The Basics of Wireless Communication. Octav Chipara

Size: px
Start display at page:

Download "The Basics of Wireless Communication. Octav Chipara"

Transcription

1 The asics of Wireless ommunication Octav hipara

2 genda hannel model: the protocol model High-level media access TM, SM hidden/exposed terminal problems WLN Fundamentals of routing proactive on-demand 2

3 hannel models hannel models - document assumptions of wireless properties the basis upon which we build and analyze network protocols good model is one that is simple - reason effectively about the properties of protocols accurate - capture prevalent properties of wireless channels these requirements are often conflicting Must provide insight into fundamental problems media access routing congestion Today, simple channel model..., next lecture more realistic models 3

4 Protocol model Network is modeled as a graph vertices - all nodes in a graph edges - connect nodes that may communicate Properties: captures connectivity information packet collisions (collisions happen only at the receiver) radios are half-duplex 4

5 Protocol model Network is modeled as a graph vertices - all nodes in a graph edges - connect nodes that may communicate Properties: captures connectivity information packet collisions (collisions happen only at the receiver) radios are half-duplex 4

6 Protocol model Network is modeled as a graph vertices - all nodes in a graph edges - connect nodes that may communicate Properties: captures connectivity information packet collisions (collisions happen only at the receiver) radios are half-duplex 4

7 Media ccess and ontrol (M) Problem: multiple nodes want to transmit concurrently nodes transmitting concurrently packet collisions Metrics for characterizing M performance throughput - number of packets delivered per second latency - time to deliver a packet energy efficiency - energy consumed for tx and rx fairness - each node gets its fair share of the channel flexibility - how does the M handle changes in workload pproaches SM - arrier Sense Multiple ccess TM - Time ivision Multiple ccess 5

8 SM SM - arrier Sense Multiple ccess pproach: 1: node will attempt to transmit after a random delay t W 2: check if channel is available free perform packet transmission busy W = W * 2, go to step 1 Notes: nodes operate independently! the underlying performance is highly dependent on selecting W W - reflects the expected number of contenders for the channel W increases exponentially [the rate depends on protocol] assumption: the sender can accurately check if channel is free/busy usually holds because: receiver sensibility << channel quality required for communication 6

9 SM SM - arrier Sense Multiple ccess pproach: 1: node will attempt to transmit after a random delay t W 2: check if channel is available free perform packet transmission busy W = W * 2, go to step 1 Notes: nodes operate independently! the underlying performance is highly dependent on selecting W W - reflects the expected number of contenders for the channel W increases exponentially [the rate depends on protocol] assumption: the sender can accurately check if channel is free/busy usually holds because: receiver sensibility << channel quality required for communication 6

10 Signal propagation ranges Transmission range communication possible low error rate etection range detection of the signal possible no communication possible Interference range signal may not be detected signal adds to the background noise sender transmission detection interference distance 7

11 TM TM - Time ivision Multiple ccess pproach: 1: construct a frame in which each node gets a slot to transmit F - frame size, fn - slot in which node n is assigned to transmit 2: a node n will transmit at time (t mod F) = fn Notes: time synchronization is required frame construction requires a global agreement among nodes underlying performance depends on matching a node s workload demand with its slot allocations hard to do due to dynamic workloads and channel properties assumption: only one successful transmission per slot 8

12 TM TM - Time ivision Multiple ccess pproach: 1: construct a frame in which each node gets a slot to transmit F - frame size, fn - slot in which node n is assigned to transmit 2: a node n will transmit at time (t mod F) = fn Notes: time synchronization is required frame construction requires a global agreement among nodes underlying performance depends on matching a node s workload demand with its slot allocations hard to do due to dynamic workloads and channel properties assumption: only one successful transmission per slot 8

13 Single-hop vs. multiple hops Single-hop networks both SM and TM protocols are easy to implement Multi-hop networks important challenges arise due to asymmetrical views of the networks hidden-terminal problem exposed-terminal problem 9

14 Hidden terminal problem Node and are hidden (edge () is not in the graph) they cannot sense their packet transmissions onsequences for M protocols SM protocols will never increase W TM protocols will have to agree on a frame over multiple hops 10

15 Hidden terminal problem Node and are hidden (edge () is not in the graph) they cannot sense their packet transmissions onsequences for M protocols SM protocols will never increase W TM protocols will have to agree on a frame over multiple hops 10

16 Hidden terminal problem undetected collisions Node and are hidden (edge () is not in the graph) they cannot sense their packet transmissions onsequences for M protocols SM protocols will never increase W TM protocols will have to agree on a frame over multiple hops 10

17 Exposed terminal problem Node and can communicate () and () can occur currently (collisions at receivers) onsequences for M protocols SM will increase W unnecessarily 11

18 Exposed terminal problem false positives Node and can communicate () and () can occur currently (collisions at receivers) onsequences for M protocols SM will increase W unnecessarily 11

19 RTS/TS a solution for SM protocols dd two additional messages to the TM protocol RTS - request to send TS - clear to send lgorithm node n wants to send packet to m transmit RTS(n, m) node a1, a2,..., an, m receive RTS(n, m) node m replies with TS(n, m) if its channel is free node b1, b2,..., bn, n receives TS(n, m) node n transmits the data packet The algorithm signals access requests over 2-hops 12

20 Hidden terminal problem 13

21 Hidden terminal problem send RTS(,) 13

22 Hidden terminal problem recv RTS(,) send RTS(,) 13

23 Hidden terminal problem recv RTS(,) send RTS(,) send TS(,) 13

24 Hidden terminal problem recv RTS(,) send RTS(,) recv TS(,) send TS(,) recv TS(,) 13

25 Exposed terminal problem send RTS(,) 14

26 Exposed terminal problem send RTS(,) send TS 14

27 Exposed terminal problem send RTS(,) ready to tx send TS 14

28 Exposed terminal problem send RTS(,) ready to tx send TS send RTS(, ) ready to tx 14

29 Exposed terminal problem send RTS(,) ready to tx send TS send RTS(, ) ready to tx send TS ready to tx 14

30 Exposed terminal problem send RTS(,) ready to tx send TS send RTS(, ) ready to tx send TS ready to tx ready to tx 14

31 WLN technology Protocol soup: Local wireless networks WLN WiFi a h i/e/ /w b g Goals: seamless operation leverage on existing wired infrastructure low-power operation on stations Two architectures: infrastructure + ad-hoc 15

32 802.11: rchitecture of an infrastructure network ST 1 ESS SS LN ccess Point istribution System SS 2 ccess Point 802.x LN Portal ST LN ST 3 Station (ST) terminal with wireless access mechanisms to contact the access point asic Service Set (SS) group of stations using the same radio frequency ccess Point station integrated into the wireless LN and the distribution system Portal bridge to other (wired) networks istribution System interconnection network to/form one logical network 16

33 802.11: rchitecture of an ad-hoc network SS 1 ST LN ST 3 irect communication within a limited range Station (ST): terminal with access mechanisms to the wireless medium Independent asic Service Set (ISS): group of stations using the same radio frequency When no direct link is feasible between two station, a third station may act as a relay (multihop communications) ST LN 17

34 802.11b - istributed oordination Function Exponential back-off hosen for uniformly from (0, W-1), W increase exponentially with the number of failed attempts Wmin minimum contention window Wmax = 2 m Wmin maximum contention window 18

35 802.11b - istributed oordination Function Message resent when the backoff counter reaches zero ackoff counter decremented only when the channel is idle ackoff counter is reset to zero after a successful transmission 19

36 Routing Routing consists of two fundamental steps Forwarding packets to the next hop (from an input interface to an output interface in a traditional wired network) etermining how to forward packets (building a routing table or specifying a route) Forwarding packets is easy, but knowing where to forward packets (especially efficiently) is hard Reach the destination Minimize the number of hops (path length) Minimize delay Minimize packet loss Minimize cost 20

37 Routing ecision Point Source routing Sender determines a route and specifies it in the packet header Hop-by-hop (datagram) routing routing decision is made at each forwarding point (at each router) Standard routing scheme for IP Virtual circuit routing etermine and configure a path prior to sending first packet Used in TM (and analogous to voice telephone system) 21

38 Routing Table routing table contains information to determine how to forward packets Source routing: Routing table is used to determine route to the destination to be specified in the packet Hop-by-hop routing: Routing table is used to determine the next hop for a given destination Virtual circuit routing: Routing table used to determine path to configure through the network 22

39 Routing pproaches Reactive (On-demand) protocols discover routes when needed source-initiated route discovery Proactive protocols traditional distributed shortest-path protocols based on periodic updates. High routing overhead Tradeoff state maintenance traffic vs. route discovery traffic route via maintained route vs. delay for route discovery

40 istance Vector lgorithms (1) istance of each link in the network is a metric that is to be minimized each link may have distance 1 to minimize hop count algorithm attempts to minimize distance The routing table at each node specifies the next hop for each destination specifies the distance to that destination Neighbors can exchange routing table information to find a route (or a better route) to a destination 24

41 istance Vector lgorithms (2) est Next Metric est Next Metric est Next Metric est Next Metric

42 istance Vector lgorithms (3) Node will learn of Node s shorter path to Node and update its routing table est Next Metric est Next Metric

43 Reactive Routing Source initiated Source floods the network with a route request packet when a route is required to a destination flood is propagated outwards from the source pure flooding = every node transmits the request only once estination replies to request reply uses reversed path of route request sets up the forward path 27

44 Route iscovery RREQ FORMT G Initiator Initiator seq # estination I Partial Route E H -- Route Request (RREQ) F -- Route Reply (RREP) 28

45 Route iscovery RREQ FORMT G Initiator Initiator seq # estination I Partial Route -- E H Route Request (RREQ) F -- Route Reply (RREP) 28

46 Route iscovery RREQ FORMT - G Initiator Initiator seq # estination I Partial Route -- E H Route Request (RREQ) F -- Route Reply (RREP) 28

47 Route iscovery RREQ FORMT - G Initiator Initiator seq # estination I Partial Route -- E H Route Request (RREQ) - -- F Route Reply (RREP) 28

48 Route iscovery RREQ FORMT - G Initiator Initiator seq # estination I Partial Route --E -- - E --E --E H Route Request (RREQ) -- F Route Reply (RREP) 28

49 Route iscovery RREQ FORMT - -- G Initiator Initiator seq # estination I Partial Route --E -- - E --E --E H Route Request (RREQ) -- F Route Reply (RREP) 28

50 Route iscovery RREQ FORMT - --E -- G --E-H Initiator Initiator seq # estination I Partial Route -- - E --E --E H Route Request (RREQ) -- F Route Reply (RREP) 28

51 Route iscovery RREQ FORMT ---G - ---G ---G --E -- G --E-H Initiator Initiator seq # estination I Partial Route -- - E --E --E H Route Request (RREQ) -- F Route Reply (RREP) 28

52 Route iscovery: at source need to send to G Lookup ache for route to G Start Route iscovery Protocol wait uffer packet ontinue normal processing yes no Route found? yes Write route in packet header Route iscovery finished Packet in buffer? no done Send packet to next-hop 29

53 Route iscovery: t an intermediate node ccept route request packet <src,id> in recent requests list? yes iscard route request no ppend myddr to partial route Store <src,id> in list no Host already in partial route no myddr =target Send route reply packet yes iscard route request roadcast packet done 30

54 Route iscovery Route Reply message containing path information is sent back to the source either by the destination, or intermediate nodes that have a route to the destination reverse the order of the route record, and include it in Route Reply. unicast, source routing Each node maintains a Route ache which records routes it has learned and overheard over time 31

55 Route Maintenance Route maintenance performed only while route is in use Error detection: monitors the validity of existing routes by passively listening to data packets transmitted at neighboring nodes When problem detected, send Route Error packet to original sender to perform new route discovery Host detects the error and the host it was attempting; Route Error is sent back to the sender the packet original src 32

MAC Layer Protocols for Sensor Networks

MAC Layer Protocols for Sensor Networks MAC Layer Protocols for Sensor Networks Leonardo Leiria Fernandes Compiled by C. Pham for educational purposes.background color has been modified in this presentation. Some slides were also added l Basic

More information

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols Link Layer: Introduction daptors ommunicating hosts and routers are nodes communication channels that connect nodes are links wired links wireless links LNs layer-2 packet is a frame, encapsulates datagram

More information

Part 4. Routing Protocols

Part 4. Routing Protocols Part 4. Routing Protocols 1. Routing for Mobile Ad hoc NETworks (MANETs) Routing in MANETs is difficult since mobility causes frequent network topology changes and requires more robust and flexible mechanisms

More information

CSE 123b Communications Software

CSE 123b Communications Software S 3b ommunications Software Spring 4 Lecture 6: Routing: Overview and istance Vector lgorithms Stefan Savage Some slides courtesy avid Wetherall dministrativa Homework up front I ll give out solutions

More information

Medium Access Control (MAC) Protocols

Medium Access Control (MAC) Protocols Medium ccess Control (MC) Protocols MC Protocols: a taxonomy Three broad classes: Channel Partitioning divide channel into smaller pieces (time slots, frequency, code) allocate piece to node for exclusive

More information

Ad-Hoc Networks. Manet: Mobile Ad-hoc Networking. Problems of Traditional Routing Algorithms. Traditional Routing Algorithms.

Ad-Hoc Networks. Manet: Mobile Ad-hoc Networking. Problems of Traditional Routing Algorithms. Traditional Routing Algorithms. d-oc Networks Standard Mobile IP needs an infrastructure ome gent/oreign gent in the fixed network NS, routing etc. are not designed for mobility Sometimes there is no (stable) infrastructure! Wireless

More information

Link Layer Services (more) Link Layer. LAN technologies. LAN Addresses and ARP. MAC Addresses and ARP. Last Course Review: Link Layer: Introduction

Link Layer Services (more) Link Layer. LAN technologies. LAN Addresses and ARP. MAC Addresses and ARP. Last Course Review: Link Layer: Introduction Last Course Review: Link Layer: Introduction Some terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are links wired links wireless links

More information

Energy-Efficient Channel Access Protocols

Energy-Efficient Channel Access Protocols UNIVERSITY OF CALIFORNIA SANTA CRUZ Energy-Efficient Channel Access Protocols Venkatesh Rajendran venkat@soe.ucsc.edu Introduction Sensor networks are a special class of multihop wireless networks. Ad-hoc

More information

Stuff. CSMA/CD efficiency. Ethernet uses CSMA/CD. Ethernet CSMA/CD algorithm. Taking Turns MAC protocols. Ethernet s CSMA/CD (more) efficiency =

Stuff. CSMA/CD efficiency. Ethernet uses CSMA/CD. Ethernet CSMA/CD algorithm. Taking Turns MAC protocols. Ethernet s CSMA/CD (more) efficiency = Stuff Ethernet s CSM/CD (more) Project phase III out, due pril 25. Guest lecturer next Tues: Vern Paxson on Network Security. Lecture today: Finish multiple access Link layer addressing Hub vs Switch Jam

More information

On-Demand Routing Protocols

On-Demand Routing Protocols On-Demand Routing Protocols Routes are established on demand as requested by the source Only the active routes are maintained by each node Channel/Memory overhead is minimized Two leading methods for route

More information

Shared Access Networks

Shared Access Networks Shared ccess Networks Outline us (Ethernet 802.2/3) Token ring Wireless (802.11) 1 Ethernet Overview The most successful Local rea Networks andwidth: 10Mbps, 100Mbps (Fast), 1Gbps void Simultaneous on

More information

Dynamic Source Routing (DSR) Protocol

Dynamic Source Routing (DSR) Protocol Dynamic Source Routing (DSR) Protocol S: 647 dvanced Topics in Wireless Networks Drs. aruch werbuch & mitabh Mishra Department of omputer Science Johns Hopkins 5-1 Reading hapter 5 d Hoc Networking, Perkins,

More information

Collision in Star Topology: Case 3. IEEE MAC Frame Format

Collision in Star Topology: Case 3. IEEE MAC Frame Format Collision in Star Topology: Case 3 A and D transmitting Collision presence signal E A B C D 1 IEEE 802.3 MAC Frame Format Figure 16.3 Ethernet frame format differs that Length field is used for other purposes,

More information

Advanced Computer Networks

Advanced Computer Networks Introduction to Mobile Ad hoc Networks (MANETs) Advanced Computer Networks Outline Ad hoc networks Differences to other networks Applications Research areas Routing Other research areas Enabling Technologies

More information

Review of Networking Concepts. Part 1: Switching Networks

Review of Networking Concepts. Part 1: Switching Networks Review of Networking oncepts Part 1: Switching Networks The first few lectures of this course cover basic, but important, concepts of computer networking Summary of Topics Taxonomy of switching networks

More information

History. Outline. Multiple Access protocols. Ideal Multiple Access Protocol. Multiple Access Links and Protocols. MAC Protocols: a taxonomy

History. Outline. Multiple Access protocols. Ideal Multiple Access Protocol. Multiple Access Links and Protocols. MAC Protocols: a taxonomy Outline History of ad-hoc Ad-hoc vs cellular Application Issues MAC protocols for ad-hoc Example ad-hoc MAC protocol: MACAW History Darius I, Persia ca 500 B.C. ALOHAnet, 1970s DARPA PRNet (ALOHA and CSMA),

More information

Lectures The Medium Access Control Sub-Layer

Lectures The Medium Access Control Sub-Layer Computer Communications Lectures 11-13 The Medium Access Control Sub-Layer The Channel Allocation Problem Consider a broadcast channel (sometimes also called multi-access or random access channel) How

More information

Wireless LAN (IEEE class of protocol suite)

Wireless LAN (IEEE class of protocol suite) Wireless LAN (IEEE 802.11 class of protocol suite) In these notes, I will explain the MAC protocols used in constructing wireless LANs using the IEEE 802.11 class of protocol suites. Specific protocols,

More information

Ethernet uses CSMA/CD

Ethernet uses CSMA/CD Stuff Project phase III out, due April 25. Guest lecturer next Tues: Vern Paxson on Network Security. Lecture today: Finish multiple access Link layer addressing Hub vs Switch DataLink Layer 1 Ethernet

More information

Kenneth Holter. 23rd April 2005

Kenneth Holter. 23rd April 2005 Comparing ODV and OLSR Kenneth Holter 23rd pril 2005 1 Contents 1 Introduction 4 2 Wireless networks 5 2.1 The OSI reference model...................... 6 2.2 Radio technology..........................

More information

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III CS: 647 Advanced Topics in Wireless Networks Drs. Baruch Awerbuch & Amitabh Mishra Department of Computer Science Johns Hopkins

More information

Outline Computer Networking. Reminder: Datalink Functions. Datalink Architectures Lecture 25 CSMA Protocols Peter Steenkiste

Outline Computer Networking. Reminder: Datalink Functions. Datalink Architectures Lecture 25 CSMA Protocols Peter Steenkiste Outline 15-441 15 441 15-641 Computer Networking Lecture 25 CSM Protocols Peter Steenkiste Ethernet Wireless networking Wireless Ethernet loha 802.11 Fall 2016 www.cs.cmu.edu/~prs/15-441-f16 2 Reminder:

More information

CHAPTER 5 IMPLEMENTATION OF NEURO FUZZY SCHEDULING BASED CONNECTED DOMINATING SET IN WIRELESS MESH NETWORK

CHAPTER 5 IMPLEMENTATION OF NEURO FUZZY SCHEDULING BASED CONNECTED DOMINATING SET IN WIRELESS MESH NETWORK 63 CHAPTER 5 IMPLEMENTATION OF NEURO FUZZY SCHEDULING BASED CONNECTED DOMINATING SET IN WIRELESS MESH NETWORK 5.1 Introduction Neuro fuzzy logic method is taken in wireless mesh network to increase a network

More information

Routing Protocols. AODV: reactive routing protocol OLSR: proactive routing protocol

Routing Protocols. AODV: reactive routing protocol OLSR: proactive routing protocol Routing Protocols Setting all routes in large size networks is an unfeasible solution There exists several routing algorithm developed for Linux-based OSs (BGP, OSPF, OLSR, AODV, etc.) In this seminary

More information

EN FA11 Network Embedded Systems/Sensor Networks Week 4: Medium Access Control. Marcus Chang, Andreas CS JHU

EN FA11 Network Embedded Systems/Sensor Networks Week 4: Medium Access Control. Marcus Chang, Andreas CS JHU EN.600.450.01.FA11 Network Embedded Systems/Sensor Networks Week 4: Medium Access Control Marcus Chang, Andreas Terzis @ CS JHU 1 Outline Background in MAC protocols Role and features of MAC protocols

More information

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - II

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - II Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - II CS: 647 Advanced Topics in Wireless Networks Drs. Baruch Awerbuch & Amitabh Mishra Department of Computer Science Johns Hopkins University

More information

CSMA/CA. Information Networks p. 1

CSMA/CA. Information Networks p. 1 Information Networks p. 1 CSMA/CA IEEE 802.11 standard for WLAN defines a distributed coordination function (DCF) for sharing access to the medium based on the CSMA/CA protocol Collision detection is not

More information

Wireless networks. Routing: DSR, AODV

Wireless networks. Routing: DSR, AODV Wireless networks Routing: DSR, AODV 1 Routing in Ad Hoc Networks Goals Adapt quickly to topology changes No centralization Loop free routing Load balancing among different routes in case of congestion

More information

CS 294-7: Routing in Packet Radio Networks. Professor Randy H. Katz CS Division University of California, Berkeley Berkeley, CA

CS 294-7: Routing in Packet Radio Networks. Professor Randy H. Katz CS Division University of California, Berkeley Berkeley, CA CS 294-7: Routing in Packet Radio Networks Professor Randy H. Katz CS Division University of California, Berkeley Berkeley, CA 94720-1776 1996 1 Packet Radio Network Schemes (ARPA PR Program) Passive Acknowledgments

More information

1. What is the capacity C of a channel with a bandwidth of 10,000 Hz and a signal to noise ratio of 100 (S/N=100) (3 points)

1. What is the capacity C of a channel with a bandwidth of 10,000 Hz and a signal to noise ratio of 100 (S/N=100) (3 points) CSE 4153 / 6153, Fall 2010, Midterm Name /Net ID 1. What is the capacity C of a channel with a bandwidth of 10,000 Hz and a signal to noise ratio of 100 (S/N=100) (3 points) C = B log2(1+s/n) = 10000.

More information

Final Exam for ECE374 05/05/11 Solution!!

Final Exam for ECE374 05/05/11 Solution!! ECE374: Final Exam 1 Final Exam for ECE374 05/05/11 Solution!! Note: In all written assignments, please show as much of your work as you can. Even if you get a wrong answer, you can get partial credit

More information

Wireless Medium Access. David Holmer

Wireless Medium Access. David Holmer Wireless Medium Access David Holmer dholmer@jhu.edu Multi-transmitter Interference Problem Similar to multi-path or noise Two transmitting stations will constructively/destructively interfere with each

More information

Medium Access Control (MAC) Protocols

Medium Access Control (MAC) Protocols Medium ccess Control (MC) Protocols MC Protocols: a taxonomy Three broad classes: Channel Partitioning divide channel into smaller pieces (time slots, frequency, code) allocate piece to node for exclusive

More information

Datalink Functions. Link Flow Control and Error Recovery. Outline

Datalink Functions. Link Flow Control and Error Recovery. Outline 8-345: Introduction to Telecommunication Networks Lectures 6: Datalink layer Error ontrol, Ethernet Peter Steenkiste Spring 05 www.cs.cmu.edu/~prs/nets-ece Datalink Functions Framing: encapsulating a network

More information

CS413 Computer Networks Final Exam Solution

CS413 Computer Networks Final Exam Solution CS413 Computer Networks Final Exam Solution December 21, 2005 Student ID: Name: Problem No. Assigned Marks Your Marks 1 20 2 7 3 6 4 6 5 7 6 10 7 7 8 10 9 7 Total 80 Note: You may write the answers in

More information

Last class. Basic classification of ad hoc routing. DSR: dynamic source routing

Last class. Basic classification of ad hoc routing. DSR: dynamic source routing DSDV & AODV 2/27/06 Last class Basic classification of ad hoc routing Proactive Reactive, on-demand Geographical routing Hierarchical routing DSR: dynamic source routing Reactive protocol Route discovery

More information

CS 43: Computer Networks Media Access. Kevin Webb Swarthmore College December 1, 2015

CS 43: Computer Networks Media Access. Kevin Webb Swarthmore College December 1, 2015 CS 43: Computer Networks Media Access Kevin Webb Swarthmore College December 1, 2015 Multiple Access Links & Protocols Two classes of links : point-to-point dial-up access link between Ethernet switch,

More information

Chapter 5: Link layer

Chapter 5: Link layer Chapter 5: Link layer our goals: understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing local area networks: Ethernet,

More information

A Comparison Study of Qos Using Different Routing Algorithms In Mobile Ad Hoc Networks

A Comparison Study of Qos Using Different Routing Algorithms In Mobile Ad Hoc Networks A Comparison Study of Qos Using Different Routing Algorithms In Mobile Ad Hoc Networks T.Chandrasekhar 1, J.S.Chakravarthi 2, K.Sravya 3 Professor, Dept. of Electronics and Communication Engg., GIET Engg.

More information

Lecture 3.1 : An Overview of the DSR Protocol. Lecture 3.2 : Routing Details and Performance of the DSR Protocol

Lecture 3.1 : An Overview of the DSR Protocol. Lecture 3.2 : Routing Details and Performance of the DSR Protocol Lecture 3 : The Dynamic Source Routing Protocol Lecture 3.1 : An Overview of the DSR Protocol. Lecture 3.2 : Routing Details and Performance of the DSR Protocol Dynamic Source Routing (DSR) Protocol Mobile

More information

MAC Addresses and ARP. Mac Addressing, Ethernet, and Interconnections. LAN Addresses and ARP. LAN Address (more) ARP protocol: Same LAN (network)

MAC Addresses and ARP. Mac Addressing, Ethernet, and Interconnections. LAN Addresses and ARP. LAN Address (more) ARP protocol: Same LAN (network) M ddresses and RP Mac ddressing, thernet, and Interconnections 32-bit IP address: network-layer address used to get datagram to destination IP subnet M (or LN or physical or thernet) address: used to get

More information

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc

Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc (International Journal of Computer Science & Management Studies) Vol. 17, Issue 01 Performance Evaluation of AODV, OLSR Routing Protocol in VOIP Over Ad Hoc Dr. Khalid Hamid Bilal Khartoum, Sudan dr.khalidbilal@hotmail.com

More information

EEC 189Q Medium Access Sublayer Computer Networks Reading: Chapter Communication Links Remarks on MAC Sublayer

EEC 189Q Medium Access Sublayer Computer Networks Reading: Chapter Communication Links Remarks on MAC Sublayer EEC 189Q Computer Networks Medium Access Sublayer Medium Access Control (MAC) Random vs. controlled access Random Access Aloha, CSMA, CSMA/CD Network Data Link Physical Medium Access Sublayer Medium Access

More information

COMP9332 Network Routing & Switching

COMP9332 Network Routing & Switching COMP9332 Network Routing & Switching MANET Routing I (AODV) www.cse.unsw.edu.au/~cs9332 1 Previous lectures Routers are dedicated machines installed in the infrastructure High processing capacity High-bandwidth

More information

William Stallings Data and Computer Communications. Chapter 10 Packet Switching

William Stallings Data and Computer Communications. Chapter 10 Packet Switching William Stallings Data and Computer Communications Chapter 10 Packet Switching Principles Circuit switching designed for voice Resources dedicated to a particular call Much of the time a data connection

More information

William Stallings Data and Computer Communications. Chapter 10 Packet Switching

William Stallings Data and Computer Communications. Chapter 10 Packet Switching William Stallings Data and Computer Communications Chapter 10 Packet Switching Principles Circuit switching designed for voice Resources dedicated to a particular call Much of the time a data connection

More information

Both connections oriented and connectionless are techniques used in packet switching networks.

Both connections oriented and connectionless are techniques used in packet switching networks. 1. X.25 vs. Frame Relay Based on Functionality. Frame Relay implements that concept. The Frame Relay has separate logical channel for the call control. The multiplexing and logical connection takes place

More information

Behavior Analysis of TCP Traffic in Mobile Ad Hoc Network using Reactive Routing Protocols

Behavior Analysis of TCP Traffic in Mobile Ad Hoc Network using Reactive Routing Protocols Behavior Analysis of TCP Traffic in Mobile Ad Hoc Network using Reactive Routing Protocols Purvi N. Ramanuj Department of Computer Engineering L.D. College of Engineering Ahmedabad Hiteishi M. Diwanji

More information

The Link Layer and LANs

The Link Layer and LANs The Link Layer and LANs Raj Jain Washington University in Saint Louis Saint Louis, MO 63130 Jain@wustl.edu Audio/Video recordings of this lecture are available on-line at: http://www.cse.wustl.edu/~jain/cse473-11/

More information

Multiple Access Protocols for Link Layer. Multiple Access Protocols

Multiple Access Protocols for Link Layer. Multiple Access Protocols Multiple Access Protocols for Link Layer Multiple Access Protocols Single shared broadcast channel Two or more simultaneous transmissions by nodes: interference collision if node receives two or more signals

More information

6.1. Why do LANs tend to use broadcast networks? Why not use networks consisting of multiplexers and switches?

6.1. Why do LANs tend to use broadcast networks? Why not use networks consisting of multiplexers and switches? TUTORIAL 2 (EKT 332) 6.1. Why do LANs tend to use broadcast networks? Why not use networks consisting of multiplexers and switches? Why broadcast network? -The computers in a LAN are separated by a short

More information

Computer Networks Delhi Technological university Network Layer: Routing Instructor: Divya Sethia

Computer Networks Delhi Technological university Network Layer: Routing Instructor: Divya Sethia Computer Networks Delhi Technological university Network Layer: Routing Instructor: Divya Sethia Divyashikha Sethia (DTU) Objective Routing Algorithms Classification Shortest Path First Flooding Distance

More information

Star topology. Ethernet. Ethernet Frame Structure (more) Ethernet Frame Structure. Ethernet uses CSMA/CD. Unreliable, connectionless service

Star topology. Ethernet. Ethernet Frame Structure (more) Ethernet Frame Structure. Ethernet uses CSMA/CD. Unreliable, connectionless service thernet dominant wired LN technology: cheap $0 for 00Mbs! first widely used LN technology Simpler, cheaper than token LNs and TM Kept up with speed race: 0 Mbps 0 bps Star topology us topology popular

More information

Infrastructure Components: Hub & Repeater. Network Infrastructure. Switch: Realization. Infrastructure Components: Switch

Infrastructure Components: Hub & Repeater. Network Infrastructure. Switch: Realization. Infrastructure Components: Switch Network Infrastructure or building computer networks more complex than e.g. a short bus, some additional components are needed. They can be arranged hierarchically regarding their functionality: Repeater

More information

Advantages. Basic Operation of Packet Switching. Principles. Chapter 10 Packet Switching

Advantages. Basic Operation of Packet Switching. Principles. Chapter 10 Packet Switching Chapter 10 Packet Switching Packet Switching Principles Switching Techniques (Datagram, Virtual Circuit) Packet Size Comparison of Circuit Switching & Packet Switching Routing Principles Circuit switching

More information

Summary of MAC protocols. Medium Access Protocols. LAN Addresses and ARP. LAN technologies. LAN Addresses and ARP. LAN Address (more)

Summary of MAC protocols. Medium Access Protocols. LAN Addresses and ARP. LAN technologies. LAN Addresses and ARP. LAN Address (more) Summary of MAC protocols Medium Access Protocols What do you do with a shared media? Channel Partitioning, by time, frequency or code Time Division,Code Division, Frequency Division Random partitioning

More information

VTU-NPTEL-NMEICT Project

VTU-NPTEL-NMEICT Project Assignment Questions Module 1: Networks Introduction 1. Discuss the properties of a network. Module 3 & 4: Packetized File Transfer and Layering 2. Discuss the key design issues for layering in a network

More information

CS 457 Lecture 7 Ethernet and Wireless. Fall 2011

CS 457 Lecture 7 Ethernet and Wireless. Fall 2011 CS 457 Lecture 7 Ethernet and Wireless Fall 2011 Ethernet Uses CSMA/CD Carrier sense: wait for link to be idle Channel idle: start transmitting Channel busy: wait until idle Collision detection: listen

More information

XORs in the air: Practical Wireless Network Coding

XORs in the air: Practical Wireless Network Coding XORs in the air: Practical Wireless Network Coding Sachin Katti, Hariharan Rahul, Wenjun Hu, Dina Katabi, Muriel Medard, Jon Crowcroft SIGCOMM 06 Presented by Thangam Seenivasan 1 Problem Increase the

More information

CS 168 Discussion 12 - Final Review. Question 1: Short Answer

CS 168 Discussion 12 - Final Review. Question 1: Short Answer CS 168 Discussion 12 - Final Review Question 1: Short Answer A) Internet Principles We are faced with three basic design decisions: a) How to break the overall systems into modules b) Where these modules

More information

CS 640: Introduction to Computer Networks

CS 640: Introduction to Computer Networks S : Introduction to omputer Networks ditya kella Lecture - Intra-omain Routing rom previous lecture. Three Types of Switching abrics Switching Via a Memory irst generation routers looked like Ps Packet

More information

EECS 122. Spring University of California Berkeley

EECS 122. Spring University of California Berkeley EECS 122 Spring 2004 University of California Berkeley What are the basic differences between Circuit and Packet Switching? Understand Packet Switch network hierarchy: LAN, MAN, WAN What is the motivation

More information

Lectures 14: LAN technologies: Token Rings, Wireless LANs

Lectures 14: LAN technologies: Token Rings, Wireless LANs Lectures 14: LAN technologies: Token Rings, Wireless LANs Slide 1 Token rings Token rings were developed by IBM in early 1980 s IEEE Standard 802.5 Token: a bit sequence Token circulates around the ring

More information

Elements of a wireless network!

Elements of a wireless network! 1DT066" Distributed Information Systems" " Chapter 6! Wireless, WiFi and mobility! Adapted from: Computer Networking, Kurose/Ross! Elements of a wireless! infrastructure wireless hosts!! laptop, smartphone!!

More information

CS 640: Computer Networks. Error Coding. Parity. Page 1. Aditya Akella. Lecture 6 - Error/Flow Control & Intro to Switching and Medium Access Control

CS 640: Computer Networks. Error Coding. Parity. Page 1. Aditya Akella. Lecture 6 - Error/Flow Control & Intro to Switching and Medium Access Control CS 6: Computer Networks Aditya Akella Lecture 6 - Error/Flow Control & Intro to Switching and Medium Access Control Error Coding Transmission process may introduce errors into a message. Single bit errors

More information

Multicast. Lecture 14. Outline. Multicast Addresses. Multicast Routing. Multicast

Multicast. Lecture 14. Outline. Multicast Addresses. Multicast Routing. Multicast Lecture 14 Multicast Homework 5, due next Tuesday (October 23) Wireshark Project 3 posted, due (October 23) Programming Project 3 posted, (October 30) October 25 th Midterm exam review October 30 th Midterm

More information

WLAN, part 2. Contents

WLAN, part 2. Contents Contents IEEE 802.11 MAC layer operation Basic CSMA/CA operation Network Allocation Vector (NAV) Backoff Contention window Wireless medium access example Usage of RTS / CTS Basic operation When should

More information

CIRCUIT SWITCHING AND PACKET SWITCHING

CIRCUIT SWITCHING AND PACKET SWITCHING Islamic University Of Gaza Data Communication Faculty of Engineering Discussion Computer Department Chapter 10 Eng. Ahmed M. Ayash Date: 19/12/2012 Chapter 10 CIRCUIT SWITCHING AND PACKET SWITCHING Switched

More information

Network Layer (7): Unicast Routing

Network Layer (7): Unicast Routing Network Layer (7): Unicast Routing Required reading: Kurose 4.5 SE 4, Fall 06 Instructor: N. Vlajic . Introduction. Network Layer Protocols in the Internet 4. IPv4 4. IP ddressing and Subnetting 4. RP

More information

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs)

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs) CS6956: Wireless and Mobile Networks Lecture Notes: //05 IEEE 80. Wireless Local Area Networks (WLANs) CSMA/CD Carrier Sense Multi Access/Collision Detection detects collision and retransmits, no acknowledgement,

More information

Lecture 6. Wide Area Networks, Switching techniques. How to take several hops over a network Circuit switching concepts Packet switching concepts

Lecture 6. Wide Area Networks, Switching techniques. How to take several hops over a network Circuit switching concepts Packet switching concepts Data communication I Lecture 6 Wide Area Networks, Switching techniques Wide Area Networks Switching techniques How to take several hops over a network Circuit switching concepts Packet switching concepts

More information

CS263: Wireless Communications and Sensor Networks

CS263: Wireless Communications and Sensor Networks CS263: Wireless Communications and Sensor Networks Matt Welsh Lecture 4: Medium Access Control October 5, 2004 2004 Matt Welsh Harvard University 1 Today's Lecture Medium Access Control Schemes: FDMA TDMA

More information

An overview of soft real-time wireless communication for Sensor Networks. Marco Caccamo

An overview of soft real-time wireless communication for Sensor Networks. Marco Caccamo An overview of soft real-time wireless communication for Sensor Networks Marco Caccamo 1 Outline Wireless LANs background Enforce priorities with CSMA/CA access Speed routing protocol Real-time chains

More information

Communication Protocols and Internet Architectures Harvard University CSCI E-40

Communication Protocols and Internet Architectures Harvard University CSCI E-40 Communication Protocols and Internet Architectures Harvard University CSCI E-40 Homework Assignment #2 Solutions Total points: 24 Question 1) 5 points total 1a, 1b and 1c, Explain in detail what is meant

More information

Question Score 1 / / / 8 4 / 9.5 Total / 50.5

Question Score 1 / / / 8 4 / 9.5 Total / 50.5 NAME: Login name: Computer Science 461 Midterm Exam March 14, 2014 This test has five (5) questions. Put your login name on every page, and write out and sign the Honor Code pledge (in cursive) before

More information

Computer Networking

Computer Networking 15-441 Computer Networking Lecture 18 Datalink and LANs Goals Understand and services provided by the datalink layer and the the principles used to implement them. Understand the design principles and

More information

Lecture 2.1 : The Distributed Bellman-Ford Algorithm. Lecture 2.2 : The Destination Sequenced Distance Vector (DSDV) protocol

Lecture 2.1 : The Distributed Bellman-Ford Algorithm. Lecture 2.2 : The Destination Sequenced Distance Vector (DSDV) protocol Lecture 2 : The DSDV Protocol Lecture 2.1 : The Distributed Bellman-Ford Algorithm Lecture 2.2 : The Destination Sequenced Distance Vector (DSDV) protocol The Routing Problem S S D D The routing problem

More information

Lecture 12: Computer Networks Review

Lecture 12: Computer Networks Review Lecture : omputer s Review Yuan Xue Suppose you want to build a computer network. What technologies would serve as the underlying building blocks, what kind of software architecture would you design to

More information

06/02/ Local & Metropolitan Area Networks. Overview. Medium Access Sublayer (1) ACOE322

06/02/ Local & Metropolitan Area Networks. Overview. Medium Access Sublayer (1) ACOE322 1 Local & Metropolitan Area Networks ACOE322 Lecture 2 Medium Access Control and Logical Link Control 1 Overview The architecture of a LAN is best described in terms of a layering of protocols that organize

More information

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Chapter 5 Link Layer CPSC 335 Data Communication Systems Readings: 5.1, 5.3 David Nguyen Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Adapted from

More information

Ad Hoc On-Demand Distance Vector Routing (AODV) Diwakar Yagaysen Assistant Prof. CSE, BBDNITM, Lucknow

Ad Hoc On-Demand Distance Vector Routing (AODV) Diwakar Yagaysen Assistant Prof. CSE, BBDNITM, Lucknow Ad Hoc On-Demand Distance Vector Routing (AODV) Diwakar Yagaysen Assistant Prof. CSE, BBDNITM, Lucknow Unicasting The routing we have discussed so far is mainly point-topoint routing. A source node wants

More information

Wireless Mesh and Multi-Hop Relay Networks

Wireless Mesh and Multi-Hop Relay Networks Wireless Mesh and Multi-Hop Relay Networks Raj Jain Washington University in Saint Louis Saint Louis, MO 63130 Jain@cse.wustl.edu These slides are available on-line at: http://www.cse.wustl.edu/~jain/cse574-06/

More information

Communication Networks Chapter 5. Switching Technology

Communication Networks Chapter 5. Switching Technology Communication Networks Chapter 5. Switching Technology o Circuit Switching o Message Switching o Virtual Circuit / Virtual Connection o Datagram Recapitulation: Telecommunications Network LAN 1 Backbone

More information

Networking technologies and applications. Rolland Vida April 20, 2015

Networking technologies and applications. Rolland Vida April 20, 2015 Networking technologies and applications Rolland Vida IEEE 802.11 WLAN Wireless Local Area Network The most popular WLAN solution defined by the IEEE 802.11 standard Other solutions: HiperLAN, HomeRF What

More information

March 1996 doc.: IEEE P /49C Tutorial MAC Entity: MAC Basic Access Mechanism Privacy and Access Control

March 1996 doc.: IEEE P /49C Tutorial MAC Entity: MAC Basic Access Mechanism Privacy and Access Control 802.11 MAC Entity: MAC Basic Access Mechanism Privacy and Access Control 1 802.11 Protocol Entities LLC MAC MAC Sublayer MAC Layer Management Station Management PHY PLCP Sublayer PHY Layer Management PMD

More information

Last Lecture: Network Layer

Last Lecture: Network Layer Last Lecture: Network Layer. Design goals and issues Debate around service model/design principle question 2. Basic Routing Algorithms & Protocols Packet Forwarding Shortest-Path Algorithms Routing Protocols

More information

Last time. Multiple access protocols. Link-layer addressing. Channel partitioning MAC protocols. Random access MAC protocols

Last time. Multiple access protocols. Link-layer addressing. Channel partitioning MAC protocols. Random access MAC protocols Last time Multiple access protocols Channel partitioning MAC protocols TDMA, FDMA Random access MAC protocols Slotted Aloha, Pure Aloha, CSMA, CSMA/CD Taking turns MAC protocols Polling, token passing

More information

Wide Area Networks Routing Tables

Wide Area Networks Routing Tables Wide Area Networks Routing Tables A D F G I E H A Wide Area Network (WAN) is usually an arbitrary mesh of The stations, or nodes, usually have several connections or ports, with each port connecting to

More information

Chapter 16 Networking

Chapter 16 Networking Chapter 16 Networking Outline 16.1 Introduction 16.2 Network Topology 16.3 Network Types 16.4 TCP/IP Protocol Stack 16.5 Application Layer 16.5.1 Hypertext Transfer Protocol (HTTP) 16.5.2 File Transfer

More information

Module 4. Switched Communication Networks

Module 4. Switched Communication Networks Module 4 Switched Communication Networks Lesson 2 Switching Techniques: Circuit Switching 4.2.0 Specific Instructional Objectives At the end of this lesson the student will be able to: Explain the need

More information

Chapter 7: Internet at Work

Chapter 7: Internet at Work Chapter 7: Internet at Work Silvia Giordano ICA-EPFL 7: Internet at work 1 1 Introduction Chapter goal: understand how s support the applications with an example: application data generation process-to-process

More information

Chapter 13 Ad Hoc and Sensor Networks

Chapter 13 Ad Hoc and Sensor Networks Chapter 13 Ad Hoc and Sensor Networks 1 Outline Introduction Characteristics of Ad Hoc Networks Applications Routing Table-driven Routing Protocols Source-initiated On-demand Routing Hybrid Protocols Wireless

More information

Efficient Fair TDMA Scheduling In Wireless Multi-Hop Networks

Efficient Fair TDMA Scheduling In Wireless Multi-Hop Networks Efficient Fair TDMA Scheduling In Wireless Multi-Hop Networks Aggeliki Sgora 1, Dimitrios J. Vergados 2,,and Dimitrios D. Vergados 1 1 University of the Aegean Department of Information and Communication

More information

IEEE & b. By: Adel A. Youssef

IEEE & b. By: Adel A. Youssef IEEE 802.11 & 802.11b By: Adel A. Youssef adel@cs.umd.edu Contents 802.11 and 802.11b Technologies. Operating Modes. Protocol Architecture. 802.11 PHY Layer. 802.11b Enhancements to PHY Layer. 802.11 Data

More information

Networking basics. Mobile and Wireless Computing. Courtesey of Abdus Salam International Centre for Theoretical Physics, Trieste

Networking basics. Mobile and Wireless Computing. Courtesey of Abdus Salam International Centre for Theoretical Physics, Trieste Networking basics Courtesey of Abdus Salam International Centre for Theoretical Physics, Trieste Physical Layer This layer is concerned with the transmission of bits. Some of the issues handled in this

More information

Network Layer. Introduction Datagrams and Virtual Circuits Routing Traffic Control CS457

Network Layer. Introduction Datagrams and Virtual Circuits Routing Traffic Control CS457 Network Layer Introduction Datagrams and Virtual Circuits Routing Traffic Control Introduction Main Task of the network layer is to move packets from the source host to the destination host Lowest layer

More information

Medium Access Control (MAC) protocol

Medium Access Control (MAC) protocol Medium Access ontrol (MA) protocol omputers DNS Shared medium Point-to-Point. R R. WLAN AP R LAN. Shared medium AP DNS DNS: Domain Name System Figure 1: Different components of a network The Internet consists

More information

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction Wireless Physical Layer Q1. Is it possible to transmit a digital signal, e.g., coded as square wave as used inside a computer, using radio transmission without any loss? Why? It is not possible to transmit

More information

28 Networks and Communication Protocols

28 Networks and Communication Protocols 113 28 Networks and ommunication Protocols Trend in computer systems: personal computing. Reasons why: ost: economies of scale. lso, avoids large initial investment in timesharing system. Performance:

More information