN-REQ_Message_Format () {  Management Message Type = 50 8 bits  Scan Duration 12 bits Units are frames  Interleaving interval x bits  Scan iteration y bits  }

As shown in Table 4, the mobile station transmits information for performing periodic scanning to the base station using the scanning interval request message. The scanning interval request message includes information on the size of the scanning interval (Scan Duration), the time to start scanning (Start Frame), the number of repetitive scanning (Scan Iteration) and the general function interval (Interleaving Interval).

The base station receiving the scanning interval request message from the mobile station transmits a scanning response message to the mobile station in response. Table 5 shows an example of the configuration of a scanning response message according to the present invention.

Syntax Size Notes MOB-SCN-RSP_Message_Format () {  Management Message Type = 50 8 bits  Scan Duration 12 bits Units are frames  Start frame 4 bits  Interleaving interval x bits  Scan iteration y bits  }

As shown in Table 5, the base station transmits a scanning response message to the mobile station in response to the scanning interval request message of the mobile station. The scanning response message includes information about an allowable scanning duration, a start frame, a start frame, a scan iteration, and an interleaving interval.

The mobile station periodically measures the channel quality of the adjacent base station based on the information contained in the scanning response message sent from the base station. The information on the start frame, the scan iteration, and the interleaving interval that the base station informs the mobile station may be transmitted in response to the request of the mobile station. It may be sent without a request.

5 is a flowchart illustrating an embodiment of a neighboring base station scanning method according to the present invention. Referring to Figure 5, during the scanning interval in which the mobile station measures the channel quality of the adjacent base station, when data to be transmitted to the mobile station occurs, the base station stores the data in the base station once without transmitting data to the mobile station. The mobile station transmits data stored in an interval in which the mobile station does not perform scanning on a neighboring base station, that is, in an interleaving interval.

On the other hand, when the data transmission time is long and the transmission of data is not completed until the newly started scanning start frame (Start Frame), the base station may ignore the scanning start time (Start Frame) of the mobile station may continue to transmit data. In addition, the data transmission may be stopped according to the scanning start time of the mobile station and then transmitted again when the scanning interval of the mobile station is completed.

If the base station continues to transmit data ignoring the scanning start time of the mobile station, the mobile station is no longer valid for the scanning interval, interleaving interval, and scanning repetition number assigned through the scanning response message from the base station. You may decide not to scan any more.

When the base station ignores the scanning period and continues to transmit data during the scanning period of the mobile station, the base station may receive data from the base station and perform the scanning process as many times as the number of repetitions that have not been performed yet. In addition, by continuously scanning for the section that could not be scanned by the data transmission of the base station, scanning may be performed for the entire scanning period (the product of Scan Duration and Scan Iteration) initially allocated from the base station.

In addition, it is possible to use the channel quality measurement result of the neighboring base station obtained through the scanning of the mobile mobile station or to determine whether the base station commands handover to the mobile station for the purpose of adjusting the network load in the base station. In such a case, the base station may request the mobile station to measure the channel quality of the neighboring base station to determine if the mobile station needs to perform a handover.

The channel quality measurement request from the base station to the mobile station may be generated according to the needs of the base station. The mobile station receiving the request transmits the result of measuring the channel quality with the neighboring base station to the base station requesting the measurement. 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 station.

The method of reporting the measurement result of the mobile station may be selected by the base station or may be selected by the mobile station. Table 6 shows an example of a scanning response message including information on the selection.

Syntax Size Notes MOB-SCN-RSP_Message_Format () {  Message Message Type = 50 8 bits  Scan Duration 12 bits Units are frames  Start frame 4 bits  Interleaving interval x bits  Scan iteration y bits  Scan Report 2 bits 00: no report
01: periodic report
10: event triggered report
11: reserved  Scan Report Period z bits Available when the value of Scan Report is set to 01  }

The mobile station may or may not report the measured result periodically according to the identifier of the scanning response message received from the base station. In the case of reporting the measurement results periodically, the measurement result reporting period may be set separately.

The mobile station does not necessarily send an acknowledgment message for the scanning response message received from the base station. That is, when the mobile station performs an operation different from that commanded by the base station, the base station determines that the scanning response message is incorrectly transmitted, and transmits the scanning response message as necessary.

On the other hand, if a mobile station receives a new message requesting scanning and reporting from the base station while performing a procedure of scanning a neighboring base station and reporting the result to the serving base station, the mobile station ignores all current scanning and reporting procedures, You can perform scanning and reporting procedures according to the message.

The set of periodically repeated scanning durations and interleaving intervals capable of transmitting and receiving data may be stopped at any time at the request of the base station. When requesting such an interruption, the base station may inform the specific area (Scan Duration, Interleaving Interval, Scan Iteration) in the scanning response message shown in Table 5 by filling a specific value, for example, a value of zero. The set of the repeated scanning duration and the interleaving interval capable of transmitting and receiving data may be stopped at any time at the request of the mobile station. To this end, the mobile station may inform a specific area (Scan Duration, Interleaving Interval, Scan Iteration) in the scanning request message shown in Table 4 by filling it with a specific value, for example, a value of zero.

Claims (14)

A method for supporting scanning for a neighboring base station in a wireless communication system,
The serving base station transmitting information related to the at least one neighboring base station to the mobile terminal; And
A scanning duration associated with a scanning duration for the serving base station to repeat scanning for the at least one neighboring base station, an interleaving interval interleaved between the scanning intervals, and the scanning interval Transmitting a scanning response message to the mobile terminal, the scanning response message including a report mode corresponding to a frequency of a report on the scanning of the mobile terminal;
And the scanning response message is transmitted from the serving base station without request of the mobile station. The method of claim 1,
The reporting mode is a no report mode in which the mobile station does not report, a periodic report mode in which the mobile station reports periodically, and an event in which the mobile terminal reports the event. The method of claim 1, characterized by indicating one of the event-triggered report mode. The method of claim 2,
And the report mode is represented by 2-bit information. The method of claim 3, wherein
When the report mode is displayed as '00', it indicates the no report mode. When the report mode is displayed as '01', it indicates the periodic report mode, and the report mode is '10'. And, if displayed, indicate an event-triggered report mode. The method of claim 2,
Receiving a scan report message transmitted by the mobile terminal according to the report mode included in the scanning response message,
And the scan report message includes a measurement result for the at least one neighboring base station. 6. The method of claim 5,
If the report mode indicates a periodic report mode,
And the scanning response message further comprises a reporting period parameter indicating a period for reporting a measurement result. The method of claim 2,
The event trigger report mode instructs the mobile station to report measurement results for the at least one neighboring base station to the serving base station after each measurement. A serving base station supporting scanning for a neighboring base station in a wireless communication system,
The serving base station includes means for transmitting information associated with at least one neighboring base station to the mobile terminal; And
A scanning duration associated with a scan duration of the serving base station, a number of repetitions of repeating scanning with respect to the at least one neighboring base station, an interleaving interval interleaved between each scanning operation, and the Means for transmitting a scanning response message to the mobile terminal, the scanning response message including a report mode indicating a method for reporting the scanning of the mobile terminal,
And the scanning response message is transmitted from the serving base station without a request of the mobile station. The method of claim 8,
The reporting mode is a no report mode in which the mobile station does not report, a periodic report mode in which the mobile station reports periodically, and an event in which the mobile terminal reports the event. And serving one of an event-triggered report mode. The method of claim 9,
The reporting mode is characterized in that represented by the two-bit information, serving base station. The method of claim 10,
When the report mode is displayed as '00', it indicates the no report mode. When the report mode is displayed as '01', it indicates the periodic report mode, and the report mode is '10'. The serving base station, characterized in that indicating the event-triggered report mode. The method of claim 9,
Means for receiving a scan report message transmitted by the mobile terminal according to the report mode included in the scanning response message,
And the scan report message includes measurement results for the at least one neighboring base station. The method of claim 9,
If the report mode indicates a periodic report mode,
The scanning response message further includes a reporting period parameter indicating a period for reporting a measurement result. The method of claim 9,
And the event trigger report mode instructs the mobile station to report the measurement result for the at least one neighboring base station to the serving base station after each measurement.

Images