WO2005107379A2

WO2005107379A2 - Method of communicating neighbor base station information

Info

Publication number: WO2005107379A2
Application number: PCT/KR2005/001361
Authority: WO
Inventors: Gi Seon Ryu; Chang Jae Lee; Yong Suk Jin
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2004-05-10
Filing date: 2005-05-10
Publication date: 2005-11-17
Anticipated expiration: 2006-11-10
Also published as: ATE557558T1; CA2564891C; CA2564891A1; US7957761B2; KR20050107667A; US20080051087A1; ATE526803T1; EP1747698B1; CN101453769A; EP2073591A3; JP5142711B2; CN1951142A; JP2007536874A; US7853286B2; EP1747698A2; CN101453769B; WO2005107379A3; JP2009147954A; EP2073591A2; EP2073591B1

Abstract

A method uses inter-base station control messages to provide neighbor base station information to mobile subscriber stations in a mobile communication system. The method includes obtaining (S414, S415), at a serving base station, physical channel information of neighbor base stations over a backbone network via, either directly or via a server; periodically transmitting (S417) the obtained physical channel information from the serving base station to a mobile subscriber station connected to the serving base station; and measuring, based on the updated physical channel information, signal quality of the at least one neighbor base station at the mobile subscriber station. Thus, the serving base station receives from the neighbor base stations the inter-base station control messages containing the neighbor base station information, updates the information, and provides the updated information to the corresponding mobile subscriber station(s), to be used for a specific purpose such as handover or network entry.

Description

METHOD OF COMMUNICATING NEIGHBOR BASE STATION

INFORMATION [DESCRIPTION]

Technical Field

The present invention relates to a method of communicating neighbor base

station information to mobile subscriber stations in a mobile communication system.

Background Art

In a broadband wireless access system such as a radio mobile Internet system, a

mobile subscriber station receives a signal from a neighbor base station and measures a

signal quality to find an optimal base station prior to performing handover. If the signal

quality of the neighbor base station is superior to that of a serving base station, the

mobile subscriber station performs a handover procedure. In doing so, it should be

noted that the mobile subscriber station in the radio mobile Internet system performs

handover between base stations over an air backbone.

A mobile subscriber station tunes its synchronization with a neighbor base

station, receives a signal to measure a signal quality, and previously transmits/receives

parameters required for handover to/from a handover target base station. Hence, a

quick handover is enabled when handover is substantially performed. Namely, a

serving base station periodically transmits information of a neighbor base station to all

mobile subscriber stations within the serving base station via a broadcast message. The

transmitted information, referred to herein as neighbor base station information, includes, for example, the downlink center frequency, base station identifιer(s), and

uplink/downlink channel information.

The mobile subscriber station having received the information of the neighbor

base stations releases its connection to the serving base station during a specific period,

acquires syncs from the neighbor base stations, and then receives signals to measure

respective signal qualities.

A handover procedure of a medium access control (MAC) layer according to a

related art is explained as follows.

Referring to FIG. 1, illustrating a network topology advertisement, a serving

base station delivers information of neighbor base stations to all mobile subscriber

stations within the serving base station using a MAC control message. The MAC

control message provides physical channel information including uplink/downlink

channel information of the neighbor base stations. The mobile subscriber station having

received the message can acquire sync with the neighbor base station efficiently. Referring to FIG. 2, illustrating a neighbor base station scanning process, a

serving base station allocates a time for monitoring a neighbor base station to a mobile

subscriber station to find a target base station fitting for handover. The allocated time is

called a scanning period. During the scanning period, the mobile subscriber station

releases its connection to a current serving base station, tunes its sync with a downlink

transmission signal of the neighbor base station, and measures a quality of a physical

channel. During the scanning period, the serving base station buffers downlink data that

will be transferred to the mobile subscriber station. If the scanning period expires, the serving base station transmits the buffered data to the mobile subscriber station. In

doing so, by measuring a signal quality transferred from the neighbor base station and

by previously exchanging parameters that will be exchanged in handover with a

potential handover target base station, a procedure enabling a quick handover in case

that a real handover occurs is carried out as well.

Referring to FIG. 3, illustrating a handover initiation process, a signal quality of

a neighbor base station is measured. If there exists a neighbor base station having the

signal quality superior to that of a serving base station, a procedure for performing a

handover is executed. Namely, a mobile subscriber station initiates a handover in a

manner of delivering a handover request message to a handover target base station to

the serving base station.

However, even though the neighbor base station information provided to the

mobile subscriber station by the serving base station is defined in a broadcast control

message, the related art method fails to propose how the serving base station acquires

the neighbor base station information.

Disclosure of Invention

The present invention is directed to a method of communicating neighbor base

station information to mobile subscriber stations in a mobile communication system that

substantially obviates one or more problems due to limitations and disadvantages of the

related art.

An object of the present invention is to provide a method of communicating neighbor base station information to mobile subscriber stations in a mobile

communication system, by which a serving base station acquires information of the

neighbor base stations via a backbone network in the mobile communication system to

provide the acquired information to the corresponding mobile subscriber station. Another object of the present invention is to provide a method of

communicating neighbor base station information to mobile subscriber stations in a

mobile communication system, in which base station information is exchanged between

base stations via inter-base station control messages.

Additional advantages, objects, and features of the invention will be set forth in

part in the description which follows and in part will become apparent to those having

ordinary skill in the art upon examination of the following or may be learned from

practice of the invention. The objectives and other advantages of the invention may be

realized and attained by the structure particularly pointed out in the written description

and claims hereof as well as the appended drawings. To achieve these objects and other advantages in accordance with the purpose of

the invention, as embodied and broadly described herein, there is provided a method of

communicating neighbor base station information in a mobile communication system.

The method comprises obtaining, at a first base station, neighbor base station

information from at least one neighbor base station, the neighbor base station

information corresponding to the at least one neighbor base station and being provided

to the first base station over a backbone network; and transmitting the obtained neighbor

base station information from the first base station to a mobile subscriber station connected to the first base station. The mobile subscriber station then can use the

neighbor base station information for a specific purpose.

According to another aspect of the present invention, there is provided a method

of communicating neighbor base station information in a mobile communication system.

The method comprises obtaining, at a serving base station, physical channel information

exchanged over a backbone network using a plurality of inter-base station control

messages, the physical channel information corresponding to at least one neighbor base

station; periodically transmitting the obtained physical channel information from the

serving base station to a mobile subscriber station connected to the serving base station,

the obtained physical channel information being updated for each transmission; and

measuring, based on the updated physical channel information, signal quality of the at

least one neighbor base station at the mobile subscriber station.

Preferably, the inter-base station control messages are delivered between a

server and each of the neighbor base stations using the server operating between the

serving base station and the neighbor base stations.

It is to be understood that both the foregoing general description and the

following detailed description of the present invention are exemplary and explanatory

and are intended to provide further explanation of the invention as claimed.

Brief Description of Drawings

The accompanying drawings, which are included to provide a further

understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description

serve to explain the principle of the invention. In the drawings:

FIG. 1 is a diagram illustrating a network topology advertisement operation

according to a related art; FIG. 2 is a diagram illustrating a neighbor base station scanning operation

according to a related art;

FIG. 3 is a diagram illustrating a handover initiation operation according to a

related art;

FIG. 4 is an exemplary operational flow diagram of a neighbor base station

information transmission method according to a first embodiment of the present

invention;

FIG. 5 is an exemplary operational flow diagram of the first-embodiment

method applying a management function server;

FIG. 6 is an exemplary operational flow diagram of a neighbor base station

information transmission method according to a second embodiment of the present

invention;

FIG. 7 is an exemplary operational flow diagram of the second-embodiment

method applying a management function server;

FIG. 8 is an exemplary operational flow diagram of a neighbor base station

information transmission method according to a third embodiment of the present

invention; and

FIG. 9 is an exemplary operational flow diagram of the third-embodiment method applying a management function server;.

Best Mode for Carrying Out the Invention

Reference will now be made in detail to the preferred embodiments of the

present invention, examples of which are illustrated in the accompanying drawings.

In the embodiments of the present invention, to provide neighbor base station

information in such a mobile communication system as a broadband wireless access

system, a serving base station directly obtains information of at least one neighbor base

station from the at least one neighbor base station over a backbone network. The

serving base station transmits the information of the neighbor base stations to at least

one mobile subscriber station belonging to the serving base station. Hence, the at least

one mobile subscriber station can use the information of the at least one neighbor base

station for a specific purpose.

The serving base station directly obtains physical channel information of the

neighbor base stations from the neighbor base stations over the backbone network via

inter-base station control messages. The serving base station periodically transmits the

obtained physical channel information to the at least one mobile subscriber station

belonging to a governing domain of the serving base station. The at least one mobile

subscriber station uses the obtained physical channel information in measuring a signal

quality of the at least one neighbor base station.

The neighbor base station information contains a base station identifier, physical

frequency, uplink channel descriptor (UCD), and downlink channel descriptor (DCD). As mentioned in the foregoing description, the serving base station exchanges the inter-

base station control messages with the at least one neighbor base station to obtain the

information of the at least one neighbor base station.

The information of the at least one neighbor base station is transmitted to the at

least one mobile subscriber station belonging to the governing domain of the serving

base station from the serving base station via a message. The information of the at least

one neighbor base station is periodically transmitted to the at least one mobile

subscriber station via the message. The at least one mobile subscriber station uses the

information of the at least one neighbor station transmitted via the message to identify a

network and to define characteristics of the at least one neighbor base station to an

influential initial network entry for which the at least one mobile subscriber station is

looking. The at least one mobile subscriber station uses the information transmitted via

the message for a handover to a target base station among the neighbor base stations

from the serving base station. Each of the neighbor base stations is capable of transmitting its information to

the serving base station and other neighbor base stations whenever its information

change occurs. Each of the neighbor base stations is capable of transmitting its

information periodically to the serving base station and other neighbor base stations.

Meanwhile, the at least one mobile subscriber station is facilitated to tune a sync with

the at least one neighbor base station, without monitoring a transmission from a target

base station among the neighbor base stations, for downlink channel description

broadcast and uplink channel description broadcast using the information of the neighbor base stations.

The inter-base station control messages include a base station information

request message transmitted to request the neighbor base station information to the at

least one neighbor base station from the serving base station and a base station

information response message transmitted from each of the neighbor base stations to the

serving base station and other neighbor base stations in response to the base station

information request message.

The base station information request is a message describing a variety of

parameters according to respectively allocated fields and includes an 8-bit message-type

field, a 48-bit sender base station identifier, a 48-bit target base station identifier, a

security field for authenticating the message, and a 32-bit error correction field. The

error correction preferably uses a cyclic redundancy check (CRC) code. The base

station information request message can be transmitted to the at least one neighbor base

station from the serving base station via a server. The base station information response is a message describing a variety of

parameters according to respectively allocated fields and includes an 8-bit message type

physical frequency, a configuration change count incremented in case of each change of

information for a base station, a hysteresis threshold, a mobile-assisted handover

(MAHO) report period, type length value (TLV) encoded information, a security field,

and a 32-bit error correction (CRC) field. The base station information response

message can be transmitted from the at least one neighbor base station to the serving base station via a server. The neighbor base station information includes a downlink

center frequency, an uplink channel descriptor, and a downlink channel descriptor.

As mentioned in the foregoing description, the serving base station, which is

providing a service, gives and takes parameters included in the network topology

advertisement via the inter-base station control messages with the neighbor base stations.

In doing so, the inter-base station control messages used in the embodiments of the

present invention are classified into the base station information request message

requesting the information of the corresponding neighbor base station and the base

station information response message by which each of the base stations having

received the base station information request message delivers its information to the

requesting base station, i.e., the serving base station.

Table 1 shows an example of the base station information request message.

Table 1

Table 2 shows an example of the base station information response message. Table 2

The base stations directly give and take the control messages between themselves to share the information associated with their physical channel characteristics via the inter-base station control messages. Alternatively, the base stations operate a management function server between themselves to mutually obtain the information of the neighbor base stations via the management function server.

First Embodiment

In a method according to a first embodiment of the present invention, a serving

base station transmits a base station information request message to neighbor base

stations and receives a base station information response message from each of the

neighbor base stations to update information of the neighbor base stations.

The method according to the first embodiment of the present invention includes

the steps of initializing a serving base station, allowing the serving base station to obtain

information of neighbor base stations by exchanging inter-base station control messages

between the serving base station and the neighbor base stations over a backbone

network, performing an initialization and registration process between the serving base

station and mobile subscriber stations belonging to a governing domain of the serving

base station, delivering the information of the neighbor base stations to the mobile

subscriber stations from the serving base station via a message, and periodically

performing the step of obtaining the information of the neighbor base stations to deliver

the periodically obtained information of the neighbor base stations to the mobile

subscriber stations from the serving base station and to update the information of the

neighbor base stations periodically.

The inter-base station control messages include a base station information

request message transmitted to request the information of the neighbor base stations to

the neighbor base stations from the serving base station and a base station information

response message transmitted from each of the neighbor base stations to the serving base station in response to the base station information request message.

FIG. 4 is a flowchart of a neighbor base station information transmission method

according to a first embodiment of the present invention.

Referring to FIG. 4, a serving base station performs an initialization process

(S411) and then requests base station information from neighbor base stations, i.e., base

stations 1 and 2 (S412, S413). Base stations 1 and 2 each transmit information

including its physical channel characteristics to the serving base station in response to

the neighbor base station information request (S414, S415).

Meanwhile, a mobile subscriber station performs an initialization and

registration process for the serving base station (S416) and receives the information of

the neighbor base stations from the serving base station (S417). The information of the

neighbor base stations transmitted from the serving base station can be commonly

transmitted to all mobile subscriber stations existing within a corresponding cell via a

broadcast control message such as a neighbor advertisement (MOB NBR-ADV)

message, which will hereinafter be explained in detail.

Base stations supporting mobile functionality shall be capable of transmitting a

MOB_NBR-ADV management message at a periodic interval (MOB_NBR-ADV

interval) to identify the network and to define the characteristics of neighbor base

station to potential mobile subscriber station seeking initial network entry or handover.

If neighbor information is unavailable, this message need not be transmitted.

The neighbor advertisement message is a message describing a variety of

parameters according to respectively allocated fields and includes an 8-bit management message type field, a 24-bit operator identifier, a 7-bit N_neighbors field, a 32-bit

physical frequency field, an 8-bit length field, an 8-bit configuration change count, a 24-

bit neighbor base station identifier, an 8-bit hysteresis threshold field, an 8-bit physical

(PHY) profile identifier, an 8-bit frequency assignment index, an 8-bit base station

equivalent isotropic radiated power (EIRP) field, an 8-bit preamble index/subchannel

index, a 4-bit DCD configuration change count, a 4-bit UCD configuration change

count, and TLV encoded neighbor information.

The operator identifier is the unique network identifier shared by an association

of base stations. This field is present only if bit 0 of skip-optional-fields bitmap has a

value of "0". The N_neighbors is the count of the unique combination of neighbor base

station identifier, preamble index, and downlink channel descriptor. The configuration

change count is incremented each time the information for the associated neighbor base

station has changed. The neighbor base station identifier is an optional field, i.e.,

omitted for a skip-optional-fields flag value of "1," for an orthogonal frequency division

multiple access (OFDMA) PHY layer. That is, the least significant 24 bits of the base

station identifier is included in the DL-MAP message of the neighbor base station. This

field is present only if bit 1 of skip-optional-fields bitmap is "0."

The length field indicates the length, in bytes, of message information within the

iteration of N_Neighbor. The PHY profile identifier is an aggregation of the co-located

frequency assignment indicator, frequency assignment configuration indicator, fast

Fourier transform (FFT) size, bandwidth, operation mode (of the starting sub-

channelization of a frame), and channel number. In more detail, the PHY profile identifier is an aggregate identifier including the co-located frequency assignment

indicator bit, the frequency assignment configuration indicator bit, time/frequency

synchronization indicator, base station EIRP indicator, DCD/UCD reference indicator,

frequency assignment index indicator, and the frequency assignment number. If the co-

located frequency assignment indicator bit is set, the following field of the NBR-ADV

element, which includes a preamble index, handover process optimization, DCD UCD

configuration change count, and TLV-encoded neighbor information, may be omitted.

The frequency assignment index field is present only if the frequency

assignment index indicator in PHY profile identifier is set. Otherwise, the neighbor

base station has the same frequency assignment index or the center frequency is

indicated using the TLV encoded information. If the frequency assignment index

Indicator bit in the PHY profile identifier is set to "1," the frequency assignment index

follows the PHY profile identifier. In addition, if the frequency assignment indicator is

followed, the downlink center frequency shall be determined by a service provider or a

governmental body (e.g., the FCC). The base station EIRP is a signed integer form

from -128dBm to +127dBm. This field is present only if the base station EIRP

indicator is set in the PHY profile identifier. Otherwise, the base station has the same

EIRP as the serving base station. The neighbor base station EIRP is listed in a signed

integer form from -128dBm to +127dBm. This field shall be omitted if the base station

EIRP indicator bit in the PHY profile identifier is set to "0."

The preamble index/subchannel index parameter defines the PHY specific

preamble for the SCa (signal carrier access below 11GHz) and OFDMA PHY. For the OFDMA PHY, the five least significant bits contain the active downlink subchannel

index used in the advertised base station sector. The three most significant bits shall be

reserved and set to "ObOOO." The DCD configuration change count is represented by the

four least significant bits of the current DCD configuration change count of the

neighbor base station. The UCD configuration change count is represented by the four

least significant bits of the current UCD configuration change count of the neighbor

base station.

The TLV encoded neighbor information may include TLV parameters, DCD

settings, UCD settings, and a PHY mode identifier. The DCD settings is a compound TLV value that encapsulates a DCD message

that may be transmitted in the advertised base station downlink channel. This

information is intended to enable fast synchronization of the mobile subscriber station

with the advertised base station downlink. The DCD settings fields shall contain only

neighbor's DCD TLV values that are different from the serving base station

corresponding values. The mobile base station assumes that all excluded values are

identical to the corresponding values of the serving base station. The duplicate TLV

encoding parameters within a neighbor base station are excluded from DCD settings.

The UCD settings is a compound TLV value that encapsulates a UCD message

that may be transmitted in the advertised base station downlink channel. This

with the advertised base station uplink. The DCD settings fields shall contain only

neighbor's UCD TLV values that are different from the serving base station's corresponding values. For values that are not included, the mobile subscriber station

shall assume they are identical to the corresponding values of the serving base station.

The duplicate TLV encoding parameters within a neighbor base station shall not be

included in UCD settings. The PHY mode identifier is a sixteen-bit value that specifies the PHY

parameters, including channel bandwidth, FFT size, cyclic prefix, and frame duration.

The bit-by-bit definition of the PHY profile identifier of the base station will be

explained hereinafter. The co-located frequency assignment indicator bit has one bit,

the frequency assignment configuration indicator has one bit, the time/frequency

synchronization indicator has two bits, the base station EIRP indicator has one bit, the

DCD/UCD reference indicator has one bit, and the frequency assignment index

indicator has one bit.

The co-located frequency assignment indicator bit is set to "1" if the base station

(or frequency assignment) is co-located with the serving base station. When the

frequency assignment configuration indicator bit is set to "1," the base station has the

same frequency assignment configuration, i.e., the same number of frequency

assignments having the same frequencies, as the base station broadcasts the NBR-ADV

message. The time/frequency synchronization indicator value is set to "00" to indicate

an unsynchronized condition, is set to "01" to indicate time synchronization, and is set

to "10" to indicate time and frequency synchronization. If the time synchronization is

indicated for the OFDMA PHY, then the downlink frames transmitted by the serving

base station and the neighbor base station shall be synchronized to a level of at least 1/8 cyclic prefix length. If the frequency synchronization is indicated for the OFDMA PHY,

then the base station reference clock shall be synchronized to a level that yields RF

center frequency offset of no more than 4% of the OFDMA carrier spacing of the

neighbor base station. If the base station EIRP indicator bit (one bit) is "1," the base station EIRP

follows the PHY profile identifier. If the DCD/UCD reference indicator bit (one bit) is

set to "1," the DCD/UCD settings of the neighbor base station are the same as those of

the preceding neighbor base station unless the TLV information is specified. If the

DCD/UCD reference indicator bit (one bit) is set to "0," the DCD/UCD settings of the

neighbor base station are the same as those of the serving base station unless the TLV

information is specified. Only if the frequency assignment index indicator (one bit) is

set to "1," the frequency assignment index follows the PHY profile identifier. In

addition, if the frequency assignment indicator is followed, the downlink center

frequency shall be omitted in the DCD/UCD difference TLV information. One bit may

be reserved for future use.

For OFDMA PHY, the physical mode identifier has fields such as channel

bandwidth (seven bits), FFT size (three bits), cyclic prefix (two bits), and frame

duration code (four bits). The channel bandwidth is a bandwidth expressed in units of

125Khz. Regarding the FFT size (three bits), a value of "ObOl l" indicates a size of 256.

Values ObOOO-ObOlO and ObOlOO-Obl 11 are reserved. Regarding the cyclic prefix (two

bits), "00," "01," "10," and "11" indicate cyclic prefixes of 1/4, 1/8, 1/16, and 1/32,

respectively. Regarding the frame duration code (four bits), values of "0000," "0001," "0010," "0011," "0100," "0101," "0110," and "0111-1111" indicate durations of 2.5ms,

4ms, 5ms, 8ms, 10ms, 12.5ms, 20ms, and "reserved," respectively.

The above procedure of the first embodiment as shown in FIG. 4 can be

periodically performed. Namely, the serving base station sends a base station

information request to each neighbor base station at a periodic interval T2, and the base

station information received in response is transmitted to the mobile subscriber station

at a periodic interval TI.

The first embodiment may be achieved by a direct transfer of the inter-base

station control messages as shown in FIG. 4. As an alternative, a management function

server may be applied as shown in FIG. 5.

Referring to FIG. 5, the neighbor base station information transmission method

using a management function server includes the steps of initializing a serving base

station; allowing the serving base station to obtain information of neighbor base stations

by exchanging inter-base station control messages between the serving base stations and

the neighbor base stations over a backbone network via a server, i.e., the management

function server; performing an initialization and registration process between the

serving base station and mobile subscriber stations connected to the serving base

station; delivering the information of the neighbor base stations to the mobile subscriber

stations from the serving base station via a message; and periodically performing the

step of obtaining the information of the neighbor base stations to deliver the periodically

obtained information of the neighbor base stations to the mobile subscriber stations

from the serving base station and to update the information of the neighbor base stations periodically.

The inter-base station control messages include a first base station information

request message transmitted from the serving base station, to request the information of

the neighbor base stations from the server, a second base station information request

message transmitted from the server to the neighbor base stations according to the first

base station information request message, a first base station information response

message transmitted from each of the neighbor base stations to the server in response to

the second base station information request message, and a second base station

information response message transmitted to the serving base station from the server. Referring to FIG. 5, the serving base station performs the initialization process

(S511) and then requests the information of the neighbor base stations from the

management function server (S512). If so, the management function server requests

base station information from the neighbor base stations, i.e., base stations 1 and 2

(S513, S514), and receives information containing physical channel characteristics of

the corresponding neighbor base station from each of the neighbor base stations (S515,

S516). In response to the neighbor base station information request of the step S512

from the serving base station, the management function server transmits the information

of the neighbor base stations to the serving base station (S517).

Meanwhile, the mobile subscriber station performs an initialization and

registration process on the serving base station (S518) and receives the information of

the neighbor base stations from the serving base station (S519). The information of the

neighbor base stations transmitted from the serving base station can be commonly transmitted to all mobile subscriber stations existing within a corresponding cell via a

broadcast control message.

The above procedure, as shown in FIG. 5, can be periodically performed.

Namely, the serving base station requests the base station information to the neighbor

base stations at a periodic interval T2 and transmits the base station information

received from the neighbor base stations to the mobile subscriber station at a periodic

interval TI.

Second Embodiment

A second embodiment of the present invention relates to a method of updating

information of neighbor base stations by periodically receiving base station information

from the neighbor base stations at a periodic interval without a request from a serving

base station.

The method according to the second embodiment of the present invention

includes the steps of initializing a serving base station, allowing the serving base station

to obtain information of neighbor base stations by exchanging inter-base station control

messages between the serving base station and the neighbor base stations over a

backbone network, performing an initialization and registration process between the

serving base station and mobile subscriber stations within the serving base station,

delivering the information of the neighbor base stations to the mobile subscriber stations

from the serving base station via a message, and allowing each of the neighbor base

stations to periodically transmit its information to the serving base station via the inter-

base station control message without a request from the serving base station to deliver the periodically obtained information of the neighbor base stations to the mobile

neighbor base stations periodically.

The inter-base station control messages include a base station information

the neighbor base stations from the neighbor base stations, and a base station

serving base station in response to the base station information request message.

FIG. 6 illustrates a neighbor base station information transmission method

according to a second embodiment of the present invention.

Referring to FIG. 6, a serving base station performs an initialization process

(S611) and then requests base station information from neighbor base stations, i.e., base

stations 1 and 2 (S612, S613). Base stations 1 and 2 each transmit information

the neighbor base station information request (S614, S615).

Meanwhile, a mobile subscriber station belonging to a governing domain of the

serving base station performs an initialization and registration process for the serving

base station (S616) and receives the information of the neighbor base stations from the

serving base station (S617). The information of the neighbor base stations transmitted

from the serving base station can be commonly transmitted to all mobile subscriber

stations existing within a corresponding cell via a broadcast control message.

In the second embodiment of the present invention, the neighbor base stations periodically transmit their information to the serving base station without the

information request of the neighbor base stations made by the serving base station

(S618 to S621).

FIG. 7 illustrates a method using a management function server according to the

second embodiment of the present invention. The method includes the steps of

initializing a serving base station, allowing the serving base station to obtain

between the serving base station and the neighbor base stations over a backbone

network via a server, performing an initialization and registration process between the

stations to periodically transmit an inter-base station control message containing its

information to the serving base station via the server without a request from the serving

base station to deliver the periodically obtained information of the neighbor base

stations to the mobile subscriber stations from the serving base station and to update the

information of the neighbor base stations within the serving base station periodically.

the neighbor base stations from the server; a second base station information request

base station information request message; a first base station information response message transmitted from each of the neighbor base stations to the server in response to

the second base station information request message; and a second base station

information response message transmitted to the serving base station from the server.

Referring to FIG. 7, a serving base station performs an initialization process

(S711) and then transmits requests to a management function server information of

neighbor base stations, i.e., base stations 1 and 2 (S712). If so, the management

function server requests base station information from the neighbor base stations (S713,

S714) and receives information containing their physical channel characteristics from

the neighbor base stations (S715, S716). The management function server transmits the

information of the neighbor base stations to the serving base station in response to the

neighbor base station information request of the step S712 (S717).

Meanwhile, a mobile subscriber station performs an initialization and

registration process for the serving base station (S718) and receives the information of

the neighbor base stations from the serving base station (S719). The information of the

broadcast control message.

In the embodiment shown in FIG. 7, even though the management function

server does not request the base station information to the neighbor base stations, the

neighbor base stations periodically transmit their information to the management

function server (S718, S719). Meanwhile, the management function server, even if the

information of the neighbor base stations is not requested by the serving base station, periodically transmits the information of the neighbor base stations to the serving base

station (S720).

Third Embodiment

A third embodiment of the present invention relates to a method of allowing a

serving base station to update information of neighbor base stations by having each of

the neighbor base stations transmit a message containing its base station information to

the serving base station each time the information of the corresponding neighbor base

station is changed.

The method according to the third embodiment of the present invention includes

between the serving base station and the neighbor base stations over a backbone

subscriber stations from the serving base station via a message, and allowing each of the

neighbor base stations to transmit its information to the serving base station and other

neighbor base stations via the inter-base station control message without a request from

the serving base station each time its base station information is changed wherein the

serving base station delivers the corresponding information to the mobile subscriber

stations each time the changed base station information is received from each of the

neighbor base stations and wherein the serving base station updates the changed base station information of each of the neighbor base stations within the serving base station

itself.

The inter-base station control messages include a base station information

the neighbor base stations from the neighbor base stations, and a base station

FIG. 8 illustrates a neighbor base station information transmission method

according to a third embodiment of the present invention. Referring to FIG. 8, a serving base station performs an initialization process

(S811) and then requests base station information from neighbor base stations, i.e., base

stations 1 and 2 (S812, S813). Base stations 1 and 2 each transmit information

the neighbor base station information request (S814, S815). Meanwhile, a mobile subscriber station performs an initialization and

registration process for the serving base station (S816) and receives the information of

the neighbor base stations from the serving base station (S817). The information of the

broadcast control message. In this case, the broadcast control message has the same

parameters of the message mentioned in the first embodiment of the present invention.

The inter-base station control message has the same parameters of the message mentioned in the first embodiment of the present invention as well.

In the third embodiment of the present invention, each of the neighbor base

stations transmits its information to the serving base station and other neighbor base

stations (S819, S820, S822, S823) in case that its base station information is changed

(S818, S821). The serving base station having received the information of the neighbor

base station transmits the information of the neighbor base stations to the mobile

subscriber stations.

FIG. 9 illustrates a method using a management function server according to the

third embodiment of the present invention. The method includes the steps of initializing

a serving base station, allowing the serving base station to obtain information of

neighbor base stations by exchanging inter-base station control messages between the

serving base station and the neighbor base stations over a backbone network via a server,

performing an initialization and registration process between the serving base station

and mobile subscriber stations within the serving base station, delivering the

information of the neighbor base stations to the mobile subscriber stations from the

serving base station via a message, and allowing each of the neighbor base stations to

deliver the inter-base station control message containing its changed information to the

serving base station via the server without a request from the serving base station each

time its base station information is changed wherein the serving base station delivers the

corresponding information to the mobile subscriber stations each time the changed base

station information is received from each of the neighbor base stations and wherein the

serving base station updates the changed base station information of each of the neighbor base stations within the serving base station itself.

base station information request message; a first base station information response

the second base station information request message; and a second base station

information response message transmitted to the serving base station from the server. Referring to FIG. 9, a serving base station performs an initialization process

(S911) and then requests information of neighbor base stations, i.e., base stations 1 and

2, from a management function server (S912). If so, the management function server

sends a requests base station information to the neighbor base stations (S913, S914) and

receives information containing its physical channel characteristics from each of the

neighbor base stations (S915, S916). The management function server transmits the

neighbor base station information request of the step S912 (S917).

Meanwhile, a mobile subscriber station performs an initialization and

registration process for the serving base station (S918) and receives the information of

the neighbor base stations from the serving base station via a broadcast control message

or the like (9719). The information of the neighbor base stations transmitted from the

serving base station can be commonly transmitted to all mobile subscriber stations existing within a corresponding cell via a broadcast control message.

In the embodiment shown in FIG. 9, in case that information of each of the

neighbor base stations is changed (S920, S924), each of the neighbor base stations

transmits its changed base station information to the management function server (S921,

S925). Meanwhile, the management function server transits the changed base station

information to the serving base station and other neighbor base stations (S922, S923,

S926, S927).

According to the first, second, and third embodiments of the present invention as

described above, the serving base station receives the information of the neighbor base

stations via the inter-base control messages from the neighbor base stations and then

updates the information. The serving base station then provides the information of the

neighbor base stations to the corresponding mobile subscriber stations to enable the

mobile subscriber stations to perform quick handover using the previously received

neighbor base station information. The mobile subscriber station, having received the

information of the neighbor base stations from the serving base station, temporarily

synchronizes with each neighbor base station at predetermined times to measure signal

quality, and then, if necessary, uses the previously received base station information to

execute a handover procedure. That is, the mobile subscriber station uses the neighbor

base station information for a specific purpose, which may be a handover operation

between the first base station and a target base station of the at least one neighbor base

station or an instance of network entry.

In spite of exchanging the information of the mobile subscriber stations between the base stations, the related art fails to provide a technology of allowing the base

stations to exchange their information with each other over the backbone network.

Hence, the parameters contained in the related art control message exchanged between

the base stations are different from those of the present invention. Handover operations are not determined or controlled by the mobile subscriber

stations (e.g., cellular phones) in a 3GPP CDMA mobile communication system, which

instead uses a handover wireless network controller to provide to a mobile subscriber

station, prior to handover, a set of handover parameters corresponding to the target base

station. In the present invention on the other hand, the mobile subscriber station itself

determines and controls a handover operation, which is enabled by updated neighbor

base station information being communicated in advance, so that signal quality with

respect to the target base station may be measured for performing a handover operation

or for network entry. The present invention may be less applicable in 3 GPP CDMA

mobile communications due to cellular telephone power limitations and is more

applicable to the mobile subscriber station of a portable wireless internet system using

mobile terminals having higher power capacities.

It will be apparent to those skilled in the art that various modifications and

variations can be made in the present invention. Thus, it is intended that the present

invention covers the modifications and variations of this invention provided they come

within the scope of the appended claims and their equivalents.

Industrial Applicability The present invention can be applicable to wireless communication systems.

Claims

[CLAIMS]

1. A method of communicating neighbor base station information in a

mobile communication system, the method comprising: obtaining, at a first base station, neighbor base station information from

at least one neighbor base station, the neighbor base station information corresponding

to the at least one neighbor base station and being provided to the first base station over

a backbone network; and transmitting the obtained neighbor base station information from the first

base station to a mobile subscriber station connected to the first base station.

2. The method of claim 1, wherein the mobile subscriber station uses the

neighbor base station information for a specific purpose.

3. The method of claim 2, wherein the specific purpose corresponds to a

handover operation between the first base station and a target base station of the at least

one neighbor base station.

4. The method of claim 2, wherein the specific purpose corresponds to an

instance of network entry.

5. The method of claim 1, wherein the neighbor base station information

includes physical channel information for connecting to the at least one neighbor base

station.

6. The method of claim 1, wherein the neighbor base station information

includes a base station identifier, physical frequency information, an uplink channel

descriptor, and a downlink channel descriptor.

7. The method of claim 1, wherein the mobile communication system is a

broadband wireless access system.

8. The method of claim 1, wherein the first base station is a serving base

station.

9. The method of claim 1, wherein the first base station obtains the

neighbor base station information by exchanging with the at least one neighbor base

station a plurality of inter-base station control messages over the backbone network.

10. The method of claim 9, wherein the plurality of inter-base station control messages include a base station information request for requesting the neighbor base

station information and a base station information response responsive to the base

station information request, the base station information request being transmitted from

the serving base station to each of the at least one neighbor base station and the base

station information response being transmitted from each neighbor base station to the

serving base station.

11. The method of claim 10, wherein the base station information response is

also transmitted to neighbor base stations other than the at least one neighbor base

station.

12. The method of claim 10, wherein the base station information request

includes respective fields for message type, sender base station identification, target

base station identification, message authentication, and error correction.

13. The method of claim 12, wherein the fields for message type, sender

base station identification, target base station identification, and error correction are

configured with 8 bits, 48 bits, 48 bits, and 32 bits, respectively.

14. The method of claim 10, wherein the base station information request is transmitted, from the first base station to the at least one neighbor base station, via a

server.

15. The method of claim 14, wherein the server is a management function

server.

16. The method of claim 10, wherein the base station information response

base station identification, physical frequency, configuration change count incremented

for each change in neighbor base station information, hysteresis threshold, mobile-

assisted handover report period, type-length-value-encoded information, message

authentication, and error correction.

17. The method of claim 16, wherein the fields for message type, sender

configured with 8 bits, 48 bits, 48 bits, and 32 bits, respectively.

18. The method of claim 10, wherein the base station information response is

transmitted, from the first base station to the at least one neighbor base station, via a

server.

19. The method of claim 18, wherein the server is a management function

server.

20. The method of claim 1, wherein the neighbor base station information

includes downlink center frequency information, an uplink channel descriptor, and a

downlink channel descriptor.

21. The method of claim 1, wherein the neighbor base station information is

included in a message periodically transmitted to the mobile subscriber station.

22. The method of claim 21, wherein the mobile subscriber station uses the

message containing the neighbor base station information to identify a network and

characteristics of the at least one neighbor base station for an instance of network entry.

23. The method of claim 1, wherein the neighbor base station information is

transmitted, for each change in the neighbor base station information, from the at least

one neighbor base station to the first base station and to neighbor base stations other

than the at least one neighbor base station.

24. The method of claim 1, wherein the neighbor base station information is

periodically transmitted, for each change in the neighbor base station information, from

the at least one neighbor base station to the first base station and to neighbor base

stations other than the at least one neighbor base station.

25. The method of claim 1, wherein the at least one mobile subscriber station

uses the neighbor base station information to synchronize with the at least one neighbor

base station.

26. The method of claim 25, wherein the synchronization is performed

without monitoring downlink/uplink channel descriptor broadcast transmissions from a

target base station of the at least one neighbor base station.

27. A method of communicating neighbor base station information in a

mobile communication system, the method comprising: obtaining, at a serving base station, physical channel information exchanged

over a backbone network using a plurality of inter-base station control messages, the

physical channel information corresponding to at least one neighbor base station; periodically transmitting the obtained physical channel information from the

serving base station to a mobile subscriber station connected to the serving base station, the obtained physical channel information being updated for each transmission; and measuring, based on the updated physical channel information, signal quality of

the at least one neighbor base station at the mobile subscriber station.

28. The method of claim 27, wherein the inter-base station control messages

include a base station information request for requesting neighbor base station

information and a base station information response responsive to the base station

information request, the base station information request being transmitted from the

serving base station to the at least one neighbor base station and the base station

information response being transmitted from each of the at least one neighbor base

station to the serving base station.

29. The method of claim 28, wherein the base station information response is

station.

30. The method of claim 27, wherein the inter-base station control messages

are exchanged directly between the serving base station and the at least one neighbor

base station.

31. The method of claim 27, wherein the inter-base station control messages

are exchanged via a server functionally interposed between the serving base station and

the at least one neighbor base station.

32. The method of claim 31, wherein the inter-base station control messages

are exchanged between the server and each of the at least one neighbor base station.

33. The method of claim 27, wherein the physical channel information is

updated in the serving base station.

34. The method of claim 33, wherein the physical channel information is

updated in the at least one neighbor base station.

35. The method of claim 27, wherein the physical channel information is

updated by the serving base station periodically requesting updated information from

the at least one neighbor base station via the inter-base station control messages.

36. The method of claim 35, wherein the at least one neighbor base station

transmits the updated information to the serving base station in response to the request.

37. The method of claim 27, wherein the physical channel information is

updated by transmitting neighbor base station information from the at least one

neighbor base station to the serving base station.

38. The method of claim 37, wherein the neighbor base station information

is transmitted for each change in the physical channel information of the at least one

neighbor base station.

39. A method of communicating neighbor base station information in a

mobile communication system, the method comprising: performing an initialization and registration process between a serving

base station and a mobile subscriber station connected to the serving base station; obtaining, at the serving base station, neighbor base station information

by exchanging inter-base station control messages over a backbone network between

the serving base station and at least one neighbor base station; and updating the neighbor base station information, by periodically

performing said neighbor base station information obtaining and transmitting to the

mobile subscriber station the periodically obtained information from the serving base

station.

40. The method of claim 39, wherein the inter-base station control messages

base station.

41. The method of claim 40, wherein the inter-base station control messages

include a base station information request for requesting neighbor base station

station to the serving base station.

42. The method of claim 39, wherein the inter-base station control messages

are exchanged via a server.

43. The method of claim 42, wherein the inter-base station control messages

include a first base station information request, transmitted from the serving base station

to the server, for requesting the neighbor base station information; a second base station

information request transmitted from the server to the at least one neighbor base station

according to the first base station information request, a first base station information response transmitted from the at least one neighbor base station to the server in response

to the second base station information request; and a second base station information

response message transmitted from the server to the serving base station according to

the second base station information response.

44. The method of claim 42, wherein the server is a management function

server.

45. A method of communicating neighbor base station information in a

station, said updating being continuously performed according to a completion of the

initialization and registration process.

46. The method of claim 45, wherein the inter-base station control messages

base station.

47. The method of claim 46, wherein the inter-base station control messages

include a base station information request for requesting neighbor base station

station to the serving base station.

48. The method of claim 45, wherein the inter-base station control messages

are exchanged via a server.

49. The method of claim 48, wherein the inter-base station control messages

information request transmitted from the server to the at least one neighbor base station according to the first base station information request, a first base station information

response transmitted from the at least one neighbor base station to the server in response

the second base station information response.

50. The method of claim 48, wherein the server is a management function

server.

51. A method of communicating neighbor base station information in a

performing said neighbor base station information obtaining for each change in the

neighbor base station information and transmitting to the mobile subscriber station the

periodically obtained information from the serving base station, said updating being continuously performed according to a completion of the initialization and registration

process..

52. The method of claim 51, wherein the serving base station transmits the

updated neighbor base station information to the mobile subscriber station for each

transmission of a change in the neighbor base station information is received from any

one of the at least one neighbor base station.

53. The method of claim 52, wherein the neighbor base station information

is updated in the serving base station.

54. The method of claim 53, wherein the neighbor base station information

is updated in the at least one neighbor base station.

55. The method of claim 51, wherein the inter-base station control messages

base station.

56. The method of claim 55, wherein the inter-base station control messages

include a base station information request for requesting neighbor base station information and a base station information response responsive to the base station

station to the serving base station.

57. The method of claim 51, wherein the inter-base station control messages

are exchanged via a server.

58. The method of claim 57, wherein the inter-base station control messages

according to the first base station information request, a first base station information

the second base station information response.

59. The method of claim 57, wherein the server is a management function

server.