Title of Invention

A METHOD FOR PERFORMING LOCATION UPDATE BY A MOBILE SUBSCRIBER STATION IN A COMMUNICATION SYSTEM

Abstract The invention relates to a method for performing location update by a mobile subscriber station in a communication system, the method comprising the steps of : mode-transiting (531) into an idle mode (530) if there is no data transmission between a serving base station (620, 720, 830, 930, 1030) and the mobile subscriber station (610, 710, 810, 910, 1010) during a predetermined first time interval in an awake mode (510); detecting that a paging zone changes into another paging zone to which a target base station (850, 950) belongs, wherein the another paging zone is different from the paging zone to which the serving base station (620, 720, 830, 930, 1030) of the mobile subscriber station (610, 710, 810, 910, 1010) belongs; and mode-transiting (541) into the awake mode (510) at timings determined based on an offset value and performing location update, the offset value being determined to differently set time points at which mobile subscriber stations of the target base station (850, 950) mode-transit from the idle mode (530) into the awake mode (510); wherein the location update is performed by transmitting a location update request to the target base station (850, 950) and receiving a location update response from the target base station (850, 950).
Full Text

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a broadband wireless access
communication system, and more particularly to a system and method for
controlling the operation mode of a Medium Access Control (MAC) layer.
2. Description of the Related Art
In 4th generation (4G) communication systems, which are the next
generation communication systems, improvements focus on providing various
qualities of service (QoSs) at high transmission speed. The third generation (3G)
communication system supports a transmission speed of about 384 kbps outdoors
with relatively bad channel conditions and a maximum transmission speed of
about 2 Mbps indoors with relatively good channel conditions
Wireless Local Area Network (LAN) and Metropolitan Area Network
(MAN) communication systems generally support transmission speeds of 20 to
50 Mbps. Since the wireless MAN communication system has a wide service
coverage and supports a high transmission speed, it is suitable for supporting a
high speed communication service. However, the wireless MAN system does not
provide for mobility of a user, i.e., a subscriber station (SS), or a handover for
high speed movement of the SS.
As a result, in 4G communication systems, a new type of communication
system ensuring mobility and QoS for wireless LAN and MAN systems
supporting relatively high transmission speeds is being developed to support high
speed service in the 4G communication system.
The IEEE (Institute of Electrical and Electronics Engineers) 802.16a

communication system employs an Orthogonal Frequency Division Multiplexing
(OFDM) scheme and an Orthogonal Frequency Division Multiple Access
(OFDMA) scheme to support a broadband transmission network for a physical
channel of the wireless MAN system.
The IEEE 802.16a communication system considers only a single cell
structure and stationary SSs, so the system does not condsider movement of the
SSs. In contrast, an IEEE 802.16e communication system has been defined as a
system designed for mobility of an SS in addition to the IEEE 802.16a
communication system, and thus, should reflect mobility of an SS in a multi-cell
environment. To provide for the mobility of an SS in a multi-cell environment as
described above, of the operation mode changes of the SS and its base station
(BS) are considered and accommodated. To that end, research about SS handover
in a multi-cell structure is actively pursued to support SS mobility. Herein, a
mobile SS is referred to as an Mobile Subscriber Station(MSS).
FIG. 1 is a block diagram schematically illustrating the structure of a
IEEE 802.16e communication system.
Referring to FIG. 1, the IEEE 802.16e communication system has a multi-
cell structure with a cell 100 and a cell 150. In addition, the IEEE 802.16e
communication system includes a BS 110 controlling the cell 100, a BS 140
controlling the cell 150, and a plurality of MSSs 111, 113, 130, 151, and 153. The
transmission/reception of signals between the BSs 110 and 140 and the MSSs 111,
113, 130, 151, and 153 is accomplished through an OFDM/OFDMA scheme. The
MSS 130 is located in a boundary zone (i.e., handover zone) between the cell 100
and the cell 150. When a handover for the MSS 130 is possible, the MSS 130 can
move without loss of service.
In the IEEE 802.16e communication system, a certain MSS receives pilot
signals transmitted from a plurality of BSs and measures Carrier to Interference
and Noise Ratios (CINRs) of the received pilot signals. The MSS selects the BS
with the highest CINR as a serving BS, which means the MSS belongs to that BS..
The MSS, having selected the serving BS, receives the downlink frame and
uplink frame transmtted from the serving BS and uses them in transmitting and

receiving data.
In the case where mobility of the MSS is taken into consideration as
described above, MSS power consumption plays an important part in system
performance. Therefore, a sleep mode operation and an awake mode operation
have been proposed for the BS and the MSS to minimize MSS power
consumption.
Hereinafter, operation modes of a Medium Access Control (MAC) layer
for the IEEE 802.16e communication system will be described with reference to
FIG. 2.
FIG. 2 is a mode diagram schematically illustrating the operation modes
supported by a MAC layer of the IEEE 802.16e communication system.
Referring to FIG. 2, the MAC layer of the IEEE 802.16e communication
system supports two kinds of operation modes (i.e., an awake mode 210 and a
sleep mode 220). First, the sleep mode 220 has been proposed in order to
minimize the power consumption of the MSS during idle time when packet data
is not transmitted. The MSS mode-trans its (211) from the awake mode 210 to the
sleep mode 220, thereby minimizing the power consumption of the MSS during
the idle time when packet data is not transmitted. In general, packet data is
transmitted in bursts when generated. It would be inefficient to perform the same
operations when data is transmitted and when data is not transmitted. For this
reason, the sleep mode operation as described above has been developed.
When packet data is generated while the MSS is in. the sleep mode, the
MSS mode-transits into the awake mode and transmits/receives the packet data.
However, because the packet data is highly reliable on a traffic mode, the sleep
mode operation must be organically performed in consideration of the traffic
characteristic and the transmission scheme characteristic of the packet data.
Hereinafter, schemes proposed up to now for the IEEE 802.16e
communication system to support operation in the sleep mode 220 will be
described.

First, to mode-transit into the sleep mode 220, an MSS receives mode
transition consent from a BS. The BS allows the MSS to shift into the sleep mode
220 simultaneously while buffering or dropping the packet data to be transmitted
to the MSS. In addition, the BS informs the MSS of packet data to be transmitted
during the listening interval of the MSS. The MSS awakes from the sleep mode
220 and checks whether there is any packet data to be transmitted from the BS to
the MSS. The listening interval will be described below in more detail. When
there is packet data to be transmitted from the BS to the MSS, the MSS mode-
transits to the awake mode 210 from the sleep mode 220 and receives the packet
data from the BS. When there is no packet data to be transmitted from the BS to
the MSS, the MSS stays in the sleep mode 220.
Hereinafter, parameters to support operation in the sleep mode and the
awake mode will be described.
1) Sleep Interval
The sleep interval is an interval requested by an MSS and assigned by a
BS according to. the MSS request. The sleep interval also represents the time it
takes to go from the sleep mode 220 to the awake mode 210. In other words, the
sleep interval is defined as an interval during which the MSS stays in the sleep
mode 220. The MSS may continue to stay in the sleep mode 220 even after the
sleep interval is over. In this case, the .MSS updates the sleep interval by
performing a sleep interval update algorithm by means of a preset initial sleep
window value and a final sleep window value. Herein, the initial sleep window
value corresponds to a minimum sleep window value and the final sleep window
value corresponds to a maximum sleep window value. Further, both the initial
sleep window value and the final sleep window value are assigned by the BS and
expressed by the number of frames. Since the minimum window value and the
maximum window value will be described in detail below, a further description is
omitted here.
2) Listening Interval
The listening interval is an interval requested by an MSS and assigned by

a BS according to the MSS request. Further, the listening interval represents the
time it takes for theMSS to awake from the sleep mode 220 and synchronize with
the downlink signal of the BS sufficient enough to decode downlink messages
such as a traffic indication (TRF_IND) message. Herein, the TRF_IND message
is a message representing existence of traffic (i.e., packet data) to be transmitted
to the MSS. Since the TRF_IND message will be described below, a further
detailed description is omitted here. The MSS determines whether to stay in the
awake mode or to mode-transit back into the sleep mode according to the values
of the TRF_IND message.
3) Sleep Interval Update Algorithm
When the MSS goes into the sleep mode 220, it determines the sleep
interval while regarding the preset minimum window value as a minimum sleep
mode interval. After the sleep interval passes, the MSS awakes from the sleep
mode 220 for the listening interval and checks whether there is packet data to be
transmitted from the BS. If there is no packet data to be transmitted, the MSS
renews the sleep interval to be twice as long as that of the previous sleep interval
and continues to stay in the sleep mode 220. For example, when the minimum
window value is "2", the MSS sets the sleep interval to be 2 frames and stays in
the sleep mode for 2 frames. After passage of the 2 frames, the MSS awakes from
the sleep mode and determines whether the TRF_IND message has been received.
When the TRF_IND message has not been received (that is, when no packet data
transmitted from the BS to the MSS exists), the MSS sets the sleep interval to be
4 frames (twice as many as 2 frames) and stays in the sleep mode 220 during the
4 frames. In this way, the sleep interval increases within a range from the initial
sleep window value to the final sleep window value. The algorithm for updating
the sleep interval as described above is the sleep interval update algorithm.
Hereinafter, a network re-entry process of an MSS will be described with
reference to FIG. 3.
FIG. 3 is a signal flowchart schematically illustrating a network re-entry
process of an MSS in a conventional IEEE 802.16e communication system.

First, in step 311, according to handover, the MSS receives preambles of
downlink frames transmitted from the handovered BS (i.e. a new serving BS) and
acquires system sync with the new serving BS. Thereafter, the MSS acquires
downlink sync from BS information contained in messages broadcasted by the BS,
which include a Downlink Channel Descriptor (DCD) message, an Uplink
Channel Descriptor (UCD) message, a downlink map (DL_MAP) message, an
uplink map (UL_MAP) message, a mobile neighbor advertisement
(MOB_NBR_ADV) message.
Thereafter, in step 313, the MSS transmits a ranging request (RNG_REQ)
message to the BS, receives a ranging response (RNG_RSP) message from the
BS in response to the RNG_REQ message, and acquires uplink sync with the BS
from the RNG_RSP message. Then, in step 315, the MSS adjusts frequency and
power.
Thereafter, in step 317, the MSS negotiates the basic capacity of the MSS
with the BS. In step 319, the MSS acquires an Authorization Key(AK) and a
Traffic Encryption Key (TEK) by performing authentication operation together
with the BS. In step 321, the MSS requests the BS to register the MSS and the BS
completes registration of the MSS. In step 323, the MSS performs an Internet
Protocol (IP) connection with the BS. In step 325, the MSS downloads
operational information through the IP in connection with the BS. In step 327, the
MSS performs service flow connection with the BS. Here, the service flow refers
to a flow in which MAC_SDUs (service data units) are transmitted and received
through a connection having a certain, predetermined threshold QoS. Thereafter,
in step 329, the MSS uses the service provided from the BS. Then, the process
ends.
Next, a handover process in an IEEE 802.16e communication system will
be described with reference to FIG. 4.
FIG. 4 is a signal flow diagram schematically illustrating a handover
process in a conventional IEEE 802.16e communication system.
Referring to FIG. 4, the MSS scans CINRs of the pilot signals from the

neighbor BSs in the process described (step 411). When the MSS 400 determines
that it should change the serving BS (step 413), the MSS 400 transmits an Mobile
Handover Request (MOB_HO_REQ) message to the current serving BS 410 (step
415). FIG. 4 is based on an assumption that the MSS 400 has two neighbor BSs
including a first BS 420 and a second BS 430. Here, the MOB_HO_REQ
message includes the result of scanning by the MSS 400.
When the serving BS 410 receives the MOB_HO_REQ message, the
serving BS 410 detects information on a list of neighbor BSs to which the MSS
400 can be handed over from information contained in the received
MOB_HO_REQ message (step 417). Here, for the convenience of description,
the list of neighbor BSs to which the MSS 400 can be handed over will be
referred to as 'handover-available neighbor BS list', and this example assumes
that the handover-available neighbor BS list includes the first BS 420 and the
second BS 430. The serving BS 410 transmits a handover notification
(HO_NOTIFICATION) message to the neighbor BSs contained in the handover-
available neighbor BS list, i.e., the first BS 420 and the second BS 430 (steps 419
and 421).
Upon receiving the HO_NOTIFICATION message from the serving BS
410, each of the first BS 420 and the second BS 430 transmits a handover
notification response (HO_NOTIFICATION_RESPONSE) message, which is a
response message to the HO_NOTIFICATION message, to the serving BS 410
(step 423 and 425). The HO_NOTIFICATION_RESPONSE message contains a
plurality of Information Elements (IEs) including an MSS ID of the MSS 40-,a
response (ACK/NACK) regarding whether or not the neighbor BSs can perform
the handover in response to the request of the MSS 400, and bandwidth and
service level information which each of the neighbor BSs can provide when the
MSS 400 is handed over for each BS.
When the serving BS 410 has receives the
HO_NOTIFICATION_RESPONSE message transmitted from the first neighbor
BS 420 and the second neighbor BS 430, the serving BS 410 selects a neighbor
BS that can optimally provide a bandwidth and a service level requested by the
MSS 400 when the MSS 400 is handed over, as a target BS to which the MSS 400 .'

will be actually handed over.
For instance, if the service level required by the MSS 400 is higher than a
service level which can be provided by the first neighbor BS 420 and is equal to a
service level which can be provided by the second neighbor BS 430, the serving
BS 410 will select the second neighbor BS 430 as the target BS. Then, the serving
BS 410 transmits a handover notification confirmation
(HO_NOTIFICATION_CONFIRM) message to the second neighbor BS 430 as a .
response to the HO_NOTIFICATION_RESPONSE message (step 427).
The serving BS 410 transmits an Mobile handover response
(MOB_HO_RSP) message to the MSS 400 as a response to the MOB_HO_REQ
message (step 429). The MOB_HO_RSP message contains information on the
target BS to which the MSS 400 will be handed over.
Next, upon receiving the MOB_HO_RSP message, the MSS 400 analyzes
the information contained in the MOB_HO_RSP message and selects the target
BS. After selecting the target BS, the MSS 400 transmits an Mobile handover
indication (MOB_HO_IND) message to the serving BS 410 as a response to the
MOB_HO_RSP message (step 431).
Upon receiving the MOB_HO_IND message, the serving BS 410
recognizes that the MSS 400 will be handed over to the target BS (i.e., the second
neighbor BS 430) contained in the MOB_HO_IND message, and then releases
the present setup link with the MSS 400 (step 433). Then, the MSS 400 performs
an initial ranging process with the second neighbor BS 430 (step 435) and
performs a network re-entry process with the second neighbor BS 430 when the
initial ranging succeeds(step 437).
The handover-related operations as described with reference to FIG. 4 are
operations performed by the MSS in awake mode. However, when the MSS
detects that it has reached a cell boundary zone while in sleep mode, the MSS
switches to the awake mode and performs the handover-related operations of FIG.
4. In Other words, when the MSS moves from a first cell to a second cell in
sleep mode, the MSS cannot restore the connection with the first cell BS and

performs a network re-entry process with the second cell BS. In performing the
network re-entry process in the current IEEE 802.16e communication system, the
MSS transmits an BS identifier (BS ID) of the previous BS to which the MSS
belonged, so that the new BS can recognize that the-MSS is being handed over.
Then, the new BS can acquire information of the MSS from the previous BS and
perform the handover together with the MSS.
The above description is given on both a method for reducing power
consumption of an MSS and a method for handover of an MSS. However, when
the method for reducing power consumption is applied to an MSS in the sleep
mode, the method becomes inefficient because the MSS, although it is in sleep
mode, must perform the handover as described above whenever it shifts between
cells, especiallywhen even an MSS having no traffic to transmit or receive at all
must perform the handover whenever it shifts between cells. The effect MSS
power consumption reduction is lessened and message overhead is generated
during the handover operation. Furthermore, all MSSs in the sleep and awake
modes perform periodic ranging. This, too, causes unnecessary power
consumption and generates message overhead.
Further, the current IEEE 802.16e communication system constantly
assigns various types of basic radio resources to MSSs with no traffic to transmit
or receive. Below are the basic radio resources that are always assigned regardless
of actual need.
(1) Basic Connection Identifier (CID)(Basic CID)
The basic CID is a connection identifier used in transmitting a message
that is relatively short and must be urgently transmitted (i.e., an urgent control
message).
(2) Primary Management CID
The primary management CID is a connection identifier used in
transmitting a message that is relatively long and has a relatively lower urgency.

(3) Secondary Management CID
The secondary management CID is a connection identifier used in transmitting a
message mat has a relatively lower urgency and relates to a standard protocol for
at least three layers.
Furthermore, in the IEEE 802.16e communication system, each MSS is assigned an
Internet Protocol version 4 (IPv4) address which is also a limited radio resource. As
described above, in the IEEE 802.16e communication system, radio resources as
described above, such as the connection identifiers and IPv4 addresses, may be
assigned to MSSs having no data to transmit or receive, thereby degrading die
efficiency in use of radio resources. Therefore, there is a necessity for a specific
operation scheme of a MAC layer to support operation between a BS and an MSS,
that can maximize efficiency in use of radio resources while minimizing power
consumption of die MSS moving at high speeds.
US 2003143999 A1 describes a telecommunication system, wherein paging areas
may be automatically reconfigured as required. Paging areas can be adaptively
reconfigured in accordance with changes in movement traffic of mobile hosts.
The system and method work under a constraint that only a limited number of
area IDs are permitted for each paging unit area. Also, the system and method
work over heterogeneous access networks. Thus, according to the presently
disclosed embodiments, paging areas reconfigure themselves according to
changes in movement traffic of mobile hosts.
US 6 463 055 B1 refers to integrated radio telecommunications network which
integrates an ANSI-41 circuit switched network and a General Packet Radio
Service, GPRS, packet data network to support a mobile station which operates in
both the ANSI-41 network and the GPRS network. An interworking function
interfaces a mobile switching center, MSC, in the ANSI-41 network with a serving
GPRS switching node, SGSN, in the GPRS network by mapping circuit switched
signaling utilized by the MSC into GPRS packet switched signaling utilized by the

SGSN, and mapping GPRS packet switched signaling into circuit switched
signaling. An interworking GPRS base station controller interfaces the SGSN with
a GPRS/ANSI-136 base station which supports both ANSI-136 operations and
GPRS operations. The interworking GPRS base station controller adapts the traffic
signaling format utilized by the SGSN into an air interface traffic signaling format
utilized by the GPRS/ANSI-136 base station. An authentication center interface
passes the authentication state of the mobile station between an ANSI-41 home
location register/authentication center, HLR/AC, in the ANSI-41 network, and a
GPRS home location register/authentication center, HLR/AUC, in the GPRS
network.
US 5 509 015 A describes a system for reducing receiver power consumption in
communication system having a transmitter and one or more receivers schedules
periodic messages in slots. Each receiver is assigned a slot during which it
monitors the transmissions. The transmitter transmits messages to the receiver
only during the assigned slots. The receiver is in an active state during its
assigned slot. It may remain in the active state after its assigned slot if the
message requires the receiver to perform additional actions. During the inactive
state, which is the time period between successive occurrences of its assigned
slot, the receiver may perform any action not requiring coordination with the
transmitter. It may conserve power during this time by removing power from one
or more components such as those used for monitoring the transmissions. At a
time during the inactive state shortly before the assigned slot, the receiver
applies power to these components and performs initializations. Such
initializations may include reacquiring a pilot channel signal to which the receiver
may synchronize itself if its timing signals have drifted out of synchronization with
those of the transmitter during the preceding inactive state.

SUMMERY OF THE INVENTION
Accordingly, the present invention has been made to solve the above-mentioned
problems occurring in the prior art, and the object of the present invention is to
provide a system and a method for controlling MAC layer operation modes of a
broadband wireless access communication system.
It is aspect of the present invention to provide a system and a method for
minimizing power consumption of MSSs by controlling MAC layer operation modes
of a broadband wireless access communication system.
It is another aspect of the present invention to provide a system and a method
for paging an MSS in an idle mode of a MAC layer in a broadband wireless access
communication system.
It is another aspect of the present invention to provide a system and a method for
location update according to movement of the MSS in an idle mode of a MAC layer in
a broadband wireless access communication system..

To accomplish this object, there is provided a method for controlling
operation modes of a medium access control layer by a mobile subscriber station
in a broadband wireless access communication system including the mobile
subscriber station and a serving base station providing service to the mobile
subscriber station. The method comprises the steps of mode-transiting into an idle
mode when the mobile subscriber station is in an inactive state to conserve power
and operational resources; detecting movement of the mobile subscriber station in
the idle mode into another paging zone to which a target base station belongs,
which is different from a paging zone to which the serving base station belongs;
and mode-transiting into the awake mode and performing location update
together with the target base station when the movement of the mobile subscriber
station is detected.
In accordance with another aspect of the present invention, there is
provided a method for controlling operation modes of a medium access control
layer by a mobile subscriber station in a broadband wireless access
communication system including the mobile subscriber station and a serving base
station providing service to the mobile subscriber station. The method comprises
the steps of mode-transiting into an idle mode when there is no data transmission
between the serving base station and the mobile subscriber station - during a
predetermined first time interval in an awake mode; and mode-transiting into the
awake mode and performing location update of the mobile subscriber station
itself at each predetermined interval in the idle mode.
In accordance with another aspect of the present invention, there is
provided a method for determining paging time points for a plurality of mobile
subscriber stations by a paging controller when mobile some subscriber stations
mode-transits from an awake mode having transmission of traffic into an idle
mode having no transmission of traffic from among the plurality of mobile
subscriber stations in a broadband wireless access communication system
including a base station, the plurality of mobile subscriber stations in a cell
controlled by the base station, and the paging controller connected to the base
station, the method including determining a paging interval; determining an offset
value in order to differently set time points at which mobile subscriber stations
awake; and determining based on the paging interval and the offset value the time
points at which mobile subscriber stations awake.

In accordance with another aspect of the present invention, there is
provided a system for controlling operation modes of a medium access control
layer by a mobile subscriber station in a broadband wireless access
communication system including the mobile subscriber station and a serving base
station providing service to the mobile subscriber station. The system comprises
the mobile subscriber station which mode-transits into an idle mode when there is
no data transmission between the serving base station and the mobile subscriber
station during a predetermined first time interval in an awake mode, mode-transits
into the awake mode and transmits a location update request to a target base
station when detecting movement of the mobile subscriber station in the idle
mode into another paging zone to which the target base station belongs, which is
different from a paging zone to which the serving base station belongs, and
performs location update in accordance with a location update response from the
target base station, which responds to the location update request; the target base
station which, together with a paging controller for performing the paging zones,
performs the location update of the mobile subscriber station and transmits the
location update response to the mobile subscriber station when the location
update request from the mobile subscriber station is detected; and the paging
controller for updating the location of the mobile subscriber station
correspondingly to the location update operation of the target base station and the
mobile subscriber station.
In accordance with another aspect of the present invention, there is
provided a system for controlling operation modes of a medium access control
layer in a broadband wireless access communication system. The system
comprises a mobile subscriber station which mode-transits into an idle mode
when there is no data transmission between a base station and the mobile
subscriber station during a predetermined first time interval in an awake mode,
mode-transits into the awake mode and transmits a location update request to the
base station at each predetermined interval in the idle mode, and performs
location update in accordance with a location update response from the base
station, which responds to the location update request; the base station which,
together with a paging controller for performing the paging zones, performs the
location update of the mobile subscriber station and transmits the location update
response to the mobile subscriber station when the location update request from
the mobile subscriber station is detected; and the paging controller for updating

the location of the mobile subscriber station correspondingly to the location update
operation of the base station and the mobile subscriber station.
In accordance with another aspect of the present invention, there is provided a
method for determining paging time points for a plurality of mobile 5 subscriber
stations by a paging controller when mobile some subscriber stations mode-transits
from an awake mode having transmission of traffic into an idle mode having no
transmission of traffic from among the plurality of mobile subscriber stations in a
broadband wireless access communication system including a base station, the
plurality of mobile subscriber stations in a cell controlled by the base station, and
die paging controller connected to the base station. The mediod comprises the
steps of determining a paging cycle; determining an offset value in order to
differently set time points at which mobile subscriber stations awake; and
determining based on the paging cycle and the offset value the time points at
which mobile subscriber stations awake.
In accordance with another aspect of the present invention, there is provided a
broadband wireless access communication system comprising a base station; a
plurality of mobile subscriber stations in a cell controlled by the base station; and a
paging controller for determining paging time points for a plurality of mobile
subscriber stations when mobile some subscriber stations mode-transits from an
awake mode having transmission of traffic into an idle mode having no
transmission of traffic from among the plurality of mobile subscriber stations,
determining an offset value in order to differently set time points at which mobile
subscriber stations awake, and determining based on a paging cycle and the offset
value the time points at which mobile subscriber stations awake.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above object and other aspects, features and advantages of the present
invention will be more apparent from the following detailed description taken in
conjunction with the accompanying drawings, in which:
FIG 4 is a block diagram schematically showing the structure of a typical IEEE
802.16e communication system;
FIG 2 is a mode diagram schematically illustrating the operation modes
supported by a MAC layer of a typical IEEE 802.16e communication system;
FIG. 3 is a signal flowchart schematically showing a process in which an_

MSS enters a network of a typical IEEE 802.16e communication system;
FIG. 4 is a signal flow diagram schematically showing a handover process
in a typical IEEE 802.16e communication system;
FIG. 5 is a diagram schematically illustrating the operation modes
supported by a MAC layer of a broadband wireless access communication system
according to an embodiment of the present invention;
FIG. 6 is a diagram schematically illustrating mode transition of an MSS
from the awake mode to the idle mode according to an embodiment of the present
invention;
FIG. 7 is a signal flow diagram of a process for paging an MSS in the idle
mode according to an embodiment of the present invention;
FIG. 8 is a signal flow diagram of a process for handover of an MSS in
the idle mode which does not require a location update according to an
embodiment of the present invention;
FIG. 9 is a signal flow diagram of a process for handover of an MSS in
the idle mode which requires a location update according to an embodiment of the
present invention; and
FIG. 10 is a signal flow diagram of a process for periodic location update
of an MSS in the idle mode according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter, preferred embodiments of the present invention will be
described with reference to the accompanying drawings. In the following
description, a detailed description of known functions and configurations
incorporated herein will be omitted when it may make the subject matter of the
present invention unclear.
FIG. 5 is a diagram schematically illustrating the operation modes
supported by a Medium Access Control(MAC) layer of a broadband wireless
access(BWA) communication system according to an embodiment of the present
invention.
In the following description of embodiments of the present invention, an

Institute of Electrical and Electronics Engineers(IEEE) 802.16e communication
system performing communication by an Orthogonal Frequency Division
Multiplexing(OFDM) scheme and an Orthogonal Frequency Division Multiple
Access(OFDMA) scheme is employed as an example of the BWA communication
system of the present invention. Referring to FIG. 5, a MAC layer of the IEEE
802.16e communication system supports three kinds of operation modes (i.e:, an
awake mode 510, a sleep mode 520, and an idle mode 530). The awake mode 510
and the sleep mode 520 are the same as the awake mode 210 and the sleep mode
220, so a detailed description of them is omitted here.
The idle mode 530 is a new mode included in an embodiment of the
present invention. An Mobile Subscriber Station (MSS) in the idle mode 530 does
not transmit or receive traffic. It measures downlink preambles, specifically
intensities of pilot signals, transmitted from neighbor base stations(BSs), and
receives only system information and paging messages broadcasted from the
neighbor BSs, thereby maximizing the effect of reduction in power consumption.
That is, the MSS being in the idle mode 530 exits in an inactive state and thus, the
MSS changes the current mode into the idle mode 530 in order to preserve power
source and operation resources under the inactive state.
In this case, when a Carrier to Interference and Noise Ratio (CINR ) of a
pilot signal from a particular neighbor BS (i.e., a target BS) is higher than the
current BS, the MSS, while in idle mode 530, determines that the MSS has moved
from the serving BS to the target BS.
The MSS analyzes System Information (SI) broadcast from the target BS
and compares a Paging Zone Identifier (PZID), with a PZID of the previous BS or
the serving BS. When the PZID of the previous BS is different from the PZID of
the target BS, the MSS performs location registration. When the PZID of the
previous BS is identical to the PZID of the target BS, the MSS remains in sleep
for a predetermined time interval once more. After the predetermined time
interval passes, the MSS performs location registration, thereby updating the
location information, even when there is no change in location.
Hereinafter, the paging zone will be described.

The paging zone is a zone in which a plurality of BSs are grouped to
constitute one paging unit. That is, a plurality of BSs are grouped to generate one
paging zone as a paging unit, and location information of MSSs is managed for
each of the paging zones. Each of the paging zones is identified using a Paging
Zone Identifier (PZID). Each BS broadcasts a PZID of the BS together with other
system information each frame. If the MSS leaves the current paging zone and
enters a new paging zone, the MSS receives a new PZID from the new paging
zone BS. The difference between the new PZID and the previously received PZID
enables the MSS to recognize an entry into the new paging zone from the
previous paging zone. Here, PZID value may be contained in a downlink
map(DL—MAP) message, etc.
When an MSS changes paging zones, it requests change of location to the
corresponding BS of the new paging zone, so it can respond to a network page in
the new location. In preferred embodiments of the present invention, a plurality of
cells are grouped to form the paging zone. However, it is not beyond the scope
of the present invention to include a single cell in the paging zone. Also, the
paging zone, including a single cell, may apply to the inter-cell handover
operation. When the concept of the paging zone is the same as that of the single
cell as described above, the concept of the paging zone can be applied to
handover between cells in the same manner. Further, when the concept of the
paging zone is the same as that of the single cell, the MSS can recognize a
movement from a previous cell to a new cell by means of a BS ID contained in
the DL_MAP message.
The MSS in the idle mode 530 is preferably not assigned the basic
resources that should be basically and constantly assigned in the IEEE 802.16e
communication system, such as a basic Connection Identifier (CID), a primary
management CID, and a secondary management CID, thereby maximizing the
efficiency in use of the radio resources.
First, a process of transition of the MSS from the awake mode 510 to the
idle mode 530 will be described below.
The mode transition of the MSS from the awake mode 510 to the idle

mode 530 is usually forced by the BS or according to a request of the MSS. The
MSS in the awake mode 510 mode-tranits into the idle mode 530 by transmitting
a mobile idle mode transition request (MOB_IDL_REQ) message and receiving a
mobile idle mode transition response (MOB_IDL_RSP) message when there is .
expected to be no data transmission/reception during a predetermined time
interval set in advance by the BS or the MSS. The mode transition of the MSS
from the awake mode 510 to the idle mode 530 will be described in detail later.
Meanwhile, the mode transition of the MSS from the idle mode 530 to
the awake mode 510 as shown by arrow 541 may be performed when the MSS.
receives a mobile paging request (MOB_PAG_REQ) from the BS, when the MSS
has data to transmit, when the MSS moves from the current paging zone, when a
location update is performed at expiration of the predetermined time interval, or
when the new BS to which the MSS moves does not support the idle mode 530.
The mode transition of the MSS from the idle mode 530 to the awake mode 510
will be described later in detail, so its detailed description is omitted here.
The above description with reference to FIG. 5 is given on the operation
modes supported by a MAC layer of a broadband wireless access communication
system according to an embodiment of the present invention. Hereinafter, an
operation of the MSS from the awake mode to the idle mode will be described
with reference to FIG. 6.
First, in a state where the MSS 610 is in the awake mode, when there is
no data transmission or reception between the MSS and the BS 620, the MSS 610
transmits an MOB_IDL_REQ message to the BS 620 (step 611). The
MOB_IDL_REQ message may contain a preferred idle interval
(PREF_IDLE_INTERVAL), that is, an idle intervale (or paging cycle) during
which the MSS 610 stays in the idle mode. Nomenclature such as a paging cycle
or preferred paging cycle arises from the fact that the MSS escapes from the idle
mode and monitors whether there is a paging from the base station in this cycle.
In the following description, the term 'paging cycle' will be mainly used instead
of the 'idle interval'.
. The MOB_IDL_REQ message has a structure as illustrated in Table 1.


In Table 1, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_IDL_REQ message is undetermined yet and has thus
been marked as '??'. Further, 'PREF_IDLE_INTERVAL_INDEX' represents an
idle interval (i.e. paging cycle) preferred by the MSS.
The BS 620, upon receiving the MOB_ JDL_REQ message from the MSS
610, transmits an idle mode request (IDLEMODEREQUEST) message to a
paging controller (PC) 630 in step 613. Upon receiving the
IDLE_MODE_REQUEST message from the BS 620, the paging controller 630
determines a paging cycle for the MSS 610 by referring to the preferred paging
cycle of the MSS 610 and the MAC address of the MSS 610. Herein, the paging
cycle determined by the paging controller 630 will be called 'selected paging
cycle'. Further, the paging controller 630 determines a paging time point for
paging the MSS 610 in accordance with the selected paging cycle (step 615). The
paging controller 630 transmits an idle mode response
(IDLE_MODE_RESPONSE) message containing the selected paging cycle and

the paging time point to the BS 620 (step 617).
Upon receiving the IDL_MODE_RESPONSE, message, the BS 620
transmits the MOB_IDL_RSP message containing information about the selected
paging cycle (step 619). The MOBIDLRSP message has a structure as
illustrated in Table 2 below.



In Table 2, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_IDL_RSP message is undetermined yet and has thus
been marked as '??'. Further, 'Idle approved' represents whether the mode
transition into the idle mode has been approved. When the 'Idle approved' has a
value of '0', it indicates that the mode transition into the idle mode is not
approved. When the 'Idle approved' has a value of '1', it indicates that the mode

transition-into the idle mode is approved. 'After_REQ_action' represents whether
the MSS should retransmit the MOB_IDL_REQ message, with a '0' indicating
that it should retransmit and a ' 1', indicating that is should not.
'REQ_duration' represents the time the MSS waits before re-transmitting
the MOB_IDL_REQ message. 'SEL_IDLE_INTERVAL_INDEX' represents the
selected paging cycle determined by the paging controller 630.
'TB_REGI_REQUIRED' indicates whether a timer-based registration is
requested with a '0' indicating the registration has not been requested and a '1'
indicating that is has. 'TB_REGI_INDES' indicates the count value of the timer
when the timer-based registration is requested.
The MSS 610 mode-transits from the awake mode into the idle mode by
referring to the selected paging cycle contained in the MOB_IDL_RSP message
from the BS 620 and monitors whether there is a paging message for the MSS
610 itself in each paging cycle (step 621).
Hereinafter, an operation of the paging controller 630 for determining the
paging cycle and the paging time point will be described.
First, the paging controller 630 calculates the first paging time point F0 by
using a Hash function employing the MAC address of the MSS 610 as an input
parameter. The paging controller 630 obtains a set of the paging time points by
using the selected paging cycle D. Here, the selected paging cycle D can be
expressed by Equation (1) below:

In Equation (1), D represents a paging cycle, Y represents a maximum
value of frame number, i represents an exponent of the paging cycle, δ is equal to
2j and j typically has a value of 0. Of course, j may have another value instead of
0.
When the set of paging time points is put as {Fi} (i = 0, 1, ...., Y/D), the
relation between the (n+l)th paging time point Fn+1 and the nth paging time point

Fn can be expressed by Equation (2) below:

As shown in Equation (2), the (n+1) paging time point Fn+1 is set
differently from the nth paging time point Fn as much as an offset generated in
consideration of the nth paging time point Fn and the paging cycle. Herein, an
interval between F„ and Fn+1 is a paging cycle.
The information about the paging cycle and the paging time point
determined by the paging controller 630 is shared by all BSs in the paging zone to
which the MS S 610 belongs.
The above description with reference to FIG. 6 is given of the operation
of the MSS from the awake mode to the idle mode according to an embodiment
of the present invention. Now, an operation of paging an MSS in the idle mode
will be described with reference to FIG. 7.
FIG. 7 is a signal flow diagram of a process for paging an MSS in the idle
mode according to an embodiment of the present invention.
First, when the paging controller 780 detects a page or traffic for the MSS
710, the paging controller 780 transmits a PAGING_REQUEST message to all
BSs in the paging zone to which the MSS 710 currently belongs (steps 711, 713,
and 715). In FIG. 7, the .paging zone to which the MSS 710 currently belongs
includes three BSs, a first BS 720, a second BS 740, and a third BS 760. The -
PAGING_REQUEST message is sent to all BSs in the same paging zone because
each BS lacks sufficient information to determine which paging zone it is in. Each
of the first BS 720, the second BS 740, and the third BS 760 receives the
PAGING_REQUEST message from the paging controller 780 and transmits a
MOB_PAG_REQ message targeting the MSS 710 to the MSS 710 (steps 717, 719,
and 721)..
The MOB_PAG_REQ message has a structure as shown in Table 3 below.


In Table 3, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_IDL_RSP message is undetermined yet and has thus
been marked as '??'. 'Number of paged terminal' represents the number of MSSs

which the network has currently paged from among the MSSs in the idle mode.
'MAC_ADDRESS' represents.a MAC address (i.e. a specific identifier) of each
paged MSS. Here, the paging message may be obtained by either modifying the
existing message currently used in the IEEE 802.16e communication system or
generating a new message. Further, 'PAGJPURPOSE' represents the object to
transmit the MOB_IDL_REQ message, 'LENGTH' represents the length of
'PAYLOAD', and 'PAYLOAD' represents actual contents corresponding' to
values marked in 'PAGPURPOSE'.
The values marked in 'PAG_PURPOSE' are as shown in Table 4 below.

In Table 4, '00000000' is a value reserved for future use, '00000001:
indicates that the MSS receiving the MOB_PAG_REQ performs the network re-

entry and initialization, '00000010' indicates that the MSS receiving the
MOBPAGREQ need not transmit a MOB_PAG_RSP message in response to
the MOBPAGREQ, '00000011' indicates that the MSS receiving the
MOBPAGREQ should transmit a MOB_PAG_RSP message in response to the
MOB_PAG_REQ, '00000100' indicates that it is necessary to change the paging
cycle, '00000100' indicates that location update should be performed, and
'00000110' through 'Oxff' are values reserved for future use.
The contents of Tables 5 through 9 are recorded in the 'PAYLOAD' in
accordance with the values marked in 'PAG_PURPOSE'.

The contents in Table 5 indicate contents recorded in 'PAYLOAD' when
'00000001' is marked on 'PAG_PURPOSE'. When '00000001' is marked on
'PAG_PURPOSE', it indicates that the message is an MOB_PAG_REQ message
containing downlink data targeting the MSS.


The contents in Table 6 indicate contents recorded in 'PAYLOAD'
when '00000010' is marked on TAG_PURPOSE\ When '00000010' is marked
on 'PAGPURPOSE', it indicates that the message is an MOB_PAG__REQ
message which does not require transmission of an MOBPAGRSP message in
response to the MOB_PAG_REQ message.

The contents in Table 7 indicate contents recorded in 'PAYLOAD5 when
'00000011' is marked on 'PA"G_PURPOSE\ When '00000011' is marked on
'PAG_PURPOSE\ it indicates that the message is an MOB_PAG_REQ message
which requires transmission of an MOB_PAG_RSP message in response to the
MOB_PAG_REQ message.


The contents in Table 8 indicate contents recorded in 'PAYLOAD' when
'00000100' is marked on 'PAG_PURPOSE\ When '00000100' is marked on
'PAG_PURPOSE', it indicates that the message is an MOBPAGREQ message
which requires to change the paging cycle.

The contents in Table 9 indicate contents recorded in 'PAYLOAD' when
'00000101' is marked on 'PAG_PURPOSE'. When '00000101' is marked on
'PAG_PURPOSE', it indicates that the message is an MOB_PAG_REQ message
which requires location update.

The example of FIG. 7 assumes that 'PAG_PURPOSE' of the
MOB_PAG_REQ message is marked as '00000011', which indicates
transmission of an MOB_PAG_RSP message in response to the MOB_PAG_REQ
message. Table 10 shows the structure of the MOB_PAG_REQ message.



In Table 10, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_IDL_RSP message is undetermined yet and has thus
been marked as '??'. 'Cause' indicates the reason for the transmission of the
MOB_PAG_RSP message. When '01' is marked on 'Cause', it indicates that the
MOBPAGREQ message has been approved. A '10' indicates that the
MOB_PAG_REQ message has been denied. Further, 'PL_TYPE' represents the
type of 'PAYLOAD' of the MOB_PAG_RSP message; '01' indicates just an
acknowledgement, '10' indicates a response message. 'LENGTH' represents the
length of'PAYLOAD'.
Upon receiving the MOB_PAG_REQ message, the MSS 710 recognizes
from the value '00000011' marked on 'PAG_PURPOSE' that the MSS 710
transmits a MOB_PAG_RSP message to a corresponding BS in response to the
MOB_PAG_REQ message. Herein, if the MSS 710 has moved within the paging
zone to another BS different from the BS to which the MSS 710 belonged before
the mode transition into the idle mode, the MSS 710 performs the initial ranging
again(step 723). The MSS 710.performs the initial ranging because the MSS 710
needs assigned uplink bandwidth, etc. in order to transmit the MOB_PAGJR.SP
message. FIG. 7 assumes that the MSS 710 determined from the initial ranging
that the first BS 720 is the serving BS to which the MSS 710 currently belongs.
Thereafter, the MSS 710 transmits the MOB_PAG_RSP message to the
first BS 720 (step 725). Upon receiving the MOB_PAG_RSP message, the first
BS 720 transmits to the paging controller 780 a 'PAGING_RESPONSE' message
responding to the TAGING_REQUEST' message (step 727). Further, the first BS
720 transmits an MOB_IDL_RSP message to the MSS 710, thereby controlling

the MSS 710 to transit into the idle mode (step 729).
The above description with reference to FIG. 7 is given of an operation of
paging an MSS in the idle mode according to an embodiment of the present
invention. Now, handover of an MSS in the idle mode which does not require
location update according to an embodiment of the present invention will be
described with reference to FIG. 8.
FIG. 8 is a signal flow diagram of a process for handover of an MSS in
the idle mode which does not require location update according to an embodiment
of the present invention.
FIG. 8 is based on the case where handover of an MSS 810 in the idle
mode moves (i.e. performs the handover) within the same paging zone (i.e. in a
paging zone using the same PZID). Referring to FIG. 8, a serving BS 830
transmits an MOB_IDL_RSP message to the MSS 810 (step 811).The serving BS
830 may transmit the MOB_IDL_RSP message either in response to the
MOBIDLREQ message, or based on an unsolicited scheme. Here, the
transmission of the MOB_IDL_RSP message by the serving BS 830 is based on
an unsolicited scheme and may be intended to adjust the load of the serving BS
830. Upon receiving the MOBIDLRSP message from the serving BS 830, the
MSS 810 transits from the awake mode to the idle mode.
While the MSS 810 is in the idle mode, it moves from a service zone
controlled oy the serving BS 830 to another service zone controlled by a target BS
850 (step 813). For this example, it is assumed that the serving BS 830 and the
target BS 850 are located within the same paging zone.
When the MSS 810 moves, communication between the serving BS 830
and the MSS 810 is disconnected and the MSS 810 cannot receive the
MOB_PAG_REQ message eYeil though the MSS 810 performs network
monitoring after awakening at the paging time point. Therefore, when the MSS
810 moves to a new BS (i.e. target BS 850), the MSS receives information of the
target BS 850 from an uplink channel descriptor (UCD) message, a downlink
channel descriptor (DCD) message, and DL_MAP and UIJV1AP messages

broadcast by the target BS 850 (step 815). As described above, the PZID of the
target BS 850 may be contained in the DL_MAP message.
By receiving BS information broadcast by the target BS 850, the MSS
810 detects the PZID of the target BS 850, and thus recognizes that the serving
BS 830 and the target BS 850 are located within the same paging zone (step 817).
Then, the MSS 810 checks the frame number, thereby recognizing its own paging
time point. Thereafter, the MSS 810 checks whether it has reached the paging
time point (step 819). If it has not yet reached the paging time point, the MSS 810
scans neighbor BSs (step 821). Here, scanning of the neighbor BSs includes
scanning of Carrier to Interference and Noise Ratio (CINRs) of pilot signals
transmitted from the neighbor BSs to detect movement of the MSS in the idle
mode.
When it has reached the paging time point, the MSS awakes from the idle
mode and receives the MOB_PAG_REQ message from the target BS 850 (step
823). Here, it is assumed that the MOBPAGREQ message transmitted from the
target BS 850 does not contain the MAC address of the MSS 810, so that the
MSS 810 remains in the idle mode.
The above description with reference to FIG. 8 is given of handover of an
MSS in the idle mode that does not require location update according to an
embodiment of the present invention. Now, handover of an MSS in the idle mode
that does use location updates according to an embodiment of the present
invention will be described with reference to FIG 9.
FIG. 9 is a signal flow diagram of a process for handover of an MSS in
the idle mode that uses location updates according to an embodiment of the
present invention.
FIG. 9 is based on a case where handover of an MSS 910 in the idle mode
moves (i.e. performs the handover) into a different paging zone (i.e. into a paging
zone using a different PZID). Referring to FIG. 9, a serving BS 930 transmits a
MOB_IDL_RSP message to the MSS 910 (step 911). The serving BS 930 may be
transmitting the MOB_IDL_RSP message either in response to an

MOB__IDL_REQ message transmitted from the MSS 910, or based on an
unsolicited scheme. Here, the MOB_IDL_RSP message is transmitted based on
the unsolicited scheme and may be intended to adjust the load of the serving BS
930. Upon receiving the MOB_IDL_RSP message from the serving BS 930, the
MSS 910 transits from the awake mode to the idle mode. .
In this example, while the MSS 910 is idle, the MSS 910 moves from a
service zone controlled by the serving BS 930 to another service zone controlled
by a target BS 950(step 913). Here, it is assumed that the serving BS 930 and the
target BS 950 are located within different paging zones. When the MSS 910
moves, the communication between the serving BS 930 and the MSS 910 is
disconnected so the MSS 910 cannot receive the MOB_PAG_REQ message, even
though the MSS 910 performs network monitoring after awakening at the paging
time point. Therefore, when the MSS 910 moves to a new BS (i.e. target BS 950),
the MSS receives information of the target BS 950 from an UCD message, a
DCD message, and DLJV1AP and UL_MAP messages broadcasted by the target
BS 950 (step 915). As described above, the PZID of the target BS 950 may be
contained in the DL_MAP message.
By receiving the BS information broadcast by the target BS 950, the MSS
910 detects the PZID of the target BS 950 and thus recognizes that the serving BS
930 and the target BS 950 are located within different paging zones (step 917).
Then, the MSS 910 performs the initial ranging (step 919) to acquire the basic
CID and the primary management CID. Then, the MSS 910 transmits a mobile
location update request (M0B_LU_REQ) message to the target BS 950 (step
921). The M0BJLUJREQ message has a structure as shown in Table 11.



In Table 11, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_LU_REQ message is undetermined yet and has thus
been marked as '??'. Further, 'PREF_IDLE_INTERVAL_rNDEX' represents an
idle interval (i.e. paging cycle) preferred by the MSS, and 'PREFPZONE ID'
represents a PZID of the serving BS 930 to which the MSS 910 belonged before
the handover.
Upon receiving the MOB_LU_REQ message from the MSS 910, the
target BS 950 transmits a location update request
(LOCATIONJJPDATE_REQUEST) message to the paging controller 970 (step
923). Here, the LOCATION_UPDATE_REQUEST message transmitted from the
target BS 950 contains a MAC address of the MSS 910 requiring the location
update and the PZID of the serving BS 930 to which the MSS 910 belonged
before the handover. Upon receiving the LOCATIONJJPDATEJREQUEST
message, the paging controller 970 updates the location of the MSS 910 based on
the PZID and the MAC address contained in the
LOCATION_UPDATE_REQUEST message and then transmits, a location update
response (L0CATI0N_UPDATE_RESP0NSE) message to the target BS 950 in
response to the LOCATIONJJPDATEJEQUEST message (step 925). Upon
receiving the, L0CATI0N_UPDATE_RESPONSE message from the paging
controller 970, the target BS 950 transmits a mobile location update response
(MOB_LU_RSP) message to the MSS 910 (step 927). The MOB_LU_RSP
message has a structure as shown in Table 12 below.




In Table 12, 'Management Message Type' contains information about the
type of message being currently transmitted. Currently, the 'Management
Message Type' of the MOB_LU_RSP message is undetermined yet and has thus
been marked as '??'. Further, 'LU approved' indicates whether the location
update has failed; a value of '0' indicates failure and a value of '1' indicates
success. 'After_REQ_action' indicates whether the MSS should retransmit the
MOB_LU_REQ message when the location update has failed with a '0'
indicating retransmission after waiting a predetermined time, and a ' 1' indicating
retransmission is not needed. 'REQjIuration' indicates a duration during which
the MSS waits to retransmit the MOB_LU_REQ message.
'SELJDLEJNTERVALJNDEX' indicates a paging cycle newly determined
when the location update has been achieved. 'TB_REGI_REQUIRED' indicates
Whether the new BS (the target BS) requests a timer-based registration.
'TB_REGI_INDES' indicates a count value of the timer when the target BS

requests timer-based registration.
Upon receiving the MOB_LU_RSP message from the target BS 950, the
MSS 910 switches, or mode-transits into the idle mode correspondingly to the
selected paging cycle, etc. contained in the MOB_LU_RSP message.
The above description with reference to FIG. 9 is given of handover of an
MSS in the idle mode that uses location updates according to an embodiment of
the present invention. Now, periodic location update of an MSS in idle mode
according to an embodiment of the present invention will be described with
reference to FIG. 10.
FIG. 10 is a signal flow diagram of a process for periodic location update
of an MSS in the idle mode according to an embodiment of the present invention.
First, an MSS 1010 in the awake mode transmits an MOB_IDL_REQ
message to the BS 1030 (step. 1011). Upon receiving the MOB_IDL_REQ
message from the MSS 1010, the BS 1030 transmits an
IDLE_MODE_REQUEST message to the paging controller 1050 (step 1013).
Upon receiving the IDLE_MODE_REQUEST message from the BS 1030, the
paging controller 1050 transmits to the BS 1030 an IDLE_MODE_RESPONSE
message responding to the IDLE_MODE_REQUEST message (step 1015). Upon
receiving the IDLE_MODE_RESPONSE message, the BS 1030 transmits to the
MSS 1010, an MOBJDLJRSP ■ message in response to the MOB_IDL_REQ
message (step 1017). Here, the M0B_IDL_RSP message contains a selected
paging cycle and a paging time point determined for the MSS 1010, and a request
for registration based on the timer.. That is, it is assumed that the
'TB_REGI_REQUIRED' of the MOB_IDL_REQ message is marked as 1.
Upon receiving the MOBJDLJISP message from the BS 1030, the MSS
1010 switches, or transits, from the awake mode into the idle mode. The MSS
1010 starts count of a predetermined time interval, :TB_REGI_INTERVAL\ to
request the timer-based registration inidle mode and performs the initial ranging
(step 1021) for the location Update when it has reached the
CTB_REGI_INTERVAL' (step 1019). By performing the initial ranging, the MSS

1010 acquires the basic CID and the primary management CID. Then, the MSS
1010 transmits an MOB_LU_REQ message to the BS 1030 (step 1023). Steps
1023 through 1029 in FIG. 10 are similar to steps 921 through 927 in FIG. 9
between the MSS 910, the target BS 950, and the paging controller 970, so a
detailed description of them will not be repeated here.
Next, the process of determining the TBJREGIJNTERVAL' by the
MSS 910 is described.
First, the MSS 910 obtains the 'TB_REGIJNTERVAL' by using the
'TB_REGI_INDEX' and 'SEL_IDLE_rNTERVAL_INDEX' in the
MOB_IDL_RSP message. Here, the 'TBJREGIJNTERVAL' can be expressed by
Equation (3) below.
TB_REGI_INTERVAL = 2fT (3)
In Equation (3), / represents 'SELJDLEJNTERVALJNDEX' and T
represents 'TB_REGI_INDEX'. That is, 'TB_REGI_INTERVAL' can be
expressed as an integer number multiple of the paging cycle.
Location updates of the MSS are periodically performed tO increase
convenience in the location update and reliability in the updated location of the
MSS. Of course, as described above with reference to FIG. 10, the location update
may be performed even when a zone in which the MSS is located is not actually
changed. However, when the paging controller performs the paging while
enlarging the paging zone from the cell which has been most-recently updated by
the MSS, the increase of the load due to the periodic location update can be
compensated for by the reduction of the load by the reduction of the paging zone.
As described above, the present invention provides new MAC layer
operation modes proper for a broadband wireless access communication system,

thereby minimizing power consumption while supporting mobility of an MSS and high
speed data transmission. Further, the present invention prevents unnecessary
possession of radio resources by discarding the network entry process in the same
paging zone. Therefore, the present invention can maximize efficiency in use of
resources and eliminates message overhead due to network entry.
While the invention has been shown and described with reference to certain
preferred embodiments thereof, it will be understood by those skilled in the art that
various changes in form and details may be made therein without departing from
the scope of the invention as defined by the appended embodiments.

WE CLAIM :
1. A method for performing location update by a mobile subscriber station in
a communication system, the method comprising the steps of :
mode-transiting (531) into an idle mode (530) if there is no data
transmission between a serving base station (620, 720, 830, 930, 1030)
and the mobile subscriber station (610, 710, 810, 910, 1010) during a
predetermined first time interval in an awake mode (510);
detecting that a paging zone changes into another paging zone to which a
target base station (850, 950) belongs, wherein the another paging zone
is different from the paging zone to which the serving base station (620,
720, 830, 930, 1030) of the mobile subscriber station (610, 710, 810, 910,
1010) belongs; and
mode-transiting (541) into the awake mode (510) at timings determined
based on an offset value and performing location update, the offset value
being determined to differently set time points at which mobile subscriber
stations of the target base station (850, 950) mode-transit from the idle
mode (530) into the awake mode (510),
wherein the location update is performed by transmitting a location
update request to the target base station (850, 950) and receiving a
location update response from the target base station (850, 950).

2. The method as claimed in claim 1, wherein operation modes of a medium
access control layer in the communication system comprises the awake
mode (510), the idle mode (530), and a sleep mode (520);
wherein the awake mode (510) is a mode in which a packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and the serving base station (620, 720, 830,
930, 1030) is performed;
wherein the sleep mode (520) is a mode in which the packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and the serving base station (620, 720, 830,
930, 1030) is not performed, and
wherein the idle mode is a mode (530) in which the mobile subscriber
station (610, 710, 810, 910, 1010) receives system information form at
least one base station, and detects the paging zone change based on
information indicating a paging zone included in the system information.
3. The method as claimed in claim 1, comprising the step of mode-transiting
(511) into a sleep mode (520) if there is no data transmission between
the serving base station (620, 720, 830, 930, 1030) and the mobile
subscriber station (610, 710, 810, 910, 1010) in the awake mode (510)
. during a predetermined second time interval, the predetermined second
time interval being shorter than the predetermined first time interval.

4. The method as claimed in claim 1, comprising the step of mode-transiting
(541) from the idle mode (530) into the awake mode (510) if the mobile
subscriber station (610, 710, 810, 910, 1010) detects a paging targeting
the mobile subscriber station (610, 710, 810, 910, 1010) itself.
5. The method as claimed in claim 4, wherein the step of detecting the
paging comprises :
receiving paging information broadcasted from the serving base station
(620, 720, 830, 930, 1030) in accordance with a paging cycle; and
recognizing existence of the paging if the paging information contains the
mobile subscriber station identifier of the mobile subscriber station
(610,710, 810, 910, 1010).
6. The method as claimed in claim 1, wherein the step of performing the
location update comprises :
performing the location update cyclically at a predetermined idle interval.
7. A mobile subscriber station in a communication system, comprising :
a transmitter;
a receiver; and
a processor to mode transits into an idle mode (530) if there is no data
transmission between a serving base station (620, 720, 830, 930, 1030)
and the mobile subscriber station (610, 710, 810, 910, 1010) during a
predetermined first time interval in an awake mode (510), detect that a
paging zone changes into another paging zone to which a target base
station (850, 950) belongs, wherein the another paging zone is different
from a paging zone to which the serving base station (620, 720, 830, 930,
1030) of the mobile subscriber station ((610, 710, 810, 910, 1010).

belongs, mode-transits into the awake mode (510) at timings determined
based on an offset value, and perform location update the offset value
being determined to differently set time points at which mobile subscriber
stations of the target base station (850, 950) mode-transit from the idle
mode (530) into the awake mode (510);
wherein the processor performs location update by processing transmitter
to transmit a location update request to the target base station (850, 950)
and processing the receiver to receive a location update response from
the target base station (850, 950).
8. The mobile subscriber station as claimed in claim 7, wherein operation
modes of a medium access control layer in the communication system
comprises the awake mode (510), the idle mode (530), and a sleep mode
(520);
wherein the awake mode (510) is a mode in which a packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and the serving base station (620, 720, 830,
930, 1030) is performed;
wherein the sleep mode (520) is a mode in which the packet data
transmission/reception operation between the mobile subscriber station
(610,720, 820, 920, 1010) and the serving base station (620, 720, 830,
1030) is not performed, and

wherein the idle mode (530) is a mode in which the mobile subscriber
station (610, 710, 810, 910, 1010) receives system information from at
least one base station, and detects the paging zone change based on
information indicating a paging zone included in the system information.
9. The mobile subscriber station as claimed in claim 7, wherein the processor
mode-transits (511) into a sleep mode (520) if there is no data
transmission between the serving base station (620, 720, 830, 930, 1030)
and the mobile subscriber station (610, 710, 810, 910, 1010) during a
predetermined second time interval, the predetermined second time
interval being shorter than the predetermined first time interval.
10. The mobile subscriber station as claimed in claim 7, wherein the processor
mode-transits (541) from the idle mode (530) into the awake mode (510)
if the processor detects a paging targeting the mobile subscriber station
(610, 710, 810, 910, 1010).
11. The mobile subscriber station as claimed in claim 7, wherein the receiver
receives paging information broadcast from the serving base stat ion (620,
720, 830, 930, 1030) in accordance with a paging cycle, and the
processor recognizes existence of the paging if the paging information
contains the mobile subscriber station identifier of the mobile subscriber
station (610, 710, 810, 910, 1010).
12. The mobile subscriber station as claimed in claim 7, wherein the processor
performs the location update cyclically at a predetermined idle interval.

13. A method for performing location update by a target base station in a
communication system, the method comprising the steps of:
receiving a location update request from a mobile subscriber station (610,
710, 810, 910, 1010); and
transmitting a location update response to the mobile subscriber station
(610, 710, 810, 910, 1010);
wherein the location update request is transmitted by the mobile
subscriber station (610, 710, 810, 910, 1010) after the mobile subscriber
station (610, 710, 810, 910, 1010) mode-transits (541) from an idle mode
(530) into an awake mode (510) at timings determined based on an offset
value, the offset value being determined to differently set time points at
which mobile subscriber stations of the target base station (850, 950)
mode-transit from the idle mode (530) into the awake mode (510).
14. The method as claimed in claim 13, wherein operation modes of a
medium access control layer in the communication system includes the
awake mode (510), the idle mode (530), and a sleep mode (520);
wherein the awake mode (510) is a mode in which a packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and a serving base station (620, 720, 830,
930, 1030) of the mobile subscriber station (610, 710, 810, 910, 1010) is
performed;
wherein the sleep mode (520) is a mode in which the packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and the serving base station (620, 720, 830,
930, 1030) is not performed; and

wherein the idle mode is a mode (530) in which the mobile subscriber
station (610, 710, 810, 910, 1010) receives system information from at
least one base station, and detects a paging zone change based on
information indicating a paging zone included in the system information.
15. The method as claimed in claim 13, wherein the location update request is
transmitted, by the mobile subscriber station (610, 710, 810, 910, 1010),
cyclically at a predetermined idle interval.
16. A target base station in a communication system, comprising:
a receiver for receiving a location update request from a mobile subscriber
station (610, 710, 810, 910, 1010); and
a transmitter for transmitting a location update response to the mobile
subscriber station (610, 710, 810, 910, 1010);
wherein the location update request is transmitted by the mobile
subscriber station (610, 710, 810, 910, 1010) after the mobile subscriber
station (610, 710, 810, 910, 1010) mode-transits (541) from an idle mode
(530) into an awake mode (510) at timings determined based on an offset
value, the offset value being determined to differently set time points at
which mobile subscriber stations of the target base station (850, 950)
mode-transit from the idle mode (530) into the awake mode (510).
17. The target base station as claimed in claim 16, wherein operation modes
of a medium access control layer in the communication system includes
the awake mode (510), the idle mode (530), and a sleep mode (520);

wherein the awake mode (510) is a mode in which a packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and a serving base station (620, 720, 830,
930, 1030) of the mobile subscriber station (610, 710, 810, 910, 1010) is
performed;
wherein the sleep mode (520) is a mode in which the packet data
transmission/reception operation between the mobile subscriber station
(610, 710, 810, 910, 1010) and the serving base station (620, 720, 830,
930, 1030) is not performed, and
wherein the idle mode is a mode (530) in which the mobile subscriber
station (610, 710, 810, 910, 1010) receives system information from at
least one base station, and detects a paging zone change based on
information indicating a paging zone included in the system information.
18. The target base station as claimed in claim 16, wherein the location
update request is transmitted, by the mobile subscriber station (610, 710,
810, 910, 1010), a cyclically at a predetermined idle interval.



ABSTRACT


" A METHOD FOR PERFORMING LOCATION UPDATE
BY A MOBILE SUBSCRIBER STATION IN A
COMMUNICATION SYSTEM"
------------------------------------------------------
The invention relates to a method for performing location update by a
mobile subscriber station in a communication system, the method
comprising the steps of : mode-transiting (531) into an idle mode (530) if
there is no data transmission between a serving base station (620, 720,
830, 930, 1030) and the mobile subscriber station (610, 710, 810, 910,
1010) during a predetermined first time interval in an awake mode (510);
detecting that a paging zone changes into another paging zone to which a
target base station (850, 950) belongs, wherein the another paging zone
is different from the paging zone to which the serving base station (620,
720, 830, 930, 1030) of the mobile subscriber station (610, 710, 810, 910,
1010) belongs; and mode-transiting (541) into the awake mode (510) at
timings determined based on an offset value and performing location
update, the offset value being determined to differently set time points at
which mobile subscriber stations of the target base station (850, 950)
mode-transit from the idle mode (530) into the awake mode (510);
wherein the location update is performed by transmitting a location
update request to the target base station (850, 950) and receiving a
location update response from the target base station (850, 950).

Documents:

02481-kolnp-2006 abstract.pdf

02481-kolnp-2006 assignment.pdf

02481-kolnp-2006 claims.pdf

02481-kolnp-2006 correspondence others.pdf

02481-kolnp-2006 description(complete).pdf

02481-kolnp-2006 drawings.pdf

02481-kolnp-2006 form-1.pdf

02481-kolnp-2006 form-2.pdf

02481-kolnp-2006 form-3.pdf

02481-kolnp-2006 form-5.pdf

02481-kolnp-2006 international publication.pdf

02481-kolnp-2006 international search authority report.pdf

02481-kolnp-2006 pct form.pdf

02481-kolnp-2006 priority document.pdf

2481-kolnp-2006-(08-09-2011)-ABSTRACT.pdf

2481-kolnp-2006-(08-09-2011)-AMANDED CLAIMS.pdf

2481-kolnp-2006-(08-09-2011)-DESCRIPTION (COMPLETE).pdf

2481-kolnp-2006-(08-09-2011)-DRAWINGS.pdf

2481-kolnp-2006-(08-09-2011)-EXAMINATION REPORT REPLY RECIEVED.pdf

2481-kolnp-2006-(08-09-2011)-FORM 1.pdf

2481-kolnp-2006-(08-09-2011)-FORM 3.pdf

2481-kolnp-2006-(08-09-2011)-FORM 5.pdf

2481-kolnp-2006-(08-09-2011)-OTHERS.pdf

2481-KOLNP-2006-(08-09-2011)-PETITION UNDER RULE 137.pdf

2481-KOLNP-2006-(11-04-2012)-CLAIMS.pdf

2481-KOLNP-2006-(11-04-2012)-CORRESPONDENCE.pdf

2481-KOLNP-2006-(11-04-2012)-OTHERS.pdf

2481-KOLNP-2006-(23-02-2012)-CORRESPONDENCE.pdf

2481-KOLNP-2006-CANCELLED PAGES.pdf

2481-KOLNP-2006-CORRESPONDENCE 1.1.pdf

2481-KOLNP-2006-CORRESPONDENCE-1.1.pdf

2481-KOLNP-2006-CORRESPONDENCE.pdf

2481-KOLNP-2006-ENGLISH TRANSLATION.pdf

2481-KOLNP-2006-EXAMINATION REPORT.pdf

2481-KOLNP-2006-FORM 18.pdf

2481-KOLNP-2006-FORM 18_.pdf

2481-KOLNP-2006-FORM 3.1.pdf

2481-KOLNP-2006-GPA.pdf

2481-KOLNP-2006-GRANTED-ABSTRACT.pdf

2481-KOLNP-2006-GRANTED-CLAIMS.pdf

2481-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

2481-KOLNP-2006-GRANTED-DRAWINGS.pdf

2481-KOLNP-2006-GRANTED-FORM 1.pdf

2481-KOLNP-2006-GRANTED-FORM 2.pdf

2481-KOLNP-2006-GRANTED-FORM 3.pdf

2481-KOLNP-2006-GRANTED-FORM 5.pdf

2481-KOLNP-2006-GRANTED-SPECIFICATION-COMPLETE.pdf

2481-KOLNP-2006-OTHERS.pdf

2481-KOLNP-2006-PETITION UNDER RULE 137.1.pdf

2481-KOLNP-2006-PETITION UNDER RULE 137.pdf

2481-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-02481-kolnp-2006.jpg


Patent Number 255861
Indian Patent Application Number 2481/KOLNP/2006
PG Journal Number 13/2013
Publication Date 29-Mar-2013
Grant Date 26-Mar-2013
Date of Filing 31-Aug-2006
Name of Patentee SAMSUNG ELECTRONICS CO.LTD.
Applicant Address 416,MAETAN-DONG,YEONGTONG-GU,SUWON-SI,GYEONGGI-DO.
Inventors:
# Inventor's Name Inventor's Address
1 HYON-GOO KANG #202,1255-7,MAETAN-DONG,YEONGTONG-GU,SUWON-SI,GYEONGGI-DO.
2 KWANG-SEOP EOM #406-103,SANGNOKMAEUL IMGWANG BOSEONG APT,JEONGJA-DONG,BUNDANG-GU,SEONGNAM-SI,GYEONGGI-DO.
3 SEUNG-EUN HONG #210-801,WONCHEON JUGONG 2-DANJI APT,WONCHEON-DONG,YEONGTONG-GU,SUWON-SI,GYEONGGI-DO.
4 YEONG-MOON SON #102,JEONGWOOVILLA,897-1 ANYANG 3-DONG,MANAN-GU,ANYANG-SI,GYEONGGI-DO.
5 SO-HYUN KIM #531-1402,SHINAN APT,YEONGTONG-DONG,YEONGTONG-GU,SUWON-SI,GYEONGGI-DO.
6 SEUNG-IL YOON #111-102,CHEONGSOLMAEUL GYERYONG APT,GEUMGOK-DONG,BUNDANG-GU,SEONGNAM-SI,GYEONGGI-DO.
7 TAE-WON KIM #230-1703,SUNGWON SANGTTEVILL 3-CHA SANGHYEON-DONG,YONGIN-SI,GYEONGGI-DO.
8 JUNG-SHIN PARK #892-20,DAERIM 1-DONG,YEONGDEUNGPO-GU,SEOUL,
9 HONG-SUNG CHANG #435-1802,SAMSUNGRAEMIAN CHEONGMYEONGMAEUL YEONGTONG-DONG,YEONGTONG-GU,SUWON-SI,GYEONGGI-DO.
10 YONG CHANG #403-801,PUREUNMAEUL SHINSUNG APT,SUNAE-DONG,BUNDANG-GU,SEONGNAM-SI,GYEONGGI-DO.
11 GEUN-HWI LIM #101-301,HYUNDAI VILLA,41,BUNDANG-DONG,BUNDANG-GU,SEONGNAM-SI,GYEONGGI-DO.
12 JAE-JEONG SHIM 3rd FLOOR 183-21,DONGGYO-DONG,MAPO-GU,SEOUL.
13 BONG-GEE SONG #103-201,YANGJIMAEUL GEUMHO 1-DANJI APT,SUNAE-DONG,BUNDANG-GU,SEONGNAM-SI,GYEONGGI-DO.
PCT International Classification Number H04B7/005;H04L12/28
PCT International Application Number PCT/KR2005/000606
PCT International Filing date 2005-03-04
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 14753/2004 2004-03-04 Republic of Korea