WO2008060033A1 - Sleep period management method in mobile broadband wireless access system - Google Patents

Sleep period management method in mobile broadband wireless access system Download PDF

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Publication number
WO2008060033A1
WO2008060033A1 PCT/KR2007/004500 KR2007004500W WO2008060033A1 WO 2008060033 A1 WO2008060033 A1 WO 2008060033A1 KR 2007004500 W KR2007004500 W KR 2007004500W WO 2008060033 A1 WO2008060033 A1 WO 2008060033A1
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WIPO (PCT)
Prior art keywords
sleep
period
sleep mode
sleep period
terminal
Prior art date
Application number
PCT/KR2007/004500
Other languages
French (fr)
Inventor
Jae-Sun Cha
Chul-Sik Yoon
Original Assignee
Electronics And Telecommunications Research Institute
Samsung Electronics Co., Ltd.
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Publication date
Application filed by Electronics And Telecommunications Research Institute, Samsung Electronics Co., Ltd. filed Critical Electronics And Telecommunications Research Institute
Publication of WO2008060033A1 publication Critical patent/WO2008060033A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/02—Power saving arrangements
    • H04W52/0209—Power saving arrangements in terminal devices
    • H04W52/0225—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal
    • H04W52/0229—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal where the received signal is a wanted signal
    • H04W52/0232—Power saving arrangements in terminal devices using monitoring of external events, e.g. the presence of a signal where the received signal is a wanted signal according to average transmission signal activity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/28—TPC being performed according to specific parameters using user profile, e.g. mobile speed, priority or network state, e.g. standby, idle or non transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections
    • H04W76/28—Discontinuous transmission [DTX]; Discontinuous reception [DRX]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention relates to a power saving method in a mobile broadband wireless access system, and more particularly, to a sleep period management method used in a case where a power saving mode or a sleep mode (hereinafter, collectively referred to as a sleep mode) is applied in a mobile broadband wireless access system.
  • a sleep mode a sleep mode
  • a mobile broadband wireless access system is implemented in accordance with a next-generation communication scheme in which mobility is added to a local area data communication scheme such as a conventional wireless local area network (LAN) that uses a fixed access point.
  • a local area data communication scheme such as a conventional wireless local area network (LAN) that uses a fixed access point.
  • LAN wireless local area network
  • the conventional wireless LAN scheme provides a data communication scheme in which wireless communication is performed in a local area around a fixed access point.
  • the conventional wireless LAN scheme has a limitation in that it cannot provide mobility to a subscriber terminal, and it supports the local area data communication not in a wired manner but rather in a wireless manner.
  • the mobile broadband wireless access system guarantees mobility even in a case where the subscriber terminal moves from a cell covered by a current base station to another cell covered by another base station so as to provide a seamless data communication service.
  • the aforementioned mobile broadband wireless access system mainly uses a battery as a power supply unit of the subscriber terminal. Therefore, in the mobile broadband wireless access system, a short battery usage time of the subscriber terminal is an obstacle to a long-time service.
  • the mobile broadband wireless access system supports a sleep mode in which all devices in the terminal stop operating so as to save power when uplink/downlink traffic does not occur.
  • wireless channels that are set between a terminal and a base station have different qualities of service (QoS) according to traffic characteristics of the wireless channels.
  • QoS qualities of service
  • a power saving class has been introduced, so that a sleep period is managed according to the power saving class. For example, a wireless channel in which data occurs at an interval of 2 seconds and another wireless channel in which data occurs at an interval of 3 seconds correspond to different power saving classes to have different listening intervals having different periods between sleep modes so as to determine whether or not data occurs.
  • the power saving classes are classified into the below- described three types according to the required QoS. Different schemes of updating a listening period and a sleep period and different operations of receiving data in the listening period are provided to different power saving class types.
  • a power saving class Type I is associated with best effort (BE) traffic having existing Internet traffic characteristic and non-real-time variable rate (nrt-VR) traffic.
  • BE best effort
  • nrt-VR non-real-time variable rate
  • parameters that define the power saving class Type I there are an initial-sleep window, a final-sleep window base, a final-sleep window exponent, a listening window, and a start frame number for the sleep window.
  • a power saving class Type II is associated with voice over Internet protocol (VoIP) or real-time variable rate (rt-VR) traffic having a variable transmission rate.
  • VoIP voice over Internet protocol
  • rt-VR real-time variable rate
  • parameters that define the power saving class Type II there are an initial-sleep window, a listening window, and a start frame number for the sleep window.
  • a power saving class Type III is associated with a management message that is to be periodically transmitted to a terminal that is in a sleep mode, such as a downlink channel descriptor/uplink channel descriptor (DCD/UCD) and mobile neighbor base-station advertisement (MOB_NBR-ADV), or data that is to be multicasted.
  • a management message that is to be periodically transmitted to a terminal that is in a sleep mode
  • DCD/UCD downlink channel descriptor/uplink channel descriptor
  • MOB_NBR-ADV mobile neighbor base-station advertisement
  • Wireless channels of the subscriber terminal are specified with the corresponding power saving classes.
  • the power saving classes are included in the aforementioned three power saving types.
  • FIG. 1 is a signal flowchart illustrating a sleep mode management operation performed in a conventional mobile broadband wireless access system.
  • the base station 20 transmits a sleep mode response message SLP_RSP to permit the sleep mode of the subscriber terminal 10 (SI l).
  • the subscriber terminal 10 When the sleep mode approval is received from the base station 20, the subscriber terminal 10 enters into the sleep mode in which the subscriber terminal 10 does not receive data at the time of entering into the sleep mode (S 12). After an initial sleep mode, the subscriber terminal 10 enters into a listening mode and determines whether or not there is data that is to be transmitted from the base station 20 in the sleep period (S13).
  • the sleep period is an interval in which the subscriber terminal 10 is operated in the sleep mode
  • the listening period is an interval in which the subscriber terminal 10 is operated in a listening mode.
  • the base station 20 sets a message that indicates the existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S 14).
  • the subscriber terminal 10 that determines that there is no transmitted data traffic in the listening mode enters into the sleep mode (S 15).
  • the sleep period may be the same as or longer than the initial sleep period according to initial setting of the sleep mode.
  • the base station 20 performs buffering on the downlink data (S 17). Existence of the buffered data is notified to the subscriber terminal 10 when the subscriber terminal 10 is operated in the listening mode (S 18).
  • the subscriber terminal 10 determines that there is downlink data to be transmitted to the subscriber terminal 10 in the listening mode (S 16)
  • the subscriber terminal 10 terminates the sleep mode and enters into the awake mode to receive the buffered downlink data. Thereafter, the subscriber terminal 10 performs data communication with the base station 20.
  • FIG. 2 illustrates a sleep period and a listening period of a power saving class 1 included in the aforementioned power saving class Type I of a subscriber terminal that is operated in a sleep mode
  • FIG. 3 illustrates a sleep period and a listening period of a power saving class 2 included in the power saving class Type II of the subscriber terminal that is operated in the sleep mode.
  • the sleep period is increased exponentially with base 2 when the subscriber terminal maintains the sleep mode.
  • the power saving class 1 instructs the subscriber terminal to terminate the sleep mode immediately.
  • the sleep period is continuously increased when there is no downlink data.
  • the power saving class 1 does not increase the sleep period and maintains the final-sleep period.
  • the final-sleep period (final-sleep window) can be calculated by using the following
  • Equation 1 and the final-sleep window base, the final-sleep window exponent, and the like are information included in the sleep mode request message and the sleep mode response message.
  • the power saving class 2 has a listening period and a sleep period that have fixed lengths regardless of data transmission/reception in the listening period.
  • the downlink data in a data communication system such as the Internet associated with the power saving class Type I has a burst characteristic that indicates that the downlink data occurs in bursts at a predetermined time, or occurs periodically with a relatively long period. Therefore, a case where the base station receives data that is to be transmitted to a downlink from a network in the listening period means that there is no data transmission in a next period or data can occur continuously during a short period. Accordingly, although there is a data in the listening period, terminating the sleep mode is not efficient. [34] In addition, when the subscriber terminal maintains the sleep mode but does not enter into the awake mode even though data occurs in the listening period, as shown in FIG.
  • a next sleep period is increased to be twice the current sleep period. Therefore, when downlink data occurs, there is a problem in that a data transmission delay time may be increased.
  • the present invention has been made in an effort to provide an efficient sleep mode management method having advantages of maintaining a sleep mode of a terminal in a mobile broadband wireless access system without additional power consumption to increase power saving efficiency of the terminal.
  • the present invention has also been made in an effort to provide an efficient sleep period updating method having advantages of reducing a transmission delay time of downlink data that is transmitted during a sleep mode.
  • the sleep mode management method of decreasing or increasing the sleep period according to whether there is traffic that occurs in the sleep mode has advantages in that the terminal can maintain the sleep mode without additional power consumption and power saving efficiency of the terminal can be increased.
  • FIG. 1 is a flowchart illustrating a sleep mode operation performed in a conventional mobile broadband wireless access system.
  • FIG. 2 is a flowchart illustrating a sleep period and a listening period in a sleep mode of a power saving class 1 included in a power saving class Type I in a conventional mobile broadband wireless access system.
  • FIG. 3 is a flowchart illustrating a sleep period and a listening period in a sleep mode of a power saving class 2 included a power saving class Type II in a conventional mobile broadband wireless access system.
  • FIG. 4 is a flowchart illustrating a sleep period updating method of a power saving class included in a power saving class Type I in a mobile broadband wireless access system according to an embodiment of the present invention.
  • FIG. 5 is a flowchart illustrating a sleep mode management method in a mobile broadband wireless access system according to an embodiment of the present invention. Best Mode for Carrying Out the Invention
  • the present invention has been made in an effort to provide an efficient sleep mode management method having advantages of maintaining a sleep mode of a terminal in a mobile broadband wireless access system without additional power consumption to increase power saving efficiency of the terminal.
  • the present invention has also been made in an effort to provide an efficient sleep period updating method having advantages of reducing a transmission delay time of downlink data that is transmitted during a sleep mode.
  • An exemplary embodiment of the present invention provides a sleep period management method for a base station in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, including: (a) transmitting downlink data to the terminal in a listening period of the terminal that is operated in a sleep mode; and (b) after terminating the listening period in (a), decreasing a sleep period of the terminal.
  • Another embodiment of the present invention provides a sleep period management method for a terminal in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, including: (a) receiving downlink data transmitted from a base station in a listening period; and (b) after terminating the listening period in (a), decreasing a sleep period.
  • a sleep period management method in a mobile broadband wireless access system in which downlink traffic associated with a power saving class Type I, which has a burst characteristic that indicates that the downlink traffic occurs in bursts at a predetermined time, or occurs periodically with a relatively long period, is serviced.
  • FIG. 4 is a flowchart illustrating a sleep period updating method in a mobile broadband wireless access system according to an embodiment of the present invention.
  • a sleep period is increased exponentially with base 2.
  • a right- after sleep period of the terminal is decreased to be shorter than a right-before sleep period.
  • the right-after sleep period is decreased by 1/n of the right-before sleep period.
  • the value n is a sleep window decreasing ratio that indicates a decreasing ratio of the sleep period.
  • the value n may be set to a natural number of 1 or more according to a traffic characteristic of a subscriber terminal. The value n will be described later.
  • the right-before sleep period is a sleep period right before a listening period in which it is determined that downlink data traffic occurs, and the right-after sleep period means a sleep period right after the listening period.
  • a sleep period when a subscriber terminal enters into a sleep mode at first has the same value as the initial-sleep window, and the above equations are applied after the initial sleep period.
  • the sleep period updating method of decreasing the sleep period right after the downlink data occurs by 1/n as described above can be used when there is prior consent between a base station and a corresponding terminal.
  • the value n (sleep window decreasing ratio) is included in the sleep mode request message SLP-REQ and transmitted.
  • the value n is shared by the terminal and the base station. Therefore, although the downlink traffic occurs and the terminal updates the sleep period, the base station perceives this and can manage the sleep mode to correspond to the updated sleep period of the terminal.
  • FIG. 5 is flowchart illustrating a sleep mode management method in the mobile broadband wireless access system according to an embodiment of the present invention.
  • the base station 20 transmits a sleep mode response message SLP_RSP to the subscriber terminal 10 to permit the sleep mode (S21).
  • the base station 20 may add a value n that is determined to be suitable to the sleep mode response message SLP_RSP to transmit the value n together with the message to the subscriber terminal 10.
  • the base station 20 and the subscriber terminal 10 use the value n included in the sleep mode response message SLP_RSP to enter into the sleep mode.
  • the subscriber terminal 10 When sleep mode approval is received from the base station 20, the subscriber terminal 10 enters into a sleep mode in which the subscriber terminal 10 does not receive data after the time of entering into the sleep mode (S22). After an initial sleep period, the subscriber terminal 10 enters into a listening mode to determine whether or not there is data that is to be transmitted to the subscriber terminal 10 in the sleep period from the base station 20 (S23).
  • the sleep period is an interval in which the subscriber terminal 10 is operated in the sleep mode
  • the listening period means an interval in which the subscriber terminal 10 is operated in the listening mode.
  • the base station 20 sets a message that indicates existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S24).
  • the subscriber terminal 10 that determines that there is no data traffic transmitted in the listening mode then enters into the sleep mode (S25).
  • the sleep period is increased exponentially with base 2 with respect to the initial sleep period according to initial setting of the sleep mode.
  • the base station 20 may perform buffering on the downlink data (S26). Existence of the buffered data is notified (S28) when the subscriber terminal 10 is operated in the listening mode (S27).
  • the subscriber terminal 10 determines that there is the downlink data that is to be transmitted to the subscriber terminal 10 in the listening mode (S27), the subscriber terminal 10 receives the downlink data in the listening mode, decreases the sleep period, and enters into the sleep mode (S29).
  • the subscriber terminal 10 decreases the sleep mode by 1/n according to the aforementioned sleep period updating method.
  • the base station 10 predicts the updated sleep period to correspond to the value n transmitted through the sleep mode request message and manages next sleep modes according to the updated sleep period.
  • the subscriber terminal 10 After maintaining the sleep mode during the sleep period, the subscriber terminal 10 enters into the listening mode (S30), and when there is no downlink data that is to be transmitted to the subscriber terminal 10, the base station 20 sets a message that indicates the existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S31).
  • the subscriber terminal 10 that determines that there is no data traffic transmitted in the listening mode enters into the sleep mode (S32).
  • the sleep period is increased exponentially with base 2 with respect to the right-before sleep period.
  • Table 1 illustrates an example of the sleep mode request message SLP-REQ according to the embodiment of the present invention. [78] Table 1 [Table 1]
  • Table 2 illustrates an example of the aforementioned sleep mode response message SLP_RSP according to the embodiment of the present invention. [80] Table 2
  • the sleep window decreasing ratio is a ratio for decreasing the sleep period and is a value corresponding to the aforementioned n (sleep window decreasing ratio) value.
  • the sleep window decreasing ratio is newly introduced according to the embodiment of the present invention. Since the sleep window decreasing ratio is included in the sleep mode request message or the sleep mode response message and is transmitted, the updated sleep period can be shared by the base station and the subscriber terminal.
  • downlink data can be transmitted while the subscriber terminal is in the listening mode.
  • data traffic has a burst characteristic that indicates that the data traffic occurs in bursts at a predetermined time, or has a traffic characteristic that indicates that the data traffic has a relatively long period or occurs periodically.
  • a case where the base station receives a data that is to be transmitted to the downlink from a network in the listening period means that there is no data transmission in a next period or data can occur continuously during a short period.
  • the sleep mode management method of decreasing the sleep period right after traffic occurs by 1/n when the downlink data traffic occurs as described above to maintain the sleep mode of a corresponding channel has advantages in that efficient power saving control can be achieved in accordance with a traffic characteristic of the power saving class Type 1 and a transmission delay time of the downlink data can be decreased.

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Abstract

The present invention relates to a sleep period management method in a mobile broadband wireless access system. In the sleep period management method according to the present invention, a sleep period is increased or decreased when downlink data traffic that has a burst characteristic occurs while a subscriber terminal is operated in a sleep mode. The sleep period management method according to the present invention prevents the terminal from unnecessarily awaking from the sleep mode, so that power saving efficiency can be increased. In addition, when the downlink data traffic that has a burst characteristic occurs while the terminal is operated in the sleep mode, a delay time of the data transmitted to the terminal can be reduced.

Description

Description
SLEEP PERIOD MANAGEMENT METHOD IN MOBILE BROADBAND WIRELESS ACCESS SYSTEM
Technical Field
[1] The present invention relates to a power saving method in a mobile broadband wireless access system, and more particularly, to a sleep period management method used in a case where a power saving mode or a sleep mode (hereinafter, collectively referred to as a sleep mode) is applied in a mobile broadband wireless access system. Background Art
[2] A mobile broadband wireless access system is implemented in accordance with a next-generation communication scheme in which mobility is added to a local area data communication scheme such as a conventional wireless local area network (LAN) that uses a fixed access point.
[3] For the mobile broadband wireless access system, various standards have been proposed. International standards for the mobile broadband wireless access system have been actively developed by the IEEE (Institute of Electrical and Electronics Engineers) 802.16e and the like.
[4] The conventional wireless LAN scheme provides a data communication scheme in which wireless communication is performed in a local area around a fixed access point. The conventional wireless LAN scheme has a limitation in that it cannot provide mobility to a subscriber terminal, and it supports the local area data communication not in a wired manner but rather in a wireless manner.
[5] On the contrary, the mobile broadband wireless access system guarantees mobility even in a case where the subscriber terminal moves from a cell covered by a current base station to another cell covered by another base station so as to provide a seamless data communication service.
[6] Accordingly, the aforementioned mobile broadband wireless access system mainly uses a battery as a power supply unit of the subscriber terminal. Therefore, in the mobile broadband wireless access system, a short battery usage time of the subscriber terminal is an obstacle to a long-time service.
[7] In order to minimize power consumption of the terminal, the mobile broadband wireless access system supports a sleep mode in which all devices in the terminal stop operating so as to save power when uplink/downlink traffic does not occur.
[8] In addition, in the mobile broadband wireless access system, wireless channels that are set between a terminal and a base station have different qualities of service (QoS) according to traffic characteristics of the wireless channels. Accordingly, in the IEEE 802.16e standard, for efficient management of the sleep mode, a power saving class has been introduced, so that a sleep period is managed according to the power saving class. For example, a wireless channel in which data occurs at an interval of 2 seconds and another wireless channel in which data occurs at an interval of 3 seconds correspond to different power saving classes to have different listening intervals having different periods between sleep modes so as to determine whether or not data occurs.
[9] In the IEEE 802.16e standard, the power saving classes are classified into the below- described three types according to the required QoS. Different schemes of updating a listening period and a sleep period and different operations of receiving data in the listening period are provided to different power saving class types.
[10] Firstly, a power saving class Type I is associated with best effort (BE) traffic having existing Internet traffic characteristic and non-real-time variable rate (nrt-VR) traffic. As parameters that define the power saving class Type I, there are an initial-sleep window, a final-sleep window base, a final-sleep window exponent, a listening window, and a start frame number for the sleep window.
[11] Secondly, a power saving class Type II is associated with voice over Internet protocol (VoIP) or real-time variable rate (rt-VR) traffic having a variable transmission rate. As parameters that define the power saving class Type II, there are an initial-sleep window, a listening window, and a start frame number for the sleep window.
[12] Thirdly, a power saving class Type III is associated with a management message that is to be periodically transmitted to a terminal that is in a sleep mode, such as a downlink channel descriptor/uplink channel descriptor (DCD/UCD) and mobile neighbor base-station advertisement (MOB_NBR-ADV), or data that is to be multicasted. As parameters that define the power saving class Type III, there are a final-sleep window base, a final-sleep window exponent, and a start frame number for the sleep window.
[13] Wireless channels of the subscriber terminal are specified with the corresponding power saving classes. Here, the power saving classes are included in the aforementioned three power saving types.
[14] FIG. 1 is a signal flowchart illustrating a sleep mode management operation performed in a conventional mobile broadband wireless access system.
[15] In order for a subscriber terminal 10 that is operated in an awake mode to enter into a sleep mode, approval of a base station 20 is needed. The subscriber terminal 10 that wants to enter into the sleep mode transmits a sleep mode request message SLP-REQ to the base station 20 to perform a sleep mode request (SlO).
[16] When the sleep mode request is received, the base station 20 transmits a sleep mode response message SLP_RSP to permit the sleep mode of the subscriber terminal 10 (SI l).
[17] When the sleep mode approval is received from the base station 20, the subscriber terminal 10 enters into the sleep mode in which the subscriber terminal 10 does not receive data at the time of entering into the sleep mode (S 12). After an initial sleep mode, the subscriber terminal 10 enters into a listening mode and determines whether or not there is data that is to be transmitted from the base station 20 in the sleep period (S13).
[18] Here, the sleep period is an interval in which the subscriber terminal 10 is operated in the sleep mode, and the listening period is an interval in which the subscriber terminal 10 is operated in a listening mode.
[19] When there is no data that is to be transmitted in the initial sleep period, the base station 20 sets a message that indicates the existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S 14).
[20] The subscriber terminal 10 that determines that there is no transmitted data traffic in the listening mode enters into the sleep mode (S 15). In this case, the sleep period may be the same as or longer than the initial sleep period according to initial setting of the sleep mode.
[21] On the other hand, when there is downlink data that is to be transmitted to the subscriber terminal 10 in a second sleep period, the base station 20 performs buffering on the downlink data (S 17). Existence of the buffered data is notified to the subscriber terminal 10 when the subscriber terminal 10 is operated in the listening mode (S 18).
[22] When the subscriber terminal 10 determines that there is downlink data to be transmitted to the subscriber terminal 10 in the listening mode (S 16), the subscriber terminal 10 terminates the sleep mode and enters into the awake mode to receive the buffered downlink data. Thereafter, the subscriber terminal 10 performs data communication with the base station 20.
[23] Due to the aforementioned sleep mode operation, when there is no downlink data that is to be transmitted to the subscriber terminal, the subscriber terminal can maintain the sleep mode to prevent unnecessary power consumption.
[24] In another sleep mode management method of the mobile broadband wireless access system, when buffered downlink data occurs when the terminal is operated in the sleep mode, it is determined whether or not the buffered downlink data can be completely transmitted within the listening period of the corresponding terminal. When it is determined that transmission can be completed within the listening period, the transmission of the downlink data is finished within the listening period, and the subscriber terminal maintains the sleep mode.
[25] In order to perform the transmission of the downlink data in the listening mode as described above, a specific agreement between the base station and the subscriber terminal is needed. The agreement can be achieved by setting traffic_triggered_wakening_flag of a sleep mode request message SLP-REQ and a sleep mode response message SLP_RSP.
[26] FIG. 2 illustrates a sleep period and a listening period of a power saving class 1 included in the aforementioned power saving class Type I of a subscriber terminal that is operated in a sleep mode, and FIG. 3 illustrates a sleep period and a listening period of a power saving class 2 included in the power saving class Type II of the subscriber terminal that is operated in the sleep mode.
[27] Referring to FIG. 2, in the power saving class 1, the sleep period is increased exponentially with base 2 when the subscriber terminal maintains the sleep mode. In addition, when it is determined that data transmission is needed in the listening mode or that data transmission cannot be completed within the listening period, the power saving class 1 instructs the subscriber terminal to terminate the sleep mode immediately. In the power saving class 1, the sleep period is continuously increased when there is no downlink data. When the sleep period reaches the final-sleep period, the power saving class 1 does not increase the sleep period and maintains the final-sleep period.
[28] The final-sleep period (final-sleep window) can be calculated by using the following
Equation 1, and the final-sleep window base, the final-sleep window exponent, and the like are information included in the sleep mode request message and the sleep mode response message.
[29] [Equation 1] ( /iF~<i •na il-Soileep Window \)=( /iF~<i •na il-Soileep « WΛ ri.nd ,ow - Bi-vase \)x2 (Final-S leep Window Exponent)
[31] Referring to FIG. 3, the power saving class 2 has a listening period and a sleep period that have fixed lengths regardless of data transmission/reception in the listening period.
[32] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. Disclosure of Invention Technical Problem
[33] The downlink data in a data communication system such as the Internet associated with the power saving class Type I has a burst characteristic that indicates that the downlink data occurs in bursts at a predetermined time, or occurs periodically with a relatively long period. Therefore, a case where the base station receives data that is to be transmitted to a downlink from a network in the listening period means that there is no data transmission in a next period or data can occur continuously during a short period. Accordingly, although there is a data in the listening period, terminating the sleep mode is not efficient. [34] In addition, when the subscriber terminal maintains the sleep mode but does not enter into the awake mode even though data occurs in the listening period, as shown in FIG.
2, a next sleep period is increased to be twice the current sleep period. Therefore, when downlink data occurs, there is a problem in that a data transmission delay time may be increased.
Technical Solution [35] The present invention has been made in an effort to provide an efficient sleep mode management method having advantages of maintaining a sleep mode of a terminal in a mobile broadband wireless access system without additional power consumption to increase power saving efficiency of the terminal. [36] The present invention has also been made in an effort to provide an efficient sleep period updating method having advantages of reducing a transmission delay time of downlink data that is transmitted during a sleep mode.
Advantageous Effects
[37] According to the exemplary embodiment of the present invention, in the mobile broadband wireless access system in which downlink traffic that has a burst characteristic that indicates that the downlink traffic occurs in bursts at a predetermined time and has a burst traffic characteristic that indicates that the downlink traffic occurs periodically with a relatively long period, is serviced, the sleep mode management method of decreasing or increasing the sleep period according to whether there is traffic that occurs in the sleep mode has advantages in that the terminal can maintain the sleep mode without additional power consumption and power saving efficiency of the terminal can be increased.
[38] In addition, a transmission delay time of downlink data that is transmitted in the sleep mode can be reduced. Brief Description of the Drawings
[39] FIG. 1 is a flowchart illustrating a sleep mode operation performed in a conventional mobile broadband wireless access system.
[40] FIG. 2 is a flowchart illustrating a sleep period and a listening period in a sleep mode of a power saving class 1 included in a power saving class Type I in a conventional mobile broadband wireless access system.
[41] FIG. 3 is a flowchart illustrating a sleep period and a listening period in a sleep mode of a power saving class 2 included a power saving class Type II in a conventional mobile broadband wireless access system.
[42] FIG. 4 is a flowchart illustrating a sleep period updating method of a power saving class included in a power saving class Type I in a mobile broadband wireless access system according to an embodiment of the present invention.
[43] FIG. 5 is a flowchart illustrating a sleep mode management method in a mobile broadband wireless access system according to an embodiment of the present invention. Best Mode for Carrying Out the Invention
[44] The present invention has been made in an effort to provide an efficient sleep mode management method having advantages of maintaining a sleep mode of a terminal in a mobile broadband wireless access system without additional power consumption to increase power saving efficiency of the terminal.
[45] The present invention has also been made in an effort to provide an efficient sleep period updating method having advantages of reducing a transmission delay time of downlink data that is transmitted during a sleep mode.
[46] An exemplary embodiment of the present invention provides a sleep period management method for a base station in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, including: (a) transmitting downlink data to the terminal in a listening period of the terminal that is operated in a sleep mode; and (b) after terminating the listening period in (a), decreasing a sleep period of the terminal.
[47] Another embodiment of the present invention provides a sleep period management method for a terminal in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, including: (a) receiving downlink data transmitted from a base station in a listening period; and (b) after terminating the listening period in (a), decreasing a sleep period.
[48] In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.
[49] Hereinafter, a sleep period management method in a mobile broadband wireless access system according to embodiments of the present invention is described in detail with reference to the accompanying drawings.
[50] Particularly, what is described is a sleep period management method in a mobile broadband wireless access system in which downlink traffic associated with a power saving class Type I, which has a burst characteristic that indicates that the downlink traffic occurs in bursts at a predetermined time, or occurs periodically with a relatively long period, is serviced.
[51] FIG. 4 is a flowchart illustrating a sleep period updating method in a mobile broadband wireless access system according to an embodiment of the present invention.
[52] Referring to FIG. 4, when there is no downlink data that is to be transmitted to a subscriber terminal, a sleep period is increased exponentially with base 2.
[53] On the other hand, when it is determined that a sleep mode can be maintained even though the downlink data that is to be transmitted to the terminal occurs, a right- after sleep period of the terminal is decreased to be shorter than a right-before sleep period. Here, preferably, the right-after sleep period is decreased by 1/n of the right-before sleep period. The value n is a sleep window decreasing ratio that indicates a decreasing ratio of the sleep period. In addition, the value n may be set to a natural number of 1 or more according to a traffic characteristic of a subscriber terminal. The value n will be described later. The right-before sleep period is a sleep period right before a listening period in which it is determined that downlink data traffic occurs, and the right-after sleep period means a sleep period right after the listening period.
[54] The operation of decreasing the sleep period of the terminal by 1/n is performed only once right after the downlink data traffic occurs, and next sleep periods are increased exponentially with base 2.
[55] The sleep period updating method as described above may be represented by
Equation 2.
[56] [Equation 2]
[57] (Sleep Period)=(Right-Before Sleep Period)x2, (in case of Traffic Notification D=O and (Right-Before Sleep Period)<(Final Sleep Period))
[58] (Sleep Period)=(Right-Before Sleep Period)xl/n, (in case of Traffic Notification D=I and (Right-Before Sleep Period)<(Final Sleep Period))
[59] (Sleep Period)=(Final Sleep Period), (in case of Traffic Notification D=O and
(Right-Before Sleep Period)=(Final Sleep Period))
[60] (Sleep Period)=(Final Sleep Period)xl/n (in case of Traffic Notification D=I and
(Right-Before Sleep Period)=(Final Sleep Period))
[61] A sleep period when a subscriber terminal enters into a sleep mode at first has the same value as the initial-sleep window, and the above equations are applied after the initial sleep period. In addition, the sleep period updating method of decreasing the sleep period right after the downlink data occurs by 1/n as described above can be used when there is prior consent between a base station and a corresponding terminal. To do this, the value n (sleep window decreasing ratio) is included in the sleep mode request message SLP-REQ and transmitted. [62] Accordingly, the value n is shared by the terminal and the base station. Therefore, although the downlink traffic occurs and the terminal updates the sleep period, the base station perceives this and can manage the sleep mode to correspond to the updated sleep period of the terminal.
[63] Hereinafter, by applying the aforementioned sleep period updating method, a sleep mode management method in the mobile broadband wireless access system is described.
[64] FIG. 5 is flowchart illustrating a sleep mode management method in the mobile broadband wireless access system according to an embodiment of the present invention.
[65] Here, when downlink data that is to be transmitted to a subscriber terminal 10 occurs, only a case where the corresponding downlink data can be completely transmitted to the subscriber terminal 10 within a listening period is described, and a description of a case where the downlink data transmission cannot be completed and the subscriber terminal 10 is wakened from the sleep mode is omitted. Since the sleep mode operation in the aforementioned case is well known, it will be understood by a person of an ordinary skill in the art even though a detailed description thereof is omitted.
[66] In order for the subscriber terminal 10 that is operated in an awake mode to enter into a sleep mode, approval of a base station 20 is needed. The subscriber terminal 10 that wants to enter into the sleep mode transmits a sleep mode request message SLP-REQ including the value n (sleep window decreasing ratio) to perform a sleep mode request (S20).
[67] When the sleep mode request is received, the base station 20 transmits a sleep mode response message SLP_RSP to the subscriber terminal 10 to permit the sleep mode (S21).
[68] Negotiation of the value n for managing the sleep period is performed while the sleep mode request (S21) and the sleep mode response (S22) are performed. More specifically, when the base station extracts the value n included in the sleep mode request message SLP-REQ and determines that the value n is a suitable value, the base station adds the same value n to the sleep mode response message SLP_RSP so as to be transmitted. Thereafter, when downlink traffic occurs and the subscriber terminal 10 that receives the downlink traffic updates the sleep period, the value n is used to predict the sleep period of the subscriber terminal 10. On the other hand, when the base station 20 determines that the value n that is included in the sleep mode request message SLP-REQ to efficiently manage the sleep mode is not suitable and wants to use a different value n, the base station 20 may add a value n that is determined to be suitable to the sleep mode response message SLP_RSP to transmit the value n together with the message to the subscriber terminal 10. As described above, when the value n included in the sleep mode request message SLP-REQ is different from the value n included in the sleep mode response message SLP_RSP, the base station 20 and the subscriber terminal 10 use the value n included in the sleep mode response message SLP_RSP to enter into the sleep mode.
[69] When sleep mode approval is received from the base station 20, the subscriber terminal 10 enters into a sleep mode in which the subscriber terminal 10 does not receive data after the time of entering into the sleep mode (S22). After an initial sleep period, the subscriber terminal 10 enters into a listening mode to determine whether or not there is data that is to be transmitted to the subscriber terminal 10 in the sleep period from the base station 20 (S23).
[70] Here, the sleep period is an interval in which the subscriber terminal 10 is operated in the sleep mode, and the listening period means an interval in which the subscriber terminal 10 is operated in the listening mode.
[71] Here, when there is no data that is to be transmitted in the initial sleep mode, the base station 20 sets a message that indicates existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S24).
[72] The subscriber terminal 10 that determines that there is no data traffic transmitted in the listening mode then enters into the sleep mode (S25). Here, the sleep period is increased exponentially with base 2 with respect to the initial sleep period according to initial setting of the sleep mode.
[73] When there is downlink data that is to be transmitted to the subscriber terminal 10 in the second sleep period, the base station 20 may perform buffering on the downlink data (S26). Existence of the buffered data is notified (S28) when the subscriber terminal 10 is operated in the listening mode (S27).
[74] When the subscriber terminal 10 determines that there is the downlink data that is to be transmitted to the subscriber terminal 10 in the listening mode (S27), the subscriber terminal 10 receives the downlink data in the listening mode, decreases the sleep period, and enters into the sleep mode (S29). Here, the subscriber terminal 10 decreases the sleep mode by 1/n according to the aforementioned sleep period updating method. In this case, the base station 10 predicts the updated sleep period to correspond to the value n transmitted through the sleep mode request message and manages next sleep modes according to the updated sleep period.
[75] After maintaining the sleep mode during the sleep period, the subscriber terminal 10 enters into the listening mode (S30), and when there is no downlink data that is to be transmitted to the subscriber terminal 10, the base station 20 sets a message that indicates the existence of data traffic to "0" and transmits the message to the subscriber terminal 10 (S31).
[76] The subscriber terminal 10 that determines that there is no data traffic transmitted in the listening mode enters into the sleep mode (S32). In this case, the sleep period is increased exponentially with base 2 with respect to the right-before sleep period.
[77] Table 1 illustrates an example of the sleep mode request message SLP-REQ according to the embodiment of the present invention. [78] Table 1 [Table 1]
Figure imgf000012_0001
[79] Table 2 illustrates an example of the aforementioned sleep mode response message SLP_RSP according to the embodiment of the present invention. [80] Table 2
[Table 2]
Figure imgf000013_0001
[81] According to Table 1 and Table 2, the sleep window decreasing ratio is a ratio for decreasing the sleep period and is a value corresponding to the aforementioned n (sleep window decreasing ratio) value. The sleep window decreasing ratio is newly introduced according to the embodiment of the present invention. Since the sleep window decreasing ratio is included in the sleep mode request message or the sleep mode response message and is transmitted, the updated sleep period can be shared by the base station and the subscriber terminal.
[82] In addition, by setting the traffic_triggered_wakening_flag illustrated in Table 1 or
Table 2, downlink data can be transmitted while the subscriber terminal is in the listening mode. [83] In the data communication system such as the Internet associated with the power saving class Type I, data traffic has a burst characteristic that indicates that the data traffic occurs in bursts at a predetermined time, or has a traffic characteristic that indicates that the data traffic has a relatively long period or occurs periodically.
[84] Therefore, a case where the base station receives a data that is to be transmitted to the downlink from a network in the listening period means that there is no data transmission in a next period or data can occur continuously during a short period.
[85] Accordingly, the sleep mode management method of decreasing the sleep period right after traffic occurs by 1/n when the downlink data traffic occurs as described above to maintain the sleep mode of a corresponding channel has advantages in that efficient power saving control can be achieved in accordance with a traffic characteristic of the power saving class Type 1 and a transmission delay time of the downlink data can be decreased.
[86] Although the exemplary embodiments and the modified examples of the present invention have been described, the present invention is not limited to the embodiments and examples, but may be modified in various forms without departing from the scope of the appended claims, the detailed description, and the accompanying drawings of the present invention. Therefore, it is natural that such modifications belong to the scope of the present invention.
[87] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

Claims
[1] A sleep period management method for a base station in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, comprising:
(a) transmitting downlink data to the terminal in a listening period of the terminal that is operated in a sleep mode; and
(b) after terminating the listening period in (a), decreasing a sleep period of the terminal.
[2] A sleep period management method for a terminal in a mobile broadband wireless access system in which a sleep mode is supported to save power of a terminal, comprising:
(a) receiving downlink data transmitted from a base station in a listening period; and
(b) after terminating the listening period in (a), decreasing a sleep period.
[3] The sleep period management method of claim 2, wherein in (b), the sleep period is decreased by 1/n, and wherein the n represents a sleep period decreasing ratio and is shared by the base station and the terminal.
[4] The sleep period management method of claim 3, wherein the value n is determined through a sleep mode request message and a sleep mode response message that are transmitted and received between the terminal and the base station before entering into the sleep mode.
[5] The sleep period management method of claim 4, wherein, when a sleep period decreasing ratio included in the sleep mode request message is different from a sleep period decreasing ratio included in the sleep mode response message, the value n is determined by the sleep period decreasing ratio included in the sleep mode response message.
[6] The sleep period management method of claim 3, wherein a traffic characteristic of the downlink data is associated with a power saving class Type 1 among power saving classes that are classified according to quality of service (QoS).
[7] The sleep period management method of claim 3, wherein the power saving class Type I is associated with existing Internet traffic or non-real-time traffic having a variable transmission rate.
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