Patent Publication Number: US-2018035366-A1

Title: Signal detection verification

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims priority to and the benefit of India patent application number 201641025550 filed on Jul. 26, 2016, the entire content of which is incorporated herein by reference. 
     INTRODUCTION 
     Various aspects described herein relate to wireless communication, and more particularly but not exclusively, to verifying the efficacy of a signal (e.g., radar) detection function. 
     Dynamic Frequency Selection (DFS) specifies that Wi-Fi devices using certain 5G channels are to detect the presence of radar in the channel and stop using the channel if radar is found. However, it is possible that a Wi-Fi device could be configured to disable radar detection. For example, a software component of a Wi-Fi device could provide the radar detection function. Thus, someone could disable the radar detection function of a Wi-Fi device by modifying the software code of the Wi-Fi device. 
     SUMMARY 
     The following presents a simplified summary of some aspects of the disclosure to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present various concepts of some aspects of the disclosure in a simplified form as a prelude to the more detailed description that is presented later. 
     In one aspect, the disclosure provides an apparatus configured for communication that includes a processing system. The processing system is configured to: determine whether radar detection is enabled, and disable communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. 
     Another aspect of the disclosure provides a method for communication including: determining whether radar detection is enabled; and disabling communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. 
     Another aspect of the disclosure provides an apparatus configured for communication. The apparatus including: means for determining whether radar detection is enabled; and means for disabling communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. 
     Another aspect of the disclosure provides a computer-readable medium (e.g., a non-transitory computer-readable medium) storing computer-executable code, including code to: determine whether radar detection is enabled, and disable communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. 
     In one aspect, the disclosure provides an access point configured for communication that includes a processing system and a transceiver coupled to the processing system. The processing system is configured to: determine whether radar detection is enabled, and disable communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. The transceiver is configured to communicate data on the at least one wireless communication channel. 
     In one aspect, the disclosure provides an access terminal configured for communication that includes a processing system and a user interface coupled to the processing system. The processing system is configured to: determine whether radar detection is enabled, and disable communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. The user interface is configured to provide data for the communication on the at least one wireless communication channel 
     These and other aspects of the disclosure will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and implementations of the disclosure will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific implementations of the disclosure in conjunction with the accompanying figures. While features of the disclosure may be discussed relative to certain implementations and figures below, all implementations of the disclosure can include one or more of the advantageous features discussed herein. In other words, while one or more implementations may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various implementations of the disclosure discussed herein. In similar fashion, while certain implementations may be discussed below as device, system, or method implementations it should be understood that such implementations can be implemented in various devices, systems, and methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are presented to aid in the description of aspects of the disclosure and are provided solely for illustration of the aspects and not limitations thereof. 
         FIG. 1  is an example of a wireless communication system in which aspects of the present disclosure may be employed. 
         FIG. 2  is a layer diagram for DFS in accordance with some aspects of the disclosure. 
         FIG. 3  is a device architecture in accordance with some aspects of the disclosure. 
         FIG. 4  is a DFS flow diagram in accordance with some aspects of the disclosure. 
         FIG. 5  is another DFS flow diagram in accordance with some aspects of the disclosure. 
         FIG. 6  is a radar pattern table in accordance with some aspects of the disclosure. 
         FIG. 7  is an example of a wireless communication system in which aspects of the present disclosure may be employed. 
         FIG. 8  is a functional block diagram of an example apparatus that may be employed within a wireless communication system in accordance with some aspects of the disclosure. 
         FIG. 9  is a functional block diagram of example components that may be utilized in the apparatus of  FIG. 8  to transmit wireless communication. 
         FIG. 10  is a functional block diagram of example components that may be utilized in the apparatus of  FIG. 8  to receive wireless communication. 
         FIG. 11  is a functional block diagram of an example apparatus in accordance with some aspects of the disclosure. 
         FIG. 12  is a flow diagram of an example signal detection verification process in accordance with some aspects of the disclosure. 
         FIG. 13  is a flow diagram of an example signal detection verification process that uses a data pattern in accordance with some aspects of the disclosure. 
         FIG. 14  is a flow diagram of an example process for triggering signal detection verification in accordance with some aspects of the disclosure. 
         FIG. 15  is a simplified block diagram of several sample aspects of an apparatus configured with functionality in accordance with some aspects of the disclosure. 
         FIG. 16  is a simplified block diagram of several sample aspects of a memory configured with code in accordance with some aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects of the disclosure are described below. It should be apparent that the teachings herein may be embodied in a wide variety of forms and that any specific structure, function, or both being disclosed herein is merely representative. Based on the teachings herein one skilled in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, such an apparatus may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. Furthermore, an aspect may comprise at least one element of a claim. As an example of the above, in some aspects, a method of communication includes determining whether radar detection is enabled and disabling communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. 
     The disclosure relates in some aspects to determining whether a radar detection function is properly detecting for radar. If the radar detection function is not functioning as desired, communication on at least one wireless communication channel may be disabled. For example, communication on a channel that is subject to dynamic frequency selection (DFS) may be disabled to ensure that a device is not interfering with radar operations. 
       FIG. 1  illustrates a wireless communication system  100  that includes an access point (AP)  110  and several access terminal terminals (ATs)  120 . The AP  110  is connected to a system controller  130  to enable communication to other APs and/or other communication systems. It is possible that some of the wireless communication channels that the AP  110  and the ATs  120  use for communication may be used for radar applications (e.g., weather radar). A regulatory body (e.g., the FCC) may require that the wireless system  100  back off of a communication channel if radar signals  140  are detected on that channel. 
     During normal operation of a wireless access point (AP) in a radar enabled channel, the hardware of the AP scans for potential radar pulses. Firmware of the AP passes the potential radar information to the host of the AP for processing to check against known radar types. If there is a match, the AP moves to another channel and places the channel on a list of channels that must not be used for thirty minutes. 
     A typical wireless access point (AP) has hardware (HW), firmware (FW), and host software components. In general, AP software may be upgradable to fix bugs or add features and the AP Host software image can be updated by updating the flash memory image. 
     It is desirable for end-customers to retain the ability to update their AP software from sources other than the original equipment manufacturer (OEM) because they may provide additional features, better security, or the OEM may no longer support the equipment directly. Whereas OEM updates usually remain compliant with all regulatory requirements, 3rd party updates may allow end-users to disable and/or bypass regulatory features such as channel selection, power restrictions, or DFS. 
     For example, open source code for AP host software may be available for download and modification of the source. End users can use a web-based user interface (UI) to configure an AP and shell/command line tools shipped with the image may be used to configure the AP, fine tune parameters and debug the AP. Thus, it may be possible for anyone to modify the source and disable or bypass radar detection in the AP host software. For example, a user could disable and/or bypass regulatory requirements related to DFS, disable radar detection, and ignore rules regarding a Non-Occupancy List (NOL) after radar detection in a channel. 
     The disclosure relates in some aspects to using firmware that executes on the radio hardware subsystem to determine whether radar detection is enabled on the AP host during operation. As firmware is typically proprietary and its source code not available to the general public, it is much less likely that firmware could be modified to bypass radar detection. It is also possible for the radio system to authenticate the firmware by checking that it has a known digital signature before execution and reject it if it does not. Thus, compliance of a device can be more effectively assured. 
     The disclosure relates in some aspects to firmware that sends “spoofed” data that resembles real radar data to the host. The host will match the data with known radar patterns and send a notification of successful radar detection to the firmware. If the firmware does not receive any notification from the host, the firmware concludes that the host software does not meet regulatory requirements for DFS. The firmware will then prevent the host from selecting any of the channels that require radar detection. Thus, in some aspects, hardware and/or firmware may be used to enforce regulatory DFS compliance in user modified or factory certified code, detect if radar detection function is enabled in the AP host software, and detect if NOL compliance is maintained. 
     Referring to  FIG. 2 , there are various points in a set of DFS layers  200  that are susceptible to tampering. In this example, the DFS layers  200  include a channel switch announcement layer  202 , a random channel selection layer  204 , a channel marking layer  206 , a non-occupancy list layer  208 , a filter match layer  210 , a radar pulse (e.g., type length value) processing layer  212 , an offload layer  214 , a firmware layer  216 , and a hardware layer  218 . 
     Examples of the points in the DFS layers  200  that could be tampered with are indicate in  FIG. 2 . Firmware could be modified to ignore randomization,  220 , ignore channel marking  222 , ignore the NOL  224 , ignore a filter match  226 , ignore radar  228 , disable hardware  230 , or any combination thereof. 
     It is desirable for firmware to detect tampering across all layers. To this end, firmware sends a known radar data pattern (spoofed radar) to the host. The sending of this pattern may be triggered or conditioned in different ways in different scenarios. For example, the pattern may be sent: if (or when) Wi-Fi is enabled, if (or when) a DFS channel is selected for the first time, randomly, on-demand, if (or when) a DFS channel is in use, or based on some other condition. The data pattern travels through all the DFS layers  200  and should result in positive detection. Positive detection is reported back to the firmware to confirm all radar detection pieces are functional. Failure to indicate detection means radar detection is not working properly in the host, and the firmware will disregard any host request to select any of the DFS channels. For example, the firmware may reject or ignore a request from the host to select one or more channels (e.g., thereby preventing the device from accessing all of the DFS channel or, in some cases, any of the channels). 
     Referring to  FIG. 3 , a device  300  (e.g., a Wi-Fi device) may contain memory and processing capabilities  302  that run radio firmware  304  on radio hardware  306  and are separate from a host operating system (OS)  308  running host software. In accordance with the teachings herein, the “radio firmware” can run regulatory checks to confirm that the host software is operating in compliance with FCC rules. In particular, the “radio firmware” can verify whether a radar detection function of the host software is operating properly. 
       FIG. 4  illustrates an example of a conventional operation for detecting radar. At some point in time, a host  402  (e.g., host software) sends a virtual device (VDEV) start request (VDEV_START_REQ) message  406  to firmware  404  (e.g., radio firmware). The firmware  404  sends a VDEV start response (VDEV_START_RESP) message  408  to the host  402  (e.g., after checking the NOL  410 ). The firmware  404  then sends potential radar pulse information to the host  402  (e.g., to the host software) via messages  412 . Based on this information, the host  402  determines whether the characteristics of the information match the expected characteristics associated with radar. If there is a match, the host  402  informs the firmware that there is radar in the channel of interest (e.g., the current channel) by sending a radar match message  416  to the firmware  404 . 
     A device may maintain a NOL to indicate which DFS channels are currently unavailable. In some implementations, the NOL is managed by the host software. Thus, in this case, the host software updates the NOL in the event communication is not allowed (e.g., due to presence of radar on a channel or a refusal of the firmware to allow communication on a channel). 
     In other implementations, the firmware manages the NOL (e.g., as shown in  FIG. 4 ). In this case, the firmware will update the NOL  418  (e.g., place channels on the NOL) if a radar event is detected by the host, provide the host with an indication the change in the NOL via an NOL update message  420 , and reject any request to use channels on the NOL. 
       FIG. 5  illustrates an example of a spoof operation  500  for radar detection in accordance with the teachings herein. At some point in time, a host  502  (e.g., host software) sends a virtual device (VDEV) start request (VDEV_START_REQ) message  506  to firmware  504  (e.g., radio firmware). The firmware  504  sends a VDEV start response (VDEV_START_RESP) message  508  to the host  502  (e.g., to the host software). 
     The firmware  504  then sends spoofed data  510  (e.g., spoof radar pulse information) to the host  502  via messages  412 . As indicated, real hardware detection may be disabled  510  while spoofed data is sent. Real hardware detection may then be enabled 514 after all of the spoofed data has been sent. 
     The host  502  is supposed to determine whether the characteristics of the received information match the expected characteristics associated with radar. If the host  502  reports a radar match (e.g., a radar match message  516 ), the firmware  504  may be assured that the host  502  is properly checking for the presence of radar. In this case, if applicable, the firmware updates the NOL to indicate that the channel is unavailable. The firmware may choose not to update the NOL if the detection was due to spoofed data. 
     Otherwise (e.g., if the firmware does not receive the radar match message  516  from the host  592 ), the firmware  504  may update  518  the NOL to indicate that that the channel (and potentially other channels) is not available because the host cannot be trusted to perform the radar detection function. 
     Various messages (e.g., between the firmware and the host) may be employed in different implementations. Several example wireless module interface (WMI) messages are set forth below. 
     WMI_RADAR_FOUND message. Host sends this message to the firmware to indicate that radar was found in the current channel and provides information regarding the characteristics of the radar found. This information may include, for example, frequency (range) where the radar was found, timing (e.g., the time at which a pulse was detected, pulse interval, pulse width, and pulse frequencies. Upon receiving such a message in response to spoof data, the firmware can determine whether the host is adequately testing the data being sent to the host for the presence of radar. In this way, non-operational software or software that was modified to try to trick the firmware (e.g., by acting like radar detection is still functioning) may be detected. 
     WMI_UPDATE_NOL message. This message (e.g., the NOL update message  520 ) may be used in implementations where the firmware manages the NOL. The firmware sends this message to the host to indicate a change to NOL. If (e.g., when) radar is found in a channel, the channel is added to NOL. After 30 minutes (or some other designated amount of time), the channel is removed from NOL. This timer may be maintained in the firmware. The firmware may choose not to add a channel to the NOL if the radar found by the host was due to spoofed data. In the event the firmware removes a channel from the NOL and reports this NOL update, the host may thereby determine  522  that the channel is now available for use. 
     VDEV_START_RESP message. This virtual device (VDEV) message is a response to a request to commence radar detection. This message may include a field to indicate failure to set a channel if the channel is listed in the NOL. 
       FIG. 6  depicts a table of information  600  that may be used to generate a spoof data pattern. The information is indexed according the different characteristics of the data and corresponding regulatory domains. In some aspects, the spoof data pattern (as with an actual data pattern) may include, for example, information regarding pulse timing (e.g., the time at which a pulse was detected, a pulse interval (e.g., minimum and maximum pulse repetition intervals, PRIs), a pulse width (e.g., minimum and maximum pulse durations in microseconds), and pulse frequencies (e.g., RF band). Here, selection of a radar pattern to spoof may include, for example, selecting a random index, a pulse repetition index (PRI), a duration, and an offset from the table and populating type length values (TLVs) in the radar data pattern. In some implementations, spoofed data is generated from a captured template (e.g., from data derived from real radar signals). Also, the content of the data pattern can vary/change over time. 
     Example Wireless Communication System 
     The teachings herein may be implemented using various wireless technologies and/or various spectra. Wireless network technologies may include various types of wireless local area networks (WLANs). A WLAN may be used to interconnect nearby devices together, employing widely used networking protocols. The various aspects described herein may apply to any communication standard, such as Wi-Fi or, more generally, any member of the IEEE 802.11 family of wireless protocols. 
     In some aspects, wireless signals may be transmitted according to an 802.11 protocol using orthogonal frequency-division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communication, a combination of OFDM and DSSS communication, or other schemes. 
     Certain of the devices described herein may further implement Multiple Input Multiple Output (MIMO) technology and be implemented as part of an 802.11 protocol. A MIMO system employs multiple (N t ) transmit antennas and multiple (N r ) receive antennas for data transmission. A MIMO channel formed by the N t  transmit and N r  receive antennas may be decomposed into N s  independent channels, which are also referred to as spatial channels or streams, where N s ≦min{N t , N r }. Each of the N s  independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. 
     In some implementations, a WLAN includes various devices that access the wireless network. For example, there may be two types of devices: access points (“APs”) and clients (also referred to as stations, or “STAs”). In general, an AP serves as a hub or base station for the WLAN and a STA serves as a user of the WLAN. For example, a STA may be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In an example, a STA connects to an AP via a Wi-Fi (e.g., IEEE 802.11 protocol) compliant wireless link to obtain general connectivity to the Internet or to other wide area networks. In some implementations, a STA may also be used as an AP. 
     An access point (“AP”) may also comprise, be implemented as, or known as a Transmit Receive Point (TRP), a NodeB, Radio Network Controller (“RNC”), eNodeB, Base Station Controller (“BSC”), Base Transceiver Station (“BTS”), Base Station (“BS”), Transceiver Function (“TF”), Radio Router, Radio Transceiver, or some other terminology. 
     A station “STA” may also comprise, be implemented as, or known as an access terminal (“AT”), a subscriber station, a subscriber unit, a mobile station, a remote station, a remote terminal, a user terminal, a user agent, a user device, user equipment, or some other terminology. In some implementations, an access terminal may comprise a cellular telephone, a cordless telephone, a Session Initiation Protocol (“SIP”) phone, a wireless local loop (“WLL”) station, a personal digital assistant (“PDA”), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music or video device, or a satellite radio), a gaming device or system, a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium. 
       FIG. 7  illustrates an example of a wireless communication system  700  in which aspects of the present disclosure may be employed. The wireless communication system  700  may operate pursuant to a wireless standard, for example the 802.11 standard. The wireless communication system  700  may include an AP  704 , which communicates with STAs  706   a ,  706   b ,  706   c ,  706   d ,  706   e , and  706   f  (collectively STAs  706 ). 
     STAs  706   e  and  706   f  may have difficulty communicating with the AP  704  or may be out of range and unable to communicate with the AP  704 . As such, another STA  706   d  may be configured as a relay device (e.g., a device comprising STA and AP functionality) that relays communication between the AP  704  and the STAs  706   e  and  706   f.    
     A variety of processes and methods may be used for transmissions in the wireless communication system  700  between the AP  704  and the STAs  706 . For example, signals may be sent and received between the AP  704  and the STAs  706  in accordance with OFDM/OFDMA techniques. If this is the case, the wireless communication system  700  may be referred to as an OFDM/OFDMA system. Alternatively, signals may be sent and received between the AP  704  and the STAs  706  in accordance with CDMA techniques. If this is the case, the wireless communication system  700  may be referred to as a CDMA system. 
     A communication link that facilitates transmission from the AP  704  to one or more of the STAs  706  may be referred to as a downlink (DL)  708 , and a communication link that facilitates transmission from one or more of the STAs  706  to the AP  704  may be referred to as an uplink (UL)  710 . Alternatively, a downlink  708  may be referred to as a forward link or a forward channel, and an uplink  710  may be referred to as a reverse link or a reverse channel. 
     The AP  704  may act as a base station and provide wireless communication coverage in a basic service area (BSA)  702 . The AP  704  along with the STAs  706  associated with the AP  704  and that use the AP  704  for communication may be referred to as a basic service set (BSS). 
     Access points may thus be deployed in a communication network to provide access to one or more services (e.g., network connectivity) for one or more access terminals that may be installed within or that may roam throughout a coverage area of the network. For example, at various points in time an access terminal may connect to the AP  704  or to some other access point in the network (not shown). 
     Each of the access points may communicate with one or more network entities (represented, for convenience, by network entities  712  in  FIG. 7 ), including each other, to facilitate wide area network connectivity. A network entity may take various forms such as, for example, one or more radio and/or core network entities. Thus, in various implementations the network entities  712  may represent functionality such as at least one of: network management (e.g., via an authentication, authorization, and accounting (AAA) server), session management, mobility management, gateway functions, interworking functions, database functionality, or some other suitable network functionality. Two or more of such network entities may be co-located and/or two or more of such network entities may be distributed throughout a network. 
     It should be noted that in some implementations the wireless communication system  700  might not have a central AP  704 , but rather may function as a peer-to-peer network between the STAs  706 . Accordingly, the functions of the AP  704  described herein may alternatively be performed by one or more of the STAs  706 . Also, as mentioned above, a relay may incorporate at least some of the functionality of an AP and a STA. 
       FIG. 8  illustrates various components that may be utilized in an apparatus  802  (e.g., a wireless device) that may be employed within the wireless communication system  700 . The apparatus  802  is an example of a device that may be configured to implement the various methods described herein. For example, the apparatus  802  may comprise the AP  704 , a relay (e.g., the STA  706   d ), or one of the STAs  706  of  FIG. 7 . 
     The apparatus  802  may include a processing system  804  that controls operation of the apparatus  802 . The processing system  804  may also be referred to as a central processing unit (CPU). A memory component  806  (e.g., including a memory device), which may include both read-only memory (ROM) and random access memory (RAM), provides instructions and data to the processing system  804 . A portion of the memory component  806  may also include non-volatile random access memory (NVRAM). The processing system  804  typically performs logical and arithmetic operations based on program instructions stored within the memory component  806 . The instructions in the memory component  806  may be executable to implement the methods described herein. 
     If the apparatus  802  is implemented or used as a transmitting node, the processing system  804  may be configured to select one of a plurality of media access control (MAC) header types, and to generate a packet having that MAC header type. For example, the processing system  804  may be configured to generate a packet comprising a MAC header and a payload and to determine what type of MAC header to use. 
     If the apparatus  802  is implemented or used as a receiving node, the processing system  804  may be configured to process packets of a plurality of different MAC header types. For example, the processing system  804  may be configured to determine the type of MAC header used in a packet and process the packet and/or fields of the MAC header. 
     The processing system  804  may comprise or be a component of a larger processing system implemented with one or more processors. The one or more processors may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that can perform calculations or other manipulations of information. 
     The processing system may also include machine-readable media for storing software. Software shall be construed broadly to mean any type of instructions, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Instructions may include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code). The instructions, when executed by the one or more processors, cause the processing system to perform the various functions described herein. 
     The apparatus  802  may also include a housing  808  that may include a transmitter  810  and a receiver  812  to allow transmission and reception of data between the apparatus  802  and a remote location. The transmitter  810  and receiver  812  may be combined into single communication device (e.g., a transceiver  814 ). An antenna  816  may be attached to the housing  808  and electrically coupled to the transceiver  814 . The apparatus  802  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas. A transmitter  810  and a receiver  812  may comprise an integrated device (e.g., embodied as a transmitter circuit and a receiver circuit of a single communication device) in some implementations, may comprise a separate transmitter device and a separate receiver device in some implementations, or may be embodied in other ways in other implementations. 
     The transmitter  810  may be configured to wirelessly transmit packets having different MAC header types. For example, the transmitter  810  may be configured to transmit packets with different types of headers generated by the processing system  804 , discussed above. 
     The receiver  812  may be configured to wirelessly receive packets having different MAC header type. In some aspects, the receiver  812  is configured to detect a type of a MAC header used and process the packet accordingly. 
     The receiver  812  may be used to detect and quantify the level of signals received by the transceiver  814 . The receiver  812  may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The apparatus  802  may also include a digital signal processor (DSP)  820  for use in processing signals. The DSP  820  may be configured to generate a data unit for transmission. In some aspects, the data unit may comprise a physical layer data unit (PPDU). In some aspects, the PPDU is referred to as a packet. 
     The apparatus  802  may further comprise a user interface  822  in some aspects. The user interface  822  may comprise a keypad, a microphone, a speaker, and/or a display. The user interface  822  may include any element or component that conveys information to a user of the apparatus  802  and/or receives input from the user. 
     The various components of the apparatus  802  may be coupled together by a bus system  826 . The bus system  826  may include a data bus, for example, as well as a power bus, a control signal bus, and a status signal bus in addition to the data bus. Those of skill in the art will appreciate the components of the apparatus  802  may be coupled together or accept or provide inputs to each other using some other mechanism. 
     Although a number of separate components are illustrated in  FIG. 8 , one or more of the components may be combined or commonly implemented. For example, the processing system  804  may be used to implement not only the functionality described above with respect to the processing system  804 , but also to implement the functionality described above with respect to the transceiver  814  and/or the DSP  820 . Further, each of the components illustrated in  FIG. 8  may be implemented using a plurality of separate elements. Furthermore, the processing system  804  may be used to implement any of the components, modules, circuits, or the like described below, or each may be implemented using a plurality of separate elements. 
     For ease of reference, if the apparatus  802  is configured as a transmitting node, it is hereinafter referred to as an apparatus  802   t . Similarly, if the apparatus  802  is configured as a receiving node, it is hereinafter referred to as an apparatus  802   r . A device in the wireless communication system  700  may implement only functionality of a transmitting node, only functionality of a receiving node, or functionality of both a transmitting node and a receive node. 
     As discussed above, the apparatus  802  may comprise an AP  704  or a STA  706 , and may be used to transmit and/or receive communication having a plurality of MAC header types. 
     The components of  FIG. 8  may be implemented in various ways. In some implementations, the components of  FIG. 8  may be implemented in one or more circuits such as, for example, one or more processors and/or one or more ASICs (which may include one or more processors). Here, each circuit may use and/or incorporate at least one memory component for storing information or executable code used by the circuit to provide this functionality. For example, some or all of the functionality represented by blocks of  FIG. 8  may be implemented by processor and memory component(s) of the apparatus (e.g., by execution of appropriate code and/or by appropriate configuration of processor components). It should be appreciated that these components may be implemented in different types of apparatuses in different implementations (e.g., in an ASIC, in a system-on-a-chip (SoC), etc.). 
     As discussed above, the apparatus  802  may comprise an AP  704  or a STA  706 , a relay, or some other type of apparatus, and may be used to transmit and/or receive communication.  FIG. 9  illustrates various components that may be utilized in the apparatus  802   t  to transmit wireless communication. The components illustrated in  FIG. 9  may be used, for example, to transmit OFDM communication. In some aspects, the components illustrated in  FIG. 9  are used to generate and transmit packets to be sent over a bandwidth of less than or equal to 1 MHz. 
     The apparatus  802   t  of  FIG. 9  may comprise a modulator  902  configured to modulate bits for transmission. For example, the modulator  902  may determine a plurality of symbols from bits received from the processing system  804  ( FIG. 8 ) or the user interface  822  ( FIG. 8 ), for example by mapping bits to a plurality of symbols according to a constellation. The bits may correspond to user data or to control information. In some aspects, the bits are received in codewords. In one aspect, the modulator  902  may comprise a QAM (quadrature amplitude modulation) modulator, for example, a 16-QAM modulator or a 64-QAM modulator. In other aspects, the modulator  902  may comprise a binary phase-shift keying (BPSK) modulator, a quadrature phase-shift keying (QPSK) modulator, or an 8-PSK modulator. 
     The apparatus  802   t  may further comprise a transform module  904  configured to convert symbols or otherwise modulated bits from the modulator  902  into a time domain. In  FIG. 9 , the transform module  904  is illustrated as being implemented by an inverse fast Fourier transform (IFFT) module. In some implementations, there may be multiple transform modules (not shown) that transform units of data of different sizes. In some implementations, the transform module  904  may be itself configured to transform units of data of different sizes. For example, the transform module  904  may be configured with a plurality of modes, and may use a different number of points to convert the symbols in each mode. For example, the IFFT may have a mode where 32 points are used to convert symbols being transmitted over 32 tones (i.e., subcarriers) into a time domain, and a mode where 64 points are used to convert symbols being transmitted over 64 tones into a time domain. The number of points used by the transform module  904  may be referred to as the size of the transform module  904 . 
     In  FIG. 9 , the modulator  902  and the transform module  904  are illustrated as being implemented in the DSP  920 . In some aspects, however, one or both of the modulator  902  and the transform module  904  are implemented in the processing system  804  or in another element of the apparatus  802   t  (e.g., see description above with reference to  FIG. 8 ). 
     As discussed above, the DSP  920  may be configured to generate a data unit for transmission. In some aspects, the modulator  902  and the transform module  904  may be configured to generate a data unit comprising a plurality of fields including control information and a plurality of data symbols. 
     Returning to the description of  FIG. 9 , the apparatus  802   t  may further comprise a digital to analog converter  906  configured to convert the output of the transform module into an analog signal. For example, the time-domain output of the transform module  904  may be converted to a baseband OFDM signal by the digital to analog converter  906 . The digital to analog converter  906  may be implemented in the processing system  804  or in another element of the apparatus  802  of  FIG. 8 . In some aspects, the digital to analog converter  906  is implemented in the transceiver  814  ( FIG. 8 ) or in a data transmit processor. 
     The analog signal may be wirelessly transmitted by the transmitter  910 . The analog signal may be further processed before being transmitted by the transmitter  910 , for example by being filtered or by being upconverted to an intermediate or carrier frequency. In the aspect illustrated in  FIG. 9 , the transmitter  910  includes a transmit amplifier  908 . Prior to being transmitted, the analog signal may be amplified by the transmit amplifier  908 . In some aspects, the amplifier  908  comprises a low noise amplifier (LNA). 
     The transmitter  910  is configured to transmit one or more packets or data units in a wireless signal based on the analog signal. The data units may be generated using the processing system  804  ( FIG. 8 ) and/or the DSP  920 , for example using the modulator  902  and the transform module  904  as discussed above. Data units that may be generated and transmitted as discussed above are described in additional detail below. 
       FIG. 10  illustrates various components that may be utilized in the apparatus  802  of  FIG. 8  to receive wireless communication. The components illustrated in  FIG. 10  may be used, for example, to receive OFDM communication. For example, the components illustrated in  FIG. 10  may be used to receive data units transmitted by the components discussed above with respect to  FIG. 9 . 
     The receiver  1012  of apparatus  802   r  is configured to receive one or more packets or data units in a wireless signal. Data units that may be received and decoded or otherwise processed as discussed below. 
     In the aspect illustrated in  FIG. 10 , the receiver  1012  includes a receive amplifier  1001 . The receive amplifier  1001  may be configured to amplify the wireless signal received by the receiver  1012 . In some aspects, the receiver  1012  is configured to adjust the gain of the receive amplifier  1001  using an automatic gain control (AGC) procedure. In some aspects, the automatic gain control uses information in one or more received training fields, such as a received short training field (STF) for example, to adjust the gain. Those having ordinary skill in the art will understand methods for performing AGC. In some aspects, the amplifier  1001  comprises an LNA. 
     The apparatus  802   r  may comprise an analog to digital converter  1010  configured to convert the amplified wireless signal from the receiver  1012  into a digital representation thereof. Further to being amplified, the wireless signal may be processed before being converted by the analog to digital converter  1010 , for example by being filtered or by being downconverted to an intermediate or baseband frequency. The analog to digital converter  1010  may be implemented in the processing system  804  ( FIG. 8 ) or in another element of the apparatus  802   r . In some aspects, the analog to digital converter  1010  is implemented in the transceiver  814  ( FIG. 8 ) or in a data receive processor. 
     The apparatus  802   r  may further comprise a transform module  1004  configured to convert the representation of the wireless signal into a frequency spectrum. In  FIG. 10 , the transform module  1004  is illustrated as being implemented by a fast Fourier transform (FFT) module. In some aspects, the transform module may identify a symbol for each point that it uses. As described above with reference to  FIG. 9 , the transform module  1004  may be configured with a plurality of modes, and may use a different number of points to convert the signal in each mode. The number of points used by the transform module  1004  may be referred to as the size of the transform module  1004 . In some aspects, the transform module  1004  may identify a symbol for each point that it uses. 
     The apparatus  802   r  may further comprise a channel estimator and equalizer  1005  configured to form an estimate of the channel over which the data unit is received, and to remove certain effects of the channel based on the channel estimate. For example, the channel estimator and equalizer  1005  may be configured to approximate a function of the channel, and the channel equalizer may be configured to apply an inverse of that function to the data in the frequency spectrum. 
     The apparatus  802   r  may further comprise a demodulator  1006  configured to demodulate the equalized data. For example, the demodulator  1006  may determine a plurality of bits from symbols output by the transform module  1004  and the channel estimator and equalizer  1005 , for example by reversing a mapping of bits to a symbol in a constellation. The bits may be processed or evaluated by the processing system  804  ( FIG. 8 ), or used to display or otherwise output information to the user interface  822  ( FIG. 8 ). In this way, data and/or information may be decoded. In some aspects, the bits correspond to codewords. In one aspect, the demodulator  1006  comprises a QAM (quadrature amplitude modulation) demodulator, for example an 8-QAM demodulator or a 64-QAM demodulator. In other aspects, the demodulator  1006  comprises a binary phase-shift keying (BPSK) demodulator or a quadrature phase-shift keying (QPSK) demodulator. 
     In  FIG. 10 , the transform module  1004 , the channel estimator and equalizer  1005 , and the demodulator  1006  are illustrated as being implemented in the DSP  1020 . In some aspects, however, one or more of the transform module  1004 , the channel estimator and equalizer  1005 , and the demodulator  1006  are implemented in the processing system  804  ( FIG. 8 ) or in another element of the apparatus  802  ( FIG. 8 ). 
     As discussed above, the wireless signal received at the receiver  812  comprises one or more data units. Using the functions or components described above, the data units or data symbols therein may be decoded evaluated or otherwise evaluated or processed. For example, the processing system  804  ( FIG. 8 ) and/or the DSP  1020  may be used to decode data symbols in the data units using the transform module  1004 , the channel estimator and equalizer  1005 , and the demodulator  1006 . 
     Data units exchanged by the AP  704  and the STA  706  may include control information or data, as discussed above. At the physical (PHY) layer, these data units may be referred to as physical layer protocol data units (PPDUs). In some aspects, a PPDU may be referred to as a packet or physical layer packet. Each PPDU may comprise a preamble and a payload. The preamble may include training fields and a SIG field. The payload may comprise a Media Access Control (MAC) header or data for other layers, and/or user data, for example. The payload may be transmitted using one or more data symbols. The systems, methods, and devices herein may utilize data units with training fields whose peak-to-power ratio has been minimized. 
     The apparatus  802   t  shown in  FIG. 9  is an example of a single transmit chain used for transmitting via an antenna. The apparatus  802   r  shown in  FIG. 10  is an example of a single receive chain used for receiving via an antenna. In some implementations, the apparatus  802   t  or  802   r  may implement a portion of a MIMO system using multiple antennas to simultaneously transmit data. 
     The wireless communication system  700  may employ methods to allow efficient access of the wireless medium based on unpredictable data transmissions while avoiding collisions. As such, in accordance with various aspects, the wireless communication system  700  performs carrier sense multiple access/collision avoidance (CSMA/CA) that may be referred to as the Distributed Coordination Function (DCF). More generally, an apparatus  802  having data for transmission senses the wireless medium to determine if the channel is already occupied. If the apparatus  802  senses the channel is idle, then the apparatus  802  transmits prepared data. Otherwise, the apparatus  802  may defer for some period before determining again whether or not the wireless medium is free for transmission. A method for performing CSMA may employ various gaps between consecutive transmissions to avoid collisions. In an aspect, transmissions may be referred to as frames and a gap between frames is referred to as an Interframe Spacing (IFS). Frames may be any one of user data, control frames, management frames, and the like. 
     IFS time durations may vary depending on the type of time gap provided. Some examples of IFS include a Short Interframe Spacing (SIFS), a Point Interframe Spacing (PIFS), and a DCF Interframe Spacing (DIFS) where SIFS is shorter than PIFS, which is shorter than DIFS. Transmissions following a shorter time duration will have a higher priority than one that must wait longer before attempting to access the channel. 
     A wireless apparatus may include various components that perform functions based on signals that are transmitted by or received at the wireless apparatus. For example, in some implementations a wireless apparatus comprises a user interface configured to output an indication based on a received signal as taught herein. 
     A wireless apparatus as taught herein may communicate via one or more wireless communication links that are based on or otherwise support any suitable wireless communication technology. For example, in some aspects a wireless apparatus may associate with a network such as a local area network (e.g., a Wi-Fi network) or a wide area network. To this end, a wireless apparatus may support or otherwise use one or more of a variety of wireless communication technologies, protocols, or standards such as, for example, Wi-Fi, WiMAX, CDMA, TDMA, OFDM, and OFDMA. Also, a wireless apparatus may support or otherwise use one or more of a variety of corresponding modulation or multiplexing schemes. A wireless apparatus may thus include appropriate components (e.g., air interfaces) to establish and communicate via one or more wireless communication links using the above or other wireless communication technologies. For example, a device may comprise a wireless transceiver with associated transmitter and receiver components that may include various components (e.g., signal generators and signal processors) that facilitate communication over a wireless medium. 
     The teachings herein may be incorporated into (e.g., implemented within or performed by) a variety of apparatuses (e.g., nodes). In some aspects, an apparatus (e.g., a wireless apparatus) implemented in accordance with the teachings herein may comprise an access point, a relay, or an access terminal. 
     An access terminal may comprise, be implemented as, or known as user equipment, a subscriber station, a subscriber unit, a mobile station, a mobile, a mobile node, a remote station, a remote terminal, a user terminal, a user agent, a user device, or some other terminology. In some implementations, an access terminal may comprise a cellular telephone, a cordless telephone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, or some other suitable processing device connected to a wireless modem. Accordingly, one or more aspects taught herein may be incorporated into a phone (e.g., a cellular phone or smart phone), a computer (e.g., a laptop), a portable communication device, a portable computing device (e.g., a personal data assistant), an entertainment device (e.g., a music device, a video device, or a satellite radio), a global positioning system device, or any other suitable device that is configured to communicate via a wireless medium. 
     An access point may comprise, be implemented as, or known as a NodeB, an eNodeB, a radio network controller (RNC), a base station (BS), a radio base station (RBS), a base station controller (BSC), a base transceiver station (BTS), a transceiver function (TF), a radio transceiver, a radio router, a basic service set (BSS), an extended service set (ESS), a macro cell, a macro node, a Home eNB (HeNB), a femto cell, a femto node, a pico node, or some other similar terminology. 
     A relay may comprise, be implemented as, or known as a relay node, a relay device, a relay station, a relay apparatus, or some other similar terminology. As discussed above, in some aspects, a relay may comprise some access terminal functionality and some access point functionality. 
     In some aspects, a wireless apparatus comprises an access device (e.g., an access point) for a communication system. Such an access device provides, for example, connectivity to another network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link. Accordingly, the access device enables another device (e.g., a wireless station) to access the other network or some other functionality. In addition, it should be appreciated that one or both of the devices may be portable or, in some cases, relatively non-portable. Also, it should be appreciated that a wireless apparatus also may be capable of transmitting and/or receiving information in a non-wireless manner (e.g., via a wired connection) via an appropriate communication interface. 
     The teachings herein may be incorporated into various types of communication systems and/or system components. In some aspects, the teachings herein may be employed in a multiple-access system capable of supporting communication with multiple users by sharing the available system resources (e.g., by specifying one or more of bandwidth, transmit power, coding, interleaving, and so on). For example, the teachings herein may be applied to any one or combinations of the following technologies: Code Division Multiple Access (CDMA) systems, Multiple-Carrier CDMA (MCCDMA), Wideband CDMA (W-CDMA), High-Speed Packet Access (HSPA, HSPA+) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Single-Carrier FDMA (SC-FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, or other multiple access techniques. A wireless communication system employing the teachings herein may be designed to implement one or more standards, such as IS-95, cdma2000, IS-856, W-CDMA, TDSCDMA, and other standards. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, or some other technology. UTRA includes W-CDMA and Low Chip Rate (LCR). The cdma2000 technology covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communication (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM are part of Universal Mobile Telecommunication System (UMTS). The teachings herein may be implemented in a 3GPP Long Term Evolution (LTE) system, an Ultra-Mobile Broadband (UMB) system, and other types of systems. LTE is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents from an organization named “3 rd  Generation Partnership Project” (3GPP), while cdma2000 is described in documents from an organization named “3 rd  Generation Partnership Project 2” (3GPP2). Although certain aspects of the disclosure may be described using 3GPP terminology, it is to be understood that the teachings herein may be applied to 3GPP (e.g., Rel99, Rel5, Rel6, Rel7) technology, as well as 3GPP2 (e.g., 1×RTT, 1×EV-DO Rel0, RevA, RevB) technology and other technologies. 
     Example Communication Device 
       FIG. 11  illustrates an example communication device  1100  (e.g., an AP, an AT, or some other type of device) according to certain aspects of the disclosure. The communication device  1100  includes an apparatus  1102  (e.g., an integrated circuit). In some aspects, the apparatus  1102  may be configured to operate in a wireless communication node (e.g., the AP  110  or an AT  120  of  FIG. 1 ) and to perform one or more of the operations described herein. For convenience, a wireless communication node (e.g., an AP, and AT, a relay, etc.) may be referred to as a wireless node. The apparatus  1102  includes a processing system  1104 , and a memory  1106  coupled to the processing system  1104 . Example implementations of the processing system  1104  are provided herein. In some aspects, the processing system  1104  and the memory  1106  of  FIG. 11  may correspond to the processing system  804  and the memory component  806  of  FIG. 8 . 
     The processing system  1104  is generally adapted for processing, including the execution of such programming stored on the memory  1106 . For example, the memory  1106  may store instructions that, when executed by the processing system  1104 , cause the processing system  1104  to perform one or more of the operations described herein. As used herein, the terms “programming” or “instructions” or “code” shall be construed broadly to include without limitation instruction sets, instructions, data, code, code segments, program code, programs, programming, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. In some implementations, the apparatus  1102  provides the firmware functionality and the host functionality as discussed herein. In some aspects, one or more of any components represented by dashed boxes in  FIG. 11  may be optional. 
     In some implementations, the apparatus  1102  communicates with another component (i.e., a component external to the apparatus  1102 ) of the communication device  1100 . For example, in some implementations, the apparatus  1102  provides the firmware functionality discussed herein and communicates with an external host component  1108  of the communication device  1100 . In this case, the host component  1108  provides the host functionality as discussed herein. To this end, in some implementations, the apparatus  1102  may include a send/receive interface  1110  (e.g., an interface bus, bus drivers, bus receivers, or other suitable circuitry) coupled to the processing system  1104  for sending information (e.g., radar data patterns, messages, etc.) between the processing system  1104  and the host component  1108 . In some implementations, the interface  1110  may be configured to interface the processing system  1104  to one or more other components (e.g., a radio frequency (RF) front end (e.g., a transmitter and/or a receiver)) of the communication device  1100  (other components not shown in  FIG. 11 ). 
     The apparatus  1102  may communicate with other apparatuses in various ways. In cases where the apparatus  1102  include an RF transceiver (not shown in  FIG. 11 ), the apparatus may transmit and receive information (e.g. a frame, a message, bits, etc.) via RF signaling. In some cases, rather than transmitting information via RF signaling, the apparatus  1102  may have an interface to provide (e.g., output, send, transmit, etc.) information for RF transmission. For example, the processing system may output information, via a bus interface, to an RF front end for RF transmission. Similarly, rather than receiving information via RF signaling, the apparatus  1102  may have an interface to obtain information that is received by another apparatus. For example, the processing system may obtain (e.g., receive) information, via a bus interface, from an RF receiver that received the information via RF signaling. 
     Example Processes 
       FIG. 12  illustrates a process  1200  for communication in accordance with some aspects of the disclosure. The process  1200  may take place within a processing system (e.g., the processing system  1104  of  FIG. 11 ), which may be located in an AP, an AT, or some other suitable apparatus. Of course, in various aspects within the scope of the disclosure, the process  1200  may be implemented by any suitable apparatus capable of supporting communication-related operations. 
     At block  1202 , an apparatus (e.g., an access point) determines whether radar detection is enabled. For example, the apparatus may provide a data pattern indicative of a radar signal for transmission to a component of the apparatus designated to perform a radar detection function, and then determine whether a response to the data is received from the component. 
     At block  1204 , the apparatus disables communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled. For example, the apparatus may ignore or reject a request to select the at least one communication channel. 
     The disabling may take various forms. In some aspects, the disabling of communication on the at least one wireless communication channel may include blocking the component from using the at least one wireless communication channel. In some aspects, the disabling of communication on the at least one wireless communication channel may include ignoring a request to select the at least one communication channel. In some aspects, the disabling of communication on the at least one wireless communication channel may include rejecting a request to select the at least one communication channel. 
     In some aspects, the at least one wireless communication channel may be associated with a radar detection requirement. For example, the at least one wireless communication channel may be a dynamic frequency selection channel. 
       FIG. 13  illustrates a process  1300  for communication in accordance with some aspects of the disclosure. In some aspects, the process  1300  may be used in conjunction with (e.g., in addition to or as part of) the process  1200  of  FIG. 12 . The process  1300  may take place within a processing system (e.g., the processing system  1104  of  FIG. 11 ), which may be located in an AP, an AT, or some other suitable apparatus. Of course, in various aspects within the scope of the disclosure, the process  1300  may be implemented by any suitable apparatus capable of supporting communication-related operations. 
     At block  1302 , an apparatus (e.g., an access point) provides a data pattern indicative of a radar signal for transmission to a component of the apparatus designated to perform a radar detection function. In some aspects, the data pattern may be a spoofed data pattern. 
     The data pattern may be provided in various ways. In some aspects, the apparatus may provide different data patterns indicative of different radar signals to the component over time. In some aspects, the apparatus may provide the data pattern randomly. In some aspects, the apparatus may provide the data pattern periodically. In some aspects, the apparatus may provide the data pattern on demand. In some aspects, the apparatus may provide the data pattern if Wi-Fi communication is enabled. In some aspects, the apparatus may provide the data pattern for a channel if the channel is in use. Thus, to provide the data pattern, the apparatus may perform at least one of: provide the data pattern on a random basis, provide the data pattern on a periodic basis, provide the data pattern on an on-demand basis, provide the data pattern if Wi-Fi communication is enabled, provide the data pattern for a channel if the channel is in use, or any combination thereof. 
     At block  1304 , the apparatus provides the data pattern to the component. For example, an interface of the apparatus may output a signal including the data pattern to the component. In some aspects, the component may be a host software component of the apparatus and the data pattern may be sent by a firmware component of the apparatus. 
     At block  1306 , the apparatus determines whether a response to the data pattern is received from the component. In some aspects, the response may include an indication of whether radar is present. 
     At block  1308 , the apparatus determines whether radar detection is enabled based, at least in part, on the determination of block  1306 . For example, the determination of whether radar detection is enabled may be based on the indication of whether radar is present. 
       FIG. 14  illustrates a process  1400  for communication in accordance with some aspects of the disclosure. In some aspects, the process  1400  may be used in conjunction with (e.g., in addition to or as part of) the process  1200  of  FIG. 12 . The process  1400  may take place within a processing system (e.g., the processing system  1104  of  FIG. 11 ), which may be located in an AP, an AT, or some other suitable apparatus. Of course, in various aspects within the scope of the disclosure, the process  1400  may be implemented by any suitable apparatus capable of supporting communication-related operations. 
     At block  1402 , an apparatus (e.g., an access point) obtains an indication that at least one wireless communication channel has been selected for communication. For example, a firmware component may receive an indication from a host component that communication will commence on a DFS channel or that a DFS channel is in use. As another example, host software may sends a virtual device start request message to radio firmware indicating the channel or channels to be used. 
     At block  1404 , the apparatus triggers the providing of the data pattern after obtaining the indication. For example, upon determining that the indication has been received, radio firmware may determine whether the channel is a DFS channel and, if so, invoke the process  1300  of  FIG. 13 . 
     In some aspects, an apparatus may perform any combination of the operations described above for  FIGS. 12-14 . 
     Example Apparatus 
     The components described herein may be implemented in a variety of ways. Referring to  FIG. 15 , an apparatus  1500  is represented as a series of interrelated functional blocks that represent functions implemented by, for example, one or more integrated circuits (e.g., an ASIC) or implemented in some other manner as taught herein. As discussed herein, an integrated circuit may include a processor, software, other components, or some combination thereof. 
     The apparatus  1500  includes one or more modules that may perform one or more of the functions described above with regard to various figures. For example, a circuit (e.g., an ASIC or a processing system) for determining  1502  may correspond to, for example, a processing system as discussed herein. A circuit (e.g., an ASIC or a processing system) for disabling communication  1504  may correspond to, for example, a processing system and/or a transceiver as discussed herein. A circuit (e.g., an ASIC or a processing system) for obtaining an indication  1506  may correspond to, for example, a processing system as discussed herein. A circuit (e.g., an ASIC or a processing system) for triggering  1508  may correspond to, for example, a processing system as discussed herein. A circuit (e.g., an ASIC or a processing system) for providing  1510  may correspond to, for example, an interface or a transmitter as discussed herein. 
     As noted above, in some aspects these modules may be implemented via appropriate processor components. These processor components may in some aspects be implemented, at least in part, using structure as taught herein. In some aspects, a processor may be configured to implement a portion or all of the functionality of one or more of these modules. Thus, the functionality of different modules may be implemented, for example, as different subsets of an integrated circuit, as different subsets of a set of software modules, or a combination thereof. Also, it should be appreciated that a given subset (e.g., of an integrated circuit and/or of a set of software modules) may provide at least a portion of the functionality for more than one module. In some aspects, one or more of any components represented by dashed boxes in  FIG. 15  may be optional. 
     As noted above, the apparatus  1500  comprises one or more integrated circuits in some implementations. For example, in some aspects a single integrated circuit implements the functionality of one or more of the illustrated components, while in other aspects more than one integrated circuit implements the functionality of one or more of the illustrated components. As one specific example, the apparatus  1500  may comprise a single device (e.g., with components  1502 - 1510  comprising different sections of an ASIC). As another specific example, the apparatus  1500  may comprise several devices (e.g., with the components  1502 - 1508  comprising one ASIC, and the component  1510  comprising another ASIC). 
     In addition, the components and functions represented by  FIG. 15  as well as other components and functions described herein, may be implemented using any suitable means. Such means are implemented, at least in part, using corresponding structure as taught herein. For example, the components described above in conjunction with the “ASIC for” components of  FIG. 15  correspond to similarly designated “means for” functionality. Thus, one or more of such means is implemented using one or more of processor components, integrated circuits, or other suitable structure as taught herein in some implementations. 
     The various operations of methods described herein may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components with similar functionality and/or numbering. For example, the blocks of the processes  1200 - 1400  illustrated in  FIGS. 12-14  may correspond at least in some aspects, to corresponding blocks of the apparatus  1500  illustrated in  FIG. 15 . For example, a means for determining whether radar detection is enabled may be the circuit for determining  1502 , a means for disabling communication on at least one wireless communication channel if the determination indicates that radar detection is not enabled may be the circuit for disabling communication  1504 , a means for obtaining an indication that the at least one wireless communication channel has been selected for communication may be the circuit for obtaining  1506 , a means for triggering the providing of the data pattern after obtaining the indication may be the circuit for triggering  1508 , or a means for providing the data pattern to the component may be the circuit for providing  1510 . 
     Example Programming 
     Referring to  FIG. 16 , programming stored by the memory  1602  (e.g. a storage medium, a memory device, etc.), when executed by a processing system (e.g., the processing system  1104  of  FIG. 11 ), causes the processing system to perform one or more of the various functions and/or process operations described herein. For example, the programming, when executed by the processing system  1104 , may cause the processing system  1104  to perform the various functions, steps, and/or processes described herein with respect to  FIGS. 1, 5, and 12-14  in various implementations. As shown in  FIG. 16 , the memory  1600  may include one or more of code for determining  1602 , code for disabling communication  1604 , code for obtaining  1606 , code for triggering  1608 , or code for sending  1610 . In some aspects, one of more of the code for determining  1602 , the code for disabling communication  1604 , the code for obtaining  1606 , the code for triggering  1608 , or the code for sending  1610  may be executed or otherwise used to provide the functionality described herein for the circuit for determining  1502 , the circuit for disabling communication  1504 , the circuit for obtaining  1506 , the circuit for triggering  1508 , or the circuit for sending  1510 . In some aspects, the memory  1600  of  FIG. 16  may correspond to the memory  1106  of  FIG. 11 . In some aspects, one or more of any components represented by dashed boxes in  FIG. 16  may be optional. 
     Additional Aspects 
     The examples set forth herein are provided to illustrate certain concepts of the disclosure. Those of ordinary skill in the art will comprehend that these are merely illustrative in nature, and other examples may fall within the scope of the disclosure and the appended claims. Based on the teachings herein those skilled in the art should appreciate that an aspect disclosed herein may be implemented independently of any other aspects and that two or more of these aspects may be combined in various ways. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, such an apparatus may be implemented or such a method may be practiced using other structure, functionality, or structure and functionality in addition to or other than one or more of the aspects set forth herein. 
     As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to any suitable telecommunication system, network architecture, and communication standard. By way of example, various aspects may be applied to wide area networks, peer-to-peer network, local area network, other suitable systems, or any combination thereof, including those described by yet-to-be defined standards. 
     Many aspects are described in terms of sequences of actions to be performed by, for example, elements of a computing device. It will be recognized that various actions described herein can be performed by specific circuits, for example, central processing units (CPUs), graphic processing units (GPUs), digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or various other types of general purpose or special purpose processors or circuits, by program instructions being executed by one or more processors, or by a combination of both. Additionally, these sequence of actions described herein can be considered to be embodied entirely within any form of computer readable storage medium having stored therein a corresponding set of computer instructions that upon execution would cause an associated processor to perform the functionality described herein. Thus, the various aspects of the disclosure may be embodied in a number of different forms, all of which have been contemplated to be within the scope of the claimed subject matter. In addition, for each of the aspects described herein, the corresponding form of any such aspects may be described herein as, for example, “logic configured to” perform the described action. 
     In some aspects, an apparatus or any component of an apparatus may be configured to (or operable to or adapted to) provide functionality as taught herein. This may be achieved, for example: by manufacturing (e.g., fabricating) the apparatus or component so that it will provide the functionality; by programming the apparatus or component so that it will provide the functionality; or through the use of some other suitable implementation technique. As one example, an integrated circuit may be fabricated to provide the requisite functionality. As another example, an integrated circuit may be fabricated to support the requisite functionality and then configured (e.g., via programming) to provide the requisite functionality. As yet another example, a processor circuit may execute code to provide the requisite functionality. 
     Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the aspects disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure. 
     One or more of the components, steps, features and/or functions illustrated in above may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated above may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware. 
     It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of example processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein. 
     The functions, methods, sequences or algorithms described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software and/or firmware module executed by a processor, or in a combination thereof. An example of a storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. 
     If implemented in software and/or firmware, the functions, methods, sequences or algorithms may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A computer-readable media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM, registers, flash memory, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of 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. Thus, in some aspects computer readable medium may comprise non-transitory computer-readable medium (e.g., tangible media, computer-readable storage medium, computer-readable storage device, etc.). Such a non-transitory computer-readable medium (e.g., computer-readable storage device) may comprise any of the tangible forms of media described herein or otherwise known (e.g., a memory device, a media disk, etc.). In addition, in some aspects computer-readable medium may comprise transitory computer readable medium (e.g., comprising a signal). Combinations of the above should also be included within the scope of computer-readable media. It should be appreciated that a computer-readable medium may be implemented in any suitable computer-program product. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Likewise, the term “aspects” does not require that all aspects include the discussed feature, advantage or mode of operation. 
     The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the aspects. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof. Moreover, it is understood that the word “or” has the same meaning as the Boolean operator “OR,” that is, it encompasses the possibilities of “either” and “both” and is not limited to “exclusive or” (“XOR”), unless expressly stated otherwise. It is also understood that the symbol “I” between two adjacent words has the same meaning as “or” unless expressly stated otherwise. Moreover, phrases such as “connected to,” “coupled to” or “in communication with” are not limited to direct connections unless expressly stated otherwise. 
     Any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations may be used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements may be used there or that the first element must precede the second element in some manner. Also, unless stated otherwise a set of elements may comprise one or more elements. In addition, terminology of the form “at least one of a, b, or c” or “a, b, c, or any combination thereof” used in the description or the claims means “a or b or c or any combination of these elements.” For example, this terminology may include a, or b, or c, or a and b, or a and c, or a and b and c, or  2   a , or  2   b , or  2   c , or  2   a  and  b , and so on. 
     As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining, and the like. Also, “determining” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Also, “determining” may include resolving, selecting, choosing, establishing, and the like. 
     While the foregoing disclosure shows illustrative aspects, it should be noted that various changes and modifications could be made herein without departing from the scope of the appended claims. The functions, steps or actions of the method claims in accordance with aspects described herein need not be performed in any particular order unless expressly stated otherwise. Furthermore, although elements may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.