Intelligent Transportation Systems. Medium Access Control. Prof. Dr. Thomas Strang

Size: px
Start display at page:

Download "Intelligent Transportation Systems. Medium Access Control. Prof. Dr. Thomas Strang"

Transcription

1 Intelligent Transportation Systems Medium Access Control Prof. Dr. Thomas Strang

2 Recap: Wireless Interconnections Networking types + Scalability + Range Delay Individuality Broadcast o Scalability o Range o Delay o Individuality Relevance Cellular Scalability Range + Delay + Individuality Ad-hoc M. Röckl and T. Strang, 2009

3 Medium Access Control

4 Medium Access Control Basic functions Medium Access Control is required to control the access of multiple nodes on a shared medium (e.g. wired or wireless channel) Multiple Access Control: During packet reception no other node within interference range should transmit simultaneously Prioritization: Packets with higher priority should get access to the medium first Local: packet prioritization of a single node Global: packet prioritization of all nodes Multi-channel operation: Packets should be assigned to the appropriate channel (e.g. channel with lowest load, fastest data rate, regulatively assigned) Packet 1 Node 1 Node 1 Node 5 Node 2 Medium Access Control Channel 1 Packet i Shared Medium Packet 1 Channel 2 Node 2 Packet k Node 3 Node 4 Packet 1 Node n Channel m Packet l M. Röckl and T. Strang, 2009

5 Medium Access Control MAC in VANETs Static channel assignment structure, such as static TDMA, is not suitable for Vehicular Ad-hoc Networks (VANETs) due to their lack of a priori knowledge about transmission characteristics and synchronization dynamic channel assignment Centralized channel coordination, such as polling, is not feasible in VANETs due to the lack of a central infrastructure decentralized channel coordination Nodes get access to the channel only if required (event-triggered) Nodes have to compete with other nodes to gain access to the medium (contention) M. Röckl and T. Strang, 2009

6 Medium Access Control Multiple access Channel Separation Channel Assignment Channel Coordination Channel Access SDMA TDMA FDMA CDMA Static SDMA = Space Division Multiple Access TDMA = Time Division Multiple Access FDMA = Frequency Division Multiple Access CDMA = Code Division Multiple Access Centralized Random Access (Slotted) Aloha CSMA Dynamic Decentralized Hybrid Solutions CSMA/CA Reservation-based MACA PRMA Reservation TDMA M. Röckl and T. Strang, 2009

7 Random Access MAC

8 Medium Access Control Aloha MAC Part of the ALOHAnet developed by University of Hawaii in 1970 If a node has data to transmit, it immediately accesses the channel If the receiver is within interference range of two transmitters which simultaneously send data on the channel, both packets are lost due to collision (complete or partial collisions) Max. throughput: ~18% (82% lost due to packet collisions) + Simple Bad channel utilization Sender A Sender B Sender C Complete collision Partial collision t M. Röckl and T. Strang, 2009

9 Medium Access Control Aloha Protocol Any terminal is allowed to transmit without considering whether channel is idle or busy If packet is received correctly, the base station transmits an acknowledgement. If no acknowledgement is received by the sender, 1) it assumes the packet to be lost 2) it retransmits the packet after waiting a random time, usually with probability Pr in every slot. [J-P Linnartz]

10 Medium Access Control Slotted Aloha Time is divided in discrete intervals (=time slots) A node can only transmit at the beginning of a slot If a receiver is within interference range of two transmitters which simultaneously send data, both packets are lost due to collision Packet size restricted to slot size Max. throughput: ~36% (64% lost due to packet collisions) + Doubles channel utilization compared to pure Aloha Synchronization required Still suboptimal channel utilization Sender A Sender B Sender C Complete collisions only t M. Röckl and T. Strang, 2009

11 Collision probability vs. throughput Collisionrate = 1 Throughput OfferedTraffic [Rico-Garcia et al. 2010]

12 Medium Access Control Carrier Sense Multiple Access (CSMA) Collisions cannot be detected in wireless communication as it is done in wired communication because of high power difference between sent and received signal Listen while talk is not feasible in wireless networks Idea: Listen when not sending If someone else is transmitting, listen until transmission is finished If the channel is idle, stop listening and start transmitting Listen before talk No interruption of ongoing transmission ( polite Aloha ) M. Röckl and T. Strang, 2010

13 CSMA with Collision Avoidance CSMA: Sensing the medium before accessing it ( listen before talk) Physical carrier sensing: The medium is sensed to be busy if the received signal power exceeds a CS signal threshold value Virtual carrier sensing: Every node maintains a network allocation vector (NAV) and updates it by means of the duration field of the currently sent message Drawback: Collisions are likely to occur directly after current transmission ends if several nodes wait for the medium to become idle Idea: Every node waits for additional random time (called backoff time) before transmission starts

14 Medium Access Control CSMA/CA in its simple form If a node wants to access the shared medium, at first it senses the medium for a certain time Sensing If the medium has sensed to be free for that certain time, the node accesses it immediately and begins to send the packet Busy Sensing Sensing DATA If the medium has sensed to be busy, the node chooses a random backoff time it has to wait after the medium is free again, before it starts transmitting Backoff DATA B. Kloiber and T. Strang, 2010

15 Medium Access Control CSMA Persistency 1-persistent CSMA If channel is idle, node immediately accesses the channel If channel is busy, node persistently senses the channel until it becomes idle Problem: When channel becomes idle all waiting nodes access the channel in parallel Collisions can occur infinitely Non-persistent CSMA If channel is idle, node immediately accesses the channel If channel is busy, node starts backoff and reschedules future sensing Problem: Long idle times in case of long backoff times p-persistent CSMA If the channel is idle: node accesses the channel with probability p, or node starts the backoff with probability (1-p) If channel is busy, node persistently senses the channel until it becomes idle Good trade-off between 1-persistent CSMA and nonpersistent CSMA Sense Carrier Busy? no Transmit Sense Carrier Busy? no Transmit Sense Carrier Busy? no yes yes yes Transmit with probability p or Start backoff with p. (1-p) Wait M. Röckl and T. Strang, 2009

16 Medium Access Control Slotted p-persistant CSMA Sender A wants to transmit. It selects a backoff number of 3 Sender A Sender B Sender C Sender B wants to transmit. It selects a backoff number of 8 1. If a node wants to transmit, it senses the channel 2. If the channel is busy, it waits until it becomes idle 3. When channel becomes idle, node generates a random number for backoff counter 4. As long as the channel is idle the backoff counter is decremented with every slot 5. If the channel becomes busy, the backoff counter is frozen until the channel gets idle again 6. When the backoff counter reaches zero, the node starts transmitting in the next slot Sender A s backoff counter is zero It accesses the channel Sender B detects busy channel and freezes backoff timer Sender A defers transmission because channel is busy Sender C wants to transmit. It selects a backoff number of 2 Collision t M. Röckl and T. Strang, 2009

17 Medium Access Control Transmission Acknowledgements in CSMA Successful transmission can not be detected by listening on the channel as it is done in CSMA/CD Acknowledgements (ACK) sent by the receiver after successful reception of a data packet can be used to provide feedback to the sender Acknowledgements in CSMA: Automatic retransmission triggered by missing acknowledgements Higher layer (e.g. TCP/IP) retransmission schedule usually not suitable for wireless communication Data link layer ACKs can be scheduled faster and can be tailored to respective PHY layer normally used in wireless CSMA systems Problem: Multiple ACKs in multicast or broadcast communication will result in the so called broadcast storm problem collision of ACK packets Based on Ni et al. (1999): The Broadcast Storm Problem in a Mobile Ad Hoc Network M. Röckl and T. Strang, 2010

18 Medium Access Control Throughput Performance Comparison Throughput persistent CSMA 0.9 Nonpersistent CSMA persistent CSMA persistent CSMA persistent CSMA Slotted Aloha 0.2 Aloha Traffic Load Source: Dharma et al. (2003): Multiple Radio Access M. Röckl and T. Strang, 2009

19 Ad-hoc Networking Problems directly influencing MAC

20 Medium Access Control Interference Transmission range: Range within a packet can be successfully received if there is no interference Detection range (=Carrier sense range): Range within communication is not possible but signal can be detected by carrier sensing Interference range: Range within signal can interfere with other signals, channel sensed to be free (signal adds to background noise) Interference Range can be up to 10x of the Communication Range! B. Kloiber and T. Strang, 2010

21 Medium Access Control Ad-hoc networking problems Hidden-Terminal-Problem (HTP) Packet collision at the receiver (R1) due to simultaneous transmission of nodes (S1 & S2) that are not within each others detection range but in the interference range of the receiver Packet collisions Exposed-Terminal-Problem (ETP) Transmission blocking due to ongoing transmission between two nodes (S1 & R1) with a third node (S3) that is not in the interference range of the receiver (R1) but in detection range of the sender (S1) and thus suppresses its transmission to a fourth node (R2) which is not in the sender s (S1) interference range communication between S3 and R2 would be possible without collisions but will be suppressed Low bandwidth utilization R2 S3 S1 R1 S2 Collision occurs at the receiver (not at the transmitter) Carrier Sensing cannot avoid collisions M. Röckl and T. Strang, 2009

22 Closed-Open Network A Closed Network is a network where all the nodes are visible. No hidden terminal problem Network diameter < range An Open Network is a network where not all the nodes are visible. Hidden terminal problem Network diameter > range C. Rico-Garcia and T. Strang, 2010

23 MANETs and their issues Capture effect: There are at least two simultaneous transmissions within the communication range, but due to a sufficient signal-tosignal ratio one message can be received correctly (b)

24 Positive aspect of capture effect db Ideal Channel [Rico-Garcia 2010] db db Sensrange = 5 km Hata Okumura Channel Sensrange = 5 Hata Ideal Channel Sensrange = 5 km km

25 Reservation Based MAC

26 Medium Access Protocol Channel Reservation Reservation of an exclusive channel can be used to avoid packet collisions Channel reservation has to be known to all nodes within two-hops from the sender Implicit vs. explicit reservation: frame 1 A C D A B A F Implicit reservation: frame 2 A C A B A Reservation Aloha: Once acquired slot is implicitly assigned to the node for future usage until it is not used anymore Explicit reservation: frame 3 frame 4 frame 5 A A C E E B B A A F F D Busy Tone Multiple Access (BTMA) for multi-channel operation (control & data channel): busy tone transmitted by sender and receiver informs nodes in the vicinity RTS/CTS messages in MACA Explicit channel reservation causes delays and increased traffic load A B A F D M. Röckl and T. Strang, 2009

27 Medium Access Control Medium Access with Collision Avoidance (MACA) Introduction of two-way handshake with two new messages exchanged prior to data transmission: Request-To-Send (RTS): Announcement of the transmission initiator having data to transmit (Alice: Hey, Bob? ) Clear-To-Send (CTS): Acknowledgement of the transmission responder being ready to receive data (Bob: What do you have to say, Alice? ) RTS and CTS include the amount of data to exchange every node that hears RTS and/or CTS is aware of the ongoing transmission A node that receives CTS and/or RTS suppresses its transmission for the specified time (avoids HTP) RTS and no CTS is allowed to transmit (avoids ETP) If no CTS is received after sending an RTS (due to a collision or ongoing transmission), the initiator starts backoff algorithm and reschedules next RTS RTS/CTS is sometimes called virtual sensing in contrast to physical sensing in CSMA Neighbor Initiator Responder Neighbor RTS DATA RTS CTS DATA Source: Karn (1990):MACA A New Channel Access Method for Packet Radio CTS No transmission M. Röckl and T. Strang, 2009

28 Hybrid Medium Access Control Combining Random Access w/ Reservation Based MAC CSMA/CA = CSMA (with ACKs) and MACA As efficient as MACA in situation with HTP or ETP and as efficient as CSMA otherwise Physical (Carrier Sensing) and virtual carrier sensing (RTS/CTS) CSMA/CA is the standard medium access control techniques used in Wireless LAN systems (IEEE ) M. Röckl and T. Strang, 2010

29 Typical MAC Performance Metrics Update Delay: Time interval between two consecutive messages from the same sender. Delay / Latency: Time spending in the waiting queue, until the transmission is complete Throughput: Average rate of successful message delivery over a communication channel Stability: The system should be able to handle instantaneous loads that are greater than the maximum sustained load when long-term offered load is less than the maximum Robustness: The wireless channel is time-varying and error-prone. This behaviour should not cause an unstable system. (Fairness, Power consumption, multimedia support) etc. B. Kloiber and T. Strang, 2010

30 Beaconing in VANETs In Vehicular Ad-hoc Networks (VANETs), all nodes are broadcast transmitters and receivers, they are therefore sometimes referred to as Mobile Ad-hoc Multibroadcast Networks Interesting to note: Obviously there cannot arise the exposed terminal problem Base functionality, also for safety applications, is implemented using short periodic status update beacons (TCAS/ADS-B, AIS, Car2Car, RCAS, military applications) Beaconing is the core communication mode in many safety systems. The MAC layer has an important role in the successful transmission of beacons. The hidden terminal problem is a major issue. C. Rico-Garcia and T. Strang, 2010

31 Scalability Challenges for Car2Car Networks B. Kloiber and T. Strang, 2010

32 Transmission Delay Tx Tx Video, sound, data Short status update buffer May I send? MAC MAC Network Network Yes! No Rx Rx Classical network Beaconing VANET [Rico-Garcia 2010]

33 Update Delay The Update Delay is the time between the reception of two consecutive status update messages coming from the same node. Knowledge certainty Status Update Receive Update Delay Frame Status Update Receive Status Update NOT Receive Update Delay Status Update NOT Receive Status Update Receive Time B. Kloiber and C. Rico-Garcia, 2010

34 Importance of the Update Delay Actions (breaking, change in direction, etc.) are decided according to the status updates. The larger the time between status updates, the lower the reaction time. TA Train B... BC TA D Guard D Brake D Alert D Comm Train A RCAS Example: Status update frequency = 1Hz ; 1 packet lost 2 s update delay. At 160 km/h, 2s 90m C. Rico-Garcia and T. Strang, 2010

35 General analysis of a MAC protocol Collision Rate Update Delay Throughput The Update Delay depends on many parameters: Offered Traffic, Propagation Channel, Network Dynamics. C. Rico-Garcia and T. Strang, 2010

36 Update delay medium access of Slotted Aloha [Rico-Garcia 2010]

37 Self Organized TDMA

38 SOTDMA protocol as used in the Automatic Identification system (AIS) 1 1 Node 1 Node 2 I want to send, which slots are free? Time C. Rico-Garcia and T. Strang, 2010

39 SOTDMA protocol as used in the Automatic Identification system (AIS) Present Present Reserve 1 NSS2 1 Reserve Mine SI=3 (20%) NSS2 Observing! Node 1 Observing! Node 2 I send in this slot Among free slots I choose this as my central slot NSS Time And, in next frame I will choose and reserve 1 free slot between NSS and +-SI/2 C. Rico-Garcia and T. Strang, 2010

40 Collision rate of SOTDMA. [Rico-Garcia 2010]

41 Update Delay SOTDMA [Rico-Garcia 2010]

42 Hidden terminal problem in SOTDMA Reserve Node Reserve 2 1 Node Node Node 2 Node 1 Node 3 3 Reserve 2 3 Time If Node 1 and Node 3 would use different channels, Node 2 wouldn t see any collision C. Rico-Garcia and T. Strang, 2010

43 Cell-based Orientation-aware Multi Broadcast MAC

44 COMB Reserve Node Reserve 2 1 Node 2 Node Node 1 Node 3 Node 2 2 Reserve 3 3 Time Nodes in range can be in the same channel. Nodes not in range must be in different channels. C. Rico-Garcia and T. Strang, 2010

45 10 3 Number of channels and cell size in COMB Node 1 All the nodes inside a channel see the same network closed SOTDMA network At least 12 channels are 10 8 needed 3 12 It is possible to reuse the 11 7 same channels C. Rico-Garcia and T. Strang, 2010

46 Protocols Comparison: Update Delay [Rico-Garcia 2010]

47 Protocols Comparison: Update Delay [Rico-Garcia 2010]

CS 43: Computer Networks. 27: Media Access Contd. December 3, 2018

CS 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 information

Medium 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 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 information

CS 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 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 information

Lecture 12 December 04, Wireless Access. Graduate course in Communications Engineering. University of Rome La Sapienza. Rome, Italy

Lecture 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 information

Aloha and slotted aloha

Aloha 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 information

Unit 7 Media Access Control (MAC)

Unit 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 information

Chapter 12 Multiple Access 12.1

Chapter 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 information

The MAC layer in wireless networks

The 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 information

Mobile Communications Chapter 3 : Media Access

Mobile 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 information

MAC LAYER. Murat Demirbas SUNY Buffalo

MAC LAYER. Murat Demirbas SUNY Buffalo MAC LAYER Murat Demirbas SUNY Buffalo MAC categories Fixed assignment TDMA (Time Division), CDMA (Code division), FDMA (Frequency division) Unsuitable for dynamic, bursty traffic in wireless networks Random

More information

CSE 461: Wireless Networks

CSE 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 information

MAC in /20/06

MAC in /20/06 MAC in 802.11 2/20/06 MAC Multiple users share common medium. Important issues: Collision detection Delay Fairness Hidden terminals Synchronization Power management Roaming Use 802.11 as an example to

More information

CMPE 257: Wireless and Mobile Networking

CMPE 257: Wireless and Mobile Networking CMPE 257: Wireless and Mobile Networking Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 3 CMPE 257 Winter'11 1 Announcements Accessing secure part of the class Web page: User id: cmpe257.

More information

Mohamed Khedr.

Mohamed Khedr. Mohamed Khedr http://webmail.aast.edu/~khedr Tentatively Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14 Week 15 Overview Packet Switching IP addressing

More information

Wireless Medium Access Control Protocols

Wireless 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 information

The MAC layer in wireless networks

The 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 information

Lecture 4: Wireless MAC Overview. Hung-Yu Wei National Taiwan University

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 information

CSE 461: Multiple Access Networks. This Lecture

CSE 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 information

Random Assignment Protocols

Random 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 information

Computer Communication III

Computer Communication III Computer Communication III Wireless Media Access IEEE 802.11 Wireless LAN Advantages of Wireless LANs Using the license free ISM band at 2.4 GHz no complicated or expensive licenses necessary very cost

More information

ICE 1332/0715 Mobile Computing (Summer, 2008)

ICE 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 information

SENSOR-MAC CASE STUDY

SENSOR-MAC CASE STUDY SENSOR-MAC CASE STUDY Periodic Listen and Sleep Operations One of the S-MAC design objectives is to reduce energy consumption by avoiding idle listening. This is achieved by establishing low-duty-cycle

More information

Multiple Access Links and Protocols

Multiple 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 information

Data Communications. Data Link Layer Protocols Wireless LANs

Data Communications. Data Link Layer Protocols Wireless LANs Data Communications Data Link Layer Protocols Wireless LANs Wireless Networks Several different types of communications networks are using unguided media. These networks are generally referred to as wireless

More information

High Level View. EE 122: Ethernet and Random Access protocols. Medium Access Protocols

High 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 information

ECEN 5032 Data Networks Medium Access Control Sublayer

ECEN 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 information

MAC protocols. Lecturer: Dmitri A. Moltchanov

MAC protocols. Lecturer: Dmitri A. Moltchanov MAC protocols Lecturer: Dmitri A. Moltchanov E-mail: moltchan@cs.tut.fi http://www.cs.tut.fi/kurssit/tlt-2616/ OUTLINE: Problems for MAC to deal with; Design goals; Classification of MAC protocols Contention-based

More information

Wireless Communications

Wireless 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 information

Multiple Access in Cellular and Systems

Multiple Access in Cellular and Systems Multiple Access in Cellular and 802.11 Systems 1 GSM The total bandwidth is divided into many narrowband channels. (200 khz in GSM) Users are given time slots in a narrowband channel (8 users) A channel

More information

EE 122: Ethernet and

EE 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 information

ECE 4450:427/527 - Computer Networks Spring 2017

ECE 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 information

CMPE 257: Wireless and Mobile Networking

CMPE 257: Wireless and Mobile Networking CMPE 257: Wireless and Mobile Networking Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 3 CMPE 257 Spring'15 1 Next week Announcements April 14: ICN (Spencer Sevilla) April 16: DTN

More information

Rahman 1. Application

Rahman 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 information

15-441: Computer Networking. Wireless Networking

15-441: Computer Networking. Wireless Networking 15-441: Computer Networking Wireless Networking Outline Wireless Challenges 802.11 Overview Link Layer Ad-hoc Networks 2 Assumptions made in Internet Host are (mostly) stationary Address assignment, routing

More information

Chapter 4. The Medium Access Control Sublayer. Points and Questions to Consider. Multiple Access Protocols. The Channel Allocation Problem.

Chapter 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 information

IEEE , Token Rings. 10/11/06 CS/ECE UIUC, Fall

IEEE , Token Rings. 10/11/06 CS/ECE UIUC, Fall IEEE 802.11, Token Rings 10/11/06 CS/ECE 438 - UIUC, Fall 2006 1 Medium Access Control Wireless channel is a shared medium Need access control mechanism to avoid interference Why not CSMA/CD? 10/11/06

More information

IEEE Medium Access Control. Medium Access Control

IEEE Medium Access Control. Medium Access Control IEEE 802.11 Medium Access Control EECS3214 3 April 2018 Medium Access Control reliable data delivery access control MAC layer covers three functional areas: security 2 1 MAC Requirements To avoid interference

More information

CMPE 257: Wireless and Mobile Networking

CMPE 257: Wireless and Mobile Networking CMPE 257: Wireless and Mobile Networking Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 4 1 Announcements Project proposals. Due April 17 th. Submit by e-mail to katia@soe.ucsc.edu.

More information

6.9 Summary. 11/20/2013 Wireless and Mobile Networks (SSL) 6-1. Characteristics of selected wireless link standards a, g point-to-point

6.9 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 information

CHAPTER 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 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 information

Embedded Internet and the Internet of Things WS 12/13

Embedded Internet and the Internet of Things WS 12/13 Embedded Internet and the Internet of Things WS 12/13 4. MAC Protocols Prof. Dr. Mesut Güneş Distributed, embedded Systems (DES) Institute of Computer Science Freie Universität Berlin Prof. Dr. Mesut Güneş

More information

Outline. 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 Outline Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties Layered Network Architectures - OSI framework descriptions of layers

More information

G 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 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 information

CSE/EE 461 Wireless and Contention-Free Protocols

CSE/EE 461 Wireless and Contention-Free Protocols CSE/EE 461 Wireless and Contention-Free Protocols Last Time The multi-access problem Medium Access Control (MAC) sublayer Random access protocols: Aloha CSMA variants Classic Ethernet (CSMA/CD) Application

More information

Data and Computer Communications. Chapter 13 Wireless LANs

Data and Computer Communications. Chapter 13 Wireless LANs Data and Computer Communications Chapter 13 Wireless LANs Wireless LAN Topology Infrastructure LAN Connect to stations on wired LAN and in other cells May do automatic handoff Ad hoc LAN No hub Peer-to-peer

More information

Wireless Local Area Networks. Networks: Wireless LANs 1

Wireless Local Area Networks. Networks: Wireless LANs 1 Wireless Local Area Networks Networks: Wireless LANs 1 Wireless Local Area Networks The proliferation of laptop computers and other mobile devices (PDAs and cell phones) created an obvious application

More information

Strengthening Unlicensed Band Wireless Backhaul

Strengthening Unlicensed Band Wireless Backhaul be in charge Strengthening Unlicensed Band Wireless Backhaul Use TDD/TDMA Based Channel Access Mechanism WHITE PAPER Strengthening Unlicensed Band Wireless Backhaul: Use TDD/TDMA Based Channel Access Mechanism

More information

MSIT 413: Wireless Technologies Week 8

MSIT 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 information

Media Access Control in Ad Hoc Networks

Media Access Control in Ad Hoc Networks Media Access Control in Ad Hoc Networks The Wireless Medium is a scarce precious resource. Furthermore, the access medium is broadcast in nature. It is necessary to share this resource efficiently and

More information

Chapter 3 MEDIA ACCESS CONTROL

Chapter 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 information

Lecture 6. Data Link Layer (cont d) Data Link Layer 1-1

Lecture 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 information

1-1. Switching Networks (Fall 2010) EE 586 Communication and. November 8, Lecture 30

1-1. 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 information

Announcements / Wireless Networks and Applications Lecture 9: Wireless LANs Wireless. Regular Ethernet CSMA/CD.

Announcements / Wireless Networks and Applications Lecture 9: Wireless LANs Wireless. Regular Ethernet CSMA/CD. Announcements 18-452/18-750 Wireless Networks and Applications Lecture 9: Wireless LANs 802.11 Wireless Peter Steenkiste Homework 1 should be out by tomorrow Project 1 by Friday Schedule:» Thursday lecture

More information

Topics. Link Layer Services (more) Link Layer Services LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS. flow control: error detection:

Topics. 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 information

Lecture 16: QoS and "

Lecture 16: QoS and Lecture 16: QoS and 802.11" CSE 123: Computer Networks Alex C. Snoeren HW 4 due now! Lecture 16 Overview" Network-wide QoS IntServ DifServ 802.11 Wireless CSMA/CA Hidden Terminals RTS/CTS CSE 123 Lecture

More information

Medium Access Control

Medium 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 information

Wireless & Mobile Networking

Wireless & Mobile Networking Wireless & Mobile Networking CS 752/852 - Spring 2011 Lec #3: Medium Access Control - I Tamer Nadeem Dept. of Computer Science Data Link Layer (DLL) Main Task of the data link layer: Provide error-free

More information

Physical Layer. Medium Access Links and Protocols. Point-to-Point protocols. Modems: Signaling. Modems Signaling. Srinidhi Varadarajan

Physical 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 information

NMA Radio Networks Network Level: Medium Access Control Roberto Verdone

NMA Radio Networks Network Level: Medium Access Control Roberto Verdone NMA Radio Networks Network Level: Medium Access Control Roberto Verdone Outline 1. Introduction 2. Fundamentals of Random MAC Aloha in Compact Networks Slotted Aloha in Compact Networks CSMA in Compact

More information

MAC 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 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 information

MAC. Fall Data Communications II 1

MAC. Fall Data Communications II 1 802.11 MAC Fall 2005 91.564 Data Communications II 1 RF Quality (ACK) Fall 2005 91.564 Data Communications II 2 Hidden Terminal (RTS/CTS) Fall 2005 91.564 Data Communications II 3 MAC Coordination Functions

More information

Chapter 6 Medium Access Control Protocols and Local Area Networks

Chapter 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 information

Computer Network Fundamentals Spring Week 3 MAC Layer Andreas Terzis

Computer 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 information

Wireless Local Area Networks (WLANs)) and Wireless Sensor Networks (WSNs) Computer Networks: Wireless Networks 1

Wireless Local Area Networks (WLANs)) and Wireless Sensor Networks (WSNs) Computer Networks: Wireless Networks 1 Wireless Local Area Networks (WLANs)) and Wireless Sensor Networks (WSNs) Computer Networks: Wireless Networks 1 Wireless Local Area Networks The proliferation of laptop computers and other mobile devices

More information

Logical Link Control (LLC) Medium Access Control (MAC)

Logical 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 information

MULTIPLE ACCESS PROTOCOLS 2. 1

MULTIPLE 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 information

COMPUTER NETWORKS - Local area networks

COMPUTER 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 information

Local area networks. Copyright

Local 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 information

Redes de Computadores. Medium Access Control

Redes 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 information

Medium Access Control. IEEE , Token Rings. CSMA/CD in WLANs? Ethernet MAC Algorithm. MACA Solution for Hidden Terminal Problem

Medium Access Control. IEEE , Token Rings. CSMA/CD in WLANs? Ethernet MAC Algorithm. MACA Solution for Hidden Terminal Problem Medium Access Control IEEE 802.11, Token Rings Wireless channel is a shared medium Need access control mechanism to avoid interference Why not CSMA/CD? 9/15/06 CS/ECE 438 - UIUC, Fall 2006 1 9/15/06 CS/ECE

More information

Link Layer and LANs 안상현서울시립대학교컴퓨터 통계학과.

Link 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 information

Wireless Networks (CSC-7602) Lecture 6 (08 Oct. 2007) Seung-Jong Park (Jay) Wireless MAC

Wireless Networks (CSC-7602) Lecture 6 (08 Oct. 2007) Seung-Jong Park (Jay)  Wireless MAC Wireless Networks (CSC-7602) Lecture 6 (08 Oct. 2007) Seung-Jong Park (Jay) http://www.csc.lsu.edu/~sjpark 1 Wireless MAC 2 1 Wireless MAC CSMA as wireless MAC? Hidden and exposed terminal problems make

More information

Data Link Layer Technologies

Data 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 information

Local Area Networks NETW 901

Local Area Networks NETW 901 Local Area Networks NETW 901 Lecture 4 Wireless LAN Course Instructor: Dr.-Ing. Maggie Mashaly maggie.ezzat@guc.edu.eg C3.220 1 Contents What is a Wireless LAN? Applications and Requirements Transmission

More information

Wireless and Mobile Networks

Wireless and Mobile Networks Wireless and Mobile Networks 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

COMP/ELEC 429/556 Introduction to Computer Networks

COMP/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 information

Links Reading: Chapter 2. Goals of Todayʼs Lecture. Message, Segment, Packet, and Frame

Links Reading: Chapter 2. Goals of Todayʼs Lecture. Message, Segment, Packet, and Frame Links Reading: Chapter 2 CS 375: Computer Networks Thomas Bressoud 1 Goals of Todayʼs Lecture Link-layer services Encoding, framing, and error detection Error correction and flow control Sharing a shared

More information

Wireless and WiFi. Daniel Zappala. CS 460 Computer Networking Brigham Young University

Wireless and WiFi. Daniel Zappala. CS 460 Computer Networking Brigham Young University Wireless and WiFi Daniel Zappala CS 460 Computer Networking Brigham Young University Wireless Networks 2/28 mobile phone subscribers now outnumber wired phone subscribers similar trend likely with Internet

More information

04/11/2011. Wireless LANs. CSE 3213 Fall November Overview

04/11/2011. Wireless LANs. CSE 3213 Fall November Overview Wireless LANs CSE 3213 Fall 2011 4 November 2011 Overview 2 1 Infrastructure Wireless LAN 3 Applications of Wireless LANs Key application areas: LAN extension cross-building interconnect nomadic access

More information

ECE453 Introduction to Computer Networks. Broadcast vs. PPP. Delay. Lecture 7 Multiple Access Control (I)

ECE453 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 information

Outline / Wireless Networks and Applications Lecture 9: Wireless LANs Aloha and 802 Wireless. Regular Ethernet CSMA/CD

Outline / Wireless Networks and Applications Lecture 9: Wireless LANs Aloha and 802 Wireless. Regular Ethernet CSMA/CD Page 1 Outline 18-452/18-750 Wireless Networks and Applications Lecture 9: Wireless LANs Aloha and 802 Wireless Peter Steenkiste Data link fundamentals» And what changes in wireless Aloha Ethernet Wireless-specific

More information

CONTENTION BASED PROTOCOLS WITH RESERVATION MECHANISMS

CONTENTION BASED PROTOCOLS WITH RESERVATION MECHANISMS CONTENTION BASED PROTOCOLS WITH RESERVATION MECHANISMS Five-Phase Reservation Protocol A single-channel time division multiple access (TDMA)-based broadcast scheduling protocol. Nodes use a contention

More information

ECE 4450:427/527 - Computer Networks Spring 2017

ECE 4450:427/527 - Computer Networks Spring 2017 ECE 4450:427/527 - Computer Networks Spring 2017 Dr. Nghi Tran Department of Electrical & Computer Engineering Lecture 5.6: Wireless Networks - MAC Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527

More information

Wireless MACs: MACAW/802.11

Wireless MACs: MACAW/802.11 Wireless MACs: MACAW/802.11 Mark Handley UCL Computer Science CS 3035/GZ01 Fundamentals: Spectrum and Capacity A particular radio transmits over some range of frequencies; its bandwidth, in the physical

More information

CSE 461 Multiple Access. David Wetherall

CSE 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 information

original standard a transmission at 5 GHz bit rate 54 Mbit/s b support for 5.5 and 11 Mbit/s e QoS

original standard a transmission at 5 GHz bit rate 54 Mbit/s b support for 5.5 and 11 Mbit/s e QoS IEEE 802.11 The standard defines a wireless physical interface and the MAC layer while LLC layer is defined in 802.2. The standardization process, started in 1990, is still going on; some versions are:

More information

Announcements: Assignment 4 due now Lab 4 due next Tuesday Assignment 5 posted, due next Thursday

Announcements: Assignment 4 due now Lab 4 due next Tuesday Assignment 5 posted, due next Thursday ECE/CS 372 introduction to computer networks Lecture 15 Announcements: Assignment 4 due now Lab 4 due next Tuesday Assignment 5 posted, due next Thursday Credit for lecture slides to Professor Bechir Hamdaoui

More information

Wireless LANs. ITS 413 Internet Technologies and Applications

Wireless LANs. ITS 413 Internet Technologies and Applications Wireless LANs ITS 413 Internet Technologies and Applications Aim: Aim and Contents Understand how IEEE 802.11 wireless LANs work Understand what influences the performance of wireless LANs Contents: IEEE

More information

Wireless Sensor Networks 8th Lecture

Wireless Sensor Networks 8th Lecture Wireless Sensor Networks 8th Lecture 21.11.2006 Christian Schindelhauer schindel@informatik.uni-freiburg.de 1 Media Access Control (MAC) Controlling when to send a packet and when to listen for a packet

More information

Link Layer: Retransmissions

Link Layer: Retransmissions Link Layer: Retransmissions Context on Reliability Where in the stack should we place reliability functions? Application Transport Network Link Physical CSE 461 University of Washington 2 Context on Reliability

More information

MAC protocols for ad hoc networks

MAC protocols for ad hoc networks MAC protocols for ad hoc networks Lecturer: Dmitri A. Moltchanov E-mail: moltchan@cs.tut.fi http://www.cs.tut.fi/kurssit/tlt-2756/ OUTLINE: Problems for MAC to deal with; Design goals; Classification of

More information

Data Link Layer: Collisions

Data 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 information

CS/ECE 439: Wireless Networking. MAC Layer Road to Wireless

CS/ECE 439: Wireless Networking. MAC Layer Road to Wireless CS/ECE 439: Wireless Networking MAC Layer Road to Wireless Multiple Access Media Media access Controlling which frame should be sent over the link next Easy for point-to-point links; half versus full duplex

More information

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

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

More information

CSE 6811 Ashikur Rahman

CSE 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 information

Link Layer. (continued)

Link Layer. (continued) Link Layer (continued) Topics 1. Framing Delimiting start/end of frames 2. Error detection and correction Handling errors 3. Retransmissions Handling loss 4. Multiple Access 802.11, classic Ethernet 5.

More information

LECTURE PLAN. Script. Introduction about MAC Types o ALOHA o CSMA o CSMA/CD o CSMA/CA

LECTURE PLAN. Script. Introduction about MAC Types o ALOHA o CSMA o CSMA/CD o CSMA/CA Course- B.Sc. Applied Physical Science (Computer Science) Year- IIIrd, Sem- Vth Subject Computer Science Paper- XVIIth, Computer Networks Lecture -11 Lecture Title- Medium Access Layer Script Today in

More information

Telecommunication Protocols Laboratory Course. Lecture 2

Telecommunication Protocols Laboratory Course. Lecture 2 Telecommunication Protocols Laboratory Course Lecture 2 Last time We began our study of telecommunication protocols at the Logical Link Control sub-layer (LLC) LLC issues Connectionless vs connection-oriented

More information

Lecture 8 The Data Link Layer part I. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it

Lecture 8 The Data Link Layer part I. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Lecture 8 The Data Link Layer part I Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Link Layer: setting the context two physically connected devices: host-router, router-router,

More information

Multiple Access (1) Required reading: Garcia 6.1, 6.2.1, CSE 3213, Fall 2010 Instructor: N. Vlajic

Multiple 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 information