Abstract:
A system and method of performing device detection and service discovery in a mobile ad hoc communications network, each network node storing a local application directory. One of the network nodes is selected to be a directory server node that stores a combined application directory. The directory server node sends an inquiry message to a listening node when the listening node enters the coverage area of the directory server node. The listening node sends a notification message to the directory server node that includes the local application directory stored in the listening node. The directory server node compares the received local application directory to the combined application directory and updates the combined application directory accordingly. The directory server node sends an update message to each network node by sending an update portion of the combined application directory. Each network node updates the local application directories accordingly.

Description:
FIELD OF THE INVENTION 
   The disclosed invention is a device detection and service discovery system and method for a mobile ad hoc communications network. The system and method employs a centralized distribution model for sending update messages to the network nodes in a mobile ad hoc communications network, each update message based upon local application directory information that describes the network node. 
   BACKGROUND OF THE INVENTION 
   Short-range wireless systems have a range of less than one hundred meters, but may connect to the Internet to provide communication over longer distances. Short-range wireless systems include, but are not limited to, a wireless personal area network (PAN) and a wireless local area network (LAN). A wireless PAN uses low-cost, low-power wireless devices that have a typical range of ten meters. An example of a wireless PAN technology is the Bluetooth Standard. The Bluetooth Standard operates in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band and provides a peak air-link speed of one Mbps and a power consumption low enough for use in personal, portable electronics such as a personal digital assistance or mobile phone. A description of the Bluetooth communication protocol and device operation principles is in  Bluetooth Special Interest Group, Specification of the Bluetooth Standard , version 1.0B, volumes 1 and 2, December 1999. A wireless LAN is more costly than a wireless PAN, but has a longer range. An example of a wireless LAN technology is the IEEE 802.11 Wireless LAN Standard and the HIPERLAN Standard. The HIPERLAN Standard operates in the 5 GHz Unlicensed-National Information Infrastructure (U-NII) band and provides a peak air-link speed between ten and one hundred Mbps. 
   An ad hoc network is a short-range wireless system comprising an arbitrary collection of wireless devices that are physically close enough to exchange information. An ad hoc network is constructed quickly with wireless devices joining and leaving the network as they enter and leave the proximity of the remaining wireless devices. An ad hoc network also may include one or more access points, that is, stationary wireless devices operating as a stand-alone server or as gateway connections to other networks. 
   In the future, the Bluetooth Standard will likely support the interconnection of multiple piconets to form a multi-hop ad hoc network, or scatternet. In a scatternet, a connecting device forwards traffic between different piconets. The connecting device may serve as a master device in one piconet, but as a slave device or a master device in another piconet. Thus, the connecting devices join the piconets that comprise a scatternet by adapting the timing and hop sequence to the respective piconet and possibly changing the roles that they serve from a master device to a slave device. 
   A Bluetooth device includes, but is not limited to, a mobile telephone, personal or laptop computer, radio-frequency identification tag, and personal electronic device such as a personal digital assistant (PDA), pager, or portable-computing device. Each Bluetooth device includes application and operating system programs designed to find other Bluetooth devices as they enter and leave the communication range of the network. The requesting Bluetooth device in a client role and the responding Bluetooth device in a server role establish a link between the two devices. The requesting and responding Bluetooth device use the link and a service discovery protocol to discover the services offered by the other Bluetooth device and how to connect to those services. 
   Prior art systems follow similar patterns of behavior for service discovery protocols. A service description, created using a description language and an appropriate vocabulary, is advertised or made available for query matching. Some prior art systems advertise the service description by pushing the description to a directory and requiring the advertisers to discover the directory. Other prior art systems advertise the service description by making the descriptions available for peer-to-peer discovery. A client device that needs to discover the service description composes a query using a query language and a matching vocabulary and uses either a query protocol or a decentralized query-processing server to deliver the query. 
   Service discovery protocols in the prior art systems require sending and replying to inquiry messages. If no other device is present, the inquiry messages are sent in vain. To avoid excessive power consumption, the prior art systems typically require a human user to manually initiate device detection when another device of interest is present. For example, a human user manually initiates device detection when connecting a cellular telephone to a laptop computer to handle data communications or when connecting a wireless headset to a laptop computer to deliver digital audio. These prior art systems rely upon three assumptions. First, an application can be freely started because the presence of its services is guaranteed. Second, an application performs service discovery when it first needs a service. Third, the composition of the network does not change during the lifetime of the application. 
   Thus, there is a need for a device detection and service discovery protocol that will avoid excessive power consumption and allow an application resident in one device to automatically find a counterpart application or some other resource resident in any of the remaining devices within the ad hoc communications network. The protocol does not require a human user to manually initiate device detection to find the counterpart application or other resource. Furthermore, the protocol will accommodate a network environment in which the presence of a particular service is not guaranteed and in which the composition of the network is dynamic because devices frequently enter and leave the network. The disclosed invention addresses this need. 
   SUMMARY OF THE INVENTION 
   A system and method of performing device detection and service discovery in a mobile ad hoc communications network including at least one network node, each network node storing a local application directory. The system and method selects a directory server node from said at least one network node, the directory server node having a coverage area and storing a combined application directory. The directory server node sends an inquiry message to a listening node when the listening node enters the coverage area of the directory server node. The listening node sends a notification message to the directory server node, the notification message comprising the local application directory stored in the listening node. The directory server node stores an update to the combined application directory based on a comparison of the local application directory included with the notification message and the combined application directory. The directory server node sends an update message to each network node communicating with the mobile ad hoc communications network, the update message comprising an update portion of the combined application directory for updating the local application directories of each of the nodes within the mobile ad hoc communications network. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying figures best illustrate the details of the device detection and service discovery system and method for a mobile ad hoc communications network, both as to its structure and operation. Like reference numbers and designations in these figures refer to like elements. 
       FIG. 1  is a network diagram that illustrates the interaction of the devices that comprise a mobile ad hoc communications network. 
       FIG. 2A  is a block diagram that illustrates the hardware and software components comprising server  110  shown in FIG.  1 . 
       FIG. 2B  is a block diagram that illustrates the hardware and software components comprising terminal  120  shown in FIG.  1 . 
       FIG. 3A  is a flow diagram of an embodiment of server  110  performing device detection and service discovery for a mobile ad hoc communications network. 
       FIG. 3B  is a flow diagram of an embodiment of terminal  120  performing device detection and service discovery for a mobile ad hoc communications network. 
       FIG. 4A  is an exemplary block diagram of the data flow before a terminal enters a mobile ad hoc communications network. 
       FIG. 4B  shows the exemplary block diagram of  FIG. 4A  after the terminal enters the mobile ad hoc communications network. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a network diagram that illustrates the interaction of the network nodes that comprise a mobile ad hoc communications network. In one embodiment, the mobile ad hoc communications network is a Bluetooth piconet that includes one master device and up to seven active slave devices. As shown in  FIG. 1 , piconet  100  includes server  110  and five instances of terminal  120 . Server  110  maintains the network clock and is the communication manager for each instance of terminal  120 . Server  110  typically initiates an exchange of data with an instance of terminal  120 . Two instances of terminal  120  typically communicate through the server  110  however, if two instances of terminal  120  communicate directly, one instance will assume the role of server, or master, and the other instance will assume the role of client, or slave. 
   Each device in the mobile ad hoc communications network will either assume the role of a terminal device or a server device. A terminal device is a consumer of services that a single user operates. A terminal device includes devices such as a mobile phone or PDA. A server is typically a stationary device and only produces services. A server device creates a hotspot around them for using their services. “Hotspot” refers to the radio coverage area provided by the server device for detecting devices and discovering services offered by the applications hosted in the server. If the server device is not stationary, one of the terminal devices in the network will assume the role of application directory server and perform device detection and service discovery functions for the remaining terminal devices in the network. The disclosed invention introduces two roles among such terminal devices, application directory servers and terminals, where application directory servers serve terminals in device detection and service discovery. If stationary servers with hotspots exist, servers typically act as application directory servers however, device detection and service discovery is possible without such a stationary server because one of the terminals will assume the application directory server duties. 
   The disclosed invention categorizes an application as a server-based application, terminal-to-terminal application, foreground application, background application, or generic application component. A server-based application requires a server to produce a service. A terminal-to-terminal application requires at least two terminal devices to implement a service without the presence of a server device. A foreground application is an application resident in a terminal device that a user accesses via the user interface of the terminal device. A background application is an application resident in a terminal device that may start without any intervention by the user A generic application component can be used either as a standalone application or as a component of another application. 
   An application may be further categorized as either active, passive, new, or rejected. An active application is a foreground or background application that is resident in (i.e., stored in memory) the terminal. A passive application is resident in the terminal, but has not yet been started. In another embodiment, the passive application is started, but is not actively looking for other instances of the same application. A new application is not yet resident in the terminal, but might be in the future. A rejected application is not resident in the terminal and has been marked by the user as an application that should never be resident in the terminal. In another embodiment, the rejected application was once resident in the terminal, but was subsequently deleted and marked as rejected. In yet another embodiment, the rejected application never resided in the terminal, but is of a type of application that the user has marked as rejected. 
   Service discovery in a mobile ad hoc communications network differentiates between a resident application and an unloaded application. A resident application is stored in the terminal memory and loaded as either a foreground application or a background application. An unloaded application is not yet stored or loaded in the terminal, but has been accepted by the user. Typically, when an application was previously used, but has been overwritten to reclaim space, the application is considered unloaded. Thus, starting an unloaded application may require first downloading the application. 
   Service discovery from the perspective of the terminal device requires categorizing the status of an application as either an active resident application, active unloaded application, passive resident application, passive unloaded application, rejected application, or new application. An active resident application is loaded in the terminal and looking for peers, servers, or clients. An active unloaded application is not loaded in the terminal, but is still looking for such counterpart applications that could be automatically downloaded if found interesting. A passive resident application is loaded in the terminal, but is not looking for counterpart applications. A passive unloaded application is not loaded in the terminal, but was once accepted by the user. A rejected application is an application that a user has requested to exclude from the terminal device. A new application is not loaded in the terminal device, but the user might have seen an application in an earlier server for instance. 
     FIG. 2A  is a block diagram that illustrates the hardware and software components comprising server  110  shown in FIG.  1 . Server  110  is a general-purpose wireless device. Bus  200  is a communication medium that connects keypad  201 , display  202 , central processing unit (CPU)  203 , and radio frequency (RF) adapter  204  to memory  210 . RF adapter  204  connects via a wireless link to terminal  120  and is the mechanism that facilitates network traffic between server  110  and terminal  120 . 
   CPU  203  performs the methods of the disclosed invention by executing the sequences of operational instructions that comprise each computer program resident in, or operative on, memory  210 . Memory  210  includes operating system software  211 , application programs  212 , and middleware software  220 . Operating system software  211  controls keypad  201 , display  202 , RF adapter  204 , and the management of memory  210 . Application programs  212  control the interactions between a user and server  110 . Middleware software  220  includes an application program interface (API)  221  that help an application program running on server  110  find and communicate with a counterpart application running on terminal  120 . To quickly locate each application, middleware software  220  also includes application directory  230  to track the role assumed by each application that is resides in each device in piconet  100 . 
     FIG. 2B  is a block diagram that illustrates the hardware and software components comprising terminal  120  shown in FIG.  1 . Terminal  120  is a general-purpose wireless device. Bus  250  is a communication medium that connects keypad  251 , display  252 , CPU  253 , and RF adapter  254  to memory  260 . RF adapter  254  connects via a wireless link to server  110  or another terminal  120  and is the mechanism that facilitates network traffic between server- 110  and terminal  120 . 
   CPU  253  performs the methods of the disclosed invention by executing the sequences of operational instructions that comprise each computer program resident in, or operative on, memory  260 . Memory  260  includes operating system software  261 , application programs  262 , and middleware software  270 . Operating system software  261  controls keypad  251 , display  252 , RF adapter  254 , and the management of memory  260 . Application programs  262  control the interactions between a user and terminal  120 . Middleware software  270  includes an API  271  that help an application program running on terminal  120  find and communicate with a counterpart application running on server  110  or another terminal  120 . To quickly locate each application, middleware software  270  also includes application directory  280  to track the role assumed by each application that is resident on each device in piconet  100 . 
   In one embodiment, the configuration of memory  210  and memory  260  is identical. In another embodiment, the configuration of memory  210  and memory  260  only includes the software necessary to perform the essential tasks of server  110  and terminal  120 , respectively. For example, if terminal  120  needs to receive a general inquiry access code, but does not need to send a general inquiry access code message, only the software that sends this message will reside in memory  260 . 
   An application executing on a terminal is constantly searching for a counterpart application, that is, another instance of the same application that can communicate with the application. Each instance of an application assumes a particular role. Communication between an application and a counterpart application is only meaningful if the roles are complementary. For example, an application that assumes the role, of “client” can communication with a counterpart application that assumes the role of “server”. Middleware software is a software layer with an API that negotiates the communication, between two applications to help an application find a counterpart application with the correct role. Thus, an application installed in a terminal and activated, will query the API for a continuous stream of new counterpart applications that are of interest. 
   A new application is installed by “installer” applications that use middleware for finding counterparts and installing the new application into the local storage of a terminal. The actual finding and selection of new applications takes place in the application level. Initially, the installer application will be a dedicated “browser-supplier” (i.e., client-server) application that accesses counterpart applications in servers, browses their available application databases, allows a user to pick the applications to install, and downloads and installs the new applications. Later, the corresponding functionality may be added to a wireless access protocol (WAP) and hypertext markup language (HTML) browsers. 
   Service discovery is viewed as a three step process. First, new potential applications are found and will be considered for installation. Second, active installed applications begin to search for counterpart application. Third, active installed applications begin searching for common resources such as printers (i.e., resource discovery). The disclosed invention relies upon the applications to perform resource discovery. Typically, a terminal application communicates with its counterpart application and use local (i.e., server) resources. If an application uses a private resource, the associated service discovery is implemented by the application in a standard (e.g. Bluetooth or Bluetooth/Java) way not supported by the terminal middleware software. 
     FIG. 3A  is a flow diagram of an embodiment of the disclosed invention, wherein one network node assumes a role of a directory server, such as, server  110  performing device detection and service discovery for a mobile ad hoc communications network. The process begins when server  110  sends a general inquiry access code message to terminal  120  (step  300 ). Terminal  120  receives the message and sends an acknowledgment response message to server  110  (step  302 ). Server  110  accesses middleware software  220  to request a socket connection with terminal  120  (step  304 ). In response to establishing the socket connection, server  110  receives a message from terminal  120  that includes a local application directory listing all of the applications that are locally resident on terminal  110  (step  306 ). Server  110  compares the list of applications resident on terminal  120  to a combined application directory resident on server  110 . Server  110  updates the combined application directory by adding to the combined application directory each entry in the local application directory that does not appear in the combined application directory (step  308 ). Server  110  sends a portion of the updated combined application directory to each terminal  120  in piconet  100  (step  310 ). The portion may vary for each terminal  120  and includes each entry in the combined application directory that is a counterpart application to an application resident in terminal  120 . In another embodiment, server  110  sends the entire combined application directory to each terminal  120  in piconet  100  and relies upon terminal  120  to retain the pertinent entries. Instances of middleware software in terminal  120  and server  110  begin to schedule the newly found counterpart application pairs for execution (step  312 ). In one embodiment, the scheduled applications make use of any other Bluetooth profile and protocol. In another embodiment, an application that is an installer application may suggest to the user other applications that the user should download. Once server  110  downloads and starts a new application, counterpart matching repeats and the new application becomes a part of the middleware scheduling. 
     FIG. 3B  is a flow diagram of an embodiment of the disclosed invention, wherein one network node assumes a role of a directory server, such as, terminal  120  performing device detection and service discovery for a mobile ad hoc communications network. The process begins when terminal  120  receives a general inquiry access code message from server  110  (step  320 ). Terminal  120  generates and sends an acknowledgment response message to server  110  (step  322 ). Terminal  120  sends a message to server  110  that includes a local application directory that includes all of the applications that are locally resident on terminal  110  (step  324 ). Server  110  compares the list of applications resident on terminal  120  to a combined application directory resident on server  110 . Server  110  updates the combined application directory by adding to the combined application directory each entry in the local application directory that does not appear in the combined application directory. Terminal  120  receives from server  110  a portion of the updated combined application directory (step  326 ). Server  110  customizes the portion for terminal  120  to include each entry in the combined application directory that is a counterpart application to an application resident in terminal  120 . In another embodiment, server  110  sends the entire combined application directory to terminal  120  and relies on terminal  120  to retain the pertinent entries. Instances of middleware software in terminal  120  and server  110  begin scheduling these newly found counterpart application pairs for execution (step  328 ). 
     FIGS. 4A and 4B  are exemplary block diagrams showing the content of the application directory before terminal X and terminal Y enter a mobile ad hoc communications network served by server S.  FIG. 4A  shows the configuration of application directory  404 , application directory  415 , and application directory  425  before terminal X and terminal Y enter a communication network managed by server S, a master device. Application C  401  resides in server S memory  400  and accesses middleware software  403  via API  402 . Middleware software  403  registers application C  401  with application directory  404  by adding a table entry to indicate that application C resides in the local device (i.e., server S) and assumes the role of server. Application A  411  and application B  412  reside in terminal X memory  410  and access middleware software  414  via API  413 . Middleware software  414  registers application A  411  and application B  412  with application directory  415  by adding a table entry to indicate that application A resides in the local device (i.e., terminal X) and assumes the role of client and that application B resides in the local device (i.e., terminal X) and assumes the role of peer. Application B  421  and application C  422  reside in terminal Y memory  420  and access middleware software  424  via API  423 . Middleware software  424  registers application B  421  and application C  422  with application directory  425  by adding a table entry to indicate that application B resides in the local device (i.e., terminal Y) and assumes the role of peer and that application C resides in the local device (i.e., terminal Y) and assumes the role of client. 
     FIG. 4B  shows the configuration of application directory  404 , application directory  415 , and application directory  425  after terminal X and terminal Y enter the communication network managed by server S, a master device. Server S assumes the role of an application directory server (ADS) and mediates the registration of the applications residing in each device in piconet  100 . Server S adds a table entry to application directory  404  for each application residing in a device on piconet  100 . Thus, server S adds an entry for application A residing in terminal X in a client role, application B residing in terminal X in a peer role, application B residing in terminal Y in a peer role, and application C residing in terminal Y in a client role. Server S also updates application directory  415  in terminal X and application directory  425  in terminal Y with application registrations that may be interesting to those terminal devices. As shown in  FIG. 4B , terminal X and terminal Y both host application B in a peer role. Since, a peer-to-peer communication session between application B on terminal X and application B on terminal Y is likely, server S adds an entry to application directory  415  for application B residing in terminal Y in a peer role and an entry to application directory  425  for application B residing in terminal X in a peer role. Also, since a client-server communication session between application C on terminal Y and application C on server S is likely, server S adds an entry to application directory  425  for application C residing in server S in a server role. Finally, there is no counterpart in piconet  100  for application A on terminal X. 
   As shown in  FIGS. 4A and 4B , the disclosed data items for each entry in the middleware software application directory server include a device identifier (e.g., “local”, an address, or other unique identifier), an application identifier (e.g., application name or other unique identifier), and a role for the application (e.g., “client”, “server”, “peer”, etc.). In another embodiment, the data items can be expanded to include fields for the local applications (i.e., device=“local”) and fields for remote applications in other terminals or servers. The fields for the local applications include:
         Name—An identifier for the application (e.g., supplier name and data to compare different versions and hardware variants);   My_role—The role that the application takes in the local device;   Partner_role—The role that the application assumes from interesting counterparts (e.g., peer, client, and server are the most common roles);   Residency—Either RESIDENT (installed and currently in memory), UNLOADED (installed once, not currently in memory, but can be re-downloaded automatically), REJECTED (indicates to the new application installer that it should ignore the application), and NEW (the application is not installed or rejected);   State—Either RUNNING (has communications, is now working with its remote counterparts, but there may be either only one, or more, applications that can use the communications at a time), WAITING (in execution but does not have any communications), STARTABLE (active, if a matching peer with the right partner_role is found, the middleware software starts this application, downloading the software first if needed), COMPLETE (all counterpart applications are aware), and PASSIVE (user must do something to start application);   Type—Eitehr FOREGOUND (when the application terminates, the state will be PASSIVE), and BACKGROUND (if the application terminates, the state will be STARTABLE);   Unload—Either AUTOMATIC (middleware may remove code when the application has terminated), or UNINSTALL (user must confirm removals);   Icon—Creates a visual image of the application for the user; and   Timeout—Sets a time limit that the middleware software uses to detect, for example, when the application is in an unproductive software loop.       

   The fields for the remote applications include:
         Device—An address for establishing communications with the terminal or server storing the application instance;   Name—An identifier for the application; and   My_role—The role that the application takes in the remote device.       

   The client-server roles of the applications are independent of the roles of the devices as a terminal device and an application directory server. Typically, the device acting as an application directory server hosts applications acting in a server role and the terminal devices act in the client role for the same application. In another embodiment, two terminal devices each send a general inquiry access code message and listen for a reply. The terminal device that first receives a response first will assume the server role and proceed according to the procedure in FIG.  3 A. Another terminal device that receives the inquiry message will assume the terminal role, and proceed according to FIG.  3 B. Thus the, disclosed invention supports terminal-to-terminal scenarios (e.g., one of identical handheld devices automatically becoming an ADS) and does not require predetermined application directory servers. 
   Although the disclosed embodiments describe a fully functioning device detection and service discovery system and method for a mobile ad hoc communications network, the reader should understand that other equivalent embodiments exist. Since numerous modifications and variations will occur to those who review this disclosure, the device detection and service discovery system and method for a mobile ad hoc communications network is not limited to the exact construction and operation illustrated and disclosed. Accordingly, this disclosure intends all suitable modifications and equivalents to fall within the scope of the claims.