Title of Invention

A METHOD OF CONFIGURING AN IP ADDRESS OF A TERMINAL IN A BROADBAND WIRELESS ACCESS SYSTEM

Abstract This invention is a method for configuring an IP address of fixed/mobile station in a broadband wireless access system. A method of configuring an IP address of a terminal in a broadband wireless access system is disclosed. The base station determines whether the mobile station that changes from idle mode to receiving mode or performs handover needs to re-configure its IP address, and informs this to the mobile station. So, IP address configuration procedures are simplified between the base station and the mobile station.
Full Text Description
Technical Field
[1] The present invention relates to broadband (wideband) wireless (radio) access
systems, in particular, to a method of simplifying the IP address configuration
(establishment) procedures when a mobile/fixed terminal in idle mode changes to
receiving mode or when performing handover.
Background Art
[2] In general, in a broadband wireless access system, an idle mode for a mobile (or
fixed) terminal (e.g., mobile station, mobile subscriber station (MSS), user terminal,
user equipment (UE), etc.) is supported in order to minimize power consumption. In
idle mode, a 'paging zone' is defined as the entire region that is handled by a plurality
of bases station called a 'paging group' and all base station included within the same
paging zone have the same paging cycle value (Paging_Cycle) and paging offset value
(Paging_Offset).
[3] The terminal may request to the base station for changing into idle mode, and the
base station delivers its paging zone identification (Paging-group ID) and the paging
cycle and paging offset associated thereto to the terminal to allow that terminal to
change into idle mode state. During the idle mode, the terminal can determine whether
to maintain or end its idle mode based upon the paging that is delivered in broadcast
format from the base station at each paging period.
[4] Additionally, when there is traffic (e.g., data, packets, etc.) that needs to be
delivered by the terminal in idle mode, the terminal may end its idle mode at any time.
Also, when a terminal in idle mode does not receive paging within a set period of time
due to reasons such as moving into another paging zone, losing synchronization, etc.,
then the terminal ends its idle mode.
[5] When data traffic to be delivered to me terminal in idle mode is generated, the base
station can make me terminal end its idle mode through paging. In such situations
when traffic to be forwarded is generated for the terminal, the base station delivers an
action code to enter network.
[6] In mis situation or when the terminal has data to be sent on the uplink, die terminal
performs IP address configuration (establishment) procedures. If the network prefix
used by the base station that received the paging did not change and remains the same,
the above procedures could be omitted, but such omission is not possible because a
procedure for performing network prefix comparison is not provided by the related art.

[7] The idle mode can be comprised of the following operations and steps.
[8] - start idle mode by mobile terminal
[9] - cell selection
[10] - synchronization of paging message broadcast time of terminal
[11] - terminal paging unavailable cycle
[12] - terminal paging listening period
[13] - base station paging broadcast message transmission period
[14] - base station broadcast message
[15] - end paging available mode
[16] Among these, the technique related to the present invention is the base station
paging broadcast message.
[17] The base station paging broadcast message is a message sent via the base station or
a different network element for informing a particular mobile terminal that currently
delayed downlink traffic exists. This paging broadcast message must be transmitted
through a broadcast connection identifier (CID) during a base station paging broadcast
message transmission time period, and should be transmitted during the transmission
time period regardless of the number of mobile terminals that require paging.
[18] The base station paging broadcast message should be able to include one or more
paging group IDs mat indicate the logical classification of the base station that
transmits. Regarding the base station paging broadcast message, the mobile terminals
are distinguished by the mobile terminal MAC address hash, and a single base station
paging broadcast message can include a plurality of MAC addresses.
[ 19] The base station paging broadcast message must transmit an action code with
respect to each mobile terminal that is distinguished by mobile terminal MAC address
hashes, and such action codes are as follows.
[20] - 00: no action required
[21] - 01: perform Ranging to configure location and acknowledge message
[22] -10: perform initial network entry
[23] -11: reserved
[24] Among the above action codes, the base station paging broadcast message that is
transmitted when there is downlink data, transmits an action code '10' and the terminal
performs network entry procedures based upon mis action code.
[25] Accordingly, in the related art, the mobile terminal must always re-configure
(re-establish) its IP address when the mobile terminal in idle mode receives paging
from the base station because there is downlink data to be received or when there is
uplink data to be sent
[26]- Namely, when a mobile terminal operating in idle mode moves into a different base
station region and receives from the base station a paging broadcast message indicating

that currently set aside (delayed) downlink data exists, the mobile terminal may omit
the IP address configuration (establishment) procedures if the IP Subnet, Prefix, and
Access Router (NetID) used by the base station are the same as those previously used
by the mobile terminal. Also, when the mobile terminal in idle mode performs reg-
istration procedures with the base station because it has data to be sent on the uplink,
the base station compares the previously received IP Subnet, Prefix, and Access Router
(NetID) used by the mobile terminal with the IP Subnet, Prefix, and Access Router
(NetID) that are can be used or are currently being used within die base station, and
informs to the mobile station as to whether IP address re-configuration
(re-establishment) is needed or not.
[27] However, because the related art does not provide the procedures that can compare
the IP Subnet, Prefix, and Access Router (NetID), the mobile terminal had to perform
IP address configuration (establishment) procedures each time the idle mode was
ended when there was uplink or downlink data, thus causing the problems of un-
necessary time delays.
[28] Meanwhile, the process for handover in a broadband wireless access system
comprises a pre-processing procedure, a handover procedure, and a 'drops and
corrupted HO attempts' procedure.
[29] 1. Pre-processing procedures for handover
[30] As the pre-processing procedures for handover of IEEE 802.16e, a procedure of
informing the mobile terminals by broadcasting from a base station, the information
related to neighboring base stations (e.g., Network Topology Advertisement), a
procedure of measuring the channel quality of neighboring base stations based upon
such information (e.g„ MSS scanning of neighbor BS), and a procedure of selectively
matching time differences and the like for the neighboring base station and initial
terminal power value, as well as for synchronization (e.g., association procedures).
[31] * Network Topology Advertisement
[32] The base station informs all mobile stations within a cell about the information of
neighboring base stations by transmitting information related to network constitution
information in a broadcasting manner through a MOBJ^JBR-ADV MAC (Medium
Access Control) message.
[33] * MSS scanning of neighbor BS
[34] As a mobile terminal must scan (search) neighboring base stations for handover, a
scanning interval is requested to the base station through a MOB_SCN-REQ MAC
message for scanning neighbor base stations, and the base station transmits a
MOB_SCN-RSP MAC message in response to allocate an interval that allows the
terminal to scan neighboring base stations. Also, the base station may directly transmit
a MOB_SCN_RSP MAC message without any request of the mobile terminal (i.e., un-

solicited request). At this time, the scanning interval and offset unit to start scanning
that the base station allocates are all allocated in units of frames.
[35] * Association Procedure
[36] The association procedure is a procedure in which the terminal normally joins a cell
by performing a ranging procedure with the base station. The associate procedure is
performed when the terminal scans the base stations and selects a new base station. A
RNG-REQ MAC message is transmitted by the terminal, and the base station transmits
a RNG-RSP MAC message to set the power offset value, timing offset value, etc. to
the appropriate values.
[37] Transmitting of the RNG-REQ MAC message is referred to as an initial ranging
operation, and is one of the most basic operations of an IEEE 802.16 system by which
the terminal performs a network entry process. The target base station that receives a
new terminal through handover (HO), transmits the matters in association to the cell of
the terminal to the serving base station that the terminal was previously a part of, and
then stores the information related to the terminal.
[38] 2. Handover (HO) Process
[39] Based upon the neighboring base station and channel'quality information obtained
from the above handover pre-processing procedures, the terminal begins handover.
[40] * Cell Selection
[41] The cell selection operation is an operation of changing a cell in order to newly
register with a base station that allows reception of a signal having a better Signal-
to-Interference-Noise Ratio (SINR) than me SINR of the signal transmitted from the
base station of a current cell before the terminal normally registers with the cell At this
time, the base station has no way of knowing about any movement of the terminal
because the terminal has not yet performed any registration procedures.
[42] * HO Initiation
[43] Handover initiation can be performed by either the base station (BS) or the mobile
terminal (MSS: mobile subscriber station). Namely, when the base station requests
handover, it transmits a MOB_BSHO-REQ MAC message, and when the mobile
terminal requests handover, it transmits a MOB_MSSHO-REQ MAC message. If the
terminal transmits a MOB_MSSHO-REQ MAC message, the SINR of the signals
received from neighboring base stations is transmitted to the base station, and the
candidate base stations that can be a target base station during handover are transmitted
to the currendy serving base station.
[44] The base station receives a MOB_MSSHO-REQ MAC message from the terminal
or before the base station itself transmits a MOB_MSSHO-REQ MAC message in
order to handover the terminal, the handover of the terminal is allowed after checking
the responses (ACK) from neighboring base stations for performing handover of the

particular terminal. The terminal or base station that receives the
MOB_BSHO/MSSHO-REQ message transmits a MOB_MSSHO/BSHO-RSP MAC
message to inform about the target base station that will perform the handover.
[45] * HO Cancellation
[46] After the MOBJMSSHO/BSHO-REQ MAC message is transmitted to allow the
terminal or base station to perform handover, the terminal may cancel the handover.
Here, the terminal can set a particular field of the MOB_HO-IND MAC message (e.g.,
HO_Type=01) and transmit such to the base station for canceling the handover that is
currently being performed.
[47] * Termination with the Serving BS
[48] By transmitting a MOB_HO-IND MAC message to the serving base station, the
terminal informs that handover has been properly completed and finishes the handover
operation. Here, the terminal can set a particular field of the M0B_HO-IND MAC
message (e.g., HO_Type=00) and transmit such to the serving base station to inform
that handover has been properly completed. Upon receiving the MOB_HO-IND MAC
message from the terminal, the base station terminates the MAC state machine, ARQ
connection, and all connections related to data transmission that were allocated the
terminal that has been handed over.
[49] * HO Rejection
[50] The terminal may reject the handover recommended by the base station, and does
so by setting a particular field of the MOB_HO-IND MAC message (e.g.,
HO_Type=10) and transmits to the base station. Upon receiving a rejection message
from the terminal, the base station re-constitutes the target base stations and re-
transmits a MOB_BSHO-RSP message to the terminal.
[51] 3. Drops and Corrupted HO Attempts
[52] If the downlink data received from the base station cannot be reconstructed
(recovered, decoded, etc.) or if a RNG-RSP MAC message (with respect to a RNG-
REQ MAC message) transmitted to the base station after handover is not properly
received and the limit on the number of times that the RNG-REQ MAC message can
be transmitted to the base station is reached, the terminal terminates communication. In
such case, the terminal re-performs the network entry procedures with the desired
target base station to perform an operation for connection recovery.
[53] * Re-entry with the Target BS
[54] The terminal that performed handover performs a new network entry operation with
the target base station, and also performs handover procedures for re-entry with
neighboring base stations as well. However, from the point of view of the base station,
the re-entry is performed in the same manner as a regular network entry procedure.
[55] * Synchronization with Downlink and Obtain Parameters

[56] The terminal that performed handover detects the downlink signal of the target base
station to form synchronization with the base station, and receives a MOB_NBR-ADV
MAC message transmitted by the base station to determine the conditions of
neighboring base stations. Also, the terminal performs the same procedures as in a
regular network entry procedure, namely, the operations to receive the DL_MAP and
DCD message are performed.
[57] * Obtain Uplink Parameters
[58] The terminal that performed handover, after obtaining the downlink parameters as
described above, receives uplink parameters through reception of a UL_MAP MAC
message, a UCD message, etc.
[59] * Ranging and Uplink Parameters Adjustment
[60] The terminal that performed handover attempts to perform ranging with the new
base station. This ranging operation is one of the most basic operations in a IEEE
802.16 system, whereby a ranging operation of a competitive allocation method is
performed through a ranging opportunity (i.e., an interval allowing transmission of a
ranging message) that is allocated by the base station based upon the 48 bit length
MAC address of the terminal itself. Through this ranging operation, the terminal
receives a new basic ID and a primary management ID allocated from the target base
station. This operation achieved as the terminal obtains the uplink parameters by
receiving the Fast_UL_Ranging IE that is transmitted by being inserted into the
UL_MAP MAC message transmitted by the base station.
[61] Here, the ranging opportunity received for the above ranging operation is performed
in a contention-free manner, unlike the initial ranging operation performed for regular
network entry.
[62] * MSS Re-authentication
[63] This is an authentication procedure for normal operation of the terminal, whereby
an authentication procedure occurs by using a PKM (Private Key Management)
protocol, while the existing security context performs the authentication procedure
without any changes.
[64] * Re-register and Re-establish Provisioned Connections
[65] The base station is in a state by which the 48 bit MAC address if the terminal has
already been received, and since the authentication procedure of the terminal was
performed properly, me proper registration procedure of the terminal is performed. The
terminal begins the registration process by transmitting a REG-REQ MAC message,
and the base station transmits a REG-RSP MAC message to re-establish a provisioned
connection of the terminal before handover, to allow proper IP service to be
performed.

Disclosure of Invention
Technical Problem
[66] la general, IP re-configuration (re-establishment) is performed after the mobile
terminal performs handover, and IP re-configuration (re-establishment) need not be
performed if the IP subnet is the same. However, in the related art, this cannot be
known and IP re-configuration (re-establishment) must be done each time the terminal
moves. Namely, even if the previous IP address can be used without having to
configure (establish) an IP address after the terminal performs handover (for example,
when the IP subnet or foreign agent remain the same), IP address configuration
(establishment) is always performed after the mobile terminal moves according to the
related art
Technical Solution
[67] The present invention provides a method of configuring (establishing) an IP address
of a terminal that simplifies the IP address configuration (establishment) procedures
when the terminal in idle mode changed into receiving mode or when handover is
performed.
[68] Instead of having a mobile terminal always perform IP address re-configuration
whenever it is associated with a new point of attachment (e.g., performing handover,
changing from idle mode to receiving mode, etc.), it is determined if IP address re-
configuration is actually necessary by considering whether the previous IP address
may still be used or if a new IP address needs to be configured.
Description of Accompanying Drawings
[69] Figure 1 depicts the format of a registration response message (REG-RSP) applied
. to the mobile station IP address configuration (establishment) method of the present
invention.
[70] Figure 2 depicts the format of a ranging response message (RNG-RSP) used in the
mobile station IP address configuration (establishment) method of the present
invention.
[71] Figure 3 depicts an example of informing whether IP address re-configuration
(re-establishment) is needed, via the registration procedures when idle mode is ended,
because the mobile station in idle mode has downlink (DL) traffic.
[72] Figure 4 depicts an example of Morming whether IP address re-configuratiori
(re-establishment) is needed, via the ranging procedures when idle mode is ended
because the mobile station in idle mode has downlink (DL) traffic.
[73] Figure 5 depicts an example of informing whether IP address re-configuration
(re-establishment) is needed, via the ranging procedures when idle mode is ended
because the mobile station in idle mode has uplink (UL) traffic.

[74] Figure 6 depicts an example of informing whether IP address re-configuration
(re-establishment) is needed, via the registration procedures when idle mode is ended
because the mobile station in idle mode has uplink (UL) traffic.
[75] Figure 7 depicts a format of a handover check message used in the mobile station IP
address configuration (establishment) method of the present invention.
[76] Figure 8 depicts an example of informing the mobile station through a ranging
procedure during handover as to whether its IP address should be re-configured
(re-established).
[77] Figure 9 depicts an example of informing the mobile station through a registration
procedure during handover as to whether its IP address should be re-configured
(re-established).
[78] Figures 10 and 11 depicts an example of how a subnet change can be decided for
the DHCP case, wherein the DHCP server exists on the same network with the MSS.
[79] Figures 12 and 13 depicts an example of how a subnet change can be decided for
the DHCP case, wherein the DHCP server exists on a different network with the MSS.
[80] Figure 14 shows an example of an agent advertisement message according to the
present invention.
Mode for Invention
[81] The preferred exemplary embodiments of the present invention will now be
explained. However, those skilled in the art would understand that the features of the
present invention should not be limited to only the embodiments described herein.
[82] The present invention is related to the research and development being conducted
by various IEEE working groups, such as IEEE 802.16, and thus the concepts and
teachings involved therein are applicable to the features of the present invention. Ad-
ditionally, as various efforts are being made to implement the interworking of different
types of networks and communication technologies, such as achieving compatibility
between IEEE networks and cellular networks (such as, a third generation (3G)
networks), it can be clearly understood that the present invention may also have ap-
plicability in achieving such compatibility.
[83] Considering the communication protocols related to wireless (radio) access
systems, at the network layer, to allow proper data packet communication via the
Internet, an Internet Protocol (IP) provides the necessary addressing and routing in-
formation for the packets. Here, each device (e.g., user terminal, mobile handset,
wireless connectivity device, etc.) connected via the Internet requires the configuration
(establishment) of a unique IP address in order for that device to be properly identified
and distinguished from other devices.
[84] The Internet Protocols referred to as IP version 4 (IPv4) and IP version 6 (IPv6)
have been developed. By employing 32-bit addresses, IPv4 has been found to have

limitations because of the increasing popularity of Internet communications, whereby
each device connected with the Internet needs its own unique IP address. As such, bee
ause the availability of 32-bit addresses would soon be exhausted, an enhancement was
developed, namely, IPv6, which employs 128-bit addresses.
[85] However, the fact that a user terminal may have mobility (e.g., mobile terminals)
makes IP address configuration (establishment) more difficult For example, to support
mobility, a user terminal may undergo handover, whereby the terminal being served by
one point of attachment (e.g., base station) that covers a certain region, moves to a new
location and needs to be served by a different point of attachment (e.g., base station)
that covers that new location. In other words, the mobile station that is part of a first
subnet (i.e., a portion of the network) moves into a second subnet (i.e., another portion
of the network). Another example would be when a user terminal changes its state of
operation into a receiving mode from an idle mode, which is an example of a power-
saving operation mode that is important because a user terminal having mobility
should conserve its limited battery power.
[86] In such handover or idle mode change situations described above, IP address con-
figuration (establishment) must be performed at the appropriate time such that
seamless data reception can be received by the user terminal.
[87] In the related art broadband wireless access systems, regarding the handover
procedures, a so-called 'managed' mobile terminal performs IP address re-
establishment (re-configuration) after a secondary management connection identifier
(CID) is obtained upon completing handover such that IP communications can be
resumed.
[88] When a mobile terminal that moves to a new point of attachment (base station)
region is managed mobile terminal, IP address re-establishment is required regardless'
of the subnet that can be allocated by a foreign agent or by a DHCP server connected
with the new point of attachment (base station). Thus, a basis to be used for de-
termining when IP address re-establishment should be performed is needed. In the
related art, the determination at the IP layer cannot be known at the MAC layer, and
thus the IP address re-establishment cannot be informed to the mobile terminal.
[89] Thus, in (he present invention, the point of attachment (base station) uses the IP
address related information received via a backbone message (or another type of
message), and provides a basis to allow the MAC layer to determine whether the
mobile terminal should perform IP address re-establishment related procedures.
[90] As the MAC layer of the point of attachment (base station) can inform the mobile
terminal as to whether IP address establishment is necessary, the handover procedures
can be simplified and the time delay in resuming communications after handover can
be minimized.

[91] One purpose of the present invention is to provide an IP address configuration
(establishment) method for a terminal wherein the base station (point of attachment)
determines the information related to IP address configuration (establishment) when
the terminal changes from idle mode to receiving mode or when handover is
performed, and informs this to the terminal.
[92] To achieve this purpose in a broadband wireless access system, in the IP address
configuration (establishment) method according to the present invention, the base
station (point of attachment) determines and informs the terminal about whether the IP
address of the terminal should be re-configured (re-established) when the terminal
changes from idle mode to receiving mode or when handover is performed
[93] Preferably, the base station is a target base station to which the terminal is
attempting network entry to.
[94] Preferably, the matter of whether the IP address of the terminal should be re-
configured (re-established) is delivered through a ranging response message or a reg-
istration response message.
[95] Preferably, the base station respectively compares the IP Subnet, Prefix, and
Access Router (NetID) previously used by me terminal with me IP Subnet, Prefix, and
Access Router (NetID) that it may use or is currently using, in order to determine
whether the IP address of the terminal should be re-configured (re-established).
[96] Preferably, if the network prefix ID (NetID) used by the terminal changes, the base
station delivers the changed NetID to the terminal through a ranging response message
or a registration response message.
[97] Preferably, the base station delivers whether the IP address should be re-configured
(re-established) through a ranging response message or a registration response message
only when the network prefix ID (NetID) has changed.
[98] The present invention proposes a scheme in which the DP address establishment
(configuration) procedures can be simplified according to changes (NetID) in the IP
Subnet, Prefix, Access Router, and Foreign Agent being used, when the mobile/fixed
terminal changes from idle mode to receiving mode or when handover is performed.
[99] Namely, the present invention provides a method in which when me terminal
receives a paging message from the base station (point of attachment) indicating that
data to be transmitted on the downlink currently exists or when data to be transmitted
on the uplink exists, the base station determines and informs the terminal as to whether
IP address re-establishment (re-configuration) of the terminal is needed, and allowing
the IP address re-configuration (re-establishment) procedures to be omitted ac-
cordingly. Also, the present invention provides a method in which after the terminal
moves during the handover process, the base station determines and informs the
terminal as to whether IP address re-configuration (re-establishment) of the terminal is

needed, and allowing the IP address re-configuration (re-establishment) procedures to
be omitted accordingly.
[100] First, a method of configuring (establishing) an IP address of the terminal that
changes from idle mode to receiving mode according to a first embodiment of the
present invention will be explained.
[101] In the terminal IP address configuration (establishment) method according to the
first embodiment of the present invention, a registration response message (REG-RSP),
a ranging response message (RNG-RSP), a paging broadcast backbone message, etc,
are defined.
[ 102] The registration response message (REG-RSP) is a message that is transmitted by
setting an IP re-configuration (re-establishment) required bit, when the ID related to th
e terminal IP address received by the new base station (Target BS) from the previous
base station (Serving BS) when the mobile terminal performs registration procedures
after handover, and the ID that is currently being used (or can be used) are compared
and found to be different
[103] The ranging response message (RNG-RSP) is a message that is transmitted by
setting an IP re-configuration (re-establishment) required bit, when the ID related to
the terminal IP address received by the new base station (Target BS) from the previous
base station (Serving BS) when the mobile terminal performs ranging with the new
base station after handover, and the ED that is currently being used (or can be used) are
compared and found to be different
[104] Accordingly, the new base station (Target BS) informs whether the terminal IP
address should be re-configured (re-established) through either the registration
response message (REG-RSP) or the ranging response message (RNG-RSP).
[ 105] The paging broadcast backbone message is a message used when informing the
other base stations within the paging zone about the fact that data traffic to be
transmitted to the mobile terminal arrived at the base station to which the mobile
terminal requested registration release for changing into idle mode, or used when in-
formation about the terminals that changed into idle mode is to be commonly shared by
the base stations within the same paging zone. Preferably, the paging broadcast
backbone message is transmitted by including the network prefix id (NetID) that the
mobile terminal had used.
[106] Figures 1 and 2 respectively show examples of the formats of the registration
response message (REG-RSP) and the ranging response message (RNG-RSP).
[107] As shown in Figure 1, the registration response message (REG_RSP) indicates
whether the terminal IP address should be re-configured (re-established) via bit #2. In
particular, the registration response message (REG-RSP) can instruct the terminal to
change its NetID, if the ID related to IP address of the terminal received by the new

base station from the previous base station and the ID being currently used (or that can
be used) are compared and found to be different. Preferably, even if bit #2 is not
activated, if the NetID change indicator is set, then the terminal re-configures
(re-establishes) its IP address.
[108] Also, referring to Figure 2, the ranging response message (RNG-RSP) indicates
whether the terminal IP address should be re-configuration via bit #0, and the NetID
change can be instructed to the terminal through a separate bit Similarly, even if bit #0
is not activated, if the NetID change indicator is set, then the terminal re-configuration
of its IP address.
[109] Figure 3 shows an example of how the matter of whether the IP address re-
configuration should be made is informed through the registration procedures when a
terminal in idle mode ends its idle mode because downlink (DL) traffic exists.
[110] Referring to Figure 3, the mobile terminal performs registration release request/
response (DREG_REQ/DREG_RSP) with the base station in order to enter idle mode.
At this time, the base station broadcasts the information about the terminal that entered
idle mode to all base stations within the same paging zone (e.g., through use of a
paging-announce message). Through this, the procedures that the terminal must
perform should be informed to the base stations at each paging cycle. To do so, the
paging broadcast backbone message may be used. The MAC address of the terminal
and the Network Prefix ID (NetID) corresponding to the IP address used by the mobile
terminal are both included in the paging broadcast backbone message and transmitted.
[111] Thereafter, for a mobile terminal in idle mode, when data traffic (uplink traffic)
that needs to be transmitted is generated or when data traffic (downlink traffic) that
needs to be received is generated, the mobile terminal ends its idle mode and performs
network entry.
[112] The base station (BS#3), with which the mobile station performs network entry
procedures, compares the network prefix ID (NetID) received from the base station
(BS#1) that had its registration released by the mobile terminal and the network prefix
ID (NetID) that it currently can use, and then the matter of whether IP address re-
configuration (re-establishment) would be needed or not is informed to the mobile
terminal during the ranging procedures (via a RNG-RSP message) or during the reg-
istration procedures (via a REG-RSP message).
[113] Accordingly, the mobile terminal determines whether to re-configure (re-establish)
its IP address based upon the RNG-RSP or REG-RSP message, and if not required, the
IP address re-configuration (re-establishment) procedures may be omitted, which
allows communications to be resumed more quickly.
[114] Also, when an ID related to an IP address is changed for handover with another
type of network, this can be informed by the base station to the mobile station by

including such in a ranging or registration response message.
[115] Thus, the methods that can be performed by the base station to inform the mobile
station about whether IP address re-configuration (re-establishment) would be needed
can be summarized as follows.
[116] 1. Method of mforming by setting a configuration bit in the registration response
message.
[117] 2. Method of informing by setting a configuration bit in the ranging response
message.
[118] For 1 or 2 above, if the network prefix ID (NetID) changes, this changed ID must
be informed to the terminal separately by using the ranging response message and the
registration response message.
[119] 3. Only in the case where the network prefix ID (NetID) changes, the mobile
terminal is informed through the ranging response message or the registration response
message.
[120] Figure 4 shows an example of informing whether or not the IP address re-
configuration (re-establishment) is needed through a ranging procedure when the
terminal ends its idle mode because downlink traffic exists.
[121] Figure 5 also shows an example of informing whether or not the IP address re-
configuration (re-establishment) is needed through a ranging procedure when the
terminal ends its idle mode because downlink traffic exists.
[122] Figure 6 shows an example of informing whether or not the IP address re-
configuration (re-establishment) is needed through a registration procedure when the
terminal ends its idle mode because uplink traffic exists.
[ 123] Hereafter, a method of configuring (establishing) an IP address of the terminal
during handover according to a second embodiment of the present invention will be
explained.
[124] In the terminal IP address configuration (establishment) method according to the
second embodiment of the present invention, a registration response message
(REG-RSP), a ranging response message (RNG-RSP), a handover confirmation
message (HO-confirm), etc. are defined.
[125] The registration response message (REG-RSP) is a message that is transmitted by
setting an IP re-configuration (re-establishment) required bit, when the ID related to
the terminal IP address received by the new base station (Target BS) from the previous
base station (Serving BS) when the mobile terminal performs registration procedures
after handover, and the ID that is currently being used (or can be used) are compared
and found to be different.
[126] The ranging response message (RNG-RSP) is a message that is transmitted by
setting an IP re-configuration (re-establishment) required bit, when the ID related to

the terminal IP address received by the new base station (Target BS) from the previous
base station (Serving BS) when the mobile terminal performs ranging with the new
base station after handover, and the ID that is currently being used (or can be used) are
compared and found to be different
[127] Also, the handover confirmation message is a message that allows delivery through
the backbone of an IP address related message of the mobile terminal that will move
from a previous base station to a new base station when the mobile terminal performs
handover. Accordingly, the new base station (Target BS) can determine whether the IP
address of the mobile terminal should be re-configured (re-established) through the
above-described messages.
[128] The formats of the registration response message (REG-RSP) and the ranging
response message (RNG-RSP) are shown in Figures 1 and 2, respectively, while the
format of the handover confirmation message is shown in Figure 7.
[129] In general, there are two types of handover; a handover started by the mobile
terminal and a handover determined by the network In either case, when handover is
performed, a handover confirmation message (HO-confirm) is delivered over the
backbone from the previous base station (Serving BS) to a new base station (Target
BS). When the handover confirmation message (HO-confirm) having the IP address of
the terminal that is moving and its related ID (NetID=xxx) is delivered, the new base
station uses this for comparison with the IP address related ID (NetID) that is uses and
can inform the comparison result to the terminal after handover is completed when the
ranging or registration procedure is performed,
[130] Thus, based upon the above results, the terminal can know whether the IP address
should be re-configured (re-established) or whether the previously used IP address can
be used. By employing the method of the present invention, the need for the terminal
to re-configure (re-establish) its IP address during handover can be reduced for
situations such as when the previous base station and the new base station have the
same IP subnet, when the foreign agent (FA) is the same, etc., to thus nunimize the
delays caused each time (he IP address is configured (established).
[131] Accordingly, in the terminal IP address configuration method according to the
second embodiment of the present invention, there are three methods by which the
base station can inform the mobile terminal about whether the IP address should be re-
configured (re-established), which are the same as those of the first embodiment.
[132] Figure 8 shows an example of the operation in informing the terminal about
whether the IP address should be re-configured (re-established) through (he ranging
procedures during handover.
[133] Figure 9 shows an example of the operation in informing the terminal about
whether the IP address should be re-configured (re-established) through the registration

procedures during handover.
[134] It can be said that the present invention relates to the minimization of IP con-
nectivity establishment procedures. IEEE 802.16 uses DHCP (Dynamic Host Con-
figuration Protocol) and Mobile IP in order to allocate IP addresses to MSSs (Mobile
Subscriber Stations), and after the MSS handover to the target BS (base station), re-
establishment of IP connectivity is required. However, in case the same subnet is used
in the target BS or the same Foreign Agent is connected in the new BS, the re-
establishment of IP connectivity procedure can be skipped and the MSS can use the
same IP address. Therefore, a mechanism to determine the subnet change or Foreign
Agent change for a moving MSS is required. When the MSS moves to a new BS, to
decide the MSS's subnet change or Foreign Agent change, the new BS can provide the
MSS with an instruction of subnet change provided through a backbone message.
Here, the network ID can represent a Subnet Prefix, an Access Router, or a Foreign
Agent One BS can have more than one NetID depending upon the network con-
figuration.
[135] The current IEEE 802.16 does not provide the MSS with an instruction for IP re-
establishment However, the present inventors propose a possible solution for the MSS
to make a decision as to whether it needs to re-establish IP connectivity. By giving the
MSS's IP related information to the target BS over a backbone, the target BS can
provide a moving MSS with an instruction of IP-establishment
[136] In the related art, after MSS handover, a new IP allocation procedure is required
regardless of subnet change. However, if the network subnet is not changed in the new
BS, the MSS can use the old IP address which was used in the previous BS. Namely, in
the DHCP case, if the network subnet is not changed in the new BS, the MSS can use
the old IP address which was used in the previous BS. In the Mobile IPv4 case, when a
MSS moves to a new BS, it takes some time for the MSS to re-establish IP con-
nectivity using Mobile IPv4 However, if the same Foreign Agent is connected to the
new BS, the MSS can skip the mobile IP procedure to reduce delay.
[137] To do so, the MSS needs information to decide whether the subnet or Foreign
Agent is different from the previous BS. The information for subnet change decision is
different depending upon the method for allocation the IP address. Two IP address
allocating methods can be defined. One is using DHCP, and the other is using Mobile
IPv4. Since DHCP messages and Mobile IPv4 messages are flowing on the secondary
management connection, the BSs can monitor and store the IP related information.
When an MSS is moving to a new BS, the old BS sends stored information (e.g., send
MSS's NetID through a backbone) to the new BS, which then compares the received
information with its own stored information (e.g., NetID) to make a decision of subnet
change. The new BS provides a decision of subnet change in REG-RSP to the MSS

after MSS's successful handover. For example, if one of the NetlDs in the new BS is
the same as the received NetID from the previous BS, the new BS instructs the MSS
with IP re-establishment is not required in a "Method for allocating IP address TLV of
REG-RSP. If me NetID either in the Serving BS or the Target BS or both do not exist,
the target BS should instruct to the MSS to re-establish IP connectivity.
[138] The procedures of how a subnet change can be decided for the DHCP case and for
the Mobile IP case will be described hereafter.
[139] Figures 10,11,12 and 13 show examples of the DHCP case, whereby, Figures 10
and 11 show when the DHCP server exists on the same network with the MSS, while
Figures 12 and 13 shown when the DCHP server exists on a different network with the
MSS. Figure 10 shows a DHCP message broadcast by the MSS, and Figure 11 shows a
DHCP message sent by the DHCP server in response to the message from the MSS.
Figure 12 shows a DHCP message forwarded from a MSS to a DHCP server by a relay
agent in the router, while Figure 13 shows a response from the DHCP server forwarded
by the relay agent in the router to the MSS.
[140] Referring to Figures 10 through 13, the relay agent IP address and server identifier
in the DHCP response from the server can be used to decide whether a subnet is
changed. Here, 'giaddr* refers to a relay agent IP address, and 'server identifier" is used
to identify a DHCP server in a DHCP message and as a destination address from
clients to servers.
[141] In the Mobile IPv4 case, the MSSs determine their movement by either using a
lifetime field within the ICMP Router Advertisement [IETF RFC 1256] portion of an
Agent Advertisement [IETF RFC 3220] or by using Network-Prefixes [IETF RFC
3220]. The Router Address with prefix-length extension can identify a network-prefix.
However, the prefix-length is an optional parameter, and when me prefix-length is not
present, this information should not be used to decide the network-prefixes. Figure 14
shows an example of an agent advertisement message.
[142] In the DHCP case, the BS listens to the DHCP offer message from the DHCP
server to the MSSs on the secondary management connection and stored the 'giaddr'
and 'server identifier'. In the Mobile IP case, the BS listens to the periodic Agent Ad-
vertisement from the Foreign Agent and stores me Router Address in an ICMP Router
Advertisement portion and a prefix-length extension in the Prefix-Length Extension of
an Agent Advertisement
[143] By providing information to a target BS when MSS moves to a new BS, the target
BS can determine whether the MSS's subnet has changed or not. The target BS tells the
MSS whether it has to re-establish IP connectivity or not in the registration response
(RSG-RSP) message.
[144] Accordingly, the present invention adds a mechanism for the BS to monitor the

DHCP related and Mobile IP related information. Also, Type-Length-Value (TLV)
parameters are added into the REG-RSP message, which is used to instruct the MSS
whether it should perform an IP address re-establishment procedure.
[145] For mobile networks, the target BS may include the IP Address Change In-
formation TLV in the REG-RSP message for MSS handover. The TLV specifies
whether MSS has to re-establish IP connectivity or not based on the received in-
formation from the old BS over a backbone. If the target BS cannot make a decision,
the value should be set to 1.
[146] For a managed MSS, there is the possibility that entry at the new BS necessitates
Layer 3 protocol exchanges in order to retain IP connectivity. Such an MSS should
take appropriate steps to detect and respond to the change of BS (e.g., by performing
Mobile IPv4 movement detection and re-registration, or Mobile IPv4 Binding Update).
In order for the MSS to facilitate an IP connectivity retainment, the new BS may
provide the MSS with an instruction of IP address change. The new BS's DP address
change instruction is made based on the information from the old BS over a backbone.
This information is stored by monitoring the MSS's IP connectivity establishment
using DHCP and listening to an Agent Advertisement from the Foreign Agent on the
secondary management connection.
[147] The following Table 1 shows an example of IP address establishment information.
[148]
[149] The following Table 2 shows an example of TLV values that may appear in the IP
address establishment information TLV.
[150]
[151] The following Table 3 shows an example of TLV values that may appear in the IP
address establishment information TLV.
[152] [Table 3]


[153] The following Table 4 shows an example of an IP Address Change Information.
This field indicates whether or not the MSS needs to re-establish an IP address after
handover. A bit value of '0' indicates that such is not required, while T indicates it is
required.
[154]
[ 155] The following Table 5 shows an example of the format of a Handover Comfirm
Message.
[156]

[157] Also, the present invention proposes to modify the "method for allocating IP
address TLV in the REG-RSP messages, which arc used to instruct the MSS as to
whether it should perform IP address re-establishment procedures, which is achieved
by adding 'NetID' and 'HO-Confirm and Paging-announce' backbone messages.
[158] Regarding the "Method for allocating IP address,' for establishing IP connectivity,
the BS may include the method for allocating IP address TLV in the REG-RSP for the
SS's or MSS's IP connectivity establishment. The TLV also specifies whether the MSS
has to re-establish IP connectivity or not when the MSS moves to the new BS. The IP
re-establishment required bit is set based on the comparison with the received NetID
from the old BS over a backbone. If the target BS cannot make a decision, the value
should be set as '1' (IP re-establishment required).
[159] The following Tables 6 and 7 show examples of the Method for allocating IP
address, Table 8 shows an example of a HO-Confirm Message format, and Table 9
shows an example of a Paging-announce message.
[160]-----
[161]
[162]

[163]
[164] Regarding the effects of the present invention, when a mobile terminal in idle mode
performs network entry procedures, the bases station (point of attachment) that
performed the registration release procedures of the mobile terminal delivers the
network prefix related information (e.g, NetID, Router Advertisement, Agent Ad-
vertisement) of the mobile terminal to another base station (point of attachment) within

the same paging zone, and the base station performing the network entry compares the
above network prefix related information (e.g, NetID) with the network prefix related
information (e.g, NetID) that it is using, to inform whether IP address re-configuration
(re-establishment) of me mobile station would be needed. Thus, by using the present
invention, when the network prefix related information (e.g, NetID) of a terminal is
changed, this changed network prefix related information (e.g, NetID) is informed to
the terminal to allow it to be used when performing handover with a different network
other that a IEEE 802.16 network.
[165] Also, in the present invention, when the mobile terminal performs IP address con-
figuration (establishment) procedures after handover, if the subnet used among two
base stations are the same or if the same foreign agent is used, the previous base station
delivers the network prefix related information (e.g, NetID, router advertisement,
Agent Advertisement) to the new base station, the new base station compares the
delivered network prefix related information (e.g, NetID) with the network prefix
related information (e.g, NetID) that it can or is currently using, and informs the
mobile station as to whether IP address re-configuration is needed or not
[166] Accordingly, the present invention has the effect of simplifying the IP address con-
figuration (establishment) procedures when the terminal changes from idle mode to
receiving mode or when handover is performed, and can thus minimize the time delay
caused by IP address re-configuration (re-establishment) of the related art
[167] As the present invention has been described above with respect to wireless access
technologies, it can be clearly understood that various types of wireless access
technologies currently under development (such as WiMax, WiBro, Wi-Fi, etc.) can
also benefit from the features and teachings of the present invention, which are.
applicable because of the similarities involved in wireless communications involving
user terminal mobility, handovers and idle mode operations.
[ 168] The foregoing description of the preferred embodiments is provided to enable any
person skilled in the art to make or use the present invention. Various modifications to
these embodiments will be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments. Thus, the present
invention is not intended to be limited to the embodiments shown herein but us to be
accorded the widest scope consistent with the principles and novel features disclosed
herein.

WE CLAIM:
1. A method of configuring an IP address of a terminal in a broadband wireless
access system, the method comprising:
transmitting by a first base station, a paging broadcast backbone message to
base stations with a same paging zone when a mobile station goes into idle mode;
when traffic to be transmitted or traffic to be received is generated, the mobile
station ends its idle mode and performs network entry with a second base station;
at the second base station, a network prefix ID received from the first base
station through the paging broadcast backbone message is compared with a network
prefix ID that can be used, to determine whether IP address re-configuration is
needed; and
informing the mobile station about the determined IP address re-configuration
when a registration procedure is performed,
wherein the matter of whether the IP address should be re-configured is
delivered through a registration response message,
wherein a result of the determination of whether the IP address should be re-
configured is informed by activation of an IP re-establishment required bit or a
network prefix ID change indicator of the registration response message both when
the IP address should be re-configured and when the IP address should be not re-
configured,
wherein the registration response message comprises IP Address Allocation
information and Network ID information, and the IP Address Allocation information
includes values indicating DHP-default, Mobile IPv4, and IP re-establishment
required,
wherein each value indicating DHP-default, Mobile IPv4, and IP re-
establishment required corresponds to bit #0, bit #1, and bit #2 of the IP Address
Allocation information, and bit #3 to bit #7 of the IP Address Allocation information
are set to zero.

2. The method as claimed in claim 1, wherein the paging broadcast backbone
message includes a medium access control address and a network prefix ID of the
terminal.
3. The method as claimed in claim 1, wherein the second base station informs
the mobile station of a changed network prefix ID when the network prefix ID used
by the terminal changes, through the registration response message.
4. The method as claimed in claim 1, wherein the matter of whether or not the
IP address should be re-configured is delivered the registration response message
only if the network prefix ID has changed.


ABSTRACT

A METHOD OF CONFIGURING AN IP ADDRESS OF A TERMINAL
IN A BROADBAND WTRELESS ACCESS SYSTEM
This invention is a method for configuring an IP address of fixed/mobile station in a
broadband wireless access system. A method of configuring an IP address of a terminal in a
broadband wireless access system is disclosed. The base station determines whether the
mobile station that changes from idle mode to receiving mode or performs handover needs to
re-configure its IP address, and informs this to the mobile station. So, IP address
configuration procedures are simplified between the base station and the mobile station.

Documents:

03309-kolnp-2006 abstract.pdf

03309-kolnp-2006 claims.pdf

03309-kolnp-2006 correspondence others.pdf

03309-kolnp-2006 description(complete).pdf

03309-kolnp-2006 drawings.pdf

03309-kolnp-2006 form-1.pdf

03309-kolnp-2006 form-3.pdf

03309-kolnp-2006 form-5.pdf

03309-kolnp-2006 gpa.pdf

03309-kolnp-2006 international publication.pdf

03309-kolnp-2006 international search authority report.pdf

03309-kolnp-2006 pct other document.pdf

03309-kolnp-2006 pct request form.pdf

03309-kolnp-2006 priority document.pdf

03309-kolnp-2006-assignment.pdf

03309-kolnp-2006-correspondence_1.1.pdf

03309-kolnp-2006-correspondence_1.2.pdf

03309-kolnp-2006-form-18.pdf

03309-kolnp-2006-form-3-1.1.pdf

3309-KOLNP-2006-(14-02-2012)-CORRESPONDENCE.pdf

3309-KOLNP-2006-ABSTRACT 1.1.pdf

3309-KOLNP-2006-AMANDED CLAIMS.pdf

3309-KOLNP-2006-AMANDED PAGES OF SPECIFICATION.pdf

3309-KOLNP-2006-ASSIGNMENT.pdf

3309-KOLNP-2006-CORRESPONDENCE 1.1.pdf

3309-KOLNP-2006-CORRESPONDENCE 1.3.pdf

3309-KOLNP-2006-CORRESPONDENCE-1.2.pdf

3309-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

3309-KOLNP-2006-DRAWINGS 1.1.pdf

3309-KOLNP-2006-EXAMINATION REPORT.pdf

3309-KOLNP-2006-FORM 1-1.1.pdf

3309-KOLNP-2006-FORM 18.pdf

3309-KOLNP-2006-FORM 2.pdf

3309-KOLNP-2006-FORM 3 1.2.pdf

3309-KOLNP-2006-FORM 3-1.1.pdf

3309-KOLNP-2006-FORM 5.pdf

3309-KOLNP-2006-GPA.pdf

3309-KOLNP-2006-GRANTED-ABSTRACT.pdf

3309-KOLNP-2006-GRANTED-CLAIMS.pdf

3309-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

3309-KOLNP-2006-GRANTED-DRAWINGS.pdf

3309-KOLNP-2006-GRANTED-FORM 1.pdf

3309-KOLNP-2006-GRANTED-FORM 2.pdf

3309-KOLNP-2006-GRANTED-SPECIFICATION.pdf

3309-KOLNP-2006-OTHERS 1.1.pdf

3309-KOLNP-2006-OTHERS.pdf

3309-KOLNP-2006-PA.pdf

3309-KOLNP-2006-PETITION UNDER RULE 137.pdf

3309-KOLNP-2006-REPLY TO EXAMINATION REPORT 1.1.pdf

3309-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-03309-kolnp-2006.jpg


Patent Number 253122
Indian Patent Application Number 3309/KOLNP/2006
PG Journal Number 26/2012
Publication Date 29-Jun-2012
Grant Date 27-Jun-2012
Date of Filing 10-Nov-2006
Name of Patentee LG ELECTRONICS INC.
Applicant Address 20,YOIDO-DONG YONGDUNGPO-GU SEOUL 150-010 REPUBLIC OF KOREA
Inventors:
# Inventor's Name Inventor's Address
1 KIM YONG-HO E-PYUNHANSESANG APARTMENT 108-503,813,HOGYE 3-DONG DONGAN-GU,ANYANG GYEONGGI-DO 431-834 REPUBLIC OF KOREA
PCT International Classification Number H04L12/28
PCT International Application Number PCT/KR2005/001353
PCT International Filing date 2005-05-09
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/569,238 2004-05-10 U.S.A.
2 60/570,836 2004-05-14 U.S.A.
3 60/577,186 2004-06-07 U.S.A.
4 60/571,537 2004-05-17 U.S.A.
5 41597/2004 2004-06-08 U.S.A.