Abstract:
Embodiments of voice signaling latency reduction mechanisms are described generally herein. Other embodiments may be described and claimed.

Description:
TECHNICAL FIELD  
       [0001]     Various embodiments described herein relate to digital communications generally, including apparatus, systems, and methods used in packet-switched wireless voice communications.  
       BACKGROUND INFORMATION  
       [0002]     Digital voice communications may be implemented in a packet-switched network. Methods associated with two such implementations may include those defined in voice over Internet protocol (VoIP) specifications H.323 and Internet Engineering Task Force (IETF) Request for Comments (RFC) 2543. Additional information regarding H.323 may be found in International Telecommunication Union (ITU) Standard H.323—Version 5 “Packet-based Multimedia Communications Systems” (July 2003). Additional information regarding a session initiation protocol (SIP) may be found in IETF RFC 2543, “SIP: Session Initiation Protocol” (1999).  
         [0003]     H.323 and session initiation protocol definitions may include voice signaling methods such as initiating, modifying, and terminating a voice call. Signaling traffic may be present on a link whether or not active voice traffic is present on the link, and can be sensitive to delay. While voice packets may be sent using a real-time protocol, perhaps implemented with a user datagram protocol, signaling packets are usually sent through a transport control protocol.  
         [0004]     These factors may be particularly significant as they relate to wireless packet transmission methods such as those incorporated in an Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard and in an IEEE 802.11E standard. Additional information regarding the IEEE 802.11 standard may be found in “ANSI/IEEE Std. 802.11, Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications” (published 1999; reaffirmed June 2003). Additional information regarding the IEEE 802.11E standard may be found in “IEEE 802.11E Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Amendment  8 : Medium Access Control (MAC) Quality of Service Enhancements (published 2005).  
         [0005]     Voice and signaling packets may be prioritized differently according to quality of service (QoS) methods defined in the 802.11E standard. Voice packets may be sent with an access category-voice (AC-VO) channel access category that is prioritized relatively higher than an access category-video (AC-VI) channel access category used for voice signaling.  
         [0006]     Such differential prioritization of voice and signaling packets may be considered together with a state of reduced power consumption referred to as a power-save mode of operation. The power-save mode of operation may be utilized by a battery-powered wireless device to extend an operating time between battery recharge cycles.  
         [0007]     A particular type of power-save mode of operation referred to as an automatic power-save delivery (APSD) mode is described in the IEEE 802.11E standard. APSD is a mechanism for delivery of downlink frames from a wireless access point operating in a QoS mode (a “QAP”) to a station (STA) operating in both the QoS mode and in the power-save mode (a “QSTA”). Although two APSD sub-modes are described, scheduled and unscheduled, the unscheduled or “triggered” (U-APSD) mode may predominate in commercial applications.  
         [0008]     A QSTA operating in the U-APSD mode may awaken periodically for a service period of time. A service period is a contiguous period of time during which a set of one or more downlink frames is sent to one or more QSTAs.  
         [0009]     The IEEE 802.11E specification defines two attributes associated with access category traffic, trigger-enabled access category and delivery-enabled access category. Trigger-enabled access category refers to an attribute associated with traffic in the uplink. A packet in the uplink associated with a trigger-enabled access category may trigger an unscheduled service period if one is not already in progress. When an access category associated with a QAP is delivery-enabled, the QAP may be allowed to deliver traffic associated with the access category to a QSTA in an unscheduled service period triggered by the QSTA.  
         [0010]     An unscheduled service period may begin when the QAP receives a QoS-data packet (e.g., a prioritized voice packet or a prioritized voice signaling packet) or a QoS-null packet associated with an active access category in the uplink. An access category may be thought of as a level of priority associated with a particular class of traffic. The unscheduled service period may end when the QSTA receives a QoS data packet or a QoS null packet with an end of service period (EOSP) subfield set to 1 in the downlink. Once the QAP has received an acknowledgment to the latter packet, the QAP ceases transmission of packets to the QSTA using this mechanism until the next service period. Unscheduled APSD thus requires a traffic stream of QoS data or QoS null packets in the uplink to trigger a transmission of traffic in the downlink.  
         [0011]     The QAP may buffer delivery enabled traffic until it receives a packet from the QSTA associated with a trigger enabled access category. The QAP may then transmit the buffered packets to the QSTA. Buffered traffic associated with an access category with a U-APSD attribute set to “non-delivered” may continue to be buffered at the QAP and may not be forwarded to the QSTA upon a receipt at the QAP of the packets associated with the trigger-enabled AC. The QAP may notify the QSTA about buffered non-delivered traffic using a deliver traffic information message (TIM) in a beacon packet associated with a standard, non-APSD power-save mode of operation. A TIM may not be set for traffic associated with a delivered traffic access category unless all ACs are delivery enabled, however. The QSTA should thus use upstream traffic to trigger a delivery of traffic from the QAP buffer.  
         [0012]     A problem with using VoIP with U-APSD may result from the fact that that the 802.11E standard was designed with voice streams in mind, but does not necessarily define how the QSTA can receive unexpected downstream signaling traffic to initiate a voice stream. Although static access category configurations may be implemented, these may result in large delays to signaling traffic and/or increased power consumption when coupled with APSD use. A user may experience symptoms of a bad call connection attempt (e.g., an “other side not available” or a “line broken” indication). 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a block diagram of an apparatus and a representative system according to various embodiments.  
         [0014]      FIG. 2  is a flow diagram illustrating several methods according to various embodiments.  
         [0015]      FIG. 3  is a block diagram of an article according to various embodiments. 
     
    
     DETAILED DESCRIPTION  
       [0016]      FIG. 1  comprises a block diagram of an apparatus  100  and a system  180  according to various embodiments of the invention. The apparatus  100  and the system  180  may dynamically switch a power saving mode of operation between a legacy power-save mode and an APSD mode based upon whether or not a voice packet stream is pending transmission. Lower latencies associated with downlink voice signaling traffic may result.  
         [0017]     A dynamic configuration mechanism may be established to change a U-UPSD state affecting voice signaling traffic at a beginning of a voice stream and again at an end of the voice stream. When a VoIP application  108  initializes in a wireless portable electronic device (WPED)  112 , the application  108  may open a voice signaling traffic stream. The WPED  112  may comprise a personal digital assistant, a handheld computer, a laptop computer, or a mobile telephone, among other wireless portable electronic devices.  
         [0018]     The voice signaling traffic stream may traverse an uplink  114  from a wireless communication module (WCM)  116  associated with the WPED  112  to a wireless access point  124 . The VoIP application  108  may configure an AC-VI associated with voice signaling traffic in a downlink  126  as non-APSD. In this mode, voice signaling traffic may be delivered to the WCM  116  according to a legacy power-save mode of operation. That is, the wireless access point  124  may buffer voice signaling packets for the WPED  112  while the WCM  116  operates in the power save mode. The wireless access point  124  may send a notification to the WCM  116  as to an availability of buffered voice signaling traffic in a TIM field of a beacon packet. The WCM  116  may wake up periodically to retrieve the TIM indication and to receive the signaling traffic.  
         [0019]     When the VoIP application  108  opens a voice call and sends a voice stream to the WCM  116  for transmission, some embodiments may configure an AC-VO as trigger-enabled and delivery-enabled by sending an add traffic stream (ADDTS) control packet. The AC-VI may also be re-configured to a delivery-enabled APSD mode. With the link thus configured to operate in the APSD mode, the WCM  116  may transmit the voice stream in the uplink  114 . The voice stream in the uplink  114 , corresponding to the AC-VO, may trigger a delivery of buffered packets in the downlink  126 . That is, the wireless access point  124  may transmit both buffered voice packets and buffered voice signaling packets, if any, in the downlink  126 . Both voice traffic and signaling traffic may be sent in the downlink  126 , since both AC-VO and AC-VI are enabled.  
         [0020]     When the VoIP application  108  ends the voice call, some embodiments may re-configure both the AC-VI and the AC-VO as non-APSD. The re-configuration may be accomplished by sending a delete traffic stream (DELTS) control packet, with a U-APSD parameter reset, to the wireless access point  124  for each AC. Following a receipt of the DELTS packets, signaling traffic may be delivered to the WCM  116  using legacy power-save methods.  
         [0021]     Some embodiments may thus transition from an APSD mode of power-saving operation to a legacy power-save mode when no voice stream traffic is pending transmission. The APSD mode of operation may then be resumed when another voice stream becomes pending. It may be advantageous to dynamically change the power-saving mode because, absent any traffic in the uplink  114 , the WCM  116  may periodically transmit a trigger packet in the uplink  114 . The trigger packet may be transmitted to ensure that any traffic buffered at the wireless access point  124  is buffered for no longer than a period between trigger packets. However, the latter period may typically be shorter than a beacon interval period. Thus, a lower power consumption is obtained for downlink voice signaling traffic by operating in the legacy power-save mode when no voice packets are pending transmission in the uplink  114 .  
         [0022]     The apparatus  100  may thus include the WCM  116 . The WCM  116  may be capable of wirelessly coupling to the wireless access point  124  to facilitate data exchange between the WPED  112  and a network  127  coupled to the wireless access point  124 . More specifically, a WCM transmitter  132  may be capable of communicatively coupling to a receiver  136  in the wireless access point  124  to create the uplink  114 . A WCM receiver  140  may be capable of communicatively coupling to a transmitter  144  in the wireless access point  124  to create the downlink  126 .  
         [0023]     A power saving logic module  152  may be coupled to the WCM transmitter  132 , the WCM receiver  140 , or both. The power saving logic module  152  may disable the WCM transmitter  132 , the WCM receiver  140 , or some other portion of the WCM  116 . These portions of the WCM  116  may be disabled for a sleep period if no traffic is pending transmission from the WCM  116  or from the wireless access point  124 .  
         [0024]     An APSD state logic module  156  may be coupled to the power saving logic module  152 . The APSD state logic module  156  may dynamically control an APSD state of the WCM  116 . That is, the APSD state logic module  156  may control whether the WCM  116  operates in a U-APSD mode or in a non-APSD mode. The APSD state logic module  156  may choose a power saving mode based upon an indication that a VoIP voice packet stream is pending transmission at the WCM  116 . The state logic module  156  may dynamically determine which access categories are trigger enabled and which access categories are delivery enabled.  
         [0025]     The apparatus  100  may also include a VoIP application startup sense module  160  coupled to the APSD state logic module  156 . The VoIP application startup sense module  160  may sense an initialization of the VoIP application  108 . The VoIP application startup sense module  160  may consequently signal the APSD state logic module  156  to initiate an operation of the WCM  116  in an APSD disabled mode.  
         [0026]     The apparatus  100  may further include a VoIP voice packet stream start sense module  164  coupled to the APSD state logic module  156 . The VoIP voice packet stream start sense module  164  may sense that a VoIP voice packet stream is ready for transmission from the WCM  116 . The VoIP voice packet stream start sense module  164  may consequently signal the APSD state logic module  156  to initiate an operation of the WCM  116  in an APSD enabled mode.  
         [0027]     A VoIP voice packet stream end sense module  168  may also be coupled to the APSD state logic module  156 . The VoIP voice packet stream end sense module  168  may sense a termination of the transmission of the VoIP voice packet stream. The VoIP voice packet stream end sense module  168  may consequently signal the APSD state logic module  156  to initiate an operation of the WCM  116  in an APSD disabled mode.  
         [0028]     In another embodiment, a system  180  may include one or more of the apparatus  100 , as previously described. The system  180  may also include an antenna  182  coupled to the WCM  116 . The antenna  182  may communicatively couple the WCM  116  to the wireless access point  124 . The antenna  182  may comprise a patch, omnidirectional, beam, monopole, dipole, or slot antenna, among other types.  
         [0029]     Any of the components previously described can be implemented in a number of ways, including embodiments in software. Thus, the apparatus  100 ; VoIP application  108 ; WPED  112 ; uplink  114 ; WCM  116 ; wireless access point  124 ; downlink  126 ; network  127 ; transmitters  132 ,  144 ; receivers  136 ,  140 ; power saving logic module  152 ; APSD state logic module  156 ; VoIP application startup sense module  160 ; VoIP voice packet stream start sense module  164 ; VoIP voice packet stream end sense module  168 ; system  180 ; and antenna  182  may all be characterized as “modules” herein.  
         [0030]     The modules may include hardware circuitry, single or multi-processor circuits, memory circuits, software program modules and objects, firmware, and combinations thereof, as desired by the architect of the apparatus  100  and the system  180  and as appropriate for particular implementations of various embodiments.  
         [0031]     The apparatus and systems of various embodiments may be useful in applications other than decreasing a latency associated with a receipt of buffered voice signaling traffic associated with wireless VoIP communications. Thus, various embodiments of the invention are not to be so limited. The illustrations of the apparatus  100  and the system  180  are intended to provide a general understanding of the structure of various embodiments. They are not intended to serve as a complete description of all the elements and features of apparatus and systems that might make use of the structures described herein.  
         [0032]     Applications that may include the novel apparatus and systems of various embodiments include electronic circuitry used in high-speed computers, communication and signal processing circuitry, modems, single or multi-processor modules, single or multiple embedded processors, data switches, and application-specific modules, including multilayer, multi-chip modules. Such apparatus and systems may further be included as sub-components within a variety of electronic systems, such as televisions, cellular telephones, personal computers (e.g., laptop computers, desktop computers, handheld computers, tablet computers, etc.), workstations, radios, video players, audio players (e.g., mp3 players), vehicles, medical devices (e.g., heart monitor, blood pressure monitor, etc.) and others. Some embodiments may include a number of methods.  
         [0033]      FIG. 2  is a flow diagram illustrating several methods according to various embodiments. A WCM may be associated with a WPED, including, for example, a personal digital assistant, a handheld computer, a laptop computer, and a mobile telephone, among other wireless portable electronic devices. Turning back to  FIG. 1 , for example, the WCM  116  may be associated with the WPED  112 . The WCM  116  may be capable of wirelessly coupling to a wireless access point  124  to facilitate data exchange between the WPED  112  and a network  127  coupled to the wireless access point  124 .  
         [0034]     A method  200  may begin at block  205  with initializing a VoIP application to execute in the WPED. Alternatively, the WCM, a driver associated with the WCM, or both may initiate a state associated with a start of a voice call. The method  200  may continue at block  209  with sending one or more traffic stream specification (TSPEC) control packets from the WCM to the wireless AP. The TSPEC control packet(s) may be sent with an APSD bit reset, to advise the wireless AP to operate in an APSD disabled mode.  
         [0035]     The method  200  may include operating the WCM in the APSD disabled mode, at block  211 . Operating in the APSD disabled mode, the WCM (a) may not deliver downlink voice signaling traffic in response to either uplink voice traffic or uplink voice signaling traffic; (b) may not use uplink voice signaling traffic to trigger a delivery of either downlink voice traffic or downlink voice signaling traffic; (c) may not deliver downlink voice traffic in response to either uplink voice traffic or uplink voice signaling traffic; and (d) may not use uplink voice traffic to trigger a delivery of either downlink voice traffic or downlink voice signaling traffic.  
         [0036]     The method  200  may also include sensing that a VoIP voice packet stream is ready for transmission from the WCM, at block  213 . The method  200  may further include sending one or more TSPEC control packets from the WCM to the wireless AP, at block  215 . The TSPEC control packet(s) may be sent with an APSD bit set, to advise the wireless AP to operate in an APSD enabled mode. The APSD enabled mode may comprise disabling transmitter operation, receiver operation, or both at the WCM. The transmitter and/or receiver operation may be disabled for a sleep period if no traffic is pending transmission from either the WPED or from the wireless AP. In some embodiments, the APSD enabled mode may comprise an unscheduled APSD mode of operation.  
         [0037]     The method  200  may continue with operating the WCM in the APSD enabled mode, at block  217 . Operating in the APSD enabled mode, the WCM (a) may deliver downlink voice signaling traffic in response to uplink voice traffic; (b) may not use uplink voice signaling traffic to trigger a delivery of either downlink voice traffic or downlink voice signaling traffic; (c) may deliver downlink voice traffic in response to uplink voice traffic; and (d) may use uplink voice traffic to trigger a delivery of downlink voice traffic, downlink voice signaling traffic, or both.  
         [0038]     The method  200  may include sensing a termination of the transmission of the VoIP voice packet stream, at block  219 . The method  200  may also include sending one or more TSPEC control packets with the APSD bit reset, to advise the wireless AP to operate in an APSD disabled mode, at block  220 . An iteration of the method  200  may conclude with operating the WCM in the APSD disabled mode, at block  221 . Additional iterations may occur as additional voice packet streams are sensed, beginning at block  213 .  
         [0039]     In some embodiments disclosed herein, the WCM may perform some activities according to an IEEE standard 802.11E. It may be possible to execute the activities described herein in an order other than the order described. And, various activities described with respect to the methods identified herein can be executed in repetitive, serial, or parallel fashion.  
         [0040]     A software program may be launched from a computer-readable medium in a computer-based system to execute functions defined in the software program. Various programming languages may be employed to create software programs designed to implement and perform the methods disclosed herein. The programs may be structured in an object-orientated format using an object-oriented language such as Java or C++. Alternatively, the programs may be structured in a procedure-orientated format using a procedural language, such as assembly or C. The software components may communicate using a number of mechanisms well known to those skilled in the art, such as application program interfaces or inter-process communication techniques, including remote procedure calls. The teachings of various embodiments are not limited to any particular programming language or environment. Thus, other embodiments may be realized, as discussed regarding  FIG. 3  below.  
         [0041]      FIG. 3  is a block diagram of an article  385  according to various embodiments of the invention. Examples of such embodiments may comprise a computer, a memory system, a magnetic or optical disk, some other storage device, or any type of electronic device or system. The article  385  may include one or more processor(s)  387  coupled to a machine-accessible medium such as a memory  389  (e.g., a memory including electrical, optical, or electromagnetic elements). The medium may contain associated information  391  (e.g., computer program instructions, data, or both) which, when accessed, results in a machine (e.g., the processor(s)  387 ) performing the activities previously described.  
         [0042]     Implementing the apparatus, systems, and methods disclosed herein may dynamically switch a power saving mode of operation between a legacy power-save mode and an APSD mode based upon whether or not a voice packet stream is pending transmission. Lower latencies associated with downlink voice signaling traffic and a reduced power consumption may result.  
         [0043]     Although the inventive concept may include embodiments described in the exemplary context of an IEEE standard 802.xx implementation (e.g., 802.11, 802.11a, 802.11b, 802.11E, 802.11g, 802.16, etc.), the claims are not so limited. Additional information regarding the IEEE 802.11a protocol standard may be found in IEEE Std 802.11a, Supplement to IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications—High-speed Physical Layer in the 5 GHz Band (published 1999; reaffirmed Jun. 12, 2003). Additional information regarding the IEEE 802.11b protocol standard may be found in IEEE Std 802.11b, Supplement to IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Higher-Speed Physical Layer Extension in the 2.4 GHz Band (approved Sep. 16, 1999; reaffirmed Jun. 12, 2003). Additional information regarding the IEEE 802.11g protocol standard may be found in IEEE Std 802.11g™, IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment  4 : Further Higher Data Rate Extension in the 2.4 GHz Band (approved Jun. 12, 2003). Additional information regarding the IEEE 802.16 protocol standard may be found in IEEE Standard for Local and Metropolitan Area Networks—Part 16: Air Interface for Fixed Broadband Wireless Access Systems (published Oct. 1, 2004).  
         [0044]     Embodiments of the present invention may be implemented as part of any wired or wireless system. Examples may also include embodiments comprising multi-carrier wireless communication channels (e.g., orthogonal frequency division multiplexing (OFDM), discrete multitone (DMT), etc.) such as may be used within a wireless personal area network (WPAN), a wireless local area network (WLAN), a wireless metropolitan are network (WMAN), a wireless wide area network (WWAN), a cellular network, a third generation (3G) network, a fourth generation (4G) network, a universal mobile telephone system (UMTS), and like communication systems, without limitation.  
         [0045]     The accompanying drawings that form a part hereof show, by way of illustration and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.  
         [0046]     Such embodiments of the inventive subject matter may be referred to herein individually or collectively by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept, if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.  
         [0047]     The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In the foregoing Detailed Description, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted to require more features than are expressly recited in each claim. Rather, inventive subject matter may be found in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.