Abstract:
A method and apparatus for admitting an additional node into a communications network that uses a scheduled communications protocol. Specifically, the node detects the presence of a network, establishes a communication link with a node already present on the network using a unicast messaging protocol, and then communicates pre-admission information to the node on the network. After pre-admission is complete, the new node is admitted to the network.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 60/704,705 filed Aug. 2, 2005, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to a communications network and, more particularly, to a method and apparatus for admitting a node to a network. 
     2. Description of the Related Art 
     A conventional network is comprised of nodes and a router, typically arranged in a hub and spoke formation. A node communicates to another node by transmitting the data to the router, and the router then forwards the data to the destination node. The nodes are unaware of the presence of all the other nodes present on the network, but the router is aware of the presence of all the nodes on the network. The router stores the physical address of all the nodes on the network and facilitates the transmission of data from one node to another. 
     A node is added to a conventional network by connecting the node to a router. Once the router detects the presence of the new node, the router stores the physical address of the node its memory. The nodes on the network communicate with the newly added node in a conventional manner: data addressed to the new node is transmitted to the router, and the router forwards the data to the physical address stored in memory that is associated with the new node. 
     In a multi-base station network, where a plurality of user nodes may wirelessly communicate with a base station, the communications protocol is generally a scheduled protocol. Using a scheduled protocol, the base station organizes the communications with each of the user nodes. When a new node requests a connection to the base station, the scheduled communications may be interrupted to process the request. Such an interruption may impact network throughput. In addition, the process to negotiate the admission of a new node may introduce latency into the communication experienced by the existing nodes of the network. 
     A mesh network differs from a conventional network because there is no central switching point, i.e., a router, to distribute the data within the mesh network. The nodes are aware of the presence of other nodes on the mesh network, and data is transmitted across the mesh network by passing the data through interconnected nodes. Since there is no central switching point to direct traffic on the mesh network, a node must join the mesh network by connecting to nodes that are already a part of the mesh network. 
     The nodes of a mesh network communicate with one another using specific time slots and communications protocols, i.e., the communications within the network are scheduled. A new node that is to be admitted to the network is unsynchronized with the network and must repeatedly request admission until a node that is currently part of the network recognizes the admission request. Consequently, a new node may wait an inordinate amount of time before being admitted to the network. Furthermore, the existing nodes of the network must interrupt their scheduled communications to process the admission request of a new node. Such interruption can impact the throughput of the network. 
     Therefore, there is a need in the art for an improved method and apparatus for admitting a node to a communications network. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and apparatus for admitting an additional node into a communications network that uses a scheduled communications protocol. Specifically, the node detects the presence of a network, establishes a communication link with a node already present on the network using a unicast messaging protocol, and then communicates pre-admission information to the node on the network. After pre-admission is complete, the new node is admitted to the network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a graphical view of a communications network that uses a scheduled communication protocol; 
         FIG. 2  is a block diagram of a node; 
         FIG. 3  is a block diagram of a gateway; 
         FIG. 4  is a flowchart detailing a method of implementing the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a graphical depiction of one embodiment of a communications network  100  comprising a gateway  102  connected to nodes  104 . In the depicted exemplary embodiment, the network is a mesh network; however, those skilled in the art will understand that the invention described herein benefits and may be used with any communications network that uses a scheduled communications protocol. 
     The nodes  104  are interconnected with each other such that multiple paths exist between each node  104  and the gateway  102 . Each node  104  may operate in one of three modes: point-to-point, multi-casting and broadcasting. In a point-to-point mode, a node addresses one specific other node for a communication (i.e., a packet or sequence of packets are addressed to another node). In multi-casting mode, a node may transmit a communication to a specific plurality of other nodes. In a broadcast mode, a node transmits a communication without identifying a specific recipient node for the message. Communications are executed using packets of data that are transmitted within specific timeslots, i.e., a scheduled protocol. One such mesh network is described in U.S. patent application Ser. No. 10/122,883, filed Apr. 15, 2002 and U.S. patent application Ser. No. 10/122,886, filed Apr. 15, 2002, both of which are incorporated herein by reference. 
     In the depicted example, a new node  106  is attempting to join the mesh network  100 . The new node  106  can communicate with Node  104   4  over data path  108   1 , with Node  104   5  over data path  108   2  and with Node  104   6  over data path  108   3 . 
     A node  106  (sometimes referred to as a “child” node) that seeks admission to a mesh network  100  does so by requesting admission to the network  100  using a “unicast message” that is carried by a potentially shared channel. The existing network nodes  104  (sometimes referred to as “parent” nodes) transmit information within a specific time slot once per frame. This information provides node identification information, and other node/network parameters. These messages form a “network advertisement” that provides the child node with information necessary to perform pre-admission processing as described below. More specifically, the child node  106  wishing to join the network listens for the unicast advertisement message(s) from the existing nodes of the network. The messages provide the neighbor node information as well as identifies the time for the unicast slot that can be shared such that a child node may communicate with the existing network nodes. The child node  106  can then send a pre-admission message in the designated unicast slot and “share” the channel. 
     The nodes  104  present on the mesh network  100  listen for a request to join the mesh network  100  within the designated slot for unicast messages. When a node  104   4 ,  104   5 ,  104   6  present on the mesh network  100  detects such a request from a node  106  wishing to join the mesh network  100 , the node  104   4 ,  104   5 ,  104   6  on the mesh network  100  sends a specific reply message that is addressed to the node  106  seeking to join the mesh network  100 . Since the nodes  106  and  104  have exchanged node identifier, these nodes can now “unicast” to one another using the designated slot. These pre-admission communications between parent and child nodes do not interrupt the ongoing communication support of the network that is performed by the parent nodes  104 . 
     The messages initially contain the network identifier, the node identifier and other node parameters to the node  104   4 ,  104   5 ,  104   6  on the mesh network  100 . The node  106  then unicasts a pre-admission message to a node  104   4 ,  104   5 ,  104   6 . The node  104   4 ,  104   5 ,  104   6  on the mesh network forwards the pre-admission message to the gateway  102 . The gateway  102  then authenticates the node  106  and the node  106  becomes a part of the network  100 . A detailed description of the admission process is presented below with respect to  FIG. 4 . 
     In other embodiments of the invention, i.e., a multi-base station network, the child node communicates with a base station using a pre-admission message. The decision to admit the child node to the network is performed by the base station without communicating to a gateway or any other network node. 
     The pre-admission communications occur in such a manner that the user communications performed by the parent node is not impacted by the admission negotiation. These pre-admission communications may occur in designated slots (as discussed above) or, alternatively, may occur using a separate low-bandwidth slotted protocol that is not related to the parent node user data network protocol. The pre-admission protocol may be separate and distinct from the user data protocol. As such, once the pre-admission negotiation is complete, the child node is “handed over” to the standard communication protocol to become a member of the network. 
       FIG. 2  is a block diagram of a node  104  or node  106 . The node  104  comprises a CPU  202 , support circuits  206 , memory  204  and a network interface  208 . The CPU  202  may comprise one or more readily available microprocessors or microcontrollers. The support circuits  206  are well known circuits that are used to support the operation of the CPU and may comprise one or more of cache, power supplies, input/output circuits, network interface cards, clock circuits, and the like. Memory  204  may comprise random access memory, read only memory, removable disk memory, flash memory, optical memory or various combinations of these types of memory. The memory  204  is sometimes referred to as main memory and may, in part, be used as cache memory or buffer memory. The memory  204  stores various forms of software and files, such as, an operating system (OS)  210  and admission processing software  212 . The network interface  208  may be wired or wireless. 
       FIG. 3  is a block diagram of a gateway  102 . The gateway  102  comprises a CPU  302 , support circuits  306 , memory  304  and a network interface  308 . The CPU  302  may comprise one or more readily available microprocessors or microcontrollers. The support circuits  306  are well known circuits that are used to support the operation of the CPU  302  and may comprise one or more of cache, power supplies, input/output circuits, network interface cards, clock circuits, and the like. Memory  304  may comprise random access memory, read only memory, removable disk memory, flash memory, optical memory or various combinations of these types of memory. The memory  304  is sometimes referred to as main memory and may, in part, be used as cache memory or buffer memory. The memory  304  stores various forms of software and files, such as, an operating system (OS)  310  and admission processing software  312 . The network interface  308  connects the gateway to the mesh network  100  as well as to a data backbone (not shown). The network interface  308  may be wired or wireless. 
       FIG. 4  depicts a flow chart of methods  400  and  401  of one embodiment of the operation of the present invention. To best understand the operation of the invention, the reader in encourage to simultaneously view  FIGS. 1 and 4 . Method  400  represents process steps performed by the node  104  executing its admission processing software and method  401  represents the process steps performed by the node  106  executing its admission processing software. 
     The method  400  begins at step  402  where the node  104  broadcasts or multicasts node/network information (a network advertisement message) in a designated slot. Although designated slots are synchronous within a frame used by a given node, they are asynchronously broadcast across the network. Consequently, various nodes will be broadcasting at different times commensurate with the local data frame timing. Thus, a node that receives such a broadcast from a particular frame may wait one frame period and transmit within the slot for that particular node to communicate with the node that sent the original broadcast. The node  106  that desires to enter the network must receive and process the advertisement messages, determine the “best” node to communicate with and then negotiate entry into the network. The communications to support the admission transaction are performed using the designated slots that define a shared unicast channel between the parent and child nodes. 
     At step  404 , the child node  106  receives at least one advertisement message. Generally, the node  106  receives signals from a plurality of neighboring nodes  104 . To determine the “best” node to contact and negotiate network admission, the method  401  computes proximity indicia for the received broadcasts. Generally, the node computes received signal strength information (RSSI) for each of the received broadcast signals. Other criteria may be used for determining link quality including successful transmission rate for packets, bit error rates, and the like. At step  406 , the method  401  selects a node  104  having the “best” quality link to the child node  106 , e.g., the node with the largest RSSI. 
     At step  408 , the method decodes the node/network information that is sent in the broadcast message of the selected node. 
     At step  410 , the node  106  estimates the parameters of a data link to the nodes detected on the network. The parameters of the data link may comprise the received signal strength of the link, the modulation rate of data on the link, the bit error rate of the link, node identification, network identification, or the physical distance over the link. 
     At step  412 , the node  106  transmits a unicast message over the selected data link on a known slot. The message is a unicast message because it is addressed specifically to the selected node, i.e., the message is “tunneled” to the selected node  104 . In one embodiment where the designated slots appears once per frame, the node  106  waits one frame period from the time of reception of the broadcast signal from the selected node  104 , then transmits its unicast message. Consequently, the child and parent nodes begin communicating in a shared unicast channel. 
     At step  414 , the selected node  104  receives the request for admission form the child node on the unicast channel. At step  416 , the selected node  104  transmits pre-admission information via a unicast message to the node  106 . This information is sufficient for the node  106  to receive information from the network. The pre-admission message may contain information regarding ranging, clock synchronization, one-way or two-way authentication, cryptographic information (key exchange), network configuration (e.g., routing information, congestion information, capacity information, and the like) and the like. 
     At step  418 , the message is received and, at step  420 , the node  106  transmits authentication information (passwords and other security information) through a unicast message to the node  104 . The node  104 , at step  422 , forwards the authentication information to the gateway. At step  424 , the node  104  transmits admission information received from the gateway to the node  106 . This information will enable the node  106  to access database information regarding the network and optimize its transmission bandwidth. At step  426 , the node  106  is admitted to the network, i.e., a switch-over or hand-over occurs where the child node is admitted to the network and can operate as a parent node. 
     If the network is a multi-base station network, then the base station (node  104 ) will decide to admit the child node without communicating to a gateway. Thus, a node may perform a pre-admission process in the background without impacting the “normal” network support of user communications provided by a network node, then using a single message, handover a newly admitted node to the network. The new node may be a user node or another base-station node. 
     The child nodes, in any of the embodiments described herein, may operate in another network until the pre-admission process is complete. As such, a child node with respect to one network may be a parent node with respect to another network. Once pre-admission processing is complete, the child node switches to a parent in the new network and disconnects from the other network. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.