Abstract:
Methods and systems are disclosed for interoperations between single-radio (channel switching) devices, dual radio devices, and single-radio (always-on) devices in radio communication systems, both with and without a safety channel. The methods and systems may be applied in communication systems for wireless access in vehicular environments (WAVE), such as those according to IEEE 802.11p. When there is a safety channel, some embodiments add a Safety Channel Interval within an operation period. Other embodiments disclose how various device types can operate to coordinate safety message transmissions, both with and without a safety channel.

Description:
RELATED APPLICATION 
     The present application relates to and claims the benefit of priority to U.S. Provisional Patent Application No. 61/252,849 filed Oct. 19, 2009 which is hereby incorporated by reference in its entirety for all purposes as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to interoperability among various wireless devices for vehicular communications, and, more particularly, to enabling interoperability of dual-radio and single-radio devices for vehicular multi-channel operations. 
     Referring now to  FIG. 1 , the problem of interoperability among various wireless devices for vehicular communications is illustrated. There are two types of devices in close vicinity: 
     1) Legacy single-radio devices  102  that operate on the control channel (channel  176  in the US) for support both safety application and control of service applications and a service channel for support data delivery of service applications through periodic channel switching, and 
     2) Advanced dual-radio devices  104  that tune one of their radios always on the safety channel (channel  172  in the US) and use the other radio switching channels between the control channel (channel  176 ) and a service channel to support non-safety service applications. 
     Note that the Control Channel (CCH) Interval of the advanced dual-radio devices would be smaller (or much smaller) than that of the legacy single radio devices, since all safety message communications should use the dedicated Safety Channel and only the control message communications for support service application should be on the CCH, as opposed to the legacy single radio devices that have to provide supports for safety applications and control of service application on the CCH. A smaller CCH interval of the advanced dual-radio devices allows a larger SCH interval that can more effectively support data delivery of service applications. 
     A dedicated radio of the advanced dual-radio device that is always on the Safety channel allows the safety-critical communications to be conducted on a much less congested RF channel such that the packet delivery performance can be significantly improved. 
     When the legacy single radio devices and the advanced dual-radio devices are communicating in close proximity, safety-critical messages communications can not be effectively conducted among these different types of devices due to the fact that the specifications of channel operation of these devices are not fully interoperable. 
     Due to the longer length of the CCH interval of the single-radio device compared to the one of the dual-radio devices, the safety message transmitted by the legacy single-radio devices on the CCH may not be received by the dual-radio devices in a timely manner. 
     Since the advance dual-radio devices transmit the safety messages on the Safety channel that the legacy single-radio devices do not tune to, those safety messages on the safety channel will not be received by the legacy single-radio devices. 
     What is desired is a method for enabling interoperability among the legacy and advanced wireless vehicular devices for ensuring communication reliability of safety-critical applications, while maintaining the desirable advantages of these devices (i.e. low-cost, simple operations for the legacy devices, and higher performance and spectrum efficient for the advanced devices). 
     SUMMARY OF THE INVENTION 
     According to the present invention, a method for interoperations between single-radio (channel switching) devices and single-radio (always-on) devices comprises single-radio (always-on) devices keep announcing safety messages on the safety channel at any time and keep monitoring packet transmissions on the safety channel at all times when it not transmitting in a normal mode; single-radio (channel switching) devices announce safety messages on the safety channel and keep monitoring packet transmissions on the safety channel during a safety channel interval; and once a single-radio (always-on) device detects the existence of a single-radio (channel-switching) device after successfully receiving at least one safety message transmitted by the single-radio (channel-switching) device during the safety channel interval, it enters to an interoperation mode, in which the single-radio (always-on) device shall transmit safety messages at least during the safety channel interval of the single-radio (channel-switching) device. 
     Methods for interoperations between single-radio devices and dual-radio devices, with and without a safety channel, are also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  illustrates the interoperability problem among various wireless devices for vehicular communications; 
         FIG. 2  illustrates current (state of the art) allocation of channel operation intervals within an operation period for the single-radio devices that perform channel switching; 
         FIG. 3  illustrates a proposed allocation of channel operation intervals within an operation period for the single-radio devices that perform channel switching by adding a SafetyCH interval for dedicated communications of the safety channel according to the present invention; 
         FIG. 4  illustrates channel operations of the single-radio devices that are always on the safety channel; 
         FIG. 5  illustrates a proposed allocation of channel operation intervals within an operation period for the dual-radio devices that are performing channel switching on the CCH and SCH on one radio and are always on the safety channel on the other radio; 
         FIG. 6  illustrates interoperations between single-radio (channel switching) devices and single-radio (always-on) devices; 
         FIG. 7  illustrates interoperations between single-radio (channel switching) devices and dual-radio devices—switching from the normal mode to the interoperation mode; 
         FIG. 8  illustrates interoperations between single-radio (channel switching) devices and dual-radio devices—communications in the interoperation mode on the safety channel, control channel, and service channel; 
         FIG. 9  illustrates enabling dual-single radio devices interoperability using duplicated packet transmissions; 
         FIG. 10  illustrates current (state of the art) allocation of channel operation intervals within an operation period for the single-radio devices performing channel switching; 
         FIG. 11  illustrates channel operation of the single-radio devices that are always on the control channel; 
         FIG. 12  illustrates allocation of channel operation intervals within an operation period for the dual-radio devices that are always on the CCH with one radio and on one of the SCHs on the other radio; 
         FIG. 13  illustrates interoperations between single-radio (channel switching) devices and single-radio (always-on) devices; 
         FIG. 14  illustrates interoperations between single-radio (channel switching) devices and dual-radio devices—switching to the interoperation mode and communications in the interoperation mode on the control channel and service channel; and 
         FIG. 15  illustrates interoperability among different device types when the safety channel is not available. 
     
    
    
     DETAILED DESCRIPTION 
     Interoperability among the dual-radio and single-radio devices is now described, including interoperability requirements. 
     Interoperability is required among dual-radio devices that are:
         a. Radio  1 : Always on the safety channel for the communications of safety applications   b. Radio  2 : Always on either Control channel or Service channel, or switching between Control channel and service channel, to support services and other control applications.       

     Interoperability is also required among dual-radio devices that are:
         a. Radio  1 : Always on the control channel for the communications of safety applications   b. Radio  2 : Always on the services channel to support services and other control applications.       

     Interoperability is also required among single-radio devices that are always on the safety channel. 
     Interoperability is also required among single-radio devices that are always on the control channel. 
     Interoperability is also required among single-radio devices that are switching between the safety channel, control channel, and the service channel. 
     Interoperability is also required among single-radio devices that are switching between the control channel and the service channel. 
     When the safety channel is available, it is required that all devices shall only use the safety channel for support safety applications. 
     Therefore in this case interoperability is required between dual-radio devices that are:
         a. Radio  1 : Always on the safety channel for the communications of safety applications.   b. Radio  2 : Always on either control channel or service channel, or switching between control channel and service channel, to support services and other control applications.       

     Interoperability in this case is also required between single-radio devices that are always on the safety channel. 
     Interoperability in this case is also required between single-radio devices that are switching between the safety channel, control channel, and the service channel. 
     One the other hand, when the safety channel is not available the control channel shall be used to support the safety applications. 
     Therefore in this case interoperability is required between in this case between dual-radio devices that are:
         a. Radio  1 : Always on the control channel for the communications of safety applications   b. Radio  2 : Always on the services channel to support services and other control applications.       

     Interoperability in this case is also required between single-radio devices that are always on the control channel. 
     Interoperability in this case is also required between single-radio devices that are switching between the control channel and the service channel. 
     Interoperability among radio devices that may use a different channel for safety initially is not addressed, since they will converge to use the safety channel if the safety channel is available or the control channel (when the safety channel is not available) for safety applications. 
     Interoperability issues for these two cases are addressed: the safety channel (channel  172 ) is available; and the safety channel is NOT available. 
     Interoperability when the safety channel is available is now addressed 
     It is required that when the safety channel is available, all devices shall only use the safety channel for support safety applications. Therefore the types of devices that need to interoperable in this case are dual-radio devices that are (Radio  1 ) always on the safety channel for the communications of safety applications; and (Radio  2 ) always on either the control channel or service channel, or switching between the control channel and service channel, to support services and other control applications. Single-radio devices that are always on the safety channel and single-radio devices that are switching between the safety channel, control channel, and the service channel also need to be interoperable. 
     A proposed scheme for interoperability according to the present invention is now described, including allocating a “Safety Channel Interval” in the operation periods. A “Safety Channel Interval” is therefore added to enable the necessary interoperability among different devices. 
     Allocation for single-radio devices performing channel switching is now described. 
       FIG. 2  shows the current allocation of channel operation interval within an operation period for the single-radio devices  202  that perform channel-switching. Only operation intervals for the control channel and the service channel are allocated (i.e. CCH interval and SCH interval). Communications for supporting safety applications are conducted within the CCH interval, mixing with communications for supporting services applications (on the control channel). 
       FIG. 3  shows the newly proposed allocation of channel operation intervals within an operation period for the single radio devices  302  that perform channel switching. A new operation interval for the safety channel (SafetyCH Interval) is allocated together with the control channel and the service channel intervals. Communications for supporting safety applications are conducted on the safety channel within the dedicated SafetyCH Interval, without mixing with communications for supporting services applications. 
     The CCH interval for communications on the control channel is reduced as compared to the one in the current (state of the art) allocation, since the communication load for safety applications is now moved to the SafetyCH Interval and therefore the CCH interval only needs to support control messaging for service applications. 
     Allocation for single-radio devices always on the safety channel is now described. 
     The always-on Single-radio devices stay always on the safety channel for transmitting and receiving packets/messages of safety applications. 
       FIG. 4  shows the newly proposed channel operation within an operation period for the single radio devices  402  that are always on the safety channel. 
     Allocation for dual-radio devices is now described. 
       FIG. 5  shows the proposed allocation of channel operation interval, within an operation period for the dual-radio devices  502  that are performing channel-switching on the CCH and SCH on one radio and are always on the Safety Channel on the other radio. The CCH interval of the dual-radio devices is set to equal to the CCH interval of the single-radio devices that perform channel switching. The SCH interval of the dual-radio devices is the rest of the operation period excluding its CCH Interval. 
     Referring now to  FIG. 6 , the method according to the present invention for interoperations between single-radio (channel switching) devices and single-radio (always-on) devices is now described: 
     1) Single-radio (always-on) devices keep announcing safety messages on the safety channel at any time and keep monitoring packet transmissions on the safety channel at all times when it not transmitting. This operation mode is called the “Normal Mode”. 
     2) Single-radio (channel switching) devices announce safety messages on the safety channel and keep monitoring packet transmissions on the safety channel during the Safety Channel Interval. 
     3) Once a single-radio (always-on) device detects the existence of a single-radio (channel-switching) device after successfully receiving at least one safety message transmitted by the single-radio (channel-switching) device during the safety channel interval, it enters to the “Interoperation Mode”, in which the single-radio (always-on) device shall transmit safety messages at least during the safety channel interval of the single-radio (channel-switching) device. Note that the safety channel interval of the single-radio (channel-switching) device must be well-known/standardized. The devices that can directly communicate with one another are called “One-Hop” neighbors. 
     4) A single-radio (always-on) device that does not detect any single-radio (channel-switching) device (i.e. the device being outside of the One-Hop neighborhood) can stay in the “Normal” mode. 
     5) Single-radio (channel switching) devices operate as usual. 
     Referring now to  FIG. 7 , interoperations between single-radio (channel switching) devices and dual-radio devices is now described: 
     1) A dual-radio device uses one of its two radios to keep announcing safety messages on the safety channel at any time and keep monitoring packet transmissions on the safety channel at all time when it is not transmitting. This radio is called the “always on safety channel” radio. It uses the other radio (called channel switching radio) that switching between the control channel and the service channel to support data services. This operation mode is called the “Normal Mode” of the dual devices. 
     2) Single-radio (channel switching) devices announce safety messages on the safety channel and keep monitoring packet transmissions on the safety channel during the safety channel interval. 
     3) Once a dual radio device detects the existence of a single-radio (channel-switching) device by successfully receiving at least one safety message on the safety channel transmitted by the single-radio (channel-switching) device during the safety channel interval of the single radio (channel switching) devices, it enters to the “Interoperation Mode”, in which the dual radio device shall transmit safety messages at least during the safety channel interval of the single-radio (channel-switching) device. Such single-radio (channel-switching) devices detection can also be done by successfully receiving at least one control packets on the control channel transmitted by the single-radio (channel-switching) device during the fully synchronized CCH interval. The devices that can directly communicate with one another are called “One-Hop” neighbors. In the interoperation mode, the dual-radio device uses its “channel switching” radio to exchange control packets on the control channel with the single-radio (channel-switching) devices within the “One-Hop” neighborhood during the fully synchronized CCH interval. It shall exchange service packets on the service channel with the single-radio (channel-switching) devices within the “One-Hop” neighborhood during the SCH interval of the single-radio (channel-switching) devices. Note that the safety channel interval, CCH interval, and the SCH interval of the single-radio (channel-switching) device must be well-known/standardized. 
     4) A dual device that does not detect any single-radio (channel-switching) device (i.e. the device being outside of the One-Hop neighborhood) can stay in the “Normal” mode. 
     5) Single-radio (channel switching) devices operate as usual. 
     An example of interoperability among different device types when a safety channel is available is shown in  FIGS. 8 and 9 .  FIG. 8  illustrates interoperations between single-radio (channel switching) devices and dual radio devices—communications in the interoperation mode on the safety channel, control channel, and service channel.  FIG. 9  illustrates enabling dual-single radio devices interoperability using duplicated packet transmissions. 
     Interoperability when the safety channel is not available is now described. When the safety channel is not available under a regulatory domain, only the control channel and the service channels can be used. All safety applications, together with the control applications, will use the control channel. 
     Therefore the types of devices that need to be interoperable in this case are dual-radio devices that are (Radio  1 ) always on the control channel for the communications of safety applications and control for service applications; and (Radio  2 ) are always on the service channel to support data services. Single-radio devices that are always on the control channel and single-radio devices that are switching between the control channel, and the service channel must also be interoperable. 
     A proposed scheme for interoperability including channel interval allocation according to the present invention is now described. Channel interval allocation for single-, radio devices performing channel switching is initially described. 
       FIG. 10  shows the current allocation of channel operation interval within an operation period for the single-radio devices  1002  that perform channel-switching. Operation intervals for the control channel and the service channel are allocated (i.e. CCH interval and SCH interval). Communications for supporting safety applications are conducted within the CCH interval, mixing with communications for supporting services applications (on the control channel). 
     Channel allocation for single-radio devices always on the control channel is now described. The always-on single-radio devices stay always on the control channel for transmitting and receiving packets/messages of safety applications.  FIG. 11  shows the channel operation within an operation period for the single radio devices  1102  that are always on the control channel. 
     Allocation for dual-radio devices is now described.  FIG. 12  shows the allocation of channel operation interval within an operation period for the dual-radio devices  1202  operating on the control channel and the service channels. Every dual-radio device stays always on the control channel (CCH) with one of its radios and on one of the service channels (SCHs) with the other radio. 
     Interoperation procedures according to the present invention are now described in further detail. 
     Interoperations between single-radio (channel switching) devices and single-radio (always-on) devices is now described with respect to  FIG. 13 : 
     1) Single-radio (always-on) devices keep announcing safety messages on the control channel at any time and keep monitoring packet transmissions on the control channel at all time when it is not transmitting. This operation mode is called the “Normal Mode”. 
     2) Single-radio (channel switching) devices announce safety messages on the control and keep monitoring packet transmissions on the control channel during the Safety Channel Interval when it is not transmitting. 
     3) Once a single-radio (always-on) device detects the existence of a single-radio (channel-switching) device after successfully receiving at least one safety message transmitted by the single-radio (channel-switching) device during the CCH Interval of the single-radio (channel-switching) device, it enters to the “Interoperation Mode”, in which the single-radio (always-on) device shall transmit safety messages at least during the CCH Interval of the single-radio (channel-switching) device. Note that the CCH Interval of the single-radio (channel-switching) device must be well-known/standardized. The devices that can directly communicate with one another are called “One-Hop” neighbors. 
     4) A single-radio (always-on) device that does not detect any single-radio (channel-switching) device (i.e. the devices being outside of the One-Hop neighborhood) can stay in the “Normal” mode. 
     5) Single-radio (channel switching) devices operate as usual. 
     Interoperations between single-radio (channel switching) devices and dual-radio devices is now described with respect to  FIG. 14 : 
     1) A dual-radio device uses one of its two radios to keep announcing safety messages on the CCH at any time and keep monitoring packet transmissions on the CCH at all time when it is not transmitting. This radio is called the “always on CCH” radio. It uses the other radio (called “always on SCH” radio) that stays on the SCH to support data services. This operation mode is called the “Normal Mode” of the dual devices. 
     2) Single-radio (channel switching) devices announce safety messages on the CCH and keep monitoring packet transmissions on the CCH during the CCH interval. 
     3) Once a dual radio device detects the existence of a single-radio (channel-switching) device by successfully receiving at least one safety message on the CCH transmitted by the single-radio (channel-switching) device during the CCH Interval of the single radio (channel switching) devices, it enters to the “Interoperation Mode”, in which the dual radio device shall transmit safety messages at least during the CCH Interval of the single-radio (channel-switching) device. The devices that can directly communicate with one another are called “One-Hop” neighbors. In the interoperation mode, the dual-radio device shall exchange service packets on the service channel with the single-radio (channel-switching) devices within the “One-Hop” neighborhood during the SCH interval of the single-radio (channel-switching) devices. Note that the CCH Interval, and SCH interval of the single-radio (channel-switching) device must be well-known/standardized. 
     4) A dual device that does not detect any single-radio (channel-switching) device (i.e. the device being outside of the One-Hop neighborhood) can stay in the “Normal” mode. 
     5) Single-radio (channel switching) devices operate as usual. 
     An example of interoperability among different device types when a safety channel is not available is shown in  FIG. 15 . A single-radio device announces its device type. A “Safety Channel Interval” is added to enable the necessary interoperability among different devices. Only the behavior of the dual-radio device that is within a one-hop neighborhood of a single-radio device needs to be changed. Duplicated messages are transmitted optionally to enhance message reception probability. Desirable CCH/SCH splitting can be achieved in the dual-radio devices to support favorable services. 
     In a regulatory domain where a dedicated safety channel is available, it is recommended to use the procedures described above including a safety channel. In a regulatory domain where a dedicated safety channel is not available, it is recommended to use the procedures described above not including a safety channel. 
     While there have been described above the principles of the present invention, it is to be clearly understood that the foregoing description is made only by way of example and not as a limitation to the scope of the invention. Particularly, it is recognized that the teachings of the foregoing disclosure will suggest other modifications to those persons skilled in the relevant art. Such modifications may involve other features which are already known per se and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure herein also includes any novel feature or any novel combination of features disclosed either explicitly or implicitly or any generalization or modification thereof which would be apparent to persons skilled in the relevant art, whether or not such relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as confronted by the present invention. The Applicant hereby reserves the right to formulate new claims to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.