# Patent

## Title
Discovery-phase power conservation

## Abstract

The present specification describes techniques and apparatuses that enable power conservation in a wireless network. In some cases these techniques and apparatuses enable power conservation during a discovery phase and for a wireless network subject to a government mandate requiring a device of the network to passively search for radar transmission prior to establishing communication with another device of the network.

## Background
RELATED APPLICATION
This application is a continuation of and claims priority to U.S. patent application Ser. No. 12/646,802 filed Dec. 23, 2009 entitled DISCOVERY-PHASE POWER CONSERVATION, which claims priority to U.S. Provisional Patent Application Ser. No. 61/141,724 filed Dec. 31, 2008, the disclosure of which is incorporated by reference herein in its entirety.


BACKGROUND
Wireless local area networks (WLANs) often communicate at frequencies subject to government regulations. In the United States for example, some frequencies in the five Giga-Hertz (GHz) band are restricted because the United States' military uses these frequencies for radar. These restrictions require client stations of a WLAN to passively scan for radar at the desired frequency for a mandated period of time. If a client station does not find radar at the desired frequency during that period of time, the client station may then communicate at that frequency as part of the WLAN. During this mandated period of time, access points of WLANs often expend significant amounts of power attempting to establish communications with client stations.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
SUMMARY
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description.
A system-on-chip (SoC) is described that implements a power conserver for conserving power during a discover phase of a wireless local area network (WLAN). The SoC conserves power by reducing power at an access point of a (WLAN) for a reduced-power-usage period, the access point operating in a geographical region and at a frequency in which client stations operating in the geographical region and at the frequency are required to passively search for radar transmissions prior to transmitting at the frequency. During the reduced-power-usage period, the power at the access point is insufficient to enable the access point to receive communication from a client station within a communication region of the access point. The reduced-power-usage period at the access point can vary according to information received by the access point from one of the client stations indicating a radar search period for the client station. Following this reduced-power-usage period, the SoC increases the power at the access point for a reception period in which communication from a client station within a communication region of the access point can be received.
Another SoC embodiment is described that implements a power conserver for conserving power during a discover phase of a WLAN by transmitting, from an access point of the WLAN, a first beacon, the first beacon to discover a client station with which to establish communication, maintaining power usage at the access point for a first reception period, the power usage sufficient to enable receiving a probe request from the client station, responsive to not receiving the probe request from the client station during the first reception period and prior to establishing communication with the client station, reducing power usage at the access point after the first reception period ends and for a reduced-power-usage period, the reduced-powered-usage period insufficient to enable receiving the probe request from the client station. The SoC can also vary the reduced-power-usage period at the access point according to information received by the access point from the client station indicating a radar search period for the client station.
This embodiment of the SoC continues the power conservation by transmitting, from the access point, a second beacon, the second beacon to discover the client station, and maintaining power usage at the access point for a second reception period, the power usage sufficient to enable receiving the probe request from the client station. Then, responsive to receiving the probe request from the client station during the second reception period, responding to the probe request with a probe response, the probe response part of establishing communication with client station.
In another embodiment, a wireless communication device, including a wireless transmitter, a wireless receiver, and a power conserver, is described. The power conserver enables the wireless communication device to conserve power during operation by causing a wireless transmitter to transmit a first beacon, the first beacon to discover a client station with which to establish communication, and maintaining power usage at the wireless communication device for a first reception period, the power usage sufficient to enable receiving a probe request from the client station. Responsive to a wireless receiver not receiving the probe request from the client station during the first reception period and prior to establishing communication with the client station, the power conserver continues by reducing power usage at the wireless communication device after the first reception period ends and for a reduced-power-usage period, the reduced-powered-usage period insufficient to enable receiving the probe request from the client station. The power conserver can also vary the reduced-power-usage period at the wireless communication device according to information received by the wireless communication device from the client station indicating a radar search period for the client station.
This embodiment of the power conserver continues the power conservation by causing the wireless transmitter to transmit a second beacon, the second beacon to discover the client station, and maintaining power usage at the wireless communication device for a second reception period, the power usage sufficient to enable receiving the probe request from the client station. Then, responsive to the wireless receiver receiving the probe request from the client station during the second reception period, causing the wireless transmitter to respond to the probe request with a probe response, the probe response part of establishing communication with client station.



BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different instances in the description and the figures indicate similar or identical items.
FIG. 1 illustrates an example operating environment having wireless-communication-capable devices.
FIG. 2 illustrates a method for conserving power during a discovery phase of a wireless network.
FIG. 3 illustrates a WLAN having an access point, a client station, and a communication region.
FIG. 4 illustrates an example timeline for establishing communications between devices of a WLAN when subject to a government-mandated passive-reception period.
FIG. 5 illustrates a method performed by an access point of a WLAN to conserve power during a discovery phase of the WLAN.
FIG. 6 illustrates an example System-on-Chip (SoC) environment for implementing embodiments of the techniques described herein.



DETAILED DESCRIPTION
Conventional techniques for establishing communications in a wireless network often use significant amounts of power. This disclosure describes techniques and apparatuses for conserving this power.
In the discussion that follows, an example operating environment is described. Example methods are also described that may be employed in the example operating environment as well as other environments. These methods are followed by an example System-on-Chip (SoC) embodiment in which components of FIG. 1 may be embodied. In the discussion below, reference is made to the environment by way of example only and, therefore, implementations described below are not limited to the example environment.
Example Operating Environment
FIG. 1 illustrates an example operating environment 100 having wireless-communication-capable devices 102, all of which are capable of transmitting and receiving wireless communications, such as those of a wireless local area network (WLAN). Devices 102 are shown to include a printing device 104, a dedicated WLAN access point 106, a set-top box 108, and personal computing devices including a cellular phone 110, a desktop computing device 112, and a laptop computing device 114. Any of these devices may act as a WLAN access point or a client station of the WLAN except dedicated WLAN access point 106, which is configured to act only as an access point of the WLAN.
In this example environment, each of devices 102 includes a wireless transmitter 116, a wireless receiver 118, and a power conserver 120. Transmitter 116 is capable of transmitting a wireless communication signal according to one or more communication protocols, such as those for a WLAN. This protocol may include, by way of example only, those of the IEEE 802.11 family of protocols.
Receiver 118 is capable of receiving a wireless communication signal according to one or more communication protocols, such as those noted for transmitter 116. Transmitter 116 and receiver 118 may be separate components (as shown in FIG. 1) or be combined (in which case the combination may be referred to as a transceiver). Also, transmitter 116 and receiver 118 may be implemented in hardware in combination with (or separate from) software. Transmitter 116 and receiver 118 are capable of establishing communications during a discovery phase, such by using handshake protocols, after which devices 102 may establish post-discovery, ongoing communications.
Power conserver 120 is capable of enabling a wireless device acting as an access point of a wireless network (e.g., WLAN) to conserve power. In one implementation, power conserver 120 does so by reducing an access point's power consumption during a period in which client stations may otherwise be unable to establish communications with the access point.
In some cases client stations are unable to establish communications during a period in which the client stations are required to passively scan for radar. Government restrictions depend on the geographical region and frequency at which communications in the wireless network are desired; geographical regions are subject to different governments and thus government regulations, such those of the Federal Communications Commission (FCC) of the U.S. government, or those of various governments of the European Union, Japan, China, Canada, and Australia, to name a few. The FCC currently requires a passive radar scan of 60 seconds at various frequencies in the five GHz band.
In one implementation, power conserver 120 includes a set of computer-executable instructions stored on computer-readable media 122. When executed by one or more processors 124, device 102 acts according to those instructions. Power conserver 120 may act independently or in conjunction with various other entities, such as transmitter 116 and receiver 118. Power conserver 120 may be separate from on integral with other entities of one of devices 102 as well, such as by being firmware integrated into a System-on-Chip (SoC) having transmitter 116 and receiver 118.
Example Power-Conservation Techniques
The following discussion describes techniques that may be implemented utilizing the previously described environment. Aspects of these techniques may be implemented in hardware, firmware, software, or a combination thereof. These techniques include methods illustrated in FIGS. 2 and 5, each of which is shown as a set of blocks that specify operations performed by one or more entities. These methods are not necessarily limited to the orders shown for performing the operations by the respective blocks.
FIG. 2 depicts a method 200 for conserving power during a discovery phase of a wireless network, including operations performed by an access point (shown at arrow 202) and a client station (shown at arrow 204), both separated by a vertical dashed line. The operations of the access point and client station are shown side-by-side to illustrate possible interrelations, though the access point and client station may operate independently.
At 206, an access point of a wireless local area network (WLAN) reduces power for a reduced-power-usage period. In one implementation, the access point reduces power while the access point is attempting to establish communications with client stations. Here client stations, in at least some cases, are not able to respond or otherwise actively communicate with the access point.
By way of example, consider FIGS. 3 and 4. FIG. 3 illustrates devices of a WLAN. FIG. 4 illustrates an example timeline 400 for establishing communications between devices of a WLAN when subject to a government-mandated passive-reception period 402 (mandated period 402).
In more detail, FIG. 3 illustrates printing device 104 acting as an access point 302, and laptop computing device 114 acting as a client station 304. Access point 302 and client station 304 are attempting, as part of a discovery phase, to find and establish communications. A communication region 306 represents a region in which access point 302 may communicate with client stations (here the region includes client station 304, though in some cases more or no client stations may reside in this region). Note that these two devices are examples of devices 102 of FIG. 1 and that both may include the elements shown for device 102 (e.g., power conserver 120). This example illustrates an ad-hoc WLAN structure, the structure having device-to-device communications rather than a dedicated access point-to-device structure, though either structure may be used.
Access point 302 is operating in a geographical region and at a frequency in which a government-mandated passive-reception period (illustrated in FIG. 4 as mandated period 402) requires client stations 304 that are operating in the geographical region and at the frequency to passively search for radar transmissions prior to transmitting at the frequency. Thus, for at least this mandated period 402, power consumption by access point 302 may be reduced or eliminated without necessarily causing significant delay in establishing communication with client station 304. As noted in operation 206, power may be conserved for a particular reduced-power-usage period. An example reduced-power-usage period is shown at 404 in FIG. 4. This power conservation may render access point 302 incapable of receiving communication from client station 304.
At 208, the access point actively attempts to establish communications with a client station. This attempt can include transmitting a beacon, which may or may not indicate a reception period described at 210. Continuing the ongoing example, access point 302 transmits beacon 406-1 of beacons 406, illustrated in FIG. 4. Beacon 406-1 is not responded to by client station 304 because client station 304 may not respond during mandated period 402.
At 210, subsequent to the reduced-powered-usage period, power is increased at the access point for a reception period, the reception period enabling reception of communication, such as from a client station. Here access point 302 increases power sufficient for its receiver 118 to receive a communication from transmitter 116 of client station 304 for reception period 408-1. Client station 304 later communicates a probe request 410, though (in one implementation) not during reception period 408-1.
Operations 206, 208, and 210 can be performed until a client station replies to the access point's attempt to establish communications. Thus, if no communication is received at 210, the access point may return to operation 206 (shown with a dashed line proceeding from 210 to 206). An example of this repetition is illustrated in FIG. 4, in which multiple reduced-power-usage periods 404 (404-1, 404-2, and 404-3) and reception periods 408 (408-1, 408-2, and 408-3) reside within mandated period 402. While these operations 206, 208, and 210 may repeat, period 406 and/or 408 are not necessarily identical.
While the example provided includes a government-mandated period, these techniques can conserve power during other times, such as times in which client stations are either unable, required to refrain from, or are not present to establish communications with an access point of the WLAN.
Having described operations of a device acting as or being a dedicated access point, the discussion turns to those of a client station, namely those shown at arrow 204 of FIG. 2. At 212, a client station determines whether a frequency contains radar transmissions. Client station 304 may do so following one or even many reduced-power-usage periods 404 and during mandated period 402. If radar is found at the frequency (shown at “Found” in FIG. 2), the client station returns to 212, which the client station may repeat at the same or a different frequency. If radar is not found (shown at “Not Found”), the client station proceeds to 214.
At 214, the client station receives an attempt to establish communication. Continuing the ongoing example of FIGS. 3 and 4, client station 304 receives beacon 406-4. Note that mandated period 402 is complete.
At 216, the client station replies to the attempt to establish communication during the reception period. As noted, this reception period may be indicated (e.g., advertised and included in beacons 406) or not indicated. If not indicated, the client station may have received the reception period previously, the reception period may be standardized, or the client station may simply respond within the reception period without any knowledge of the reception period.
At 218, the access point communicates according to a handshake protocol to continue to establish ongoing communications with the client station. In the ongoing example, operation 218 is preceded at 216 with client station 304 replying with probe request 410 during reception period 408-4 after determining that no radar transmission is found. Following this reply, at 218 access point 302 transmits probe response 412 to establish communications shown at 414. These or further communications may complete a handshake protocol to establish ongoing communications (e.g., those standard to IEEE 802.11 discovery-phase WLAN protocols).
FIG. 5 depicts a method 500 for conserving power during a discovery phase of a wireless network. This method parallels operations illustrated at arrow 202 in FIG. 2, though with greater specificity concerning some operations, greater generality in other operations, and additional operations not shown at arrow 202.
At 502, an access point of a wireless local area network (WLAN) transmits a beacon, the beacon to discover a client station with which to establish communication. FIG. 4 illustrates example beacons at 406.
At 504, the access point maintains power usage at the access point for a first reception period, the power usage sufficient to enable reception of a probe request from the client station. Examples of this first reception period are shown at any of reception periods 408-1, 408-2, or 408-3 of FIG. 4.
At 506, the access point, responsive to not receiving the probe request from the client station during the first reception period, reduces power usage at the access point after the first reception period ends and for a reduced-power-usage period, the reduced-powered-usage period insufficient to enable receiving the probe request from the client station. Examples of this are illustrated at any of periods 404-1, 404-2, or 404-3 of FIG. 4.
At 508, the access point transmits a second beacon, the second beacon to discover the client station (or another client station) with which to establish communication. FIG. 4 illustrates example beacons at 406, though in this case the second beacon is assumed to be one to which a reply is made, though there may be intervening repetitions of operations 502, 504, 506, and 508 prior to a reply being received.
At 510, the access point maintains power usage at the access point for a second reception period, the power usage sufficient to enable reception of a probe request from the client station. An example of this second reception period is shown at 408-4 of FIG. 4.
At 512, the access point, responsive to receiving a probe request from a client station, responds with a probe response to establish ongoing communications. An example of this probe request is shown at 410, an example of this probe response is shown at 412, and an example of this communication established is shown at 414, all of FIG. 4.
In some cases the first beacon indicates a first amount of time that the access point is capable of receiving a probe request from the client station. The second may also or instead indicate a second amount of time that the access point will be capable of receiving a probe request from the client station, though these times are not necessarily identical. These times may be different based on various factors, including a history of how quickly client stations reply. If replies have historically been made more quickly than the reception period, the access point may reduce the reception period to conserver more power.
Similarly, reduced-power-usage periods may be altered or vary. If, for example, the access point is rarely communicated with, such as the access point being a printing device that is only used for occasional printing tasks, the access point may record this history and extend its reduced-power-usage period to further conserve power. When subject to government mandates (e.g., to search for radar), the access point may receive information indicating that a mandated period for client stations has been changed. Based on this information the access point may alter any of its reception and/or reduced-power-usage periods.
System-on-Chip Example
FIG. 6 illustrates an example System-on-Chip (SoC) 600, which can implement various embodiments described above. An SoC can be implemented in a fixed or mobile device, such as one or a combination of a media device, computer device, television set-top box, video processing and/or rendering device, appliance device, gaming device, electronic device, vehicle, workstation, WLAN access point or client station, and/or in any other type of device that may communicate wirelessly in a local or personal area network. Examples of some of these are shown in FIG. 1 at 102.
SoC 600 can be integrated with electronic circuitry, a microprocessor, memory, input-output (I/O) logic control, communication interfaces and components, other hardware, firmware, and/or software needed to run an entire device. SoC 600 can also include an integrated data bus (not shown) that couples the various components of the SoC for data communication between the components. A device that includes SoC 600 can also be implemented with many combinations of differing components.
In this example, SoC 600 includes various components such as an input-output (I/O) logic control 602 (e.g., to include electronic circuitry) and a microprocessor 604 (e.g., any of a microcontroller or digital signal processor). SoC 600 also includes a memory 606, which can be any type of random access memory (RAM), a low-latency nonvolatile memory (e.g., flash memory), read only memory (ROM), and/or other suitable electronic data storage. SoC 600 can also include various firmware and/or software, such as an operating system 608, which can be computer-executable instructions maintained by memory 606 and executed by microprocessor 604. SoC 600 can also include other various communication interfaces and components, wireless LAN (WLAN) or PAN (WPAN) components, other hardware, firmware, and/or software.
SoC 600 may include wireless transmitter 116, wireless receiver 118, and power conserver 120 (in either or multiple devices as noted above). Examples of these various components, functions, and/or entities, and their corresponding functionality, are described with reference to the respective components of the example environment 100 shown in FIG. 1.
Power conserver 120 in SoC 600, either independently or in combination with other entities, can be implemented as computer-executable instructions maintained by memory 606 and executed by microprocessor 604 to implement various embodiments and/or features described herein. Power conserver 120 may also be provided integral with other entities of the SoC, such as integrated with one or both of wireless transmitter 116 and wireless receiver 118. Alternatively or additionally, power conserver 120 and the other components can be implemented as hardware, firmware, fixed logic circuitry, or any combination thereof that is implemented in connection with the I/O logic control 602 and/or other signal processing and control circuits of SoC 600.
Although the subject matter has been described in language specific to structural features and/or methodological operations, the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including orders in which they are performed.

## Claims

1. A System-on-Chip (SoC) comprising:
a processor; and
a computer-readable storage memory device embodying computer-executable instructions, that, when executed by the processor, implement a power conserver configured to conserve power during a discovery phase of a wireless local area network (WLAN) by:
reducing power at an access point of the WLAN for a reduced-power-usage period, the access point operating in a geographical region and at a frequency in which client stations operating in the geographical region and at the frequency are required to passively search for radar transmissions prior to transmitting at the frequency, the reduced power being insufficient to enable the access point to receive communication from a client station within a communication region of the access point, the reduced-power-usage period at the access point being configured to vary according to information received by the access point from one of the client stations indicating a radar search period for the client station; and
increasing power at the access point subsequent to expiration of the reduced-power-usage period, the power being increased for a reception period in which communication from the client station or another client station within the communication region of the access point can be received.

2. The SoC of claim 1, wherein the client stations are required to passively search for radar transmissions for the radar search period prior to transmitting at the frequency.

3. The SoC of claim 2, wherein the radar search period is sixty seconds and the frequency is in a five Giga-Hertz band.

4. The SoC of claim 2, wherein reducing power and increasing power are performed multiple times during the radar search period.

5. The SoC of claim 1, further comprising, subsequent to expiration of the reduced-power-usage period, transmitting the reception period.

6. The SoC of claim 5, wherein the transmitting the reception period comprises transmitting a beacon, the beacon being part of a handshake protocol of the discovery phase.

7. A System-on-Chip (SoC) comprising:
a processor; and
a computer-readable storage memory device embodying computer-executable instructions, that, when executed by the processor, implement a power conserver configured to conserve power during a discovery phase of a wireless local area network (WLAN) by:
transmitting, from an access point of the WLAN, a first beacon, the first beacon to discover a client station with which to establish communication;
maintaining power usage at the access point for a first reception period, the power usage sufficient to enable receiving a probe request from the client station;
responsive to not receiving the probe request from the client station during the first reception period and prior to establishing a communication with the client station, reducing power usage at the access point after the first reception period ends and for a reduced-power-usage period, the reduced-power-usage period insufficient to enable receiving the probe request from the client station, the reduced-power-usage period at the access point being configured to vary according to information received by the access point from the client station indicating a radar search period for the client station;
transmitting, from the access point, a second beacon, the second beacon to discover the client station;
maintaining power usage at the access point for a second reception period, the power usage sufficient to enable receiving the probe request from the client station; and
responsive to receiving the probe request from the client station during the second reception period, responding to the probe request with a probe response, the probe response part of establishing the communication with the client station.

8. The SoC of claim 7, wherein:
transmitting the first beacon includes transmitting the first reception period, the first reception period indicating a first amount of time that the access point is capable of receiving the probe request from the client station; and
transmitting the second beacon includes transmitting the second reception period, the second reception period indicating a second amount of time that the access point is capable of receiving the probe request from the client station.

9. The SoC of claim 8, wherein the first reception period and the second reception period are identical amounts of time.

10. The SoC of claim 8, wherein the first reception period and the second reception period are different amounts of time determined based, at least in part, on a history of how quickly the access point receives the probe request from the client station.

11. The SoC of claim 10, wherein the SoC is implemented in one of:
a mobile device;
a computing device;
a media playback device;
a video rendering device;
an appliance device;
a gaming device;
a vehicle; or
a WLAN access point.

12. The SoC of claim 7, wherein the client station is required to refrain from transmitting the probe request during the radar search period.

13. The SoC of claim 7, wherein the client station is permitted to transmit the probe request if the client station does not receive radar transmissions during the radar search period.

14. The SoC of claim 7, wherein the radar search period is sixty seconds, and the probe request is transmitted in a five Giga-Hertz range.

15. The SoC of claim 7, wherein the first and second beacons are part of a handshake protocol of the discovery phase.

16. The SoC of claim 7, wherein the access point is a printing device and the client station is a personal computing device.

17. The SoC of claim 7, further comprising, prior to transmitting the second beacon:
transmitting, from the access point, a third beacon, the third beacon to discover the client station;
maintaining power usage at the access point for a third reception period, the power usage sufficient to enable receiving the probe request from the client station; and
responsive to not receiving the probe request from the client station during the third reception period, reducing power usage at the access point after the third reception period ends and for a second reduced-power-usage period, the second reduced-power-usage period insufficient to enable receiving the probe request from the client station.

18. The SoC of claim 17, further comprising:
receiving, at the access point, an indication that the radar search period has changed; and
responsive to receiving the indication, altering the reduced-power-usage period.

19. A wireless communication device comprising:
a wireless transmitter;
a wireless receiver; and
a power conserver configured to conserve power during operation of the wireless communication device by:
causing the wireless transmitter to transmit a first beacon, the first beacon to discover a client station with which to establish communication;
maintaining power usage of the wireless communication device for a first reception period, the power usage sufficient to enable the wireless receiver to receive a probe request from the client station;
responsive to the wireless receiver not receiving the probe request from the client station during the first reception period and prior to establishing a communication with the client station, reducing power usage of the wireless communication device after the first reception period ends and for a reduced-power-usage period, the reduced-power-usage period insufficient to enable receiving the probe request from the client station, the reduced-power-usage period at the wireless communication device being configured to vary according to information received by the wireless receiver from the client station indicating a radar search period for the client station;
causing the wireless transmitter to transmit a second beacon, the second beacon to discover the client station;
maintaining power usage of the wireless communication device for a second reception period, the power usage sufficient to enable receiving the probe request from the client station; and
responsive to the wireless receiver receiving the probe request from the client station during the second reception period, causing the wireless transmitter to respond to the probe request with a probe response, the probe response part of establishing the communication with the client station.

20. The wireless communication device of claim 19, wherein the wireless communication device is an access point of a wireless local area network (WLAN).