Patent Publication Number: US-2015063319-A1

Title: Systems, methods, and apparatus for preventing multiple re-association attempts

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/871,227, filed Aug. 28, 2013 and entitled “SYSTEMS, METHODS, AND APPARATUS FOR PREVENTING MULTIPLE RE-ASSOCIATION ATTEMPTS,” the entirety of which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present application relates generally to wireless communications, and more specifically to systems, methods, and devices for increasing efficiency in wireless communication. 
     BACKGROUND 
     In many telecommunication systems, communications networks are used to exchange messages among several interacting spatially-separated devices. Networks may be classified according to geographic scope, which could be, for example, a metropolitan area, a local area, or a personal area. Such networks would be designated respectively as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), wireless local area network (WLAN), or personal area network (PAN). Networks also differ according to the switching/routing technique used to interconnect the various network nodes and devices (e.g., circuit switching vs. packet switching), the type of physical media employed for transmission (e.g., wired vs. wireless), and the set of communication protocols used (e.g., Internet protocol suite, SONET (Synchronous Optical Networking), Ethernet, etc.). 
     Wireless networks are often preferred when the network elements are mobile and thus have dynamic connectivity needs, or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infra-red, optical, etc. frequency bands. Wireless networks advantageously facilitate user mobility and rapid field deployment when compared to fixed wired networks. 
     WLANs use carrier-sense multiple access (CSMA) to share air time for transmission. Efficiency of a WLAN decreases when stations operating at a low data rate, (e.g., at a low modulation coding scheme (MCS) index) require a large amount of time to send a small amount of data when compared to stations operating at a high data rate (e.g., at a high MCS index). Accordingly, systems and methods for improved wireless communication would be beneficial. 
     SUMMARY 
     Various implementations of systems, methods and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the desirable attributes described herein. Without limiting the scope of the appended claims, some prominent features are described herein. 
     Details of one or more implementations of the subject matter described in this specification 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. 
     A method for preventing multiple re-association attempts is provided. The method comprises identifying a station. The method further comprises determining a back-off period for the station during which association requests from the station will be rejected. The method further comprises transmitting a message to the station, the message including the back-off period. 
     An apparatus for wireless communication is also provided. The apparatus comprises a processor configured to identify a station and determine a back-off period for the station during which association requests from the station will be rejected. The apparatus also comprises a transmitter configured to transmit a message to the station, the message including the back-off period. 
     Another method for preventing multiple re-association attempts is provided. The method comprises receiving a message from an access point, the message including a back-off period during which the access point will reject association requests. The method further comprises refraining from sending association requests to the access point during the back-off period. 
     Another apparatus for wireless communication is provided. The apparatus comprises a receiver configured to receive a message from an access point, the message including a back-off period during which the access point will reject association requests. The apparatus also comprises a processor configured to refrain from sending association requests to the access point during the back-off period. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of a wireless communication system in which aspects of the present disclosure may be employed. 
         FIG. 2  shows various components that may be utilized in a wireless device that may be employed within a wireless communication system. 
         FIG. 3  shows a call flow diagram of an access point disassociating a station, in accordance with certain embodiments described herein. 
         FIG. 4  shows a call flow diagram of basic service set transition communications between a station and two access points. 
         FIG. 5  shows a management frame comprising a frame body. 
         FIG. 6  shows a frame body comprising a reason code. 
         FIG. 7  shows a basic service set transition management request frame. 
         FIG. 8  shows a flow chart of a method for preventing multiple re-association attempts. 
         FIG. 9  shows a flow chart of another method for preventing multiple re-association attempts. 
     
    
    
     DETAILED DESCRIPTION 
     Various aspects of the novel systems, apparatuses, and methods are described more fully hereinafter with reference to the accompanying drawings. The teachings disclosed herein may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the novel systems, apparatuses, and methods disclosed herein, whether implemented independently of or combined with any other aspect of the invention. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the invention is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the invention set forth herein. It should be understood that any aspect disclosed herein may be embodied by one or more elements of a claim. 
     Although particular aspects are described herein, many variations and permutations of these aspects fall within the scope of the disclosure. Although some benefits and advantages of the preferred aspects are mentioned, the scope of the disclosure is not intended to be limited to particular benefits, uses, or objectives. Rather, aspects of the disclosure are intended to be broadly applicable to different wireless technologies, system configurations, networks, and transmission protocols, some of which are illustrated by way of example in the figures and in the following description of the preferred aspects. The detailed description and drawings are merely illustrative of the disclosure rather than limiting, the scope of the disclosure being defined by the appended claims and equivalents thereof. 
     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 WiFi or, more generally, any member of the IEEE  802 . 11  family of wireless protocols. For example, the various aspects described herein may be used as part of the IEEE 802.11ah, 801.11ac, 802.11n, 802.11g, and/or 802.11b protocols. 
     In some aspects, wireless signals in a sub-gigahertz band may be transmitted according to the 802.11ah protocol using orthogonal frequency-division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Implementations of the 802.11ah protocol may be used for sensors, metering, and smart grid networks. Advantageously, aspects of certain devices implementing the 802.11ah protocol may consume less power than devices implementing other wireless protocols, such as 802.11b and/or 802.11g for example, and/or may be used to transmit wireless signals across a relatively long range, for example about one kilometer or longer. 
     Certain of the devices described herein may further implement Multiple Input Multiple Output (MIMO) technology. This may also be implemented as part of the 802.11ah standard. A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels or streams. Each of the NS 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 which are the components that access the wireless network. For example, there may be two types of devices: access points (APs) and stations (STAs). In general, an AP serves as a hub or base station for the WLAN and an STA serves as a user of the WLAN. For example, an STA may be a laptop computer, a personal digital assistant (PDA), a mobile phone, etc. In an example, an STA connects to an AP via a WiFi (e.g., IEEE 802.11 protocol such as 802.11ah) compliant wireless link to obtain general connectivity to the Internet or to other wide area networks. In some implementations an STA may also be used as an AP. 
     An AP may also comprise, be implemented as, or known as 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. 
     An 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 AT 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 smartphone), a computer (e.g., a laptop), a portable communication device, a headset, a portable computing device (e.g., a PDA), 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. 
     As discussed above, certain of the devices described herein may implement the 802.11ah standard, for example. Such devices, whether used as an STA, an AP, or other device, may be used for smart metering or in a smart grid network. Such devices may provide sensor applications or be used in home automation. The devices may instead or in addition be used in a healthcare context, for example for personal healthcare. They may also be used for surveillance, to enable extended-range Internet connectivity (e.g. for use with hotspots), or to implement machine-to-machine communications. 
       FIG. 1  shows an example of a wireless communication system  100  in which aspects of the present disclosure may be employed. The wireless communication system  100  may operate pursuant to a wireless standard, for example at least one of the 802.11ah, 802.11ac, 802.11n, 802.11g and 802.11b standards. The wireless communication system  100  may include an AP  104 , which may communicate with one or more STAs  106 . 
     A variety of processes and methods may be used for transmissions in the wireless communication system  100  between the AP  104  and the STAs  106 . For example, signals may be transmitted and received between the AP  104  and the STAs  106  in accordance with OFDM/OFDMA techniques. If this is the case, the wireless communication system  100  may be referred to as an OFDM/OFDMA system. Alternatively, signals may be transmitted and received between the AP  104  and the STAs  106  in accordance with CDMA techniques. If this is the case, the wireless communication system  100  may be referred to as a CDMA system. 
     A communication link that facilitates transmission from the AP  104  to one or more of the STAs  106  may be referred to as a downlink (DL)  108 . A communication link that facilitates transmission from one or more of the STAs  106  to the AP  104  may be referred to as an uplink (UL)  110 . Alternatively, a DL  108  may be referred to as a forward link or a forward channel, and a UL  110  may be referred to as a reverse link or a reverse channel. 
     The AP  104  may provide wireless communication coverage in a basic service area (BSA)  102 . The AP  104  along with the STAs  106  associated with the AP  104  and that use the AP  104  for communication may be referred to as a basic service set (BSS). It should be noted that the wireless communication system  100  may not have a central AP  104 , but rather may function as a peer-to-peer network between the STAs  106 . Accordingly, the functions of the AP  104  described herein may alternatively be performed by one or more of the STAs  106 . 
       FIG. 2  shows various components that may be utilized in a wireless device  202  that may be employed within the wireless communication system  100 . The wireless device  202  is an example of a device that may be configured to implement the various methods described herein. For example, the wireless device  202  may be configured as the AP  104  or as one of the STAs  106 . The wireless device  202  may comprise a housing  208  for enclosing at least some of the components of the wireless device  202 . 
     The wireless device  202  may comprise a communication bus  230  which may be coupled to each component of the wireless device  202 . The communication bus  230  may be configured to enable communication of data and signals between the components of the wireless device  202 . The communication bus  230  may comprise 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 wireless device  202  may be coupled together or accept or provide inputs to each other using some other mechanism. 
     The wireless device  202  may also comprise a processor  204  coupled to the communication bus  230 . The processor  204  may control the operations of each component of the wireless device  202 . The processor  204  may also be referred to as a central processing unit (CPU). The wireless device  202  may also comprise a memory unit  206  coupled to the communication bus  230 . The memory unit  206  may comprise read-only memory (ROM) and/or random access memory (RAM), and may provide instructions and data to the processor  204 . A portion of the memory unit  206  may also include non-volatile random access memory (NVRAM). The processor  204  may perform logical and arithmetic operations based on program instructions stored within the memory unit  206 . The instructions stored in the memory unit  206  may be executable to implement the methods described herein. 
     The processor  204  may comprise or be a component of a 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 wireless device  202  may also comprise a transmitter  210  and a receiver  212 , both of which are coupled to communication bus  230 . The transmitter  210  and the receiver  212  may be configured to allow transmission and reception of data between the wireless device  202  and a remote location. The transmitter  210  and receiver  212  may be combined into a transceiver  214 . The wireless device  202  may also comprise an antenna  216  which may be attached to the housing  208  and coupled to the transceiver  214 . The wireless device  202  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas, which may be utilized during MIMO communications, for example. 
     The wireless device  202  may also comprise a signal detector  218  coupled to the communication bus  230 . The signal detector  218  may be used in an effort to detect and quantify the level of signals received by the transceiver  214 . The signal detector  218  may detect such signals as total energy, energy per subcarrier per symbol, power spectral density and other signals. The wireless device  202  may also comprise a DSP  220  coupled to the communication bus  230 . The DSP  220  may be used for processing signals. The DSP  220  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 wireless device  202  may further comprise a user interface  222  in some aspects. The user interface  222  may comprise a keypad, a microphone, a speaker, and/or a display. The user interface  222  may include any element or component that conveys information to a user of the wireless device  202  and/or receives input from the user. 
     Although a number of separate components are illustrated in  FIG. 2 , those of skill in the art will recognize that one or more of the components may be combined or commonly implemented. For example, the processor  204  may be used to implement not only the functionality described above with respect to the processor  204 , but also to implement the functionality described above with respect to the signal detector  218  and/or the DSP  220 . Further, each of the components illustrated in  FIG. 2  may be implemented using a plurality of separate elements. 
     As discussed above, the wireless device  202  may comprise an AP  104  or an STA  106 , and may be used to transmit and/or receive communication. The communications exchanged between devices in a wireless network may include data units which may comprise packets or frames. In some aspects, the data units may include data frames, control frames, and/or management frames. Data frames may be used for transmitting data from an AP and/or an STA to other APs and/or STAs. Control frames may be used together with data frames for performing various operations and for reliably delivering data (e.g., acknowledging receipt of data, polling of APs, area-clearing operations, channel acquisition, carrier-sensing maintenance functions, etc.). Management frames may be used for various supervisory functions (e.g., for joining and departing from wireless networks, etc.). 
       FIG. 3  shows a call flow diagram  300  of an AP  302  disassociating an STA  304 , in accordance with an exemplary embodiment. In the call flow diagram  300 , calls occurring earlier in time are shown vertically above calls occurring later in time. The AP  302  may be configured as the AP  104  of  FIG. 1  and the STA  304  may be configured as the STA  106  of  FIG. 1 . As described above, the AP  302  and the STA  304  may communicate with each other over a wireless protocol. In some embodiments, in order to establish communication between the AP  302  and the STA  304 , the STA  304  may request association with the AP  302  and the AP  302  may acknowledge the STA&#39;s  302  association request. The AP  302  may disassociate the STA  304  to cease communication with the STA  304 . 
     As described above, an STA operating at a lower MCS may require a larger amount of time to send a set amount of data compared to an STA operating at a higher MCS. As such, an STA operating at a lower MCS compared to other STAs associated to one AP may lower the overall wireless communication efficiency of the AP. In order to increase wireless communication efficiency the AP may identify an STA operating a low MCS and may disassociate that STA from the AP. The AP may identify the STA based on a threshold MCS index or based on a difference between the MCS index of the identified STA and the MCS indexes of other associated STAs. 
     In  FIG. 3 , the STA  304  may be associated with the AP  302 . The AP  302  may determine an acceptable MCS range based on its channel usage. The AP  302  may re-determine its acceptable MCS range over time. The AP  302  may determine that the STA  304  is operating at an MCS that lower than the acceptable range. The STA  304  may be using a longer amount of air time to transmit data compared to other STAs associated with the AP  302 . The AP  302  may send a disassociation message  306  to STA  304  to disassociate the STA  304 . The dissociation message  306  may comprise a reason code indicating that the STA  304  is operating at a low MCS. In some embodiments, the disassociation message  306  may comprise a management frame of type disassociation and may comprise a reason code field indicating a low MCS. The AP  302  may also indicate to the STA  304  an MCS range that is acceptable and would not result in the AP  302  disassociating the STA  304 . In some embodiments, the STA  304  may be able to increase its MCS and may indicate the increase MCS to the AP  302  to avoid disassociation. 
     The disassociation message  306  may also indicate a timeout period  308  after which the AP  302  may disassociate the STA  304 . During the timeout period  308 , the STA  304  may communicate with the AP  302 . For example, the STA  304  may transmit pending transmissions  312  and may also request information in preparation for the disassociation. The timeout period  308  is beneficial because immediate disconnection of the STA  304  may disrupt user applications of the STA  304 . During the timeout period  308 , the STA  304  may be able to associate with another AP to maintain wireless communication with a network. For example, the STA  304  may send an association request to another AP in the same cell area. In some embodiments, the STA  304  may not send a request for association to another AP and may instead listen for a beacon or other transmission from another AP in response to receiving the disassociation message  306 . In some embodiments, the AP  302  may aid the STA  304  with synchronization and discovery functions for the STA  304  to associate with another AP in the network. As described above, after the timeout period  308 , the AP  302  may disassociate the STA  304 . The disassociation may occur at the end of the timeout period  308  or after a period of time after the end of the timeout period  308 . 
     The disassociation message  306  sent from the AP  302  to the STA  304  may also indicate a back-off period  310  during which the AP  302  will reject association requests from the STA  304 . In some embodiments, the AP  302  may provide the back-off period  310  to the STA  304  as a separate message. As shown in  FIG. 3 , the back-off period  310  may begin adjacent in time with the end of the timeout period  308 . In some embodiments, the back-off period  310  may begin an amount of time after the end of the timeout period  308 . 
     The AP  302  may store a list of the MAC addresses for STAs that are disassociated along with a corresponding list back-off periods for each STA. As shown in  FIG. 3 , the STA  304  may transmit an association request  320  to the AP  302  during the back-off period  310 . The AP  302  may determine that the STA  302  was previously disassociated from the AP  302  and assigned the back-off period  310 . The AP  302  may determine that the association request  320  was received within the back-off period  310  and the AP  302  may reject the association request  320 . The AP  302  may respond to the association request  320  with an association response frame having a status code of “reject.” In some embodiments, the association response frame from the AP  302  may also indicate a second back-off period for preventing association requests from the STA  304 . After the back-off period  310  has ended, the AP  302  may accept an association request  312  from the STA  304 . The STA  304  may send an association request  330  after the back-off period  310  has expired. The AP  302  may accept the association request  330  or it may deny the association request based on an MCS of the STA  304  as described above. 
     In some embodiments, the timeout period  308  and the back-off period  310  may vary over time for the same STA  304  or may be different for different STAs communicating with the same AP  302 . For example, the AP  302  may provide a first timeout period  308  before disassociating the STA  304  and a second, different timeout period (not shown) to disassociate the same STA  304  after the STA  304  has re-associated with the AP  302 . In other embodiments, the timeout period  308  and the back-off period  310  may remain fixed over a period of time or consistent for STAs communicating with the same AP  302 . In some embodiments, the disassociation message  306  may only comprise the timeout period  308  and not the back-off period  310 . 
     The AP  302  may also provide a back-off period in response to a probe request from the STA  304 . The AP  302  may determine that the STA  304  is operating at an MCS that is below the acceptable MCS range of the AP  302  and the AP  302  may respond to the probe request from the STA  304  with a probe rejection indicating a back-off period during which the STA  304  may not send any further probe requests to the AP  302 . The AP  302  may also provide a reason code to the STA  304  indicating a low MCS. The AP  302  may also indicate the acceptable MCS range to the STA  304 . 
     The AP  302  may also provide a back-off period in response to an authentication request from an STA  302 . The AP  302  may determine that the STA  304  is operating at an MCS that is below the acceptable MCS range of the AP  302  and the AP  302  may respond to the authentication request with an authentication rejection indicating a back-off period during which the STA  304  may not send any further authentication requests to the AP  302 . The AP  302  may also provide a reason code to the STA  304  indicating a low MCS. The AP  302  may also indicate the acceptable MCS range to the STA  304 . 
       FIG. 4  shows a call flow diagram  400  of BSS transition communications between an STA  404  and two APs  402  and  416 . In the call flow diagram  400 , calls occurring earlier in time are shown vertically above calls occurring later in time. The first AP  402  may be configured as the AP  104  of  FIG. 1 , the second AP  416  may also be configured as the AP  104  of  FIG. 1 . The STA  304  may be configured as the STA  106  of  FIG. 1 . Before the call flow exchange of  FIG. 4  occurs, the STA  404  may be associated with the first AP  402 . As such, the STA  404  may be part of a BSS of the first AP  402 . In this embodiment, the first AP  402  may identify the STA  404  to transition to a second AP&#39;s  416  BSS. The STA  404  may be operating at a lower efficiency level (e.g., a lower MCS) compared to other STAs that are being serviced by the first AP  402 . As such, the STA  404  may be negatively impacting the overall transmission efficiency of the first AP  402 . The AP  402  may determine an acceptable MCS range for associated STAs based on its channel usage. The first AP  402  may identify the STA  404  to transition to another BSS based on an MCS of the STA  404  being below the acceptable MCS range. 
     In order to transfer the STA  404 , the first AP  402  may transmit a BSS transition message  406  to the STA  404  indicating for the STA  404  to transfer to the second AP&#39;s  416  BSS within a specified timeout period  408 . The STA  404  may transmit any pending transmission (not shown) to the AP  402  during the timeout period  408 . In one embodiment, the BSS transition message  406  may include an identifier of the STA  404 . The BSS transition message  406  may also indicate a back-off period  410  during which the first AP  402  will refuse any further association requests from the STA  404 . The beginning of the back-off period  410  may occur adjacent in time to the end of the timeout period  408 . As shown in  FIG. 4 , the AP  402  may refuse or ignore an association request  418  from the STA  404  during the back-off period  410 . In response to receiving the BSS transition message, the STA  404  may send an association request  406  to the second AP  416 . The STA  404  may send the association request  406  to the AP  416  during the timeout period  408 . The STA  404  may also send the association request  406  to the AP  416  after the timeout period. In some embodiments, the AP  402  may provide to STA  404  a reason for the BSS transition message being sent (e.g., due to the MCS that is being used by the STA  404 ). The AP  402  may accept an association request  412  from the STA  404  sent after the back-off period  410 . 
       FIG. 5  shows a management frame  500  comprising a frame body  502 . In some embodiments, the management frame  500  may comprise fields such as a frame control field  510 , a duration field  512 , an address  1  field  514 , an address  2  field  516 , an address  3  field  518 , a sequence control field  520 , a high throughput control field  522 , frame body  502 , and a frame check sequence field  524 . The disassociation message  306  of  FIG. 3  may be a management frame  500 . In another embodiment, the BSS transition management request  406  of  FIG. 4  may be a management frame  500 . 
       FIG. 6  shows the frame body field  502  of the management frame  500  of  FIG. 5 . In some embodiments, the frame body  502  may comprise a reason code field  602 , an optional vendor-specific element field  604 , and a management message integrity code element field  606 . The disassociation message  306  of  FIG. 3  may indicate a reason code in the reason code field  602  of a management frame. 
       FIG. 7  shows a BSS transition management request frame  700 , in accordance with an exemplary embodiment. The BSS transition management request frame  700  may contain fields such as a category field  710 , an action field  712 , a dialog token field  714 , a request mode field  716 , a disassociation timer field  702 , a validity interval field  718 , a BSS termination duration field  720 , a session information URL field  722 , and a BSS transition candidate list entries field  724 . The BSS transition message request  406  of  FIG. 4  may indicate a timeout period in the disassociation timer field  702 . 
       FIG. 8  shows a flow chart  800  of a method for preventing multiple re-association attempts, in accordance with an exemplary embodiment. Before the start of the method, an STA may be associated with an AP as described above. At block  802 , the method may identify an STA. At block  804 , the method may determine a back-off period for the STA during which association requests from the STA will be rejected. At block  806 , the method may transmit a message to the STA, the message including the back-off period. 
       FIG. 9  shows a flow chart  900  of another method for preventing multiple re-association attempts, in accordance with an exemplary embodiment. Before the start of the method, an STA may be associated with an AP, as described above. At block  902  the method may receive a message from an AP, the message including a back-off period during which the AP will reject association requests. As described above, the message may be sent by the AP due to the fact that the STA is operating at a lower efficiency level, e.g., is encoding data at a lower MCS, than other STAs that are being serviced by the AP and is thereby negatively impacting the overall efficiency of the AP. At step  904  the method may refrain from sending association requests to the AP during the back-off period. 
     A person/one having ordinary skill in the art would understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     Various modifications to the implementations described in this disclosure can be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the disclosure is not intended to be limited to the implementations shown herein, but is to be accorded the widest scope consistent with the claims, the principles and the novel features disclosed herein. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. 
     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 sub-combination. Moreover, although features can 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 can be directed to a sub-combination or variation of a sub-combination. 
     The various operations of methods described above may be performed by any suitable means capable of performing the operations, such as various hardware and/or software component(s), circuits, and/or module(s). Generally, any operations illustrated in the Figures may be performed by corresponding functional means capable of performing the operations. 
     The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a general purpose processor, a DSP, an application specific integrated circuit (ASIC), a field programmable gate array signal (FPGA) or other programmable logic device (PLD), 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, but in the alternative, the processor may be any commercially available processor, controller, microcontroller or state machine. A processor may also 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 one or more aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. 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. 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 storage 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, EEPROM, CD-ROM 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). In addition, in some aspects computer readable medium may comprise transitory computer readable medium (e.g., a signal). Combinations of the above should also be included within the scope of computer-readable media. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein can be downloaded and/or otherwise obtained by a user terminal and/or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and/or base station can obtain the various methods upon coupling or providing the storage means to the device. Moreover, any other suitable technique for providing the methods and techniques described herein to a device can be utilized. 
     While the foregoing is directed to aspects of the present disclosure, other and further aspects of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.