KR20060040063A - Method of supporting operation of sleep mode in wideband radio acess system - Google Patents

Abstract

The present invention relates to a method for reducing a downlink load transmitted by a base station to a plurality of terminals in a sleep state in a broadband wireless access system. In the broadband wireless access system according to the present invention, a sleep mode operation support method, a broadband wireless access system comprising a base station and at least one terminal in the sleep mode, frame for synchronizing the listening period of the at least one terminal Determining an offset (frame offset); And transmitting the set frame offset information to the at least one or more terminals.

Broadband, Wireless Access, Downlink, Load, Frame Offset

Description

Methods of supporting sleep mode operation in a broadband wireless access system {Method of supporting operation of sleep mode in wideband radio access system}

1 is a flowchart illustrating an operation in a sleep mode state of a terminal in the prior art.

2 is a view for explaining a method for updating a sleep period by one terminal in the sleep mode in the prior art.

3 is a view for explaining a method for updating a sleep period by a plurality of terminals in a sleep mode in the prior art.

Figures 4a and 4b is a view for explaining a comparison with the prior art and the present invention.

5 is a process flow diagram of one preferred embodiment of the present invention.

6 is a process flow diagram of another preferred embodiment of the present invention.

The present invention relates to a wideband radio access system. More specifically, the present invention relates to a method for reducing a downlink load transmitted by a base station to a plurality of terminals in a sleep state in a broadband wireless access system.

The broadband wireless access system supports a sleep mode to minimize power consumption of a mobile subscriber station (MSS). The terminal in the sleep mode operates according to a sleep interval that increases at a constant rate. The sleep interval includes a listening window and a sleep window.

The listening period is fixed through a sleep request message and a sleep response message, and during that period, the UE receives downlink traffic directed to itself through a traffic indication message (MOB-TRF-IND) transmitted from a base station in a broadcasting form. Receive instructions on whether During the sleep period, the terminal receives only a minimum downlink signal from the base station in order to minimize power consumption. During this period, the terminal receives the scanning of the neighboring base stations for handover and maintains uplink communication and signal quality. Ranging for maintaining an appropriate downlink coding type is performed.

The sleep mode operation includes MAC management messages such as a sleep request message (MOB-SLP-REQ), a sleep response message (MOB-SLP-RSP), and a broadcast traffic indication message (MOB-TRF-IND). It is done by exchanging each other.

Table 1 shows an example of a sleep request message delivered to the service base station for a sleep mode request including a sleep period and a listening period.

Syntax Size Notes SLP-REQ_Message_Format () {   Management message type = 50 8 bits   initail-sleep window 6 bits   final-sleep window base 10 bits   listening-window 4 bits   final-sleep window exponent 3 bits   N_sleep_CID 8 bits  Number of Sleep_CID   For (i = 0; i <N_Sleep_CID; i ++ {     Sleep_CID 16 bits   }   reserved 1 bit }

Table 2 shows an example of a sleep response message in which the service base station transmits sleep mode related information such as whether to allow a sleep mode, a sleep period, a listening period, and a sleep ID through a sleep response.

Syntax Size Notes MOB-SLP-RSP_Message_Format () {   Manegement message type = 51 8 bits   Sleep-approved 1 bit 0: Sleep Mode request denied 1: Sleep Mode request approved   If (Sleep-approved = 0) {     REQ-duration 7 bits Time duration   }   else {     If (SHO or FBSS capability enabled) { if SHO or FBSS capability is enabled in the REG-REQ / RSP message exchange       Maintain Active Set and Anchor BS ID 1 bit 1: Active set and Anchor BS ID is maintained while in sleep mode for SHO / FBSS duration 0: Active set and Anchor BS ID is not maintained while in sleep mode       If (Active Set and Anchor BS ID maintained) {         SHO / FBSS duration (5) 3 bits Active set and Anchor BS ID is maintained for 10x2 ^ s frames after entering sleep mode     }   }   Start frame 6 bits   initial-sleep window 6 bits   final-sleep window base 10 bits   listening-window 4 bits   final-sleep window exponent 3 bits   SLPID 10 bits   Sleep duration 8 bits In units of 20ms frames   TLV encoded information  }  Padding Variable To ensure octet-aligned }

Table 3 shows an example of a traffic indication message transmitted in a broadcast form from the base station to the terminal at regular intervals. The terminal in the sleep mode receives the traffic indication message during the listening period, and maintains the sleep mode. Terminate and decide whether to receive downlink data.

Syntax Size Notes MOB_TRF-IND_Message_Format () {  Management message type = 52 8 bits  FMT 1 bit 0 = SLPID based format  if (FMT = 0) { 1 = CID based format    reserved 7 bits    SLPID Group Indication bit-map 32 bits N _th bit of SLPID-Group indication bit-map [MSB corresponds to N = 0] is allocated to SLPID Group that includes MSSs with SLPID values from N * 32 to N * 32 + 31 Meaning of this bit 0: There is no traffic for all the 32 MSSs which belong to the SLPID-Group 1: There is traffic for at least one MSS in SLPID-Group    Traffic Indication Bitmap Variable Traffic Indication bit map comprises the multiples of 32-bit long Traffic Indication unit.                                                  A Traffic Indication unit for 32 SLPIDs is added to MOB_TRF-IND message whenever its SLPID Group is set to '1' 32 bits of Traffic Indication Unit (starting from MSB) are allocated to MSSs in the ascending order of their SLPID values                                                  0: Negative indication 1: Positive indication  } else {    Num-pos 7 bits Number of CIDs on the positive indication list    for (i = 0; i <Num-pos; i ++) {      Short Basic CID 12 bits 12 least significant bits of the Basic CID   }   while (! (byte_boundary)) {     Padding bits <= 7 bits padding for byte alignment    }   }  }

Hereinafter, the operation of the terminal in the sleep mode state will be described.

1 is a flowchart illustrating an operation of a terminal requesting a base station to switch to a sleep mode, maintaining a sleep mode, and ending a sleep mode by generating downlink traffic to the terminal. Each operation is as follows.

The terminal sets a value such as an initial sleep period, a last sleep period, and a listening period in the sleep request message (see Table 1) and transmits the same to the base station to request to switch to the sleep mode [S11].

When the base station allows the terminal to switch to sleep mode, the base station transmits a sleep response message (see Table 2) that sets an initial sleep period, a last sleep period, a listening period, a sleep mode switch start time, and the like [S12] ].

The terminal maintains the sleep mode for the first sleep period when the sleep mode switch start time arrives.

The terminal receives a traffic indication message (see Table 3) from the base station during the listening period when the initial sleep period expires [S13], and sleeps for twice as long as the initial sleep period when there is no downward traffic directed to the terminal. Keep it. A method for checking whether the terminal receives the traffic indication message and whether there is downlink traffic thereof is as follows. The terminal checks the 'SLPID Group Indication bit-map' to check whether there is downlink traffic to be transmitted to the terminals belonging to the SLPID group to which it belongs, and if it is determined, check the 'Traffic Indication Bitmap' to be transmitted to the terminal. Check for downstream traffic.

The sleep period continues to increase through the same method as described above (setting the next sleep period twice as much as the previous sleep period), and when the last sleep period set by the sleep response message is reached, the last sleep period is changed to the next sleep period. Repeat. However, the last sleep period is set as shown in Equation 1 through the parameters in Table 2.

final sleep window = final sleep window base * 2 ^{final window exponent}

If the terminal receives the downlink traffic directed to itself during the listening period through the traffic indication message [S15], the sleep mode is terminated and the downlink traffic is received in the normal mode.

As described above, the terminal maintains a low power state during the initial sleep period after switching to the sleep mode, and when the sleep period expires, receives a traffic indication message from the base station during the listening period, to determine whether there is downlink traffic directed to itself. It is then determined whether to remain in sleep mode or to exit sleep mode. If you need to stay in sleep mode, stay in sleep mode for twice as long as your first sleep period. When the sleep period expires again and the traffic indication message confirms that there is no downward traffic during the listening period, the sleep mode is maintained by setting twice as long a sleep period as the sleep period. This is shown in Figure 2 as shown.

3 illustrates a process in which two or more terminals switch to a sleep mode to update a sleep period. As shown in FIG. 3, when a plurality of terminals switch to the sleep mode, the base station has a problem that the frequency of transmission of the traffic indication message broadcast in the listening period of the terminal increases with the number of terminals that switch to the sleep mode. .

 The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to reduce the number of broadcasts of the traffic indication message delivered to the sleep mode terminal by the base station after the terminal is switched to sleep mode, more efficient The present invention provides a method for supporting sleep mode operation in a broadband wireless access system for performing sleep mode operation.

According to the present invention, by adjusting a sleep period frame offset value of terminals in a sleep mode, a listening window is synchronized between the sleep mode terminals, thereby broadcasting from the base station to the terminals. A method of reducing the number of transmission of a traffic indication message transmitted in a form and allowing a sleep mode operation to be performed more efficiently is disclosed.

In one aspect of the present invention, a method for supporting sleep mode operation in a broadband wireless access system according to the present invention, comprising: a base station and at least one or more terminals in a sleep mode state, comprising: Determining a frame offset for synchronizing the listening period; And transmitting the set frame offset information to the at least one or more terminals.

In another aspect of the present invention, the sleep mode operation supporting method in the broadband wireless access system according to the present invention, in the terminal in the sleep mode state of the broadband wireless access system, frame offset information determined to synchronize the listening period from the base station; Receiving; And receiving a traffic indication message transmitted from the base station in a listening period determined by the set frame offset information.

The construction, operation and other features of the present invention will be readily understood by the preferred embodiments of the present invention described below with reference to the accompanying drawings. 4A and 4B are diagrams for explaining and comparing the prior art and the present invention. FIG. 4A is a diagram for explaining the prior art and FIG. 4B is a diagram for explaining the concept of the present invention.

In the prior art illustrated in FIG. 4A, the terminal having the sleep ID (SLPID) '1' and the terminal having the sleep ID '2' receive the traffic indication message separately from the base station in the listening period in the sleep mode state, respectively. In the present invention shown in FIG. 4B, the terminals receive the traffic indication message separately, and at some point, the terminal adjusts the listening time of the terminal having the SLPID of '2' to listen to the terminal having the SLPID of '1'. By synchronizing with time, the base station broadcasts one traffic indication message to all of the terminals to reduce the downlink load.

Figure 5 shows a procedure flow diagram according to one preferred embodiment of the present invention. Referring to FIG. 5, the terminal MSS transmits a sleep request message (MOB-SLP-REQ) to the base station BS and requests to switch to the sleep mode [S51]. The base station transmits the sleep response message (MOB-SLP-RSP) to the terminal by including an initial sleep period, a sleep mode switch time, a listening period, and a last sleep period [S52].

The terminal gradually increases the sleep period by a sleep window update algorithm if it is not continuously present in the traffic transmitted to it, and the traffic indication message broadcast from the base station during the listening period (MOB-TRF-). IND) to check whether there is downlink traffic destined for itself [S53, S54]. The traffic indication message may have a data structure as shown in Table 3.

When the base station synchronizes the listening period of the terminal with the listening period of at least one or more other terminals in a sleep mode to synchronize transmission of the traffic indication message, the listening period of the terminal and the at least one or more terminals is synchronized. To determine the frame offset (frame offset) to make. As a method of synchronizing the listening periods of a plurality of terminals in the sleep mode, the following two methods may be considered.

First, a frame offset is set at a start point of a listening period of other terminals based on a start point of a listening period of one of the terminals to match a start point of the listening period of the terminals.

Secondly, as in the first method, the frame offset is set at the start of the listening period of the terminal so that the base station can synchronize the start of the listening period of the terminals.

 After determining the frame offset for synchronizing the listening period of all the terminals in the sleep mode state, the base station transmits the determined frame offset information to the terminals.

In the embodiment shown in Fig. 5, the frame offset information is a parameter in the form of a TLV (Type Length Value) as shown in Table 4 below in a traffic indication message (MOB-TRF-IND) broadcast from the base station during a listening period. ) May be included as [S54]. However, the transmission method of the frame offset information is not limited to the method of Table 4.

Name Type Length Value Listening Time Adjust 2 Variable Compound

Table 4 indicates that listening time frame offset information (listening time adujst) of a 'compound' type having a variable length is included.

The base station should transmit an ID for identifying each terminal with the frame offset information to the terminals. A sleep ID (SLPID) and a basic connection ID may be used as the ID. The sleep ID is an ID assigned by the base station to the terminal through a sleep response message when the terminal enters the sleep mode, and the basic connection ID is a unique ID assigned to the terminal.

Table 5 below defines the data format included in the traffic indication message when the sleep ID is used as the ID, and Table 6 defines the data format when the basic connection ID is used as the ID. Tables 5 and 6 may be contemplated as various embodiments of the implementation of the present invention at the choice of those skilled in the art.

Name Type Length (byte) Value SLPID 2.1 2 Unique identifier used in Sleep Mode Next Listening Window Start 2.2 3 Start frame to next listening window

Name Type Length (byte) Value Basic CID 2.3 2 The Basic CID of the MSS Next Listening Window Start 2.2 3 Start frame to next listening window

The terminal checks whether there is downlink traffic transmitted to the user through the traffic indication message transmitted from the base station during the listening period, and if the downlink traffic does not exist, checks whether the frame offset information is included. If the traffic indication message includes the frame offset information, it is checked whether a sleep ID (SLPID) or a basic connection ID (basic CID) corresponding to the traffic offset message is included [S54].

If there is no downlink traffic or its own sleep ID or basic connection ID, the terminal sets a sleep period and a listening period by a sleep period update algorithm, and maintains a sleep mode. If it has its own sleep ID or basic connection ID, it maintains the sleep mode until the next listening period set by the frame offset information, and receives a traffic indication message broadcast from the base station in the next listening period [S55]. . For adjusting the listening period, the sleep period may be set differently from the value applied in the sleep period updating algorithm, and subsequent sleep periods are not updated through the adjusted sleep period, and the unadjusted sleep period, that is, the original sleep period, is updated. Follows the specified value.                     

6 is a process flow diagram of another preferred embodiment according to the present invention. In the embodiment of FIG. 6, the base station transmits a terminal ID, such as the frame offset information and a sleep ID or basic connection ID, to a terminal in a ranging response message.

Referring to FIG. 6, the terminal MSS transmits a sleep request message (MOB-SLP-REQ) to the base station BS and requests to switch to the sleep mode [S61]. The base station transmits the sleep response message (MOB-SLP-RSP) to the user equipment including an initial sleep period, a sleep mode switch time, a listening period, and a last sleep period [S62].

The terminal gradually increases the sleep period by a sleep period update algorithm, receives a traffic indication message (MOB-TRF-IND) during the listening period, checks whether there is downlink traffic directed to the terminal, and enters sleep mode if there is no downlink traffic. Hold [S63, S64].

The terminal transmits a ranging request message (RNG-REQ) to the base station in order to perform periodic ranging for maintaining uplink communication in the sleep mode state. Periodic ranging means adjusting parameters such as timing offset and power for uplink communication in case the UE needs to transmit data to the base station. Ranging should be performed by periodically sending a ranging request message to the base station.

The base station receiving the ranging request message transmits a ranging response message (RNG-RSP) to the terminal in response thereto [S36]. If the base station is to synchronize the transmission of the traffic indication message between the terminal and the other terminal in the sleep mode by adjusting the start time of the listening period of the terminal in the sleep mode state, uplink to the ranging response message In addition to the transmission parameter adjustment values, parameters including frame offset information for each terminal and an ID of the corresponding terminal are included according to the format shown in Tables 4 to 6.

That is, the base station sets and transmits a sleep ID (SLPID) or basic connection ID (Basic CID) of the terminal to change the listening period, and a frame offset value of the start of the listening period. The terminal checks whether the frame offset information is included through the sleep response message transmitted from the base station. When the frame response information is included in the sleep response message, it is checked whether a sleep ID (SLPID) or a basic connection ID (basic CID) corresponding to itself is included.

If there is no downlink traffic and no sleep ID or basic connection ID, the terminal sets a sleep period and a listening period by a sleep period update algorithm, and maintains a sleep mode. If it has its own sleep ID or basic connection ID, it maintains the sleep mode until the next listening period set by the frame offset information, and receives the traffic indication message transmitted from the base station in the next listening period [S67]. . For adjusting the listening period, the sleep period may be set differently from the value applied in the sleep period updating algorithm, and subsequent sleep periods are not updated through the adjusted sleep period, and the unadjusted sleep period, that is, the original sleep period, is updated. Follows the specified value. However, when the present invention is applied, the base station delivers the listening period start time adjustment parameter proposed by the present invention to the terminal only when the sleep terminal reaches the last sleep period in order to perform the sleep period update operation more effectively. The listening time point of the terminal may be synchronized with the listening time point of another sleep terminal.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

According to the sleep mode operation support method in the broadband wireless access system according to the present invention, by synchronizing different listening time between a plurality of terminals in the sleep mode, the base station can reduce the load to be transmitted to the terminals have.

Claims (21)

In a broadband wireless access system, Determining a frame offset for synchronizing a listening window of at least one mobile subscriber station (MSS) in a sleeping mode state; And Sleep mode operation support method in a broadband wireless access system comprising the step of transmitting the set frame offset information to the at least one or more terminals. The method of claim 1, The at least one or more terminals receiving the frame offset information checks whether there is a message transmitted from the base station in a listening period determined by the frame offset information. The method of claim 1, And transmitting a traffic indication message to the at least one or more terminals in a listening period determined by the set frame offset information. The method of claim 1, The frame offset information is included in the traffic indication message and transmitted, characterized in that the sleep mode operation support method in a broadband wireless access system. The method of claim 1, The frame offset information is transmitted in a ranging response message (ranging response message) characterized in that the sleep mode operation support method in a broadband wireless access system. The method according to claim 4 or 5, And the frame offset information is included in the traffic indication message or the ranging response message as a parameter of a type length value (TLV) type. The method according to claim 4 or 5, The traffic indication message is a sleep mode operation support method in a broadband wireless access system, characterized in that it comprises an ID for identifying the at least one or more terminals. The method of claim 7, wherein The ID is a sleep ID (SLPID) sleep mode operation support method in a broadband wireless access system, characterized in that. The method of claim 7, wherein The ID is a basic connection ID (CID), characterized in that the sleep mode operation support method in a broadband wireless access system. In a mobile subscriber station (MSS) in a sleeping mode of a broadband wireless access system, Receiving frame offset information determined for synchronizing a listening window from the base station; And And adjusting a start time of a listening window according to the set frame offset information. The method of claim 10, The frame offset information is included in the traffic indication message and transmitted, characterized in that the sleep mode operation support method in a broadband wireless access system. The method of claim 10, The frame offset information is transmitted in a ranging response message (ranging response message) characterized in that the sleep mode operation support method in a broadband wireless access system. The method according to claim 11 or 12, wherein And the frame offset information is included in the traffic indication message or the ranging response message as a parameter of a type length value (TLV) type. The method according to claim 11 or 12, wherein The traffic indication message is a sleep mode operation support method in a broadband wireless access system, characterized in that it comprises an ID for identifying the terminal. The method of claim 14, The ID is a sleep ID (SLPID) sleep mode operation support method in a broadband wireless access system, characterized in that. The method of claim 14, The ID is a basic connection ID (CID), characterized in that the sleep mode operation support method in a broadband wireless access system. In the broadband wireless access system that supports the sleep mode operation, Transmitting information for allowing sleep mode and sleeping mode operation to a terminal; And Sleep mode operation in a broadband wireless access system comprising transmitting information on the start of listening to indicate the start of the next listening period during the current listening period (listening window) to the terminal operating in the sleep mode according to the information How to apply. The method of claim 17, The information about the start of listening is transmitted in a traffic indication message, sleep mode operation support method in a broadband wireless access system. The method of claim 18, The traffic indication message is sleep mode operation support method in a broadband wireless access system, characterized in that it comprises information identifying the terminal. The method of claim 17, The information about the start of listening is transmitted in a response message to the ranging request, characterized in that the sleep mode operation support method in a broadband wireless access system. The method of claim 20, The response message includes information identifying the terminal, sleep mode operation support method in a broadband wireless access system, characterized in that.

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