WO2017026859A1

WO2017026859A1 - Method for power saving and device using same

Info

Publication number: WO2017026859A1
Application number: PCT/KR2016/008929
Authority: WO
Inventors: 박기원; 김동철; 이병주; 조영준; 임태성
Original assignee: 엘지전자 주식회사
Priority date: 2015-08-12
Filing date: 2016-08-12
Publication date: 2017-02-16

Abstract

A power saving method for a neighbor awareness network (NAN) is provided. A device of an active mode receives a medium access control (MAC) frame. The MAC frame includes a NAN cluster ID indicating a NAN cluster and information on a sleeping period in which the device stays in a sleeping state. If the device is not a member of the NAN cluster indicated by the NAN cluster ID, the device switches to the sleeping state for the sleeping period.

Description

Method for power saving and device using same

The present invention relates to wireless communication, and more particularly, to a method for power saving in a neighbor awareness network (NAN) and a device using the same.

In general, a wireless communication system communicates between devices through a management medium such as a base station or an access point (AP). The management medium is responsible for scheduling for data communication.

In order to secure communication flexibility, various protocols for direct communication between devices without a management medium have been proposed. NAN (Neighbor Awareness Network) is a standard established by the Wi-Fi Alliance (WFA) based on the Wi-Fi standard. The NAN specification provides for synchronization, discovery and data communication procedures between devices in the 2.5 GHz or 5 GHz frequency band.

In device-to-device communication, it is necessary to reduce the power consumption of the device. The NAN specification does not currently support the device's power save mode.

The present invention provides a method for power saving in a neighbor awareness network (NAN) and a device using the same.

In one aspect, a power save method for a neighbor awareness network (NAN) is a device in the active mode receives a medium access control (MAC) frame, the MAC frame is a bed to stay in the sleep state with the NAN cluster ID indicating the NAN cluster The device transitions to the sleep state during the sleep interval, if the device includes information about the interval and the device is not a member of the NAN cluster indicated by the NAN cluster ID.

In another aspect, a device for a neighbor awareness network (NAN) includes a transceiver for transmitting and receiving wireless signals and a processor coupled to the transceiver. The processor receives a medium access control (MAC) frame through the transceiver, wherein the MAC frame includes a NAN cluster ID indicating a NAN cluster and information on a sleep interval to stay in a sleep state, and wherein the device includes the NAN cluster. If it is not a member of the NAN cluster indicated by the ID, it switches to the sleep state during the sleep period.

NAN (Neighbor Awareness Network) can reduce the power consumption of the device.

1 shows an example of a NAN topology.

2 shows a NAN data communication structure.

3 shows an example of a power management operation in an existing WLAN.

4 shows an example of an immediate response in PS mode.

5 shows an example of a delay response in the PS mode.

6 shows an example of the operation of the PS mode by DTIM.

7 illustrates a power save operation according to an embodiment of the present invention.

8 shows a format of a MAC frame according to an embodiment of the present invention.

9 shows a PPDU format according to an embodiment of the present invention.

10 shows a format of a MAC frame according to another embodiment of the present invention.

11 shows a format of a MAC frame according to another embodiment of the present invention.

12 illustrates a power save operation according to an embodiment of the present invention.

13 is a block diagram illustrating a device in which an embodiment of the present invention is implemented.

NAN (Neighbor Awareness Network) is a standard established by the Wi-Fi Alliance (WFA) based on the Wi-Fi standard. NAN devices are devices that support the NAN standard. The NAN device may support various communication protocols and may be part of a station (STA) or part of an access point (AP). The STA may be fixed or mobile, and may include a user equipment (UE), a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a personal digital assistant (PDA), and a wireless modem ( It may be called other terms such as a wireless modem and a handheld device.

NAN devices can operate in the 2.5 GHz or 5 GHz frequency band and can exchange information based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11a / b / g / n / ac protocol.

The NAN device may search for a service of an adjacent device by using the NAN protocol, execute an application, and use the searched service by connecting to a wireless local area network (WLAN) or other network.

1 shows an example of a NAN topology.

The NAN cluster may be a set of NAN devices that share a set of NAN parameters and are synchronized to the same discovery window schedule. NAN devices participating in the same NAN cluster are synchronized to a common clock. The NAN parameter may include at least one of a duration of a discovery window, a discovery window interval, and a NAN channel. The discovery window interval refers to the time interval between successive discovery windows.

The NAN network may include at least one NAN cluster. The NAN device may join one or more NAN clusters.

NAN devices in a NAN cluster may operate in a master role or a non-master role. The NAN device operating in the master role may transmit a synchronization beacon frame and a discovery beacon frame. NAN devices operating in the sync state and non-master roles cannot transmit discovery beacon frames. NAN devices operating in a non-sync state and non-master role cannot transmit sync beacon frames and discovery beacon frames. Every NAN device can transmit a service discovery frame.

The synchronous beacon frame is used for synchronization of NAN devices in a NAN cluster. The discovery beacon frame is used to advertise the cluster to discover NAN devices that are not joined to the NAN cluster. The service discovery frame is used for exchanging information about a service between NAN devices.

2 shows a NAN data communication structure.

NAN Data Cluster (NDC) is a set of NAN Data Links (NDLs) having the same NAN data cluster basic schedule. NDL (NAN Data Link) means a negotiated resource block (RNB) between NAN devices. NAN Data Path (NDP) refers to a data connection established for service between NAN devices.

NDP is set to request service between NAN devices. NAN devices establish an NDL to share a resource (called RB) for data communication. To bang

The NDC includes a plurality of NAN devices sharing a common NDC schedule in the same NAN cluster. Each member device in the NDC has at least one NDL with another member device. Each NDL has its own NDL schedule.

Now, the power save operation in the existing wireless local area network (WLAN) will be described.

Sensing the channel at all times for frame transmission and reception causes a continuous power consumption of the STA. Since the power consumption in the reception state does not differ significantly from the power consumption in the transmission state, maintaining the reception state causes a relatively high power consumption for the battery operated STA. Therefore, in the WLAN system, the STA continuously maintains a reception state and senses a channel, which may cause inefficient power consumption without a special synergistic effect in terms of WLAN throughput, and thus is not suitable for power management. You may not.

In order to compensate for the above problems, the WLAN supports a power management (PM) mode of the STA. The power management mode of the STA is divided into an active mode and a power save (PS) mode. The STA basically operates in the active mode. The STA operating in the active mode maintains an awake state. That is, a state in which normal operation such as frame transmission and reception or channel sensing is possible is maintained.

The STA operating in the PS mode operates by switching between a doze state and an awake state. The STA operating in the sleep state operates at the minimum power and does not receive the radio signal transmitted from the AP including the data frame. In addition, the STA operating in the doze state does not perform channel sensing.

As the STA operates in the sleep state for as long as possible, power consumption decreases, so that the STA increases its operating period. However, since the frame transmission and reception is impossible at bedtime, it cannot operate unconditionally long. When there is a frame to be transmitted to the AP by the STA operating in the sleep state, the STA may switch to the awake state and transmit the frame. However, when the AP has a frame to transmit to the STA operating in the sleep state, the STA cannot receive it and does not know that the frame to receive exists. Accordingly, the STA may need to switch to the awake state according to a specific period in order to receive the presence or absence of a frame to be transmitted to the STA. The AP may thus transmit the frame to the STA. This will be described with reference to FIG. 2.

3 shows an example of a power management operation in an existing WLAN.

The AP 210 transmits a beacon frame to STAs in the BSS at regular intervals (S210). The beacon frame includes a traffic indication map (TIM) element. The TIM element includes information indicating that the AP 210 has buffered traffic for STAs associated with the AP 210 and transmits a frame. The TIM element includes a TIM used to inform unicast frames and a delivery traffic indication map (DTIM) used to inform multicast or broadcast frames. The AP 210 transmits the DTIM one time every three beacon frames.

STA1 221 and STA2 222 are STAs operating in a PS mode. The STA1 221 and the STA2 222 may be configured to receive the TIM element transmitted by the AP 210 by switching from the sleep state to the awake state at every wakeup interval of a specific period.

A specific wakeup interval may be set such that the STA1 221 may switch to the awake state for each beacon interval to receive the TIM element. Therefore, the STA1 221 switches to the awake state when the AP 210 first transmits the beacon frame (S211) (S221). STA1 221 receives the beacon frame and obtains a TIM element. When the acquired TIM element indicates that there is a frame to be transmitted to the STA1 221, the STA1 221 transmits a PS poll frame requesting the AP 210 to transmit the frame to the AP 210 (S221a). The AP 210 transmits the frame to the STA1 221 in response to the PS poll frame (S231). Upon completion of the frame reception, the STA1 221 switches to the sleep state to operate.

When the AP 210 transmits the beacon frame for the second time, the AP 210 does not transmit the beacon frame at the correct beacon interval because the medium is busy, such as another device accessing the medium. It can be transmitted at a delayed time (S212). In this case, the STA1 221 switches the operation mode to the awake state in accordance with the beacon interval, but does not receive the beacon frame transmitted in a delayed state and switches back to the sleep state (S222).

When the AP 210 transmits a beacon frame for the third time, the beacon frame may include a TIM element set to DTIM. However, since the medium is occupied (busy medium) state, the AP 210 delays transmission of the beacon frame (S213). The STA1 221 may operate by switching to an awake state according to the beacon interval, and may obtain a DTIM through a beacon frame transmitted by the AP 210. Since the DTIM acquired by the STA1 221 indicates that there is no frame to be transmitted to the STA1 221 and that there is a frame for another STA, the STA1 221 switches to a sleep state and operates. The AP 210 transmits the frame to the STA after transmitting the beacon frame (S232).

The AP 210 transmits a beacon frame fourthly (S214). However, STA1 221 may not obtain information that there is buffered traffic for itself through the reception of the previous two TIM elements, and thus may adjust the wakeup interval for receiving the TIM elements. Alternatively, when signaling information for adjusting the wakeup interval value of the STA1 221 is included in the beacon frame transmitted by the AP 210, the wakeup interval value of the STA1 221 may be adjusted. In this example, the STA1 221 may be configured to switch the operating state once every three beacon intervals to switch the operating state for TIM element reception every beacon interval. Accordingly, the STA1 221 transmits the fourth beacon frame (S214) at the time when the AP 210 transmits the fifth beacon frame (S215) and maintains the doze state (doze state), so as to acquire the corresponding TIM element. Can't.

When the AP 210 transmits the beacon frame for the sixth time (S216), the STA1 221 operates by switching to an awake state and acquires a TIM element included in the beacon frame (S224). Since the TIM element is a DTIM indicating that a broadcast frame exists, the STA1 221 receives a broadcast frame transmitted by the AP 210 without transmitting a PS poll frame to the AP 210 (S234). .

Meanwhile, the wakeup state set in the STA2 222 may be set in a longer period than the STA1 221. Accordingly, the STA2 222 may switch to the awake state and receive the TIM element at the time S215 when the AP 210 transmits the beacon frame for the fifth time (S224). The STA2 222 knows that there is a frame to be transmitted to itself through the TIM element and transmits a PS poll frame to the AP 210 to request transmission (S224a). The AP 210 transmits the frame to the STA2 222 in response to the PS poll frame (S233).

4 shows an example of an immediate response in PS mode.

The STA 320 transitions from the sleep state to the awake state in order to receive the beacon frame including the TIM from the AP 310 (S310). The STA 320 may interpret the received TIM element to know that there is buffered traffic to be transmitted to it.

The STA 320 contends with other STAs to access a medium for PS poll frame transmission (S320), and transmits a PS poll frame to request the AP 310 to transmit a data frame (S330). ).

The AP 310 that receives the PS poll frame transmitted by the STA 320 transmits the frame to the STA 320. The STA2 320 receives the data frame and transmits an acknowledgment (ACK) frame to the AP 310 in response to the reception (S350). After that, the STA2 320 switches to the sleep state again (S360).

This is an immediate response process in which the AP transmits a data frame immediately after receiving the PS poll frame from the STA.

5 shows an example of a delay response in the PS mode.

The STA 420 switches the operation state from the sleep state to the sleep state in order to receive the beacon frame including the TIM from the AP 410 (S410). The STA 420 interprets the received TIM element to know that there is buffered traffic to be transmitted to it.

The STA 420 contends with other STAs to access a medium for transmitting the PS poll frame (S420), and transmits a PS poll frame to request the AP 410 to transmit a data frame (S430).

If the AP 410 fails to prepare a data frame during SIFS (short interframe space) even after receiving the PS poll frame, the AP 410 does not transmit the data frame directly but instead transmits the ACK frame to the STA 420 (S440). ).

When the data frame is ready after the ACK frame is transmitted, the AP 410 performs contention (S450) and transmits the data frame to the STA 420 (S460).

The STA 420 transmits an ACK frame to the AP 410 in response to the reception of the data frame (S470), and switches to a sleep state (S480).

This is called a deferred response in that the AP sends an ACK frame first in response to the PS poll frame and then transmits a data frame.

6 shows an example of the operation of the PS mode by DTIM.

The STAs 520 switch the operational state from the sleep state to the awake state in order to receive the beacon frame including the TIM element from the AP 510 (S510). The STAs 520 may know that a multicast / broadcast frame will be transmitted through the received DTIM.

The AP 520 transmits a multicast / broadcast frame after transmitting the beacon frame including the DTIM (S520). The STAs 520 switch back to the sleep state after receiving the multicast / broadcast frame transmitted by the AP 510 (S530).

The STAs may check whether there is a data frame to be transmitted due to the buffered traffic through the STA identification information included in the TIM element. The STA identification information is associated with a 14-bit association identifier (AID) that is an identifier assigned when the STA associates with the AP.

We now describe the power save mode for the proposed NAN device.

In the conventional WLAN, the STA periodically switches between the sleep state and the awake state in the power save mode. However, the NAN device does not operate data transmission by the AP and does not need to be in an awake state or an active mode for receiving a beacon frame unless the channel is occupied by the AP.

In step S710, the NAN device receives a medium access control (MAC) frame or a physical layer protocol data unit (PPDU).

In operation S720, the NAN device determines whether to switch from the active mode to the sleep state based on the MAC frame or the PPDU.

In operation S730, when the switching condition is satisfied, the NAN device switches to the sleeping state during the sleeping period. The sleep interval may be designated by a duration field of a MAC frame to be described later or an L-SIG of a PPDU. When the sleep period elapses, the NAN device may switch back to the awake state.

The field name, field order, and number of bits are only examples below. Not all fields are required, some fields may be omitted or other fields may be added.

The Frame Control field of the MAC header contains a condition for switching to the proposed sleep state. The Duration field of the MAC header indicates the sleep period to stay in the sleep state when switching to the sleep state.

The Frame Control field includes a ToDS field, a FromDS field, a connection type field, and an NDC ID.

The meaning of the combination of the ToDS field and the FromDS field is as follows.

	의미meaning
To DS = 0From DS = 0To DS = 0	이 MAC 프레임이 동일한 BSS(basic service set)내의 타 STA으로 전달됨.This MAC frame is delivered to another STA in the same basic service set (BSS).
To DS = 1From DS = 0To DS = 1	이 MAC 프레임이 DS(distribution system)으로 향함.This MAC frame is directed to the distribution system (DS).
To DS = 0From DS = 1To DS = 0 From DS = 1	이 MAC 프레임이 DS(distribution system)에서 나감.This MAC frame exits the distribution system (DS).
To DS = 1From DS = 1To DS = 1	메쉬 BSS에서만 사용.Only used for mesh BSS.

The connection type indicates whether or not this MAC frame is for a NAN connection.

The NDC ID identifies the NDC to which this MAC frame belongs.

When the NAN device satisfies any one of the following five conditions from the received MAC frame, it may transition to the sleep state.

(1) fromDS = 0 and toDS = 1

(2) fromDS = 1 and toDS = 0

(3) fromDS = 1 and toDS = 1

(4) fromDS = 0 and toDS = 0 and connection type is not NAN.

(5) The NDC ID in the MAC frame is inconsistent with the NDC ID in which it participates.

The NAN device may switch to the sleep state for a period specified in the Duration field if the received MAC frame is not its own, is not the NDC to which it belongs, or is not a NAN connection.

9 shows a PPDU format according to an embodiment of the present invention.

The PPDU may include a legacy short training field (L-STF), a legacy long training field (L-LTF), a legacy signal field (L-SIG), a signal field (SIG), an STF, an LTF, and a data field.

L-STF can be used for automatic gain control (AGC) and coarse carrier frequency offset correction. L-LTF can be used for fine carrier frequency offset correction and symbol synchronization.

The L-SIG field may indicate the length of the PPDU or may specify a sleep interval in which the NAN device stays in the sleep state.

The SIG field may include control information necessary for demodulating the received PPDU by the device receiving the PPDU. The SIG field may include a ToDS field, a FromDS field, a connection type field, and an NDC ID for determining entry into a sleep state.

STF is used to increase the gain control performance of the AGC. LTF can be used for MIMO channel estimation. The data field includes data information to be transmitted.

The NAN device receives up to the SIG field and determines whether the condition of one of the above (1) and (5) is satisfied. If only one condition is satisfied, the user can switch to the sleep state during the designated period. Upon entering the sleep state, fields subsequent to the SIG field in the PPDU need not be received. When the designated interval elapses, the NAN device may return to the awake state.

The MAC header may include a group ID and a reception address. The group ID indicates a NAN data communication group. The reception address represents one of the unicast address, the multicast address, and the broadcast address of the device (s) to receive the corresponding MAC frame.

When the NAN device receiving the MAC frame is not a member of the NAN data communication group of the group ID or the receiving address is not the address to which the NAN device belongs, the NAN device may enter a sleep state for a specified period.

In another embodiment, the SIG field of the PPDU may include a group ID and a reception address. The NAN device that receives the PPDU may enter a sleep state for a designated period when the NAN device is not a member of the NAN data communication group of the group ID or the receiving address is not the address to which the NDU belongs.

The MAC header may include at least one of a NAN cluster ID, an NDC ID, an NDL ID, and a reception address. The NAN cluster ID indicates a NAN cluster to which a device to receive a MAC frame belongs. The NDC ID indicates an NDC to which a device to receive a MAC frame belongs. The NDL ID indicates an NDL to which a device to receive a MAC frame belongs. The reception address represents one of the unicast address, the multicast address, and the broadcast address of the device (s) to receive the corresponding MAC frame.

When the NAN device satisfies any one of the following conditions, the NAN device may switch to the sleep state for a specified period.

(1) The NAN cluster ID in the MAC frame does not match its own NAN cluster ID.

(2) The NDC ID in the MAC frame does not match its own NDC ID.

(2) The NDL ID in the MAC frame is inconsistent with its NDL ID.

(4) The receiving address in the MAC frame is not the address to which it belongs.

For example, even if the NAN cluster ID in the MAC frame matches the NAN cluster ID of the MAC frame, the NAN device may switch to a sleep state for a period specified in the Duration field if the NDC ID in the MAC frame does not match the NDC ID of the NAN device. . When the specified section has elapsed, it may return to the awake state.

In another embodiment, the SIG field of the PPDU may include at least one of a NAN cluster ID, an NDC ID, an NDL ID, and a reception address. Upon receiving the PPDU, the NAN device may enter a sleep state for a specified period when one of the conditions (1) to (4) is satisfied.

When the NAN device receives another frame and sets a network allocation vector (NAV) to a non-zero value while performing a clear channel assessment (CCA) to transmit its data frame in active mode, the NAN device currently It is possible to suspend the backoff process for transmitting the data frame to be transmitted and to go to sleep. Stay in sleep for the value set by the NAV. When the value set by the NAV expires, it can return to the awake state and restart the interrupted backoff process.

The NAN device 1 checks the NDC ID in the PPDU and checks whether the NAN device 1 is a member of the NDC identified by the NDC ID. If confirmed as a member, the NAN device 1 receives its data in the data field.

The NAN device 2 checks the NDC ID in the PPDU and checks whether the NAN device 2 is a member of the NDC identified by the NDC ID. If it is confirmed that the member is not, NAN device 2 can immediately go to sleep without decoding the data field.

The device 100 may perform an operation of the NAN device according to the proposed embodiment. The device 100 includes a processor 110, a memory 120, and a transceiver 130. The memory 120 is connected to the processor 110 to store various instructions executed by the processor 110. The transceiver 130 is connected to the processor 110 to transmit and / or receive a radio signal. The processor 110 implements the proposed functions, processes and / or methods. In the above-described embodiment, the processor 110 implements the NAN protocol, and the discovery process and the data communication process may be implemented by the processor 110. When the above-described embodiments are implemented as software instructions, the instructions may be stored in the memory 120 and executed by the processor 110 to perform the above-described operations.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

Claims

In the power save method for NAN (Neighbor Awareness Network),

The device in the active mode receives a medium access control (MAC) frame, the MAC frame including a NAN cluster ID indicating a NAN cluster and information on a sleep interval to stay in a sleep state;

If the device is not a member of the NAN cluster indicated by the NAN cluster ID, the device transitions to a sleep state during the sleep period.
The method of claim 1,

The MAC frame further includes information about a NAN data cluster ID indicating a NAN data cluster;

The method is

If the device is not a member of the NAN data cluster indicated by the NAN data cluster ID, the device further comprises switching to the sleep state during the sleep period.
The method of claim 1,

The MAC frame further includes information about a NAN data link ID indicating a NAN data link;

The method is

If the NAN data link ID of the device does not match the NAN data link ID, the device further comprises switching to the sleep state during the sleep period.
The method of claim 1,

The MAC frame further includes information about a reception address indicating a recipient of the MAC frame;

The method is

If the device is not the recipient indicated by the receiving address, the device further comprising switching to the sleep state during the sleep period.
The method of claim 1,

And when the sleep interval expires, returning the device to the active mode.
In the device for the NAN (Neighbor Awareness Network),

A transceiver for transmitting and receiving wireless signals; and

A processor coupled to the transceiver, wherein the processor includes:

Receiving a medium access control (MAC) frame through the transceiver, wherein the MAC frame includes a NAN cluster ID indicating a NAN cluster and information on a sleep interval to stay in a sleep state;

And if the device is not a member of the NAN cluster indicated by the NAN cluster ID, switch to a sleep state during the sleep period.
The method of claim 6,

The MAC frame further includes information about a NAN data cluster ID indicating a NAN data cluster;

The processor is

And if the device is not a member of the NAN data cluster indicated by the NAN data cluster ID, switch to the sleep state during the sleep period.
The method of claim 6,

The MAC frame further includes information about a NAN data link ID indicating a NAN data link;

The processor is

And if the NAN data link ID of the device does not match the NAN data link ID, switch to the sleep state during the sleep period.
The method of claim 6,

The MAC frame further includes information about a reception address indicating a recipient of the MAC frame;

The processor is

And if the device is not the receiver indicated by the receiving address, switch to the sleep state during the sleep period.