Presented by Viraj Anagal Kaushik Mada. Presented to Dr. Mohamed Mahmoud. ECE 6900 Fall 2014 Date: 09/29/2014 1

Transcription

1 Presented by Viraj Anagal Kaushik Mada Presented to Dr. Mohamed Mahmoud ECE 6900 Fall 2014 Date: 09/29/2014 1

2 Outline Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 2

3 Motivation Sensors integrated into systems. Efficient delivery of sensed information. Limiting the number of sensors that may be deployed. Fewer catastrophic failures. Conservation of natural resources. Improved manufacturing productivity, Improved emergency response Enhanced homeland security 3

4 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 4

5 Overview A Wireless Sensor Network (WSN) consists of base stations and a number of wireless sensors (nodes). Data is collected at the wireless sensor node, compressed, and transmitted to the gateway directly. If required, uses other wireless sensor nodes to forward data to the gateway. 5

6 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 6

7 Wireless Sensor Network Components 7

8 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 8

9 Characteristics Of WSN Requirements: small size, large number, tether less, and low cost. The ideal wireless sensor is networked and scaleable, consumes very little power. Is smart and software programmable, capable of fast data acquisition, reliable and accurate over the long term. Costs little to purchase and install, and requires no real maintenance. Examples of low data rate sensors include temperature, humidity, and peak strain captured passively. Examples of high data rate sensors include strain, acceleration, and vibration. Constrained by Energy, computation, and communication Small size implies small battery Low cost & energy implies low power CPU, radio with minimum bandwidth and range Ad hoc deployment implies no maintenance or battery replacement To increase network lifetime, no raw data is transmitted 9

10 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 10

11 Individual Wireless Sensor Node Architecture Sensor event driven data collection model minimizes the power consumed by the system. Depending on the sensors to be deployed, the signal conditioning block can be reprogrammed or replaced. The radio link may be swapped out as required for a given applications wireless range requirement and the need for bidirectional communications. The use of flash memory allows the remote nodes to acquire data on command from a base station, or by an event sensed by one or more inputs to the node. 11

12 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 12

13 Role of Microprocessors or Embedded Systems The Microcontroller Unit (MCU) is the primary choice for in node processing Power consumption is the key metric in MCU selection. The MCU should be able to sleep whenever possible, like the radio. Memory requirements depend on the application ATmega128L and MSP430 are popular choices Managing data collection from the sensors Performing power management functions Interfacing the sensor data to the physical radio layer Managing the radio network protocol. The hardware should be designed to allow the microprocessor to judiciously control power to the radio, sensor, and sensor signal conditioner. 13

14 Radio Commercially available chips Available bands: 433 and 916MHz, 2.4GHz ISM bands Typical transmit power: 0dBm. Power Control Sensitivity: as low as 110dBm Narrowband (FSK) or Spread Spectrum communication. DS SS (e.g., ZigBee) or FH SS (e.g., Bluetooth) Relatively low rates (<100 kbps) save power. Power Supply AA batteries power the vast majority of existing platforms. They dominate the node size. Alkaline batteries offer a high energy density at a cheap price. The discharge curve is far from flat, though. Lithium coin cells are more compact and boast a flat discharge curve. Rechargeable batteries: Who does the recharging? Solar cells are an option for some applications. Fuel cells may be an alternative in the future. Energy scavenging techniques are a hot research topic (mechanical, thermodynamical, electromagnetic). 14

15 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 15

16 Wireless Sensor Networks Architecture Star Network (Single Point to Multipoint) Mesh Network Hybrid Star Mesh Network 16

17 Wireless Sensor Networks Architecture Star Network (Single Point to Multipoint) A single base station can send and/or receive a message to a number of remote nodes. The remote nodes can only send or receive a message from the single basestation, they are not permitted to send messages to each other. Advantages Is in its simplicity and the ability to keep the remote node s power consumption to a minimum. low latency communications between the remote node and the basestation. Disadvantages Basestation must be within radio transmission range of all the individual nodes Not as robust as other networks due to its dependency on a single node to 17 manage the network.

18 Wireless Sensor Networks Architecture Cont. Mesh Network Any node in the network to transmit to any other node in the network that is within its radio transmission range. This allows for what is known as multihop communications It can use an intermediate node to forward the message to the desired node. Advantages Redundancy and Scalability The range of the network is not necessarily limited by the range in between single nodes. Disadvantages Power consumption is higher for multihop communications. Limited battery life. The time to deliver the message also increases due to increase in nodes in path. 18

19 Wireless Sensor Networks Architecture Cont. Hybrid Star Mesh Network The lowest power sensor nodes are not enabled with the ability to forward messages. This allows for minimal power consumption to be maintained. Other nodes on the network are enabled with multihop capability, allowing them to forward messages from the low power nodes to other nodes on the network. Generally, the nodes with the multihop capability are higher power, and if possible, are often plugged into the electrical mains line. This topology is implemented by the coming mesh networking standard known as ZigBee. 19

20 Wireless Sensor Networks Architecture Cont. Hybrid Star Mesh Network The lowest power sensor nodes are not enabled with the ability to forward messages. This allows for minimal power consumption to be maintained. Other nodes on the network are enabled with multihop capability, allowing them to forward messages from the low power nodes to other nodes on the network. Generally, the nodes with the multihop capability are higher power, and if possible, are often plugged into the electrical mains line. This topology is implemented by the coming mesh networking standard known as ZigBee. 20

21 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 21

22 Radio Options for the Physical Layer in Wireless Sensor Networks ZigBee Bluetooth (IEEE and.2) IEEE IEEE802.11x 22

23 Radio Options for the Physical Layer in Wireless Sensor Networks IEEE802.11x local area networking for relatively high bandwidth data transfer between computers or other devices. The data transfer rate ranges from as low as 1 Mbps to over 50 Mbps. Typical transmission range is 300 feet with a standard antenna. Both frequency hopping and direct sequence spread spectrum modulation schemes are available. While the data rates are certainly high enough for wireless sensor applications, the power requirements generally preclude its use in wireless sensor applications. 23

24 Radio Options for the Physical Layer in Wireless Sensor Networks Bluetooth (IEEE and.2) Bluetooth is a personal area network (PAN) standard that is lower power than Bluetooth uses a star network topology that supports up to seven remote nodes communicating with a single basestation. Limitations of Bluetooth in WSN Relatively high power for a short transmission range. Nodes take a long time to synchronize to network when returning from sleep mode, which increases average system power. Low number of nodes per network (<=7 nodes per piconet). Medium access controller (MAC) layer is overly complex when compared to that required for wireless sensor applications. 24

25 Radio Options for the Physical Layer in Wireless Sensor Networks IEEE The standard was specifically designed for the requirements of wireless sensing applications. It specifies multiple data rates and multiple transmission frequencies. The power requirements are moderately low. The hardware is designed to allow for the radio to be put to sleep, which reduces the power to a minimal amount When the node wakes up from sleep mode, rapid synchronization to the network can be achieved. Characteristics of IEEE Transmission frequencies, 868 MHz/ MHz/ GHz. Data rates of 20 Kbps (868 MHz Band) 40 Kbps (902 MHz band) and 250 Kbps (2.4 GHz band). Supports star and peer to peer (mesh) network connections. Standard specifies optional use of AES 128 security for encryption of transmitted data. Link quality indication, which is useful for multi hop mesh networking algorithms. 25

26 Radio Options for the Physical Layer in Wireless Sensor Networks ZigBee The ZigBee alliance specifies the IEEE as the physical and MAC layer and is seeking to standardize higher level applications such as lighting control and HVAC monitoring. The ZigBee network specification, to be ratified in 2004, will support both star network 26 and hybrid star mesh networks.

27 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 27

28 Power Consideration in Wireless Sensor Networks Fig. shows a chart outlining the major contributors to power consumption in a typical 5000 ohm wireless strain gage sensor node versus transmitted data update rate. 28

29 Power Consideration in Wireless Sensor Networks Cont. The single most important consideration for a wireless sensor network is power consumption. There are a number of strategies that can be used to reduce the average supply current of the radio, including: Reduce the amount of data transmitted through data compression and reduction. Lower the transceiver duty cycle and frequency of data transmissions. Reduce the frame overhead. Implement strict power management mechanisms (power down and sleep modes). Implement an event driven transmission strategy; only transmit data when a sensor event occurs. Power reduction strategies for the sensor itself include: Turn power on to sensor only when sampling. Turn power on to signal conditioning only when sampling sensor. Only sample sensor when an event occurs. Lower sensor sample rate to the minimum required by the application. 29

30 OUTLINE Motivation Overview Wireless Sensor Network Components Characteristics of Wireless Sensor Network Individual Wireless Sensor Network Architecture Role of Micro Processors or Embedded Systems Wireless Sensor Network Architectures Radio options for Wireless Sensor Network Power considerations in Wireless Sensor Network Applications of Wireless Sensor Network Conclusion References 30

31 Applications of Wireless Sensor Networks Structural Health Monitoring Smart Structures Industrial Automation Civil Structure Monitoring Environmental Monitoring Medical Application Military and national security application Nearly anything you can imagine 31

32 Applications of Wireless Sensor Networks Structural Health Monitoring Smart Structures Wireless sensing will allow assets to be inspected when the sensors indicate that there may be a problem, reducing the cost of maintenance and preventing catastrophic failure in the event that damage is detected. The use of wireless reduces the initial deployment costs, as the cost of installing long cable runs is often prohibitive. Wireless sensing applications demand the elimination of not only lead wires, but the elimination of batteries as well, due to the inherent nature of the machine, structure, or materials under test. These applications include sensors mounted on continuously rotating parts, within concrete and composite materials, and within medical implants. Sensors embedded into machines and structures enable condition based maintenance of these assets 32

33 Applications of Wireless Sensor Networks Industrial Automation The use of wireless sensors allows for rapid installation of sensing equipment and allows access to locations that would not be practical if cables were attached. Other applications include energy control systems, security, wind turbine health monitoring, environmental monitoring, location based services for logistics, and health care. 33

34 Applications of Wireless Sensor Networks Civil Structure Monitoring One of the most recent applications of today s smarter, energy aware sensor networks is structural health monitoring of large civil structures, such as the Ben Franklin Bridge which spans the Delaware River, linking Philadelphia and Camden, N.J 34

35 Applications of Wireless Sensor Networks Environmental Monitoring 1 Great Duck Island 150 sensing nodes deployed throughout the island relay data temperature, pressure, and humidity to a central device. Data was made available on the Internet through a satellite link. 35

36 Applications of Wireless Sensor Networks Environmental Monitoring 2 Zebranet: a WSN to study the behavior of zebras Special GPS equipped collars were attached to zebras Data exchanged with peer to peer info swaps Coming across a few zebras gives access to the data 36

37 Applications of Wireless Sensor Networks Medical Application Vital sign monitoring Accident recognition Monitoring the elderly Intel deployed a 130 node network to monitor the activity of residents in an elder care facility. Patient data is acquired with wearable sensing nodes (the watch ) 37

38 Conclusion Wireless sensor networks are enabling applications that previously were not practical. As new standards based networks are released and low power systems are continually developed, we will start to see the widespread deployment of wireless sensor networks. 38

39 References Wireless sensor networks Wireless Sensor Network Topologies A Standard Smart Transducer Interface IEEE New technological vistas for systems and control: the example of wireless networks network Wireless Sensor Networks: Principles and Applications 39

40 Thank You! 40

41 Questions??? Can you think of any applications where a wireless sensor network would be the best solution? Do you foresee wireless sensor networks becoming ubiquitous within the next ten years? During your lifetime? 41