Classicl Film and Media Theory
Classicl Film and Media Theory FMS 864
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Date Created: 09/07/15
Media Access Control 9 Vlctor S Fro st Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 Phone 785 8644833 FAX7 5 8647789 email frosteecs uedu httpwwwittckuedu Chapter 6 Outline Why use MAC protocols General classes of MAC protocols gt Deterministic gt Random Access Standard LAN protocols Broadband Access gt Cable Media Access Control Protocols provide I Direct access to the media I Control over resource allocation I Typically broadcast real or Virtual MAC 3 Media Access Control Advantages I High data rates open new applications I Low cost I Local organizational control I Wireless is a broadcast media and efficient use of resources is important I Mobility Via Wireless I Enable sharing of resources MAC 4 Media Access Control I MAC protocols establish a set of rules that govern who gets to use the shared transmission media in an efficient manner I Obstacle to perfect channel utilization gt Finite propagation delay means that each users knowledge of the state of the system is imperfect and thus they can not perfectly schedule transmissions ie some time will be wasted attempting to learn the state of the system and or learning the fate of transmissions Media Access Control I Perfect Knowledge would lead to FIFO performance I Performance of MAC protocols will be to FIFO MMl1 Delay Ideal MAC E Performance 3 Impact of MAC Overhead ETEX MAC Protocol 2 MAC Protocol 1 Transfer Delay 1 Load Pym 1 Pam 2 l p Adapted mm LeuanarnactWidjaja Commumcmtan Narwoyh MAC 7 Alternative Media Access Control Strategies I Static Allocation gt FDM gt TDM I Problems gt Management not easy to add users Requires signaling gt Wasteful in resources for bursty traffic I Example gt A transmission media has a rate of 10 Mbs and supports 50 users The system uses static allocation A user has a 1 Mbyte le to transmit The file transfer time is 1x105 xsbit 40 sec 107 bits sec 5 0 MAC 8 Alternative Media Access Control Strategies I Suppose you send a message to all the other 49 users saying I need the whole Channelfor about Isec do not use it please I As long as the overhead incurred in sending the message is less than 39 sec the user will get better performance MAC 9 Alternative Media Access Control Strategies I Deterministic gt Polling gt Token networks I Random Access gt ALOHA gt Carrier sense multiple access CSMA gt CDMA with collision detection MAC 1 0 Alternative Media Access Control Strategies Dynamic allocation of resources I Deterministic Polling Token Ring ampTollten Bus I Advantage the maximum time between users chances to transmit is bounded assuming a limit on the token holding time I Disadvantage Time is wasted polling other users if they have no data to send I The technology does not scale MAC Deterministic Protocols I Roll Call Polling gtMaster slave arrangement gtMaster polls each node Do you have data to send gtIf the polled node has data it is sent otherwise next node is polled MAC 1 2 Deterministic Protocols Gm MAC 1 3 Deterministic Protocols I Hub Polling gt No master station gt Each nodes polls the next node in turn MAC 1 4 Deterministic Protocols v vvvvv v Example nodes 10 Link rate 1 Mbs Packet Size 1000 bits Assume Low load 9 no queuem 01 ms between nodes 30 krnleOBms 01ms Find the effective transmission rate and ef ciency 7 On average destination is 5 nodes away a 5 r Timeto ansmithOO its05ms lms 1 5ms 7 Effective transmission rate 1000 bits 1 5 ms 666Kbs 7 Ef ciency 666 Kbs1000 Kbs 0 66 Repeat for link rate 10 Mbs 7 0 average destination is 5 nodes away a 5 ms 7 Time to ansmithOObits 05ms 1 ms 6ms 7 Effective transmission rate 1000 bits 6 ms l 67 Mbs 7 Ef ciency 1 a7 Mbs10 Mbs 16 7 gt Conclusion9 Polling does not scale with link rate MAC 1 5 Alternative Media Access Control Strategies Random Access l Each node sends data with limited coordination between users No explicit permission to transmit I Total chaos Send data as soon as ready I Limited chaos Listen before sending data if the channel is busy do not send I Further Limiting chaos Listen before sending data continue listening after sending and if collision with another transmission stop sending Carrier Sense Multiple Access with Collision Detection ACDl CSM MAC 16 Alternative Media Access Control Strategies Random Access I Advantage Simple I Disadvantage gtNo guarantee that you will ever get to send gtThe MAC protocol technology does not scale MAC 1 7 Random Access Protocols Assumptions l Overlap in time and space of two or more transmissions causes a collision and the destruction of all packets involved No capture effects I One channel I For analysis no station buffering MAC 1 8 Random Access Protocols Assum tions I TimeAlternatives gt Synchronization between users Slotted time gt No synchronization between users unslotted time I Knowledge of the channel state Alternatives gt Carrier sensing gt Collision detection MAC 1 9 Random Access Protocols Strategies I Aloha gt No coordination between users gt Send a PDU wait for acknowledgment if no acknowledgment ASSUME collision then M and try again I Backoff gt Select random tilne to attempt another transmission I Slotted Aloha gt Same as Aloha only tiIne is slotted MAC Random Access Protocols Strategies I p persistent CSMA gt Listen to channel on transition from busy to idle transmit with probability p gt After sending the PDU wait for acknowledgment if no acknowledgment then backoff and retransmit gt Non persistent if channel busy then reschedule transmission gt 1 persistent Transmit as soon as idle MAC Random Access Protocols Strategies I CSMA CD gt1persistent but continue to sense the channel if collision detected then stop transmission gtCSMACD is used in 10 100 Mbs and 1 Gbs Ethernet MAC Limitations on Random Access Protocols I Distance gt Time to learn channel state 9 Propagation time I Speed gt Time to learn channel state 9 Clocking speed MAC Random Access Protocols Analysis ofAIoha I Goal Find Smax I Protocol Operation gt Packet of length L sec arrives at station 139 Stationi transmits immediately Stationi starts an acknowledgment timer gt If no other station transmits while 139 is transmitting then success gt Else a collision occurred gt Station 139 learns that a collision occurred if the acknowledgment tilner fires before the acknowledgment arrives MAC Random Access Protocols Analysis ofAIoha gt If collision detected then stationi retransmitts at a later time this time is pseudorandom and is determined by a backoff algorithm I Design Issue gt Determine the maximum normalized throughput for an Aloha system MAC Random Access Protocols Analysis ofAIoha Assumptions 1 Average number of new message arrival to the system 2 A Average number arrivals to the system ie new arrivals retransmissions 3 The total arrival process is Poisson 4 Fixed Length Packets S 2L 3 l S throughpul MAC Random Access Protocols Analysis ofAIoha Collision Mechanism Arrival Arrival Arrival I I 39 39 39 39 39 39 39 39 39 quot I I l I Target Packet 1 I 2L Target packet is vulnerable to collision for 2L Sec MAC Random Access Protocols Analysis of Aloha Probability of Collision l Probno arrivalsin 2L sec l e39ZLA But AZAle392m Let Delay G AL Offeredload S AL Then GsG1 e39 orsGe39ZLA I Find Smax 0whenGlorsmio18 Z dG 2 26 The Maximum throughput for Aloha is l 8 Loid 0 18 Random Access Protocols Analysis of Slotted Aloha TargelPackel Synchronization reduces the vulnerable period from 2L to L so the maximum throughput is increases to 36 MAC Random Access Protocols Performance of Unslotted and Slotted Aloha 8 E g 03940 Slotted ALOHA s Ge G E 030 7 8 E 020 W s l a l g 03910 7 i E l E l l l 0 05 10 15 20 30 G attempts per packet time m CamputerNetwarksSxdEdmanAS TanEnbaum MAC Fm Prentice Hall1996 Random Access Protocols CSMA Protocols I Listen to the channel before transmitting to reduce the vulnerable perio Let D maximum distance between nodes m Let R the transmission rate b s Let c speed of light 3 x 108 ms The propagation tilne D kc39c sec k is a constant for the physical media k 66 for fiber k88 for coax Example 1 km Free space propagation time 333 us Fiber propagation time 505 us Coax propagation time 379 us Random Access Protocols CSMA Protocols I Assume node A transmits at time tand node B at t x where x 9 0 That is Node B transmits right before it hears A I If after 2D kc sec no collision occurred then none will occur I Let a E LD kc L normalized length of the bus I Remember Lsec Packet Length bits R b s I As a gt 1 CSMA performance approaches Aloha performance MAC Random Access Protocols CSMA Protocols I Limits on a gt Want a small to keep vulnerable period short by having Short bus a DRXkc Lower speeds W ere Long Packets X packet length in bits Rumimean mm 5 mm mm upper boun I Lower limit Minimum packet length to NM cl a l Maximum packet length to be fair MAC 33 Random Access Protocols Performance o 5parsistent CSMA Slotted ALOHA 1persistem 3 4 5 e o anempts per packet llme me quotComputerNetwurksSrd Edition A s Tanenbaum Prentice Hall 1996 Nonpersisiem 05m 0 Olpersislem CSMA 017perslstent CSMA Random Access Protocols Performance Non ersistentCSMA me Leuanarna Wham Commumcmton Mama 4 001 MAC 35 Random Access Protocols CSMA Protocols I Example Ethernet gt Rate 100 Mbs gt Minilnum packet size 512 bits gt Maxilnum packet size 12144 bits gt D max per segment 500 In gt a gt 0001 003 I CSMA networks do not scale gt Increase D performance degrades gt Increase R performance degrades MAC 36 Random Access Protocols CSMA Protocols States Contention 0 slots m D J H Tia SmISSlOH Contention idle period eriod period TimeI 4 mm CamputerNetwarksSmEdman A s Tanenbaum Frenucenaimgge MAC 37 Collision Free Protocols I Collision free protocols establish rules to determine which stations sends after a successful transmission I Assume there are N stations with unique addresses 0 t0 N 1 I A contention interval is a period after a successful transmission that is divided into N time slots one for each station MAC 38 Collision Free Protocols I If a station has a PDU to send it sets a bit to 1 in its time slot in the contention interval I At the end of the contention interval all nodes know who has data to send and the order in which it will be sent a Contention slots Frames 5 Contention slots A I 1 Me 0H 01234567 01234567 01234567 IIIIIII m IIIIII MAC 39 Collision Free Protocols I Problems gtFaimess gtFlexibility I Many systems use the basic approach of collision free protocols MAC 40 Polling vs Random Access Performance mwuxm as 1qu m 41 Standard LANs IEEE 8023 10 Mbs gt CSMACD gt BasEband IEEE 8024 up to 10Mbs TokEn Bus Modulatg IEEE 8025 4 and 16 Mbs gt TokEnnng BasE a I IEEE 80211 ereless LAN 11 Mbs m 42 Standard LANs FDDI CDDI 100 Mb 5 gt Token Ring gt Fiber Distributed Data Interface gt Copper Distributed Data Interface gt Baseband IEEE 80212 100 Mbs gt Demand priority IEEE 80216 Wireless local loop or Wireless MAN Other IEEE 802xx Protocols Cable Modem Data over Cable Service Interface Specification DOCSIS MAC Standard LANs Network Layer IEEE 8023 IEEE 8022 IEEE 8024 Medium Access Control Ph sical La er V Y IEEE 80211 IEEE 8022 Logical Link Control IEEE 80212 IEEE 80216 Protocol Others MAC Ethernet I Unslotted 1 persistent CSMA CD I Procedure gt Frametotransmit and idle wait interfmmegap transmit gt Listen to channel and if collision stop sending send jam signal schedule retransmission MAC Ethernet Schedule retansmission the binary exponential backoff algorithm I N N1 where N number of retransmission attempts I If N gt attempt limit then trash the PDU else calculate the backoff tilne k MinN backo ilimit R Uniform 0 2k retransmit at time tnow Rslottime MAC Ethernet Parameters I Slot time 512 bit times I lnterframe gap 96us I Attempt limit 16 I Backoff limit 10 I Jam time 32 bits rate I Maximum frame size 81518 bits I Minimum frame size 864 bits MAC Ethernet Packet structure 8023 MAC Frame gt 1518 Bytes 7 1 6 6 2 4 Destination Source Inf t1 P d FCS Preamme SD Address Address Lengthi Grim on a Synch Start fr 1A23F9CD 069B 46 to 1500 bytes Preamble 7 bytes of 10101010 Start Of Frame 1 byte thus 1010101 1 Source and Destination Address Each 6 bytes and are globally unique Type field In 8023 this field gives the length in bytes of the data field Data field From 46 to 1500 bytes MAC 48 Ethernet Typical Con gurations Bus Hub I MAC SWItch ed Ethernet Swwtch Connemor To hos s 8023 LAN Hub To hosts To hosts 100Base TX A A g P or TOBaseTy Angh Speed Interface GlgE connection To the host compmers From Computer Networks 3rd Edman A s Tanenbaum PrenhteHall 1996 MAC 50 Gigabit Ethernet Goals I Allows half and full duplex operation at speeds of 1000 Mb s Uses the 8023 Ethernet frame format Can use the CSMA CD access method with support for one repeater per collision domain Half duplex I Common use is with Gigabit Ethernet switches in Full duplex mode gt No CSMA CD I Addresses compatibility with 10 Mb s 100 Mb s and 10 Gigabit Ethernet technologies From Whitepaper Gigabit Ethernet Overmew MAC mm t u Ma 1 technologyWhitepapers 51 Gigabit Ethernet Distance Objectives I Multimode fiber optic link with a maximum length of 550 meters I Single mode fiber optic link with a maximum length of 3 kilometers I Optical links based on Fiber channel technology I Copper based link with a maximum length of at least 25 meters I Category 5 unshielded twisted pair UTP wiring link 100 meters From Whitepaper Gigabit Ethernet Overmew MAC mm t u Ma 1 technologyWhitepapers 52 Gigabit Ethernet Possible Application Innman Svildx Ennbii MW mm iulilwi uuuuuua 039 n a n iu mr ii ion Mlzps iD Mimi I law In MIin in mm rnd Um Cumwciiuus me wmgpaper GigabxtEthemetOvemew MAC 53 GigabxtEthemetAlhame May17htlt Evolution of Ethernet Technology 10 M 100 M 1 G 10 G ChL m y W F Kim MAC Central arms tin MAC 0mm I Frame Control i I Rm mm m il ulnaw m u w Hnlmmv Im mm mm 551mm in EMS xequemzms amp mhnzcmre h plgmnpex 1m mggmpsxnzmmc I may nit Vision Ethernet EndtoEnd E Campus LAN 39I MAC 55 Definitions of Network Elements I Repeaters I Bridges I Switches I Routers gt Routing gt Forwarding MAC 56 Repeaters amp Bridges I Repeaters forwards electrical signals from one Ethernet to another I Bridges sometimes called hubs gt Interconnects multiple access LANs to form Extended LANs gt Only forwards frames destined for other LANs gt Link layer forwarding based on MAC address gt Bridges are devices that forward link level frames from one physical LAN to another MAC Switches amp Routers gt Switches Forwards packets Star topology New hosts can be added without degrading the performance of the existing hosts Scales b adding additional switches i supported by the switch fabric gt Routers amp Gateways Forwards packets Interconnects two or more networks Forwardin 9 takecpacket from input port then use routing tab e to n an output port then forward packet to that port Routing9 process of filling in the routing table MAC Switches amp Routers I Layer 2 switching is performed by looking at a destination MAC address within a frame Layer 2 switching builds and maintains a switching table that keeps track of which MAC addresses belong to each port or interface gt Ethernet switches gt ATM Switches MAC Switches amp Routers I Layer 3 switching routers operates at the network layer It examines packet information and forwards packets based on their network layer destination addresses gt IP Switches I Layer 4 Switching operates at the transport layer makes forwarding decision based on IP address and TCPUDP application port gt Gateways Firewalls lPSec Policy Based Networks PBN Directory Enabled Networks DEN MAC Token Ring EEE8025 I Hub polling I Requires procedures for gt Ring maintenance gt Lost tokens gt Multiple tokens gt Add delete user I Priority operation I Single token operation ie one station has permission to send I Source removes data and pass on token 61 MAC Token Ring EEE8025 Node A transmits packets 62 MAC Token Ring EEE8025 Node A transmits packets MAC Token Ring EEE8025 lSource node captures token lSource node transmits frames lSource node receives transmitted frames lSource node releases generates token MAC Token Bus IEEE 8024 I Physical bus 1Mb s 5 Mb s and 10 Mbs I Logical ring I Broadband ie token bus requires high speed modems I Token bus is compatible with cable systems I Priority operation MAC 65 Token Bus IEEE 8024 I r This station quot W quotquotquotquot quot 7 notcurremlyin 7 11 19 the logical ring Dlrec Ion of token motion mm quotCampus Networks am am A s Tmnbaum mm Hall1996 MAC 66 FDDI Fiber Distributed Data Interface I High speed network interface 100 Mb s I Uses 413 SB coding gt Maps each 4 bits of data into a 5 bit pattern for transmissioneg 1111 gt 11101 gt Line rate is 125 M symbolss I Priority operation is the similar to the token bus C erne I Multiple token ie multiple stations have permission to send at the same time MAC FDDI Multiple token operation CDDI MAC FDDI Fault Recovery Using Dual Rings A Ring architectures are common in WANs to insure network reliability mm quotmm mm m mum As mam p MAC 69 renuneHdLWQE Wireless Networking I Some general problems gt Noise gt Hidden Terminal 7 B Hears A r B Hears C r Ccannothear A TerminalB 1quot MAC 70 Vi reless Networking Some problems continued I Average received signal strength gt Falls off with distance over transmission medium gt Is a function of Scattering I Changing received signal strength 9 Signal fading r Mobility MAC 71 Propagation mechanisms R Reflec i39ion S5caffering D Diffraction Mm Andlrsan 1 WWW undVashdu 5 i m MAC 72 1mm Propagation Effects l Signal strength at a distance Varies due to Multipath l Large scale models predicts the average signal strength x u u m u 9 ine mm mm w smumgs Wml l Small scale fading o l characterize the short term uctuations 9 Black line MAC 73 IEEE 80211 I Form of a packet radio network I Must deal with the hidden terminal problem I Physical layer gt Frequency Hopping Spread Spectrum gt Direct Sequence Spread Spectrum gt Infrared MAC 74 IEEE 80211 I MAC Carrier Sense Multiple Access with Collision Avoidance CSMA CA gt Sense channel if idle the send9Request to Send RTS PDU gt Receiver responds with a 9Cleur to Send CTS PDU If receive CIS then all other nodes know the channel is captured and will not send original sources sends without collision If RTS PDUs collide then use random access backoff algorithm gt RTSCTS deals with the hidden terminal problem I Access Points AP are the wireless wired gateways V V MAC 80211a 80211a supports mandatory data rates of 6 12 and 24 Mbps Optional data rates of 9 18 36 and 54 Mbps Operates in 5GHZ UNH Unlicensed National Information Infrastructure band Occupies 300 MHZ in three different bandwidths of 100 MHZ each5150 to 5250 GHZ UNH lower band5250 to 5350 GHZ UNJI middle band5725 to 5825 GHZ UNH upper band80211a provides 12 channels each channel being 20 MHZ wide and each centered at 20 MHZ intervals beginning at 5180 GHZ and ending at 5320 GHZ for the upper and middle UNH bands beginning at 5745 GHZ and ending at 5805 GHZ for the upper UNll band It is important to note that none of these channels overlap 80211a uses OFDM Orthogonal Frequency Division Multiplexing with multiple carriers aka quotsubcarriersquot per channel MAC 80211bWiFi Supports data rates of 1 2 55 and 11 Mbps Operates in the 24GHZ ISM Industrial Scienti c and Medical band Occupies 835 MHZ for North America from 24000 GHZ to 24835 GHZ 80211b provides 11 channels for North America each channel being 22 MHZ in width and each channel centered at 5 MHZ intervals beginning at 2412 GHZ and ending at 2462 GHZ This means that there are only 3 channels which do not overlap channels 1 6 11 80211b uses DSSS Direct Sequence Spread Spectrum with a single carrier per channel Both 80211b and 80211a use the 80211 MAC both use CSMA CA to listen before transmitting on a given channel to avoid colliding with another transmitter by sensing if the channel is occupied MAC 80211g I A physical layer standard for WLANs in the 24GHZ and 5GHZ radio I The maximum link rate is 54Mbps per channelcompared with 11 Mbps for 11b 80211g standard uses orthogonal frequencydivision multiplexing OFDM modulation but for backward compatibility with 11b it also supports complementary code keying CCK modulation and as an option for faster link rates allows packet binary convolutional coding PBCC modulation Speeds similar to 11a and backward compatibility may appear attractive Advantageprovides ability for dualmode 24GHZ and 5GHZ products in that using OFDM for both modes to reduce silicon cost MAC 80211e l Supplementary to the MAC layer to provide COS support for LAN applications I Applies to 80211 physical standards a b and g l 80211e provides some features for differentiating data traffic strearns l Man WLAN manufacturers have targeted CoS as a feature to differentiate their products so there will be plenty of proprietary offerings before He is ornplete MAC 79 Broadband Access Technologies Cable Modems High rmm 9 n n m w a WW s M mm a u ai 3E FDM on the Cable From ComputErNEtworks 3rd Edition AS MAC 80 Tamnbaum man Hall1996 Broadband Access Technologies Cable Modems Comparison Modem Network amp Cable Modem un1imited distance 50 kbib39s Max 1 km 101110 Mbiis gaaaaaaa Cable Modem SW0quot eg 10 m 4750 Mbstfs am HeadvEn d mas mkwp mama sum 12 cwkmmpc Minna kayak MAC From httpwwwcablemodemsorgtuto al Generic Hybird Fiber Coax HFC Distribution Plant Coaxiai Distribution Fiber Distribution Fiber Node Dismu inn Ampimer 500 to 2000 Homes Served 100000 a 500000 A Homes 0 000 served to 100 000 Homes Sened Customer Premise M AC From Data Over Cable Service Interface 39 39 nnm TF39ampi Broadband Access Technologies Cable Modems Terms I CMTS Cable Modem Termination System Central device for connecting the cable TV network to a data network like the inteI net Normally placed in the headend of the cable TV system Downs eam Headend Central distribution point for a CATV system Video 39nwl qr r 39 ah mm ntllit A L w t ere T sources frequency converted to the appropriate channels combined with locally originated signals and rebroadcast onto e ant Upstream The data owing from the Cable Modem to the CMTS I Downstream The data owing from the CMTS to the cable mo dem MAC 83 Data Rates DOCSIS 1011 Nomtnal nocsls Downstlealn Data Rate ln BMHZ Channel IMauumtma type M 255 cm Symbol rate 5n57 M55 5 360 M55 mat dnxo rate 30 34 Mbps 2 9 Mbps Etlecllve data rate 27 Mbps as Mhps Nominal DOCSIS U slveam Dala Hate to oPsK awlttm 2m kHl 400 kHz mm kHz 1600 km 32m kHz symncl rate 016 M55 012 M55 use M55 125 M55 255 M55 Total daz rate n 32 Maps 0 ea Mhps 12 Mbps 25a Maps 542 Mbps E ecllve data rate 03 Mbps neatst t2 les 2 minus 45 Mbps Nomtnal DOCSIS UQstvenm Data Rate 0 IE 0AM Band I ma kHz 00 m m 1600 m 3200 kttz Symbol rate ms M85 0 2 M55 054 M35 125 M35 255 MSs Total dam rate u at Mbps LZE Mbps 155 Mbps 52Mbps to 24 quotHips Etlocwe data rate 05 Mbps L2 Mbps 2 Mbps t5 Mbps 90 Mst Curriers limit down and upstream rates 29 New Zeulund operator Telstraclear prwides as of Sp ownstreum speeds of 10Mbits and 2Mbits upstream speed of zlvlbits MAC 84 DOCSIS Protocol Stack use came Modern H I I I I I Wmmmmw sew I quotW W m UDP UDP UDP IF ARP P ARP PARP mm 3 mm 3 23quot 1 Canvergence Sub ayer mquot u L Ime Mace between the MAC awr and 3 mm m m vmmr Medm Dependent Layer me Dr PHV Can a sa b2 Ethernetbemeen m2 Ha smug and Emma m usa cMcI MAC 85 Broadband Access Technologies Cable Modems Terms Headend controls all transmissions on the downstream Coaxra came Downstream Channe wihou canisrmon39 27 Mbps using OAMVSA and 134mm payloads Packet Upstream channel with contenhan 9 Mbps usmg OPSK and 573er mrmslms From ComputErNEtworks 3rd Edmon AS MAC 86 Tanenbaurn man Hall1996 Broadband Access Technologies Cable Modems Downstream data format ReedSolomon error correction Corrects 6 errors in 204 bytes MPEGTS Transport Stream WESPS Program Stream 39 MAC messages ATM cells lbwDAVIE Data addressed to one many or all Cable Modems MAC 87 Broadband Access Technologies Cable Modems Upstream data format ReedSolomon error correction Prepended unique wor One ATM cell per burst lbwDAVIE 39 MAC message or data as payload 18 timeslots per 3 ms lbwDAVIE Reserved timeslow for longer data Contention timeslot for small dam initiate Ranging timeslots are 3 slots MAC 88 Broadband Access Technologies Cable Modems What is MAC Media Access Control Implemented in HW and maybe some SW Performs ranging to calibrate TX level Performs ranging to calibrate time reference Assigns upstream frequency and datarate Allocates timeslots upstream bandwidth Runs on both Cable Modern and HeadEnd Very similar to satellim protocol Aggregate Data Rates shared by 500 to 2000 homes today MAC 89 DOCSIS MAC Data Over Cable Service Interface Speci cation DOCSIS A stream of minislots in upstream 5 containing 832 B es Dynamic mix of contention and reservationbased ies upstream transmit opportunit Quality of service includin gt Support ofBandwidth and Latency guarantees gt Packet classi cation gt Dynamic service establishment Extensions provided for security at data link layer Support of wide range of data rate 5 MAC 90 DOCSIS MAC I Upstream Bandwidth Allocation Protocol I MAP is a MAC management message transmitted by the CMTS in the downstream which describes the use of the next upstream mini slots up to 4096 I A MAP describes some slots as grants for particular stations to transmit data in some for contention transmission and some as an opportunity for new CMs to join the link MAC 91 DOCSIS MAC Downstream Mini 5 4 lllllllllllllllllllllllllll CM TX owommiw Maimenancc request contention Area MAC 92 Frnm Data Over Cable Servlce Interface ocsls M H M l 39 rpm Random Access and Reservations I Distributed systems Stations implement a decentralized algorithm to etermine transmission order eg reservation A oha I Centralized systems A central controller accepts requests from stations and issues grants to transmit gt Frequency Division Duplex FDD Separate frequency bands for upli k downlink gt TimeDivision Du lex TDD Uplink amp downlink timeshare the same frequency channelp I The centralized system is used in many access technologies eg gt DOCSIS gt lEEE 80216 gt Wideband code division Multiple access WCDMA High Speed Data Packet Access HSDPA Evolution from GSM gt CDMAZOOO 9 Evolution Data optimized EV DO Evolution from CDMA Adapted mm Leuanarna ampWidiaia Commumcmtan Namayi Reservation Systems i Reservation Frame int7rva transmis ions Upstream Transmissions W W W W W W W W Time lt Cycle n 7 Cycle n 1 I39quot l Minislo r I I Transmissions organized into cycles or frames I Cycle reservation interval frame transmissions I Reservation interval has a minislot for each station to request reservations for frame transmissions minislot can carry other information eg number of frame to TX station backlog channel quality indicator CQI Adapted mm Leuanarna ampWidiaia Commumcmtan Namayi MAC Reservation System I System Characteristics gt Asymmetric Upstream l Minislots with requests for resources I Access Minislots Via random access protocol Downstream I Accepts minislots and includes grants for transmission I Grants control the ow on the upstream link I Order of grants established Via a scheduling algroithm MAC g p I Let gt R Link rate bs gt L packet size bits gt v minislot size sec gt M Number of stations gt X LR sec I Assume gt Propagation delay lt X 9 Access network gt Heavy load 9 stations have packets to send gt All requests are granted gt One rninislot needed for each packetstation l Time to transmit M packets MVMX 7 W 7 1 max i V Mv W 1 X Adapted mm Leuanarna awmma Commumcmtan Narwoyh M AC Throughput I If k frame transmissions can be reserved with ONE reservation message and if there are M stations as many as M1lt frames can be transmitted in XMlltV seconds MM 1 5m 2 M V MkX V 1 Adapted mm Leuanarnacthdjaja Commumcmtan Narwoyh M AC Throughput with random access contention for Minislots I Real systems have too many nodes for each to get a fixed minislot I Therefore a random access protocol is used to transmit in a minslot gt A station attempts to obtain a grant by transmitting in a minslot in the upstream direction gt If successful the station will get the grant on the down stream gt If unsuccessful then assume collision backoff and retry MAC Throughput with random access contention for Minislots I Assume slotted Aloha is used for contention for minislots I On average each reservation takes at least 6 271 minislot attempts 3 4 1 X1ev 1271vX I Effect is just to make the minislots seem longer MAC DOCSIS MAC Best Effort DOCS S 1 0 Contention REQ cableModem All Cable Modems CMs Term39q 39siys39em Treated Equalty r i gas ago 1 i FIFO Scheduler A Grant IIrst Come First Served From DataDverCableServicelmer c MAC e Speci cations nocsn Mam hMannat rmer rpm DOCSIS MAC DOCSIS 11 Real Time Polling Mode Contention Low l REQ REQ Priority CMs From Data Overcable Service Inter ce MAC 101 Speci cations Docsl Mam hMannal mm TF39SJ DOCSIS MAC DOCSIS 11 Circuit Switched Emulation quotUnsolicited Grant Mode Q v Guaranteed Time Slots 99 every 20 msec CMTS Sends Periodic Grants Automatically Grant Grant V Grant Grant Grant From DataOvercableServicelmer ce MAC Speci cations Docsl Mam hMannal mm TF39SJ Evolution of DOCSIS I Embedded DOCSIS eDOCSIS device contains gtCM Functional Entities eSAFEs 7 Telephone 7 Digital video rec orders 7 Multiple TV tuners gt One or more embedded ServiceApplication MAC 103 Wireless broadband Internet IEEE 80216 mm um or 5mm 9mm m Mqu pnlnl lllll llll l39E IEEE 80216 protocol based on DOCSIS IEEE 80216e addresses mobility Digital Subscriber Line Physical topology Broadband Access Technologies DSL digital subscriber line I Not shared media I Point to point connection to network I ADSL Asymmetric DSL gt Downstream 15 Mbs 9 Mbs gt Upstream 16 kbs 640 kbs I HDSL High data rate DSL gt Downstream 15 Mbs 2 Mbs gt Upstream 15 Mbs 2 Mbs MAC 1 06 Broadband Access Technologies DSL digital subscriber line I VDSL 7 Very high dam rate DSL gt Downstream r 13Mbs r 52 Nib s gt Upstream r 15 Mb 5 r 23 Nibs I Glite of cially HUT standard G79922 gt Downstream e 1544Mbs to 6 Mbs gt Upstream e 128 Kbps to 384 Kbps gt Does not requrre splitting of the hue at the user end I DSLAM 7 digital subscriber line access multiplexer I Speed depends on distance from DSLAM max 18000 ft rm 107 Broadband Access Technoloies A From http www zdnet compccompfeaturesexd0198dsl rm Powerline Communications Access I What is it gt It 15 adata Communication technology that operates over the electricity supply gt Rates Mbs gt Last hop P awe 1mg 7 Wireless 802 11 t W Fm muve Wuvmatmn see Bluetooth I Bluetooth Harald Blaatand Bluetooth ll 940981 the Viking King who uni ed Denmark and Norway I Original Goal desk top cable replacement I Used to describe the protocol ofa short range 10 meter frequencyhopping radio link between devices gt devices are then termed Bluetooth 7 enabled cumentation on Bluetooth is split sections 7 Bluetooth Sped ca on 7 Bluetooth Pro les MAC 110 Bluetooth I The Specification describes how the technology works ie the Bluetooth protocol architecture I The Profiles describe how the technology is used ie how different parts of the specification can be used to fulfill a desired function for a Bluetooth device I Uses frequency hopping in 79 hops displaced by 1 MHZ starting at 2402GHZ and finishing at 2480GHZ I Data Rate lt 1Mb s For more details see MAC httpwwwpalowirelesscominfotoothtutorialasp RFID I Radio Frequency Identification Tags I Replacement for Barcode I Types gt Active like Kansas Turnpike K tag gt Passive I Need MAC when reading a group of products at once I Issues gt Cost gt Privacy MAC 112 Satellite Access I What it is Satellite access As of 2005 MAC 113 Nelson Environmental Study Area nk NESA V reless Data N 39 mam w 95 mm mm MAC 114 NESA HQ 7 Flux Tower Network H yparLiM HGZH sumo mranz mum z HNIODDS smamxa RomanMariam wme A islr Vlarvlv m NrsA no rauncan wnnues v 0 Williams lem 7 7 W wmtooe 39 Send to When New 5843214th In 302113quot pm Tmmv Ema server Flux Tm Imwtwun uESA Ha Emmi MAC 115 Satellite Link Bandwidth Tests mlSpeedTestFAQlSpEedTestHelp i 0315 u H owe r gt B R 0 A D E A N B spew l sl Speed 1135duwnll upkbps Reslzrl test Test History for Site ID 393585180139 July 25m 11 51AM loss207 kbps July 26m 1149AM 711081196 kbps Microso Remote Desktop was used to access the data server PC located in the NESA HQ building then intemet access bandwidth tests were initia ote Desktop has a si ni cant impact on the available bandwidth reported Typical numbers directly from the NESA site are 1440 kbps up 700 kbps dovm MAC 116 Satellite Networks I Properties gt Large delay 270 ms Geosynchronous gt Up and down links are on different frequencies full duplex I CSMA CD will not work because of long delay I Token networks are not applicable because of long delays eg 100 nodes will have a 27 sec token return time MAC 117 Satellite Networks Resenation ALOHA I Consider a slotted system with N slots per frame TDM like I Each slot can be in one of three states Empty ie not is use Mine ie in use by me Other ie in use by another node I Protocol If state is mine then continue to use it If state is other then do not send in that time slot If state is empty then contend for that slot using Aloha MAC 118 Satellite Networks I At low loads the network performs like a random access systems ie no waiting for permission to send I At high loads the systems performs like a TDM system I This scheme has a problem with fairness I Distributed assignment of time slots MAC 119 Satellite Networks I TDMA Time Division Multiple Access I Up stream stations request bandwidth time slots I Central controller grants requests for bandwidth I Central controller has global View of all requests I Centralized assignment of time slots MAC 120 Satellite Networks GEO IGeostationary earth orbit I 37700 km IPowergt increased cost I Propagation delay ILirnited orbital slots 180 2 degrees Satellite Networks MEO I Medium earth orbit I 5000 15000 km I Period 49 hours I Fewer satellites Satellite Networks LEO I Low earth orbit I 1500 km I Periods up to 2 hours I More satellites I Cheaper to launch
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