Network Protocol Stack-Wireless Networking-Lecture 01 Slides-Electrical and Computer Engineering, Slides of Wireless Networking

Download Network Protocol Stack-Wireless Networking-Lecture 01 Slides-Electrical and Computer Engineering and more Slides Wireless Networking in PDF only on Docsity! ECE 586 Advanced Topics: Wireless Networking http://www.ece.rochester.edu/courses/ECE586 Spring 2005 TR 2-3:15, CSB 523 Wendi Heinzelman OH: T 3:30-4:30 Hopeman 307 wheinzel@ece.rochester.edu Class information (1) Prerequisites: Permission of instructor Course Description This course will cover the latest research in the area of wireless networking, concentrating mainly on mobile ad hoc and sensor networks. Topics will include media access control, routing, flow control and cross-layer architectures. Issues such as quality of service (QoS), energy conservation, reliability and mobility management will be discussed. Students will be required to complete a semester-long research project related to the theme of this course. Course outline (tentative) Sensor management2/24Thurs13 Localization3/1Tues14 MAC2/22Tues12 Routing2/17Thurs11 Architectures2/15Tues10 Sensor networks: intro2/10Thurs9 QoS2/8Tues8 MAC2/3Thurs7 Routing2/1Tues6 Ad hoc networks: intro1/27Thurs5 802.111/25Tues4 MAC protocols (cont.)1/20Thurs3 MAC protocols1/18Tues2 Intro to wireless networking: network architectures1/13Thurs1 TopicDateDayLecture # Network protocol stack Application Transport Network Data-link Physical Source coding Packet re-ordering, congestion control (e.g., TCP) Routing (e.g., IP) Error correction, MAC, encryption, MUX Modulation, power control, filtering, spreading Provides abstraction when designing layers We'll focus on MAC, Network, Transport and Cross- layer designs What is wireless communication? Any form of communication that does not require the transmitter and receiver to be in physical contact Electromagnetic wave propagated through free-space Radar, RF, Microwave, IR, Optical Simplex: one-way communication (e.g., radio, TV) Half-duplex: two-way communication but not simultaneous (e.g., push-to-talk radios) Full-duplex: two-way communication (e.g., cellular phones) Frequency-division duplex (FDD) Time-division duplex (TDD): simulated full-duplex How does mobility affect… Hardware Lighter More robust Lower power (battery operation) Wireless communication Time-varying channels Network protocols Name/address/location changes Delay changes Error rate changes Fidelity High fidelity may not be possible How does mobility affect… Security Lighter-weight algorithms Endpoint authentication harder Devices more vulnerable Performance Network, CPU all constrained Delay and delay variability Operating systems New resources to track and manage: energy Applications Name changes Changes in connectivity Changes in quality of resources People Introduces new complexities, failures, devices Example changes Addresses Phone numbers, IP addresses Network performance Bandwidth, delay, bit error rates, cost, connectivity Network interfaces WiFi, Ethernet Between applications Different interfaces over phone & laptop Within applications Loss of bandwidth triggers change from color to B&W Available resources Files, printers, displays, power, even routing Why is wireless different than wired? Noisy, time-varying channel BER varies by orders of magnitude Environmental conditions affect transmission Shared medium Other users create interference Must develop ways to share the channel Bandwidth is limited FCC determines how spectrum is allocated ISM band for unlicensed use (902-928 MHz, 2.4-2.5 GHz and 5.725-5.875 GHz) Requires intelligent SP and comm. to make efficient use of limited bandwidth in error-prone environment Why is wireless different than wired? Major differences due to broadcast nature of wireless communication Transmitted signals can be received by an arbitrary (and perhaps unknown) number of other users Cannot guarantee a link from every transmitting node to every intended receiving node Each transmitted message utilizes scares resources (BW) Need to provide means for fair and efficient utilization of available bandwidth among transmitting nodes Transmitted signal power important parameter Require enough signal power to reach destination node Want to limit signal power to minimize interference and max battery life Network topologies Types of network topologies Centralized De-centralized (peer-to-peer) Hybrid Centralized (hub-and-spoke) topology Communication from one node to another goes through hub (base station) Hub station controls nodes and monitors transmissions from each node Hub manages access by nodes to network’s allocated bandwidth Configuration for cellular systems and many WLAN networks Centralized topology (cont.) Disadvantages Single point of failure Delay due to multiple transmit/receive operations Cannot deal with unpredictable propagation environments Cannot cover wide areas where connections exceed range of single link Not suitable for ad-hoc networks Requires significant infrastructure setup Fully connected peer-to-peer Advantages No single point of failure No store-and-forward delay No routing so complexity of nodes reduced Can provide a node that is a gateway to backbone network Disadvantages Performance degradation in large networks Near-far problem Transmitters operating at high power levels (to reach far station) will interfere with unintended receivers in close proximity Multi-hop peer-to-peer Advantages Power efficiency if Tx power dominates over Rx power Only solution if no infrastructure available Widely used in military applications Gaining popularity in other types of wireless networks Ad hoc networks Sensor networks Disadvantages Complex algorithms for efficient message routing and control Multiple store-and-forwards increase delay for users separated by multiple hops Overhead to set up efficient routes No central timing or power control authority MANETs (cont.) Mobile nodes have limited communication range Reduces battery drain Enables spatial reuse of limited bandwidth increased network capacity To connect all nodes in the network, each node is a Packet source Packet sink Router Nodes must route packets for other nodes to keep the network fully connected In MANETs, a big problem is how to determine where a destination node is located relative to a sending node MANETs (cont.) Route-finding is a current area of much research Want to determine an “optimal” way to find “optimal” routes Dynamic links Broken links must be updated when a node moves out of communication range with another node New links must be formed when a node moves into communication range with another node Based on this new information, routes must be modified Frequency of route changes a function of node mobility Issues in MANETs Routing performance Routes change over time due to node mobility Would like to avoid long delays when sending packets But would like to avoid lots of route maintenance overhead Want as many participating nodes as possible for greater aggregate throughput, shorter paths, and smaller chance of partition MAC Broadcast communication channel Neighbor nodes change over time Nodes sleep to reduce energy drain No coordination/cooperation among nodes WSNs (cont.) Hundreds or thousands of nodes scattered throughout an environment New wireless networking paradigm Requires autonomous operation Highly dynamic environments Sensor nodes added/fail Events in the environment Distributed computation and communication protocols required Microsensor network applications Home security Machine failure diagnosis Chemical/biological detection Medical monitoring Surveillance and reconnaissance Animal/plant monitoring (e.g., for research) WSNs (cont.) Networking sensors enables Extended range of sensing improved quality Fault tolerance due to redundancy in data from different sensors Distributed processing of large amounts of sensor data Scalability: quality can be traded for system lifetime “Team-work”: nodes can help each perform a larger sensing task MANETs vs. WSNs Data-centricAddress-centric Very constrained energy and bandwidth Constrained energy and bandwidth CooperativeCompetitive Application-specific QoSQoS: delay, etc Typically immobileTypically mobile Large-scaleSmall-scale Require self-configurationRequire self-configuration Unreliable communicationUnreliable communication WSNsMANETs