Abstract:
A technique for coordinating potentially-conflicting air-interface subsystems in the same station is disclosed. In accordance with the first illustrative embodiment of the present invention, a first air-interface subsystem that is compliant with a first protocol (e.g., IEEE 802.11, etc.) and a second air-interface subsystem that is compliant with a second protocol (e.g., Bluetooth, etc.) both have direct physical interfaces with the host that they serve. The two subsystems coordinate their operation via messages that are shuttled between them by the host. In accordance with the second illustrative embodiment, the first air-interface subsystem and the second air-interface subsystem both have a logical connection with the host that they serve, but only the first air-interface subsystem has a physical connection with the host. The second air-interface subsystem cannot exchange messages with the first air-interface subsystem directly but can only do so by routing them through the host.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of:  
         [0002]    1. U.S. provisional application Serial No. 60/453,613, filed Mar. 11, 2003, entitled “Inter-Radio Signaling With a Host Computer” (Attorney Docket: 680-058us), which is also incorporated by reference.  
         [0003]    The following patent applications are incorporated by reference:  
         [0004]    1. U.S. patent application Ser. No. 10/444,383, filed 23 May 2003, entitled “Multi-Protocol Interchip Interface” (Attorney Docket: 680-021us),  
         [0005]    2. U.S. patent application Ser. No. 10/444,519, filed 23 May 2003, entitled “Coordination of Competing Protocols” (Attorney Docket: 680-030us),  
         [0006]    3. U.S. patent application Ser. No. 10/___,___, entitled “Transmit Request Signaling Between Transceivers” (Attorney Docket: 680-062us), and  
         [0007]    4. U.S. patent application Ser. No. 10/___,___, entitled “Advance Notification of Transmit Opportunities on a Shared-Communications Channel” (Attorney Docket: 680-063us). 
     
    
     
       FIELD OF THE INVENTION  
         [0008]    The present invention relates to telecommunications in general, and, more particularly, to wireless local area networks.  
         BACKGROUND OF THE INVENTION  
         [0009]    [0009]FIG. 1 depicts a schematic diagram of a portion of wireless local area network  100  in the prior art. Wireless local area network  100  comprises wireless stations  101 - 1  through  101 - 6 , which communicate with each other via the same, shared-communications channel and by using one or more air-interface protocols (i.e., physical and logical standards for wireless communication).  
           [0010]    Wireless stations  101 - 1 ,  101 - 2 , and  101 - 4  communicate using one air-interface protocol (e.g., IEEE 802.11, etc.), wireless stations  101 - 5  and  101 - 6  communicate using a second air-interface protocol (e.g., Bluetooth, etc.), and wireless station  101 - 3  can communicate using both air-interface protocols.  
           [0011]    Wireless station  101 - 3  uses the same, shared-communications channel for both its first air-interface communications and its second air-interface communications, and, therefore, it cannot use both air-interface protocols at the same time. For this reason, wireless station  101 - 3  must coordinate its first air-interface communications with its second air-interface communications.  
           [0012]    There exist various techniques in the prior art for enabling a station to coordinate its various air-interface communications.  
           [0013]    For example, FIG. 2 depicts a block diagram of the salient components of wireless station  101 - 3  in accordance with a first prior-art technique. As shown in FIG. 2, wireless station  101 - 3  comprises host  201 , A/B switch  202 , air-interface subsystem  203 , air-interface subsystem  204 , antenna switch  205 , and antenna  206 , interconnected as shown. Air-interface subsystem  203  communicates in accordance with the first air-interface protocol, and air-interface subsystem  204  communicates in accordance with the second air-interface protocol. Each air-interface subsystem comprises a “radio” and, therefore, can receive and transmit over the shared-communications channel using electromagnetic waves.  
           [0014]    At any given instant, host  201  communicates with air-interface subsystem  203  or air-interface subsystem  204 , but not both, by means of A/B switch  202 . A/B switch  202  requires the user of wireless station  101 - 3  to select the air interface to be used and to manually toggle a two-position switch. In some cases, A/B switch is embedded in host  201  as a “soft switch” that the user toggles through an on-screen menu. Antenna switch  205  directs a signal to be transmitted to antenna  206  from either air-interface subsystem  203  or air-interface subsystem  204 . The state of antenna switch  205  is coupled to the state of A/B switch  202 .  
           [0015]    The first technique is advantageous because it coordinates the use of the air-interface subsystems in an economical matter, but is disadvantageous, however, because the manual nature of the switching mechanism limits the rate at which the air-interface subsystems can be switched to the rate at which a human can switch them.  
           [0016]    [0016]FIG. 3 depicts a block diagram of the salient components of wireless station  101 - 3  in accordance with a second prior-art technique. As shown in FIG. 3, wireless station  101 - 3  comprises host  301 , tandem air-interface subsystem  302 , and antenna  303 , interconnected as shown. The second prior-art technique is characterized by a tandem air-interface subsystem, which is a fully-custom dual air-interface subsystem that is capable of functioning as both an first air-interface subsystem and a second air-interface subsystem on a moment-by-moment basis.  
           [0017]    Tandem air-interface subsystem  302  is a single integrated circuit that communicates in accordance with the first air-interface protocol and with the second air-interface protocol. Host  301  maintains a logical, if not also physical, interface with the first air-interface protocol part of tandem air-interface subsystem  302  and a logical, if not also physical, interface with the second air-interface protocol part of tandem air-interface subsystem  302 . The unified nature of tandem air-interface subsystem  302  inherently coordinates the use of the first air-interface protocol and the second air-interface protocol.  
           [0018]    The second prior-art technique is advantageous because it coordinates the use of the air-interface subsystems and because it enables the host to switch between the two air interfaces at a very high rate.  
           [0019]    The second prior-art technique is disadvantageous, however, because it requires a fully-custom development effort for each combination of air-interface subsystems, which is slow and expensive.  
           [0020]    [0020]FIG. 4 depicts a block diagram of the salient components of wireless station  101 - 3  in accordance with a third prior-art technique. Wireless station  101 - 3  comprises host  401 , air-interface subsystem  402 , air-interface subsystem  403 , antenna switch  404 , antenna  405 , and inter-subsystem interface  406 , interconnected as shown. Air-interface subsystem  402  and air-interface subsystem  403  are interconnected by inter-subsystem interface  406 . Inter-subsystem interface  406  comprises once or more signaling leads and carries signals in accordance with a standard protocol. Inter-subsystem interface  406  enables air-interface subsystem  402  and air-interface subsystem  403  to exchange messages to coordinate their use.  
           [0021]    The third prior-art technique is advantageous because it coordinates the use of the air-interface subsystems, because it enables the host to switch between the two air interfaces at a very high rate, and because it is less expensive than the dual-air-interface solution. Furthermore, the third prior-art technique is advantageous because it enables the development of each air-interface subsystem to be performed independently of other air-interface subsystems.  
           [0022]    The third prior-art technique is disadvantageous, however, because inter-subsystem interface  406  increases the cost of both air-interface subsystems.  
           [0023]    Therefore, the need exists for a technique to coordinate multiple air-interface subsystems without some of the disadvantages associated with techniques in the prior art.  
         SUMMARY OF THE INVENTION  
         [0024]    The present invention is a technique for coordinating potentially-conflicting air-interface subsystems in the same station. In particular, the illustrative embodiments of the present invention coordinate the air-interface subsystems by having the host shuttle messages back and forth between the air-interface subsystems.  
           [0025]    Some embodiments of the present invention are advantageous because they enable the host to switch between the two air interfaces at a very high rate, and because they are less expensive than the dual-air-interface solution. Furthermore, some embodiments of the present invention enable the development of each air-interface subsystem to be performed independently of other air-interface subsystems.  
           [0026]    In accordance with the first illustrative embodiment of the present invention, a first air-interface subsystem that is compliant with a first protocol (e.g., IEEE 802.11, etc.) and a second air-interface subsystem that is compliant with a second protocol (e.g., Bluetooth, etc.) both have direct physical interfaces with the host that they serve. The two subsystems coordinate their operation via messages that are shuttled between them by the host.  
           [0027]    In accordance with the second illustrative embodiment, the first air-interface subsystem and the second air-interface subsystem both have a logical connection with the host that they serve, but only the first air-interface subsystem has a physical connection with the host. The second air-interface subsystem does not have a physical connection with the host. Rather, the second air-interface subsystem has a physical connection with the first air-interface subsystem for passing messages to the host. The second air-interface subsystem cannot exchange messages with the first air-interface subsystem directly but can only do so by routing them through the host.  
           [0028]    The host shuttles messages between the air-interface subsystems in hardware, software, or a combination of hardware and software. Although the illustrative embodiments comprise two air-interface subsystems, 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 comprises any number of air-interface subsystems.  
           [0029]    The illustrative embodiment comprises: receiving a first message at a host processor from a first processor via a wireline shared-communications channel, wherein the first processor performs channel-access control for a first radio, and wherein the first radio communicates via a wireless shared-communications channel on behalf of the host processor; determining with the host processor that the first message is directed to a second processor, wherein the second processor performs channel-access control for a second radio, and wherein the second radio communicates via the wireless shared-communications channel on behalf of the host processor; and forwarding the first message from the host processor to the second processor via the wireline shared-communications channel. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]    [0030]FIG. 1 depicts a schematic diagram of wireless local area network  100  in the prior art.  
         [0031]    [0031]FIG. 2 depicts a block diagram of wireless station  101 - 3 , in accordance with a first prior-art technique.  
         [0032]    [0032]FIG. 3 depicts a block diagram of wireless station  101 - 3 , in accordance with a second prior-art technique.  
         [0033]    [0033]FIG. 4 depicts a block diagram of wireless station  101 - 3 , in accordance with a third prior-art technique.  
         [0034]    [0034]FIG. 5 depicts a block diagram of wireless station  500  in accordance with the first illustrative embodiment of the present invention.  
         [0035]    [0035]FIG. 6 depicts a block diagram of host processor  501  in accordance with the illustrative embodiment of the present invention.  
         [0036]    [0036]FIG. 7 depicts a block diagram of air-interface subsystem  502 - 1  in accordance with the first illustrative embodiment of the present invention.  
         [0037]    [0037]FIG. 8 depicts a message flow diagram in accordance with the first illustrative embodiment of the present invention.  
         [0038]    [0038]FIG. 9 depicts a block diagram of wireless station  900  in accordance with the second illustrative embodiment of the present invention.  
         [0039]    [0039]FIG. 10 depicts a block diagram of air-interface subsystem  902 - 1  in accordance with the second illustrative embodiment of the present invention.  
         [0040]    [0040]FIG. 11 depicts a block diagram of air-interface subsystem  902 - 2  in accordance with the second illustrative embodiment of the present invention.  
         [0041]    [0041]FIG. 12 depicts a message flow diagram in accordance with the second illustrative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0042]    [0042]FIG. 5 depicts a block diagram of wireless station  500  in accordance with the first illustrative embodiment of the present invention. Wireless station  500  is a machine that supports two distinct wireless air-interface protocols for the purpose of transmitting and receiving voice, data, and/or video over a shared-communications channel. Wireless station  500  comprises: host  501 , air-interface subsystem  502 - 1 , air-interface subsystem  502 - 2 , antenna switch  503 , and antenna subsystem  504 , interconnected as shown.  
         [0043]    Host  501  is a machine that is capable of generating one or more data blocks to be transmitted over the wireless shared-communications channel by air-interface subsystems  502 - 1  and  502 - 2 , in well-known fashion. Host  501  is also capable of processing one or more data blocks that it receives from the wireless shared-communications channel by air-interface subsystems  502 - 1  and  502 - 2 , in well-known fashion. The salient details of host  501  are described below and with respect to FIG. 6.  
         [0044]    Each of air-interface subsystems  502 - 1  and  502 - 2  comprises a radio that enables host  501  to communicate via the wireless shared-communications channel using a different air-interface protocol.  
         [0045]    Air-interface subsystem  502 - 1  enables host  501  to communicate via the IEEE 802.11 air-interface protocol. Air-interface subsystem  502 - 1  communicates with host  501  via path  505 - 1 .  
         [0046]    Air-interface subsystem  502 - 2  enables host  501  to communicate via the Bluetooth air-interface protocol. Air-interface subsystem  502 - 2  communicates with host  501  via path  505 - 2 .  
         [0047]    Although the illustrative embodiment enables communication via the IEEE 802.11 and Bluetooth air-interface protocols, 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 other air-interface protocols.  
         [0048]    Each of air-interface subsystems  502 - 1  and  502 - 2  is capable of receiving one or more data blocks from host  501  and transmitting, over the wireless shared-communications channel, one or more data frames that comprise the payload data received from host  501 . Each of air-interface subsystems  502 - 1  and  502 - 2  is also capable of receiving one or more data frames from the wireless shared communications channel and sending to host  501  one or more data blocks comprising the payload data from the data frames. It will be clear to those skilled in the art, after reading this specification, how to make and use air-interface subsystems  502 - 1  and  502 - 2 .  
         [0049]    Antenna switch  503  enables air-interface subsystems  502 - 1  and  502 - 2  to share antenna subsystem  504 . Antenna switch  503  provides signals to air-interface subsystem  502 - 1  via path  506 - 1 - 1  and to air-interface subsystem  502 - 2  via path  506 - 2 - 1 . Antenna switch  503  accepts signals from air-interface subsystem  502 - 1  via path  506 - 1 - 2  and from air-interface subsystem  502 - 2  via path  506 - 2 - 2 . It will be clear to those skilled in the art how to make and use antenna switch  503 .  
         [0050]    Antenna subsystem  504  couples the electrical signals of antenna switch  503  with the wireless shared-communications channel. It will be clear to those skilled in the art how to make and use antenna subsystem  504 .  
         [0051]    [0051]FIG. 6 depicts a block diagram of host processor  501  in accordance with the first illustrative embodiment of the present invention.  
         [0052]    Host processor  601  is a general-purpose processor that is capable of performing the tasks described below and with respect to FIG. 8. In some embodiments of the present invention, host processor  601  executes universal serial bus (OSB) drivers that are used to interface with air-interface subsystems  502 - 1  and  502 - 2 . It will be clear to those skilled in the art, after reading this specification, how to make and use host processor  601 .  
         [0053]    Wireline shared-communications channel  602  is an electrical connection that connects air-interface subsystems  502 - 1  and  502 - 2  with host processor  601 . Wireline shared-communications channel  602  is compliant with the peripheral component interconnect (PCI) or PCI-X standard. In some alternative embodiments of the present invention, wireline shared-communications channel  602  is compliant with a different protocol. It will be clear to those skilled in the art how to make and use wireline shared-communications channel  602 .  
         [0054]    Memory  603  is capable of storing programs and data used by host processor  601 . It will be clear to those skilled in the art how to make and use memory  603 .  
         [0055]    [0055]FIG. 7 depicts a block diagram of air-interface subsystem  502 -i, for i=1 and 2, in accordance with the first illustrative embodiment of the present invention. Air-interface subsystem  502 -i comprises processor  701 -i, host interface  702 -i, memory  703 -i, receiver  704 -i, and transmitter  705 -i, interconnected as shown. Air-interface subsystem  502 - 1  also comprises lead  507 - 1  for controlling antenna switch  503 .  
         [0056]    Processor  701 -i is a general-purpose processor that is capable of performing the tasks described below and with respect to FIG. 8. It will be clear to those skilled in the art, after reading this specification, how to make and use processor  701 -i.  
         [0057]    Host interface  702 -i is a circuit that provides air-interface subsystem  502 -i with an interface to host  501 . It will be clear to those skilled in the art how to make and use host interface  702 -i.  
         [0058]    Memory  703 -i is capable of storing programs and data used by processor  701 -i. It will be clear to those skilled in the art how to make and use memory  703 -i.  
         [0059]    Receiver  704 -i is a circuit that is capable of receiving frames from antenna switch  503 , in well-known fashion, and of forwarding them to processor  701 -i. It will be clear to those skilled in the art how to make and use receiver  704 -i.  
         [0060]    Transmitter  705 -i is a circuit that is capable of receiving frames from processor  701 -i, in well-known fashion, and of transmitting those frames to antenna switch  503 . It will be clear to those skilled in the art how to make and use transmitter  705 -i.  
         [0061]    Air-interface subsystems  502 - 1  and  502 - 2  coordinate their use by exchanging coordination messages. For example, when air-interface subsystem  502 - 1  has to transmit immediately or at some point in the future, it notifies air-interface subsystem  502 - 2 . Similarly, if air-interface subsystem  502 - 1  is neither transmitting nor receiving, it notifies air-interface subsystem  502 - 2  that an opportunity exists to use the wireless shared-communications channel.  
         [0062]    The messages that coordinate air-interface subsystems  502 - 1  and  502 - 2  are exchanged through host  501 .  
         [0063]    At host  501 , in some embodiments, software that is inserted at the operating system level or at the driver level (or both) recognizes incoming messages from one air-interface subsystem as being intended for the other air-interface subsystem. For example, a driver-level “shim” interface running on processor  601  can be used to intercept incoming messages from air-interface subsystem  502 - 2  and route them to air-interface subsystem  502 - 1 . A “shim” is a software component inserted into the logical space between a higher-level program in host  501  and a program providing a communications service (e.g., a Bluetooth driver, an IEEE 802.11 driver, etc.). In this case, the shim intercepts the request on a first driver triggered by the incoming message from air-interface subsystem  502 - 2 , translates the request, and routes the request to a second driver to transmit an outgoing message to air-interface subsystem  502 - 1 . Higher-level entities running on processor  601  (e.g., application programs, etc.) need not be aware of the messages going back and forth between the air-interface subsystems. It will be clear to those skilled in the art how to insert software in host  501  to handle incoming messages from one device external to host  501  that are intended for another device external to host  501 .  
         [0064]    [0064]FIG. 8 depicts a message flow diagram in accordance with the first illustrative embodiment of the present invention. In FIG. 8, each of the two logical paths between (i) host  501  and air-interface subsystem  502 - 1  and (ii) host  501  and air-interface subsystem  502 - 2  coincide with a different physical path (i.e.,  505 - 1  and  505 - 2 ).  
         [0065]    With message  801 , processor  701 - 1  of air-interface subsystem  502 - 1  transmits a first coordination message to host  501  via wireline shared-communications channel  602 , which first message is addressed to air-interface subsystem  502 - 2 .  
         [0066]    Depending on the status of air-interface subsystem  502 - 1 , the first message conveys:  
         [0067]    1. a transmit inhibit signal, through which air-interface subsystem  502 - 1  commands air-interface subsystem  502 - 2  to inhibit transmitter  705 - 2 ; or  
         [0068]    2. a polite request signal, which indicates to air-interface subsystem  502 - 2  that air-interface subsystem  502 - 1  has a data block to transmit, but does not necessarily have to send it right at that moment.  
         [0069]    With message  802 , host  501  forwards the first coordination message to air-interface subsystem  502 - 2  via wireline shared-communications channel  602 .  
         [0070]    With message  803 , processor  702 - 2  generates a second coordination message delivery to processor  702 - 1 , and, therefore, processor  702 - 2  transmits the message to host  501 . The second coordination message can be generated in response to the receipt of the first coordination message or it can independent of the first coordination message.  
         [0071]    Depending on the status of air-interface subsystem  502 - 2 , the second message conveys:  
         [0072]    1. a transmitting indication signal, which indicates if air-interface subsystem  502 - 2  is transmitting signals over the air;  
         [0073]    2. a receiving indication signal, which indicates if air-interface subsystem  502 - 2  is receiving (or attempting to receive) signals from over the air; or  
         [0074]    3. an idle indication signal, which indicates if air-interface subsystem  502 - 2  is neither in transmit mode nor in receive mode (but is still powered on).  
         [0075]    With message  804 , host  501  forwards the second message to air-interface subsystem  502 - 1  via wireline shared-communications channel  602 . In this way, air-interface subsystems  502 - 1  and  502 - 2  can exchange the information to coordinate the use of the shared-communications channel.  
         [0076]    [0076]FIG. 9 depicts a block diagram of wireless station  900  in accordance with the second illustrative embodiment of the present invention. Wireless station  900  is a machine that supports two distinct wireless air-interface protocols for the purpose of transmitting and receiving data over the air via a shared-communications channel. Wireless station  900  comprises: host  901 , air-interface subsystem  902 - 1 , air-interface subsystem  902 - 2 , antenna switch  903 , and antenna subsystem  904 , interconnected as shown.  
         [0077]    Host  901  is a machine that is capable of generating one or more data blocks to be transmitted over the wireless shared-communications channel by air-interface subsystems  902 - 1  and  902 - 2 , in well-known fashion. Host  901  is also capable of processing one or more data blocks that it receives from the wireless shared-communications channel by air-interface subsystems  902 - 1  and  902 - 2 , in well-known fashion. The salient details of host  901  are described below and with respect to FIG. 10.  
         [0078]    Although the illustrative embodiment comprises two air-interface subsystems, 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 comprises any number of air-interface subsystems.  
         [0079]    Each of air-interface subsystems  902 - 1  and  902 - 2  comprises a radio that enables host  901  to communicate via the wireless shared-communications channel using a different air-interface protocol.  
         [0080]    Air-interface subsystem  902 - 1  enables host  901  to communicate via the IEEE 802.11 air-interface protocol. Air-interface subsystem  902 - 1  communicates with host  901  via path  905 - 1 .  
         [0081]    Air-interface subsystem  902 - 2  enables host  901  to communicate via the Bluetooth air-interface protocol. Air-interface subsystem  902 - 2  communicates with host  901  via path  905 - 2 .  
         [0082]    Although the illustrative embodiment enables communication via the IEEE 802.11 and Bluetooth air-interface protocols, 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 other air-interface protocols.  
         [0083]    Each of air-interface subsystems  902 - 1  and  902 - 2  is capable of receiving one or more data blocks from host  901  and transmitting, over the wireless shared-communications channel, one or more data frames that comprises the payload data received from host  901 . Each of air-interface subsystems  902 - 1  and  902 - 2  is also capable of receiving one or more data frames from the wireless shared communications channel and sending to host  901  one or more data blocks comprising the payload data from the data frames. It will be clear to those skilled in the art, after reading this specification, how to make and use air-interface subsystems  902 - 1  and  902 - 2 .  
         [0084]    Antenna switch  903  enables air-interface subsystems  902 - 1  and  902 - 2  to share antenna subsystem  904 . Antenna switch  903  provides signals to air-interface subsystem  902 - 1  via path  906 - 1 - 1  and to air-interface subsystem  902 - 2  via path  906 - 2 - 1 . Antenna switch  903  accepts signals from air-interface subsystem  902 - 1  via path  906 - 1 - 2  and from air-interface subsystem  902 - 2  via path  906 - 2 - 2 . It will be clear to those skilled in the art how to make and use antenna switch  903 .  
         [0085]    Antenna subsystem  904  couples the electrical signals of antenna switch  903  with the wireless shared-communications channel. It will be clear to those skilled in the art how to make and use antenna subsystem  904 .  
         [0086]    [0086]FIG. 10 depicts a block diagram of air-interface subsystem  902 - 1  in accordance with the second illustrative embodiment of the present invention. Air-interface subsystem  902 - 1  comprises processor  1001 - 1 , multi-radio host interface  1002 - 1 , memory  1003 - 1 , receiver  1004 - 1 , and transmitter  1005 - 1 , interconnected as shown.  
         [0087]    Processor  1001 - 1  is a general-purpose processor that is capable of performing the tasks described below and with respect to FIG. 11. It will be clear to those skilled in the art, after reading this specification, how to make and use processor  1001 - 1 .  
         [0088]    Multi-radio host interface  1002 - 1  is a circuit that provides air-interface subsystem  902 - 1  with a physical and logical interface to host  901 . Furthermore, multi-radio host interface  1002 - 1  provides a physical interface to air-interface subsystem  902 - 2  and acts as a logical conduit for messages exchanged between host  901  and air-interface subsystem  902 - 2 . In other words, multi-radio host interface  1002 - 1  does not switch messages between processor  1001 - 1  and air-interface subsystem  902 - 2 . Instead, messages between processor  1001 - 1  and air-interface subsystem  902 - 2  are physically routed by multi-radio host interface  1002 - 1  to host  901  which re-routes them back to multi-radio host interface  1002 - 1  for forwarding to their final destination. It will be clear to those skilled in the art, after reading this specification, how to make and use multi-radio host interface  1002 - 1 . Furthermore, it will be clear to those skilled in the art, after reading this specification, how to make and use host  901  to re-route messages from one air-interface subsystem to another air-interface subsystem.  
         [0089]    Memory  1003 - 1  is capable of storing programs and data used by processor  1001 - 1 . It will be clear to those skilled in the art how to make and use memory  1003 - 1 .  
         [0090]    Receiver  1004 - 1  is a circuit that is capable of receiving frames from antenna switch  603 , in well-known fashion and of forwarding them to processor  1001 - 1 . It will be clear to those skilled in the art how to make and use receiver  1004 - 1 .  
         [0091]    Transmitter  1005 - 1  is a circuit that is capable of receiving frames from processor  1001 - 1 , in well-known fashion, and of transmitting those frames to antenna switch  603 . It will be clear to those skilled in the art how to make and use transmitter  1005 - 1 .  
         [0092]    [0092]FIG. 11 depicts a block diagram of air-interface subsystem  902 - 2 , in accordance with the second illustrative embodiment of the present invention. Air-interface subsystem  902 - 2  comprises processor  1001 - 2 , multi-radio host interface  1002 - 2 , memory  1003 - 2 , receiver  1004 - 2 , and transmitter  1005 - 2 , interconnected as shown.  
         [0093]    Processor  1001 - 2  is a general-purpose processor that is capable of performing the tasks described below and with respect to FIG. 11. It will be clear to those skilled in the art, after reading this specification, how to make and use processor  1001 - 2 .  
         [0094]    Memory  1003 - 2  is capable of storing programs and data used by processor  1001 - 2 . It will be clear to those skilled in the art how to make and use memory  1003 - 2 .  
         [0095]    Receiver  1004 - 2  is a circuit that is capable of receiving frames from antenna switch  603 , in well-known fashion, and of forwarding them to processor  1001 - 2 . It will be clear to those skilled in the art how to make and use receiver  1004 - 2 .  
         [0096]    Transmitter  1005 - 2  is a circuit that is capable of receiving frames from processor  1001 - 1 , in well-known fashion, and of transmitting those frames to antenna switch  603 . It will be clear to those skilled in the art how to make and use transmitter  1005 - 2 .  
         [0097]    [0097]FIG. 12 depicts a message flow diagram in accordance with the second illustrative embodiment of the present invention. In the second described configuration, both of the logical paths between i) host  901  and air-interface subsystem  902 - 1  and ii) host  901  and air-interface subsystem  902 - 2  share a single physical path (i.e., between host  901  and air-interface subsystem  902 - 1 ).  
         [0098]    Air-interface subsystems  902 - 1  and  902 - 2  coordinate with each other in order to coexist on the same shared-communications channel. The coordination signaling that is exchanged between air-interface subsystems  902 - 1  and  902 - 2  comprise transmit requests and transmit opportunity indications. For example, when air-interface subsystem  902 - 1  has to transmit immediately or at some point in the future, it has to be able to notify air-interface subsystem  902 - 2 . As another example, if air-interface subsystem  902 - 1  is neither transmitting nor receiving, it can notify air-interface subsystem  902 - 2  that an opportunity exists to use the wireless shared-communications channel.  
         [0099]    With message  1101 , processor  1001 - 1  of air-interface subsystem  902 - 1  generates a first coordination message for delivery to processor  1001 - 2 , and, therefore, processor  1001 - 1  transmits the message to multi-radio host interface  1002 - 1 .  
         [0100]    Depending on the status of air-interface subsystem  902 - 1 , the first coordination message conveys:  
         [0101]    1. a transmit inhibit signal, through which air-interface subsystem  902 - 1  commands air-interface subsystem  902 - 2  to inhibit transmitter  1005 - 2 ; or  
         [0102]    2. a polite request signal, which indicates to air-interface subsystem  902 - 2  that air-interface subsystem  902 - 1  has a data block to transmit, but does not necessarily have to send it right at that moment.  
         [0103]    With message  1102 , multi-radio host interface  1002 - 1  forwards the first coordination message to host  901  via wireline shared-communications channel  905 .  
         [0104]    With message  1103 , host  901  re-routes the first coordination message back to multi-radio host interface  1002 - 1  for delivery to processor  1001 - 2  of air-interface subsystem  902 - 1 .  
         [0105]    With message  1104 , multi-radio host interface  1002 - 1  forwards the first coordination message to processor  1001 - 2 , and processor  1001 - 2  processes the first coordination message accordingly.  
         [0106]    With message  1105 , processor  1001 - 2  generates a second coordination message delivery to processor  1001 - 2 , and, therefore, processor  1001 - 2  transmits the message to multi-radio host interface  1002 - 1 . The second coordination message can be generated in response to the receipt of the first coordination message or it can independent of the first coordination message.  
         [0107]    Depending on the status of air-interface subsystem  502 - 2 , the second message conveys:  
         [0108]    1. a transmitting indication signal, which indicates if air-interface subsystem  902 - 2  is transmitting signals over the air;  
         [0109]    2. a receiving indication signal, which indicates if air-interface subsystem  902 - 2  is receiving (or attempting to receive) signals from over the air; or  
         [0110]    3. an idle indication signal, which indicates if air-interface subsystem  902 - 2  is neither in transmit mode nor in receive mode (but is still powered on).  
         [0111]    With message  1106 , multi-radio host interface  1002 - 1  forwards the second coordination message to host  901 .  
         [0112]    With message  1107 , host  901  re-routes the second coordination message to multi-radio host interface  1002 - 1  for delivery to processor  1001 - 1 .  
         [0113]    With message  1108 , multi-radio host interface  1002 - 1  forwards the second coordination message to processor  1001 - 1 , and processor  1001 - 1  processes the second coordination message accordingly.  
         [0114]    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. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.