Abstract:
A method and apparatus for internetworked communication between first and second wireless networks containing first and second pluralities of wireless nodes, respectively, is disclosed herein. In a preferred implementation a first dual-power node participates in both a first wireless network and an overlay network. The dual-power node is configured to transmit and receive in both a high-power mode and a low-power mode. The dual-power node operates in an overlay network and facilitates data transmission between low-power nodes and high-power nodes by toggling between these two power modes. In a preferred implementation, a third wireless network containing a third plurality of wireless nodes is utilized. The overlay network can accommodate a plurality of high-power or dual-power nodes.

Description:
REFERENCE TO RELATED PATENT APPLICATIONS  
         [0001]    The entire disclosure of the copending U.S. Patent Application entitled DISTRIBUTED MANAGEMENT OF AN EXTENDED NETWORK CONTAINING SHORT-RANGE WIRELESS LINKS, filed on even date herewith, the specification of which is hereby incorporated by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention generally pertains to communication systems, and more particularly to an inter-networked communication system containing a dual-powered node.  
         BACKGROUND OF THE INVENTION  
         [0003]    Traditionally, electronic devices used in an office network relied on alternating current “AC” power as their power source. A typical office configuration consisted of, at a minimum, several computers, a printer, and a central data storage device. The traditional office also typically employed hardwired connections from one device to another. Conveying information from one device to another was accomplished by using a wired backbone network. Thus, a user desiring to route data from a computer to a printer sent the necessary data over a cable from his or her computer to a local printer.  
           [0004]    More recently, office configurations incorporate both AC powered devices and battery operated, or wireless, devices such as personal digital assistants (“PDA”), pagers, laptop computers, and the like. While these devices run on battery power and thus do not require a wired connection for power, unless they are configured with a transmit antenna and an amplifier and are located in close proximity to a device capable of receiving data transmission, these wireless devices must transfer data to external devices via traditional wired backbones. Technologically speaking, it is fairly straightforward to couple a wireless device to a transmit antenna and an amplifier for the purpose of routing data from the wireless device to a standard AC device. One difficulty with this configuration is that wireless devices, unlike AC devices, have a limited power supply and, therefore, must minimize power consumption. System designers thus generally must make a trade-off between extended transmission range and power conservation.  
           [0005]    Transmission range of a wireless device without an amplifier is typically limited to somewhere on the order of ten meters. If the user is operating the wireless system exclusively in his or her office, this range limitation is typically not an issue. If, however, the user seeks to operate the wireless device outside of his or her office, AC devices intended to receive the data within the office will be out of range. Even if there are other AC devices within range of the wireless unit at the moment that the user wishes to transmit data, these intermediary devices will be unhelpful unless some wired backbone is in place to transfer the data to the desired AC device. That is, the data will remain stored at the AC device receiving the data. For example, assume a user is in conference room and is using a PDA out of range of the AC devices in his individual office. If the user wishes to print a color copy of a chart stored on the PDA using the color copier located in his office, he will be required to leave the conference room and move within the range of his color printer. This undesirable limitation has been overcome by employing a wired network connecting all of the AC devices in a particular office. Once the devices are physically connected, it becomes possible to route data from the wireless device to anywhere in the office. Unfortunately, such hardwired networks are inflexible and can be difficult to install and maintain.  
         SUMMARY OF THE INVENTION  
         [0006]    Briefly, therefore, this invention provides for a method and apparatus for internetworked communication. The system of the invention includes at least a first wireless network containing a first plurality of wireless nodes and an overlay network containing a second plurality or wireless nodes. In a preferred embodiment, a first dual-power node participates in both the first wireless network and in the overlay network and operates in a time-division multiplexed manner. Specifically, the first dual-power node communicates with the first plurality of wireless nodes at a first power level during certain time slots, and with at least one of the second plurality of wireless nodes at a second power level during other time slots. The inventive system may also include a third wireless network containing a third plurality of wireless nodes, at least one of which is also included in the second plurality of wireless nodes.  
           [0007]    In a preferred embodiment, the dual-power node contains a low-power transceiver, a high-power transceiver, and a controller for facilitating toggling between operation in high-power and low-power nodes. The overlay network may also contain a second dual-power node capable of communicating with the first dual-power node at high power and with the third plurality of wireless nodes at a lower power.  
           [0008]    The overlay network is preferably initialized pursuant to a protocol in which one high-power device becomes operative as a master node and the remaining high-power devices act as slave nodes. Pursuant to this protocol, the master node transmits a notification signal identifying itself as a high-power device and indicating the identity and connectivity of its overlay network. This notification message signals the other high-power devices that the overlay network contains a master node and that additional nodes seeking to join the network should act as slave nodes. Accordingly, when a high-power node or a dual-power node initially powers-up, it monitors the network to determine whether any of the high-power or dual-power devices are presently acting as master nodes. If a master node does not currently exist, the high-power or dual-power device assumes the role of master node. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    In the accompanying drawings:  
         [0010]    [0010]FIG. 1 illustrates a first and second pluralities of wireless nodes, respectively, configured within a first wireless network and within an overlay network in accordance with the present invention.  
         [0011]    [0011]FIG. 2 illustrates first, second, and third pluralities of wireless nodes respectively configured in a first wireless network, an overlay network, and in a third wireless network.  
         [0012]    [0012]FIG. 3 is a block diagram of a dual-power node configured in accordance with the present invention.  
         [0013]    [0013]FIG. 4 is a flow chart representative of the process of transmitting broadcasts from master nodes and advertisements from slave nodes.  
         [0014]    [0014]FIG. 5 shows the timing sequence for establishing a network when the participating nodes are operating at the same power level.  
         [0015]    [0015]FIG. 6 depicts the timing sequence for establishing a network between nodes that are operating at different power levels.  
         [0016]    [0016]FIG. 7 is a flow chart representative of a process for relaying data from a low-power node to a node in an overlay network.  
         [0017]    [0017]FIG. 8 illustrates the inclusion of a relay node within an overlay network in accordance with the present invention.  
         [0018]    [0018]FIG. 9 illustrates a system including first and second wireless networks linked by an overlay network containing a relay node. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    The present invention is more fully described with reference to FIGS.  1 - 9 . An exemplary implementation of the invention is discussed and illustrated with reference to its implementation using wireless networks predicated on the proposed “Bluetooth” wireless communications protocol. This protocol contemplates the grouping of physically proximate wireless nodes, and is described in  Specification of the Bluetooth System , v0.8, Jan. 22, 1999 (and in subsequent revisions thereof). It should be understood that this invention is not limited to such a wireless protocol, and could be similarly implemented using other types of wireless networks.  
         [0020]    [0020]FIG. 1 illustrates a communication system  10  comprised of first and second pluralities of wireless nodes configured within a first wireless network  12  and within an overlay network  14 , respectively. The first wireless network  12  is comprised of a first dual-power node  20  and a first plurality of wireless nodes  22 . While FIG. 1 only depicts one wireless node in the first wireless network  12 , the present invention could accommodate a plurality of wireless nodes in the first wireless network  12 . The overlay network  14  is comprised of the first dual-power node  20  and a second plurality of wireless node  24 .  
         [0021]    The first plurality of wireless nodes  22  operate as low-power nodes, while the second plurality of wireless nodes  24  operate as high-power nodes. For purposes of example, a low-power node is typically limited to a maximum power level of 2.5 mW or to a maximum transmission range of 10 meters. High-power nodes are capable of exceeding these power levels and transmission ranges. The dual-power node  20  is capable of operating in both high-power and in low-power modes, and is more precisely depicted in FIG. 3.  
         [0022]    Referring again to FIG. 1, a dual-power node  20  of the overlay network  14  receives data from low-power devices located closely proximate thereto. This data is then forwarded to other high-power nodes (e.g., to node  24 ) or to other dual-power devices (not shown) located within the overlay network  14 . In this way low-power electronic devices within an office environment are able to transfer data to devices well beyond their transmission ranges.  
         [0023]    In a preferred embodiment, the dual-power node  20  and high-power node  24  are respectively coupled to power amplifiers  32  and  34 . Coupling power amplifiers  32  and  34  to the dual-power node  20  and the high-power node  24  can increase their transmission capabilities by at least an order of magnitude. In a preferred implementation dual-power node  20  and high-power node  24  operate using AC power, which removes the power consumption of amplifiers  32  and  34  as a relevant design concern.  
         [0024]    [0024]FIG. 2 illustratively represents an embodiment in which a third wireless network  16  has been added to the system of FIG. 1. The third wireless network  16  contains a third plurality of low-power wireless nodes  26  and  28 . In addition, a second dual-power node  30  has been added to the overlay network  14 . This second dual-power node  30  operates in a similar fashion as the first dual-power node  20 , communicating with both the low-power nodes in the third wireless network  16  and the high-power nodes in the overlay network  14 .  
         [0025]    As previously mentioned, FIG. 3 is a detailed depiction of the interior of the dual-power node  20 . In a preferred implementation the dual-power node  20  consists of a low-power transceiver  100 , a high-power transceiver  110 , a controller  120 , and an omni-directional antenna  130 . Alternate implementations may contemplate use of a common transceiver rather than separate high-power and low-power transceivers, and antenna configurations other than omnidirectional. The controller  120  allows the dual power node  20  to toggle between operating as a high-power node and a low-power node.  
         [0026]    In a preferred implementation, the nodes  20  and  24  of the overlay network  14  operate in a hierarchical fashion such that one node acts as a master node while all other nodes behave as slave nodes. FIG. 4 contains a flow chart representation of the procedures followed in connection with establishing a master node within the overlay network  14 . As is indicated by FIG. 4, a first step in establishing a master/slave configuration occurs upon initial power-up of the device  200 . At that point, the device “listens” for a notification message  210  which would indicate that an overlay network  14  has already been established. If a notification message is not detected, the device assumes the role of master device  220  and begins periodically transmitting notification messages  230 . In addition to identifying the sender as a high power device, these notification messages are transmitted at maximum power and contain the identity and connectivity of the network as disclosed in the above-referenced copending U.S. Patent Application. If, on the other hand, an already established master device is heard upon initial power-up, the device assumes the role of a slave  240 . The slave node transmits a network type-specific response indicating that it wishes to join the network  250 . The transmitted message may also contain information identifying the node and its connectivity.  
         [0027]    The present invention contemplates the establishment of several different types networks comprised of various combinations of high-power and low-power nodes: (1) networks between high-power or dual-power nodes; (2) networks between low power nodes; and, (3) networks between dual-power nodes and low-power nodes. In a preferred implementation, the timing of signal transmission and reception is the same in networks containing only high-power nodes as in networks containing only low-power nodes.  
         [0028]    [0028]FIG. 5 is a timing diagram representative of the establishment of a network by nodes transmitting at the same, or about the same, power level. Specifically, FIG. 5A is a timing diagram associated with the process by which a device assumes a master role in establishment of a network. Similarly, FIG. 5B is a timing diagram associated with the process by which a device assumes a slave role within an already established network.  
         [0029]    Turning now to FIG. 5A, upon power-up at T 0  a device seeking to establish or join a network first attempts to locate an existing network by listening for a notification message. At T 1 , the device determines whether it has received a notification message while monitoring the network. If by T 2  the device determines that no notification message has been detected, the device initiates establishment of a network by assuming the role of a master node and transmitting a notification message. The notification message is transmitted during the interval bounded by between T 2  and T 3 , and contains identification and network connectivity information. The notification message also identifies the sender as either a high-power node or a low-power node.  
         [0030]    Referring now to FIG. 5B, upon power-up at T 2  a device determines whether a network is operational by listening for a notification message. At T 3 , the device determines whether a notification message has been heard by processing the information received during the listening period. For purposes of example, assume that the device at T 4  ascertains that a notification message was received during such listening period. Since a notification message has been previously transmitted, if the device is to join the existing network it must do so as a slave node. Accordingly, at T 4  the device sends a message indicating that it desires to join the established network as a slave node. This notification message identifies the power level of the node and may also contain network connectivity information.  
         [0031]    [0031]FIG. 6A is a timing diagram relevant to the establishment of a network in which information is exchanged between dual-power and low-power nodes. Such a network may be established between dual-power nodes and low-power nodes when a low-power node desires to take advantage of the relaying capabilities of an overlay network of the present invention; that is, in situations where the low-power node requests communication with a node within the overlay network, but outside of transmission range of the low-power node. The timing diagram of FIG. 6A is described below with reference to FIG. 6B, which includes a subset of the elements within the system of FIG. 2.  
         [0032]    Referring now to FIG. 6A, at T 0  the first wireless node  22  determines that it is desired to transmit data to the second dual-power node  30 . After making this decision, the wireless node  22  attempts to transmit the desired data stream to the second dual-power node at T 1 . At T 2 , node  22  waits for a reply from the second dual-power node  30 . If no reply is detected, node  22  listens for the notification message being transmitted by the master node  20  of the overlay network  14 . This notification message contains information regarding the connectivity of the overlay network  14 , i.e., what nodes are available within the overlay network  14 . From this connectivity information, node  22  determines at T 4  that it can access dual-power node  30  via dual-power node  20 . In order to accomplish this data relay, wireless node  22  initiates contact with dual-power node  20  at T 5 . When dual-power node  20  is not transmitting in high-power mode, at T 6  it transitions to low-power mode and initiates a low-power network with low-power node  22 . Node  22  is then able, at T 7 , to relay the data to dual power-node  20 . At the end of this data transmission (T 8 ), dual-power node  20  transitions to high-power mode and relays the data it received from low-power node  22  to dual-power node  30 .  
         [0033]    [0033]FIG. 7 is a flow chart representation of the sequence of logical steps necessary to establish a network between a low-power node and a dual-power node. Referring to FIG. 7, at step  510  the low-power node  22  (FIG. 2) listens for a notification message that indicating which services are available within the various networks presently operating. Based upon the notification message, at step  515  the low-power node  22  discerns: (i) which services are available within each operating networks, and (ii) the connectivity between the devices offering such services. For purposes of example, assume that based upon the notification message low-power node  22  ascertains the existence of an overlay network  14  having dual-power node  20  as master node and dual-power node  30  as a slave node. Next, in step  520  low-power node  22  determines it desires to transmit data to dual-power node  30 . At step  525 , the low-power node  22  attempts to initiate communication with overlay network  14  by transmitting a request to dual-power node  30 .  
         [0034]    If dual-power node  30  is beyond the transmission range of low-power node  22 , dual-power node  30  will not hear the request signal sent by node  22 . As a consequence, dual-power node  30  will not transmit a reply signal (step  540 ). Upon not receiving any response from dual-power node  30 , low-power will conclude that dual-power node  30  is beyond its transmission range. Node  22  then once again listens for and receives the notification message in order to determine whether another network is available to relay data from node  22  to dual-power node  30  (step  550 ). At step  565 , node  22  determines that it can access dual-power node  30  via the overlay network  14 , which as mentioned above includes both dual-power nodes  20  and  30 . At step  575 , node  22  then retransmits its request to initiate communication to node  20 .  
         [0035]    Upon receiving a request signal from node  22 , dual-power node  20  initiates establishment of a low-power network between itself and node  22 . As an initial step in establishing this low-power network, the dual-power node  20  transitions from a high-power mode to a low-power mode (step  535 ). Once dual-power node  20  has been operating in a low-power mode, it becomes able to establish a low-power network with low-power node  22  (step  545 ). Low-power node  22  then transmits data as desired to dual-power node (step  535 ). The dual-power node  20  then determines whether and the data must be relayed to another node in the overlay network  14  (step  560 ). If the data must be so relayed, the dual-power node transitions back to high-power mode and relays the data to node  30  (steps  570  and  580 ).  
         [0036]    [0036]FIGS. 8 and 9 depict alternately preferred embodiments of the present invention in which overlay network  14  has been modified to incorporate a relay node  40 . A relay node  40  may be included within the overlay network  14  when its constituent nodes are too widely dispersed to communicate with each other. In the embodiments of FIGS. 8 and 9, the relay node  40  operates as a high-power node. The relay node  40  is capable of communication with the nodes in the overlay network  14  in accordance with the applicable protocols, thereby enabling traffic to be transparently relayed between such nodes. Because the relay node  40  is a high-power node, it establishes a connection between itself and nodes within the overlay network  14  in accordance with the timing diagram of FIG. 5.  
         [0037]    Although the above application has been described primarily with reference to specific embodiments, one skilled in the art can readily appreciate that the teachings of the present invention may be applied in other communication contexts. Thus the application is meant only to be limited by the scope of the appended claims.