Patent Publication Number: US-2023156581-A1

Title: Discovery channel for unlicensed frequency band

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present Application for Patent is a Continuation of U.S. Pat. Application No. 16/995,583 filed Aug. 17, 2020, which is a continuation of U.S. Pat. Application No. 16/009,145 filed on Jun. 14, 2018, which claims priority to U.S. Provisional Pat. Application No. 62/521,989 filed Jun. 19, 2017, all entitled “DISCOVERY CHANNEL FOR UNLICENSED FREQUENCY BAND,” each of which are assigned to the assignee hereof and each of which are expressly incorporated by reference in its entirety herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to the field of network communication, and more particularly to wireless communication in an unlicensed frequency band. 
     DESCRIPTION OF THE RELATED TECHNOLOGY 
     Wireless communication technologies may use unlicensed frequency bands without obtaining a specific license from a governmental agency. Examples of unlicensed frequency bands may include 2.4 GHz frequency band (sometimes also referred to as an “industrial, scientific, and medical” or “ISM” frequency band) and a 5 GHz frequency band (sometimes also referred to as an “Unlicensed National Information Infrastructure” or “UNII” frequency band). Technology specifications are being drafted for a 6 GHz frequency band, which may support IEEE 802.11 and, optionally, other wireless technologies. 
     Within each unlicensed frequency band, there may different operating channels that can be used by an access point (AP) and station (STA) for wireless communication. In this disclosure, an AP may refer to an AP as that term is used in IEEE 802.11 wireless local area networks (WLANs) and also may refer to a base station (such as an eNodeB or Home eNodeB) as that term is used for other types of wireless networks. The AP provides wireless access for client STAs to access a network via one or more operating channels. However, due to the increasing quantity of available channels associated with each unlicensed frequency band, it may be time-consuming for a STA to determine the proper operating channel to utilize for wireless access to the AP. 
    
    
     SUMMARY 
     The systems, methods, and devices of this disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. 
     One innovative aspect of the subject matter described in this disclosure can be implemented by a first access point (AP). The first AP may utilize, from among various operating channels within an unlicensed frequency band, at least a first operating channel to provide wireless access to a network. The first AP may transmit discovery information via a dedicated discovery channel for the unlicensed frequency band. The discovery information may include a first identifier of the first operating channel utilized by the first AP. 
     In some implementations, the dedicated discovery channel may be located at a center channel of the unlicensed frequency band 
     In some implementations, the dedicated discovery channel for the unlicensed frequency band may be located outside of the unlicensed frequency band. 
     In some implementations, transmitting the discovery information may include transmitting the discovery information in a discovery message that is broadcast on the dedicated discovery channel. 
     In some implementations, the dedicated discovery channel may be known to one or more stations that utilize the unlicensed frequency band. 
     In some implementations, the dedicated discover channel may be specified by at least a first technology standard adopted by the one or more stations. 
     In some implementations, the first AP may transmit the discovery information according to a first periodic interval. 
     In some implementations, the first periodic interval may be specified by a first technology standard adopted by the one or more stations. 
     In some implementations, the first periodic interval specified by the first technology standard may be different from a second periodic interval specified by a second technology standard adopted by other stations that utilize the unlicensed frequency band. 
     In some implementations, the discovery information may further include at least one member selected from a group consisting of basic service set (BSS) information, service set identification (SSID), operating parameters for the first operating channel, wireless service capabilities of the first AP, a list of supported protocols, and a list of other channels being utilized by the first AP. 
     In some implementations, the discovery information may further include an indicator to indicate whether the first AP will permit a negotiation of one or more operating parameters shared between the first AP and a first station. 
     In some implementations, the first AP may determine a second operating channel that is utilized by a second AP. The first AP may determine aggregated discovery information that identifies the first operating channel utilized by the first AP and the second operating channel utilized by the second AP. The first AP may transmit the aggregated discovery information on the dedicated discovery channel. 
     In some implementations, the discovery information may be included in a technology-specific payload of a message transmitted on the dedicated discovery channel. The message may include a header that is decodable by a first class of devices and a second class of devices. The header may indicate a technology type of the technology-specific payload. 
     In some implementations, utilizing the first operating channel may include scheduling uplink and downlink transmissions for one or more stations on the first operating channel according to an AP-managed schedule. 
     In some implementations, transmitting the discovery information may include determining an inactive period in the AP-managed schedule, switching from the first operating channel to the dedicated discovery channel, and transmitting the discovery information on the dedicated discovery channel during the inactive period. 
     In some implementations, the dedicated discovery channel may be located at a frequency range associated with one of the plurality of operating channels. The frequency range may be used as the dedicated discovery channel during some periods of time and the frequency range is used as one of the plurality of operating channels during other periods of time. 
     In some implementations, the dedicated discovery channel may include a primary dedicated discovery channel and a secondary dedicated discovery channel. The first AP may determine that the primary dedicated discovery channel is unusable. The first AP may transmit the discovery information via the secondary dedicated discovery channel. 
     In some implementations, determining that the primary dedicated discovery channel is unusable may include determining that the primary dedicated discovery channel is saturated. In some implementations, the primary dedicated discovery channel may be temporarily unavailable. For example, the primary dedicated discovery channel may be inaccessible by any device at a particular time or location (or may be accessible only for transmission of very short packets). The first AP may transmit an indicator on the primary dedicated discovery channel to indicate that the discovery information will be transmitted via the secondary dedicated discovery channel. 
     In some implementations, determining that the primary dedicated discovery channel is unusable may include determining that the primary dedicated discovery channel is unusable due to signal interference from another transmitter or to another transmitter. 
     In some implementations, transmitting the discovery information may include utilizing a collision avoidance mechanism to contend for access to the dedicated discovery channel before transmitting the discovery information. 
     In some implementations, transmitting the discovery information may include transmitting the discovery information in a first timeslot on the dedicated discovery channel. 
     In some implementations, the first timeslot may be shared by a group of APs that include the first AP and a second AP. Each AP in the group of APs may alternate utilization of occurrences of the first timeslot in a repeating sequence of timeslots. 
     In some implementations, the first timeslot may be assigned to the first AP by a central controller. 
     Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a system diagram of an example network with multiple access points (APs) operating in an unlicensed frequency band. 
         FIG.  2    depicts an example channel map with multiple operating channels in an unlicensed frequency band. 
         FIG.  3 A  depicts an example channel map having a dedicated discovery channel for an unlicensed frequency band. 
         FIG.  3 B  depicts an example channel map having a primary dedicated discovery channel and a secondary dedicated discovery channel. 
         FIG.  4    depicts a flowchart for a first AP capable of sending discovery information via a dedicated discovery channel for an unlicensed frequency band. 
         FIG.  5    depicts a flowchart for a first station (STA) capable of receiving discovery information via a dedicated discovery channel for an unlicensed frequency band. 
         FIG.  6    depicts a message timing diagram in which discovery information can be included in a technology-specific payload of a message. 
         FIG.  7    depicts a message flow diagram of example messages in which multiple APs indicate their operating channels via a dedicated discovery channel. 
         FIG.  8    depicts a message flow diagram of example messages in which a station can negotiate operating parameters with an AP. 
         FIG.  9    depicts a message flow diagram of example messages in which a coordinating AP can provide aggregated discovery information. 
         FIG.  10    depicts a flowchart for a coordinating AP capable of providing aggregated discovery information via a dedicated discovery channel for an unlicensed frequency band. 
         FIG.  11    depicts a message timing diagram in which APs transmit discovery information in separate timeslots. 
         FIG.  12    depicts a message timing diagram in which groups of APs alternate transmission of discovery information in respective timeslots. 
         FIG.  13    depicts a message timing diagram in which groups of APs transmit aggregated discovery information. 
         FIG.  14 A  depicts a conceptual diagram of an example discovery message for transmitting discovery information. 
         FIG.  14 B  depicts an example message format for an example discovery message. 
         FIG.  14 C  depicts an example message format for an example discovery message and example discovery information elements. 
         FIG.  14 D  depicts a conceptual diagram of an example discovery message with long-term evolution (LTE) signaling frames. 
         FIG.  15    shows a block diagram of an example electronic device for implementing aspects of this disclosure. 
       Like reference numbers and designations in the various drawings indicate like elements. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is directed to certain implementations for the purposes of describing the innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device, system or network that is capable of transmitting and receiving RF signals according to any of the wireless communication standards, including any of the IEEE 802.11 standards, the Bluetooth® standard, code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless, cellular or internet of things (IOT) network, such as a system utilizing 3G, 4G or 5G, or further implementations thereof, technology. 
     A network in a home, apartment, business, or another area may include one or more access points (APs). In some deployments, the APs may be associated with a same local area network. The local area network (LAN) (sometimes also referred to as a wireless local area network or WLAN) may provide access to a broadband network. For example, a gateway device (such as a central AP or router) can couple to the broadband network through a cable, a fiber optic, a powerline, or DSL network connection. In other deployments, there may be multiple APs within an environment which are related to different networks. The multiple APs may each operate on one or more operating channels within an unlicensed frequency band. A channel may refer to a portion of the unlicensed frequency band. Each channel may have a pre-defined central frequency and channel width. An operating channel is used by the AP to communicate with stations (STAs) that have a wireless association with the AP. Similarly, the STAs utilize the channel to communicate (via a wireless association) with the AP. The IEEE 802.11 standards may define a Basic Services Set (BSS) as one wireless interface of the AP, the operating channel (and its configuration), and all devices that are associated with the wireless interface. Some APs are capable of determining which operating channel is least congested and establishing itself on that operating channel. In some implementations, a central controller may assign the operating channels that can be used by each AP within a geographic area. 
     The concepts in this disclosure may be used with any unlicensed frequency band (or collection of unlicensed frequency bands). However, for brevity, this disclosure uses the 6 GHz unlicensed frequency band as an example for several of the Figures. The 6 GHz band is expected to be an unlicensed frequency band which is open for operation by next generation APs and STAs. For example, the 6 GHz band may be used by IEEE 802.11 devices that follow the 802.11ax amendment or beyond. The 6 GHz band also may be concurrently used by other types of wireless communication technologies, including LTE, Bluetooth™, or other technologies. Wireless transmissions on the operating channels within the 6 GHz band may be fully scheduled (rather than contention based access). An AP may schedule all transmissions by the AP or STAs within the BSS. In this disclosure, an AP refers to any type of access point (or base station) that may utilize the unlicensed frequency band and which provides wireless access via an operating channel in the unlicensed frequency band. While the channel map for the 6 GHz band has not been ratified yet, it is expected to provide a greater number of operating channels than previously available. While this increases the quantity of APs (and wireless communication technologies) which may coexist in the 6 GHz band, this may create a problem for STAs to determine availability and operating channels for the APs in an environment. For example, the STA may use active scanning or passive scanning (both of which are described in more detail in  FIG.  2   ) to identify and locate available APs. However, traditional procedures for active scanning and passive scanning can be time consuming and may consume more power in the unlicensed frequency band due to the larger quantity of operating channels. 
     In accordance with this disclosure, a dedicated discovery channel can be used to advertise operating channels regarding multiple APs. For example, the dedicated discovery channel can be reserved for use by an AP to announce discovery information about which operating channel(s) are being used. The discovery information also may include information about the BSS, current channel conditions, or operating parameters associated with the operating channel used by the AP. The discovery information may be sent in periodic messages having a predetermined interval known by all STAs that can access that unlicensed frequency band. In some implementations, the discovery information includes minimal information for a STA to determine whether the AP to which they intend to associate is operating in the area. The discovery information also may include the operation modes (capabilities, functionalities, or the like), that the AP desires the STA to have enabled before associating with the AP and also may contain the subset of channels (and other resources) the AP is using in its BSS. 
     Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. The discovery information for multiple APs may be transmitted in the same dedicated discovery channel of the unlicensed frequency band. This may obviate the need for the STA to actively or passively scan all of the operating channels to find a particular AP’s operating channel. Furthermore, a potential uncertainty could exist if the STA does not know how long to wait in the absence of the discovery information. In an implementation, the discovery information is sent according to a predetermined interval that is known to devices that utilize the unlicensed frequency band. In this implementation, the devices can rely on receiving the discovery information within the predetermined interval. The discovery information may enable STAs to determine if they are eligible to operate with a particular AP. For example, even if a STA may satisfy the requirements for a wireless association with a first AP, the first AP may impose restrictions that may not be satisfactory to the STA. The discovery information may include enough information for the STA to determine whether to associate with the first AP as well as the operating channel of the first AP. The discovery information also may indicate whether the first AP will permit a negotiation between the STA and the first AP regarding wireless access parameters. 
       FIG.  1    depicts a system diagram of an example network with multiple APs operating in an unlicensed frequency band. The network  100  includes multiple APs, including a first AP  110 , a second AP  120 , and a third AP  130 . Each of the multiple APs may provide wireless access for STAs (not shown) within a wireless coverage area. For example, in  FIG.  1   , the first AP  110  is providing a first wireless coverage area  115 , the second AP  120  is providing a second wireless coverage area  125 , and the third AP  130  is providing a third wireless coverage area  135 . Each AP may utilize a different operating channel within its respective wireless coverage area. As described above, an operating channel may be specified within an unlicensed frequency band. Because the operating channels may have different frequency ranges, they may coexist within the same environment. For example, shown at area  190 , all three of the first wireless coverage area  115 , the second wireless coverage area  125 , and the third wireless coverage area  135  may successfully be used in the area  190  because they are using different operating channels. In some cases, the operating channels may have frequency ranges that overlap each other slightly without negating the benefits of frequency separation. 
     In some implementations, a central controller  150  may assign the operating channels which can be used by each AP. For example, shown as dotted lines  152 , the central controller  150  may have the authority to assign the operating channels used by each of the first AP  110 , the second AP  120 , and the third AP  130 . The central controller  150  may be in the same logical network as one of the APs or may be separate. In some implementations, the central controller  150  is geographically located near the environment where the APs are operating. While in other implementations, the central controller  150  may be geographically distant from where the APs operate but may still provide management oversight to assign the operating channels within the unlicensed frequency band. In some implementations, the central controller may be one of the APs. 
     In the 6 GHz unlicensed frequency band, the assignment of operating channels may be managed, or coordinated, by a central entity. The channel map for the 6 GHz unlicensed frequency band has not yet been ratified. However,  FIG.  6    provides an example in which to describe operating channels within an unlicensed frequency band, and some of the challenges that may result from active scanning or passive scanning a large quantity of operating channels. 
       FIG.  2    depicts an example channel map with multiple operating channels in an unlicensed frequency band. The example channel map  200  shows an unlicensed frequency band  290  having many operating channels, including a first operating channel  215 , a second operating channel  225 , a third operating channel  235 , a fourth operating channel  245 , and a fifth operating channel  255 . These first set of operating channels may be considered non-overlapping because there is frequency separation between them. However, in a typical channel map, the channel definitions may include overlapping channels, such as overlapping channels  251 ,  252 ,  253 , and  254 . Each of the operating channels ( 215 ,  225 ,  235 ,  245 ,  251 ,  252 ,  253 ,  254  and  255 ) may be referred to by a channel number. Each channel may be defined by a center frequency and a channel width, such as the center frequency  280  and channel width  295  associated with the first operating channel  215 . Although each channel in the channel map  200  shows a uniform channel width, an unlicensed frequency band may define different channel widths for each channel in the unlicensed frequency band. Furthermore, channels in an unlicensed frequency band may not be adjacent to each other. Channel numbering (such as lowest to highest) may be unrelated to the frequency; for example, there can be a pre-defined mapping of channels and the channels may be spread throughout the unlicensed frequency band. 
     Absent the improvement of this disclosure, a traditional STA may scan the operating channels to locate which operating channel is being used by an AP of interest to the STA. Two scanning methods are traditionally used: active scanning and passive scanning. These are described below, along with potential challenges associated with each. 
     In active scanning, a STA tunes to an operating channel, sends a message (such as a probe request message), and waits for a period of time to receive a response (such as a probe response) from an AP on that operating channel. If the STA does not receive a response from the AP of interest, then the STA switches to another operating channel and performs the same process (probe request, and wait for probe response). On each operating channel, the STA may wait for a minimal amount of time before determining that there is no response and switching to the next candidate operating channel. However, this can be time-consuming if the STA actively scan multiple operating channels before receiving a response from the desired AP. Furthermore, if there are many STAs that are actively scanning the unlicensed frequency band, there may be a pollution of probe requests and probe responses. And each time the STA performs an active scan, the STA may consume more power due to transmission and reception of messages on multiple operating channels. 
     In passive scanning, each AP is configured to periodically generate and transmit messages to advertise its presence, capabilities and other information. For example, in IEEE 802.11, an AP may transmit frames (referred to as “beacon” frames) every beacon interval. A STA may tune to an operating channel, and monitor the channel for a period of time (associated with the beacon interval) to receive a beacon frame from an AP on that operating channel. If the STA does not receive a response from the AP of interest, then the STA switches to another operating channel and performs the same process (monitor and wait for beacon frame). As with active scanning, a STA that is using passive scanning may scan multiple operating channels before receiving a beacon frame from the desired AP. 
     The amount of time used by a STA to perform active scanning or passive scanning may depend on the wait time on each channel and the quantity of operating channels that are scanned before locating the proper operating channel for an AP of interest. For example, the amount of time may be calculated in terms of a worst case as being T*N, where T is the minimum amount of wait time residing in one channel, and N is the total quantity of channels in the unlicensed frequency band. For passive scanning, the minimum amount of wait time to monitor for a beacon frame may be unknown by the STA. For example, if the STA is scanning each channel for 20 ms (expecting the beacon interval to be 20 ms or less), the STA may miss a beacon frame from an AP that has a much larger beacon interval (such as 400 ms). The beacon interval may be specific to each AP and may be inconsistent among the various operating channels. 
     As described above, the quantity of channels may greatly impact the amount of time that could be consumed by a STA that is performing active scanning or passive scanning. In the 2.4 GHz unlicensed frequency band, there are 14 channels defined. However, each jurisdiction may determine which channels are allowed to be used in that jurisdiction. In the United States., 11 channels from the 2.4 GHz band are allowed to be used for unlicensed transmissions by IEEE 802.11 equipment. In the 5 GHz unlicensed frequency band, there are 23 non-overlapping channels defined (40 total channels counting overlapping channels). Some STAs may be capable of utilizing both the 2.4 GHz band and the 6 GHz band. Thus, the STA may perform active or passive scanning for the combination of channels from multiple unlicensed frequency bands. Furthermore, there are expected to be many more channels defined in the 6 GHz unlicensed frequency band. For example, it is expected that the channel map for the 6 GHz channel map may include 160 channels or more. 
     For a STA that wishes to locate an AP in the 6 GHz unlicensed frequency band, the process of active scanning or passive scanning may take a significantly longer time due to the quantity of channels. Furthermore, the power consumption of tuning to each operating channel and transmitting or scanning multiple channels may be disadvantageous, especially for battery-powered STAs. In accordance with this disclosure, these potential disadvantages of legacy techniques for scanning may be overcome by the introduction of a dedicated discovery channel. 
     In some implementations, the dedicated discovery channel can be used to provide discovery information for multiple unlicensed frequency bands. For example, a dedicated discovery channel can include discovery information for one or more of sub 1 GHz, 2.4 GHz, 5 GHz and 6 GHz operating channels. 
       FIG.  3 A  depicts an example channel map having a dedicated discovery channel for an unlicensed frequency band. The example channel map  301  is similar to the channel map  200  of  FIG.  2   , including the definition of various channels within the unlicensed frequency band  290 . However, in  FIG.  3 A , one of the channels is specified as a dedicated discovery channel  310 . In one alternative, as shown in  FIG.  3 A , the dedicated discovery channel  310  may be in a center channel. For example, one of the channels may be reserved for use as the dedicated discovery channel  310  and may not be available as an operating channel. Although the example in  FIG.  3 A  shows the dedicated discovery channel  310  as the center-most channel within the unlicensed frequency band  290 , other alternative locations may be possible. For example, the dedicated discovery channel  310  may be a lowest numbered channel or highest numbered channel within the spectrum associated with the unlicensed frequency band  290  (or any channel). Even though some examples in this disclosure show the dedicated discovery channel occupying a particular channel (such as the center channel or lowest numbered channel), the dedicated discovery channel may occupy any one of the channels in the unlicensed frequency band  290 . In some implementations, the dedicated discovery channel  310  may occupy only a portion of one of the operating channels. For example, a frequency range associated with an operating channel may be time-divided so that the frequency range is used as the dedicated discovery channel  310  during some periods of time and the frequency range may be used as an operating channel during other periods of time. In another alternative, the dedicated discovery channel  310  may be in a reserved spectrum that is adjacent to the unlicensed frequency band  290  (or even in a separate frequency range from the unlicensed frequency band  290 ) and not within of the unlicensed frequency band  290 . Thus, in this alternative, the dedicated discovery channel  310  may be associated with the unlicensed frequency band  290  without occupying the frequency range associated with the unlicensed frequency band  290 . For example, it may be possible to define a dedicated discovery channel within another frequency band (such as the 2.4 GHz band, the 5 GHz band, or another band) which is used by APs to advertise the operating channel(s) they are using within an unlicensed frequency band (such as the 6 GHz band). 
     Regardless of the location of the dedicated discovery channel  310 , the dedicated discovery channel  310  may be specified by one or more technology standards that would use the 6 GHz unlicensed frequency band. In some implementations, the APs and STAs that will utilize operating channels within the unlicensed frequency band would be pre-configured with the location of the dedicated discovery channel  310 . In some implementations, a central resource (such as a server at a service provider, regulatory agency, third party provider, or central coordinator) can maintain a record of which dedicated discovery channel is used at various locations. For example, a device such as a STA) may contact the central resource to determine the location of the dedicated discovery channel  310 . 
     One or more APs can send discovery information on the dedicated discovery channel  310 . A STA can monitor the dedicated discovery channel  310  to receive the discovery information from the one or more APs. Thus, the STA can monitor a single channel (the dedicated discovery channel  310 ) to obtain the discovery information (and possibly more information) that it would previously have obtained by switching or scanning the various operating channels individually. Furthermore, each AP may be configured to transmit the discovery information using a predefined periodic interval. For example, a technology standard may define the periodic interval. A STA could be configured to monitor the dedicated discovery channel  310  for the time period associated with the periodic interval. This would enable the STA to monitor for a time period and obtain the discovery information for all APs that support a particular technology standard. This discovery process may reduce the amount of time needed by a STA to obtain the discovery information for multiple APs which may be utilizing operating channels within the unlicensed frequency band. 
     In some implementations, an AP that is utilizing an operating channel may manage the schedule for the uplink and downlink transmissions on the operating channel. For example, the AP may manage an AP-managed schedule that controls when one or more stations can transmit on the operating channel. Therefore, the AP will not expect unsolicited uplink traffic from stations on the operating channel. The AP could determine an inactive period in the AP-managed schedule. During the inactive period, the AP could switch from the operating channel to the dedicated discovery channel to transmit the discovery information on the dedicated discovery channel. 
       FIG.  3 B  depicts an example channel map having a primary dedicated discovery channel and a secondary dedicated discovery channel. The example channel map  302  is similar to the channel map  301  of  FIG.  3 A , including the definition of various channels within the unlicensed frequency band  290 . In  FIG.  3 B , the dedicated discovery channel is depicted as a lowest numbered channel (such as at the beginning of the unlicensed frequency band). Furthermore,  FIG.  3 B  illustrates an implementation in which the dedicated discovery channel may occupy more than one of the channels in the channel map. For example, a primary dedicated discovery channel  311  may be similar to the dedicated discovery channel  310  described in  FIG.  3 A . However, when the primary dedicated discovery channel  311  becomes overcrowded or cannot be utilized in the environment, a secondary dedicated discovery channel  320  may be utilized. Although the primary dedicated discovery channel is shown as the lowest numbered channel and the secondary channel is shown as the next channel, the primary and secondary dedicated discovery channels can be any of the channels of the unlicensed frequency band. 
     The secondary dedicated discovery channel  320  may serve as an overflow or extension of the primary dedicated discovery channel  311 . In some implementations, the secondary dedicated discovery channel  320  may serve as a replacement of the primary dedicated discovery channel  311  (such as when the primary dedicated discovery channel  311  is unusable due to signal inference from another transmitter). In some implementations, the secondary dedicated discovery channel  320  may be predetermined and reserved for use as needed (such as when the primary dedicated discovery channel  311  has become crowded or saturated by other APs transmitting discovery information). In some implementations, an AP can include an indicator or signal on the primary dedicated discovery channel  311  to cause the STA to also monitor the secondary dedicated discovery channel  320 . In some implementations, the secondary dedicated discovery channel  320  may share time with an operating channel in the same frequency range. 
       FIG.  4    depicts a flowchart for a first AP capable of sending discovery information via a dedicated discovery channel for an unlicensed frequency band. The flowchart  400  begins at block  410 . At block  410 , the first AP may utilize at least a first operating channel to provide wireless access to a network. The first operating channel may be one of the operating channels within an unlicensed frequency band. In some implementations, the first AP may utilize more than one operating channel. 
     At block  420 , the first AP may transmit discovery information via a dedicated discovery channel for the unlicensed frequency band. The discovery information may include a first identifier of the first operating channel utilized by the first AP. For example, the discovery information may include a channel number (or a list of channel numbers) that the first AP is utilizing to provide wireless access. The discovery information also may include information about a BSS of the first AP. For example, the discovery information may include the SSID of the BSS that is operating on the first operating channel. 
     As described further below, the discovery information may be included in a discovery message (such as a discovery frame, enhanced beacon frame, or a synchronization frame) that is broadcast on the dedicated discovery channel. There may be different mechanisms for the one or more APs to transmit discovery information on the dedicated discovery channel. In some implementations of the dedicated discovery channel, a collision avoidance mechanism may be used by the APs, such that each AP monitors the dedicated discovery channel before transmitting a discovery message. An example collision avoidance mechanism might be the enhanced distributed channel access (EDCA) which is defined in IEEE 802.11. Another example might be the listen before talk (LBT) access mechanism. To prevent extending beyond the periodic interval for sending discovery information, the first AP may begin collision avoidance early so that if a collision occurs, the first AP can still send the discovery information within the period interval. In some implementations of the dedicated discovery channel, a timeslot mechanism may be used, such that each AP has a timeslot in which to transmit the discovery information. An example of the timeslot mechanism might be similar to time division multiple access (TDMA) in which collisions are avoided by assigning APs to different TDMA timeslots. These mechanisms are further described below in relation to  FIGS.  11 - 13   . 
       FIG.  5    depicts a flowchart for a first STA capable of receiving discovery information via a dedicated discovery channel for an unlicensed frequency band. The flowchart  500  begins at block  510 . 
     At block  510 , the first STA may receive, from a first AP, first discovery information via a dedicated discovery channel for an unlicensed frequency band. The first discovery information may include a first identifier of a first operating channel from among various operating channels within the unlicensed frequency band. The first operating channel is utilized by the first AP to provide wireless access to a network. The first discovery information also may include information about a BSS (such as the SSID) operated on the first operating channel. 
     At block  520 , the first STA may associate with the first AP on the first operating channel. For example, the first STA may determine from the first discovery information that the first AP has the SSID that the first STA is configured to utilize. In that case, the first STA can tune to the first operating channel for the first AP and establish a wireless association with a BSS having the SSID. 
     In some implementations, the first STA also may receive second discovery information (on the dedicated discovery channel) from a second AP. The second discovery information may include a second identifier of a second operating channel being utilized by the second AP to provide wireless access. The first STA may select the first AP based, at least in part, on the first discovery information and the second discovery information. For example, if the first discovery information and the second discovery information include SSIDs for the BSSs on the first operating channel and the second operating channel, respectively, the first STA can select the first AP having the SSID that the STA is looking for. In another example, the first STA may determine service capabilities for the first AP and the second AP. The service capabilities may be advertised in the first discovery information and the second discovery information, respectively. The first STA may select the first AP based, at least in part, on the service capabilities. 
       FIG.  6    depicts a message timing diagram in which discovery information can be included in a technology-specific payload of a message. Another interesting feature of the proposed 6 GHz unlicensed frequency band is that the operating channels may be used by devices having different technology types. For example, in addition to IEEE 802.11 devices, various operating channels within the spectrum could be used by other technologies. One example of another technology being proposed is LTE for unlicensed spectrum being developed by the 3 rd  Generation Partnership Project (3GPP) standards-setting body. Other technologies also may be developed to utilize the 6 GHz unlicensed frequency band. In accordance with this disclosure, multiple technology types may transmit discovery information on the dedicated discovery channel to advertise utilized operating channels. However, there may be an opportunity for coordinating the structure of a discovery message such that at least part of the discovery message can be decoded by STAs implementing different technology types. 
     In the message timing diagram  600 , an access point  610  may transmit (shown at  655 ) a discovery message  670  on the dedicated discovery channel. The discovery message  670  may include a header  672  before a technology-specific payload  674 . The header  672  may be uniformly defined for multiple technology types. For example, the IEEE 802.11 specification and LTE specification may use a consistent definition of the structure and contents of the header  672 . The header  672  may include an indication of the technology type that the access point  610  is utilizing for the technology-specific payload  674 . 
       FIG.  6    shows two STAs that may receive the discovery message  670 . A first STA  601  may belong to a first class of devices and may implement a first technology type used by the first class of devices. For example, the first STA  601  may implement an IEEE 802.11 technology. The second STA  602  may belong to a second class of devices and may implement a second technology type used by the second class of devices. For example, the second STA  602  may implement an LTE technology. 
     In  FIG.  6   , both the first STA  601  and the second STA  602  may begin reception of the discovery message  670 . For example, the first STA  601  may receive (shown at  611 ) the discovery message  670  and decode the header  672 . The first STA  601  may determine from the header  672  that the discovery message  670  includes a technology-specific payload  674  that is relevant to the first class of devices. In response to determining that the first STA  601  implements the technology type of the technology-specific payload  674 , the first STA  601  may continue to receive the discovery message  670  and decode the technology-specific payload  674 . For example, shown at  615 , the first STA  601  may stay in a receive mode for the remaining duration of the discovery message  670 . 
     In contrast to the first STA  601 , the second STA  602  may not implement a technology type for the technology-specific payload  674 . The second STA  602  may begin reception of the discovery message  670  (shown at  612 ). The second STA  602  may decode the header  672  and determine from the header  672  that the discovery message  670  includes a technology-specific payload  674  that is not relevant to the second class of devices. In response to determining that the second STA  602  does not implement the technology type of the technology-specific payload  674 , the second STA  602  may disregard the technology-specific payload  674 . In some implementations, the second STA  602  may enter a power saving mode (shown at  616 ) for a remaining duration of the discovery message  670 . 
       FIG.  7    depicts a message flow diagram of example messages in which multiple APs indicate their operating channels via a dedicated discovery channel. The message flow diagram  700  shows the first AP  110 , the second AP  120 , and the third AP  130  sending discovery information to a STA  701 . For example, the first AP  110  sends a first discovery message  712  to the STA  701 . The second AP  120  sends a second discovery message  722  to the STA  701 . The third AP  130  sends a third discovery message  732  to the STA  701 . Each of the discovery messages  712 ,  722 , and  732  are transmitted on the dedicated discovery channel. The STA  701  may monitor the dedicated discovery channel for a period of time to receive the discovery messages from any APs which are within range of the STA  701 . 
     In some implementations, the discovery messages  712 ,  722 , and  732  may be short messages (such as a short beacon message or a short system information message). The discovery messages  712 ,  722 , and  732  may be transmitted often (such as a short periodic interval between repeating the discovery messages  712 ,  722 , and  732 ) so that the STA can monitor the dedicated discovery channel and quickly discover the APs in that location. The short discovery messages  712 ,  722 , and  732  may provide enough information (such as an operating channel and SSID, or equivalent) so that the STA  701  can decide whether to go to a particular operating channel. In some implementations, the discovery messages  712 ,  722 , and  732  may include capability information about the capabilities available at the AP (such as a list of protocols, operation, functionalities supported by AP). In some implementations, the discovery messages  712 ,  722 , and  732  may include AP requirements information about the capabilities that the AP desires that the STA have before the STA  701  can utilize the AP (such as a list of protocols, operation, functionalities supported by STA). In some implementations, the discovery messages  712 ,  722 , and  732  may include BSS operation parameters (such as the location of operating channels for the BSS of the AP, dynamically changing parameters or the like). 
     At  742 , the STA  701  may select which AP to utilize based on the discovery information in the discovery messages  712 ,  722 , and  732 . Ideally, the discovery messages  712 ,  722 , and  732  include the information typically used by the STA  701  to select an AP. However, if the STA  701  needs additional information (other than what is included in the discovery messages  712 ,  722 , and  732 ), the STA  701  may tune (not shown) to one or more of the operating channels advertised in the discovery messages  712 ,  722 , and  732  to obtain the additional information from the APs. In the example of  FIG.  7   , the STA  701  selects the third AP  130 . 
     After selecting the third AP  130  at  742 , the STA  701  may tune to the operating channel where the BSS for the third AP  130  is operating. In the operating channel, the STA  701  can send frames to the third AP  130 . At  795 , the STA  701  establishes a wireless association with the selected third AP  130 . In some implementations, the third AP  130  schedules the use of the operating channel. If the operating channel is scheduled by the third AP  130 , the STA  701  may wait for a trigger frame  792  that allocates random resource units (Rus) that the STA  701  can contend for access to the operating channel. Alternatively, the STA  701  can contend to send the frames in another unlicensed frequency band (such as a frequency band different from the 6 GHz frequency band) if the third AP  130  has indicated that it is also operating in that other band. For example, the third discovery message  732  may indicate a list of channels which the third AP  130  is operating. 
       FIG.  8    depicts a message flow diagram of example messages in which a station can negotiate operating parameters with an AP. The message flow diagram  800  shows the first AP  110 , the second AP  120 , and the third AP  130  sending discovery information to the STA  701 , similar to  FIG.  7   . Similar to  FIG.  8   , at  742 , the STA  701  may select the third AP  130 . However,  FIG.  8    differs from  FIG.  7    in that the third AP  130  may permit a negotiation of operating parameters. 
     For example, in some cases, either the STA  701  or the third AP  130  may not satisfy the requirements of the other. In such a case the STA  701  may negotiate one or more operating parameters with the third AP  130 . The STA  701  can send a request  858  (on the operating channel for the third AP  130 ) to inquire if the third AP  130  may permit the STA  701  to associate even though the STA  701  may not satisfy a requirement of the third AP  130  that was advertised in the third discovery message  732 . In some implementations, the STA  701  may wait for a trigger frame  856  before sending the request  858 . 
     The third AP  130  may process the request at  862 . In the example of  FIG.  8   , the third AP  130  determines to agree with the request. The third AP  130  may transmit a response  864  to indicate that the request has been granted. The message flow diagram  800  continues with the operations at  792  and  795  as described in  FIG.  7   . 
     In some implementations, the third AP  130  may preemptively advertise that the third AP  130  will permit a negotiation. For example, an indicator in the third AP  130  may indicate that the third AP  130  will permit the negotiation on the operating channel. 
       FIG.  9    depicts a message flow diagram of example messages in which a coordinating AP can provide aggregated discovery information. The message flow diagram  900  shows the first AP  110 , the second AP  120 , the third AP  130  and the STA  701 , similar to  FIG.  7   . However,  FIG.  9    differs from  FIG.  7    in that the message flow diagram  900  shows a coordinating AP  950  which may be used to send aggregated discovery information on the dedicated discovery channel. In some implementations, the coordinating AP  950  may be an AP that is utilizing an operating channel for a BSS of its own. In some implementations, the coordinating AP  950  may be a central controller, central access point (CAP), router, or some other device which is capable of collecting and aggregating discovery information from multiple APs. For example, the coordinating AP  950  may or may not have an operating channel of its own, but may be configured for managing and broadcasting the discovery information on the dedicated discovery channel. 
     The message flow diagram  900  shows the first AP  110 , the second AP  120 , and the third AP  130  sending the discovery information to the coordinating AP  950  which can aggregate the discovery information for multiple APs. For example, the first AP  110  sends a first discovery message  912  to the coordinating AP  950 . The second AP  120  sends a second discovery message  922  to the coordinating AP  950 . The third AP  130  sends a third discovery message  932  to the coordinating AP  950 . In some implementations, each of the discovery messages  912 ,  922 , and  932  are transmitted on the dedicated discovery channel. In some implementations, the discovery messages  912 ,  922 , and  932  may be transmitted to the coordinating AP  950  using one or more different channels than the dedicated discovery channel. 
     At  942 , the coordinating AP  950  may aggregate the discovery information from the discovery messages  912 ,  922 , and  932 . At  952 , the coordinating AP  950  may transmit the aggregated discovery information on the dedicated discovery channel. The STA  701  can monitor the dedicated discovery channel to obtain the aggregated discovery information for the multiple APs (including the first AP  110 , the second AP  120 , and the third AP  130 ). The message flow diagram  800  continues with the operations at  742  and  795  as described in  FIG.  7   . 
       FIG.  10    depicts a flowchart for a coordinating AP capable of providing aggregated discovery information via a dedicated discovery channel for an unlicensed frequency band. The flowchart  1000  begins at block  1010 . 
     At block  1010 , the coordinating AP may receive, from a first AP, first discovery information that includes a first identifier of a first operating channel from among various operating channels within an unlicensed frequency band. The first operating channel may be utilized by the first AP to provide wireless access to the first AP. 
     At block  1020 , the coordinating AP may receive, from a second AP, second discovery information that includes a second identifier of a second operating channel from among the various operating channels within the unlicensed frequency band. The second operating channel may be utilized by the second AP to provide wireless access to the second AP. 
     At block  1030 , the coordinating AP may determine aggregated discovery information based, at least in part, on the first discovery information and the second discovery information. 
     At block  1040 , the coordinating AP may transmit the aggregated discovery information via a dedicated discovery channel for the unlicensed frequency band. 
       FIG.  11    depicts a message timing diagram in which APs transmit discovery information in separate timeslots. As mentioned above, the APs may use a collision avoidance mechanism (or contention-based access mechanism) to access the dedicated discovery channel. However, in  FIG.  11   , each AP has an assigned timeslot. Thus,  FIG.  11    shows a timeslot based mechanism for scheduling when the APs can transmit discovery information. 
     The message timing diagram  1100  shows discovery messages  1112 ,  1122 ,  1132 , and  1142  transmitted by a first AP  110 , second AP  120 , third AP  130  and fourth AP  140 , respectively. A first discovery message  1112  is transmitted by the first AP  110  during a first timeslot TS 1   1171 . A second discovery message  1122  is transmitted by the second AP  120  during a second timeslot TS 2   1172 . A third discovery message  1132  is transmitted by the third AP  130  during a third timeslot TS 3   1173 . A fourth discovery message  1142  is transmitted by the fourth AP  140  during a fourth timeslot TS 4   1174 . 
     In the example of  FIG.  11   , the dedicated discovery channel is split into four repeating timeslots. Thus, after TS 1 , TS 2 , TS 3 , and TS 4 , the next timeslot will be timeslot TS 1   1175 . The first AP  110  is configured to transmit discovery information according to a periodic advertisement interval  1118  which is every four timeslots. Thus, the first AP  110  transmits a fifth discovery message  1114  at the timeslot TS 1  1175 . Similarly, the second AP  120 , the third AP  130 , and the fourth AP  140  may repeat transmissions (not shown) in subsequent timeslots according to the pattern. 
     The example in  FIG.  11    shows four APs which are assigned one of four timeslots. Thus, the simple example shows the same quantity of APs and timeslots. Each AP has a separate timeslot which repeats according to the periodic advertisement interval  1118 . However, it may be possible that the quantity of APs and the quantity of timeslots will not be the same. If there are less APs than the quantity of timeslots, it may still be possible to assign each AP a separate timeslot for transmitting its discovery information. The unused timeslots may be used when a new AP is added to the environment or may be assigned for some other transmissions (such as coordination between APs regarding the utilization of the operating channels). 
     However, there may be scenarios where the quantity of APs is greater than the quantity of timeslots defined for the dedicated discovery channel. For example, a dense deployment may include 200 APs. However, the dedicated discovery channel may define timeslots of 1 ms for each timeslot. If one AP is configured to transmit discovery information every 100 ms (for example the periodic advertisement interval may be 100 ms for the AP), the AP may not be able to transmit discovery information every 100 ms without impacting the time available for other APs to transmit discovery information on the dedicated discovery channel.  FIGS.  12  and  13    provide some solutions which may be used to support more APs in a time-based mechanism on the dedicated discovery channel. 
       FIG.  12    depicts a message timing diagram in which groups of APs alternate transmission of discovery information in respective timeslots. In  FIG.  12   , groups of APs may take turns advertising during a particular slot (such as every odd/even slot or every nth occurrence of the timeslot). The message timing diagram  1200  shows two repeating timeslots (such as timeslot TS 1   1271 , and timeslot TS 2   1272 ) which are shared by four APs (first AP  110 , second AP  120 , third AP  130  and fourth AP  140 ). In  FIG.  12   , the first AP  110  and the third AP  130  are grouped together to share TS 1 . The second AP  120  and the fourth AP  140  are grouped together to share TS 2 . Each group will share the TS 1  by alternating which AP can transmit during the timeslot. In an example when the group has 3 APs, then each AP may transmit every 3 rd  occurrence of the timeslot. 
     In the timeslot TS 1   1271 , the first AP  110  may transmit a first discovery message  1212 . Although the third AP  130  is also assigned to use the timeslot TS 1   1271 , the third AP  130  will refrain (shown at  1232 ) from sending a discovery message during this occurrence of the timeslot. In the timeslot TS 2   1272 , the second AP  120  may transmit a second discovery message  1222 . Although the fourth AP  140  is also assigned to use the timeslot TS 2   1272 , the fourth AP  140  will refrain (shown at  1242 ) from sending a discovery message during this occurrence of the timeslot. 
     At the next occurrence of TS 1  (shown at timeslot TS 1   1273 ), the first AP  110  will refrain (shown at  1216 ) from transmitting a discovery message. Instead, the third AP  130  will transmit a third discovery message  1236  during that timeslot TS 1    1273 . Thus, the first AP  110  and third AP  130  have alternated which AP is transmitting discovery information during occurrences of TS 1 . 
     Similarly, at the next of occurrence of TS 2  (shown at timeslot TS 2   1274 ), the second AP  120  will refrain (shown at  1226 ) from transmitting a discovery message. Instead, the fourth AP  140  will transmit a fourth discovery message  1246  during that timeslot TS 2   1274 . Thus, the second AP  120  and fourth AP  140  have alternated which AP is transmitting discovery information during occurrences of TS 2 . The pattern may repeat (not shown) for subsequent occurrences of TS 1  and TS 2 . 
     In the example of  FIG.  12   , the periodic advertisement interval  1118  is equivalent to four timeslots. Thus, even though the dedicated discovery channel is defined to include two repeating timeslots, the first AP  110  will still send a discovery message  1218  at the end of the periodic advertisement interval  1118 . However, there may be implementations when the quantity of APs assigned to the repeating timeslots prevents an AP from transmitting discovery information within the time period associated with the advertisement interval. In this case, it may be possible for one AP to include discovery information for another AP, as shown in  FIG.  13   . 
       FIG.  13    depicts a message timing diagram in which groups of APs transmit aggregated discovery information. The message timing diagram  1300  shows two repeating timeslots (such as timeslot TS 1   1271 , and timeslot TS 2   1272 ) which are shared by four APs (first AP  110 , second AP  120 , third AP  130  and fourth AP  140 ). In  FIG.  13   , the first AP  110  and the third AP  130  are grouped together to share TS 1 . The second AP  120  and the fourth AP  140  are grouped together to share TS 2 . However, different from  FIG.  12   , the first AP  110  and the third AP  130  may be capable of transmitting aggregating discovery information for their respective group of APs. For example, the first AP  110  and the second AP  120  could advertise the discovery information for other APs that share the timeslot for their group. 
     At the timeslot TS 1   1271 , the first AP  110  may transmit a first discovery message  1312  which includes aggregated discovery information for the first AP  110  and the third AP  130 . The third AP  130  may refrain (shown at  1332 ) from transmitting. Similarly, at timeslot TS 2   1272 , the second AP  120  may transmit a second discovery message  1322  which includes aggregated discovery information for the second AP  120  and the fourth AP  140 . The fourth AP  140  may refrain (shown at  1342 ) from transmitting. The pattern may repeat for subsequent occurrences of TS 1  and TS 2 . For example, at timeslot TS 1   1273 , the first AP  110  may transmit a third discovery message  1316  with aggregated discovery information for the first AP  110  and the third AP  130 . At timeslot TS 2   1274 , the second AP  120  may transmit a fourth discovery message  1326  with aggregated discovery information for the second AP  120  and the fourth AP  140 . By aggregating discovery information among groups of APs, it may be possible to reduce the quantity of timeslots defined for the dedicated discovery channel. As a result, the STA may receive discovery information with a shorter advertisement interval (such as advertisement interval  1318  which is equivalent to the timer period for two timeslots). 
     There may be various ways to group APs into assigned timeslots. For example, a central coordinator may assign the timeslots for use by each AP. The central coordinator also may indicate a group of APs for the timeslot. 
       FIG.  14 A  depicts a conceptual diagram of an example discovery message for transmitting discovery information. For example, the example discovery message  1401  may be sent from a first AP (or a coordinating AP) via the dedicated discovery channel. The example discovery message  1401  may include a header  1424  and a payload  1410 .In some implementations, the header  1424  may include source addresses (such as the network address of the sending AP), the length of data frame, or other frame control information. In some implementations, the header  1424  also may indicate a technology type associated with a technology-specific payload (if the payload  1410  is specific to a particular technology type or types). The payload  1410  may be used to convey the discovery information. The discovery information may be organized or formatted in a variety of ways. The discovery information may also be conveyed using technology-specific formatting associated with different technology types. For example, in some implementations, an AP can generate discovery messages that are distinctive of a certain technology. One example of a discovery message may include an enhanced beacon frame that may be used by IEEE 802.11 (similar to the beacon frames defined for IEEE 802.11ax). Another example of a discovery message may be a synchronization frame or other short frame that may be defined for other technologies (or next generation of IEEE 802.11, beyond 802.11ax). Other types of discovery messages could be used if the AP supports a different technology (different from IEEE 802.11). An example of another technology that could be used to send discovery messages might be LTE, as shown below in  FIG.  14 D . In some implementations, a combination of different types of discovery messages may be used on the dedicated discovery channel. In some implementations, the same discovery message may include signaling for more than one technology type. 
       FIG.  14 B  depicts an example message format for an example discovery message. For example, the example discovery message  1402  may be used for IEEE 802.11 devices and may be based on a previously defined beacon message that has been modified to include the discovery information in accordance with this disclosure. The example discovery message  1402  may include a header  1424 , a payload  1411 , and an optional frame check sequence (FSC)  1426 . The payload  1411  may be organized with a message format and may include discovery information elements  1432 ,  1436 , and  1438 . The discovery information elements may include, for example, an operating channel identifier and a network identifier. For example, the network identifier may be an SSID associated with a BSS using an operating channel identified by the operating channel identifier. 
       FIG.  14 C  depicts an example message format for an example discovery message and example discovery information elements. The example discovery message  1403  may include a header  1424 , a payload  1411 , and an optional frame check sequence (FSC)  1426 . In some implementations, the example discovery message  1403  may include a preamble  1422 . The preamble  1422  may be used, for example, when the dedicated discovery channel uses a listen-before-talk, contention-based access, or carrier sense access. For example, the preamble  1422  may include one or more bits to establish synchronization. In some implementations, if the dedicated discovery channel uses a scheduled timeslot for transmission, the preamble  1422  may be omitted. Similar to  FIG.  14 B , the payload  1411  may be organized with a message format and may include discovery information elements  1432 ,  1436 , and  1438 . The discovery information elements may be used to share discovery information regarding a described AP. Several examples of information elements  1460  are illustrated in  FIG.  14 C . The information elements  1460  may include an operating channel list  1462 . For example, the operating channel list  1462  may have identifiers of one or more operating channels being used by the AP. The information elements  1460  also may include network identification information  1464 . For example, the network identification information  1464  may include the SSID of a BSS on the operating channel. Optionally, the network identification information  1464  may indicate conditions regarding the BSS, such as channel utilization, the number of wireless stations associated with the BSS, link data rate, and scheduling behavior. Other examples of discovery information elements  1460  that may be included in the discovery frame  1420  may include protocol support information  1466 , AP capability information  1468 , STA requirement information  1472 , and a negotiation allowed indicator  1474 . 
       FIG.  14 D  depicts a conceptual diagram of an example discovery message with LTE signaling frames. The example discovery message  1404  may include a header  1424  and a payload  1412 . In some implementations, the header may be omitted, such as when the dedicated discovery channel utilizes only LTE signaling or if the LTE signaling occupies a dedicated time period in the dedicated discovery channel. The payload  1412  may include one or more LTE signaling frames  1450  (such as LTE signaling frames  1451 ,  1452 ,  1453 ,  1454 ,  1455 ,  1456 ). The discovery information may be included in the LTE signaling frames  1450 . In some implementations, the payload  1412  may include a combination (not shown) of both discovery information elements and LTE signaling frames. For example, if the AP supports both IEEE 802.11 and LTE, the payload  1412  may include discovery information that is encoded in both formats. 
       FIG.  15    shows a block diagram of an example electronic device for implementing aspects of this disclosure. In some implementations, the electronic device  1500  may be one of an access point (including any of the APs described herein), a station (including the STAs described herein), or other electronic systems. The electronic device  1500  can include a processor unit  1502  (possibly including multiple processors, multiple cores, multiple nodes, or implementing multi-threading, etc.). The electronic device  1500  also can include a memory unit  1506 . The memory unit  1506  may be system memory or any one or more of the below-described possible realizations of computer-readable media. The electronic device  1500  also can include a bus  1510  (such as PCI, ISA, PCI-Express, HyperTransport®, InfiniBand®, NuBus, AHB, AXI, etc.), and a network interface  1504  that can include at least one of a wireless network interface (such as a WLAN interface, a Bluetooth® interface, a WiMAX interface, a ZigBee® interface, a Wireless USB interface, etc.) and a wired network interface (such as an Ethernet interface, a powerline communication interface, etc.). In some implementations, the electronic device  1500  may support multiple network interfaces -each of which is configured to couple the electronic device  1500  to a different communication network. 
     The electronic device  1500  may include a discovery channel support unit  1562 . In some implementations, the discovery channel support unit  1562  can be distributed within the processor unit  1502 , the memory unit  1506 , and the bus  1510 . The discovery channel support unit  1562  can perform some or all of the operations described in  FIGS.  1 - 14 D  above. For example, if the electronic device  1500  is an AP, the discovery channel support unit  1562  may transmit discovery information via the dedicated discovery channel. If the electronic device  1500  is a STA, the discovery channel support unit  1562  may be configured to monitor the dedicated discovery channel and receive the discovery information from one or more APs. 
     The memory unit  1506  can include computer instructions executable by the processor unit  1502  to implement the functionality of the implementations described in  FIGS.  1 - 14 D  above. Any one of these functionalities may be partially (or entirely) implemented in hardware or on the processor unit  1502 . For example, the functionality may be implemented with an application specific integrated circuit, in logic implemented in the processor unit  1502 , in a co-processor on a peripheral device or card, etc. Further, realizations may include fewer or additional components not illustrated in  FIG.  15    (such as video cards, audio cards, additional network interfaces, peripheral devices, etc.). The processor unit  1502 , the memory unit  1506 , the network interface  1504 , and the network configurator unit  1508  are coupled to the bus  1510 . Although illustrated as being coupled to the bus  1510 , the memory unit  1506  may be coupled to the processor unit  1502 . 
       FIGS.  1 - 15    and the operations described herein are examples meant to aid in understanding example implementations and should not be used to limit the potential implementations or limit the scope of the claims. Some implementations may perform additional operations, fewer operations, operations in parallel or in a different order, and some operations differently. 
     While the aspects of the disclosure have been described in terms of various examples with their associated operations, a person skilled in the art would appreciate that a combination of operations from any number of different examples is also within the scope of the aspects of the disclosure. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a first station (STA). The first STA may receive, from a first AP, first discovery information via a dedicated discovery channel for an unlicensed frequency band. The first discovery information may include a first identifier of a first operating channel from among various operating channels within the unlicensed frequency band. The first operating channel may be utilized by the first AP to provide wireless access to a network. The first STA may associate with the first AP on the first operating channel. 
     In some implementations, receiving the discovery information may include monitoring a single channel that has been designated as the dedicated discovery channel for the unlicensed frequency band. 
     In some implementations, first STA may monitor the dedicated discovery channel for at least a time period associated with a first periodic interval. 
     In some implementations, the first periodic interval is specified by a first technology standard adopted by the first STA. 
     In some implementations, the first discovery information may further include at least one member selected from a group consisting of basic service set (BSS) information, service set identification (SSID), operating parameters for the first operating channel, wireless service capabilities of the first AP, a list of supported protocols, and a list of other channels being utilized by the first AP. 
     In some implementations, the first STA may receive, from a second AP, second discovery information via the dedicated discovery channel. The second discovery information may include a second identifier of a second operating channel being utilized by the second AP to provide wireless access to the network. The first STA may select the first AP based, at least in part, on the first discovery information and the second discovery information. 
     In some implementations, the first discovery information may further include an identifier of a second operating channel utilized by a second AP. The first STA may determine service capabilities for the first AP and the second AP. The first STA may select the first AP based, at least in part, on the first discovery information and the service capabilities. 
     In some implementations, determining the service capabilities may include at least one member selected from a group consisting of determining signal strengths for the first operating channel and the second operating channel, and determining the service capabilities based, at least in part, on operating parameters of the first AP and the second AP. The operating parameters may be included in the first discovery information. 
     In some implementations, the first discovery information may further include an indicator to indicate whether the first AP will permit a negotiation of one or more operating parameters shared between the first AP and the first STA. The first STA may negotiate, via the first operating channel, the one or more operating parameters shared between the first AP and the first STA. 
     In some implementations, the first discovery information may be included in a technology-specific payload of a message received on the dedicated discovery channel. The first STA may decode a header of the message, wherein the header indicates a technology type of the technology-specific payload. The first STA may determine whether the first STA can utilize the technology type. The first STA may decode the technology-specific payload if the first station utilizes the technology type. The first STA may disregard the technology-specific payload if the first station does not utilize the technology type. 
     In some implementations, disregarding the technology-specific payload may include entering a power saving mode for at least a remaining duration of the message. 
     In some implementations, receiving the first discovery information via the dedicated discovery channel may obviate an active scan or passive scan of one or more operating channels associated with the unlicensed frequency band. 
     Another innovative aspect of the subject matter described in this disclosure can be implemented in a coordinating AP. The coordinating AP may receive, from a first AP, first discovery information that includes a first identifier of a first operating channel from among various operating channels within an unlicensed frequency band. The first operating channel may be utilized by the first AP to provide wireless access to the first AP. The coordinating AP may receive, from a second AP, second discovery information that includes a second identifier of a second operating channel from among the various operating channels within the unlicensed frequency band. The second operating channel may be utilized by the second AP to provide wireless access to the second AP. The coordinating AP may determine aggregated discovery information based on the first discovery information and the second discovery information. The coordinating AP may transmit the aggregated discovery information via a dedicated discovery channel for the unlicensed frequency band. 
     In some implementations, the coordinating AP may be a central coordinator for allocating channels to one or more APs that utilize the unlicensed frequency band. 
     In some implementations, the first discovery information and the second discovery information may further include operating parameters associated with each of the first AP and the second AP, respectively. Determining the aggregated discovery information may comprise including at least a portion of the operating parameters in the aggregated discovery information. 
     As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c. 
     The various illustrative logics, logical blocks, modules, circuits and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor also may be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular processes and methods may be performed by circuitry that is specific to a given function. 
     In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus. 
     If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. The processes of a method or algorithm disclosed herein may be implemented in a processor-executable software module which may reside on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program from one place to another. A storage media may be any available media that may be accessed by a computer. By way of example, and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection can be properly termed a computer-readable medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray™ disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as one or any combination or set of codes and instructions on a machine readable medium and computer-readable medium, which may be incorporated into a computer program product. 
     Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. 
     Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of any device as implemented. 
     Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.