System and method for avoiding and resolving conflicts in a wireless mobile display digital interface multicast environment

The present Application for Patent is related to the following co-pending U.S. patent applications:

“Wireless Architecture for a Traditional Wire-Based Protocol”, U.S. patent application Ser. No. 11/624,642, filed on Jan. 18, 2007;

“Wireless Architecture for a Traditional Wire Based Protocol”, U.S. patent application Ser. No. 11/624,634, filed on Jan. 18, 2007; and

“Wireless Architecture for a Traditional Wire-Based Protocol”, U.S. patent application Ser. No. 12/179,411, filed Jul. 24, 2008, all filed concurrently herewith, assigned to the assignee hereof and expressly incorporated by reference herein.

1. Field

The presently claimed invention relates generally to the field of communications, and more specifically to the field of wireless communications in a network having multiple nodes.

2. Background

Recent trends in communications have demonstrated that visual content is becoming a more important aspect of both the communications themselves as well as the devices that enable such communications. For example, displays have become much more integral to the operation of mobile phones in recent years. The mobile display digital interface (MDDI) protocol has been adopted by many manufacturers and users as a cost-effective and low-power solution that enables high-speed short-range communication with a display device, for example a display portion of a clamshell-type or flip-phone. The MDDI protocol typically utilizes a miniature connector system and a thin flexible cable for connecting portable computing, communications and entertainment devices to displays, generally referred to as a host and a client, respectively. However, with the development of high-speed wireless technologies such as ultra wideband and 802.11n, there is a growing desire for wireless communications between computing platforms and displays. Wireless USB has been introduced as one option for wireless communication between devices. However, unlike a MDDI system, wireless USB operates within the framework of the wiMedia UWB MAC, which unfortunately ties the communications protocol very heavily to the underlying MAC structure, which in turn complicates operation of wireless USB systems making them less than optimal for many applications.

As noted above, in a wired MDDI system, the host and client devices are connected by actual cabling, which forms the basis for the association between the host and the client. In a wireless system; however, there is no automatic, physical link creating an association between the host and client, which can lead to numerous difficulties with association, security, inefficient use of air link bandwidth, and conflicting addresses, packets and/or communication protocols from differing hosts and/or clients.

Accordingly, there is a need in the art for a system and/or method for wireless MDDI communications that ensures proper association between a host and a client, as well as efficient and secure communications there between.

The presently claimed invention includes systems and methods for avoiding conflict in a wireless mobile display digital interface (WMDDI) environment including both host and client devices. In one aspect, the presently claimed invention includes a system and/or method that are configured for broadcasting a first multicast address by a first host to at least one first client in a predetermined geographic area and broadcasting the first multicast address by a second host to at least one second client in the predetermined geographic area.

The system and/or method can be further configured for determining a priority between the first host and the second host when the second host receives multicast packets transmitted by the first host and changing to a second multicast address by a least priority host of the first host and the second host.

In another aspect, the presently claimed invention includes a system and/or method for resolving and/or preventing conflicts in a multicast address digital communication system. The system and/or method of conflict resolution can include the step of receiving a first multicast address broadcast by a first device in a first predetermined geographic area at a second device in a predetermined geographic area wherein the first and second geographic areas are at least partially distinct from one another. Upon receipt, the second device can rebroadcast the first multicast address in the second predetermined geographic area, where it can be received by a third, distinct device in the second predetermined geographic area. In other aspects of the presently claimed invention, the third device can then determine if the first and second multicast addresses are identical, and if so, determine a priority between the first and second devices. If the first device is the priority device, then the third device can select and/or generate a third, distinct, multicast address. Likewise, if the second device is the priority device, then the first device can select and/or generate a third, distinct multicast address, thereby preventing any potential conflicts from arising between devices in the first and second predetermined geographic areas.

As described in greater detail below, the systems and/or methods described herein, the WMDDI protocol can be run on top of a high-speed wireless MAC without interfering with the wireless MAC itself, which is a significant drawback to the wireless USB system described above. Compartmentalization of the WMDDI from the wireless MAC greatly improves the efficiency and operation of the host and client communications, while reducing the overall cost of the systems described herein. Other features described herein include a service discovery function, a dynamic association/dissociation function, a mutual authentication and key exchange function, a link status function as well as various specific functionalities to preserve air link bandwidth. Other features and advantages of the presently claimed invention are described in detail below with reference to the following figures.

FIG. 1 is a schematic block diagram of a system for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 2 is a schematic block diagram of a system hierarchy in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 3 is a diagram of a system for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 4 is a flowchart depicting a method for avoiding conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 5 is a flowchart depicting a method for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 6 is a flowchart depicting a method for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 7 is a flowchart depicting a method for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

FIG. 8 is a flowchart depicting a method for avoiding conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention.

The presently claimed invention is described herein with reference to selected preferred features and aspects thereof with reference to the appended figures. It should be understood by those of skill in the art of communications that the foregoing descriptions are exemplary in nature only, and that the scope of the presently claimed invention is defined by the following claims.

As shown in FIG. 1 , a system 10 for avoiding and/or resolving conflicts in a WMDDI multicast environment in accordance with one aspect of the presently claimed invention includes a host device 12 that is wirelessly connectable to a client device 20 . Host device 12 can include a WMDDI sender module 14 and a wireless modem 16 , each of which is connectable to a host controller 18 adapted to control at least the communications functions of host device 12 , including at least those functions described in greater detail below with reference to FIGS. 2 through 8 . Host controller 18 can include for example any suitable combination of hardware, firmware, or software that is adapted to control the communications functions of host device 12 . Similarly, client device 12 can include a WMDDI receiver module 22 and a wireless modem 24 , each of which is connectable to a client controller 26 adapted to control at least the communications functions of client device 20 . Client controller 26 can also include, for example, any suitable combination of hardware, firmware, or software that is adapted to control the communications functions of client device 20 , including at least those functions described in greater detail below with reference to FIGS. 2 through 8 .

Each host device 12 and client device 20 can have a functional system hierarchy 30 , one aspect of which is shown in FIG. 2 . System hierarchy 30 can include for example a display/video/multimedia layer 32 that is layered on top of a WMDDI protocol layer 34 . WMDDI protocol layer 34 is shown layered on top of a high-speed wireless MAC layer 36 , which in turn can run on top of a high-speed wireless PHY layer 38 . As described more fully herein, WMDDI protocol layer 34 can include a plurality of functions, including but not limited to a service discovery function, a dynamic association/dissociation function, a mutual authentication and key exchange function, a link status function as well as various specific functionalities to preserve air link bandwidth.

As shown in FIG. 3 , in one preferred aspect of the presently claimed invention, system 10 is configured such that a first host H 1 is adapted to broadcast a first multicast address to at least one client device C 1 in a predetermined geographic area, i.e. within a signal range of first host H 1 . System 10 can be further configured so that a second host H 2 broadcasts the first multicast address to at least one second client C 2 in the same geographic area, and further such that first host H 1 and second host H 2 are configured to determine a priority when second host H 2 receives multicast address packets transmitted by first host H 1 , thereby avoiding any potential multicast address conflicts. Depending upon the priority between first host H 1 and second host H 2 , system 10 can be configured such that the least priority one of first host H 1 or second host H 2 changes to a second multicast address thereby resolving any existing and/or potential multicast address conflicts.

These and other aspects of the presently claimed invention help to alleviate conflict in a broader WMDDI system in which there are multiple hosts and multiple clients all within the same predetermined geographic area. For example, in a case with two hosts A and C and two clients B and D, it is possible in a typical WMDDI system for hosts A and C to have conflicts and/or non-secure communications depending upon the selected multicast addresses. If nodes A and B are in listening range of each other, and nodes B and C are in listening range of each other, and nodes C and D are in listening range of each other, then nodes A and D might possibly become linked if they share the same multicast address and there is no manner by which to determine proper priority and multicast address selection between the two hosts A and C. As such, aspects of the presently claimed invention include a two-hop transmission of a selected multicast address from the initiating host to a client (first hop), and from the client to at least a second host (second hop), so that the second host is aware of the selection of the multicast address and can, at the option of the second host, either reject the multicast address or accept the multicast address depending upon the priority of the devices (e.g., based on respective Media AccessControl addresses associated therewith). As described in more detail herein, the second host is adapted to avoid conflicts through the rejection or the multicast address and selection of a unique address or resolve existing conflicts by determining a priority address and maintaining its existing address or selecting a new address in response to the priority of the respective devices.

As shown in diagram 40 of FIG. 3 , first host H 1 intends to start a session with one or more clients and selects and broadcasts a PickedMulticastAddress (MA 2 ). Simultaneously, second host H 2 is starting its own session with second client C 2 using a PickedMulticastAddress, MA 1 . If the first host H 1 were to also select MA 1 as its multicast address, then first host H 1 might inadvertently start a session with second client C 2 . In order to avoid this situation, first host H 1 broadcasts its MA 2 message to at least first client C 1 that is within the predetermined geographic area. In response, first client C 1 hops the MA 2 to at least second host H 2 . If MA 2 is identical to MA 1 on which second host H 2 is in session with at least a second client C 2 , then if the address of second host H 2 is greater than the address of first host H 1 , second host H 2 responds to first client C 1 with a RejectMulticastAddress (RMA) message, which in turn is hopped back to first host H 1 so that first host H 1 is aware that there is an existing broadcast with the selected address and that second host H 2 has priority on that particular address, thus allowing first host H 1 to select a different multicast address. Alternatively, if MA 2 is distinct from MA 1 , then there is no conflict between first host H 1 and second host H 2 for the immediate sessions. Moreover, each of first host H 1 and second host H 2 are aware of the other's respective multicast address so each host will refrain from starting another session on the other's multicast address unless or until it is determined by both first host H 1 and second host H 2 that there is no conflict.

Returning to FIG. 1 , host device 12 can be configured for operation as first host H 1 and second host H 2 , and client device 20 can be configured for operation as first client C 1 and second client C 2 . As noted above, each host device 12 and client device 20 can include a host controller 18 and a client controller 26 , respectively, wherein each of the controllers are configured for operation and execution of the methodologies described herein. Controllers 18 and 26 may be implemented in hardware, firmware, software, and/or combinations thereof. In a hardware implementation, for example, a processing unit may be implemented within one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, micro-controllers, microprocessors, electronic devices, other devices units designed to perform the functions described herein, and/or combinations thereof.

For a firmware and/or software implementation of aspects of the presently claimed invention, the systems and/or methodologies may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. Any machine-readable medium tangibly embodying instructions may be used in implementing the methodologies described herein.

For example, software codes may be stored in a memory, for example the memory associated with one of host device 12 or client device 20 , and executed by respective controllers 18 and 26 . Memory can be implemented within the processor or external to the processor. As used herein the term “memory” refers to any type of long term, short term, volatile, nonvolatile, or other memory and is not to be limited to any particular type of memory or number of memories, or type of media upon which memory is stored.

As shown in FIG. 4 , in one aspect of the presently claimed invention, a method for selecting a multicast address to avoid conflicts in a digital communication system includes step S 102 , which recites broadcasting a first multicast address by a first host to at least one first client in a predetermined geographic area. In step S 104 , the method recites broadcasting the first multicast address by a second host to at least one second client in the predetermined geographic area; and in step S 106 method recites determining a priority between the first host and the second host when the second host receives multicast packets transmitted by the first host. The method of this preferred aspect of the presently claimed invention further includes step S 108 , which recites changing to a second multicast address by a least priority host of the first host and the second host.

In one variation of the method of the aspect shown in FIG. 4 , the method can further include the step of detecting the at least one second client being in the predetermined geographic area by the first host. The step of detecting the at least one second client can be executed according to the two-hop principle set forth with reference to FIG. 3 . The method can further include the steps of receiving the first broadcast multicast address by the at least one second client from the first host, and rebroadcasting the received first multicast address on a first hop count to the second host. As noted above with reference to FIG. 3 , the systems and methodologies described herein function to notify, streamline and prioritize communications within a WMDDI network by minimizing the potential for conflicting multicast addresses between two or more host devices.

Further details of the exemplary methodologies described herein are depicted in the flowchart of FIG. 5 , which pertains primarily to methodologies suitable for a host device 12 functioning in a system 10 such as that shown in FIG. 1 . In step S 110 , the host H 1 is powered up and in step S 112 the host H 1 selects a multicast address G 1 . After detection of a new client in step S 114 , host H 1 transmits its PickedMulticastAddress (PMA) message in the manner described above in step S 116 . Following transmission of the PMA, the host initiates a Multicast Conflict resolution timer in step S 118 which functions to set an upper bound on a time for which the host H 1 will wait to see if the multicast group address G 1 is already in use by a priority host. In step S 120 , the method recites one of waiting for a RejectMulticastAddress packet or the expiration of the Multicast Conflict Resolution timer. In step S 122 , the method shown in FIG. 5 queries whether a RejectMulticastAddress (G 1 ) has been received. If the answer is negative, then the method proceeds to step S 128 , in which it queries whether the Multicast Conflict Resolution timer has expired. If the Multicast Conflict Resolution timer has expired, then in step S 130 the method recites maintaining the multicast group address G 1 as the MAC address for the host's session. If the Multicast Conflict Resolution timer has not expired, then the method returns to step S 120 described above.

Returning to step S 122 , if a RejectMulticastAddress (G 1 ) has been received, then the method proceeds to step S 124 , which recites host H 1 verifying that the originating host address (e.g., MAC address) H 2 has priority over the address of host H 1 , i.e. address of itself. Upon verification, then the method proceeds to step S 126 , in which the method recites picking a different multicast address G 2 that is not G 1 , after which the method returns to step S 116 and transmits a new PickedMulticastAddress (G 2 ) packet. The exemplary method shown in FIG. 5 functions to ensure the priority of hosts as well as the distinctness of the multicast addresses. As such, in a system 10 such as that described above, each host therein is performing the foregoing steps to ensure that proper priority is allocated and further that each multicast address is unique within the predetermined geographic region.

FIG. 6 illustrates a methodology appropriate for a recipient such as a host device 12 or client device 20 such as that shown in system 10 described with reference to FIG. 1 . In step S 140 , the example method recites receiving a PickedMulticastAddress (G 1 ), and in step S 142 , the example method queries whether the device is already a member of a different group having the same group address G 1 . If the answer is negative, then the method proceeds to step S 160 , described in more detail below. If the answer is affirmative, then the method proceeds to step S 144 , in which it queries whether the address (e.g., MAC address) of the host initiating the multicast group has priority over the existing host of the device.

As noted above, the methodologies of the presently claimed invention ascertain both the priority and the uniqueness of the multicast addresses. As such, if the answer to the priority query S 144 is affirmative, then the example method queries whether the device is also the second host H 2 . If the answer is affirmative, then in step S 150 the host H 2 picks a different multicast address G 2 , which is different than G 1 , for its group and then initiates the procedure of sending a PickedMulticastAddress (G 2 ) as set forth above in step S 152 . If the answer to query S 146 is negative, then the device forwards the PickedMulticastAddress to the host H 2 . If the answer to the priority query S 144 is negative, then H 1 does not have priority over H 2 , and so in step S 154 the example method queries whether the client device is also the second host H 2 . If the response is negative, then the example method proceeds to step S 158 , which recites forwarding the PickedMulticastAddress packet to the host H 2 . If the response to query S 154 is affirmative, then the host H 2 broadcasts a Reject Multicast Packet intended for host H 1 by including the host's own unicast address of H 2 in step S 156 .

As noted above, in order to prevent inadvertent association between hosts and clients that are not necessarily in the same geographic region, the methodologies of the presently claimed invention employ at least a two-hop communication process. Accordingly, in step S 160 , the example method recites incrementing the hop count on the PickedMulticastAddress packet to ensure that a predetermined number of hops is attained. For example, in step S 162 the example method queries whether the hop count is less than two. If the response is affirmative, then the method proceeds to step S 164 to increment the hop count on the PickedMulticastAddress packet and broadcast to the client device's next hop neighbors. On the other hand, if the hop count is two or more, then the example method proceeds to step S 166 in which the PickedMulticastAddress packet is discarded as both the priority and uniqueness functions have been performed.

FIG. 7 illustrates another example method usable by a packet receiver such as a host or client device in a system of the type described herein. In step S 180 , the example method recites the step of receiving a PickedMulticastAddress (G 1 ) packet. In step S 182 , the method queries whether the receiver is a member of a different group that already has the same group address G 1 . If the query of step S 182 is answered in the negative, then the example method proceeds to step S 196 , which recites the step of forwarding the PickedMulticastAddress packet to the host H 2 . If the answer to the query of step S 182 is affirmative, then the method proceeds to step S 184 , in which the method further queries whether the receiving device is a second host H 2 . If the answer to the query of step S 184 is negative, then the method proceeds to step S 194 in which the PickedMulticastAddress is forwarded to the host H 2 .

Alternatively, if the answer to the query of step S 184 is affirmative, then the method proceeds to step S 186 in which it queries whether the address (e.g., MAC address) of the host initiating the multicast group has priority over the address of the host H 2 , which is the host for the current group. If the response to the query of step S 186 is negative, then in step S 192 the host H 2 broadcasts a RejectMulticastAddress packet destined for host H 1 , by including the host H 2 's address with a hop count equal to zero. If the response to the query of step S 186 is affirmative, then in step S 188 the host H 2 selects an alternate multicast address G 2 distinct from G 1 for its own multicast group. Following selection of the new multicast address G 2 , the method directs the host H 2 to initiate the procedure for sending PickedMulticastAddress (G 2 ) in step S 190 .

As in the previous example methods, in order to prevent inadvertent association between hosts and clients that are not necessarily in the same geographic region, the methodologies of the presently claimed invention employ at least a two-hop communication process. Accordingly, in step S 198 , the example method recites incrementing the hop count on the PickedMulticastAddress packet to ensure that a predetermined number of hops is attained. For example, in step S 200 the example method queries whether the hop count is less than two. If the response is affirmative, then the method proceeds to step S 202 to increment the hop count on the PickedMulticastAddress packet and broadcast to the device's next hop neighbors. On the other hand, if the hop count is two or more, then the example method proceeds to step S 204 in which the PickedMulticastAddress packet is discarded as both the priority and uniqueness functions have been performed.

Another example method usable by a packet receiver such as a host or client device in a system of the type described herein is shown in FIG. 8 . In particular, the example methodology set forth in FIG. 8 is usable by a device that is a member of a multicast group G 1 started by host H 2 in which the device has either received multicast packets from a different host H 1 or received a beacon, signal or packet indicating that host H 1 has started a different group with the same address G 1 . This can happen if two distinct groups come into wireless contact with each other either because of mobility or due to changes in the wireless environment. The example method shown in FIG. 8 begins in step S 210 in which the device detects a duplicate multicast group (G 1 ). In step S 212 , the example method queries whether the receiving device is the host H 2 . If the response is negative, then in step S 222 the example method recites generating a PickedMulticastAddress (G 1 ) with a hop count of one on behalf of H 1 and transmitting the same to host H 2 , thereby notifying host H 2 of a possible conflict with group G 1 address.

If the response to the query of step S 212 is affirmative then the receiving device is also host H 2 . In that case, the example method further queries whether host H 1 has priority over host H 2 in step S 214 . If the response to the query of step S 214 is affirmative, then the example method proceeds to step S 216 in which the host H 2 picks an alternate multicast address G 2 that is distinct from G 1 for its multicast group. In step S 218 , host H 2 initiates the procedure for sending PickedMulticastAddress (G 2 ) to its multicast group. If the response to the query of step S 214 is negative, then host H 2 sends or broadcasts a RejectMulticastAddressPacket to H 1 by including the host H 2 's address, thereby ensuring that host H 1 will pick a distinct multicast address for its group.

Those of skill in the art will readily appreciate that although various aspects and features of the presently claimed invention have been described with reference to a multicast address, the principles of the presently claimed invention are equally well-suited to other types of wireless addresses. For example, the systems and methods described herein can be applied to any node network having unique identifiers and a special node such as a host that collectively define a multicast group. By way of non-limiting example, aspects and features of the presently claimed invention can be employed in all types of wireless networks, including those supported by Internet Protocol (IP) addressing and the IEEE 802.11 series of networks, such as for example wireless personal area networks (WPAN), wireless local area networks (WLAN) including WiFi and Fixed Wireless Data networks, wireless metropolitan area networks (WiMAX) as well as both Global System for Mobile Communication (GSM) and Personal Communications Service (PCS) networks. Those of skill in the art will recognize that the various inventive aspects and features described herein can be readily applied to at least the aforementioned types of communications protocols and networks.

Unless specifically stated otherwise, as apparent from the preceding discussion, it is appreciated that throughout this specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “selecting,” “forming,” “enabling,” “inhibiting,” “locating,” “terminating,” “identifying,” “initiating,” “detecting,” “obtaining,” “hosting,” “maintaining,” “representing,” “estimating,” “reducing,” “associating,” “receiving,” “transmitting,” “determining” and/or the like refer to the actions and/or processes that may be performed by a computing platform, such as a computer or a similar electronic computing device, that manipulates and/or transforms data represented as physical electronic and/or magnetic quantities and/or other physical quantities within the computing platform's processors, memories, registers, and/or other information storage, transmission, reception and/or display devices. Such actions and/or processes may be executed by a computing platform under the control of machine-readable instructions stored in a storage medium, for example. Such machine-readable instructions may comprise, for example, software or firmware stored in a storage medium included as part of a computing platform (e.g., included as part of a processing circuit or external to such a processing circuit). Further, unless specifically stated otherwise, process described herein, with reference to flow diagrams or otherwise, may also be executed and/or controlled, in whole or in part, by such a computing platform including for example the host device 12 and client device 20 described in detail above.

The preceding descriptions are related to selected aspects and preferred examples of the systems and methods of the presently claimed invention. It should be understood by those of skill in the art that these descriptions are exemplary in nature, and that the full scope and import of the presently claimed invention is defined with reference to the following claims.