Abstract:
A communication center that has communication as well surveillance capabilities is provided. The communication center includes a server and a plurality of UWB nodes. The server is configured to implement a medium assess control (MAC). The plurality of ultra-wideband (UWB) nodes are in communication with the server. Moreover, each UWB node of the communication center is controlled at least in part by the MAC.

Description:
BACKGROUND 
       [0001]    Ultra-wideband (UWB) radio units can serve as both a high-speed communication unit and a precise surveillance radar unit. Traditional communication systems commonly employ Medium Access Control (MAC). A MAC or MAC layer is a networking protocol layer that controls communications such as transmission requests, authentication and other overheads in a network. Although the communication functions of an UWB system could benefit from the use of a MAC layer, the surveillance functions of the UWB system are not contemplated by MAC. Hence, simply applying traditional MAC mechanisms of communication networks to an UWB communication and surveillance network is not suited to maximize the benefits of UWB radios. How to design a sensor network to accommodate both communication and surveillance capabilities of UWB radios is desired. 
         [0002]    For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a novel communication and surveillance network structure of UWB sensor arrays and a novel multidimensional division multiple access (MDMA) technique which bridges the gaps between the communication and the surveillance capabilities of UWB sensor arrays. 
       SUMMARY OF INVENTION 
       [0003]    The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the invention. In one embodiment a communication center is provided. The communication center includes a server and a plurality of UWB nodes. The server is configured to implement a medium assess control (MAC). The plurality of ultra-wideband (UWB) nodes are in communication with the server. Moreover, each UWB node of the communication center is controlled at least in part by the MAC. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the detailed description and the following figures in which: 
           [0005]      FIG. 1  is a block diagram of an UWB array network of one embodiment of the present invention; 
           [0006]      FIG. 2  is a state diagram illustrating an MDMA algorithm of one embodiment of the present invention; and 
           [0007]      FIG. 3  is a block diagram of another embodiment of an UWB array network of the present invention. 
       
    
    
       [0008]    In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text. 
       DETAILED DESCRIPTION 
       [0009]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof. 
         [0010]    Embodiments of the present invention provide a communication and surveillance network of arrays of UWB nodes that implement a MAC (or MAC layer). A UWB node array network of embodiments consists of multiple local centers, which can function as either hosts or clients or both. Each local center has a server and multiple UWB nodes. In one embodiment, the links between the server and UWB nodes inside a local center are wired and the links between UWB nodes from different local centers are wireless. Moreover, in embodiments, multiple UWB transceivers share a single MAC which resides in a common server. 
         [0011]    Referring to  FIG. 1 , a block diagram of UWB array network  100  of one embodiment of the present invention is illustrated. As illustrated, two local centers, local center  102  and local center  104  are shown. Although, only two local centers  102  and  104  are shown, more local centers could be used as illustrated in  FIG. 3 . The local centers  102  and  104  of  FIG. 2  (or communication centers) may be vehicles or stationary objects. Each local center  102  and  104  includes a server and a plurality of nodes. In particular, local center  102  includes nodes  110  ( 1 -N) and server  106  and local center  104  includes nodes  112  ( 1 -N) and server  108 . Each node  110  ( 1 -N) and  112  ( 1 -N) includes a UWB transceiver (or UWB sensor). The nodes  110  ( 1 -N) and  112  ( 1 -N) are placed in different locations within the respective local centers  102  and  104 . Moreover, in embodiments, one or more sensors in a local center are positioned to detect UWB signals from different directions. The server  106  and  108  in the respective local centers  102  and  104  include the MAC layer that controls the respective nodes  100  ( 1 -N) and  112  ( 1 -N). 
         [0012]    In one embodiment, multi-dimension division multiple access (MDMA) that includes channel separation, time division and host-client role division seamlessly incorporates various surveillance and communication services in the arrangement as set out in  FIG. 1  to form network  100  having high reliability, fault tolerance and determinism.  FIG. 2  illustrates a high level state diagram  200  of MDMA algorithms used in some embodiments of the present invention. At start up, a local center  102  or  104  is preconfigured to search in a steady state with all nodes sending out a beacon signal in each communication frame and changing into receiving mode during the rest of the frame. Beacon time slots are different for each node in order to avoid collisions since the search channel is common for all local centers. Once another local center is detected, the two local centers  102  and  104  negotiate their roles ( 202 ). That is, the local centers  102  and  104  decide who should be the host and who should be the client. The elected host then uses one designated node to broadcast beacon signals to keep different local centers synchronized and informed of the time division and channel separation. 
         [0013]    In one embodiment multiple channels are established to accommodate multiple service simultaneously using code division multiple access (CDMA). In the embodiment illustrated in  FIG. 2 , different channels are separated by different pseudo-random code sequences which are known prior by both the host and the client ( 204 ). In an embodiment where UWB pulses use different frequency bands, multiple channels are separated by frequency division multiple access (FDMA) ( 204 ). Moreover, in the embodiment of  FIG. 2 , different services are scheduled with time division multiple access (TDMA) ( 206 ). By carefully assigning time slots to each service, deterministic latency and QoS are guaranteed. The host uses one node to broadcast a beacon signal which has a time schedule and code sequence information for all the nodes. Once the role division, channel separation and time division are determined, the network goes into a steady state where all services are delivered and QoS is guaranteed. When new service requests, fault detections, network topology changes, etc. take place, the old steady state is broken and the network will once again go through role division, channel separation and time division until it once again reaches a steady state. 
         [0014]    An example of a network  300  with more than two local centers is illustrated in  FIG. 3 . As illustrated in  FIG. 3 , a first local center ( 302 ) includes server  308  and nodes  310  ( 1 - 4 ). A second local center  304  includes server  318  and nodes  312  ( 1 - 4 ) and a third local center  306  includes server  340  and nodes  314  ( 1 - 4 ). In the example of  FIG. 3 , nodes  310  ( 1 - 4 ) in the first local center  302  cannot directly communicate with nodes  314  ( 1 - 4 ) in the third local center  306 . In this scenario, multiple hosts are used. In  FIG. 3 , nodes  312 - 1  and  312 - 2  in local center  320  can only connect to nodes  310 - 1  and  310 - 2  respectfully in local center  302  and nodes  312 - 3  and  312 - 4  in local center  304  can only connect to nodes  314 - 2  and  314 - 4  respectfully in local center  306 . In one embodiment, all local centers  302 ,  304  and  306  are formed into a single network  300  through role division. For example, server  308  of the first local center  302  serves as host and server  318  of the second local center  304  serves as both client and host. In particular, the first local center  302  serves as a first host whose clients  320  are nodes  312 - 1  and  312 - 2  of the second local center  304 . Moreover, as illustrated in  FIG. 3 , nodes  312 - 3  and  312 - 4  of the second local center  304  form a second host  322  to a second client that is the third local center  306 . In the example of  FIG. 3 , the second host  322  of nodes  312 - 3  and  312 - 4  are in communication to clients made up of nodes  314 - 2  and  314 - 4  respectfully. The arrangement of  FIG. 3  is made by way of example and not by way of limitation. Other arrangements are contemplated. For example, nodes  312 - 3  and  312 - 4  could also connect to nodes  310 - 3  and  3104  respectively. In this scenario, nodes  312 - 3  and  312 - 4  would provide host communications with nodes  314 - 2  and  314 - 4  of the third local center  306  and client communications with nodes  310 - 3  and  310 - 4  of the first local center  302  (though in a different time slot than when communicating with the third local center  306 ). 
         [0015]    The UWB sensor array networks  100  and  300  as illustrated in  FIGS. 1 and 3  provide various services. For example, the UWB array network may provide rangefinder functions. This function is accomplished when two UWB nodes in an array network calculate the distance between themselves by sending and receiving short messages and measuring the transit time of the signals. Another function includes intrusion detection. In this function two UWB nodes in an array network work as a bi-static radar pair with one a transmitter and the other a receiver. By detecting the received pulse energy, the UWB receiver can detect whether an object has intruded into a pre-defined area around the transmitter and receiver. Another function relates to tracking and collision avoidance. In this function, UWB sensor arrays are used as mono-static radars to scan, track and possibly avoid colliding into other objects in nearby space. Still another function includes deterministic communication. In this function, the time instant and duration of time slots are reserved so that latency of data bits is fixed or deterministic. Its ideal applications include real-time close-loop control information and actuator data. Another function includes real-time communication. In real time communication, the overall data rate is guaranteed but the response latency is not strictly the same for all the data packets, e.g. in video and audio streaming applications. Yet another function includes non-real-time communication. In a non-real-time communication, correct data delivery and maximum delay time are the only two requirements and the latency and delay time are not critical to the application. The above services are made by way of examples and not by way of limitation. Other services are contemplated. 
         [0016]    The UWB sensor array networks  100  and  300  as illustrated in  FIGS. 1 and 3  provide advantages over other communication systems. For example, the array networks provide location-awareness. Since each local center has multiple nodes with UWB sensors in different locations, the local center can calculate its location in 3D space. This is accomplished with three or more nodes reflecting range pulses of objects to determine distances to the objects and using triangulation techniques on the distance determinations to determine location information. Another advantage relates to fault tolerance. In embodiments of the present invention if a node is broken, another node in a respective local center is substituted. Still another advantage relates to fault resolution. When one node is determined to not be working well, the respective local center resets the malfunctioning node while one or more other nodes in the local center remain working. Yet another advantage is with embodiments in which predictable outages of nodes can be determined and addressed. In particular, since relative position of local centers can be precisely determined as discussed above, each local center can predict when one or more of its nodes will lose connections to nodes in other local centers and take action accordingly. Another advantage of embodiments of the networks is that deterministic latency can be handled. In particular, since TDMA is used in the MAC layer, deterministic latency can be managed. Still yet another advantage is that embodiments provide high reliability since the system will still function even when one or more UWB sensors in the nodes fail. 
         [0017]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.