Introduction to Wireless Networking ECE/CSC 575 – Section 1 Introduction to Wireless Networking Lecture 23 Dr. Xinbing Wang

Overview of the Course Part 1: Wireless communication systems (Chapter 1) Flexibility to support roaming Limitations: Geographical coverage, transmission rate, and transmission errors Part 2: Wireless communication technology Radio propagation (Chapter 5) Spread spectrum (Chapter 7) Part 3: Current wireless systems Cellular network architecture (Chapter 10) Mobile IP (Chapter 12) Wireless LAN (Chapter 11/13/14) Part 4: Other wireless networks Ad hoc networks (Reading materials) Sensor networks (Reading materials) Wireless PAN (Chapter 15) Satellite systems (Chapter 9) Part 5: Wireless Security In our daily lives, wireless communication technology is used everywhere, from VCR remote control, to satellite weather forecast. The common characteristics of wireless communication systems is that there is no physical (visible) lines between two communication parties. Therefore, a wireless system is able to support user roaming. For example, we do not have to use a remote control in a particular position to.., we can use our cellular phones almost everywhere. However, there are many impairments to a wireless channel, causing a lot of limitations to wireless communications system such as geographical.. (signal fading, additional noise, cochannel interference. Wireless systems also suffers from limit usable spectral width, so that the transmission rate is relatively low. Specifically, wireless cellular systems based on radio propagation has been evolving from narrow band (1G, late 170s) to wide-band(3G). With their geographical coverage limitation, wireless systems need a backbone network to extend their geographical coverage to enable global communications. The interoworking of a wireless network as the front-end and the Internet as the backbone has received much attention in recent years. So we will first take a look at the network architecture of current wireless systems,…, Then we will talk about the evolution from 2G to 3G systems. Dr. Xinbing Wang

Wireless Sensor Networks Architecture Hardware and examples Applications Design issues: hardware, fault tolerance, energy conservation and so on. Dr. Xinbing Wang

Architecture Internet, Satellite, etc Several thousand nodes Sink Task Manager Several thousand nodes Nodes are tens of feet of each other Densities as high as 20 nodes/m3 I.F.Akyildiz, W.Su, Y. Sankarasubramaniam, E. Cayirci, “Wireless Sensor Networks: A Survey”, Computer Networks (Elsevier) Journal, March 2002. Dr. Xinbing Wang

Key technologies that enable sensor networks: Micro electro-mechanical systems (MEMS) Wireless communications Digital electronics Dr. Xinbing Wang

Sensor Network Concepts Sensors nodes are very close to each other Sensor nodes have local processing capability Sensor nodes can be randomly and rapidly deployed even in places inaccessible for humans Sensor nodes can organize themselves to communicate with an access point Sensor nodes can collaboratively work Dr. Xinbing Wang

Location Finding System Sensor Node Hardware Power Unit Power Generator Sensor ADC Processor Memory Transceiver Location Finding System Mobilizer Small Low power Low bit rate High density Low cost (dispensable) Autonomous Adaptive SENSING UNIT PROCESSING UNIT Dr. Xinbing Wang

Berkeley Motes Dr. Xinbing Wang

Specifications of the Mote Processor/Radio Board MPR300CB Remarks Speed 4 MHz Flash 128K bytes SRAM 4K bytes EEPROM Radio Frequency 916MHz or 433MHz ISM Band Data Rate 40 Kbits/Sec Max Power 0.75 mW Radio Range 100 feet Programmable 2 x AA batteries Dr. Xinbing Wang

Examples of Sensors UCLA: WINS Rockwell: WINS UC Berkeley: Smart Dust UC Berkeley: COTS Dust UC Berkeley: Smart Dust UCLA: WINS JPL: Sensor Webs Rockwell: WINS Dr. Xinbing Wang

Sensor Networks Applications Sensors can monitor ambient conditions including: Temperature Humidity Vehicular movement Lightning condition Pressure Soil makeup Noise levels The presence or absence of certain kinds of objects Mechanical stress levels on attached objects, and Current characteristics (speed, direction, size) of an object Dr. Xinbing Wang

Sensor Networks Applications (2) Sensors can also be used for : Sensing Event detection Event identification Location sensing Local control of actuators Dr. Xinbing Wang

Sensor Networks Military Applications Command, control, communications, computing, intelligence, surveillance, reconnaissance, targeting (C4SRT) Monitoring friendly forces, equipment and ammunition Battlefield surveillance Reconnaissance of opposing forces and terrain Targeting Battle damage assessment Nuclear, biological and chemical (NBC) attack detection and reconnaissance Dr. Xinbing Wang

Sensor Networks Applications (2) Sensors can also be used for : Sensing Event detection Event identification Location sensing Local control of actuators Dr. Xinbing Wang

Factors Influencing Sensor Network Design A. Fault Tolerance (Reliability) B. Scalability C. Production Costs D. Hardware Constraints E. Sensor Network Topology F. Operating Environment G. Transmission Media H. Power Consumption Dr. Xinbing Wang

A. Fault Tolerance (Reliability) Sensor nodes may fail or be blocked due to lack of power have physical damage, or environmental interference. The failure of sensor nodes should not affect the overall task of the sensor network. This is called RELIABILITY or FAULT TOLERANCE, i.e., ability to sustain sensor network functionality without any interruption Dr. Xinbing Wang

Reliability (Fault Tolerance) of a sensor node is modeled: i.e., by Poisson distribution, to capture the probability of not having a failure within the time interval (0,t) with lambda_k is the failure rate of the sensor node k and t is the time period. G. Hoblos, M. Staroswiecki, and A. Aitouche, “Optimal Design of Fault Tolerant Sensor Networks,” IEEE International Conference on Control Applications, pp. 467-472, Anchorage, AK, September 2000. Dr. Xinbing Wang

Fault Tolerance (3) Reliability (Fault Tolerance) of a broadcast range with N sensor nodes is calculated from: Dr. Xinbing Wang

Fault Tolerance (4) EXAMPLE: How many sensor nodes are needed within a broadcast radius (range) to have 99% fault tolerated network? Assuming all sensors within the radio range have same reliability, prev. equation becomes Drop t and substitute f = (1 – R). o.99 = 1 – fN  N = 2 Dr. Xinbing Wang

Fault Tolerance (5) REMARK: 1. Protocols and algorithms may be designed to address the level of fault tolerance required by sensor networks. 2. If the environment has little interference, then the requirements can be more relaxed. Dr. Xinbing Wang

Factors Influencing Sensor Network Design  A. Fault Tolerance (Reliability) B. Scalability C. Production Costs D. Hardware Constraints E. Sensor Network Topology F. Operating Environment G. Transmission Media H. Power Consumption  Dr. Xinbing Wang

B. Scalability The number of sensor nodes may reach millions in studying a field/application The density of sensor nodes can range from few to several hundreds in a region (cluster) which can be less than 10m in diameter. Dr. Xinbing Wang

Scalability (2) The Sensor Node Density: i.e., the number of expected nodes within the radio range R where N is the number of scattered sensor nodes in region A and R is the radio transmission range. Basically:  is the number of sensor nodes within the transmission radius of each sensor node in region A. The number of sensor nodes in a region is used to indicate the node density depends on the application. Dr. Xinbing Wang

EXAMPLE: Scalability (3) Use the eq. on the previous slide Assume sensor nodes are evenly distributed in the sensor field, determine the node density if 200 sensor nodes are deployed in a 50x50 m2 region where each sensor node has a broadcast radius of 5 m. Use the eq. on the previous slide  (R) = (200 * * 52 )/(50*50) = 2 *  Dr. Xinbing Wang

Example -- Node Distribution Dr. Xinbing Wang

Scalability (4) -- Network Configuration dnei  Expected distance to the nearest neighbor, may or may not be communicating neighbor. dhop  Expected distance to the next hop, i.e., distance to communicating neighbor. dhop>=dnei Assuming that connection establishment is equally likely with any node within the radio range R of the given node, the expected hop distance is: Sink node dhop = 2R/3 Radio Range R e.g., R=20m  13.33m dnei dhop Sensor nodes Dr. Xinbing Wang

Scalability (5) -- Examples Machine Diagnosis Application: less than 300 sensor nodes in a 5 m x 5 m region. Vehicle Tracking Application: Around 10 sensor nodes per cluster/region. Home Application: 2 dozens or more. Habitat Monitoring Application: Range from 25 to 100 nodes/cluster Personal Applications: Ranges from 100s to 1000s, e.g., clothing, eye glasses, shoes, watch, jewelry. Dr. Xinbing Wang

Factors Influencing Sensor Network Design  A. Fault Tolerance (Reliability) B. Scalability C. Production Costs D. Hardware Constraints E. Sensor Network Topology F. Operating Environment G. Transmission Media H. Power Consumption   Dr. Xinbing Wang