NOTIFICATION OF CHANNEL DESCRIPTOR TRANSMISSION FORA
MOBILE STATION IN IDLE OR SLEEPMODE IN A WIRELESS ACCESS
SYSTEM
TECHNICAL FIELD
The present invention relates generally to a wireless access system and, more
particularly, to idle or sleep mode in a wireless access system.
BACKGROUND ART
A mobile station (MS) operating in sleep or idle mode of a wireless access
system conventionally acts to confirm that sleep or idle mode may be maintained by
continually receiving broadcast messages from a base station (BS), such as a traffic
indicating message and a paging advertising message, and decoding the received
messages to confirm MS status.
Since the traffic indicating message and the paging advertising message include
information related to all nearby mobile stations in sleep or idle mode, the messages
may be very long. Thus, the mobile station may consume much power to decode the
messages.
For most mobile stations, the time required for transmission/reception of data
may be shorter than a standby time for receiving data. Therefore, a mobile station in
sleep mode typically receives a traffic indicating message to continue the sleep mode
(e.g., Negative Indication). Furthermore, a mobile station in idle mode typically
receives a paging advertising message to continue idle mode (e.g., No Action Required).
The sleep mode and idle mode control the mobile station via broadcasting, e.g., the
traffic indicating message and the paging advertising message, respectively.
However, when the mobile station in sleep or idle mode unnecessarily decodes
a message, power is unnecessarily consumed by the mobile station.
DISCLOSURE OFTHE INVENTION
Accordingly, the present invention is directed to notification of channel
descriptor transmission for a mobile station in idle or sleep mode that substantially
obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide for transmission of a channel
descriptor in a wireless access system, such that information regarding decode necessity
of a message transmitted in a broadcast format is transmitted to a mobile station. The
channel descriptor information may include a downlink channel descriptor (DCD) or an
uplink channel descriptor (UCD), and/or decode information. The mobile station then
may perform a decode on a necessary message only. Such operation may provide for
reduced power consumption by the mobile station and thereby more efficient
communications .
Additional advantages, objects, and features of the invention will be set forth in
part in the description which follows and in part will become apparent to those having
ordinary skill in the art upon examination of the following or may be learned from
practice of the invention. The objectives and other advantages of the invention may be
realized and attained by the structure particularly pointed out in the written description
and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the
purpose of the invention, as embodied and broadly described herein, in one embodiment,
a method for controlling an idle mode in a mobile station comprises transmitting an idle
mode request to a serving base station to enter the idle mode, and receiving a decode
information transmission frame value and a decode information change status from at
least one base station. The method also comprises, if the decode information change
status indicates a change in the decode information, maintaining the idle mode, and
receiving the decode information from the at least one base station when the
transmission frame value is reached.
The decode information may comprise at least one of downlink channel
descriptor (DCD) information and uplink channel descriptor (UCD) information. The
decode information may comprise forward error correction (FEC) code type
information. The transmission frame value may comprise a frame number. The
transmission frame value may comprise a frame offset. The at least one base station
may be in a same paging group. The method may further comprise maintaining the
idle mode if the decode information change status indicates no change in the decode
information.
In another embodiment, a method in a network for controlling an idle mode in a
mobile station comprises receiving an idle mode request from a mobile station to enter
the idle mode, and transmitting a decode information transmission frame value and a
decode information change status to the mobile station. If the decode information
change status indicates a change in the decode information, the mobile station maintains
the idle mode. The method also comprises transmitting the decode information to the
mobile station when the transmission frame value is reached.
The network may comprise at least one base station and a paging controller, the
paging controller configured to control paging within base stations of a paging group.
The decode information transmission frame value and the decode information change
status may be broadcast to the mobile station at each paging interval.
The foregoing and other objects, features, aspects and advantages of the present
invention will become more apparent from the following detailed description of the
present invention when taken in conjunction with the accompanying drawings. It is to
be understood that both the foregoing general description and the following detailed
description of the present invention are exemplary and explanatory and are intended to
provide further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a part of this
application, illustrate embodiments of the invention and together with the description
serve to explain the principles of the invention.
FIG. 1 is a block diagram illustrating protocol layers for use in a wireless access
system, according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a subchannel of an OFDMA physical layer,
according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating a data region of an OFDMA physical layer,
according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating mapping of an FEC block to an OFDMA
subchannel and an OFDM symbol, according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating a frame structure of an OFDMA physical layer
in a wireless access system, according to an embodiment of the present invention.
FIG. 6A is a diagram illustrating a MAC PDU format, according to an
embodiment of the present invention.
FIG. 6B is a diagram illustrating a MAC management message format,
according to an embodiment of the present invention.
FIG. 6C is a diagram illustrating a plurality of concatenated MAC PDUs for
transmission as an uplink burst, according to an embodiment of the present invention.
FIG. 7 is a signal flow diagram illustrating idle mode action in a mobile station,
according to an embodiment of the present invention.
FIG. 8 is a diagram illustrating a mobile station in idle mode receiving a
DCD/UCD message, according to an embodiment of the present invention.
FIG. 9 is a diagram illustrating a mobile station in idle mode receiving a
DCD/UCD message, according to another embodiment of the present invention.
FIG. 10 is a generalized block diagram of a mobile station, according to an
embodiment of the present invention.
DETAILED DESCRIPTION OFTHE PREFERRED EMBODIMENTS
Reference will now be made in detail to the preferred embodiments of the
present invention, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the drawings to
refer to the same or like parts.
The present invention may be embodied in a wireless access system operating
according to the IEEE 802.16e standard. However, the present invention may also be
embodied in wireless access systems operating according to other standards.
The present invention may provide for transmission of a channel descriptor in a
wireless access system, such that information regarding decode necessity of a message
transmitted in a broadcast format is transmitted to a mobile station. The channel
descriptor information may include a downlink channel descriptor (DCD) or an uplink
channel descriptor (UCD), and/or decode information. The mobile station then may
perform a decode on a necessary message only. Such operation may provide for reduced
power consumption by the mobile station and thereby more efficient communications.
Actions of a mobile station in sleep mode include repetition of a listening
interval and a sleep interval. The length of the listening interval may be fixed via a sleep
request/sleep response message. During the listening interval, the mobile station may
confirm whether downlink traffic intended for the mobile station and/or whether to
maintain the sleep mode, via a traffic indicating (e.g., MOB_TRF_IND) message
transmitted from a base station. The length of the sleep interval may be determined by a
sleep window. During the sleep interval, the mobile station receives minimal downlink
signals from the base station in order to minimize power consumption.
Actions in sleep mode are performed by sending/receiving management
messages, such as a sleep request (e.g., MOB-SLP-REQ) message, a sleep response
(e.g., MOB-SLP-RSP) message, and/or a traffic indicating message delivered in a
broadcast format between the mobile station and the base station.
Table 1, below, shows an exemplary management message that includes a sleep
interval and a listening interval, delivered for a sleep mode request from a mobile
station to a serving base station.
[Table 1]
Table 2, below, shows an exemplary sleep response (e.g., MOB-SLP-RSP)
message to deliver sleep mode associated information including a presence or non-
presence of sleep mode approval, a sleep interval, a listening interval, and/or a sleep ID
to a mobile station from a serving base station.
[Table 2]
Table 3, below, shows an exemplary broadcast traffic indicating (e.g., TRF-
IND) message delivered at a uniform interval. A mobile station in sleep mode receives a
traffic indicating message during a listening interval to decide whether to maintain the
sleep mode or to receive downlink data by terminating the sleep mode.
[Table 3]
Idle mode supports mobility and increases power efficiency of the mobile
station by receiving a periodic paging advertising (e.g., MOB-PAG-ADV) message at
the mobile station within a paging zone. The paging zone includes a plurality of base
station areas. To configure a paging zone, an inter-base-station message (e.g., Paging-
Group-Action) is transmitted between base stations by wire in a format such as that
shown in the below Table 4.
[Table 4]
The inter-base-station message (e.g., Paging-Group-Action) is delivered
between base stations and may be used in various ways according to different
combinations of action bits. In a first usage, a receiving base station (target BS) may be
assigned to a specific paging group (e.g., Action=0). In a second usage, a receiving base
station may be removed from a specific paging group (e.g., Action=l). In a third usage,
a receiving base station may be queried regarding to which group the receiving base
station belongs (e.g., Action=2). In a fourth usage, a receiving base station may be
informed regarding to which paging group a transmitting base station (sender BS)
belongs (e.g., Action=3).
Since a base station may belong to one or more paging zones, the inter-base-
station message may include information related to a plurality of paging groups. Via the
inter-base-station message, base stations may be informed of a paging cycle and a
paging offset used in each paging zone. Furthermore, base stations may be dynamically
assigned to paging groups using the inter-base-station message.
When entering idle mode, a mobile station uses a deregistration request (e.g.,
DREG-REQ) message, such as that shown in the below Table 5.
[Table 5]
Referring to Table 5, a mobile station sets a deregistration request code of the
deregistration request message to 0x01, for example, and then delivers the message to a
base station to request entrance to idle mode. The mobile station may accordingly
deliver a preferred paging cycle. The base station receives the message and may respond
to the request from the mobile station via a deregistration command (e.g., DREG-CMD)
message, such as that shown in the below Table 6.
[Table 6]
Referring to Table 6, the base station may allow the mobile station to enter the
idle mode via Action Code (e.g., Action Code=0x05) of the deregistration command
(e.g., DREG-CMD) message. Alternatively, the mobile station may request to enter the
idle mode after a prescribed duration (e.g., Action Code=0x06). Alternatively, the
mobile station may not request to enter the idle mode until transmitting the
deregistration command message (e.g., Action Code=0x07). Exemplary action codes of
the deregistration command message are shown in the below Table 7.
[Table 7]
A paging group ID (e.g., Paging Group ID), a paging cycle (e.g., Paging_Cycle)
and a paging offset value (e.g., Paging_Offset), which should be maintained during the
idle mode by the mobile station, may be delivered via a TLV (type length value) item
that may be selectively included in the deregistration message.
The mobile station may then receive a paging advertising (e.g., MOB-PAG-
ADV) message, such as that shown in the below Table 8 during a predefined paging
cycle and paging offset to maintain or terminate the idle mode.
[Table 8]
A wireless access system may define a protocol of a medium access control
(MAC) layer and a physical (PHY) layer for a point-to-multipoint connection between a
base station and a mobile station.
FIG. 1 is a block diagram illustrating protocol layers for use in a wireless access
system, according to an embodiment of the present invention.
Referring to FIG. 1, an uppermost part of a MAC layer is a service specific
convergence sublayer, operative to convert various packet data of an upper core network
to a common protocol data unit (PDU) format according to the MAC specification and
to compress a header of the corresponding packet.
A physical layer of the wireless access system may be classified into a single
carrier system and a multi-carrier system (e.g., OFDM/OFDMA). The multi-carrier
system may use orthogonal frequency division multiplexing (OFDM), capable of
allocating resources by subchannel unit grouping. OFDM, in turn, enables orthogonal
frequency division multiple access (OFDMA).
Table 9, below, shows common physical layer characteristics between OFDM
and OFDMA.
[Table 9]
Referring to Table 9, forward error correction (FEC) coding selectively uses a
concatenated code between a Reed-Solomon code (RS code) and a convolutional code
or a block turbo code (BTC) and employs a modulation system of BPSK/QPSK/16-
QAM/64-QAM. FEC coding adopts adaptive modulation/coding (AMC) to select a
modulation mode and a coding rate method according to a channel status. For AMC, a
received signal strength indication (RSSI), a carrier to interface noise ratio (CINR)
and/or a bit error rate (BER) are used in measuring channel quality.
In an OFDMA physical layer, active carriers are separated into groups and are
transmitted per group to a receiving end. The carrier group transmitted to a particular
receiving end is called a subchannel.
FIG. 2 is a diagram illustrating a subchannel of an OFDMA physical layer,
according to an embodiment of the present invention.
Referring to FIG. 2, three exemplary subchannels including subcarriers are
shown. The subcarriers configuring each of the subchannels may lie adjacent to each
other or may be spaced apart from each other at an equal distance. Thus, by enabling
multiple access by subchannel unit, complexity of implementation may increase, but
frequency diversity gain, gain according to power concentration, and forward power
control may be efficiently performed. A slot allocated to each user is defined by a data
region of a two-dimensional space. The two-dimensional space is a set of continuous
subchannels allocated by a burst.
FIG. 3 is a diagram illustrating a data region of an OFDMA physical layer,
according to an embodiment of the present invention.
Referring to FIG. 3, a data region of OFDMA may be represented by a rectangle
defined by a time coordinate and a subchannel coordinate.
FIG. 4 is a diagram illustrating mapping of an FEC block to an OFDMA
subchannel and an OFDM symbol, according to an embodiment of the present invention.
Referring to FIG. 4, the data region is assigned to an uplink of a specific user.
Alternatively, a base station may transmit the data region to the specific user. To define
such a data region in a two-dimensional space, the number of OFDM symbols in a time
domain and the number of continuous subchannels beginning from a remote location
reference point with an offset in a frequency domain may be provided.
MAC data is segmented according to a FEC block size and each FEC block is
extended to occupy three OFDM symbols on a time axis. Mapping may be sequentially
performed by increasing the subchannel number for each FEC block to arrive at the end
of the data region. Upon reaching the end of the data region, the mapping continues to
be performed from an OFDM symbol with a one-step lower number.
FIG. 5 is a diagram illustrating a frame structure of an OFDMA physical layer
in a wireless access system, according to an embodiment of the present invention.
Referring to FIG. 5, a downlink subframe starts with a preamble used in
synchronization and equalization of a physical layer and then defines a structure of an
overall frame via broadcast downlink map (e.g., DL-MAP) and uplink map (e.g., UL-
MAP) messages that define locations and usages of bursts assigned to a downlink and
an uplink, respectively.
Table 10 and Table 11, below, show exemplary of DL-MAP and UL-MAP
messages, respectively.
[Table 10]
[Table 11]
A DL-MAP message defines a usage assigned to each burst for a downlink
section in a burst mode physical layer, and a UL-MAP message defines a usage of a
burst assigned to an uplink section.
Table 12, below, shows an exemplary DL-MAP information element (e.g., DL-
MAP IE).
[Table 12]
In the information elements (IE) for configuring a DL-MAP message shown in
Table 12, a downlink traffic section is divided at a user end by a downlink interval
usage code (e.g., DIUC), a connection ID (e.g., CID), and burst location information
(e.g., subchannel offset, symbol offset, subchannel number, symbol number).
Furthermore, in the information elements for configuring a UL-MAP message
shown in Table 13, a usage is decided for each CID by UIUC and a location of a
corresponding section is specified by a certain duration. In such case, a per-section
usage is determined according to a UIDC value used in the UL-MAP. Each section
begins from a point remote from a previous IE start point according to a duration
specified by the UL-MAP IE.
[Table 13]
A downlink channel descriptor (e.g., DCD) message includes a modulation type
and an FEC code type as physical layer associated parameters to be applied to a burst
section assigned to a downlink. An uplink channel descriptor (e.g., UCD) message
includes a modulation type and an FEC code type as physical layer associated
parameters to be applied to a burst section assigned to an uplink. Moreover, parameters
(e.g., 'K', 'R' etc. for R-S code) needed for various forward error correction (FEC) code
types are specified. Such parameters are provided by a burst profile specified per UIUC
(uplink interval usage code) or DIUC (downlink interval usage code) within UCD or
DCD.
Table 14 and Table 15 show examples of DCD and UCD, respectively.
[Table 14]
[Table 15]
Each of the DCD and UCD messages are not transmitted each frame but is
periodically transmitted at a cycle of maximum 10 seconds. Values of Configuration
Change Count included in the DCD and UCD messages are equal to the count values
included in the DL-MAP and UL-MAP shown in the above Table 10 and Table 11,
respectively. Thus, a mobile station may recognize whether the configurations are
changed via the Configuration Change Count values included in the DL-MAP and the
UL-MAP, respectively. If the Configuration Change Count value included in the DL-
MAP or the UL-MAP is changed, the mobile station receives the DCD or UCD message.
A MAC layer of a wireless access system is described below. A CS (service-
specific convergence sublayer) is a layer existing on a MAC CPS (common part
sublayer). The CS performs PDU reception from an upper layer, classification of upper
layer PDU, handling of the upper layer PDU based on the classification, delivery of a
CS PDU to an appropriate MAC SAP, and reception of the CS PDU from a peer entity.
The CS is operative in classifying the upper layer PDU per connection, compressing
information of a payload header optionally and/or restoring the compressed header
information.
The MAC CPS maps each packet to a suitable service flow in packet
transmission between a mobile station and a base station on a connection basis and
offers a quality of service (QoS) that varies according to the service flow on the
connection basis. A MAC PDU format defined in the MAC CPS is described below.
FIG. 6A is a diagram illustrating a MAC PDU format, according to an
embodiment of the present invention. FIG. 6B is a diagram illustrating a MAC
management message format, according to an embodiment of the present invention.
Referring to FIGS. 6 A and 6B, MAC PDUs may be classified into a MAC
management PDU and a user data MAC PDU. The MAC management PDU uses a
MAC management message, which is previously specified for an action of a MAC layer,
as a payload. A MAC header is attached to a front end of each payload. A band request
PDU, which is needed to dynamically request a band necessary for each subscriber
adding uplink, corresponds to a specifically formatted MAC management PDU having
only a header called a band request header without a separate payload. A packet PDU
corresponding to user data is mapped to a payload of a MAC SDU. The packet PDU
becomes the MAC PDU by attachment of the MAC header and CRC.
FIG. 6C is a diagram illustrating a plurality of concatenated MAC PDUs for
transmission as an uplink burst, according to an embodiment of the present invention.
Referring to FIG. 6C5 each MAC PDU is identified by a unique connection
identifier (CID). A MAC management message, a band request PDU, and/or user data
(user PDU) may be concatenated to the same burst.
The MAC management message includes a field to indicate a management
message type and a management message payload. Among management messages,
DCD, UCD, UL-MAP, and DL-MAP correspond to the representative management
messages that directly specify the frame structure, the band assignment and the physical
layer parameters.
FIG. 7 is a signal flow diagram illustrating idle mode action in a mobile station,
according to an embodiment of the present invention.
Referring to FIG. 7, a mobile station requests a base station for transition to
sleep mode, maintains the sleep mode, and then terminates the sleep mode when
downlink traffic intended for the mobile station is present, as further described below.
A mobile station sets a sleep request message to values of an initial sleep
interval, a final sleep interval, and a listening interval and then delivers the set message
to a base station to request a transition to sleep mode (S701). In a case where the sleep
mode transition is approved, the base station delivers a sleep response message (S702)
set to the initial sleep interval, the final sleep interval, the listening interval, and a sleep
mode transition start time (start time offset).
When the sleep mode transition start time occurs, the mobile station receives
and decodes all frames during the listening interval. When the initial sleep interval
expires, the mobile station receives a traffic indicating message (S703) from the base
station for the listening interval. If there is no downlink traffic intended for the mobile
station, the mobile station maintains the sleep mode for a period twice the length of the
initial sleep interval, for example.
Under the above condition (e.g., a next sleep interval set twice as long as a
previous sleep interval), the sleep interval continues to increase. After the final sleep
interval set by the sleep response message ends, the final sleep interval is repeated as a
next sleep interval. The final sleep interval may be determined by the below Formula 1
via parameters of the sleep response message.
[Formula 1]
final sleep window = final sleep window base * 2 final window exponent
In a case where downlink traffic intended for the mobile station is present, as
indicated via a traffic indicating message, the mobile station terminates the sleep mode
and receives the downlink traffic in normal mode.
Actions of the idle mode are described below.
A paging zone is defined as an overall area covered by base stations included in
a set (e.g., a paging group). The base stations belonging to the same paging group have
the same paging cycle (e.g., Paging_Cycle) and the same paging offset (e.g.,
Paging_Offset).
A mobile station may request a base station for transition to idle mode. The
base station then delivers a paging group ID (e.g., Paging Group ID), a paging cycle
according to the paging group ID, and a paging offset according to the paging group ID
to the mobile station to enable entry to idle mode. During idle mode, the mobile station
may determine whether to maintain idle mode or terminate idle mode via a broadcast
paging advertising message delivered from the base station at each paging cycle.
In a case where uplink traffic is present for the mobile station in idle mode to
transmit, the mobile station may terminate the idle mode. In a case where downlink
~ 2,0 ~
traffic intended for the mobile station in idle mode is present, the base station may
instruct the mobile station to terminate idle mode via the paging advertising message. In
a case where the paging advertising message is not received by the mobile station at a
certain time (for example, if the mobile station in idle mode moves to another paging
zone or loses synchronization to the base station), the mobile station terminates the idle
mode.
To minimize power consumption, a method for early notification of the validity
of the traffic indicating message and paging messages periodically delivered to the
mobile stations in sleep or idle mode, is provided. Accordingly, early notification
information having a suitable length is configured by appropriately grouping the mobile
stations in sleep or idle modes. The early notification information may be delivered to
the mobile stations in sleep or idle mode via a downlink frame.
The early notification information may be delivered in a broadcast via the
downlink frame. If the length of the early notification information is excessive, radio
resources may be wasted. Therefore, configuring early notification information having a
suitable length is provided. To configure early notification information having a suitable
length, a 48-bit MAC address allocated to each mobile station may be used as an
indicator to identify mobile stations in sleep or idle mode, for example.
The number of groups used to classify mobile stations in sleep or idle mode
may be expressed by 'N_Group', for example, hi grouping the mobile stations, the
respective MAC address of the mobile stations may be used for reference, regardless of
whether the mobile stations is in sleep or idle mode. Consequently, a group index (e.g.,
Group_Index) of a group to which a certain mobile station in sleep or idle mode belongs
may be determined using the below Formula 2.
[Formula 2]
Grouρ_Index = (MAC address) modulo N_Group
In Formula 2, 'Groupjhidex' means a remainder resulting from dividing a
MAC address of a corresponding mobile station by the number of groups N_Group.
Hence, a value of Group_Index ranges between 0 and (N_Group-l).
For example, in a case where mobile stations in sleep or idle mode are
classified into ten groups (e.g., N_Group=10), a mobile station having a MAC address
of '102' belongs to a 2nd group by '10 modulo (102)'. After completion of the above
grouping procedure, a base station may configure a flag for early notification of mobile
stations belonging to each group. The length of the flag (e.g., a bit number) is equal to
the number of groups. Thus, the length of flag may be determined by 'N_Group'.
If a mobile station that must decode a traffic indicating message or a paging
advertising message is present among a plurality of mobile stations belonging to a
certain group (e.g., if there exists mobile station(s) unable to maintain a sleep or idle
mode), a base station may set a flag for the group to which the corresponding mobile
station belongs to 'positive notification', for example. In such case, the positive
notification may be expressed as ' 1 ' .
If no mobile stations belonging to a certain group need to decode a traffic
indicating message or a paging advertising message, the base station may set a flag for
the corresponding group to 'negative notification', for example. In this case, the
negative notification may be expressed as O'.
In a preferred embodiment of the present invention, it is assumed that five
mobile stations are present having MAC addresses 1, 2, 3, 4 and 5, respectively, and that
the mobile station having the MAC address 3 in the current frame is instructed to
decode a traffic indicating message and a paging advertising message. If the five mobile
stations are classified into two groups (i.e., N_Group=2), Group_Index of the mobile
station having the MAC address 2 is set to 0, Group_Index of the mobile station having
the MAC address 4 is set to 0, and each Group_Index of the mobile stations having the
MAC addresses 1 , 3 and 5, respectively, is set to 1 , for example.
To deliver a positive notification to the mobile station having the MAC address
3, a base station sets a flag having a Group_Index of 1 among 2-bit flags to 'positive'.
Therefore, the base station may set flags such as those shown in the below Table 16, for
example.
[Table 16]
The flags may be delivered to the five mobile stations in a broadcast. The
mobile station having a Group_Index with a flag set to 'negative' does not decode the
traffic indicating message or the paging message included in a corresponding downlink
frame.
As explained in the above embodiment, mobile stations may avoid unnecessary
decoding of the traffic indicating message and the paging message via an early
notification flag. Nonetheless, mobile stations belonging to the group set to 'positive'
still decode the traffic indicating message and the paging message.
Furthermore, to increase efficiency via the early notification flag, another
preferred embodiment may be implemented. In the embodiment, a base station is
assumed to know the total number of mobile stations in sleep or idle mode and the
number of mobile stations needing to be set to 'positive' in a current frame. Thus, the
- -
base station may determine the number of groups (N_Grouρ) based on the preceding
numbers. By regrouping mobile stations having a Group_Index set to 'positive', the
base station may improve accuracy of the early notification. Accordingly, the mobile
stations having a Group_Index set to 'positive' are classified into N_Positive_Group
groups. An identifier for identifying each of the N_Positive_Group groups may be
defined as a Positive_Group_Index.
In the above embodiment, the mobile stations having Group_Index set to
'positive' are regrouped into N_Positive_Group=3 groups, the mobile station having the
MAC address 1 belongs to the group of which Positive_Group_Index is 1, the mobile
station having the MAC address 3 belongs to the group of which Positive_Group_Index
is 0, and the mobile station having the MAC address 5 belongs to the group of which
Positive_Group__Index is 2, based on Formula 2. Therefore, a final early notification
flag may have a format such as that shown in the below Table 17.
[Table 17]
Consequently, if the base station transmits the early notification flag to the
mobile stations in sleep or idle mode together with values of N_Group and
N_Positive_Group, the mobile stations belonging to the group set to 'positive' decode
the corresponding traffic indicating message and the paging message. However, the
mobile stations belonging to the group set to 'negative' may minimize power
consumption by not decoding the messages.
In a case where a mobile station in idle mode needs to receive a DCD/UCD
message, the early notification flag may include information indicating whether the
DCD/UCD message is transmitted in a current frame.
In order for a mobile station in idle mode to enter a network more quickly in
case of uplink/do wnlink traffic occurrence, DCD/UCD variables of a base station within
which the mobile station lies may be stored in the mobile station. Thus, the mobile
station needs to receive the DCD/UCD message whenever the DCD/UCD variables are
changed. The DCD/UCD variables may be changed if the mobile station lies within the
same base station area and/or if the mobile station enters another base station area
belonging to the same paging group.
FIG. 8 is a diagram illustrating a mobile station in idle mode receiving a
DCD/UCD message, according to an embodiment of the present invention.
Referring to FIG. 8, DCD/UCD is transmitted by the same cycle of a variable
called a DCD/UCD transmission cycle (e.g., DCD/UCD Interval). To know whether a
DCD/UCD message is included in a current frame, a mobile station decodes a burst.
Mobile stations in idle mode may determine whether the DCD/UCD is changed using a
DCD count transmitted via a DL-MAP message but may not determine whether the
received message relates to the DCD/UCD until decoding at least part of the burst. Thus,
the mobile station in idle mode should decode all messages broadcast in a downlink
frame until receiving the DCD/UCD message. Thus, significant power consumption
may occur.
FIG. 9 is a diagram illustrating a mobile station in idle mode receiving a
DCD/UCD message, according to another embodiment of the present invention.
Referring to FIG. 9, the base station may transmit information indicating
whether a DCD/UCD message is included in a current frame using an early notification
flag. The information indicating whether the DCD/UCD message is included in the
current frame may be transmitted using a DCD/UCD indicator (e.g., DCD/UCD
Indication) of the early notification flag. Therefore, a mobile station may minimize
power consumption by confirming the DCD/UCD Indication of the early notification
flag and then decoding messages broadcast within a downlink frame having the
corresponding value set to 1, for example.
Table 18 shows an exemplary early notification flag.
[Table 18]
The early notification flag may be included as one information element (IE)
included in the DL-MAP message or may be delivered in a separate broadcast message
at the initiation of a downlink frame. Alternatively, the early notification flag may be
delivered over a broadcast channel.
FIG. 10 is a generalized block diagram of a mobile station 1000, according to an
embodiment of the present invention. The methods described herein may be
performed using the mobile station 1000, for example.
Referring to FIG. 10, the mobile station 1000 includes a transmitter 1010 and a
receiver 1060, which operate in conjunction. A processor 1015, which performs
control functions, may be shared by the transmitter 1010 and the receiver 1060.
Alternatively, the transmitter 1010 and the receiver 1060 may have separate processors.
A display 1017, an interface 1019, a speaker 1021, and a microphone 1022 are
operatively coupled to the processor to enable operation of the mobile station 1000 by
the user. A channel coding and a channel decoding 1025 and 1075, respectively, are
operatively coupled to the processor to add redundancy bits, for example, and perform
error correction. A symbol mapping and a symbol demapping 1030 and 1080,
respectively, are operatively coupled to the channel coding and the channel decoding
1025 and 1075, respectively, and serve to map bits to signals, such as QPSK and
16QAM, for example. A subchannel modulation and a subchannel demodulation 1035
and 1085, respectively, are operatively coupled to the symbol mapping and the symbol
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demapping 1030 and 1080, respectively, and serve to map signals to OFDMA
subcarriers. An IFFT (inverse fast fourier transform) and an FFT (fast fourier
transform) 1040 and 1087, respectively, are operatively coupled to the subchannel
modulation and the subchannel demodulation 1035 and 1085, respectively, and serve to
generate an OFDM wave-formed signal by combining multiple subcarriers. The
mobile station 1000 also includes filters 1045 and 1089, a digital to analog converter
(DAC) 1050, an analog to digital converter (ADC) 1091, and radio frequency
converters (RFs) 1055 and 1093.
In one embodiment, a method for controlling an idle mode in a mobile station
comprises transmitting an idle mode request to a serving base station to enter the idle
mode, and receiving a decode information transmission frame value and a decode
information change status from at least one base station. The method also comprises,
if the decode information change status indicates a change in the decode information,
maintaining the idle mode, and receiving the decode information from the at least one
base station when the transmission frame value is reached.
The decode information may comprise at least one of downlink channel
descriptor (DCD) information and uplink channel descriptor (UCD) information. The
decode information may comprise forward error correction (FEC) code type
information. The transmission frame value may comprise a frame number. The
transmission frame value may comprise a frame offset. The at least one base station
may be in a same paging group. The method may further comprise maintaining the
idle mode if the decode information change status indicates no change in the decode
information.
In another embodiment, a method in a network for controlling an idle mode in a
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mobile station comprises receiving an idle mode request from a mobile station to enter
the idle mode, and transmitting a decode information transmission frame value and a
decode information change status to the mobile station. If the decode information
change status indicates a change in the decode information, the mobile station maintains
the idle mode. The method also comprises transmitting the decode information to the
mobile station when the transmission frame value is reached.
The network may comprise at least one base station and a paging controller, the
paging controller configured to control paging within base stations of a paging group.
The decode information transmission frame value and the decode information change
status may be broadcast to the mobile station at each paging interval.
Accordingly, the present invention provides early notification of channel
descriptor information from a base station to a mobile station to reduce decoding by the
mobile station. Power consumption may thus be reduced and communications may be
performed more efficiently.
It will be apparent to those skilled in the art that various modifications and
variations may be made in the present invention without departing from the spirit or
scope of the inventions. Thus, it is intended that the present invention covers the
modifications and variations of this invention provided they come within the scope of
the appended claims and their equivalents.
INDERSTRIAL APPLICABILITY
The present invention can be applied to a broadband wireless access system.