Abstract:
Some embodiments described herein provide a method for transmitting a preamble in accordance with a wireless local area network communication protocol. In some embodiments, a data frame may be obtained for transmission including a preamble compliant with the wireless local area network communication protocol. It may be determined that the preamble includes a first preamble portion that spans multiple symbol durations and a second preamble portion that spans a single symbol duration. The first preamble portion via beamforming may be transmitted based on a first beamforming matrix. When a transmission mode of the second preamble portion is beamforming, a second beamforming matrix may be generated based on the first beamforming matrix, each tone for the second preamble portion may be calculated based on the second beamforming matrix. Each calculated tone may be transmitted in accordance with the wireless local area network communication protocol.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This disclosure claims the benefit of U.S. Provisional Patent Application No. 62/216,550, filed Sep. 10, 2015; and U.S. Provisional Patent Application No. 62/246,316, filed Oct. 26, 2015. 
         [0002]    This application is related to PCT International Application No. ______, filed on Sep. 9, 2016. The aforementioned applications are all hereby incorporated by reference in their entireties. 
     
    
     FIELD OF USE 
       [0003]    This disclosure relates to a preamble transmission mechanism in a wireless data transmission system; for example, a wireless local area network (WLAN) implementing the IEEE 802.11 standard, which can be used to provide wireless transfer of data in outdoor deployments, outdoor-to-indoor communications, and device-to-device (P2P) networks. 
       BACKGROUND OF THE DISCLOSURE 
       [0004]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure. 
         [0005]    Wireless local area networks (WLANs) operate under WLAN standards such as the Institute for Electrical and Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, and 802.11n Standards. The 802.11 standards may specify transmission protocols and data frame formats for data packets. For example, the 802.11 standards may adopt a physical layer convergence procedure (PLCP), under which the PLCP protocol data unit (PPDU) format is used for preamble. The existing 802.11 PPDU in 2.4/5 GHz has a mixed format structure, which includes legacy 802.11a/g portion of preambles and other format portions of preambles suitable for more recently developed 802.11 standards. Such a mixed format preamble is effective in backward compatibility and performance. Thus, because of the mixed structure, a transmission mechanism for the preamble is needed to adapt to both the legacy portion and the non-legacy portion, which can be compatible with the more recently developed 802.11 standards. 
       SUMMARY 
       [0006]    Some embodiments described herein provide a method for transmitting a preamble in accordance with a wireless local area network communication protocol. In some embodiments, a data frame may be obtained for transmission including a preamble compliant with the wireless local area network communication protocol. It may be determined that the preamble includes a first preamble portion that spans multiple symbol durations and a second preamble portion that spans a single symbol duration. The first preamble portion via beamforming may be transmitted based on a first beamforming matrix. When a transmission mode of the second preamble portion is beamforming, a second beamforming matrix may be generated based on the first beamforming matrix, each tone for the second preamble portion may be calculated based on the second beamforming matrix. Each calculated tone may be transmitted in accordance with the wireless local area network communication protocol. 
         [0007]    In some implementations, the first preamble portion includes a high efficiency short training field (HESTF), and a high efficiency long training field (HELTF), and the second preamble portion includes legacy training fields and signaling configuration fields. 
         [0008]    In some implementations, when the transmission mode of the second preamble portion is omni-directional, the second preamble portion may be transmitted in omni-direction with no data transmission on guard tones that are configured in accordance with the wireless local area network communication protocol. 
         [0009]    In some implementations, channel estimation may be performed using a first training field contained in the first preamble portion even if channel estimation has been performed based on a second training field contained in the second preamble portion. 
         [0010]    In some implementations, guard tones may be filled in accordance with the wireless local area network communication protocol with extended symbols. 
         [0011]    In some implementations, the extended symbols are known symbols for a receiver to perform channel estimation. 
         [0012]    In some implementations, at least one of cyclic delay diversity (CDD) and cyclic shift diversity (CSD) may be applied to the preamble. 
         [0013]    In some implementations, when the CSD is applied in time domain to the second preamble portion, the same CSD is applied in time domain to the first preamble portion. 
         [0014]    In some implementations, when the CDD is applied in frequency domain to the second preamble portion, the same or a different CDD is applied in frequency domain to the first preamble portion. 
         [0015]    In some implementations, the second preamble portion may be transmitted via a mixed transmission mode of beamforming and omni-direction, wherein the mixed transmission mode is specified via a data value transmitted with the preamble, or implied by a transmission characteristic of the second preamble portion. 
         [0016]    Some embodiments described herein provide a system for transmitting a preamble in accordance with a wireless local area network communication protocol. The system includes processing circuitry that is configured to obtain a data frame for transmission including a preamble compliant with the wireless local area network communication protocol, and determine that the preamble includes a first preamble portion that spans multiple symbol durations and a second preamble portion that spans a single symbol duration. The system further includes a network interface that is configured to transmit the first preamble portion via beamforming based on a first beamforming matrix. When a transmission mode of the second preamble portion is beamforming, the processing circuitry is configured to generate a second beamforming matrix based on the first beamforming matrix, and calculate each tone for the second preamble portion based on the second beamforming matrix. The network interface is configured to transmit each calculated tone under the wireless local area network communication protocol. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Further features of the disclosure, its nature and various advantages will become apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
           [0018]      FIG. 1  is a block diagram of an example wireless WLAN  100  that the preamble transmission mechanism can be operated within, according to some embodiments described herein; 
           [0019]      FIG. 2  provides an example block diagram illustrating an example of data transmission scheme  200  for a preamble under 802.11ac, according to some embodiments described herein; 
           [0020]      FIG. 3  provides an example block diagram illustrating an example of data transmission scheme  200  for a preamble frame structure under 802.11ax, according to some embodiments described herein; 
           [0021]      FIG. 4  provides an example logic flow diagram illustrating aspects of transmitting the 1× symbol duration portion of preamble  301  and the 4× symbol duration portion of preamble/data  302 , according to some embodiments described herein; 
           [0022]      FIG. 5  provides an example block diagram illustrating a transmission scheme  500  for the 1× symbol duration portion of a preamble (e.g., see preamble  301  in  FIG. 3 ), according to some embodiments described herein; and 
           [0023]      FIG. 6  provides an example logic flow diagram illustrating a receiver processing a received preamble, according to some embodiments described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    This disclosure describes methods and systems for transmitting a preamble within an 802.11 wireless network. In some embodiments, the PPDU under 802.11ax may include two different portions of preamble, e.g., a 1× symbol duration portion of preamble and a 4× symbol duration portion of preamble. While the 4× symbol duration portion of preamble is usually transmitted using beamforming, the 1× symbol duration portion of preamble may also be transmitted via beamforming, instead of the omni-directional transmission under 802.11ac. In this way, the power configuration of transmitting the two portions of the preamble of the same PPDU may remain the same and thus do not require re-configuration. In addition, when the 1× symbol duration portion of preamble is transmitted via beamforming, data fields in both the 1× symbol duration portion of preamble and the 4× symbol duration portion of preamble can be used for channel estimation. Also, extended symbols may be filled on the 802.11a guard tones, which can be used to enhance channel estimation at the receiver. Thus, channel performance of the PPDU transmission may be improved. 
         [0025]      FIG. 1  is a block diagram of an example wireless WLAN  100  that the preamble transmission mechanism can be operated within, according to some embodiments described herein. A wireless access point  110  (AP) includes a host processor  105  that may be configured to process or assist in data operation, such as modulation/demodulation, encoding/decoding, encryption/decryption, and/or the like. For example, the host processor  105  may be configured to configure and/or process the data frames illustrated in  FIGS. 2-3 , and/or perform the work flows illustrated in  FIGS. 4 and 6 . 
         [0026]    A network interface device  107  is coupled to the host processor  105 , which is configured to interface with an outer network. The network interface device  107  includes a medium access control (MAC) processing unit  108  and a physical layer (PHY) processing unit  109 . The PHY processing unit  109  includes a plurality of transceivers  111 , and the transceivers  111  are coupled to a plurality of antennas  112 . 
         [0027]    The WLAN  100  includes a plurality of client stations  120   a - c . Although three client stations  120   a - c  are illustrated in  FIG. 1 , the WLAN  100  can include different numbers (e.g., 1, 2, 3, 5, 6, etc.) of client stations  120   a - c  in various scenarios and embodiments. Each client station, e.g.,  120   a - c , may have a similar structure as that of an AP  110 . For example, the client station  120   c  can include a host processor  125  coupled to a network interface device  127 . The network interface device  127  includes a MAC processing unit  128  and a PHY processing unit  129 . The PHY processing unit  129  includes a plurality of transceivers  131 , and the transceivers  131  are coupled to a plurality of antennas  132  to receive or transmit data from or to the wireless communication channel. 
         [0028]    Two or more of the client stations  120   a - c  may be configured to receive data such as including an 802.11 PPDU  130 , which may be transmitted simultaneously by the AP  110 . Additionally, two or more of the client stations  120   a - c  can be configured to transmit data to the AP  110  such that the AP  110  receives the data. An example data structure of a preamble under 802.11ac is illustrated in  FIG. 2 . 
         [0029]      FIG. 2  provides an example block diagram illustrating an example data transmission scheme  200  for a preamble under 802.11ac, according to some embodiments described herein. The legacy portion of the preamble may include a legacy short training field (LSTF  201 ), a legacy long training field (LLTF  202 ), a legacy signal field (LSIG  203 ), and a very high throughput (VHT) signal field A (SIGA), which may be transmitted in omni-direction at  220 . In another example, the non-legacy preamble, e.g., a preamble developed for the later version of the 802.11 standards, the VHT short training field (VHTSTF  205 ) and VHT long training field (VHTLTF  206 ), together with the payload data  207 , may be transmitted via beamforming, at  230 . 
         [0030]    Thus, the legacy portion and part of the non-legacy preamble may be transmitted in an 802.11a tone plan. For example, some of preamble fields (e.g., fields  201 - 204 ) are duplicated (e.g., see duplicated fields  211 - 214 ,  221 - 224  and  231 - 234 , which are the duplicates of fields  201 - 204 ) over each 802.11a 20 MHz channel when the bandwidth is greater than 20 MHz. The transmission of the duplicated copies may be separated by guard tones  245  per each 802.11a 20 MHz channel. 
         [0031]    Due to the different transmission schemes for the omni-directional preamble  220  and beamformed preamble  230 , additional configuration of transmission parameters may need to be performed. For example, an LSTF-based automatic gain control (AGC) may need to be reset when the transmission scheme switches from omni-directional to beamforming. For another example, the LLTF-based channel estimates obtained during omni-directional transmission may not be for the payload data transmission because the payload data  207  is transmitted via beamforming. Thus, the omni-directional preamble  220  may not be useful in the beamformed portion  230 . 
         [0032]      FIG. 3  provides an example block diagram illustrating an example data transmission scheme  200  for a preamble frame structure under 802.11ax, according to some embodiments described herein. The 802.11ax PPDU includes a 1× symbol duration portion of preamble  301  (tone spacing=312.5 KHz), and a 4× symbol duration portion of preamble and data  302  (tone spacing=312.5/4 KHz). The 1× symbol duration portion of preamble  301  includes, in addition to the LSTF, LLTF and LSIG fields, a repeated LSIG (RLSIG  305 ), a high efficiency signal field A  306  (SIGA) and an HE signal field B  307  (HE-SIGB). Specifically, the HESIGB is used to signal the resource unit signaling and physical layer (PHY) configuration for data transmission; and the HESIGA  306  provides channel-SIGB mapping information, e.g., the information of which channels is carried by the HESIGB. Thus, the 1× symbol duration portion of preamble  301  is to be transmitted in a way that the 1× symbol duration portion of preamble  301  can be useful during the transmission of the 4× symbol duration portion of preamble and data  302 . 
         [0033]      FIG. 4  provides an example logic flow diagram illustrating aspects of transmitting the 1× symbol duration portion of preamble  301  and the 4× symbol duration portion of preamble/data  302 , according to some embodiments described herein. At  401 , a wireless transmitter (e.g., an 802.11 transmitter) may obtain a data frame for transmission. For example, the data frame may be but is not limited to the 802.11ax preamble in  FIG. 3 . At  402 , the transmitter may determine the 1× symbol duration portion of preamble (e.g., portion  301 ) and the 4× symbol duration portion of preamble/data (e.g., portion  302 ). At  403 , the 4× symbol duration portion of preamble/data may be transmitted via beamforming. 
         [0034]    At  404 , the transmission mode for the 1× symbol duration portion of preamble may be determined, e.g., based on a pre-defined configuration of the data frame. In one implementation, at  406 , the 1× symbol duration portion of preamble  301  may be transmitted in omni-direction over 802.11a tones, in a similar manner as the omni-directional portion of preamble  220  under 802.11ac in  FIG. 2 . In this way, the data transmission may be operated in a similar manner as that in an 802.11n/ac system, except that AGC may be redone using a high efficiency short training field (HESTF  308 ), and channel estimation may be restarted using a high efficiency long training field (HELTF  309 ). 
         [0035]    In another implementation, the 1× symbol duration portion of preamble  301  may also be beamformed with one spatial stream. For example, at  407 , the beamforming matrix Q can be designed based on the 4× symbol duration portion of preamble and data  302  on the frequency domain. When multiple transmitting antennas are deployed, time domain cyclic delay diversity (CDD) may be used for antenna mapping in the frequency domain. Specifically, the j th  column of the training matrix A for HELTF may be used to map a single stream to the number of spatial streams of the beamforming matrix Q, in which j can be any available column, e.g., j=1, 3, 5, . . . . 
         [0036]    At  409 , the k th  tone of the 1× symbol duration portion of preamble  301  in the frequency domain may be calculated as: 
         [0000]    
       
         
           
             
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         [0037]    where x field,k   (i     TX     )  denotes the k th  tone of the 1× symbol duration portion of preamble  301  at the i th  transmitting antenna; N sts,k  denotes the number of space-time streams at the k th  tone; Q k  denotes the beamforming matrix on the k th  tone and 
         [0000]    
       
         
           
             
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         [0000]    denotes the entry on the i TX -th row and m-th column; A field   k  denotes the training matrix for HELTF on the k th  tone and └A field   k ┘ m,1  denotes the entry on the m-th row and first column; s field,k  denotes the data symbol being transmitted on the k th  tone; and Δ F T CS,HE (m) denotes the delay diversity factor that adds a linear phase on the k th  tone. 
         [0038]    Specifically, back to  407 , the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  may be calculated per each Q matrix for the 4× symbol duration portion of preamble and data  302 . The calculation may be written as: 
         [0000]        Q   k,1×   ×f ( Q   k,4×   ,k=−N   SR   , . . . ,N   SR ) 
         [0000]    where N SR  denotes the number of tones. For example, the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  may be the same as the beamforming matrix of the 4k-th tone on the 4× symbol duration portion of preamble and data  302 , e.g., 
         [0000]    
       
      
       Q 
       k,1× 
       =Q 
       4k,4× 
      
     
         [0039]    In another example, the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  may be the beamforming matrix of non-empty tone closest in frequency on the 4× symbol duration portion of preamble and data  302 . Or alternatively, the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  may be the interpolation of the beamforming matrices on the tones around the frequency for the 4× symbol duration portion of preamble and data  302 . 
         [0040]    In a different example, the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  may be calculated per each Q matrix for a 4× symbol duration portion of preamble and data. In this way, the beamforming matrix Q k  on the k th  tone of the 1× symbol duration portion of preamble  301  is the same as that of the k th  tone of the 4× symbol duration portion of preamble and data. 
         [0041]    In one implementation, at  411 , when multiple transmitting antennas are deployed, cyclic delay diversity (CDD) or cyclic shift diversity (CSD) may be applied on the frequency domain per stream. Or alternatively, CDD or CSD may be applied on the time domain per antenna. Or alternatively, a combination of both frequency-domain and time-domain CDD/CSD may be applied. 
         [0042]    If time-domain CSD is applied on LLTF (e.g., see field  202  in  FIG. 2  or field  311  in  FIG. 3 ), the same time-domain CSD is also applied on any HTLTF (high throughput LTF, not shown in the figures), VHTLTF (e.g., see field  206  in  FIG. 2 ), HELTF (e.g., see field  309  in  FIG. 3 ) and the data field (e.g., see field  320  in  FIG. 3 ). Conversely, if time-domain CSD is not applied on LLTF, then time-domain CSD is not applied on any of the HTLTF/VHTLTF/HELTF/data fields either. 
         [0043]    However, frequency-domain CSD allows more flexibility. If frequency-domain CSD is applied on LLTF (e.g., see field  202  in  FIG. 2  or field  311  in  FIG. 3 ), the same, another different or no frequency-domain CSD is also applied on HTLTF/VHTLTF/HELTF, and the same or the other different or no frequency-domain CSD can be applied on the data field. If frequency-domain CSD is not applied on LLTF, a frequency-domain CSD may or may not be applied on HTLTF/VHTLTF/HELTF, and a same or different frequency-domain CSD may also be applied on the data field. 
         [0044]    The 1× symbol duration portion of a preamble may be defined per their respective purposes on each 802.11a data tone. For example, the 1× symbol duration portion of preambles may be duplicated over each 20 MHz channel for legacy preamble, RLSIG, and HESIGA, e.g., in a similar way as the omni-directional portion of preamble  220  is duplicated as shown in  FIG. 2 . The 1× symbol duration portion of preamble may be generated by HESIGB coding. 
         [0045]    For example, the 1× symbol duration portion of preamble symbols on the 802.11a guard tones may be empty, e.g., in a similar way as shown in  FIG. 2  where there is no transmission at the guard tones  245 . In another example, at  413 , the 1× symbol duration portion of preamble symbols on the 802.11a guard tones may be filled with known/extended symbols, which may be filled to cover the 4× tone plan. 
         [0046]      FIG. 5  provides an example block diagram illustrating a transmission scheme  500  for the 1× symbol duration portion of a preamble (e.g., see preamble  301  in  FIG. 3 ), according to some embodiments described herein. As shown in  FIG. 5 , in the transmission scheme  500 , the 1× symbol duration portion of preamble fields LSTF  501 , LLTF  502 , LSIG  503 , RLSIG  504 , HESIGA  505 , and HESIGB  506 , have extended 1× preamble symbols  511 - 516 , respectively, to fill the 802.11a guard tones. The extended symbols  511  on LSTF may still follow the frequency density and maintain periodicity. The extended symbols  512  on LLTF may be used for channel estimation. Alternatively, the LSIG/RLSIG/HESIGA/HESIGB extended symbols  513 - 516  may be skipped. Power adjustment may be set on the 1× preambles as needed. 
         [0047]    Back to  FIG. 4 , at  415 , the 1× symbol duration portion of preamble and the 4× symbol duration portion of preamble/data from  403 ,  408  and  413 , respectively, are transmitted to a receiver based on the transmission mode configured in  403 ,  408  and  413 . 
         [0048]    In one implementation, the transmission of the 1× symbol duration portion of preamble may use mixed modes of omni-directional transmission and beamforming transmission. For example, one PPDU may engage the omni-directional transmission, and the next PPDU may engage the beamforming transmission. In this case, the mode of 1× symbol duration portion of preamble may need to be signaled. 
         [0049]    For implicit signaling, when the HESTF does not trigger an AGC change, then the beamforming mode is applied. Or in a different example, a detection on extended symbols indicates the beamformed mode. 
         [0050]    In another implementation, the 1× preamble transmission mode may be implied by the frame format and/or other parameters. For example, single user (SU) and multi-user multiple-input multiple-output (MU-MIMO) frames may imply that a beamformed preamble is used, and an orthogonal frequency-division multiple access (OFDMA) frame may imply that an omni-directional preamble is used. 
         [0051]    In another implementation, even when only a beamformed preamble is used, the receiver may treat the 1× preamble as omni-directional or beamformed based on a decision (e.g., based on the HESTF measurement). 
         [0052]    On the other hand, a variety of explicit signaling may be used to indicate whether a 1× preamble is omni-directional or beamformed. For example, the HESIGA may be configured to contain a bit to signal “omni-directional” and “beamformed” preamble mode. Or a LSIG reserved bit, or LENGTH%3 may be used to signal the preamble mode. In another example, quadrature or binary phase shift keying (QBPSK) rotation may be used on a given 1× preamble symbol, e.g., HESIGA-1, HESIGA-2, or one of the two HESIGBs, to indicate whether the respective 1× preamble symbol is omni-directional or beamformed. In another example, a scrambling sequence on RLSIG may be used to indicate the transmission mode of the respective 1× preamble. In another example, an additional management or control frame can be used to indicate the transmission mode of the respective 1× preamble. It is noted that the implicit signaling and explicit signaling discussed above may be used independently, interchangeably, and/or jointly, when a mixed transmission mode is used to transmit 1× preambles. 
         [0053]    In some implementations, the HESTF field (e.g., see HESTF  308  in  FIG. 3 ) is transmitted without regard for the transmission mode of the 1× preamble mode. Or alternatively, the HESTF data field can be skipped when a beamformed 1× preamble is used. In this case, some new field can be transmitted in place of HESTF. 
         [0054]    In some implementations, the HELTF field (e.g., see HELTF  309  in  FIG. 3 ) is transmitted from the first column of the training matrix A. Or alternatively, the HELTF field may start to transmit with the j th  column of the A matrix being skipped, when using a beamformed 1× preamble and the extended preamble symbols (e.g., as shown in  FIG. 4 ). For example, if j=1, then the HELTF field starts from the 2 nd  column of the A matrix. 
         [0055]      FIG. 6  provides an example logic flow diagram illustrating a receiver processing a received preamble, according to some embodiments described herein. In some implementations, at the receiver, when the 1× symbol duration portion of preamble is received at  601 , the 1× symbol duration portion of preamble may be processed based on the transmission mode, which is detected at  602 . For example, upon detecting a beamformed 1× preamble at  603 , the receiver may skip AGC control directly at  605 . Or alternatively, upon detecting beamformed 1× preamble, the receiver may use an LLTF (e.g., see LLTF  202  in  FIG. 2  and LLTF  311  in  FIG. 3 ) to assist an HELTF channel estimate at  605 . For example, the received LLTF (e.g., field  311  in  FIG. 3 ) and the received first symbol of HELTF (e.g., field  309  in  FIG. 3 ) can be averaged or combined for noise suppression. The receiver may then send the data frame to decoder at  606 , after the beamformed 1× symbol duration portion of preamble has been processed. 
         [0056]    The data frame transmission scheme and signaling methods discussed in  FIGS. 3-6 , although the different modes for 1× preamble are discussed primarily for 802.11ax, can be extended to 802.11n/ac. For example, the implementations discussed in connection with any of the HE fields can also be applied on the corresponding HT/VHT field. The 11n/11ac omni-directional preamble can also be transmitted in beamformed mode. The preamble mode may also be signaled either implicitly or explicitly as described for 11ax. For example, all implicit signaling methods discussed in connection with 802.11ax can be applied for 11n/ac. Explicit signaling can be done by setting reserved bits in LSIG, HTSIG, VHTSIGA, or by setting certain fields to a specific value. 
         [0057]    While this specification contains many specifics, these should not be construed as limitations on the scope of what may be claimed, but, rather, as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
         [0058]    While operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve the desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the aspects described above should not be understood as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
         [0059]    Suitable computer program code residing on a computer-readable medium may be provided for performing one or more functions in relation to performing the processes as described herein. The term “computer-readable medium” as used herein refers to any non-transitory or transitory medium that provides or participates in providing instructions to a processor of the computing device (e.g., the BLE device  106   a - b , the receiving server  105 , or any other processor of a device described herein) for execution. Such a medium may take many forms, including but not limited to non-volatile media and volatile media. Nonvolatile media include, for example, optical, magnetic, or opto-magnetic disks, or integrated circuit memory, such as flash memory. Volatile media include dynamic random access memory (DRAM), which typically constitutes the main memory. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, an EPROM or EEPROM (electronically erasable programmable read-only memory), a FLASH-EEPROM, any other memory chip or cartridge, or any other non-transitory medium from which a computer can read. 
         [0060]    The subject matter of this specification has been described in terms of particular aspects, but other aspects can be implemented and are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous. Other variations are within the scope of the following claims.