Abstract:
A distributed wireless sensor network node is disclosed. The wireless sensor network node includes a plurality of sensor modules coupled to a system bus and configured to sense a parameter. The parameter may be an object, an event or any other parameter. The node collects data representative of the parameter. The node also includes a communication module coupled to the system bus and configured to allow the node to communicate with other nodes. The node also includes a processing module coupled to the system bus and adapted to receive the data from the sensor module and operable to analyze the data. The node also includes a power module connected to the system bus and operable to generate a regulated voltage.

Description:
STATEMENT REGARDING RESEARCH &amp; DEVELOPMENT  
       [0001]     This invention was made with Government support under government contract no. DE-AC04-94AL85000 awarded by the U.S. Department of Energy to Sandia Corporation. The Government has certain rights in the invention, including a paid-up license and the right, in limited circumstances, to require the owner of any patent issuing in this invention to license others on reasonable terms. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates generally to wireless sensor networks, and more specifically to modular sensor network nodes.  
       BACKGROUND OF THE INVENTION  
       [0003]     Sensor network nodes are used in many applications. For example, sensor network nodes are used to monitor: seismic activities; atmospheric pressure, temperature and humidity; indoor and outdoor agriculture to increase yield; environmental variation on a fine grained scale; vibration in factories to predict machine failures; a ship&#39;s hull for cracks in a distributed fashion; and HVAC systems in large office buildings.  
         [0004]      FIG. 1 ( a ) is a block diagram of a conventional sensor network  100 ( a ). The sensor network  100 ( a ) can be used in many applications such as, for example, detection of sound, radiation, pollution, etc. The sensor network  100 ( a ) includes a plurality of nodes  104 ( a ),  108 ( a ),  112 ( a ), and  116 ( a ). The nodes  104 ( a )- 116 ( a ) communicate with each other wirelessly. The sensor network  100 ( a ) includes a base station  124 ( a ) that communicates with the nodes  104 ( a )- 116 ( a ) wirelessly.  
         [0005]      FIG. 1 ( b ) is a block diagram of a conventional sensor network  100 ( b ) where the nodes  104 ( b )- 116 ( b ) are connected to each other by a communication link  120 , such as a wired link, an optical link, the Internet or any other communication link. The nodes  104 ( b )- 116 ( b ) can communicate with each other over the communication link  120 . The sensor network  100 ( b ) includes a base station  124 ( b ) that communicates with the nodes  104 ( b )- 116 ( b ) over the communication link  120 . The nodes  104 ( a )- 116 ( a ) and  104 ( b )- 116 ( b ) monitor their environment for data collection or event or object detection purposes. The nodes  104 ( a )- 116 ( a ) and  104 ( b )- 116 ( b ) may process and analyze the data to evaluate the event or the object. The nodes  104 ( a )- 116 ( a ) and  104 ( b )- 116 ( b ) can also transmit collected data to the base station  124 ( a ) and  124 ( b ), respectively, for analysis or storage.  
         [0006]      FIG. 2  is a block diagram of one of the nodes  104 ( a )- 116 ( a ) and  104 ( b )- 116 ( b ) (shown in FIGS.  1 ( a ) and  1 ( b )) in more detail. For ease of description, the node of  FIG. 2  will be designated as the node  104 . The node  104  includes sensor modules  204 ,  208 ,  212 ,  216  connected to a central processor  224 . The sensor modules  204 - 216  sense the environment for data collection or event or object detection purposes. The sensor modules  204 - 216  typically do not have capability to process and analyze the data. Accordingly, the data collected by the sensor modules  204 - 216  are transmitted to the central processor  224 . The central processor  224  processes the data to evaluate the event or the object. The node  104  transmits the processed data to the base station  124 ( a ) or  124 ( b ) (shown in FIGS.  1 ( a ) and  1 ( b )) for storage and/or further analysis.  
         [0007]     At present, two system level architectures are used for the wireless sensor network node. The first architecture incorporates an optimized, less powerful system that is specific to a single application. The first architecture generally includes a less powerful (i.e., low processing power), optimized central processor that is designed or chosen only for a specific application. Since the first architecture is specific to a single application, it is inflexible and cannot be extensively modified for other applications. For example, a wireless sensor network node may be designed exclusively for seismic applications. The central processor can be designed or chosen for only seismic related applications including processing and analyzing seismic data, and therefore the central processor need not be a powerful processor. Since these specific central processors typically have low processing power, they consume relatively less power.  
         [0008]     The second architecture incorporates a non-optimal, more powerful system that can be adapted for different applications. The second architecture includes a powerful central processor that can be used for different applications. Since the second architecture can be used for different applications, it is flexible. For example, a wireless sensor network node can be designed to monitor seismic events, radiation, or atmospheric pressure and temperature in different applications. The central processor is designed or chosen to be more general, flexible, and computationally powerful to process different types of data, and therefore the central processor needs to be a powerful processor (i.e., high processing power). Since the central processor must possess high processing power, it consumes a large amount of power.  
         [0009]     The first architecture, which is the inflexible system, is generally a one time solution. The first architecture cannot be extensively adapted to different applications, but consumes relatively small amounts of power. The second architecture, which is the flexible system, consumes large amounts of power, but can be adapted to different applications. The second architecture is unsuitable for applications in locations where the sensor network node  104  (shown in  FIG. 2 ) must operate on a limited power supply such as battery power. Thus, neither of these systems is satisfactory to produce efficient and flexible sensor systems.  
         [0010]     Furthermore, the two architectures are essentially implemented around a central processor. The central processor is typically a microprocessor that performs all functions of the nodes. The central processor is required to perform complicated tasks as well as simple tasks simultaneously. For example, the central processor is required to perform complicated tasks such as processing and analysis of the sensed data, and also perform simple tasks related to the management and control of the node  104  including polling of the sensors  204 - 212 . Thus, the two architectures utilize the central processor inefficiently.  
         [0011]     Accordingly, there is a need for a wireless sensor network node system that is flexible and adaptable, yet that does not consume large amounts of power and is efficient for general use.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention is directed to a modular sensor network node. The sensor network node may include a plurality of sensor modules coupled to a system bus and configured to sense a parameter and operable to generate data representative of the parameter. The parameter may be sound, radiation, temperature, pressure, pollution, or any other parameter. The node may include a communication module coupled to the system bus and configured to allow the network node to communicate with other nodes in the network. The node may also include a processing module coupled to the system bus and adapted to receive the data from the sensor module and to analyze the data. The node also includes a power module connected to the system bus and operable to generate one or several regulated voltages to power the node.  
         [0013]     The sensor module may include a system resource configured to sense a parameter and operable to generate data representative of the sensed parameter. The sensor module also include a resource specific processor coupled to the system resource and configured to control the system resource. The resource specific processor is a low power and low performance processor designed to perform limited specific tasks related to the management and control of the sensor module and use less power than other general purpose processors. The resource specific processor is adapted to receive the data from the system resource. The sensor module also includes a distributed controller coupled to the resource specific processor and operable to regulate the power consumption of the sensor module as well as provide communications with other modules on the same node. The sensor module may also include data storage coupled to the resource specific processor and adapted to store the data collected by the system resource. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     FIGS.  1 ( a ) and  1 ( b ) are block diagrams of conventional sensor networks.  
         [0015]      FIG. 2  is a block diagram of a node used in the sensor networks of FIGS.  1 ( a ) and  1 ( b ).  
         [0016]      FIG. 3  is a block diagram of a sensor network node in accordance with one embodiment of the invention.  
         [0017]      FIG. 4  is a block diagram of a sensor module used in the sensor network node of  FIG. 3 .  
     
    
     DETAILED DESCRIPTION  
       [0018]     The various features and methods of the invention will now be described in the context of wireless sensor network nodes. Those skilled in the art will recognize that the invention is applicable to other types of network nodes.  
         [0019]     Throughout the description of the invention, implementation-specific details will be given on how the invention is used to sense an event or an object. These details are provided to illustrate the preferred embodiments of the invention and not to limit the scope of the invention. The scope of the invention is set in the claims section.  
         [0020]      FIG. 3  is a block diagram of a wireless sensor network node  300  in accordance with one embodiment of the invention. The node  300  includes a system bus  304  that is connected to a processing module  308 . The processing module  308  includes a general purpose processor  312  such as a microprocessor. As will be described later, the general purpose processor  312  performs complex processing tasks such as data processing and analysis related to an event, an object or the environment. The general purpose processor  312  functions as a shared resource for all other modules in the node  300 . Other modules in the node  300  may request the processing module  308  to perform tasks that the other modules do not have the resources to perform.  
         [0021]     The node  300  also includes a communication module  316  connected to the system bus  304 . The communication module  316  includes a transceiver  320 , which may be an optical transceiver, a wireless transceiver or any other type of transceiver. In one embodiment, the communication module  316  includes a wireless transceiver and a wire-line or an optical transceiver. The transceiver  320  allows the node  300  to communicate with other nodes in the network or the base station  124  (shown in  FIG. 1 ).  
         [0022]     The communication module  316  performs all necessary functions required to allow the node  300  to communicate with other nodes in the network and also with the base station, thus allowing the other modules in the node  300  to completely rely on the communication module  316  for all external, i.e. off-node, communications needs. Additionally, the communication module  316  performs network related tasks such as, for example, routing network traffic not intended for the local node (i.e., node  300 ) without involving the other modules in the node  300 , thus allowing the other modules in the node  300  to be undisturbed by network related events that do not concern the other modules.  
         [0023]     The node  300  also includes a sensor module  324  that is connected to the system bus  304 . The sensor module  324  includes a sensor  328  designed to sense or detect parameters such as, for example, sound, seismic activities or other parameters. The sensor  328  may also be designed to detect chemical or biological agents or radiation or any other parameters that can be sensed. In one embodiment, the node  300  can have a plurality of sensor modules  324 . Also, if the application requires, one or more sensor nodes  300  can be added or removed from the network. The sensor module  324  includes a resource specific processor (not shown in  FIG. 3 ) that controls and manages the sensor  328 . The resource specific processor is a low power processor having limited processing capability. The sensor module  324  may also be capable of storing a small amount of data from sensor readings. The operation of the sensor module  324  and the resource specific processor will be described in more detail later.  
         [0024]     The node  300  also includes a power supply module  332  that is connected to the system bus  304 . The power supply module  332  provides power to the various modules of the node  300  via the system bus  304 . The power supply module  332  includes one or more regulated power supplies  336  that provide one or more regulated voltages. In one embodiment, the power supply module  332  includes one or more regulators to provide 3.3 volts DC or 5.0 volts DC or other desired voltages to the node  300 . In many applications, it is necessary to control and limit the amount of power being used by the node. In many remote applications, only battery power may be available to the node  300 . Thus it is necessary to limit the amount of power being used. Consequently, it is necessary to carefully monitor the amount of power being used. In one embodiment, the power supply module  332  includes a processor (not shown in  FIG. 3 ) to monitor how much power has been consumed and how much power is left in the batteries.  
         [0025]      FIG. 4  is a detailed block diagram of the sensor module  324  and the system bus  304  (shown in  FIG. 3 ). The system bus  304 , to which the sensor module  324  is connected, includes a power bus  404 , may include one or more data buses  408 , and a control bus  412 . The power supply module  332  (shown in  FIG. 3 ) provides regulated power that is distributed by the power bus  404  among various modules of the node  300  (shown in  FIG. 3 ). In one embodiment, the power bus  404  distributes 3.3 V, 5 V or any other desired voltage from batteries or other power sources in the power module  332  (shown in  FIG. 3 ). The power bus  404  also provides ground to the sensor module  324 .  
         [0026]     The control bus  412  is generally used to transmit control signals (low bandwidth signals) among the modules  308 - 332  (shown in  FIG. 3 ). For example, a short message identifying that a new sensor module  324  has been added to the node  300  can be broadcast on the control bus  412 . The other modules  316 - 332  can receive the short message over the control bus  412 . In contrast, the data bus  408  allows high bandwidth transmission among the modules  308 - 332 . By separating the data bus  312  from the control bus  308 , shorter control messages can be transmitted without being delayed by longer data messages and longer data messages can utilize a more powerful higher bandwidth bus.  
         [0027]     The sensor module  324  also includes a distributed controller  416 . In one embodiment, the distributed controller  416  includes a power control algorithm designed to lower the overall power consumption of the sensor module  324 . The distributed controller also includes communication algorithms to allow the sensor module  324  to communicate with any other module in the node. These communications may provide for identification of the other modules present in the node, requests for utilization of the other system resources on other modules, or for other purposes. The distributed controller  416  can be implemented as software, can be implemented as an application specific integrated circuit (ASIC), or can be implemented on a field programmable gate array (FPGA) or programmable logic device (PLD).  
         [0028]     The sensor module  324  also includes a processor  420 , which is designed to perform specific sensor related tasks. The processor  420  is also referred to as the resource specific processor  420 . In one embodiment, the resource specific processor  420  is a low power, low computational processor capable of configuring the sensor module  324 , reading data collected by the sensor module  324 , and may perform preliminary data analysis. Since the resource specific processor  420  is a low computational performance processor, it does not perform any significant data analysis, and thus uses only a limited amount of power.  
         [0029]     In contrast, the general purpose processor  312  (shown in  FIG. 3 ) is a high performance microprocessor capable of complicated data analysis necessary to evaluate a detected event or an object. If the resource specific processor  420  determines that the data collected by the sensor module  324  needs to be analyzed in greater detail, the data is preferably transmitted to the processing module  308  for analysis. In one embodiment, the general purpose processor  312  will perform computations on the collected data such as, for example, a fast Fourier transform (FFT), pattern recognition, or another type of computation. The general purpose processor  312  will then analyze the results of these computations to determine if something of importance exists in the data such as, for example, the detection of an unknown object or event in the surrounding environment. The general purpose processor  312  may also perform data fusion on data collected from a plurality of sensor modules. The general purpose processor  312  may also perform distributed computations with other nodes in the network or communicate data and/or processing results to a base station.  
         [0030]     In one embodiment, the sensor module  324  is an acoustic sensor module. The acoustic sensor module may operate on a “trip” mode where it simply waits for any sound. When there is a sound, the acoustic sensor module trips and starts recording data. The recorded data is transmitted to the processing module  308  (shown in  FIG. 3 ) with instructions to analyze and identify the sound. The act of tripping on a sound and recording the data does not require significant processing power, and thus can be controlled by the resource specific processor  420 . In contrast, analyzing the data to identify the sound requires considerable processing power, which is performed by the processing module  308  (shown in  FIG. 308 ). The need to identify the sound does not arise very often, allowing the processing module  308  (shown in  FIG. 3 ) to remain asleep most of the time. During periods when identification of sound is not needed, only the resource specific processor  420  on the sensor module  324  needs to be active.  
         [0031]     In one embodiment the sensor module may include a camera. The camera can be a digital, optical, video or any other type of camera.  
         [0032]     The sensor module  324  may also include a data storage device  424 , which allows the module  324  to store data. The data storage device  424  can either be separate from the resource specific processor  420  or integrated into the resource specific processor  420 . In one embodiment, the sensor module  324  includes a first data storage device integrated into the processor  420  for buffering data and a second data storage device separate from the processor  420  for off-chip storage of long-term data. This second data storage device may be in a form such as, for example, a random access memory (RAM) chip, an electronically erasable programmable read-only memory (EEPROM) chip, a flash memory storage device, or other storage types.  
         [0033]     The sensor module  324  includes a sensor  328  designed to sense and detect an event, an object, or any other parameter that can be sensed. The sensor  328  is also referred to as the system resource  328 , which performs the primary task of the module  324 . For example, in the case of an acoustic sensor module, the system resource  328  is an acoustic sensor, and in the case of a radiation sensor module, the system resource  328  is a radiation sensor.  
         [0034]     The distributed controller  416 , the resource specific processor  420 , the data storage  424  and the system resource  428  can be implemented separately on the module  324 , integrated into a single chip, or combined in some other manner.  
         [0035]     In one embodiment, the resource specific processor  420  is a customized processor designed to perform simple tasks. The resource specific processor  420  can manage basic functions of the sensor module  324  such as turning on or off the system resource  328 . The resource specific processor  420  can receive a sensor reading, perform simple preliminary computations on this data, and store a small amount of data in the data storage  424 . Also, the resource specific processor  420  can act as a router for network traffic received by a transceiver  320  on the communication module  316 . During operation, the node  300  (shown in  FIG. 3 ) may receive wireless traffic that are not intended for the node  300 , but must be routed to another node. The resource specific processor  420  routes wireless traffic that is not intended for the local node, i.e., node  300 , without disturbing any other modules. For a processing module  308 , the resource specific processor  420  may act as a processing request scheduler and manage processing request responses. These processing requests may come to the processing module  308  from another module, another node, or a base station.  
         [0036]     The basic management of the sensor module  324  is separated from the central processor, i.e., the processing module  308  (shown in  FIG. 3 ), and is assigned to the resource specific processors  420 , so that the processing module  308  need not be involved in routine tasks. The processing module  308  (shown in  FIG. 3 ) can be dormant and save power while the resource specific processors  420 , which use less power, perform basic management tasks and other routine tasks of each individual module and between modules, and thus for the node as a whole.  
         [0037]     There are instances when the processing module  308  (shown in  FIG. 3 ) must act. For example, if an input to a sensor exceeds a predetermined threshold, the processing module  308  may be awakened. Also, if a wireless packet is destined for the local node, the processing module  308  (shown in  FIG. 3 ) can be awakened. At that time, the data can be transferred to the general purpose processor  312  (shown in  FIG. 3 ), and its full capabilities can be utilized to process the data.  
         [0038]     The node  300  (shown in  FIG. 3 ) allows easy upgradeability. If a technology advancement is made in a particular module in the node  300 , the module can be replaced, and a complete system redesign, as in the case of a conventional centralized system, is unnecessary.  
         [0039]     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.