Chapter 1 Basic concepts of wireless data networks (cont d)
|
|
- Cameron Carson
- 6 years ago
- Views:
Transcription
1 Chapter 1 Basic concepts of wireless data networks (cont d) Part 2: Medium access methods for mobile data networks Sept Fixed assignment access schemes in voice-oriented networks Frequency division multiple access (FDMA) Different users using different frequency channels Time division multiple access (TDMA) Different users using different time slots Code division multiple access (CDMA) Different users using different codes Time division duplex (TDD) The downlink and uplink of a connection use different time slots Frequency division duplex (FDD) Uplink and downlink use different frequency channels 2
2 Medium access schemes in voiceoriented networks A FDMA/FDD t uplink downlink A t FDMA/TDD User 1 User 2 User 3 User 4 A TDMA/FDD f1 f2 f3 f4 t uplink f1 f2 f3 f4 downlink t1 t2 f f A f1 f2 f3 f4 t 2 1 f1 f2 f3 f4 downlink uplink f TDMA/TDD downlink uplink f 3 Random access schemes in data networks Data traffic is bursty Fixed assignment access scheme wastes resources when traffic is bursty Random access schemes more flexible and efficient for data services Contention among users for access 4
3 Pure ALOHA Operation: When a packet arrives, it is encoded for error detection, then transmitted. At the receiver side, check the correctness when a packet received. If error-free, an ACK sent back. The sender will wait an amount of time for ACK. If ACK received within this time interval, transmission is successful. If ACK is not received in time, delay a random amount of time, then retransmit it. 5 An example of pure ALOHA T Successful transmission User 1 User 2 User 3 User 4 2T Random delay No other packet arrival New packet Rescheduled packet T: time for sending a packet : collision 6
4 Throughput of pure ALOHA A packet is successfully transmitted if no other packets arrive within one frame time of its start. Poisson arrival with mean λ pkt/s, including new and rescheduled packets P(N pkt arrive in time t) = (λt) N e - λ t / N!, N = 0, 1, Time for sending one packet T is constant. G= pkt sent per pkt time T= λ T Throughput (pkt successfully sent per pkt time T) 2G S = S max =0.184 when G=0.5 Ge Advantage: simple; disadvantage: low throughput 7 Slotted ALOHA Time is divided into discrete time intervals, each corresponding to one packet transmission Synchronization needed among different geographically dispersed users Operation When a packet arrives, it will be sent at the beginning of next time slot If ACK received in time, successful. Otherwise, delay this packet for a random interval and retransmitted. Slotted ALOHA is adopted in GPRS 8
5 Operation of slotted ALOHA User 1 User 2 User 3 User 4 T No other packet arrival T: one time slot Successful transmission Random delay New packet Rescheduled packet : collision 9 Throughput of slotted ALOHA A packet is successfully transmitted if no other packets arrive in the same time slot Poisson arrival with mean λ Time for sending one packet T. G= λt Throughput S = Ge S max =0.368 when G=1 G Twice the throughput of pure ALOHA (or is it really twice?) 10
6 Dynamic slotted ALOHA Full duplex communication in Mobitex: BS and mobile can transmit simultaneously Mobile can only transmit during certain free cycles consisting of several random slots that are periodically initiated by BS Long messages are transmitted in reserved time slots. 11 Dynamic slotted ALOHA (cont d) Operation: BS sends a free message to indicate a number of random slots for MS to send requests. MS having requests to send chooses one of these random time slots to send request. If the request is received by BS without collision, an Access Grant packet is sent by the BS to the MS indicating the reserved time slots for sending information message. MS sends the information message in the reserved time slot. 12
7 An example of dynamic slotted ALOHA Free Free AG to MS2 ACK to MS2 BS Message to MS MS Message from MS2 MS1 MS2 ACK from MS3 One message to MS3 MS1 and MS2 want to send requests to BS Access grant is given to MS2 MS2 then sends packet to BS in reserved time slot 13 Operation of this example BS sends a Free message indicating 5 random slots available BS sends a message to MS3 during these random slots (in downlink channel) MS1 and MS2 want to send requests to BS during these random slots. They randomly choose one of these 5 random slots to send requests. MS1 chooses slot 1 and MS2 chooses slot 3. These requests are received without collision by BS. Access Grant is given to MS2. MS2 sends message in reserved slot. BS sends ACK to MS2 indicating the success of the sent message. 14
8 Carrier sense multiple access (CSMA) Reason: the efficiency of ALOHA is too low as each station operates independently. By sensing channel status, collision can be significantly reduced. Operation: Before sending packet, the MS senses if the channel is idle. If idle, send packet. Otherwise, delay using a back-off algorithm, then sense the channel again. If packet collides, reschedule as in ALOHA. (Why would packets collide with sensing?) 15 An example of CSMA User 1 User 2 User 3 Reschedule delay Busy delay Packet arrival New packet Delayed packet Rescheduled packet : collision 16
9 Variations of CSMA Non-persistent CSMA: after sensing channel is busy, delay a certain amount of time before sensing the channel again. 1-persistent CSMA: after sensing the channel is busy, continues sensing the channel until the channel is idle and then sends the packet p-persistent CSMA (for slotted channel): after sensing the channel is busy, continues sensing the channel until it is idle. Then the packet is sent with probability p. Channel busy delay Non-persistent ready 1-persistent p-persistent 17 Throughput of CSMA Unslotted, 1-persistent: Slotted, 1-persistent: [ 1+ G + ag(1 + G + ag / 2) ] G G(1 + 2a) (1 e e ) + (1 + ag) e G(1+ 2a) S = ag G(1 + a) ag [ 1+ a e ] G (1 + a)(1 e e ) + ae G(1+ a) S = ag G(1 + a) Unslotted, non-persistent: ag Ge S = G(1 + 2a) + e ag Slotted, non-persistent: G: the same as in ALOHA a= τ/t P τ: maximum propagation delay T P : packet transmission time S age 1 e = ag ag + a 18
10 Comparison Throughput versus offered traffic load for various random access protocols 19 Comparison (cont d) Capacity versus normalized delay for various random access protocols 20
11 Comparison (cont d) Delay-throughput behavior of random access protocols 21 CSMA/CA (collision avoidance) Adopted by IEEE WLAN Operation: Step 1: When packet arrives, sense the channel. If it is idle, send packet; otherwise, choose a backoff time delay randomly. Then continues sensing the channel. Step 2: When channel becomes idle, delay an IFS (interframe spacing). Then count down the backoff delay. Step 3: If channel remains idle until the delay is 0, send packet. If channel becomes busy during delay countdown, freeze the delay and continues sensing the channel. Go to Step 2. 22
12 An example of CSMA/CA IFS IFS IFS IFS A Frame B C Frame Frame D E Frame Frame CW CW CW CW Delay after packet ready Back off Remaining back-off 23 Complications caused by wireless channel Hidden terminal problem: two nodes are too far away that they cannot sense the transmission of each other and cause collision. Throughput is decreased 24
13 Complications (cont d) Capture effect: when two nodes are trying to send packets simultaneously, and the distances to the receiver are different, the packet sent by the closer node may be correctly received, and performance may be improved. 25 Impact of capture effect Impact of capture effect on throughput, BPSK modulation and SNR=20dB 26
14 Impact of capture effect (cont d) Delay versus throughput of CSMA for BPSK modulation and SNR=20dB 27 Impact of hidden terminals Mobile terminal Access point Area 2 Area 1 Area 1 carrier sensible by red mobile terminal Area 2 carrier non-sensible by red mobile terminal, but still within coverage area of AP => hidden terminal effect Coverage areas of an AP and a mobile terminal in a WLAN 28
15 Impact of hidden terminals (cont d) With capture R MS < R BS R MS = R BS Without capture R MS : radius of the coverage of MS R BS : radius of the coverage of BS 29 Providing data services in voiceoriented networks Two reasons for providing data services in voice-oriented networks (to improve efficiency and save cost): Some portion of unused resources can be used by data users Short pauses in voice channel can be used for data services 30
16 Providing data services in FDMA system CDPD (cellular digital packet data) packet data system uses available frequency channel in existing analog FDMA cellular phone network (AMPS) Data rate<=19.2kbps Idle frequency channels are used for data services Talk pauses not exploited Frequency hopping allowed to release current channel to voice users Only one frequency channel for one data user: data rate limited 31 Average number of idle channels in FDMA system Required call blocking lower, more available channels for data services For 1% call blocking and 15 channels, 7 available 32
17 Average channel AMPS idle period Higher call blocking requirement, longer idle period 33 Providing data services in TDMA system GPRS in GSM Unused time slots are assigned for data services Multiple time slot assignment possible to increase data rate Talk pause not exploited 34
18 Movable boundary TDMA scheme with silence detection Some slots dedicated for data services only Remaining slots shared by data and voice users, with voice users having higher priority Movable boundary. When the number of voice users increases, the number of dedicated slots for data decreases Movable boundary Voice slots data slots Voice slots data slots frame frame 35 Providing data services in CDMA system Data services in 3G Integration of data and voice services Assign multiple parallel channels or reduce processing gain, data rate increased 36
Lecture 4: Wireless MAC Overview. Hung-Yu Wei National Taiwan University
Lecture 4: Wireless MAC Overview Hung-Yu Wei National Taiwan University Medium Access Control Topology 3 Simplex and Duplex 4 FDMA TDMA CDMA DSSS FHSS Multiple Access Methods Notice: CDMA and spread spectrum
More informationMultiple Access (1) Required reading: Garcia 6.1, 6.2.1, CSE 3213, Fall 2010 Instructor: N. Vlajic
1 Multiple Access (1) Required reading: Garcia 6.1, 6.2.1, 6.2.2 CSE 3213, Fall 2010 Instructor: N. Vlajic Multiple Access Communications 2 Broadcast Networks aka multiple access networks multiple sending
More informationMedium Access Control. MAC protocols: design goals, challenges, contention-based and contention-free protocols
Medium Access Control MAC protocols: design goals, challenges, contention-based and contention-free protocols 1 Why do we need MAC protocols? Wireless medium is shared Many nodes may need to access the
More informationMultiple Access Links and Protocols
Multiple Access Links and Protocols Two types of links : point-to-point PPP for dial-up access point-to-point link between Ethernet switch and host broadcast (shared wire or medium) old-fashioned Ethernet
More informationICE 1332/0715 Mobile Computing (Summer, 2008)
ICE 1332/0715 Mobile Computing (Summer, 2008) Medium Access Control Prof. Chansu Yu http://academic.csuohio.edu/yuc/ Simplified Reference Model Application layer Transport layer Network layer Data link
More informationAloha and slotted aloha
CSMA 2/13/06 Aloha and slotted aloha Slotted aloha: transmissions are synchronized and only start at the beginning of a time slot. Aloha sender A sender B collision sender C t Slotted Aloha collision sender
More informationChapter 6 Medium Access Control Protocols and Local Area Networks
Chapter 6 Medium Access Control Protocols and Local Area Networks Part I: Medium Access Control Part II: Local Area Networks CSE 3213, Winter 2010 Instructor: Foroohar Foroozan Chapter Overview Broadcast
More informationCHAPTER 7 MAC LAYER PROTOCOLS. Dr. Bhargavi Goswami Associate Professor & Head Department of Computer Science Garden City College
CHAPTER 7 MAC LAYER PROTOCOLS Dr. Bhargavi Goswami Associate Professor & Head Department of Computer Science Garden City College MEDIUM ACCESS CONTROL - MAC PROTOCOLS When the two stations transmit data
More informationECE 4450:427/527 - Computer Networks Spring 2017
ECE 4450:427/527 - Computer Networks Spring 2017 Dr. Nghi Tran Department of Electrical & Computer Engineering Lecture 5.4: Multiple Access Protocols Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527
More informationData Communications. Automatic Repeat Request Medium Access Control
Data Communications Automatic Repeat Request Medium Access Control Handling Error Cases Automatic Repeat request(arq), also known as Automatic Repeat Query, is an error-control method ARQ uses acknowledgements
More informationWireless Communications
4. Medium Access Control Sublayer DIN/CTC/UEM 2018 Why do we need MAC for? Medium Access Control (MAC) Shared medium instead of point-to-point link MAC sublayer controls access to shared medium Examples:
More informationPhysical Layer. Medium Access Links and Protocols. Point-to-Point protocols. Modems: Signaling. Modems Signaling. Srinidhi Varadarajan
P Physical Layer Srinidhi Varadarajan Medium Access Links and Protocols Three types of links : point-to-point (single wire, e.g. PPP, SLIP) broadcast (shared wire or medium; e.g, Ethernet, Wavelan, etc.)
More informationChapter 12 Multiple Access 12.1
Chapter 12 Multiple Access 12.1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12.2 Figure 12.1 Data link layer divided into two functionality-oriented sublayers
More informationChapter 4. The Medium Access Control Sublayer. Points and Questions to Consider. Multiple Access Protocols. The Channel Allocation Problem.
Dynamic Channel Allocation in LANs and MANs Chapter 4 The Medium Access Control Sublayer 1. Station Model. 2. Single Channel Assumption. 3. Collision Assumption. 4. (a) Continuous Time. (b) Slotted Time.
More informationCS 716: Introduction to communication networks. - 9 th class; 19 th Aug Instructor: Sridhar Iyer IIT Bombay
CS 716: Introduction to communication networks - 9 th class; 19 th Aug 2011 Instructor: Sridhar Iyer IIT Bombay Contention-based MAC: ALOHA Users transmit whenever they have data to send Collisions occur,
More informationMultiple Access Links and Protocols
Multiple Access Links and Protocols Two types of links : point-to-point PPP for dial-up access point-to-point link between Ethernet switch and host broadcast (shared wire or medium) old-fashioned Ethernet
More informationData Link Layer Technologies
Chapter 2.2 La 2 Data Link La Technologies 1 Content Introduction La 2: Frames Error Handling 2 Media Access Control General approaches and terms Aloha Principles CSMA, CSMA/CD, CSMA / CA Master-Slave
More informationPacket multiple access and the Aloha protocol
Packet multiple access and the Aloha protocol Massachusetts Institute of Technology Department of Aeronautics and Astronautics Slide 1 Packet Multiple Access PMA SHARED UPLINK TERMINAL TERMINAL APPL TRANS
More informationTopics. Link Layer Services (more) Link Layer Services LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS. flow control: error detection:
1 Topics 2 LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS Multiple access: CSMA/CD, CSMA/CA, token passing, channelization LAN: characteristics, i basic principles i Protocol architecture Topologies
More informationG 364: Mobile and Wireless Networking. CLASS 2, Wed. Jan Stefano Basagni Spring 2004 M-W, 11:40am-1:20pm, 109 Rob
G 364: Mobile and Wireless Networking CLASS 2, Wed. Jan 7 2004 Stefano Basagni Spring 2004 M-W, 11:40am-1:20pm, 109 Rob Wireless Issues Architecture, communication model and duplexing define the framework
More informationData Link Layer: Collisions
Data Link Layer: Collisions 1 Multiple Access Data Link layer divided into two sublayers. The upper sublayer is responsible for datalink control, The lower sublayer is responsible for resolving access
More informationMobile Communications Chapter 3 : Media Access
Mobile Communications Chapter 3 : Media Access 2. Motivation 3. SDMA, FDMA, TDMA 1. Aloha and contention based schemes 4. Reservation schemes 5. Collision avoidance, MACA 6. Polling CDMA (Lecture 6) Prof.
More informationLecture 6. Data Link Layer (cont d) Data Link Layer 1-1
Lecture 6 Data Link Layer (cont d) Data Link Layer 1-1 Agenda Continue the Data Link Layer Multiple Access Links and Protocols Addressing Data Link Layer 1-2 Multiple Access Links and Protocols Two types
More informationMultiple Access Protocols
Multiple Access Protocols Computer Networks Lecture 2 http://goo.gl/pze5o8 Multiple Access to a Shared Channel The medium (or its sub-channel) may be shared by multiple stations (dynamic allocation) just
More informationChapter 6 Medium Access Control Protocols and Local Area Networks
Chapter 6 Medium Access Control Protocols and Local Area Networks Part I: Medium Access Control Part II: Local Area Networks Chapter Overview Broadcast Networks All information sent to all users No routing
More informationRandom Access. 1. Aloha. 2. Slotted Aloha 3. CSMA 4. CSMA/CD
Random Access 1. Aloha 2. Slotted Aloha 3. CSMA 4. CSMA/CD Background Communication medium B No Collision collision A C Modern Local Area Networks (LANs) operate as follows Users are connected to communication
More informationChapter 3 MEDIA ACCESS CONTROL
Chapter 3 MEDIA ACCESS CONTROL Distributed Computing Group Mobile Computing Winter 2005 / 2006 Overview Motivation SDMA, FDMA, TDMA Aloha Adaptive Aloha Backoff protocols Reservation schemes Polling Distributed
More informationCS 43: Computer Networks Media Access. Kevin Webb Swarthmore College November 30, 2017
CS 43: Computer Networks Media Access Kevin Webb Swarthmore College November 30, 2017 Multiple Access Links & Protocols Two classes of links : point-to-point dial-up access link between Ethernet switch,
More information1-1. Switching Networks (Fall 2010) EE 586 Communication and. November 8, Lecture 30
EE 586 Communication and Switching Networks (Fall 2010) Lecture 30 November 8, 2010 1-1 Announcements Quiz on Wednesday Next Monday hands-on training on Contiki OS Bring your laptop 4-2 Multiple Access
More informationCS 43: Computer Networks. 27: Media Access Contd. December 3, 2018
CS 43: Computer Networks 27: Media Access Contd. December 3, 2018 Last Class The link layer provides lots of functionality: addressing, framing, media access, error checking could be used independently
More informationEITF25 Internet Techniques and Applications L4: Network Access. Stefan Höst
EITF25 Internet Techniques and Applications L4: Network Access Stefan Höst Repetition The link layer protocol should make sure that the data is correctly transmitted over the physical link using error
More informationMedium Access Control
Medium Access Control Fundamental Problem N nodes in vicinity want to transmit (to, say, N other nodes). How to do this interference free? Interference free means SINR Otherwise, we say that packets collide.
More informationMultiple-access protocols
Multiple Access Multiple-access protocols Random Access MA CSMA CSMA/CD CSMA/CA RANDOM ACCESS In a random access method, each station has the right to the medium without being controlled by any other station.
More information6.9 Summary. 11/20/2013 Wireless and Mobile Networks (SSL) 6-1. Characteristics of selected wireless link standards a, g point-to-point
Chapter 6 outline 6.1 Introduction Wireless 6.2 Wireless links, characteristics CDMA 6.3 IEEE 802.11 wireless LANs ( wi-fi ) 6.4 Cellular Internet Access architecture standards (e.g., GSM) Mobility 6.5
More informationThe MAC layer in wireless networks
The MAC layer in wireless networks The wireless MAC layer roles Access control to shared channel(s) Natural broadcast of wireless transmission Collision of signal: a /space problem Who transmits when?
More informationRandom Assignment Protocols
Random Assignment Protocols Random assignment strategies attempt to reduce problem occur in fixed assignment strategy by eliminating pre allocation of bandwidth to communicating nodes. Random assignment
More informationMultiple Access. Data Communications and Networking
Multiple Access In the previous part we discussed data link control, a mechanism which provides a link with reliable communication. In the protocols we described, we assumed that there is an available
More informationMULTIPLE ACCESS PROTOCOLS 2. 1
MULTIPLE ACCESS PROTOCOLS AND WIFI 1 MULTIPLE ACCESS PROTOCOLS 2. 1 MULTIPLE ACCESS LINKS, PROTOCOLS Two types of links : point-to-point broadcast (shared wire or medium) POINT-TO-POINT PPP for dial-up
More informationUnit 7 Media Access Control (MAC)
Unit 7 Media Access Control (MAC) 1 Internet Model 2 Sublayers of Data Link Layer Logical link control (LLC) Flow control Error control Media access control (MAC) access control 3 Categorization of MAC
More informationCSC 4900 Computer Networks: Wireless Networks
CSC 4900 Computer Networks: Wireless Networks Professor Henry Carter Fall 2017 Last Time Mobile applications are taking off! What about current platforms is fueling this? How are an application s permission
More informationECEN 5032 Data Networks Medium Access Control Sublayer
ECEN 5032 Data Networks Medium Access Control Sublayer Peter Mathys mathys@colorado.edu University of Colorado, Boulder c 1996 2005, P. Mathys p.1/35 Overview (Sub)networks can be divided into two categories:
More informationLink Layer and LANs 안상현서울시립대학교컴퓨터 통계학과.
Link Layer and LANs 안상현서울시립대학교컴퓨터 통계학과 ahn@venus.uos.ac.kr Data Link Layer Goals: understand principles behind data link layer services: error detection, correction sharing a broadcast channel: multiple
More informationCCM 4300 Lecture 5 Computer Networks, Wireless and Mobile Communications. Dr Shahedur Rahman. Room: T115
CCM 4300 Lecture 5 Computer Networks, Wireless and Mobile Communications Dr Shahedur Rahman s.rahman@mdx.ac.uk Room: T115 1 Recap of Last Session Described the physical layer Analogue and Digital signal
More informationData Link Layer -2- Network Access
EITF25 Internet: Technology and Applications Data Link Layer -2- Network Access 2015, Lecture 03 Kaan Bür Previously on EITF25 Logical Link Control Sublayer Flow control Send data Wait for ACK Error control
More informationCOMPUTER NETWORKS - Local area networks
Local area networks Telecommunication Networks Group firstname.lastname@polito.it http://www.telematica.polito.it/ COMPUTER NETWORKS LANs - 1 Copyright Quest opera è protetta dalla licenza Creative Commons
More informationLocal area networks. Copyright
Local area networks Telecommunication Networks Group firstname.lastname@polito.it http://www.telematica.polito.it/ COMPUTER NETWORKS LANs - 1 Copyright Quest opera è protetta dalla licenza Creative Commons
More informationRedes de Computadores. Medium Access Control
Redes de Computadores Medium Access Control Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto 1 » How to control the access of computers to a communication medium?» What is the ideal Medium
More informationEP2210 FEP3210 Performance analysis of Communication networks. Topic 2 Medium access control (or multiple access protocols)
EP2210 FEP3210 Performance analysis of Communication networks Topic 2 Medium access control (or multiple access protocols) 1 Medium access control Lecture material: R. Rom, M. idi, Multiple access protocols,
More informationData Link Layer -2- Network Access
EITF25 Internet: Technology and Applications Data Link Layer -2- Network Access 2013, Lecture 03 Kaan Bür, Stefan Höst Previously on EITF25 Logical Link Control Sublayer Flow control Send data Wait for
More informationMedium Access Control
Medium Access Control All material copyright 1996-2009 J.F Kurose and K.W. Ross, All Rights Reserved 5: DataLink Layer 5-1 Link Layer Introduction and services Multiple access protocols Ethernet Wireless
More informationECE453 Introduction to Computer Networks. Broadcast vs. PPP. Delay. Lecture 7 Multiple Access Control (I)
ECE453 Introduction to Computer Networks Lecture 7 Multiple Access Control (I) 1 Broadcast vs. PPP Broadcast channel = multiaccess channel = random access channel Broadcast LAN Satellite network PPP WAN
More informationLecture 12 December 04, Wireless Access. Graduate course in Communications Engineering. University of Rome La Sapienza. Rome, Italy
Lecture 12 December 04, 2017 Wireless Access Graduate course in Communications Engineering University of Rome La Sapienza Rome, Italy 2017-2018 Random Medium Access Control Part II - CSMA and Collision
More informationMedium Access Control Sublayer Chapter 4
Medium Access Control Sublayer Chapter 4 Channel Allocation Problem Multiple Access Protocols Ethernet Wireless LANs Broadband Wireless Bluetooth RFID Data Link Layer Switching Revised: August 2011 & February
More informationThe MAC layer in wireless networks
The MAC layer in wireless networks The wireless MAC layer roles Access control to shared channel(s) Natural broadcast of wireless transmission Collision of signal: a time/space problem Who transmits when?
More informationOutline. Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties
Outline Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties Layered Network Architectures - OSI framework descriptions of layers
More informationCS 332 Computer Networks Wireless Networks
CS 332 Computer Networks Wireless Networks Professor Szajda Chapter 6: Wireless and Mobile Networks Background: # wireless (mobile) phone subscribers now exceeds # wired phone subscribers! computer nets:
More informationRahman 1. Application
Data Link layer Overview of IEEE 802.11 Application Presentation Session Transport LLC: On transmission, assemble data into a frame with address and CRC fields. On reception, disassemble frame, perform
More informationWireless Networks. CSE 3461: Introduction to Computer Networking Reading: , Kurose and Ross
Wireless Networks CSE 3461: Introduction to Computer Networking Reading: 6.1 6.3, Kurose and Ross 1 Wireless Networks Background: Number of wireless (mobile) phone subscribers now exceeds number of wired
More informationMSIT 413: Wireless Technologies Week 8
MSIT 413: Wireless Technologies Week 8 Michael L. Honig Department of EECS Northwestern University November 2017 The Multiple Access Problem How can multiple mobiles access (communicate with) the same
More informationChapter 4. The Medium Access Control Sublayer
Chapter 4 The Medium Access Control Sublayer The Channel Allocation Problem Static Channel Allocation in LANs and MANs Dynamic Channel Allocation in LANs and MANs Dynamic Channel Allocation in LANs and
More informationComputer Network Fundamentals Spring Week 3 MAC Layer Andreas Terzis
Computer Network Fundamentals Spring 2008 Week 3 MAC Layer Andreas Terzis Outline MAC Protocols MAC Protocol Examples Channel Partitioning TDMA/FDMA Token Ring Random Access Protocols Aloha and Slotted
More informationProtocols for Multiaccess Networks
Protocols for Multiaccess Networks Hosts broadcast packets When a collision occurs, all transmitted packets are lost Lost packets have to be retransmitted => Need Multiaccess Protocol Model - Slotted Aloha
More informationCSE 461: Wireless Networks
CSE 461: Wireless Networks Wireless IEEE 802.11 A physical and multiple access layer standard for wireless local area networks (WLAN) Ad Hoc Network: no servers or access points Infrastructure Network
More informationCOS 140: Foundations of Computer Science
COS 140: Foundations of Computer Science ALOHA Network Protocol Family Fall 2017 Homework 2 Introduction 3 Network Protocols.......................................................... 3 Problem.................................................................
More informationComputer Networks Medium Access Control. Mostafa Salehi Fall 2008
Computer Networks Medium Access Control Mostafa Salehi Fall 2008 2008 1 Outline Issues ALOHA Network Ethernet Token Ring Wireless 2 Main Issues Local Area Network (LAN) : Three or more machines are physically
More informationCSE 461: Multiple Access. Homework: Chapter 2, problems 1, 8, 12, 18, 23, 24, 35, 43, 46, and 58
CSE 461: Multiple Access Homework: Chapter 2, problems 1, 8, 12, 18, 23, 24, 35, 43, 46, and 58 Next Topic Key Focus: How do multiple parties share a wire? This is the Medium Access Control (MAC) portion
More informationLANs. Local Area Networks. via the Media Access Control (MAC) SubLayer. Networks: Local Area Networks
LANs Local Area Networks via the Media Access Control (MAC) SubLayer 1 Local Area Networks Aloha Slotted Aloha CSMA (non-persistent, 1-persistent, p-persistent) CSMA/CD Ethernet Token Ring 2 Network Layer
More informationCOMP/ELEC 429/556 Introduction to Computer Networks
COMP/ELEC 429/556 Introduction to Computer Networks Broadcast network access control Some slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang T. S. Eugene Ng eugeneng
More informationData Link Layer: Overview, operations
Data Link Layer: Overview, operations Chapter 3 1 Outlines 1. Data Link Layer Functions. Data Link Services 3. Framing 4. Error Detection/Correction. Flow Control 6. Medium Access 1 1. Data Link Layer
More informationMultiple Access Communications. EEE 538, WEEK 11 Dr. Nail Akar Bilkent University Electrical and Electronics Engineering Department
Multiple Access Communications EEE 538, WEEK 11 Dr. Nail Akar Bilkent University Electrical and Electronics Engineering Department 1 Multiple Access Satellite systems, radio networks (WLAN), ethernet segment
More informationWireless Medium Access Control Protocols
Wireless Medium Access Control Protocols Telecomunicazioni Undergraduate course in Electrical Engineering University of Rome La Sapienza Rome, Italy 2007-2008 Classification of wireless MAC protocols Wireless
More informationIntelligent Transportation Systems. Medium Access Control. Prof. Dr. Thomas Strang
Intelligent Transportation Systems Medium Access Control Prof. Dr. Thomas Strang Recap: Wireless Interconnections Networking types + Scalability + Range Delay Individuality Broadcast o Scalability o Range
More informationData Link Layer: Multi Access Protocols
Digital Communication in the Modern World Data Link Layer: Multi Access Protocols http://www.cs.huji.ac.il/~com1 com1@cs.huji.ac.il Some of the slides have been borrowed from: Computer Networking: A Top
More informationETSN01 Exam Solutions
ETSN01 Exam Solutions March 014 Question 1 (a) See p17 of the cellular systems slides for a diagram and the full procedure. The main points here were that the HLR needs to be queried to determine the location
More informationHigh Level View. EE 122: Ethernet and Random Access protocols. Medium Access Protocols
High Level View EE 122: Ethernet and 802.11 Ion Stoica September 18, 2002 Goal: share a communication medium among multiple hosts connected to it Problem: arbitrate between connected hosts Solution goals:
More informationMobile and Sensor Systems
Mobile and Sensor Systems Lecture 2: Mobile Medium Access Control Protocols and Wireless Systems Dr Cecilia Mascolo In this lecture We will describe medium access control protocols and wireless systems
More informationCSC 4900 Computer Networks: The Link Layer
CSC 4900 Computer Networks: The Link Layer Professor Henry Carter Fall 2017 Last Time We talked about intra-as routing protocols: Which routing algorithm is used in RIP? OSPF? What techniques allow OSPF
More informationWireless Local Area Network (IEEE )
Wireless Local Area Network (IEEE 802.11) -IEEE 802.11 Specifies a single Medium Access Control (MAC) sublayer and 3 Physical Layer Specifications. Stations can operate in two configurations : Ad-hoc mode
More informationLANs Local Area Networks LANs provide an efficient network solution : To support a large number of stations Over moderately high speed
Local Area Networks LANs provide an efficient network solution : To support a large number of stations Over moderately high speed With relatively small bit errors Multiaccess Protocols Communication among
More informationCSE 6811 Ashikur Rahman
Data Link layer Application Overview of IEEE 802.11 LLC: On transmission, assemble data into a frame with address and CRC fields. On reception, disassemble frame, perform address recognition and CRC validation.
More informationLogical Link Control (LLC) Medium Access Control (MAC)
Overview of IEEE 802.11 Data Link layer Application Presentation Session Transport LLC: On transmission, assemble data into a frame with address and CRC fields. On reception, disassemble frame, perform
More informationMAC Sublayer(1) Principal service of the Medium Access Control Sublayer: Allocating a single broadcast channel (mostly a LAN) among competing users
MAC Sublayer(1) Principal service of the Medium Access Control Sublayer: Allocating a single broadcast channel (mostly a LAN) among competing users Static Channel Allocation: Frequency Division Multiplexing
More informationCOMMUNICATION NETWORKS NETW 501
COMMUNICATION NETWORKS NETW 501 TUTORIAL 6 Presented by: Eng. Hana Hesham Eng. Mohamed Atef Data Link Layer Data Link Layer is split into 2 sublayers which are the Logical Link Control (LLC) and the Medium
More informationChapter 5: Link layer
Chapter 5: Link layer our goals: v understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing local area networks:
More informationThe Medium Access Control Sublayer
The Medium Access Control Sublayer Chapter 4 Channel Allocation Problem Static channel allocation Assumptions for dynamic Assumptions for Dynamic Channel Allocation 1. Independent traffic 2. Single channel
More informationLecture 23 Overview. Last Lecture. This Lecture. Next Lecture ADSL, ATM. Wireless Technologies (1) Source: chapters 6.2, 15
Lecture 23 Overview Last Lecture ADSL, ATM This Lecture Wireless Technologies (1) Wireless LAN, CSMA/CA, Bluetooth Source: chapters 6.2, 15 Next Lecture Wireless Technologies (2) Source: chapter 16, 19.3
More informationJaringan Komputer. Broadcast Network. Outline. MAC (Medium Access Control) Channel Allocation Problem. Dynamic Channel Allocation
Broadcast Network Jaringan Komputer Medium Access Control Sublayer 2 network categories: point-to-point connections broadcast channels Key issue in broadcast network: how to determine who gets to use the
More informationCMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 16
CMPE 150/L : Introduction to Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 16 1 Final project demo Please do the demo next week to the TAs. So basically you may need
More informationComputer Networks. Today. Principles of datalink layer services Multiple access links Adresavimas, ARP LANs Wireless LANs VU MIF CS 1/48 2/48
Computer Networks VU MIF CS 1/48 Today Principles of datalink layer services Multiple access links Adresavimas, ARP LANs Wireless LANs 2/48 1 Link layer: introduction terminology: hosts and routers: nodes
More informationAn Efficient Scheduling Scheme for High Speed IEEE WLANs
An Efficient Scheduling Scheme for High Speed IEEE 802.11 WLANs Juki Wirawan Tantra, Chuan Heng Foh, and Bu Sung Lee Centre of Muldia and Network Technology School of Computer Engineering Nanyang Technological
More informationLink Layer I: ALOHA, Time-, Frequency-, and Code Division. COS 463: Wireless Networks Lecture 4 Kyle Jamieson
Link Layer I: ALOHA, Time-, Frequency-, and Code Division COS 463: Wireless Networks Lecture 4 Kyle Jamieson Review: The Data Link Layer (L2) Enables exchange of atomic messages (frames) between end hosts
More informationCS 716: Introduction to communication networks. - 8 th class; 17 th Aug Instructor: Sridhar Iyer IIT Bombay
CS 716: Introduction to communication networks - 8 th class; 17 th Aug 2011 Instructor: Sridhar Iyer IIT Bombay Key points to consider for MAC Types/Modes of communication: Although the medium is shared,
More informationPrinciples of Wireless Sensor Networks
Principles of Wireless Sensor Networks https://www.kth.se/social/course/el2745/ Lecture 5 January 31, 2013 Carlo Fischione Associate Professor of Sensor Networks e-mail: carlofi@kth.se http://www.ee.kth.se/~carlofi/
More informationFairness in the IEEE network. Shun Y. Cheung
Fairness in the IEEE 802.11 network Shun Y. Cheung Simple FIFO queueing High data rate flow Output queue (infinite size) Low data rate flow Packets from low data rate flow experience excessive queueing
More informationEE 122: Ethernet and
EE 122: Ethernet and 802.11 Ion Stoica September 18, 2002 (* this talk is based in part on the on-line slides of J. Kurose & K. Rose) High Level View Goal: share a communication medium among multiple hosts
More informationLAN PROTOCOLS. Beulah A AP/CSE
LAN PROTOCOLS Beulah A AP/CSE IEEE STANDARDS In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety
More informationCSE 461: Multiple Access Networks. This Lecture
CSE 461: Multiple Access Networks This Lecture Key Focus: How do multiple parties share a wire? This is the Medium Access Control (MAC) portion of the Link Layer Randomized access protocols: 1. Aloha 2.
More informationCOMP476 Networked Computer Systems. Polling. Sharing the Wire. LAN Technologies. COMP476 Networked Computer Systems 1
Media Access Control Sub Layer COMP476 Networked Computer Systems Sharing Common Media There are several ways to share common media. Some methods are: Frequency division multiplexing Time division multiplexing
More informationCSE 461 Multiple Access. David Wetherall
CSE 461 Multiple Access David Wetherall djw@cs.washington.edu How to share a link Multiplexing = networking term for sharing a resource among multiple users (e.g., link, protocol instance) Topics: Multiplexing
More informationLecture 19. Principles behind data link layer services Framing Multiple access protocols
Link Layer Lecture 19 Principles behind data link layer services Framing Multiple access protocols ALOHA *The slides are adapted from ppt slides (in substantially unaltered form) available from Computer
More information