Abstract:
A technique is disclosed involves a station (e.g., an IEEE 802.11 station, etc.) requesting that one or more frames be transmitted from an access point to the station. The station might have been in power save mode during Bluetooth operation for the purpose of causing the access point to queue frames that are intended for the station. The station making the request is collocated with the Bluetooth station or is, in fact, a single station that supports two protocols (i.e., has two parts), and is able to determine the regular timing of the Bluetooth synchronous connected oriented (SCO) packet transmissions. The requests to the access point for IEEE 802.11 frames are timed to cause the access point response frames to fall between the Bluetooth messages, thus managing potential interference.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of: 
    1. U.S. provisional application Ser. No. 60/491,214, filed Jul. 30, 2003, entitled “Managing via an Access Point Coexistence of Separate Protocols Sharing the Same Communications Channel,” (Attorney Docket: 680-084us), 
 
 which is also incorporated by reference. 
   
 
         [0004]     The following patent applications are incorporated by reference: 
    1. U.S. application Ser. No. 10/830570, filed Apr. 23, 2004, entitled “Signaling Extended Functionality and Management Information in a Network,” (Attorney Docket: 680-086us); and     2. U.S. application Ser. No. 10/830575, filed Apr. 23, 2004, entitled “Managing Coexistence of Separate Protocols Sharing the Same Communications Channel,” (Attorney Docket: 680-088us).   
 
     
    
     FIELD OF THE INVENTION  
       [0007]     The present invention relates to telecommunications in general, and, more particularly, to local area networks (LAN).  
       BACKGROUND OF THE INVENTION  
       [0008]      FIG. 1  depicts a schematic diagram of wireless local-area network (LAN)  100  in the prior art comprising access point  101 , stations  102 - 1  through  102 -K, wherein K is a positive integer, and shared-communications channel  103 . Stations  102 - 1  through  102 -K are typically associated with host computers (not shown), such as notebook computers, personal digital assistants (PDA), tablet PCs, etc. Stations  102 - 1  through  102 -K enable communications between (i) the host computers or (ii) the host computers and other devices, such as printer servers, email servers, file servers, etc. Access point  101  enables stations  102 - 1  through  102 -K to (i) coordinate transmissions between each other and (ii) communicate with devices in other communications networks.  
         [0009]     Access point  101  and stations  102 -k, for k=1 through K, transmit data blocks called “frames” over shared-communications channel  103 . If two or more stations (or access point  101  and a station) transmit frames simultaneously, then one or more frames can become corrupted, resulting in what is called a “collision”. Local-area networks, therefore, typically employ a medium access control (MAC) protocol for ensuring that a station can gain exclusive access to shared-communications channel  103  for an interval of time in order to transmit one or more frames. A “protocol” is a set of communications procedures that relate to the format and timing of transmissions between different stations.  
         [0010]     In wireless local-area networks that are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, the medium access control protocol is based on a mechanism called “carrier sense multiple access” (CSMA), in which station  102 -k or access point  101  can detect whether shared-communications channel  103  is busy or idle. If shared-communications channel  103  is busy, station  102 -k or access point  101  will wait until the channel is idle before attempting to transmit a signal that conveys a message.  
         [0011]     Shared-communications channel  103  can be used by stations that operate in accordance with different protocols. For example, the IEEE 802.11 standard (e.g., 802.11a, 802.11b, 802.11e, 802.11g, etc.) describes one set of protocols, and the Bluetooth standard describes another set of protocols. A particular station (e.g., station  102 - 1 , etc.) might handle an IEEE 802.11 protocol or a Bluetooth protocol, or both. A station that is capable of handling multiple protocols (i.e., a “multi-protocol station”) comprises multiple protocol subsystems, or “parts”, in which each part handles communications in accordance with a specific protocol.  
         [0012]     Coordination of the IEEE 802.11 and Bluetooth protocols in a multi-protocol station can become particularly difficult when the Bluetooth part transmits or receives packets that are synchronous connection oriented (SCO) (e.g., voice packets, etc.), because such packets are often repeatedly transmitted at high data rates. As a result, Bluetooth coexistence mechanisms, such as the IEEE 802.15.2 set of standards, have been introduced in the prior art to address this problem. Such coexistence mechanisms coordinate a multi-protocol station&#39;s transmission of (i) Bluetooth synchronous connection oriented voice packets, and (ii) frames of another protocol. These mechanisms, however, do not prevent collisions that can occur when access point  101  transmits an IEEE 802.11 frame at the same time that a multi-protocol station transmits a Bluetooth packet.  
         [0013]     Another approach in the prior art is to use the IEEE 802.11 Power Save state to cause access point  101  to queue outbound IEEE 802.11 traffic that is intended for station  102 -k. The queuing occurs during the time that station  102 -k indicates that it is inactive in the IEEE 802.11 sense as far as access point  101  is aware, but actually remains active in the Bluetooth sense. The technique of entering and exiting power save mode to allow time for Bluetooth operation, however, does not effectively support synchronous connection oriented operation of Bluetooth for some applications (e.g., voice, etc.). The repetition rate of synchronous connection oriented Bluetooth is so rapid that it is often impractical to rely on the IEEE 802.11 frames that indicate the rapid changes in power save state.  
         [0014]     Therefore, a need exists for an improvement in how stations that operate in accordance with different protocols coexist with an access point without some of the costs and disadvantages in the prior art.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention provides a technique for improving how stations that operate in accordance with different protocols coexist with an access point without some of the costs and disadvantages in the prior art. In the illustrative embodiment of the present invention, a station (e.g., an IEEE 802.11 station, etc.) requests that one or more frames be transmitted from an access point to the station. The station might have been in power save mode during Bluetooth operation for the purpose of causing the access point to queue frames that are intended for the station. The station that makes the request is collocated with the Bluetooth station or is, in fact, a single station that supports two protocols (i.e., has two parts), and is able to determine the regular timing of the Bluetooth synchronous connected oriented (SCO) packet transmissions. The requests to the access point for IEEE 802.11 frames are timed to cause the access point response frames to fall between the Bluetooth messages, thus managing potential interference.  
         [0016]     In the first embodiment of the present invention, soon after detecting the end of a Bluetooth transmission, a station requesting data frames transmits a PS_Poll frame to request one or more IEEE 802.11 data frames from the access point. The access point responds to the PS_Poll frame with a data frame after an SIFS (short interframe space) delay. The station that transmits the PS_Poll frame does so, in some embodiments, without first determining whether or not a queued data frame exists at the access point for the station, thus minimizing the delay.  
         [0017]     In the second embodiment of the present invention, soon after detecting the end of a Bluetooth transmission, a station requesting data frames transmits a Clear_to_Send (CTS) frame that specifies a particular “info-address” field value to request that the access point immediately transmit one or more IEEE 802.11 data frames to the requesting station. The CTS frame with info-address is sent with a non-zero duration value that is sufficient to cover the anticipated length of the data frame or frames, enabling network allocation vector (NAV) protection from stations that are able to detect the transmitted duration field value. NAV protection uses the IEEE 802.11 virtual carrier sense mechanism to cause stations that detect the frame exchange to set their internal carrier sense to the “busy” state, even if they do not sense radio frequency energy during the NAV protection interval. The CTS frame with info-address and the corresponding NAV protection are important in that the access point does not have to contend for the shared-communications channel being used, and possibly be delayed beyond the imposed interference-free interval at the receiving station.  
         [0018]     In both the first and second embodiments, the frame (i.e., PS_Poll or CTS with info-address) that indicates readiness to receive at least one data frame can be transmitted by the requesting station to the access point without contending for the shared-communications channel. This can be the case, for example, when the station is already aware that previous NAV protection extends through at least the end of the Bluetooth transmission.  
         [0019]     The illustrative embodiment is described in the context of Bluetooth and IEEE 802.11. However, it will be clear to those skilled in the art, after reading this specification, how to apply the illustrative embodiment of the present invention to other separate protocols.  
         [0020]     An illustrative embodiment of the present invention comprises: detecting the end of a transmission of a first signal in accordance with a first protocol on a shared-communications channel; and transmitting a second signal in accordance with a second protocol on the shared-communications channel after the detecting of the end of the transmission, wherein the second signal conveys a readiness to receive at least one data frame. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  depicts a schematic diagram of wireless local area network  100  in the prior art.  
         [0022]      FIG. 2  depicts a schematic diagram of a portion of network  200  in accordance with the illustrative embodiment of the present invention.  
         [0023]      FIG. 3  depicts a block diagram of the salient components of access point  201  in accordance with the illustrative embodiment of the present invention.  
         [0024]      FIG. 4  depicts a block diagram of the salient components of multi-protocol station  203 -i in accordance with the illustrative embodiment of the present invention.  
         [0025]      FIG. 5  depicts a flowchart of the salient tasks performed by multi-protocol station  203 -i in accordance with the first illustrative embodiment of the present invention.  
         [0026]      FIG. 6  depicts a flowchart of the salient tasks performed by multi-protocol station  203 -i in accordance with the second illustrative embodiment of the present invention.  
         [0027]      FIG. 7  depicts a flowchart of the salient tasks performed by access point  201 , in accordance with the second illustrative embodiment of the present invention.  
         [0028]      FIG. 8  depicts a sequence of messages exchanged in accordance with the first illustrative embodiment of the present invention.  
         [0029]      FIG. 9  depicts a sequence of messages exchanged in accordance with the second illustrative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0030]      FIG. 2  depicts a schematic diagram of network  200  in accordance with the illustrative embodiment of the present invention. Network  200  comprises access point  201 ; stations  202 - 1  through  202 -L, wherein L is a positive integer; multi-protocol stations  203 - 1  through  203 -M, wherein M is a positive integer; host computers  204 - 1  through  202 -P, wherein P is a positive integer equal to L plus M; and wireless shared-communications channel  205 , interconnected as shown. In some embodiments, network  200  is a wireless local area network.  
         [0031]     Access point  201 , stations  202 - 1  through  202 -L, and multi-protocol stations  203 - 1  through  203 -M operate in accordance with an IEEE 802.11 standard. Multi-protocol stations  203 - 1  through  203 -M also operate in accordance with the Bluetooth standard.  
         [0032]     It will be clear to those skilled in the art, after reading this specification, how to make and use embodiments of the present invention that operate in accordance with other protocols. Furthermore, it will be clear to those skilled in the art, after reading this specification, how to make and use embodiments of the present invention that use a wireline or tangible shared-communications channel.  
         [0033]     Access point  201  enables stations  202 - 1  through  202 -L and multi-protocol stations  203 - 1  through  203 -M within network  200  to communicate with devices in other communications networks. Furthermore, because access point  201  coordinates communication over shared-communications channel  205 , stations  202 - 1  through  202 -L and multi-protocol stations  203 - 1  through  203 -M communicate with each other through access point  201 . The salient details of access point  201  are described below and with respect to  FIG. 3 .  
         [0034]     Stations within network  200 , in other embodiments, communicate directly with each other and without access point  201 . It will be clear to those skilled in the art how to make and use stations that communicate with each other without access point  201 .  
         [0035]     Station  202 -i, for i=1 through L, comprises a radio (i.e., a transmitter/receiver subsystem) that enables host computer  204 -i to communicate via shared-communications channel  205  by using a single protocol only (i.e., IEEE 802.11 or Bluetooth, but not both). Station  202 -i is capable of receiving data blocks from host computer  204 -i and transmitting over shared-communications channel  205  messages (e.g., frames, packets, etc.) that comprise the data received from host computer  204 -i. Station  202 -i is also capable of receiving messages from shared-communications channel  205  and sending to host computer  204 -i data blocks that comprise data from the messages. It will be clear to those skilled in the art how to make and use station  202 -i.  
         [0036]     Multi-protocol station  203 -i, for i=1 through M, comprises the radios that enable host computer  204 -(i+L) to communicate via shared-communications channel  205 . Multi-protocol station  203 -i is capable of receiving data blocks from host computer  204 -(i+L) and transmitting over shared-communications channel  205  data messages comprising the data received from host computer  204 -(i+L). Multi-protocol station  203 -i is also capable of receiving data messages from shared-communications channel  205  and sending to host computer  204 -(i+L) data blocks comprising data from the data messages. It will be clear to those skilled in the art, after reading this specification, how to make and use multi-protocol station  203 -i. The salient details for multi-protocol station  203 -i are described below and with respect to  FIG. 4 .  
         [0037]     Host computer  204 -i, for i=1 to P, is capable of generating data blocks and transmitting those data blocks to station  202 -i or multi-protocol station  203 -j, wherein j is equal to (i−L). Host computer  204 -i is also capable of receiving data blocks from station  202 -i or multi-protocol station  203 -j and of processing and using the data contained within those data blocks. Host computer  204 -i can be, for example, a desktop or a laptop computer that uses network  200  to communicate with other hosts and devices via access point  201 . It will be clear to those skilled in the art how to make and use host computer  204 -i.  
         [0038]      FIG. 3  depicts a block diagram of the salient components of access point  201  in accordance with the illustrative embodiment of the present invention. Access point  201  comprises receiver  301 , processor  302 , memory  303 , and transmitter  304 , interconnected as shown.  
         [0039]     Receiver  301  is a circuit that is capable of receiving messages from shared-communications channel  205 , in well-known fashion, and of forwarding them to processor  302 . It will be clear to those skilled in the art how to make and use receiver  301 .  
         [0040]     Processor  302  is a general-purpose processor that is capable of performing the tasks described below and with respect to  FIG. 7, 8 , and  9 . It will be clear to those skilled in the art, after reading this specification, how to make and use processor  302 .  
         [0041]     Memory  303  is capable of storing programs and data used by processor  302 . It will be clear to those skilled in the art how to make and use memory  303 .  
         [0042]     Transmitter  304  is a circuit that is capable of receiving messages from processor  302 , in well-known fashion, and of transmitting them on shared-communications channel  205 . It will be clear to those skilled in the art how to make and use transmitter  304 .  
         [0043]      FIG. 4  depicts a block diagram of the salient components of multi-protocol station  203 -i in accordance with the illustrative embodiment of the present invention. Multi-protocol station  203 -i comprises receiver  401 -i, processor  402 -i, memory  403 -i, and transmitter  404 -i, interconnected as shown.  
         [0044]     Receiver  401 -i is a circuit that is capable of receiving messages from shared-communications channel  205 , in well-known fashion, and of forwarding them to processor  402 -i. It will be clear to those skilled in the art how to make and use receiver  401 -i.  
         [0045]     Processor  402 -i is a general-purpose processor that is capable of performing the tasks described below and with respect to  FIGS. 5, 6 ,  8 , and  9 . It will be clear to those skilled in the art, after reading this specification, how to make and use processor  402 -i.  
         [0046]     Memory  403 -i is capable of storing programs and data used by processor  402 -i. It will be clear to those skilled in the art how to make and use memory  403 -i.  
         [0047]     Transmitter  404 -i is a circuit that is capable of receiving messages from processor  402 -i, in well-known fashion, and of transmitting them on shared-communications channel  205 . It will be clear to those skilled in the art how to make and use transmitter  404 -i.  
         [0048]     Multi-protocol station  203 -i comprises a single receiver/transmitter pair, in accordance with the illustrative embodiment of the present invention. Receiver  401 -i and transmitter  404 -i are each capable of communicating in accordance with both the IEEE 802.11 protocol and the Bluetooth protocol. In other embodiments, multi-protocol station  203 -i comprises multiple receiver/transmitter pairs, where each pair handles a specific protocol (e.g., IEEE 802.11, Bluetooth, etc.).  
         [0049]      FIG. 5  depicts a flowchart of the salient tasks performed by multi-protocol station  203 -i in accordance with the first illustrative embodiment of the present invention. Multi-protocol station  203 - 1  and access point  201  are used as examples. For illustrative purposes, it is assumed that multi-protocol station  203 - 1  supports the IEEE 802.11 and Bluetooth protocols. In the example provided, Bluetooth is the first protocol and IEEE 802.11 is the second protocol.  
         [0050]     At task  501 , multi-protocol station  203 - 1  detects the end of a transmission of a first signal in accordance with the Bluetooth protocol on shared-communications channel  205 . This can be determined, for example, through packet traffic arbitration between IEEE 802.11 and Bluetooth medium access control, as is known in the art. It will be clear to those skilled in the art how to detect the end of a transmission.  
         [0051]     At task  502 , multi-protocol station  203 - 1  transmits to access point  201  a PS_Poll frame as is known in the art into shared-communications channel  205  and by using the IEEE 802.11 protocol. In some embodiments, multi-protocol station  203 - 1  transmits the PS_Poll frame without first determining if a data frame that is intended for multi-protocol station  203 - 1  exists at access point  201 . It will be clear to those skilled in the art how to transmit a PS_Poll frame.  
         [0052]     At task  503 , multi-protocol station  203 - 1  receives in well-known fashion at least one IEEE 802.11 data frame from access point  201 .  
         [0053]      FIG. 6  depicts a flowchart of the salient tasks performed by multi-protocol station  203 -i in accordance with the second illustrative embodiment of the present invention. Multi-protocol station  203 - 1  and access point  201  are used as examples. For illustrative purposes, it is assumed that multi-protocol station  203 - 1  supports the IEEE 802.11 and Bluetooth protocols. In the example provided, Bluetooth is the first protocol and IEEE 802.11 is the second protocol.  
         [0054]     At task  601 , multi-protocol station  203 - 1  detects the end of a transmission of a first signal in accordance with the Bluetooth protocol on shared-communications channel  205 . This can be determined, for example, through packet traffic arbitration between IEEE 802.11 and Bluetooth medium access control, as is known in the art. It will be clear to those skilled in the art how to detect the end of a transmission.  
         [0055]     At task  602 , multi-protocol station  203 - 1  transmits to access point  201  a Clear_to_Send frame as is known in the art into shared-communications channel  205  and by using the IEEE 802.11 protocol. The Clear_to_Send frame comprises a receiver address field and a duration field, as are known in the art.  
         [0056]     The receiver address field conveys an info-address value. Info-address is described further in U.S. patent application Ser. No. 10/830570 (Attorney Docket 680-086us). The info-address value that is used in the illustrative embodiment indicates that access point  201  transmit at least one data frame without first contending for shared-communications channel  205 . The info-address value also conveys information that indicates that access point  201  is the intended recipient of the frame. For example, the info-address value can comprise at least a portion of access point  201 &#39;s latest timing synchronization function (TSF) value, as is known in the art, which is unlikely to be the same as the latest timing synchronization function value of another, nearby access point. It will be clear to those skilled in the art, after reading this specification, how to encode information as part of the info-address value to indicate an intended recipient.  
         [0057]     The duration field has a value based on the expected length of time required for access point  201  to transmit at least a first data frame. The duration field is used by other stations within network  200  to update their network allocation vectors in well-known fashion. This enables access point  201  to transmit without having to contend for shared-communications channel  205  and without incurring delay.  
         [0058]     In other embodiments, multi-protocol station  203 - 1  transmits a different type of frame (i.e., other than Clear_to_Send) that conveys the info-address. It will be clear to those skilled in the art, after reading this specification, how to transmit a frame (e.g., Clear_to_Send, etc.) that conveys the info-address.  
         [0059]     At task  603 , multi-protocol station  203 - 1  receives in well-known fashion at least one IEEE 802.11 data frame from access point  201 .  
         [0060]     At task  604 , multi-protocol station  203 - 1  transmits to access point  201  an acknowledgement frame in well-known fashion. In some embodiments, the acknowledgement frame comprises a duration field with a value that sets the network allocation vector to zero, having the effect of allowing all stations to contend for shared-communications channel  205 .  
         [0061]      FIG. 7  depicts a flowchart of the salient tasks performed by access point  201  in accordance with the second illustrative embodiment of the present invention. Multi-protocol station  203 - 1  is also used as an example.  
         [0062]     At task  701 , access point  201  receives from multi-protocol station  203 - 1  a first signal on shared-communications channel  205 . The first signal conveys a Clear_to_Send frame that comprises an info-address field and a duration field. The info-address field and duration field were described earlier in conjunction with  FIG. 6 .  
         [0063]     At task  702 , access point  201  transmits to multi-protocol station  203 - 1  at least one IEEE 802.11 data frame in well-known fashion. Because access point  201  transmits one or more data frames in response to receiving a Clear_to_Send message with the info-address field value of the illustrative embodiment, access point  201  transmits the data frame or frames without contending for shared-communications channel  205  and without having to incur the added delay.  
         [0064]     At task  703 , in some embodiments, access point  201  receives an acknowledgement frame in well-known fashion.  
         [0065]      FIG. 8  depicts a sequence of messages (e.g., frames, packets, etc.) in accordance with the first illustrative embodiment of the present invention. Multi-protocol station  203 - 1  is used in the example. For illustrative purposes, it is assumed that multi-protocol station  203 - 1  supports the IEEE 802.11 and Bluetooth protocols. The Bluetooth part of multi-protocol station  203 - 1  has to transmit High Quality Voice 3 (HV3) packets every 3.75 milliseconds with each packet being 625 microseconds in length. The IEEE 802.11 part of multi-protocol station  203 - 1  can be made aware of this transmission requirement in the course of monitoring for transmit opportunities.  
         [0066]     Alternatively, the illustrative embodiment also supports the scenario in which the IEEE 802.11 and the Bluetooth part are in separate stations that are able to exchange transmission requirements with each other, and have to coexist with other stations. It will be clear to those skilled in the art, after reading this specification, how to apply the illustrative embodiment to two different stations operating in accordance with two different protocols.  
         [0067]     As part of Bluetooth activity interval  801 , multi-protocol station  203 - 1  detects the end of a transmission of a first protocol message (e.g., a Bluetooth HV3 [or “High Quality Voice 3”] packet, etc.) on shared-communications channel  205 . Detecting can be performed in a variety of ways. In the illustrative example, the second protocol part of multi-protocol station  203 - 1  coexists with the first protocol (e.g., Bluetooth, etc.) part and, as a result, can detect status directly on the Bluetooth part&#39;s shared-communications channel usage. Alternatively, the second protocol part of multi-protocol station  203 - 1  might sense first protocol activity ending on shared-communications channel  205 . It will be clear to those skilled in the art how to detect the end of a transmission.  
         [0068]     The second protocol part (e.g., the IEEE 802.11 part, etc.) of multi-protocol station  203 - 1  transmits PS_Poll frame  802  to access point  201  on shared-communications channel  205  using the second protocol. PS_Poll frame  802  indicates readiness to receive at least one data frame.  
         [0069]     In some embodiments, PS_Poll frame  802  can be transmitted without contending for shared-communications channel  205 . This can be the case, for example, when multi-protocol station  203 - 1  is already aware that previously-imposed network allocation vector (NAV) protection extends through at least the end of the transmission of the first protocol message. For example, multi-protocol  203 - 1  itself might have already set the network allocation vector. One such technique is described further in U.S. patent application Ser. No. 10/830575 (Attorney Docket 680-088us).  
         [0070]     After waiting for short interframe space (SIFS) interval  803 , access point  201  responds to PS_Poll frame  802  with at least one data frame during interval  804 .  
         [0071]     As part of Bluetooth activity interval  805 , the first protocol part of multi-protocol station  203 - 1  transmits, in some embodiments, another first protocol message (e.g., a Bluetooth HV3 [or “High Quality Voice 3”] packet, etc.) on shared-communications channel  205 .  
         [0072]      FIG. 9  depicts a sequence of messages (e.g., frames, packets, etc.) in accordance with the second illustrative embodiment of the present invention. Multi-protocol station  203 - 1  is used in the example. For illustrative purposes, it is assumed that multi-protocol station  203 - 1  supports the IEEE 802.11 and Bluetooth protocols. The Bluetooth part of multi-protocol station  203 - 1  has to transmit High Quality Voice 3 (HV3) packets every 3.75 milliseconds with each packet being 625 microseconds in length. The IEEE 802.11 part of multi-protocol station  203 - 1  can be made aware of this transmission requirement in the course of monitoring for transmit opportunities.  
         [0073]     Alternatively, the illustrative embodiment also supports the scenario in which the IEEE 802.11 and the Bluetooth part are in separate stations that are able to exchange transmission requirements with each other, and have to coexist with other stations. It will be clear to those skilled in the art, after reading this specification, how to apply the illustrative embodiment to two different stations operating in accordance with two different protocols.  
         [0074]     As part of Bluetooth activity interval  901 , multi-protocol station  203 - 1  detects the end of a transmission of a first protocol message (e.g., a Bluetooth HV3 [or “High Quality Voice 3”] packet, etc.) on shared-communications channel  205 . Detecting can be performed in a variety of ways. In the illustrative example, the second protocol part of multi-protocol station  203 - 1  coexists with the first protocol (e.g., Bluetooth, etc.) part and, as a result, can detect status directly on the Bluetooth part&#39;s shared-communications channel usage. Alternatively, the second protocol part of multi-protocol station  203 - 1  might sense first protocol activity ending on shared-communications channel  205 . It will be clear to those skilled in the art how to detect the end of a transmission.  
         [0075]     The second protocol part (e.g., the IEEE 802.11 part, etc.) of multi-protocol station  203 - 1  transmits Clear_to_Send frame  902  that specifies an info-address to access point  201  on shared-communications channel  205  using the second protocol. Multi-protocol station  203 - 1  specifies within the message a duration field value based on the expected length of time required to transmit at least one data frame in accordance with the second protocol on shared-communications channel  205 . Network allocation vector (NAV) protection interval  903  represents the specified length of time. Clear_to_Send frame  902  that comprises the specific info-address is used to solicit a response from access point  201 , while setting the NAV of other nearby stations, preventing access point  201  from having to contend for shared-communications channel  205  and from incurring delay. Clear_to_Send frame  902  indicates readiness to receive at least one data frame.  
         [0076]     In some embodiments, Clear_to_Send frame  902  can be transmitted without contending for shared-communications channel  205 . This can be the case, for example, when multi-protocol station  203 - 1  is already aware that previously-imposed network allocation vector (NAV) protection extends through at least the end of the transmission of the first protocol message. For example, multi-protocol  203 - 1  itself might have already set the network allocation vector, as for the case of PS_Poll frame  802 .  
         [0077]     During interval  904 , access point  201  responds to the Clear_to_Send that comprises info-address with at least one data frame.  
         [0078]     Multi-protocol station  203 - 1  operating in accordance with the second protocol transmits acknowledgement frame  905  in response to the data frame or frames from access point  201 . Acknowledgement frame  905 , in some embodiments, comprises a duration field with a value that effectively ends network allocation vector protection interval  903 .  
         [0079]     As part of Bluetooth activity interval  906 , the first protocol part of multi-protocol station  203 - 1  transmits, in some embodiments, another first protocol message (e.g., a Bluetooth HV3 [or “High Quality Voice 3”] packet, etc.) on shared-communications channel  205 .  
         [0080]     It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.  
         [0081]     Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.