PATENT DOCUMENT

Publication Number: US-8576870-B2
Application Number: US-79757910-A
Country: US
Kind Code: B2

Title: Access point systems

Abstract:
Wireless local area networks may be established between devices. Each device may include wireless interfaces. A first device may include an infrastructure interface that supports an interface link with access point equipment on a given channel. The first device may listen for probe requests from a second device on the given channel. The second device may send probe requests on a series of channels in single-channel increments. When the second device sends the probe request on the given channel, the first device may receive the probe request. Each probe request may include an information element. The first device may extract the information element from a received probe request and may compare the extracted information element to a predetermined stored information element. If there is match, an association process may be used to establish a wireless link between the first and second devices.

Claims:
What is claimed is: 
     
       1. A method for supporting wireless networking between a first electronic device and a second electronic device, wherein the second electronic device sends a series of probe requests to the first device on a sequence of channels incremented in single-channel increments, each of the probe requests including an information element, the method comprising:
 with the first device, maintaining a first wireless local area network link with access point equipment using a given wireless local area network channel; 
 with the first device, listening for probe requests from the second device on the given wireless local area network channel; 
 with the first device, receiving a probe request from the second device; 
 with the first device, extracting the information element from the probe request and comparing the extracted information element to a predetermined information element to determine whether the extracted information element matches the predetermined information element; and 
 in response to determining that the extracted information element matches the predetermined information element, establishing a second wireless local area network link between the first device and the second device without the access point equipment. 
 
     
     
       2. The method defined in  claim 1  wherein maintaining the first wireless local area network link comprises maintaining an infrastructure link. 
     
     
       3. The method defined in  claim 2  further comprising:
 in response to establishing the second wireless local area network link, turning on beaconing in the first device. 
 
     
     
       4. The method defined in  claim 3 , further comprising turning off beaconing when the first device is wirelessly linked to only the access point equipment. 
     
     
       5. The method defined in  claim 3  wherein maintaining the first wireless local area network link comprises maintaining a link on a channel other than channels  1 ,  6 , and  11 . 
     
     
       6. The method defined in  claim 1  further comprising:
 in response to establishing the second wireless local area network link, turning on beaconing in the first device. 
 
     
     
       7. The method defined in  claim 6 , further comprising turning off beaconing when the first device is wirelessly linked to only the access point equipment. 
     
     
       8. The method defined in  claim 1  wherein maintaining the first wireless local area network link comprises maintaining a link on a channel other than channels  1 ,  6 , and  11 . 
     
     
       9. The method defined in  claim 1  wherein listening for probe requests from the second device on the given wireless local area network channel comprises listening for probe requests from the second device on the given wireless local area network channel using a non-beaconing access point interface. 
     
     
       10. A method for supporting wireless networking between a first electronic device and a second electronic device, wherein the second electronic device sends probe requests to the first device that each include an information element, the method comprising:
 with the first device, receiving a probe request from the second device; and 
 with the first device, extracting an information element from the probe request; 
 with the first device, comparing the extracted information element to a predetermined information element stored in the first device to determine whether the extracted information element matches the predetermined information element; and 
 in response to determining that the extracted information element matches the predetermined information element, establishing a wireless local area network link between the first device and the second device without access point equipment; and 
 while receiving the probe request from the second device on a given wireless local area network channel, communicating wirelessly between the first device and the access point equipment using the given wireless local area network channel. 
 
     
     
       11. The method defined in  claim 10 , wherein the second electronic device sends the probe requests to the first device as a series of probe requests on a sequence of wireless local area network channels incremented in single-channel increments and wherein the sequence of wireless local area network channels includes the given wireless local area network channel. 
     
     
       12. The method defined in  claim 11  wherein extracting the information element comprises extracting the information element from an information element list in the probe request. 
     
     
       13. The method defined in  claim 12  wherein receiving the probe request comprises receiving the probe request using a non-beaconing access point interface in the first device. 
     
     
       14. The method defined in  claim 10  further comprising:
 in response to establishing the wireless local area network link, turning on beaconing in the first device. 
 
     
     
       15. The method defined in  claim 14  wherein establishing the wireless local area network link between the first device and the second device comprises performing IEEE 802.11 association procedures. 
     
     
       16. A method for supporting wireless local area networking between a first electronic device and a second electronic device, the method comprising:
 with the second electronic device, sending a series of probe requests to the first device on a sequence of channels incremented in single-channel increments, wherein each of the probe requests includes an information element that is part of an information element list; 
 with the first device, receiving a probe request from the second device; 
 with the first device, extracting the information element from the probe request and comparing the extracted information element to a predetermined information element stored at the first device to determine whether the extracted information element matches the predetermined information element; and 
 in response to determining that the extracted information element matches the predetermined information element, establishing a wireless local area network link between the first device and the second device. 
 
     
     
       17. The method defined in  claim 16  further comprising:
 with the first device, maintaining a wireless local area network infrastructure link with access point equipment using a given wireless local area network channel; and 
 with the first device, listening for the probe requests from the second device on the given wireless local area network channel. 
 
     
     
       18. The method defined in  claim 17  further comprising:
 in response to establishing the wireless local area network link, turning on beaconing in the first device.

Description:
BACKGROUND 
     This relates generally to wireless communications, and, more particularly, to ways in which to create wireless local area networks. 
     The Institute of Electrical and Electronics Engineers (IEEE) has promulgated wireless local area network standards that govern the protocols with which computers discover and associate with access points. These protocols are sometimes referred to as the IEEE 802.11 protocols or WiFi® protocols. 
     To simplify functions such as peer-to-peer connections and make other refinements to wireless local area networking procedures, there is an interest in developing other wireless networking protocols. For example, the WiFi Alliance® has supported a protocol called WiFi Direct. 
     The WiFi Direct protocol supports peer-to-peer connections, but specifies that devices that wish to be discoverable and that are not already participating in a group must spend a certain amount of time on a fixed listen channel (channel  1 ,  6 , or  11 ) to respond to probe requests. As a result, a device with a single radio that wishes to be discoverable while simultaneously participating in an infrastructure network must split time between the channel on which the infrastructure network is operating and its listen channel. This channel hopping requirement reduces the amount of time a device is discoverable by peers, reduces throughput, and has the potential to increase power consumption. 
     It would be desirable to be able to avoid the penalties associated with this type of channel hopping while maintaining wireless local area network discoverability. 
     SUMMARY 
     Wireless local area networks may be established between devices. The devices may include computers, cellular telephones, portable electronic equipment, or other electronic devices. Each device may have wireless communications circuitry including a wireless transceiver and associated antenna structures. 
     To avoid channel hopping when supporting wireless discovery operations, a first device may listen for probe requests from a second device without changing the channel to which the wireless transceiver is tuned. 
     Each device may include wireless interfaces. For example, the first device may include an infrastructure interface that supports an interface link with access point equipment on a given channel. The first device may listen for probe requests from the second device on the given channel. 
     The second device may repeatedly send probe requests on a series of channels (i.e., all wireless local area network channels supported by the transceiver). The channels that are used to send the probe requests may be incremented in single-channel increments. This allows complete coverage of all available wireless local area network channels and ensures the one of the probe requests will eventually be sent on the given channel. 
     When the second device sends the probe request on the given channel, the first device can receive the probe request. Each probe request may include an information element that makes up part of an information element list. A valid predetermined information element may be maintained in storage in the first device. The first device may extract the information element portion of each received probe request and may compare each extracted information element to the predetermined information element. If there is match, an association process such as an IEEE 802.11 association process may be used to establish a wireless link between the first and second devices. If there is not a match, the received probe request can be ignored and the first device can continue listening for additional probe requests. Probe requests can be detected in this way without requiring the first device to transmit beacons. If desired, beaconing can be turned on once the second device has associated with the first device. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a conventional wireless network. 
         FIG. 2  is a diagram of a wireless network in accordance with an embodiment of the present invention. 
         FIG. 3  is a flow chart of illustrative steps involved in supporting discovery and association operations in a network of the type shown in  FIG. 2  in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram showing how a probe request frame of the type that may be used in the system of  FIG. 3  may contain an information element that is recognized by appropriately configured access points in accordance with an embodiment of the present invention. 
         FIG. 5  is a flow chart of illustrative steps involved in processing probe requests in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A conventional wireless network is shown in  FIG. 1 . As shown in  FIG. 1 , wireless network  10  includes access point equipment  14 . Access point equipment  14  may be, for example, a wireless router that is connected to a communications network such as the internet (network  12 ) through a modem. Devices such as computer  16  that have wireless local area network (WLAN) communications circuitry such as WLAN transceiver  26  and antenna  28  may form wireless local area network links with access point  14 . Links such as link  18  are sometimes referred to as infrastructure links or access point (AP) mode links. 
     The WLAN communications circuitry of device  16  typically includes processing circuitry for running software code. For example, this circuitry may run multiple instances of an access point module. Infrastructure interface  22  may serve as an access point connection instance and may support communications between device  16  and access point equipment  14  over infrastructure link  18 . Access point interface  24  may serve as an access point instance and may support communications between device  16  and device  32  over link  30 . Device  32  may use infrastructure interface  34  to support communications over link  30 . 
     During discovery operations before link  30  is formed, device  32  may issue probe requests to equipment  16 . In a typical scenario, device  32  uses probe request scan module  36  to issue a repeating sequence of probe requests on WLAN channels  1 ,  6 , and  11 . 
     Device interface  20  is used by device  16  to handle corresponding listening responsibilities for device  16 . In order to detect incoming probe requests, device  16  listens on a fixed listening channel selected from channels  1 ,  6 , and  11 . Because the probe requests from device  32  cycle through channels  1 ,  6 , and  11  in sequence, there will eventually be a match between the channel on which device  32  is sending a probe request and the fixed listen channel. When device  16  detects an incoming probe request, device  16  and device  32  can set up link  30  using a standards-compliant protocol (i.e., WiFi Direct). 
     Transceivers such as transceiver  26  are generally only able to tune to a single WLAN channel at a time. Transceiver  26  must therefore be shared so that some of the time transceiver  26  is tuned to the infrastructure channel for link  18  and some of the time transceiver  26  is tuned to the fixed listen channel (which is often different than the infrastructure channel). When managing the sharing of transceiver resources in device  16 , device interface  20  directs transceiver  26  to hop back and forth between these channels. To support infrastructure link  18 , transceiver  26  is tuned to the infrastructure link channel. To support listening operations, transceiver  26  is tuned to the fixed listen channel. Channel hopping in this way reduces throughput on link  18 , because transceiver  26  is not dedicated to supporting link  18 . Discovery operations also tend to be slowed, because device  16  is only listening for probe requests part of the time. 
     These issues can be addressed using a wireless system of the type shown in  FIG. 2 . As shown in  FIG. 2 , wireless network  40  may include access point equipment  44 . Access point equipment  44  may be a wireless router that is connected to a communications network such as the internet (network  42 ) through a modem, a computer serving as an access point, or any other suitable WLAN access point equipment. 
     Computing equipment  48  may be a portable computer such as a laptop computer or tablet computer, a cellular telephone or other handheld device, a desktop computer, a television, a computer monitor, or other electronic equipment that contains wireless communications circuitry. 
     Computing equipment  48  may sometimes be referred to as an electronic device. 
     Device  48  may have wireless local area network communications circuitry such as WLAN transceiver  50  and antenna  52 . In a typical scenario, WLAN transceiver  50  may be based on a wireless circuit (“radio”) that supports communications over a single WLAN channel at a time. Other types of configurations may be used if desired. For example, WLAN transceiver  50  may support multiple simultaneous WLAN channels. 
     WLAN wireless communications circuitry  50  and  52  may be used to form wireless links with access point  44 . Links such as link  46  are sometimes referred to as infrastructure links or access point (AP) mode links. 
     The WLAN communications circuitry of device  48  (and, if desired, other processors in device  48 ) serve as processing circuitry for running wireless communications software code in device  48 . This allows device  48  to run multiple instances of an access point module. For example, device  48  may include infrastructure interface  56  (serving as an access point connection instance) and one or more access point interfaces  58  (each serving as an access point instance). Infrastructure interface  56  may serve as an access point connection instance that supports communications between device  48  and equipment  44  over infrastructure link  46 . Access point interface  58  may serve as an access point instance that can be used in supporting wireless link  60  with computing equipment  62 . 
     Computing equipment  62  may be a computer, cellular telephone, or other electronic equipment that supports WLAN communications. As shown in  FIG. 2 , device  62  may have an infrastructure interface such as interface  64  to support communications with device  48  over WLAN link  60 . Multiple devices may form links with device  48  using multiple access point interfaces in device  48 , as indicated by dots  63 . 
     Scan module  66  may be used by device  62  in sending probe requests to device  48  to set up a wireless link. To avoid channel hopping, device interface  54  may direct transceiver  50  to remain tuned to the channel that is being used to support infrastructure link  46  during discovery operations. To ensure that probe requests from device  62  are detected by device  48 , device  62  may sequence through all available WLAN channels when sending probe requests. In particular, device  62  may use all-channel probe request scan module  66  to repeatedly send probe requests on channel  1 , channel  2 , channel  3 , etc. in sequence. These probe requests can be received and processed by device  48  to establish a wireless link without requiring device  48  and access point interface  58  to transmit beacon frames. Accordingly, access point interface  58  may sometimes be referred to as a non-beaconing access point interface. 
     To ensure that device  48  and device  62  can establish link  60  without using the conventional approach of  FIG. 1 , all-channel probe request scan module  66  can include a predetermined information element in each probe request. Device  48  can store a copy of the predetermined information element value in advance. When a probe request is received, device  48  can extract the information element from the probe request and can compare the extracted information element to the stored information element. If the values of the extracted information element and the stored information element match, device  48  can proceed with establishing link  60  with device  62 . If the value of the extracted information element does not match the value of the stored information element, device  48  need not take any action and the probe request can be ignored. 
     Illustrative steps involved in operating network  40  of  FIG. 2  are shown in  FIG. 3 . 
     At step  68 , device  48  may form WLAN infrastructure link  46  with access point equipment  44 . Infrastructure interface  56  may be used in supporting communication with equipment  44 . Link  46  may be formed on a given WLAN channel (e.g., one of the IEEE 802.11 2.4 GHz or 5 GHz channels such as channel  13  as just one example). Link  46  allows device  48  to access network resources through access point equipment  44 . In the example of  FIG. 2 , link  46  may be used by device  48  to access internet  42 . If desired, other resources may be accessed through access point equipment  44 . Multiple devices such as device  48  may be connected to equipment  44 . The arrangement of  FIG. 2  in which one device (device  48 ) is coupled to equipment  44  is merely illustrative. 
     At step  70 , while device  48  is linked with access point equipment  44  over infrastructure link  46  using the given channel, non-beaconing access point interface  58  may listen for a probe request from module  66  on the given channel. It is not necessary for transceiver  50  to be tuned to a different channel during the listening operations of step  70 . This allows device  48  to maintain its throughput on the given channel over link  46  while supporting discovery operations. 
     To link to equipment  48 , device  62  may, during the operations of step  70 , use scan module  66  to issue wireless probe requests. Before link  60  is established, device  62  does not know the identity of currently used infrastructure channel (the given channel used by device  48  in communicating with equipment  44 ). Probe request scan module  66  may therefore scan in sequence through all channels (i.e., all IEEE 802.11 channels). For example, scan module  66  may step through the channels one by one in sequential order without skipping channels. With this approach, probe requests are transmitted using a series of contiguous adjacent channels (i.e., channel  1 , channel  2 , channel  3 , etc.). The process may be repeated continuously (i.e., scan module  66  may transmit probe requests on all channels in a repeating sequence of channels in single-channel increments). 
     Each probe request may include an information element (i.e., an information element having a predetermined value). Device  48  may have storage in which this predetermined information element value is stored and may have processing circuitry that determines when the information element in a probe request has a value that matches the value of the stored information element and is therefore valid. When a probe request with a matching information element (i.e., a valid probe request) is received, processing may proceed to the operations of step  72 . 
     During the operations of step  72 , device  48  may, in response to receiving the valid probe request, send a wireless probe response to device  62  and may perform WLAN association procedures (e.g., IEEE 802.11 association procedures) to establish WLAN link  60  between device  48  and device  62 . Access point interface  58  in device  48  and infrastructures interface  64  in device  62  support communications over link  60 . When the link is formed, equipment  62  and  48  can share files and other resources such as access to network  42 . Links such a link  60  may sometimes be referred to as peer links. Additional links may be formed after link  60  has been formed (e.g., using the WiFi Direct protocol). 
     To support the formation of additional wireless links between device  48  and additional devices (e.g., using standards compliant protocols), WLAN beaconing may be turned on at step  74  (e.g., IEEE 802.11 beaconing may be activated so that beacon frames are transmitted device  48 ). The beacon frames may contain service set identifier (SSID) information and other beacon data. Additional devices can detect the beacons and can use information from the beacons in associating with device  48 . Whenever a device dissociates from device  48 , the wireless link between the dissociating device and device  48  is dropped. When all devices drop their links with device  48  (i.e., when device  48  is only wirelessly linked to access point equipment  44 ), beaconing may be turned off in device  48  (step  76 ). As indicated by path  78 , processing may then return to step  70  (i.e., device  48  can once again await reception of valid probe requests). 
       FIG. 4  shows an illustrative probe request (PR) frame. As shown in  FIG. 4 , probe request PR may contain header information and end of frame information. The payload of the frame may reside between the header and the end of frame information. Part of the payload may include an information element list (IE list). The information element (IE) that is extracted by device  48  during probe request processing may be one of the entries in the information element list. Any unique digital code (e.g., a binary bit pattern or an alphanumeric string) may be used as the information element. 
       FIG. 5  is a flow chart of illustrative steps that may be used during the operations of step  70  of  FIG. 3 . 
     At step  70 A, device  62  may transmit a probe request containing an information element IE while device  48  uses interface  58  to listen for probe requests from device  62  on a given wireless local area network channel (i.e., the current channel for infrastructure link  44 ). The given wireless local area network channel need not be one of the probe request channels used in conventional system  10  of  FIG. 1  (i.e., channels  1 ,  6 , and  11 ). For example, device  48  and equipment  44  may be linked over channel  13  (as an example). The probe requests sent at step  70 A may be sent as a series of probe requests on a sequence of channels that are incremented in single-channel increments (i.e., channels  1 ,  2 ,  3 ,  4 ,  5 , etc.). In a typical configuration, the channels are all adjacent and no channels are skipped in the sequence. This ensures that one of the channels that are used will match the current channel (i.e., channel  13  in this example). 
     At step  70 B, while non-beaconing access point interface  58  is listening for incoming probe requests on the given wireless local area network channel, a transmitted probe request may be received over the given wireless local area network channel (i.e., when the transmit channel for the probe request matches the current channel to which transceiver  50  is tuned). Device  48  may then proceed to process the received probe request. 
     In particular, the information element IE may be extracted from the received probe request at step  70 C. 
     At step  70 D, device  48  may retrieve its previously stored valid information element from storage in device  48  and may compare the value of this predetermined information element to the value of the extracted information element. If the extracted information element does not match the stored information element, device  48  can ignore the probe request and processing can return to step  70 A (as indicated by line  70 E). If the extracted information element is a valid match with the predetermined information element that was retrieved from storage, device  48  can conclude that the information element and the probe request in which the information element was contained are valid and that link  60  should be formed. Processing may therefore proceed to step  72  of  FIG. 3 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20100609
Publication Date: 20131105
Grant Date: 20131105
Priority Date: 20100609
Inventors: HEERBOTH PETER N.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W8/005", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W8/005", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 45096188