WO2006071096A1

WO2006071096A1 - A method of updating channel information by a mobile station that is in power saving mode

Info

Publication number: WO2006071096A1
Application number: PCT/KR2005/004671
Authority: WO
Inventors: Beom Joon Kim; Ki Seon Ryu; Yong Ho Kim; Yong Won Kwak; Ki Hyoung Cho
Original assignee: Lg Electronics Inc.
Priority date: 2004-12-30
Filing date: 2005-12-30
Publication date: 2006-07-06
Also published as: US20090197601A1; US7630729B2; US7630740B2; US20090185519A1; CA2585153A1; AU2005320380B2; CA2585153C; US20090191908A1; EP1832143A4; US20090191909A1; US7937100B2; EP2364046A3; US20110009144A1; US20070168577A1; EP1832143B1; AU2005320380A1; US7684812B2; US20060194598A1; US7822429B2; US7711379B2

Abstract

A method of updating channel information by a mobile station (MS) that is in power saving mode is disclosed. More specifically, the method includes the MS which receives status information of a first channel descriptor and transmission frame information which includes when the first channel descriptor is to be transmitted. Furthermore, the MS compares status information of the first channel descriptor with status information of a second channel descriptor. Here, the second channel descriptor is stored in the MS. Lastly, if the compared status information are different, the MS receives the first channel descriptor according to the transmission frame information.

Description

_i

A METHOD OF UPDATING CHANNEL INFORMATION BY A MOBILE

STATION THAT IS IN POWER SAVING MODE

Technical Field

The present invention relates to a method of updating channel information, and

more particularly, to a method of updating channel information by a mobile station that

is in power saving mode.

Background Art

In a Broadband Wireless Access System, an operation of a power saving mode

is as follows. A paging zone refers to all the paging areas covered by a plurality of base

stations. Here, all the base stations in the same paging zone share a same paging cycle

(i.e., Paging_Cycle) and a same paging offset (i.e., Paging_Offset).

In the system, a mobile station (MS) can request to enter a power saving mode

from the base station (BS). The BS can then permit the MS to enter the power saving

mode by transmitting its paging group identification (i.e, Paging_Group_ID) and the

paging cycle and the paging offset, both corresponding to the paging group ID. Upon

receiving the paging group ID, the corresponding paging cycle, and the corresponding

paging offset, the MS can then enter the power saving mode.

During the power saving mode, the MS receives a broadcast message in a form

of a paging broadcast message (i.e., MOB-PAG-ADV) from the BS at specified paging

cycle. From the paging broadcast message, the MS can determine whether to maintain

or terminate the power saving mode. If a situation arises where the MS has to send uplink traffic to the BS, the MS

can terminate the power saving mode anytime. Conversely, if a situation arises where

the MS, which is in the power saving mode, has to receive downlink traffic from the

BS, the BS sends the paging broadcast message to instruct the MS to terminate the

power saving mode.

Alternatively, if the MS, which is in a power saving mode fails to receive the

paging broadcast message at the specified time as a result of moving to another paging

zone or by failure to synchronize, then the MS has to terminate the power saving mode.

Disclosure of the Invention

Accordingly, the present invention is directed to a method of updating channel

information by a mobile station that is in power saving 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 a method of updating channel

information by a mobile station that is in power saving mode.

Another object of the present invention is to provide a method of providing

channel information by a base station to a mobile station that is in power saving mode.

A further object of the present invention is to provide an apparatus for updating

channel information by a mobile station that is in power saving mode.

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, a method of

updating channel information by a mobile station (MS) that is in power saving mode

includes the MS which receives status information of a first channel descriptor and a

transmission frame information which includes when the first channel descriptor is to

be transmitted. Furthermore, the MS compares status information of the first channel

descriptor with status information of a second channel descriptor. Here, the second

channel descriptor is stored in the MS. Lastly, if the compared status information are

different, the MS receives the first channel descriptor according to the transmission

frame information.

In another aspect of the present invention, a method of providing channel

information by a base station (BS) to a mobile station (MS) that is in power saving

mode, includes the BS which transmits status information of a first channel descriptor

and transmission frame information which includes when the first channel descriptor is

to be transmitted. Moreover, the BS transmits the first channel descriptor according to

the transmission frame information.

Yet, in another aspect of the present invention, an apparatus for updating

channel information where the apparatus is in power saving mode. The apparatus

includes a receiver for receiving status information of a first channel descriptor and a

be transmitted, hi addition, the apparatus includes a comparator for comparing status information of the first channel descriptor with status information of a second channel

descriptor. Here, the second channel descriptor is stored in a memory of the MS. Lastly,

the receiver is used to receive the first channel descriptor according to the transmission

frame information, if the compared status information from the comparator are

different.

Another aspect of the present invention includes a method of updating channel

information by a mobile station (MS) that is in power saving mode. In the method, the

MS receives status information of a channel descriptor and a transmission frame

information which includes when the channel descriptor is to be transmitted.

Furthermore, the MS recognizes a change in the status information of the channel

descriptor since a last decoded status information. Lastly, the MS receives the channel

descriptor according to the transmission frame information.

In another aspect of the present invention, a method of updating channel

information by a mobile station (MS) that is in power saving mode includes the MS

which receives a transmission frame information which includes a specified frame at

which a channel descriptor is to be transmitted. Moreover, the MS recognizes the

specified frame for receiving the channel descriptor which contains information

different from channel descriptor information stored in the MS. Lastly, the MS

receives the channel descriptor at the specified frame.

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 embodiment(s) of the invention and together with the description

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

FIG. 1 is a diagram illustrating an example of an operation of a power saving

mode according to updated status information of a DCD/UCD;

FIG. 2 illustrates an example of a transmission operation of a paging broadcast

message or a common downlink notification DL-MAP IE;

FIG. 3 is a diagram illustrating an example of an operation of a DCD/UCD

transmission offset;

FIG. 4 illustrates is a diagram illustrating an example of a paging cycle

synchronized to a DCD/UCD transmission cycle;

FIG. 5 is a diagram illustrating an example of an initial ranging operation by

the MS according to coding scheme and modulation schemes changes in the BS; and

FIG. 6 is diagram illustrating an example of an operation using a frame number

instead of a DCD/UCD transmission offset.

FIG. 7 is a diagram illustrating an example of an apparatus in a power saving

mode which updates channel information.

Best Mode for Carrying Out the Invention

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

present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings

to refer to the same or like parts.

In connection with the present invention, a more detailed description of a

power saving mode as well as a Downlink Channel Descriptor (DCD) and an Uplink

Channel Descriptor (UCD) is provided in an IEEE 802.16e specification document.

As described above, the MS in a power saving mode receives a paging

broadcast message (i.e., MOB_PAG_ADV), which is transmitted according to a

paging cycle, from the BS in the paging zone. Here, the power saving mode can be an

idle mode or a sleep mode.

Table 1 represents an example of a P aging-Group- Action message for forming

a paging zone. Here, the base stations can transmit messages between each other via a

wired connection (e.g., a cable).

[Table 1]

The messages transmitted between the base stations can be used for following

four purposes based on the indication of action bits. That is, if an action field indicates

that Action = 0, then the message can include a command to assign a target BS to a

specified paging group. Here, the target BS is the BS that receives the message from

another BS. On the contrary, if the action field indicates that Action = 1, then the

message can include a command to remove or exclude the target BS from a specified paging group. Furthermore, if the action field indicates that Action = 2, then the

message can include a query as to which paging group the target BS belongs. Lastly, if

the action field indicates that Action = 3, then the message can include information as

to which paging group a sender BS belongs. Here, the sender BS is the BS that

transmits the message from another BS.

Because one BS can belong to more than one paging group, a paging-group-

action message can include information on a plurality of paging groups. In addition,

the base stations can gain access to the paging cycle and the paging offset of each

paging zone from the paging-group-action, which is shared by base stations.

Table 2 is an example of a deregistration request message (i.e., DREG_REQ),

which is a message by the MS to request to enter a power saving mode.

[Table 2]

According to Table 2, the MS can set a De-Registration Request Code of the

DREG_REQ message to 'OxOl₅' and request for deregistration from a serving BS. That

is, the MS requests the BS for permission to enter a power saving mode. Here, the

serving BS refers to the BS which sends paging information to mobile stations in its

coverage area. In addition, the MS can send its preferred paging cycle in the

DREG_REQ message.

Table 3 is an example of a deregistration command message (i.e.,

DREG_CMD).

[Table 3]

Using an 'Action Code' of the DREG_CMD message, the BS can permit the

MS to enter a power saving mode (e.g., Action Code = 0x05), have the MS request

again the request to enter a power saving mode (e.g., Action Code = 0x06), or have the MS wait (or cease the requests to enter the power saving mode) until the BS transmits

the DREG_CMD message (e.g., Action Code = 0x07).

Table 4 is an example of action codes of a deregistration command (i.e.,

DREG_CMD) message.

[Table 4]

By using a type-length-fϊeld (TLV) parameters, which can be selectively

included in the DREG_CMD message, a paging group ID, a paging cycle, and a

paging offset can be transmitted to the MS. The paging group ID, the paging cycle, and

the paging offset must be kept (unchanged) while the corresponding MS is in the

power saving mode. After the MS enters the power saving mode, the MS receives a

paging broadcast (i.e., MOB-PAG-ADV) message at specified paging cycle(s) and at

specified paging offset. Based on the paging broadcast message, the MS can remain in

or terminate the power saving mode.

Table 5 represents an example of a paging broadcast (i.e., MOB-PAG-ADV)

message.

[Table 5]

In the Broadband Wireless Access System, the MS has to receive a Downlink

Channel Descriptor/Uplink Channel Descriptor (DCD/UCD) for network entry when

the MS turns on power and for network re-entry in performing operations such as

handover.

Table 6 is an example of a Downlink Channel Descriptor (DCD).

[Table 6]

Table 7 is an example of an Uplink Channel Descriptor (UCD).

[Table 7]

The DCD/UCD messages are physical layers parameters which apply to each

allocated burst intervals for downlink and uplink. Moreover, the DCD/UCD messages

include information on a modulation scheme and a Forward Error Correction (FEC)

code type. Furthermore, using the DCD/UCD messages, necessary parameters (e.g., K

and R values of a RS code) are provided according to various FEC code types. These

types of parameters can be provided via Burst Profile. Here, the Burst Profile is

provided for each Uplink Interval Usage Code (UIUC) and Downlink Interval Usage

Code (DIUC) from the UCD and the DCD.

The status information or the parameters and setting that can be included in the

DCD/UCD messages can vary depending on the physical layers. As such, the

parameters or settings provided in Tables 8 and 9 can be included in a 'TLV Encoded

Information for the overall channel' field of each message.

Table 8 is an example of parameters included in a 'TLV Encoded Information

for the overall channel' field of the DCD message in an Orthogonal Frequency

Division Multiple Access (OFDMA).

[Table 8]

Table 9 is an example of settings or parameters included in a 'TLV Encoded

Information for the overall channel' field of the UCD message in an Orthogonal

Frequency Division Multiple Access (OFDMA).

[Table 9]

In the system, the DCD/UCD messages are not limited to settings or parameters

contained in Tables 8 and 9. In other words, the DCD/UCD messages can include other

information besides the information listed in Tables 8 and 9.

As shown in Table 6 - Table 9, the DCD/UCD message contains large volumes

of information. As such, it would be inefficient for the MS to decode every DCD/UCD

messages received. Furthermore, the DCD/UCD message of Tables 6 and 7 includes

Configuration Change Count parameter. Here, the Configuration Change Counter can

increase by increments of one (1) if the value(s) contained in the current DCD/UCD

message is (are) different from the value(s) contained in a previous DCD/UCD

message. In other words, if the MS recognizes that there is change in status

information of a received DCC/UCD from status information of the DCD/UCD stored

in the MS, then the Configuration Change Counter increases by a specified increment.

The settings or parameters can also be referred to as status information.

As discussed above, lengths of the DCD/UCD messages are not only long but

information contained in the DCD/UCD messages are relatively constant. That is, the

DCD/UCD messages generally do not change often. Therefore, the DCD/UCD

messages are not transmitted in every frame, and more realistically, the DCD/UCD

messages are transmitted periodically with a maximum period of 10 seconds, for

example. As for the BS, the BS transmits the DCD/UCD message containing a new

status information (or new values) after waiting a specified time period so that all

mobile stations in its cell coverage area can receive the DCD/UCD message. Here, the

Configuration Change Counter included in the DCDAJCD message increases by an

increment of 1). Thereafter, the BS applies the updated or changed status information

of the DCD/UCD to the burst profile of the uplink/downlink frame(s).

As shown in Table 10 and Table 11, the updated status information can be

provided to the MS by using a DL-MAP message and a 'DCD/UCD Count' field

included in an UL-MAP message. Since the DL-MAP message and the UL-MAP

message are encoded with predefined values of the physical layer, the MS can decode

the changed status information in the DCD message and the UCD message.

Table 10 is an example of a DL-MAP.

[Table 10]

Table 11 is an example of an UL-MAP.

[Table 11]

After the MS receives an updated DL-MAP/UL-MAP having status

information different from that of the previous status information, the MS uses the

status information (or values) included in the last received DCD/UCD message to

decode the bursts included in the corresponding DL-MAP/UL-MAP.

Figure 1 is a diagram illustrating an example of an operation of a power saving

mode according to updated status information of a DCD/UCD.

If the paging broadcast message is configured to be transmitted using a

predetermined coding and modulation schemes, then the MS in the power saving mode

can still receive the paging broadcast message even if no DCD/UCD message is

received.

However, if the predetermined coding and modulation schemes are not used,

the MS in the power saving mode does not receive a DCD/UCD message, and the BS

changes (or updates) the coding and modulation schemes, the MS has to terminate the

power saving mode since the MS is unable to decode the paging broadcast message.

Alternatively, if the MS belongs to the same paging group but moves to a cell using

different coding and modulation schemes, the MS has to terminate the power saving

mode since the MS cannot decode the paging broadcast message. Alternatively, if the

MS in the power saving mode does not receive any DCD/UCD messages, the re-entry

to the network by the MS can take additional time since the MS has to receive the

DCD/UCD message in order to receive the current coding and modulation schemes. As such, it seems necessary and practical for the MS in the power saving mode to be able

to receive the DCD/UCD messages.

If the MS is configured to receive the DCD/UCD messages while in the power

saving mode, the MS in the power saving mode can decode the downlink frame during

a specified cycle. Furthermore, if the DCD/UCD status information (or values) are

updated or changed during a Paging Unavailable Interval or if the MS has moved to

another cell within the same paging group, the MS has to continuously receive and

decode all subsequent downlink frames until the new DCD/UCD message with

updated or changed status information is received. Here, the Paging Unavailable

Interval is an interval or a period in which the MS does not receive and decode any

downlink frames in order to conserve power. Moreover, as discussed above, the

DCD/UCD message contains a Configuration Change Counter which is independently

managed by each BS. For example, a first BS and a second BS belong to the same

paging group. However, since the Configuration Change Counters independent of each

other BS, the Counter of the first BS could be indicating 2 while the Counter of the

second BS could be indicating 5. In addition, since the transmission cycle of the

DCD/UCD message can be long (e.g., up to 10 seconds per cycle), the power

consumption of the MS in the power saving mode can be significant.

Table 12 is an example of a paging broadcast message (i.e., MOB-PAG-ADV).

[Table 12]

0=Not included

The paging broadcast message of Table 12 is different from the paging

broadcast message of Table 5 in that the paging broadcast message of Table 12

includes a DCD/UCD Transmission Indication to determine whether transmission of

the DCD/UCD message is scheduled during the Paging Unavailable Interval.

If the DCD/UCD Transmission Indication is set at '1,' a DCD/UCD

Transmission Offset can be provided in a form of TLV in the paging broadcast

message, as shown in Table 13.

[Table 13]

The DCD/UCD Transmission Indication of the paging broadcasts message of

Table 12 and the DCD/UCD Transmission Offset of Table 13 can be in a form of a

common downlink notification information element (i.e.,

Common_DL_Notification_IE) DL-MAP message as provided in Table 14. The

common downlink notification information element can be included in a DL-MAP IE

which is transmitted during the paging cycle. The DCD/UCD transmission offset

bitmap is used to identify whether the offset is for the DCD or UCD.

Table 14 is an example of a common downlink notification DL-MAP message.

[Table 14]

Figure 2 illustrates an example of a transmission operation of a paging

broadcast message of Table 12 or a common downlink notification DL-MAP IE of

Table 14. Referring to Figure 2, the MS that is in the power saving mode identifies a

change in the Configuration Change Counter included in the DCD/UCD message from

the paging broadcast message received during the paging listening interval. Once the

change is identified, the MS that is in the power saving mode has to obtain the

DCD/UCD transmission indication parameters of the paging broadcast message which

is received during the paging listening interval.

If the DCD/UCD transmission identification parameter is O,' the MS knows

that no DCD/UCD message transmitted during the next paging unavailable interval.

Then the MS maintains normal power saving mode instead of waiting to receive the

UCD/DCD message until the next paging listening interval.

On the contrary, the DCD/UCD transmission identification parameter set to " 1 '

signifies that the DCD/UCD message is to be transmitted during the next paging

unavailable interval. As such, the MS does not return to paging unavailable interval

even after expiration of the listening interval until the MS receives the DCD/UCD

message. In other words, the MS stays awake (maintains listening interval) until the

DCD/UCD message is received. Upon receipt, the MS returns to the paging

unavailable interval.

Figure 3 is a diagram illustrating an example of an operation of a DCD/UCD

transmission offset of Tables 13 and 14. In Figure 3, the paging broadcast message can

indicate an exact time (or frame) of when the DCD/UCD message is to be included in the transmission of the paging broadcast message. Therefore, the corresponding mobile

stations can receive the OCDfUCD messages during the paging unavailable interval.

As another embodiment of the present invention, a DCD/UCD transmission

offset can be used, instead of the DCD/UCD transmission indication to indicate

whether the DCD/UCD message is transmitted during the paging unavailable interval.

Here, the DCD/UCD transmission indication of Table 12 is removed or not used in the

paging broadcast message. However, if the situation calls for the BS to transmit a

DCD/UCD message during the paging unavailable interval, the DCD/UCD

transmission offset TLV parameter can be included in the paging broadcast message,

and the MS stays awake or enter paging unavailable interval until the paging broadcast

message containing the DCD/UCD message is received, even after expiration of the

listening interval. Alternatively, if the BS does not transmit the DCD/UCD message

during the next paging unavailable interval, the DCD/UCD transmission offset TLV

parameter is not included in the paging broadcast message. After the MS receives this

paging broadcast message absent the DCD/UCD transmission offset TLV parameter

and recognizes that the DCD/UCD message is not expected to be transmitted during

the next paging unavailable interval. Therefore, the MS maintains normal power

saving operation mode without staying awake.

Figure 4 is a diagram illustrating an example of a paging cycle synchronized to

a DCD/UCD transmission cycle. As illustrated in Figure 4, if the paging cycle of the

power saving mode and the DCD/UCD message transmission cycle (i.e., DCD/UCD

interval) are synchronized, all mobile stations in the paging listening interval of the

power saving mode can receive the DCD/UCD messages during every paging listening interval. As such, the features of the embodiments of the present invention can be

realized without the proposed operations presented in the embodiments of the present

invention.

Figure 5 is a diagram illustrating an example of an initial ranging operation by

the MS according to coding scheme and modulation schemes changes in the BS. First,

to perform initial ranging operation, the DCD/UCD message has to be received by the

MS. Thereafter, if the MS is directed to perform initial ranging operation, then the BS

can transmit the DCD/UCD message to the MS that is in the power saving mode.

After the MS receives the ranging request message via the paging broadcast

message, the MS performs following ranging operation. First, the MS receives the

DCD/UCD message, followed by transmitting a ranging request (i.e., RNG-REQ)

message, and thereafter receives a ranging response (i.e., RNG-RSP) message. After

the ranging response message is received, the MS maintains the power saving mode.

That is, if the MS receives and successfully decodes the DCD message and the UCD

message and also receives the ranging response message, then the MS enters the

paging unavailable interval to maintain the power saving mode.

Figure 6 is diagram illustrating an example of an operation using a frame

number instead of the DCD/UCD transmission offset of Table 14. If the DCD/UCD

transmission offset is used, the transmission offset has to be 16 bits considering a 16-

bit maximum paging cycle of the power saving mode and a 10-second maximum

DCD/UCD transmission cycle (e.g., 2000 frames where 1 frame = 5milliseconds). As

for using the frame number, even if lower 8 bits are used, a frame to transmit the

DCD/UCD can be indicated, thus able to decrease the size of the transmission message. If the frame number is used instead of the DCD/UCD transmission offset,

information listed in Table 15 can be additionally included to the paging broadcast

message of Table 5 in a TLV format. Table 15 is an example of using a frame number

in a TLV format in the paging broadcast message.

[Table 15]

As described above, if the frame number is used instead of the DCD/UCD

transmission offset, Table 16 illustrates another example of the common downlink

notification (i.e., Common_DL_Notification_IE) DL-MAP IE to the example of Table

14. [Table 16]

Table 17 is an example of a Broadcasts Control Pointer IE included in the DL-

MAP message if the frame number is used instead of the OCDfUCD transmission

offset.

[Table 17]

If a DCD_UCD Configuration Change Counter setting or parameter of the

Broadcast Control Pointer IE of Table 17 is different from a DCD UCD Configuration

Change Counter setting or parameter stored in the MS, the MS receives and decodes

the OCDfUCD message transmitted from the BS even after the MS has entered the

paging unavailable interval. Here, the DCDfUCD message can be received by

synchronizing the downlink frame with the transmission frame indicated in the

Broadcast Control Pointer IE. That is, the MS awakes up or exits the paging

unavailable interval during the frame. After the UCDfDCD messages are received, the

MS returns to or enters the paging unavailable interval for maintaining the power

saving mode. However, if the MS fails to successfully decode the DCD/UCD message and if

the BS does not transmit the DCD message or the UCD message at the specified

transmission frame, the MS has to receive and decode all subsequent downlink frames

to receive the DCD message or the UCD message with updated or changed status

information or parameters. After the UCD/DCD messages are received, the MS returns

to or enters the paging unavailable interval for maintaining the power saving mode.

As illustrated in Figure 6, if the DCDAJCD message is scheduled to be

transmitted during the next paging unavailable interval (e.g., at frame A), the BS can

transmit information which includes that the message is to be transmitted via either the

paging broadcast message, the DCD/UCD transmission indication of the common

downlink notification DL-MAP IE, or the DCD/UCD transmission offset bitmap

during the next paging unavailable interval.

Furthermore, the BS can indicate the lower 8 bits of the frame number, through

which actual transmission is to take place, using the DCD transmission frame and the

UCD transmission frame. Using this scheme, the MS can receive the DCD/UCD

message transmitted to the corresponding frame even during the paging unavailable

interval.

As indicated in Table 14 and Table 16, the DCD transmission indication, the

UCD transmission indication, and the DCD/UCD transmission offset bitmap has a

length of 1 bit, 1 bit, and 2 bits, respectively. Here, information contained in the DCD

transmission indication, the UCD transmission indication, and the DCD/UCD

transmission offset bitmap can be represented by using a flag, which has a length of 2

bits. Table 18 is an example illustrating a flag.

[Table 18]

As shown in Table 18, a flag can be used to indicate whether the DCD/UCD is

scheduled during the paging unavailable interval. For example, if the flag value or

parameter is OO₃' this indicates that there is no DCD/UCD transmission scheduled

during the next paging unavailable interval. If the parameter of the flag is Ol,' this

indicates that only the DCD is scheduled for transmission. Moreover, if the flag

parameter is '10,' this indicates that only the UCD is scheduled for transmission.

Lastly, if the flag parameter is '11,' then this indicates that both the DCD and the UCD

is scheduled for transmission.

In another embodiment of the present invention, an operation of updating

channel information can be performed by an apparatus in a power saving mode. Figure

7 is an example of an apparatus in a power saving mode which is used to update channel information. In Figure 7, the apparatus includes a receiver 10 which receives

status information, such as the DCD message and/or the UCD message, of a first

channel descriptor and transmission frame information which includes when the first

channel descriptor is scheduled to be transmitted. The apparatus further includes a

comparator 20 which is used to compare status information of the first channel

channel descriptor is stored in a memory 30 of the MS. Furthermore, the receiver 10

also receives the first channel descriptor according to the transmission frame

information if the compared status information from the comparator 20 are different.

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

variations can 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.

Claims

1. A method of updating channel information by a mobile station (MS)

that is in power saving mode, the method comprising:

receiving status information of a first channel descriptor and a

transmission frame information which includes when the first channel descriptor is

scheduled to be transmitted;

comparing status information of the first channel descriptor with status

information of a second channel descriptor, wherein the second channel descriptor is

stored in the MS; and

if the compared status information are different, receiving the first

channel descriptor according to the transmission frame information.

2. The method of claim 1, further comprising maintaining power saving

mode operation before receiving the first channel descriptor.

3. The method of claim 1, further comprising maintaining power saving

mode operation after receiving the first channel descriptor.

4. The method of claim 1, further comprising if the compared status

information are the same, maintain power saving mode operation without receiving the

first channel descriptor.

5. The method of claim 1, further comprising receiving an indication

which indicates whether the first channel descriptor is scheduled to be transmitted in a

subsequent paging unavailable interval.

6. The method of claim 5, wherein the idle interval is an interval in which

communication between the MS that is in power saving mode and a base station (BS)

is unavailable.

7. The method of claim 1, wherein the status information of the first

channel descriptor and the transmission frame information are received in a paging

interval.

8. The method of claim 7, wherein the paging interval is an interval in

which a communication is established between the MS that is in power saving mode

and a base station (BS).

9. The method of claim 1, wherein the first channel descriptor is at least

one of an Uplink Channel Descriptor (UCD) and a Downlink Channel Descriptor

(DCD).

10. The method of claim 9, wherein the at least one of the UCD and the

DCD is a broadcast message.

11. The method of claim 1 , wherein the second channel descriptor is at least

one of an Uplink Channel Descriptor (UCD) and a Downlink Channel Descriptor

(DCD).

12. The method of claim 11, wherein the at least one of the UCD and the

DCD is a broadcast message.

13. The method of claim 1, wherein the first channel descriptor is a

broadcast message.

14. The method of claim 1 , wherein the power saving mode is an idle mode.

15. The method of claim 1 , wherein the power saving mode is a sleep mode.

16. The method of claim 1, wherein the transmission frame information

indicates a frame number.

17. The method of claim 1 , further comprising:

receiving and decoding every subsequent frames until the first channel

descriptor is successfully decoded if the MS unsuccessfully decodes the first channel

descriptor at a transmission frame, wherein the transmission frame corresponds to the

frame number provided by the transmission frame information; and

returning to power saving mode immediately after the successful

decoding of the first channel descriptor.

18. The method of claim 1 , further comprising:

receiving every subsequent frames until the first channel descriptor is

successfully received if no first channel descriptor was received by the MS at a

transmission frame; and

returning to power saving mode immediately after the MS successfully

receives the first channel descriptor.

19. A method of providing channel information by a base station (BS) to a

mobile station (MS) that is in power saving mode, the method comprising:

transmitting status information of a first channel descriptor and

scheduled to be transmitted; and

transmitting the first channel descriptor according to the transmission

frame information.

20. The method of claim 19, further comprising transmitting an indication

subsequent idle interval.

21. The method of claim 20, wherein the idle interval is an interval in which

communication between the MS that is in power saving mode and the BS is

unavailable.

22. The method of claim 19, wherein the status information of the first

channel descriptor and the transmission frame information are transmitted in a paging

interval.

23. The method of claim 22, wherein the paging interval is an interval in

and the BS.

24. The method of claim 19, wherein the first channel descriptor is at least

one of an Uplink Channel Descriptor (UCD) and a Downlink Channel Descriptor

(DCD).

25. The method of claim 24, wherein the at least one of the UCD and the

DCD is a broadcast message.

26. The method of claim 19, wherein the first channel descriptor is a

broadcast message.

27. The method of claim 19, wherein the status information of the first

channel descriptor and the transmission frame information is transmitted if the status

information of the first channel descriptor is different from status information of a

second channel descriptor, wherein the second channel descriptor is a previously

transmitted channel descriptor.

28. The method of claim 27, wherein the second channel descriptor is at

least one of an Uplink Channel Descriptor (UCD) and a Downlink Channel Descriptor

(DCD).

29. The method of claim 28, wherein the at least one of the UCD and the

DCD is a broadcast message.

30. An apparatus for updating channel information wherein the apparatus is

in a power saving mode, the apparatus comprising:

a receiver for:

receiving status information of a first channel descriptor and

scheduled to be transmitted, and

receiving the first channel descriptor according to the

transmission frame information, if the compared status information from a comparator

are different; and

comparator for comparing the status information of the first channel

descriptor with status information of a second channel descriptor, wherein the second

channel descriptor is stored in a memory of the MS.

31. The apparatus of claim 30, wherein the first channel descriptor is at

(DCD).

32. The apparatus of claim 30, wherein the second channel descriptor is at

(DCD).

33. A method of updating channel information by a mobile station (MS)

that is in power saving mode, the method comprising:

receiving status information of a channel descriptor and a transmission

frame information which includes when the channel descriptor is scheduled to be

transmitted;

recognizing a change in the status information of the channel descriptor

since a last decoded status information; and

receiving the channel descriptor according to the transmission frame

information.

34. The method of claim 33, wherein the transmission frame information

indicates a frame number.

35. A method of updating channel information by a mobile station (MS)

that is in power saving mode, the method comprising:

receiving a transmission frame information which includes a specified

frame at which a channel descriptor is to be transmitted;

recognizing the specified frame for receiving the channel descriptor

which contains information different from channel descriptor information stored in the

MS; and

receiving the channel descriptor at the specified frame.