# Patent

## Title
Method and system for transmitting/receiving neighbor base-station advertisement message in broadband wireless access system

## Abstract

Disclosed is a method and system for transmitting/receiving a neighbor base-station information message in a broadband wireless access system. A base station sets and transmits a neighbor base-station information message, which includes a specific flag field for limiting neighbor base-station information and a reserved field and omits iterative neighbor base-station information depending on a value set in the specific flag field, thereby increasing a transmission efficiency. A mobile terminal receives the neighbor base-station information message from the base station, checks the received message, and then updates an operator ID according to the value set in the specific flag field.

## Background
PRIORITY
This application claims the benefit under 35 U.S.C. 119(a) of an application entitled “Method And System For Transmitting/Receiving Neighbor Base-Station Advertisement Message In Broadband Wireless Access System” filed in the Korean Intellectual Property Office on Oct. 26, 2004 and assigned Serial No. 2004-85915, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and system for transmitting/receiving messages in a wireless communication system, and more particularly to a method and system for transmitting/receiving neighbor base-station advertisement messages broadcast by a base station in a broadband wireless access (BWA) system.
2. Description of the Related Art
Fourth generation (4G) communication systems, which are the next generation communication systems, are being designed to provide users with services having various Qualities of Service (QoS) and supporting a transmission speed of about 100 Mbps. Particularly, in current 4G communication systems, research is being undertaken to support a high-speed service by ensuring mobility and QoS in broadband wireless access communication systems, such as a local area network (LAN) system and a metropolitan area network (MAN) system. A representative communication system currently being developed is known as an IEEE (Institute of Electrical and Electronics Engineers) 802.16 communication system.
Compared with conventional wireless technologies for providing voice services, the IEEE 802.16 communication system enables the transmission of data in a shorter period of time than needed if using conventional communication technologies, by providing a wider data bandwidth, and can efficiently use channels by sharing all user channels. In addition, the IEEE 802.16 communication system ensures QoS, so that users can receive services of different QoS depending on the characteristics of the services.
From among the IEEE 802.16 communication system, an IEEE 802.16a communication system does not take into consideration the mobility of a terminal, while an IEEE 802.16e communication system takes into consideration the mobility of a terminal (e.g., a mobile station).
Therefore, in the IEEE 802.16e communication system, a base station periodically broadcasts a MOB_NBR-ADV (mobile neighbor advertisement) message, which is information about neighbor base stations, to all mobile stations located in a corresponding cell in order to support the handover of the mobile stations, thereby notifying the mobile stations of neighbor base-station state information. That is, when a mobile station located in a cell moves into a neighbor cell, the mobile station can perform a handover because the mobile station already understands a neighbor cell's base-station information such as a network identifier and channel characteristics broadcast from the base station.
Table 1 below shows the format of a conventional MOB_NBR-ADV message used to report neighbor base station information from a base station to a mobile station. These message formats are generally known in the art, so a detailed description thereof will be omitted for the sake of clarity.









TABLE 1





Syntax
Size
Notes







MOB_NBR-ADV_Message_Format( )




{




Management Message Type = 53
 8 bits



Operator ID
24 bits
Unique ID assigned to the operator


Configuration Charge Count
 8 bits
Incremented each time the




information for the associated




neighbor BS has changed.


Fragmentation Index
 4 bits
This field indicates the current




fragmentation index.


Total Fragmentation
 4 bits
This field indicates the total number




of fragmentations


Skip-Optional-Fields Flag
 1 bit
If set to ‘1’ and if a neighbor has




OFDMA PHY the BS-ID for that




neighbor is omitted in this message.




If set to ‘0’, BS-ID is not omitted for




any neighbor.


N_NEIGHBORS
 8 bits



For (j=0; j<N_NEIGHBORS; j++){




Length
 8 bits
Length of message information




within the iteration of




N_NEIGHBOR in bytes.


PHY Profile ID
 8 bits
Aggregated IDs of Co-located FA




Indicator, FA Configuration




Indicator, FFT size, Bandwidth,




Operation Mode of the starting




subchannelization of a frame, and




Channel Number


if (FA Index Indicator = = 1) {




FA Index
 8 bits
This field, Frequency Assignment




Index, is present only the FA Index




Indicator in PHY Profile ID is set.




Otherwise, the neighbor BS has the




same FA Index or the center




frequency is indicated using the TLV




encoded information.


}




if (BS EIRP Indicator = = 1) {




BS EIRP
 8 bits
Signed Integer from −128 to 127 in




units of dBm This field is present




only if the BS EIRP indicator is set




in PHY Profile ID. Otherwise, the




BS has the same EIRP as the serving




BS.


}




Neighbor BS-ID
24 bits
This is an optional field for OFDMA




PHY and it is omitted or skipped if




Skip Optional Fields Flag = ‘1’


Preamble Index
 8 bits
The index for the PHY profile




specific preamble. Preamble Index is




PHY specific for SCa and OFDMA.




The value of Preamble Index shall be




ignored and a value of ‘0x00’ shall




be used for OFDM PHY


HO Process Optimization
 8 bits
HO Process Optimization is




provided as part of this message is




indicative only. HO process




requirements may change at time of




actual HO. For each bit location, a




value of ‘0’ indicates the associated




reentry management messages shall




be required, a value of ‘1’ indicates




the reentry management message




may be omitted. Regardless of the




HO Process Optimization TLV




settings, the Target BS may send




unsolicited SBC-RSP and/or REG-




RSP management messages Bit #0:




Omit SBC-REQ/RSP management




messages during current re-entry




processing Bit #1: Omit




PKM-REQ/RSP management




message during current re-entry




processing Bit #2: Omit




REG-REQ/RSP management during




current re-entry processing Bit #3:




Omit Network Address Acquisition




management messages during




current reentry processing Bit #4:




Omit Time of Day Acquisition




management messages during




current reentry processing Bit #5:




Omit TFTP management messages




during current re-entry processing




Bit #6: Full service and operational




state transfer or sharing between




Serving BS and Target BS (ARQ,




timers, counters, MAC state




machines, etc...)


Scheduling Service Supported
 4 bits
Bitmap to indicate if BS supports a




particular scheduling service. ‘1’




indicates support, ‘0’ indicates not




support: bit 0: Unsolicited Grant




Service (UGS) bit 1: Real-time




Polling Service (rtPS) bit 2: Non-




real-time Polling service (nrtPS)




bit 3: Best Effort value of ‘1111’




indicates no information on service




available


  Available Radio Resource
 4 bits
Percentage of reported average




available subchannels and symbols




resources per frame 0000: 0% 0001:




20% 0010: 40% 0011: 60% 0100:




80% 0101: 100% 0110-1110:




reserved 0110-1110: reserved value




of ‘1111’ indicates no information on




service available


 Hand Off Neighbor Preference
 2 bits
00 Normal 01 Preferred 10 Non-




Preferred 11 Reserved


DCD Configuration Change Count
 4 bits
This represents the Neighbor BS




current DCD configuration change




count


UCD Configuration Change Count
 4 bits
This represents the Neighbor BS




current UCD configuration change




count


TLV Encoded Neighbor information
Variable
TLV specific


   }




   }









The following Table 2 illustrates information included in a TLV Encoded Neighbor information field of the MOB_NBR-ADV message, which includes a downlink channel descriptor setting (DCD_settings) field and an uplink channel descriptor setting (UCD_settings) field.










TABLE 2





Name
Type (1 byte)
Length (1 byte)
Value (Variable-length)







DCD_settings

Variable
The DCD_settings is a compound TLV





value that encapsulates a DCD message





that may be transmitted in the advertised





BS downlink channel. This information is





intended to enable fast synchronization of





the SS with the advertised BS downlink.





The DCD settings fields shall contain only





neighbor's DCD TLV values which are





different from the Serving BS





corresponding values. For values that are





not included, the MSS shall assume they





are identical to the serving BSs





corresponding values.


UCD_settings

Variable
The UCD_settings is a compound TLV





value that encapsulates a UCD message





that may be transmitted in the advertised





BS downlink channel. This information is





intended to enable fast synchronization of





the SS with the advertised BS uplink. The





UCD settings fields shall contain only





neighbor's UCD TLV values which are





different from the Serving BS's





corresponding values. For values that are





not included, the MSS shall assume they





are identical to the serving BS's





corresponding values.









The DCD_settings field in Table 2 is configured using the TLV value of a DCD message, which may be expressed in the format of Table 3. Such a DCD_settings field is generally known in the art, so a detailed description thereof will be omitted for the sake of clarity.











TABLE 3






Type





Name
(1 byte)
Length
Value (variable length)
PHY scope



















Downlink_Burst_Profile
1

May appear more than once
All





(see 6.3.2.3.1). The length is





the number of bytes in the





overall object, including





embedded TLV items


BS EIRP
2
2
Signed in units of 1 dBM.
All


Frame duration
3
4
The number of PSs contained
SC





in a Burst FDD or TDD





frame. Required only for





framed downlinks


PHY Type
4
1
The PHY Type to be used.
SC


Power adjustment rule
5
1
0 = Preserve Peak Power
SC, SCa





1 = Preserve Mean Power





Describes the power





adjustment rule when





performing a transition from





one burst profile to another.


Channel Nr
6
1
Downlink channel number as
SCa,





defined in 8.5. Used for
OFDM,





license-exempt operation
OFDMA





only.


TTG
7
1
TTG (in PSs)
SCa,






OFDM,






OFDMA


RTG
8
1
RTG (in PSs)
SCa,






OFDM,






OFDMA


RSSIR,max
9
2
Initial Ranging Max.
All





Received Signal Strength at





BS Signed in units of 1 dBm


Channel Switch Frame
10
3
Channel switch frame
SCa,


Number


number as defined in 6.3.15.7,
OFDM,





Used for license-exempt
OFDMA





operation only


Frequency
12
4
Downlink center frequency
All





(kHz).


BS ID
13
6
Base Station ID
SCa,






OFDM,






OFDMA


Frame Duration Code
14
1
The duration of the frame.
OFDM





The frame duration code





values are specified in Table





230.


Frame Number
15
3
The number of the frame
OFDM





containing the DCD message.









The conventional base station periodically broadcasts a MOB_NBR-ADV message including a TLV encoded neighbor information field as shown in Table 1 in order to notify a mobile station of neighbor base station information. Meanwhile, information related to a base station identifier (BS_ID) field included in the DCD_settings is an iteration of information related to neighbor base-station identifier (neighbor BS_ID) of the MOB_NBR-ADV message. That is, the BS_ID information of the DCD_settings can be recognized by using a neighbor BS_ID and an operator identifier of the MOB_NBR-ADV message. Therefore, the conventional system repeatedly transmits the TLV information of the MOB_NBR-ADV message corresponding to the number of neighbor base stations, and incurs a signaling load due to iterative transmission of the BS_ID of the DCD_settings field.
In addition, an operator identifier (ID) included in the MOB_NBR-ADV message in order to report information about a network operator as shown in Table 1 does not change while a mobile station is using the same network operator. Therefore, when operator ID information is included in every transmitted MOB_NBR-ADV message, overhead may increase, degrading transmission efficiency.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method and system for transmitting/receiving a neighbor base-station advertisement message to be transmitted to a mobile station in a broadband wireless access system.
Another object of the present invention is to provide a method and system for transmitting/receiving a neighbor base-station message in a broadband wireless access system, capable of omitting an operator ID, which must be transmitted whenever a neighbor base-station advertisement message is transmitted, according to necessity and reducing an overhead caused by iterative transmission of base station identifier information.
To accomplish these objects, in accordance with one aspect of the present invention, there is provided a method for receiving a neighbor base-station advertisement message from a base station using a mobile station communicating with the base station in a broadband wireless access system, the method including receiving a neighbor base-station advertisement message, including a predetermined flag field for indicating the presence or absence of operator identifier information; and determining that operator identifier information is current operator identifier information when the predetermined flag field indicates the absence of the operator identifier information is omitted.
In accordance with another aspect of the present invention, there is provided a method for transmitting a neighbor base-station advertisement message from a base station to a mobile station communicating with the base station in a broadband wireless access system, the method including setting a value of a predetermined flag field indicating the presence or absence of operator identifier information to indicate the absence of the operator identifier information; and transmitting a neighbor base-station advertisement message including the predetermined flag field to the mobile station.
In accordance with still another aspect of the present invention, there is provided a broadband wireless access system for transmitting/receiving a neighbor base-station advertisement message, the system including a base station for transmitting a neighbor base-station advertisement message, including a predetermined flag field for indicating the presence or absence of operator identifier information; and a mobile station for receiving the neighbor base-station advertisement message and determining whether the predetermined operator identifier information is current operator identifier information when the predetermined flag field that the absence of the operator identifier information.



BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a diagram illustrating the configuration of cells configured by base stations for supporting an IEEE 802.16e system according to an embodiment of the present invention; and
FIG. 2 is a flowchart illustrating a handover procedure of a mobile station in a mobile communication system according to an embodiment of the present invention.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention. It should be noted that the MOB_ADV message will hereinafter refer to the MOB_ADV message according to an embodiment of the present invention unless indicated otherwise.
The present invention proposes a method and system for minimizing the size of a neighbor base-station advertisement (MOB_NBR-ADV) message to be transmitted in a broadband wireless access system according to the present invention. In detail, the present invention proposes a method for omitting an operator identifier(ID) field of the MOB_NBR-ADV message, and a method for omitting a base station identifier (BS ID) of a downlink channel descriptor (DCD) setting field from among a type/length/value (TLV) encoded neighbor information field of the MOB_NBR-ADV message. The following description according to the present invention can be applied to the IEEE 802.16e system.
FIG. 1 is a diagram schematically illustrating the configuration of an IEEE 802.16e communication system according to an embodiment of the present invention.
A mobile station 10 having received the service of a first base station (BS 1) 21 moves to the cell of a second base station (BS 2) 22 (as depicted by the arrow), which is a neighbor base station. In this case, the mobile station 10 must have information about the neighbor base station in advance in order to receive the service of the second base station 22 and not experience a service discontinuity.
The mobile station 10 can check neighbor base station's network operator information, base station information, scheduling information, available resource information, whether or not a message is fragmented, etc., by receiving and using the MOB_NBR-ADV message. The format of the MOB_NBR-ADV message according to the embodiment of the present invention is shown in Table 4 below.









TABLE 4





Syntax
Size
Notes







MOB_NBR-ADV_Message_Format( )




{




Management Message Type = 53
 8 bits



Operator ID Flag
 1 bit
If set to ‘1’, Operator ID will be




omitted


Reserved
 2 bits



Configuration Change Count
 8 bits
Incremented each time the




information for the associated




neighbor BS has changed.


Fragmentation Index
 4 bits
This field indicates the current




fragmentation index.


Total Fragmentation
 4 bits
This field indicates the total number




of fragmentations


Skip-Optional-Fields Flag
 1 bit
If set to ‘1’ and if a neighbor has




OFDMA PHY the BS-ID for that




neighbor is omitted in this message.




If set to ‘0’, BS-ID is not omitted for




any neighbor.


If ( Operator ID Flag = = 0)




 Operator ID
24 bits
Unique ID assigned to the operator


}




N_NEIGHBORS
 8 bits



For (j=0; j<N_NEIGHBORS; j++){




Length
 8 bits
Length of message information




within the iteration of




N_NEIGHBOR in bytes.


PHY Profile ID
 8 bits
Aggregated IDs of Co-located FA




Indicator, FA Configuration




Indicator, FFT size, Bandwidth,




Operation Mode of the starting




subchannelization of a frame, and




Channel Number


if (FA Index Indicator = = 1) {




FA Index
 8 bits
This field, Frequency Assignment




Index, is present only the FA Index




Indicator in PHY Profile ID is set.




Otherwise, the neighbor BS has the




same FA Index or the center




frequency is indicated using the TLV




encoded information.


}




if (BS EIRP Indicator = = 1) {




BS EIRP
 8 bits
Signed Integer from −128 to 127 in




units of dBm This field is present




only if the BS EIRP indicator is set




in PHY Profile ID. Otherwise, the




BS has the same EIRP as the serving




BS.


}




Neighbor BS_ID
24 bits
This is an optional field for OFDMA




PHY and it is omitted or skipped if




Skip Optional Fields Flag = ‘1’


Preamble Index
 8 bits
The index for the PHY profile




specific preamble. Preamble Index is




PHY specific for SCa and OFDMA.




The value of Preamble Index shall be




ignored and a value of ‘0x00’ shall




be used for OFDM PHY


HO Process Optimization
 8 bits
HO Process Optimization is




provided as part of this message is




indicative only. HO process




requirements may change at time of




actual HO. For each Bit location, a




value of ‘0’ indicates the associated




reentry management messages shall




be required, a value of ‘1’ indicates




the reentry management message




may be omitted. Regardless of the




HO Process Optimization TLV




settings, the Target BS may send




unsolicited SBC-RSP and/or REG-




RSP management messages Bit #0:




Omit SBC-REQ/RSP management




messages during current re-entry




processing Bit #1: Omit




PKM-REQ/RSP management




message during current re-entry




processing Bit #2: Omit




REG-REQ/RSP management during




current re-entry processing Bit #3:




Omit Network Address Acquisition




management messages during




current reentry processing Bit #4:




Omit Time of Day Acquisition




management messages during




current reentry processing Bit #5:




Omit TFTP management messages




during current re-entry processing




Bit #6: Full service and operational




state transfer or sharing between




Serving BS and Target BS (ARQ,




timers, counters, MAC state




machines, etc...)


Scheduling Service Supported
 4 bits
Bitmap to indicate if BS supports a




particular scheduling service. ‘1’




indicates support, ‘0’ indicates not




support: bit 0: Unsolicited Grant




Service (UGS) bit 1: Real-time




Polling Service (rtPS) bit 2: Non-




real-time Polling service (nrtPS)




bit 3: Best Effort value of ‘1111’




indicates no information on service




available


Available Radio Resource
 4 bits
Percentage of reported average




available subchannels and symbols




resources per frame 0000: 0% 0001:




20% 0010: 40% 0011: 60% 0100:




80% 0101: 100% 0110-1110:




reserved 0110-1110: reserved value




of ‘1111’ indicates no information on




service available


Hand Off Neighbor Preference
 2 bits
00: Normal; 01: Preferred 10: Non-




Preferred; 11: Reserved


DCD Configuration Change Count
 4 bits
This represents the Neighbor BS




current DCD configuration change




count


UCD Configuration Change Count
 4 bits
This represents the Neighbor BS




current UCD configuration change




count


TLV Encoded Neighbor information
Variable
TLV specific


}




}









The MOB_NBR-ADV message shown in Table 4 further includes a 2-bit reserved field in order to set the length of the conventional MOB_NBR-ADV message shown in Table 1 using byte units. In the MOB_N BR-ADV message according to the present invention, an operator ID flag field is newly defined. The operator ID flag field is used to report whether a MOB_NBR-ADV message includes an operator ID field. For example, when the operator ID flag field is set to “1”, it indicates that the MOB_NBR-ADV message dose not include an operator ID field. In contrast, when the operator ID flag field is set to “0”, the mobile station refers to an operator ID field.
Since the operator ID field contains information about a network operator, it is unnecessary to periodically update the operator ID field while a mobile station is using the same operator's network. Therefore, while a mobile station is continuously located in the same operator's network, the operator ID flag field is set to “1” and the operator ID field can be deleted. As a result, the total size of the MOB_NBR-ADV message can be reduced by 3 bytes.
Hereinafter, the other fields of the MOB_NBR-ADV message shown in Table 4 will be described.
The MOB_NBR-ADV message includes an 8-bit “Management Message Type=53” field; a “Configuration Change Count” field for representing whether a corresponding message changes, by increasing by “1” whenever configuration changes; a 4-bit “Fragmentation Index” field for representing an order of a currently transmitted message when the MOB_NBR-ADV message is fragmented and therefore transmitted using a plurality of message fragments a 4-bit “Total Fragmentation” field for representing the total number of fragmented messages; and a 1-bit “Skip-Operational-Flag” field. In addition, the MOB_NBR-ADV message includes a 24-bit “Operator ID” field when the Operator ID Flag field is set to “0”.
The other fields except for the above-mentioned fields in the Table 4 are related to the length, BS ID and handoff of neighbor base stations, which are generally known in the art, so a detailed description thereof will be omitted for the sake of clarity.
The operation for performing a handover of a mobile station by using the above-mentioned MOB_NBR-ADV message will be described in detail with reference to the accompanying drawings.
FIG. 2 is a flowchart illustrating a handover procedure of a mobile station in a mobile communication system according to an embodiment of the present invention.
In order to perform a handover, a mobile station 10 must receive information about a neighbor base station in advance of the handover procedure by receiving a MOB_NBR-ADV message from a first base station 21, from which the mobile station 10 is currently receiving service. Therefore, the first base station 21 communicating with the mobile station 10 transmits a MOB_NBR-ADV message according to an embodiment of the present invention as shown in Table 4 in order to reduce iterative transmission of the TLV information of a neighbor base-station message.
Then, as shown in FIG. 2, the mobile station 10 receives the MOB_NBR-ADV message from the first base station 21 in step 201.
In step 202, the mobile station 10 checks an Operator ID Flag field from among the MOB_NBR-ADV message received from the first base station 21. As a result of the determination, if Operator ID Flag field is set to “0”, the mobile station 10 updates the value of the operator ID in step 203, and then proceeds to step 204.
Alternatively, in step 202, if it is determined that the Operator ID Flag field is set to “1”, the mobile station 10 directly proceeds to step 204. In step 204, the mobile station 10 scans a base station 22, to which the mobile station 10 moves, and then performs a handover procedure in step 205.
Meanwhile, the MOB_NBR-ADV message set to reduce iterative transmission of the TLV information of a neighbor base-station message will be described with reference to Table 4.
The MOB_NBR-ADV message includes a 3-byte “Operator ID” field and a 3-byte “Neighbor BS_ID” field. Meanwhile, a 6-byte BS ID field included in the DCD_setting is created by combination of the 3-byte Operator ID and 3-byte Neighbor BS_ID. Therefore, when the MOB_NBR-ADV message includes the Operator ID and Neighbor BS_ID, the 6-byte BS ID field of the DCD_setting message can be omitted.
In the prior art, since the TLV information of the MOB_NBR-ADV message must be repeatedly transmitted by all neighbor base stations, overhead increases proportionately to the number of iterative transmissions of the 6-byte BS ID of the DCD_setting field. In this case, the BS ID field of the DCD_setting TLV has a size of 6 bytes and includes a type of 1 byte and a length of 1 byte, so that the total size for representing the BS ID becomes 8 bytes. However, according to an embodiment of the present invention, the BS ID field from among the format of the DCD_setting is omitted, thereby reducing overhead “R” as expressed in Equation 1 below.

R=N×8 bytes  Equation 1

That is, when a base station broadcasts neighbor base-station information message for 10 neighbor base stations to a mobile station, an overhead of (N×8 bytes=10×8 bytes) 80 bytes can be reduced by omitting the BS ID field included in the DCD_setting message.
As described above, according to the present invention, when a base station transmits neighbor base station information messages to a mobile station in a broadband wireless access system, information either not required to be repeatedly transmitted for every message or iteratively transmitted is omitted, and an indication field (Operator ID Flag) for updating such information is added, so that it is possible to reduce overhead and improve a transmission efficiency.
While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, the scope of the invention is not to be limited by the above embodiments but by the claims and the equivalents thereof.

## Claims

1. A method for receiving a neighbor base station advertisement (MOB_NBR-ADV) message by a mobile station in a broadband wireless access system, the method comprising:
receiving, by the mobile station, the MOB_NBR-ADV message including an operator identifier (ID) flag field indicating a presence or absence of an operator ID field for identifying a network operator to which the neighbor base station belongs, a Configuration Change Count field for representing whether a configuration of the MOB_NBR-ADV message changes, a Fragmentation Index field for representing an order of a currently transmitted message when the MOB_NBR-ADV message is fragmented and transmitted using a plurality of fragmented messages, and a Total Fragmentation field for representing a total number of the plurality of fragmented messages,
wherein the operator ID flag field being set to ‘0’ indicates that the operator ID field is included in the MOB_NBR-ADV message, and
wherein the operator ID flag field being set to ‘1’ indicates that the operator ID field is not included in the MOB_NBR-ADV message.

2. The method as claimed in claim 1, wherein the MOB_NBR-ADV message includes neighbor base station ID information.

3. The method as claimed in claim 2, wherein when the operator ID field is included in the MOB_NBR-ADV message, base station ID information is not included in a downlink channel descriptor.

4. The method as claimed in claim 3, wherein the base station ID information includes information about a network operator ID and the neighbor base station ID information.

5. A method for transmitting a neighbor base station advertisement (MOB_NBR-ADV) message by a base station in a broadband wireless access system, the method comprising:
transmitting, by the base station, the MOB_NBR-ADV message including an operator identifier (ID) flag field indicating a presence or absence of an operator ID field for identifying a network operator to which the neighbor base station belongs, a Configuration Change Count field for representing whether a configuration of the MOB_NBR-ADV message changes, a Fragmentation Index field for representing an order of a currently transmitted message when the MOB_NBR-ADV message is fragmented and transmitted using a plurality of fragmented messages, and a Total Fragmentation field for representing a total number of the plurality of fragmented messages,
wherein the operator ID flag field being set to ‘0’ indicates that the operator ID field is included in the MOB_NBR-ADV message, and
wherein the operator ID flag field being set to ‘1’ indicates that the operator ID field is not included in the MOB_NBR-ADV message.

6. The method as claimed in claim 5, wherein the MOB_NBR-ADV message includes neighbor base station ID information.

7. The method as claimed in claim 6, wherein when the operator ID field is included in the MOB_NBR-ADV message, base station ID information is not included in a downlink channel descriptor.

8. The method as claimed in claim 7, wherein the base station ID information includes information about a network operator ID and the neighbor base station ID information.

9. A broadband wireless access system for receiving a neighbor base station advertisement (MOB_NBR-ADV) message, the system comprising:
a mobile station for receiving the MOB_NBR-ADV message including an operator identifier (ID) flag field indicating a presence or absence of an operator ID field for identifying a network operator to which the neighbor base station belongs, a Configuration Change Count field for representing whether a configuration of the MOB_NBR-ADV message changes, a Fragmentation Index field for representing an order of a currently transmitted message when the MOB_NBR-ADV message is fragmented and transmitted using a plurality of fragmented messages, and a Total Fragmentation field for representing a total number of the plurality of fragmented messages,
wherein the operator ID flag field being set to ‘0’ indicates that the operator ID field is included in the MOB_NBR-ADV message, and
wherein the operator ID flag field being set to ‘1’ indicates that the operator ID field is not included in the MOB_NBR-ADV message.

10. The system as claimed in claim 9, wherein the MOB_NBR-ADV message includes neighbor base station ID information.

11. The system as claimed in claim 10, wherein when the operator ID field is included in the MOB_NBR-ADV message, base station ID information is not included in a downlink channel descriptor.

12. The system as claimed in claim 11, wherein the base station ID information includes information about a network operator ID and the neighbor base station ID information.

13. A broadband wireless access system for transmitting a neighbor base station advertisement (MOB_NBR-ADV) message, the system comprising:
a base station for transmitting the MOB_NBR-ADV message including an operator identifier (ID) flag field indicating a presence or absence of an operator ID field for identifying a network operator to which the neighbor base station belongs, a Configuration Change Count field for representing whether a configuration of the MOB_NBR-ADV message changes, a Fragmentation Index field for representing an order of a currently transmitted message when the MOB_NBR-ADV message is fragmented and transmitted using a plurality of fragmented messages, and a Total Fragmentation field for representing a total number of the plurality of fragmented messages,
wherein the operator ID flag field being set to ‘0’ indicates that the operator ID field is included in the MOB_NBR-ADV message, and
wherein the operator ID flag field being set to ‘1’ indicates that the operator ID field is not included in the MOB_NBR-ADV message.

14. The system as claimed in claim 13, wherein the MOB_NBR-ADV message includes neighbor base station ID information.

15. The system as claimed in claim 14, wherein when the operator ID field is included in the MOB_NBR-ADV message, base station ID information is not included in a downlink channel descriptor.

16. The system as claimed in claim 15, wherein the base station ID information includes information about a network operator ID and the neighbor base station ID information.