Patent Publication Number: US-9408224-B2

Title: Communications coexistence signaling

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/761,605, filed on Feb. 7, 2013, entitled “COMMUNICATIONS COEXISTENCE SIGNALING,” now issued as U.S. Pat. No. 9,131,519, which claims the benefit of U.S. Provisional Application No. 61/740,099, filed Dec. 20, 2012, the entire contents of both of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Many portable electronic devices, especially phone and tablet devices, include circuitry that facilitates communications according to various standards or specifications. For example, a telephone may communicate according to Advanced Mobile Phone (“AMPS”), digital AMPS, Global System for Mobile communications (“GSM”), Code Division Multiple Access (“CDMA”), Local Multi-point Distribution Systems (“LMDS”), Long Term Evolution (“LTE”), Multi-channel-Multi-point Distribution System (MMDS), or other cellular services, and/or variations thereof. The phone may further communicate according to Bluetooth (“BT”) and Wireless Local Area Network (“WLAN”) (e.g., 802.11-based) standards or services, among others. In certain circumstances, the operating frequency bands of cellular, BT, and WLAN communications standards can interfere with each other when used together, leading to communication and/or data loss. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the embodiments and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying figures briefly described as follows: 
         FIG. 1  illustrates a system for communications coexistence according to an example embodiment; 
         FIGS. 2-5  illustrate signal timings between system elements in the system of  FIG. 1  according example embodiments; 
         FIG. 6  illustrates a process flow diagram for communications coexistence according to an example embodiment; 
         FIG. 7  illustrates a process flow diagram of managing first communications in the communications coexistence process of  FIG. 6 , according to an example embodiment; 
         FIG. 8  illustrates a process flow diagram of managing second communications in the communications coexistence process of  FIG. 6 , according to an example embodiment; 
         FIG. 9  illustrates an example embodiment of a coexistence matrix; 
         FIG. 10  illustrates a chart representative of example empirical Rx communications performance according to aspects of the embodiments described herein; 
         FIG. 11  illustrates a chart representative of example empirical Tx communications performance according to aspects of the embodiments described herein; and 
         FIG. 12  illustrates an example schematic block diagram of a computing environment that may be employed in the system of  FIG. 1  according to various embodiments. 
     
    
    
     The drawings illustrate only example embodiments and are therefore not to be considered limiting of the scope described herein, as other equally effective embodiments are within the scope and spirit of this disclosure. The elements and features shown in the drawings are not necessarily drawn to scale, emphasis instead being placed upon clearly illustrating the principles of the embodiments. Additionally, certain dimensions or positions of elements and features may be exaggerated to help visually convey certain principles. In the drawings, similar reference numerals between figures designate like or corresponding, but not necessarily the same, elements. 
     DETAILED DESCRIPTION 
     In the following paragraphs, the embodiments are described in further detail by way of example with reference to the attached drawings. In the description, well known components, methods, and/or processing techniques are omitted or briefly described so as not to obscure the embodiments. 
     The embodiments described herein are not limited in application to the examples set forth in the following description. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” and variations thereof is meant to encompass the identified items, equivalents thereof, and other additional items. The terms “connected” and “coupled” are used broadly to encompass both direct and indirect connections and couplings and are not restricted to physical or mechanical connections or couplings. 
     Many portable electronic devices include communications circuitry that facilitates communications according to various communications standards or specifications. For example, a phone may include cellular, BT, and WLAN radio circuitry, among other circuitry. In certain circumstances, the operating frequency bands of cellular, BT, and WLAN communications standards interfere with each other when used together, leading to communication and/or data loss. In this context, techniques for mitigating interference are described herein. 
     It is noted that, by design, some communications standards are able to automatically mitigate for interference. For example, a BT transceiver can avoid radio interference with other standards by relying upon automatic frequency hopping. Also, at least for certain channels, cellular and WLAN frequencies are sufficiently separated to avoid interference. However, for some channel combinations of certain cellular and WLAN standards, band separation is not sufficient to completely avoid interference. For these cases, cellular band filtering may be relied upon to mitigate interference. In other situations, time-domain coexistence of the cellular and WLAN standards is preferable. 
     Sufficient separation between WLAN frequencies and the XGP band (i.e., 2545-2575 MHz) or band 38 (i.e., 2570-2620 MHz) of the LTE cellular standard may be achieved by using sharp cellular band filters, for example. In another case, separation between WLAN frequencies and band 7 (i.e., 2500-2570 MHz Tx; 2620-2690 MHz Rx) of the LTE standard using sharp cellular band filters may be sufficient for WLAN channels 1-11 (e.g., about 2400-2460 Mhz) but not for WLAN channels 12 and 13 (e.g., greater than about 2460 Mhz). Thus, for separation between LTE band 7 and WLAN channels 12 and 13, time domain separation may be preferable to other separation techniques. Further, even if operating frequencies of communications standards are not directly overlapping, intermodulation products of frequencies of one standard may fall upon frequencies of another standard. 
     It is noted that these examples of band (and band-intermodulation) interference among communications standards are provided by way of example only, as other bands of interference exist today and may arise in the future. In this context, it is noted that future configurations of cellular transceivers may rely upon frequency bands, such as bands in the 2300-2400 MHz range, that encroach upon the Industrial, Scientific, and Medical (“ISM”) frequency bands relied upon by the WLAN standards. 
     In view of the discussion above, a coexistence signaling scheme is described herein to facilitate the operation of various cellular, BT, and WLAN transceivers in a single device. In general, the coexistence signaling scheme comprises a signaling protocol to help mitigate interference between circuitry operating according to different communications standards. 
     Turning now to the drawings, a description of exemplary embodiments of a system and its components are provided, followed by a discussion of the operation of the same. 
       FIG. 1  illustrates a system  10  for communications coexistence according to an example embodiment. The system  10  comprises a device  100 , a WLAN access point  110 , and a base station  120 . In various embodiments, the access point  110  comprises an access point of a WLAN, such as an 802.11-based (e.g., “WiFi”) or 802.16-based (e.g., “WiMax”) wireless network, for example. The communications standard relied upon by the access point  110  is not limited to the 802.11- and 802.16-based standards. Instead, other communications standards are within the scope of the embodiments described herein. It is noted that the access point  110  may be representative of a WLAN comprising several network switches, routers, and access points, in any configuration. In some embodiments, the system  10  further comprises a BT access point  112 . The access point  112  may comprise any BT accessory such as headphones, a headset, a controller, a keyboard, or a pointing device, for example. 
     The base station  120  comprises a station of a cellular-based wireless network. In an exemplary embodiment, the base station  120  comprises a station of an LTE communications network. In various embodiments, however, the base station  120  may comprise a station of any known cellular-based wireless network. As generally described herein, the access point  110  communicates according to a first communications specification, and the base station  120  communicates according to a second to communications specification. As discussed above, the first and second communications specifications may interfere with each other, leading to packet loss and/or disassociation with the access point  110  or the base station  120 . 
     The device  100  comprises a front end  130 , WLAN/BT circuitry  140 , LTE circuitry  150 , and a host controller  160 . The front end  130  comprises RF front end circuitry that supports wireless communications between the device  100  and the access points  110  and  112  and the base station  120 . For example, the front end  130  may comprise one or more antennas, mixers, and duplexers. The front end  130  may further comprise filtering circuitry (e.g., band pass, band stop, and cellular blocking filters) and amplifiers to support wireless communications. It is noted that, in various embodiments, the front end  130  may comprise elements respective to each of the communications standards supported by the device  100 . 
     The host controller  160  executes a host OS  162  and host applications  164 . In general, the host controller  160  coordinates the overall operations of the device  100 , including the operations of the WLAN/BT  140  and the operations of the LTE  150 . Further, although not shown, the host controller  160  may control or coordinate other elements of the device  100  such as a display, a speaker, a microphone, and a camera, for example. As described in further detail below, in one embodiment, the host controller  160  comprises an integrated processor chip having access to one or more memory devices. The host controller  160  is coupled to the WLAN/BT  140  and the LTE  150  via the I/O interface  180 . Via the I/O interface  180 , the host controller  160  communicates various data and signals to the WLAN/BT  140  and the LTE  150 . 
     The WLAN/BT  140  comprises various application layers including layer X  142 , a coexistence layer  144 , and layer Y  146 . The WLAN/BT  140  further comprises a data queue  148 , as further described below. The layers  142 ,  144 , and  146  comprise abstraction layers of a system model of the WLAN/BT  140 . For example, the layers  142 ,  144 , and  146  may be considered similar to layers of the Open Systems Interconnection (“OSI”) model, such as session, transport, and network layers, for example. It is noted that the layers  142  and  146  support and communicate with the coexistence layer  144  and, in various embodiments, may provide session management, flow control, logical and/or physical addressing, or data transmission, among other functions. The layers  142  and  146  are provided by way of example only and are not to be considered limiting, as such layers may be omitted and other layers included in various embodiments. 
     In certain aspects, the coexistence layer  144  is similar to the transport layer of the OSI model, but operates to achieve communications coexistence with the LTE  150  according to a signaling scheme between the WLAN/BT  140  and the LTE  150 . In one aspect, the coexistence layer  144  is configured to establish communications with the access point  110 , identify a priority signal generated by the LTE  150 , and manage communications with one or both of the access points  110  and  112  based on the priority signal. In other aspects, the coexistence layer  144  is configured to analyze a timing pattern of the priority signal, and manage communications with the access point  110  based on the timing pattern. Additionally, the coexistence layer  144  may be configured to generate a relief request signal based on a status of communications with one or both of the access points  110  and  112 . 
     The LTE  150  comprises various application layers including layer X  152 , a coexistence layer  154 , and a layer Y  156 . The LTE  150  further comprises a data queue  158 , as further described below. The layers  152 ,  154 , and  156  comprise abstraction layers of a system model of the LTE  150 . Again, the layers  152 ,  154 , and  156  may be considered similar to layers of the Open Systems Interconnection (OSI) model, such as session, transport, and network layers, for example. It is noted that the layers  152  and  156  support and communicate with the coexistence layer  154  and, in various embodiments, may provide session management, flow control, logical and/or physical addressing, or data transmission, among other functions. The layers  152  and  156  are provided by way of example only and are not to be considered limiting, as such layers may be omitted and other layers included in various embodiments. It is noted that, in alternative embodiments, the data queues  148  and  158  may be implemented by memory devices separate from the WLAN/BT  140  and the LTE  150 , or combined within the host controller  160 . 
     The coexistence layer  154  is similar to the transport layer of the OSI model in certain aspects because it operates to achieve communications coexistence with the WLAN/BT  140  according to the signaling scheme between the WLAN/BT  140  and the LTE  150 . In one aspect, the coexistence layer  154  is configured to establish communications with the base station  120 , forecast data communications with the base station  120 , and generate one or more priority signals based on the forecast. In other aspects, the coexistence layer  154  is configured to identify a relief request signal and manage communications with the base station  120  based on the relief request signal. 
     As described in further detail below, in one embodiment, both the WLAN/BT  140  and the LTE  150  comprise integrated processor chips comprising and/or having access to one or more memory devices. As one example, each comprises an Application Specific Integrated Circuit (“ASIC”) adapted for communications according to one or more communications standards or specifications. 
     As illustrated in  FIG. 1 , the WLAN/BT  140  and the LTE  150  share the communications signals LTE_Tx  170 , LTE_Rx  172 , and WLAN_Relief  174 . In exemplary embodiments, the LTE_Tx  170  and LTE_Rx  172  signals are generated by the LTE  150  and are provided to the WLAN/BT  140 , and the WLAN_Relief  174  signal is generated by the WLAN/BT  140  and is provided to the LTE  150 . 
     According to certain aspects described herein, the communications signals  170 ,  172 , and  174  comprise signals of a coexistence signaling scheme. Communication of the signals  170 ,  172 , and  174  between the WLAN/BT  140  and the LTE  150  may be facilitated by a direct connection between general purpose pins on the WLAN/BT  140  and general purpose pins on the LTE  150 , for each of the signals  170 ,  172 , and  174 , although other means of coupling the signals between the WLAN/BT  140  and the LTE  150  are within the scope of the embodiments described herein. 
     As noted, the WLAN/BT  140  and the LTE  150  are configured to rely upon the signals LTE_Tx  170 , LTE_Rx  172 , and WLAN_Relief  174  as part of a coexistence signaling scheme. In that context, the WLAN/BT  140  and the LTE  150  may be configured to generate, identify, and act upon the LTE_Tx  170 , LTE_Rx  172 , and WLAN_Relief  174  signals. In general, the coexistence signaling scheme is relied upon by the device  100  to facilitate the coexistence of communications standards that may otherwise interfere with each other. 
     According to one embodiment, the LTE_Tx  170  signal indicates to the WLAN/BT  140  that a transmission by the LTE  150  is scheduled to occur within a certain predetermined time. After identifying an edge of the LTE_Tx  170  signal, the WLAN/BT  140  is configured to suspend its communications with the access point  110 . By suspending its communications, the WLAN/BT  140  may prevent desensitization of its receiver caused by an LTE transmission, for example. The suspension of communications may involve the transmission of one or more 802.11-based protocol commands or messages from the WLAN/BT  140  to the access point  110 . In one embodiment, the WLAN/BT  140  may suspend communications with the access point  110  by entering a power-save or power-management mode. In general, receiver desensitization occurs when a receiver is directly (or by intermodulation) frequency-overlapped by transmission frequencies of other communication circuit(s), effectively jamming the receiver. 
     As further discussed below with reference to  FIG. 9 , assertion of the LTE_Tx  170  signal by the LTE  150  may be based in part upon a coexistence matrix that identifies when certain intermodulation conditions are met between the WLAN/BT  140  and the LTE  150 . The intermodulation conditions may depend upon which LTE channel is being relied upon for transmission (e.g., LTE band 7 vs. band 38), for example. 
     The LTE_Rx  172  signal indicates to the WLAN/BT  140  that a signal is scheduled to be received by the LTE  150  within a certain predetermined time. After identifying an edge of the LTE_Rx  172  signal, the WLAN/BT  140  is configured to reduce a transmission power of transmissions (or suspend transmissions) to the access point  110 . In this manner, the WLAN/BT  140  can prevent or reduce intermodulation products, for example, from falling on a receiver of the LTE  150 . As further discussed below, assertion of the LTE_Rx  172  by the LTE  150  may be based in part upon a coexistence matrix that identifies when certain intermodulation conditions are met between the WLAN/BT  140  and the LTE  150 . The intermodulation conditions may depend upon which WLAN channel is being relied upon for transmission (e.g., WLAN channel 6 vs. 11), for example. 
     In one embodiment, the WLAN_Relief  174  signal indicates a distress condition of the WLAN/BT  140  to the LTE  150 . For example, if transmissions by the LTE  150  have been active with a high duty cycle for a significant period of time and WLAN throughput over this time period has been low, the data queue  148  of the WLAN/BT  140  may be full. Thus, the WLAN_Relief  174  signal may indicate that it is necessary for the WLAN/BT  140  to transfer data. In another case, for example, when transmitting a probe request message to discover surrounding WLAN access points, the WLAN_Relief  174  signal may be asserted to prevent the LTE  150  from transmitting over any Probe Response signals received from the surrounding WLAN access points in response to the probe request message. In this case, the WLAN_Relief  174  signal may be asserted for a predetermined period of time, such as 6 ms, for example, to prevent the LTE  150  from corrupting the reception of any Probe Request signals, as this may lead to a failure of access point discovery. 
     In other cases, a data queue of the access point  110  may be full. The data queue of the access point  110  may be full due to a power management mode of operation. In the power management mode, the WLAN/BT  140  indicates to the access point  110  that the WLAN/BT  140  is entering a “sleep” state for a certain period of time. During this sleep time, the access point  110  may buffer data in a data queue to be transmitted to the WLAN/BT  140  at a later time. At certain intervals, it is necessary for the WLAN/BT  140  to “wake” for the receipt of an Announcement Traffic Indication Message (“ATIM”) beacon from the access point  110 . Within the beacon, the access point  110  identifies whether data is buffered for communication to the WLAN/BT  140 . If the WLAN/BT  140  does not acknowledge the ATIM beacon, for example, data stored in the access point  110  may be deleted or overwritten by the access point  110 . This condition may result in a rate fallback adaptation by the access point  110 . That is, the access point  110  may determine that the WLAN/BT  140  cannot facilitate communications at a certain data rate, and select a lower rate for communications. In other cases, the access point  110  may disassociate with the WLAN/BT  140 . In view of these considerations, the WLAN/BT  140  may assert the WLAN_Relief  174  signal to indicate a distress condition to the LTE  150 . 
       FIGS. 2-5  illustrate signal timings of the LTE_Tx  170 , LTE_Rx  172 , and WLAN_Relief  174  signals between the WLAN/BT  140  and LTE  150 , according example embodiments. At the outset, it is noted that the signal timings are not necessarily drawn to scale. Further, logic levels different from those illustrated may be relied upon in various embodiments, as one would recognize that the level(s) used to represent certain logic states can be arbitrarily selected. 
     Turning first to  FIG. 2 , example timings of the LTE_Tx  170  signal are illustrated. At edge  210 , the LTE_Tx  170  signal transitions from a low to a high logic level. According to one embodiment, the transition from the low to high logic level is specified to occur “A” ms before an actual UL (i.e., transmission) by the LTE  150 . In one embodiment, the period “A” is specified as 2 ms, although other periods are within the scope of the embodiments described herein. As illustrated, the actual LTE UL begins at some time at or after the period “A,” and the LTE_Tx  170  signal remains at the logic high level until the edge  220 , when the actual LTE UL concludes. According to certain aspects of the coexistence signaling scheme, a time period of “n” μs is attributed or expected for jitter between edges. According to other aspects, the LTE_Tx  170  signal is asserted only if the LTE  150  is scheduled to transmit data, and the LTE_Tx  170  signal shall remain at the logic high state if an LTE UL is scheduled in consecutive subframes. 
     Upon identification of the edge  210 , the WLAN/BT  140  may perform certain tasks, update or adapt communications parameters, and suspend WLAN communications. The WLAN/BT  140  may transmit one or more 802.11-based protocol commands or messages from the WLAN/BT  140  to the access point  110  during the time period “A”, with or without the transmission of data. For example, the WLAN/BT  140  may transmit data in connection with a CTS-to-Self announcement. According to certain WLAN protocol standards, the WLAN/BT  140  may specify a certain time period during which it plans to transmit data, using a CTS-to-Self announcement. By doing so, the WLAN/BT  140  may effectively squelch communications by other nodes in the WLAN network, in favor of itself. 
     At the conclusion of data transmission accompanied by a CTS-to-Self announcement (or without the announcement), the WLAN/BT  140  may exchange one or more WLAN media access control protocol messages for maintenance of communications between the WLAN/BT  140  and the access point  110 . For example, the WLAN/BT  140  may indicate to the access point  110  that it is entering a power management sleep mode, according to power management protocol commands. Thus, it is noted that the WLAN/BT  140  may perform certain communication and housekeeping tasks within “A” ms of the edge  210 , before suspending communications. It is noted that, in some embodiments, the “suspension” of communications may include the suspension of data transmission, data reception, or both data transmission and reception. 
     Turning to  FIG. 3 , other timing aspects of the LTE_Tx  170  signal are illustrated. As illustrated, the LTE_Tx  170  signal comprises an exception pulse  310  of short (e.g., 10 μs) logic-low duration. According to one embodiment, the exception pulse  310  signifies the conclusion of a first LTE UL, with a second LTE UL scheduled to occur “A2” ms from the conclusion of the first LTE UL. Here, the period of time “A2” is less than “A”. Thus, the exception pulse  310  indicates to the WLAN/BT  140  that a period of time, although less than the time period “A”, is available for communications. For example, the period of time may be sufficient for the WLAN/BT  140  to receive a beacon from the access point  110 , such as an ATIM beacon, and transmit an acknowledgement. This time may be sufficient to maintain association with the access point  110  and prevent rate fallback or disassociation. In certain cases, the WLAN/BT  140  can communicate data during a time period indicated by the exception pulse  310 . It is noted that, according to certain protocol considerations and limitations, the WLAN/BT  140  may be able to make use of time periods as short as 500 μs or shorter. Also, in certain embodiments, the timings of the LTE_TX  170  signal specify that the LTE  150  generates the exception pulse  310  only when the second LTE UL is scheduled a certain minimum time period after conclusion of the first LTE UL. As such, the period “A2” may comprise a minimum time period such as 1 or 1.2 ms, for example. 
     Turning to  FIG. 4 , timing aspects of the LTE_Rx  172  signal are illustrated. At edge  410 , the LTE_Rx  172  signal transitions from a low to high logic level. According to one embodiment, the transition from the low to high logic level is specified to occur “B” μs before a scheduled DL (i.e., reception) by the LTE  150 . In one embodiment, the period “B” is specified as 200 μs, although other periods are within the scope of the embodiments described herein. As illustrated, the actual LTE DL begins at some time at or after the period “B,” and the LTE_Rx  172  signal remains at the logic high level until the edge  420 , when the actual LTE DL concludes. Again, according to certain aspects of the coexistence signaling scheme, a time period of “n” μs is attributed or expected for jitter between edges. 
     As discussed above, the WLAN/BT  140  is configured to reduce the power of transmissions (or suspend transmissions) to the access point  110  by “B” μs after the edge  410 . In this manner, the WLAN/BT  140  can prevent or reduce intermodulation products, for example, from falling on a receiver of the LTE  150 . Assertion of the LTE_Rx  172  signal by the LTE  150  may be based in part upon a coexistence matrix that identifies when certain intermodulation conditions are met between the WLAN/BT  140  and the LTE  150 . 
     According to certain embodiments, the LTE_Rx  172  signal shall remain at a logic high state if an LTE DL is scheduled in consecutive subframes or frames. In other aspects, the LTE_Rx  172  signal shall be asserted by the LTE  150  only if it must protect certain LTE channels, such as the physical downlink control channel (“PDCCH”) or physical downlink shared channel (“PDCCH”), over an entire LTE DL period. For example, the LTE_Rx  172  signal may be asserted by the LTE  150  to protect the PDCCH channel until the LTE  150  determines that there is no data allocated for DL in a current subframe. 
     Turning to  FIG. 5 , timing aspects of the WLAN_Relief  174  signal are illustrated. At edge  510 , the WLAN_Relief  174  signal transitions from a low to high logic level. In response to the WLAN_Relief  174  signal, the LTE  150  is configured to conclude any LTE UL communications within “C” μs of the edge  510 . In one embodiment, the period “C” is specified as 10 μs, although other periods are within the scope of the embodiments described herein. According to other timing aspects, the logic high level of the WLAN_Relief  174  signal may continue for, at most, “D” ms, until edge  520 . The period “D” may be specified based on a length of one or more WLAN packets, for example. In one embodiment, the period “D” is specified as 1.2 ms, although other periods are within the scope of the embodiments described herein. Again, according to certain aspects of the coexistence signaling scheme, a time period of “n” μs is attributed or expected for jitter between edges. 
     In certain embodiments, it is optional for the LTE  150  to adhere to the timing requirements specified by the WLAN_Relief  174  signal. That is, the LTE  150  may not conclude or cease LTE UL communications within “C” μs of the edge  510 , depending upon operating conditions and priorities of the LTE  150 . For example, depending upon an amount of data stored in the data queue  158 , the LTE  150  may continue to transmit data without adhering to the timing requirements specified by the WLAN_Relief  174  signal. 
     As described above, the WLAN/BT  140  may assert the WLAN_Relief  174  signal to indicate a distress condition to the LTE  150 . It may be necessary for the LTE  150  to conclude UL communications to prevent rate fallback adaptation by the access point  110  or one of the layers  142  or  146  of the WLAN/BT  140 . In other cases, it may be necessary for the LTE  150  to conclude UL communications so that the WLAN/BT  140  can receive beacons and prevent disassociation between the access point  110  and the WLAN/BT  140 . 
     Before turning to the process flow diagrams of  FIGS. 6-8 , it is noted that the embodiments described herein may be practiced using an alternative order of the steps illustrated in  FIGS. 6-8 . That is, the process flows illustrated in  FIGS. 6-8  are provided as examples only, and the embodiments may be practiced using process flows that differ from those illustrated. Additionally, it is noted that not all steps are required in every embodiment. In other words, one or more of the steps may be omitted or replaced, without departing from the spirit and scope of the embodiments. Further, steps may be performed in different orders, in parallel with one another, or omitted entirely, and/or certain additional steps may be performed without departing from the scope and spirit of the embodiments. 
       FIG. 6  illustrates a process flow diagram for communications coexistence according to an example embodiment. While the process below is described in connection with the elements of the system  10  of  FIG. 1 , the process may be implemented by other system elements. 
     As illustrated, the process  600  comprises a first communications process including  610 ,  620 , and  630 , and a second communications processing including  640 ,  650 , and  660 . In one embodiment, the first communications process comprises a BT, WLAN, or combination WLAN/BT communications process, and the second communications process comprises a cellular LTE communications process. In should be appreciated, however, that the process  600  may apply to other combinations of communications standards. 
     At  610 , first communications are established, for example, between the WLAN/BT  140  and one or both of the access points  110  and  112  of  FIG. 1 . That is, association may be achieved between the WLAN/BT  140  and one or both of the access points  110  and  112  at  610 . At  620 , the WLAN/BT  140  receives data for transmission from the host controller  160 . The data for transmission may be generated by one or more of the host OS  162  or the host applications  164 , for example. At  630 , the WLAN/BT  140  manages the first communications with one or both of the access points  110  and  112 . According to the features and aspects described above, while managing the first communications at  630 , the WLAN/BT  140  operates according to various signals of a coexistence signaling scheme. 
     At  640 , second communications are established, for example, between the LTE  150  and the base station  120  of  FIG. 1 . At  650 , the LTE  150  receives data for transmission from the host controller  160 . The data for transmission may be generated by one or more of the host OS  162  or the host applications  164 , for example. At  660 , the LTE  150  manages the second communications with the base station  120 . According to the features and aspects described above, while managing the first communications at  660 , the LTE  150  operates according to various signals of the coexistence signaling scheme. 
       FIG. 7  illustrates a process flow diagram of the managing first communications  630  of  FIG. 6 , according to an example embodiment. At  710 , a first protocol timing is determined by the WLAN/BT  140 . That is, the WLAN/BT  140  determines and settles on a schedule of communications for transmitting the data received at  620  of  FIG. 6  to one or more of the access points  110  and  112  of  FIG. 1 . The first protocol timing may be determined in connection with conditions and requirements evaluated by the layers  142  and  146  of the WLAN/BT  140 , for example, which may include session management and flow control. 
     At  712 , the WLAN/BT  140  conducts communications with one or more of the access points  110  and  112  according to the first protocol timing determined at  710 . In general, communications continue at  712  until certain events occur based on the logic levels of the coexistence signals, for example, or another changed circumstance. At  714 , the WLAN/BT  140  identifies a transition of one or more of the coexistence signals, such as the LTE_Tx  170  or LTE_Rx  172  signals. 
     At  716 , the WLAN/BT  140  analyzes one or more of the LTE_Tx  170  and LTE_Rx  172  signals to determine logic levels of the signals, for example. According to certain aspects, the WLAN/BT  140  analyzes patterns of the LTE_Tx  170  and LTE_Rx  172  signals to ascertain operating parameters and modes of the LTE  150 . If the WLAN/BT  140  determines that the LTE_Tx  170  signal is typically asserted by the LTE  150  in a certain pattern, for a certain period of time, or for a certain average period of time, the WLAN/BT  140  may update one or more parameters of communication with the access points  110  and  112  at reference  718 , based on the determination. As one example, if the WLAN/BT  140  determines that the LTE_Tx  170  signal is typically asserted for periods of time less than 2 ms, the WLAN/BT  140  may update one or more parameters to communicate using CTS_to_Self announcements. Otherwise, if the WLAN/BT  140  determines that the LTE_Tx  170  signal is typically asserted for periods of time greater than 2 ms, the WLAN/BT  140  may update substantially rely upon the WLAN power management mode for scheduling. 
     As suggested above, at  718 , the WLAN/BT  140  updates one or more parameters of the first communications and controls the first communications, according to various considerations including an amount of data to be transmitted, the first protocol timings, the identification of a transition on one or more of the coexistence signals at  714 , and the analysis at  716 . As outlined above in connection with the signal timing diagrams of  FIGS. 2-4 , the WLAN/BT  140  may suspend the first communications based on the LTE_Tx  170  signal, reduce a WLAN transmission power based on the LTE_Rx  172  signal, communicate in connection with a CTS-to-Self announcement, and/or indicate that it is entering a power management sleep mode. In exemplary embodiments, the control of the first communications is performed by the WLAN/BT  140  at  718  substantially in accordance with the timing specifications outlined in  FIGS. 2-4 . 
     Further, at  718 , aspects of the first communications may be updated in connection with conditions and requirements evaluated by the layers  142  and  146  of the WLAN/BT  140 , based on the identification of a transition on one or more of the coexistence signals at  714  and the analysis at  716 . For example, an alternate WLAN communications channel or communications rate may be selected based on the identification of a transition on one or more of the coexistence signals at  714  and the analysis at  716 . Additionally, the WLAN/BT  140  may manage the coexistence of both BT and WLAN communications, according to an internal WLAN/BT coexistence protocol. Parameters and timings among the BT and WLAN communications may also be updated at  718  based on the identification of a transition on one or more of the coexistence signals at  714  and the analysis at  716 . 
     Continuing from  718 , the process  630  includes determining whether WLAN/BT communications are in distress at  720 . For example, if transmissions by the LTE  150  have been active with a high duty cycle for a significant period of time and WLAN throughput over this time period has been low, either the WLAN/BT  140  or the access point  110  may have required automatic rate fallback pursuant to the perception of a poor communications link. In this case, the WLAN/BT  140  may identify a distress condition at  720  and generate a logic high level on the WLAN_Relief  174  signal at  722 . The logic high level on the WLAN_Relief  174  signal is coupled to the LTE  150  as described herein. It is noted that the WLAN/BT  140  may identify a distress condition at  720  for reasons other than rate fallback, such as to avoid disassociation or prevent packet loss. 
     Also continuing from  718 , the process  630  includes determining whether “coexistence” packet loss has occurred at  724 . For example, if packet loss occurs due to the suspension of communications by the WLAN/BT  140  in response to the LTE_Tx  170  signal, the coexistence layer  144  of the WLAN/BT  140  may indicate to one or both of the layers  142  and  146  that the packet loss is a “coexistence” packet loss at reference  726 . In other words, the layers  142  and  146  may distinguish packets lost due to the coexistence signaling scheme as being different than packets lost due to generally poor channel conditions. This distinction may result in alternate session management and flow control by the layers  142  and  146  depending upon the type of packet loss. 
     Turning to  FIG. 8 , a process flow diagram of the managing second communications  660  of  FIG. 6  is illustrated, according to an example embodiment. At  810 , a second protocol timing is determined by the LTE  150 . That is, the LTE  150  determines and settles on a schedule of communications for transmitting the data received at  650  of  FIG. 6  to the base station  120  of  FIG. 1 . The second protocol timing may be determined in connection with conditions and requirements evaluated by the layers  152  and  156  of the LTE  150 , for example, which may include session management and flow control. 
     At  812 , the LTE  150  conducts communications with the base station  120  according to the second protocol timing determined at  712 . In general, communications continue at  812  until certain events occur based on the logic levels of the coexistence signals, for example, or another changed circumstance. At  814 , the LTE  150  identifies a transition of one or more of the coexistence signals, such as the WLAN_Relief  174  signal. 
     At  816 , the LTE  150  updates one or more parameters of the second communications and controls the second communications, according to various considerations including an amount of data to be transmitted, the second protocol timings, and the identification of a transition on the WLAN_Relief  174  signal at  814 . As outlined above, the LTE  150  may suspend the second communications based on the WLAN_Relief  174  signal, in accordance with the timing specification outlined in  FIG. 5 , or update other communications parameters. Further, at  816 , parameters of the second communications may be updated in connection with conditions and requirements evaluated by the layers  152  and  156  of the LTE  150 , based on the identification of a transition on the WLAN_Relief  174  signal. For example, an alternate LTE communications channel, protocol timing, or reduced transmission power may be selected by the LTE  150  based on the identification of a transition on the WLAN_Relief  174  signal. 
     Continuing from  816 , the process  660  includes forecasting the second communications at  818 . For example, LTE UL and DL timings may be forecast based on the second protocol timing determined at  810 . This “look-ahead” is achieved by the LTE  150  based on a determined schedule of Tx and Rx timings negotiated between the LTE  150  and the base station  120 . 
     At  820 , the LTE  150  determines if a transmission is forecasted. If so, the LTE  150  generates a logic high level on the LTE_Tx  170  signal at  822 . Further, at  824 , the LTE  150  determines if a reception is forecasted. If so, the LTE  150  generates a logic high level on the LTE_Rx  172  signal at  826 . The logic levels on the LTE_Tx  170  and the LTE_Rx  172  signals are coupled to the WLAN/BT  140  as described herein. It is noted that, in exemplary embodiments, the generation of a logic high level on the LTE_Tx  170  signal and/or the LTE_Rx  172  signal is conditioned upon factors in addition to the forecast determined at  818 . For example, the generation of a logic high level on the LTE_Tx  170  signal and/or the LTE_Rx  172  signal may also be conditioned upon overlapping channel or intermodulation conditions, as described below. 
       FIG. 9  illustrates an example embodiment of a coexistence matrix  900 . As one aspect of the embodiments described herein, a coexistence matrix may be generated and stored in one or more of the WLAN/BT  140 , the LTE  150 , or the host controller  160 . The coexistence matrix generally identifies when certain intermodulation conditions exist between the WLAN/BT  140  and the LTE  150 . For example, the intermodulation conditions may depend upon which LTE channel is being relied upon by the WLAN/BT  140  (e.g., WLAN channel 6 vs. 11) and the LTE  150  (e.g., LTE band 7 vs. band 38). It is noted that the coexistence matrix  900  may be generated by any or each of the WLAN/BT  140 , the LTE  150 , and the host controller  160  and stored, in any data format, by any or each of the WLAN/BT  140 , the LTE  150 , and the host controller  160 . 
     To generate the coexistence matrix  900 , overlapping channel (or intermodulation) combinations or conditions between communications by the WLAN/BT  140  and the LTE  150  may be ascertained. In certain cases, those overlapping channel combinations depend, in part, on circuit board parasitics in the device  100  and the tolerances of the circuit elements mounted to the circuit boards. Thus, after manufacture, the device  100  may be tested and characterized to determine or ascertain certain offending combinations or conditions between communications by the WLAN/BT  140  and the LTE  150 . In some cases, these offending combinations or conditions may change over time, such as with temperature drift, and the device  100  may update the coexistence matrix  900  periodically based on those changes. 
     Referring to the coexistence matrix  900 , both WLAN and LTE “Rx protect” conditions are specified. For the LTE 2530 Mhz and WLAN Channel 1 combination, the coexistence matrix  900  specifies protection of LTE Rx. Here, generation of the LTE_Rx  172  signal by the LTE  150  may be conditioned (additionally) upon the overlapping channel combination of LTE 2530 Mhz and WLAN Channel 1. Thus, while assertion of the LTE_Rx  172  signal by the LTE  150  is dependent upon a timing of LTE Rx, the assertion may also be dependent upon the overlapping channel combinations indicated in the coexistence matrix  900 . 
     Alternatively, for the LTE 2510 Mhz and WLAN Channel 12 combination, the coexistence matrix  900  specifies protection of WLAN Rx. Here, generation of the LTE_Tx  170  signal by the LTE  150  may be conditioned (additionally) upon the overlapping channel combination of LTE 2510 Mhz and WLAN Channel 12. Thus, while assertion of the LTE_Tx  170  signal by the LTE  150  is dependent upon a timing of LTE Tx, the assertion may also be dependent upon the overlapping channel combinations indicated in the coexistence matrix  900 . 
       FIG. 10  illustrates a chart representative of example empirical Rx communications performance according to aspects of the embodiments described herein. In  FIG. 10 , a measure of WLAN Rx throughput is illustrated for baseline WLAN Rx communications, for WLAN Rx communications with simulated coexistence signals and without band 7 jamming, for WLAN Rx communications with coexistence signals and band 7 jamming, and for WLAN Rx communications without coexistence signals and with band 7 jamming. As illustrated, the use of coexistence signals with band 7 jamming offers a significant improvement in WLAN Rx throughput as compared to WLAN Rx communications without the use of coexistence signals, especially between the received signal strength range of about −77 to −67 dBm. 
       FIG. 11  illustrates a chart representative of example empirical Tx communications performance according to aspects of the embodiments described herein. In  FIG. 11 , a measure of WLAN Tx throughput is illustrated for baseline WLAN Tx communications, for WLAN Tx communications with coexistence signals and band 7 jamming, and for WLAN Tx communications without coexistence signals and with band 7 jamming. As illustrated, the use of coexistence signals with band 7 jamming offers no significant reduction in WLAN Tx throughput as compared to WLAN Tx communications without the use of coexistence signals. It is noted that, because the coexistence signaling scheme generally prefers communication by the cellular standard over the WLAN standard, no appreciable impact to cellular communications is anticipated by the scheme. 
       FIG. 12  illustrates an example schematic block diagram of a computing environment  1200  that may be employed in the system of  FIG. 1  according to various embodiments. The device  100  of  FIG. 1  may be implemented, at least in part, based on the elements of the computing environment  1200 . The computing environment  1200  comprises various processing circuits or processors including processors  1202 ,  1204 , and  1206 , a memory (or memories)  1210 , and a local interface  1220 . The local interface  1220  may comprise, for example, a data bus with an accompanying address/control bus or other bus structure as can be appreciated. 
     The processors  1202 ,  1204 , and  1206  may represent multiple processors and/or multiple processor cores and the memory  1210  may represent multiple memories that operate in parallel processing circuits, respectively or in combination. In one embodiment, the processors  1202 ,  1204 , and  1206  can be implemented as general purpose processors, circuits, state machines, or combinations thereof that employ any one of or a combination of technologies. These technologies may include, but are not limited to, discrete logic circuits having logic gates for implementing various logic functions upon an application of one or more data signals, ASICs having appropriate logic gates, field-programmable gate arrays (FPGAs), or other components, etc. Such technologies are generally well known by those skilled in the art and, consequently, are not described in detail herein. 
     In various embodiments, the memory  1210  stores data and software or executable-code components executable by the processors  1202 ,  1204 , and  1206 . For example, the memory  1210  may store data and software or executable-code components associated with the abstract layers  142 ,  144 ,  146 ,  152 ,  154 , and  156 , the data queues  148  and  158 , and the host OS  162  and applications  164 . Where any component discussed herein is implemented in the form of software, any one of a number of programming languages may be employed such as, for example, C, C++, C#, Objective C, Java®, JavaScript®, Perl, PHP, Visual Basic®, Python®, Ruby, Flash®, or other processor-specific or proprietary programming languages. 
     As discussed above, the memory  1210  stores software for execution by the processors  1202 ,  1204 , and  1206 , along with other data. In this respect, the terms “executable” or “for execution” refer to software forms that can ultimately be run or executed by the processors  1202 ,  1204 , and  1206 , whether in source, object, machine, or other form. Any of the processors  1202 ,  1204 , and  1206  may retrieve executable code stored in the memory  1212  and, based on the execution of that code, be directed to implement any one or more of the processes described above in connection with  FIGS. 6-8 , for example. 
     In various embodiments, the memory  1210  may include both volatile and nonvolatile memory and data storage components. Volatile components are those that do not retain data values upon loss of power. Nonvolatile components are those that retain data upon a loss of power. Thus, the memory  1210  may comprise, for example, a random access memory (RAM), read-only memory (ROM), magnetic or other hard disk drive, solid-state, semiconductor, or similar drive, USB flash drive, memory card, floppy disk, optical disc, magnetic tape, and/or other memory component, or any combination thereof. In addition, the RAM may comprise, for example, a static random access memory (SRAM), dynamic random access memory (DRAM), or magnetic random access memory (MRAM), and/or other similar memory device. The ROM may comprise, for example, a programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other similar memory device. 
     Although embodiments have been described herein in detail, the descriptions are by way of example. The features of the embodiments described herein are representative and, in alternative embodiments, certain features and elements may be added or omitted. Additionally, modifications to aspects of the embodiments described herein may be made by those skilled in the art without departing from the spirit and scope of the present invention defined in the following claims, the scope of which are to be accorded the broadest interpretation so as to encompass modifications and equivalent structures.