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ACCESS NETWORKING Dr. Prakash D. Vyavahare Dept. of Electronics & Telecomm.Engg. S. G. S. Inst. Of Tech. And Science, 23 Park Road, INDORE 452 003

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Presentation on theme: "ACCESS NETWORKING Dr. Prakash D. Vyavahare Dept. of Electronics & Telecomm.Engg. S. G. S. Inst. Of Tech. And Science, 23 Park Road, INDORE 452 003"— Presentation transcript:

1 ACCESS NETWORKING Dr. Prakash D. Vyavahare Dept. of Electronics & Telecomm.Engg. S. G. S. Inst. Of Tech. And Science, 23 Park Road, INDORE

2 Introduction PSTN access ISDN access VOIP Emergence of packet switching networks BB Access Technologies ADSL Conclusions Bibliography

3 Introduction Telecomm. Tech. Devp. (chronology) Telecomm. With Morse code First Telegraph in India (Cal.)1852 ITU established with 20 European countries1865 Trans-Atlantic cable(US - France)1866 (London - Bombay)1870 Invention of Telephone by Bell1876 First manual exchange in India (50 lines, Cal.)1882 Indian Telegraph Act1885 Sir J. C. Bose transmits on wireless1895 Marconi demonstrates wireless (UK - France)1899 Beginning of Bell company1903 Lee Deforest develops vaccumetube ampl.1906 PABX1910

4 Under ground cable in US1915 Baird develops picture tube and picture tx Hartley introduces concept of information as a measure of quantity of data in a message1927 Marconi discovers Microwaves1932 First co-axial cable manufactured1936 First SPC computer (ENIAC)1946 Transistor invented1947 Shannon’s theorem on channel capacity1949 Electronic switching1955 First artificial satellite (USSR Sputnik)1957

5 Kilby at TI invents IC1958 Paul Baran of Rand Corp. proposes packet switching 1960 STD in India(Kanpur - Lucknow)1960 Paging system, Telstar satellite1962 ARPANET using packet switching (TCP/IP) First on ARPANET1971 Cellular telephone in Tokyo1979 IBM - PC + Microsoft - DOS1981 Portable cellular (Motorola)1984 GSM in 13 European countries1988

6 Tim Burner Lee at CERN proposes Hyper-text info. System (Birth of WWW)1990 Digital mobile network in USA1993 Indian Telecom. Policy opens for private sec.1994 Internet service launched in India1995 Telecomm. Reg. Authority of India set-up1997 GMPCS (Iridium) starts 1998 Long distance telephony opened for competition in India1999 Lucent, Motorola, Microsoft opens office in India IT bill passed 2000 Wireless in Local Loop makes its presence in India 2001 Net Telephones legally introduced in INDIA1 April 2002

7 Brief History of Internet 1965Packet switching proposed (D. Davis UK, P. Baran US) 1969ARPANET Launched 1972 Beginning of (Tomlinson USA) 1974First article on TCP/IP (Cerf/Kahn) 1979First research lab. Comp. Network (NSF, Univ. of wis) 1982Internet defined as TCP/IP connected n/w 1989No. of internet users reach 100,000 and IETF formed 1992WWW released, No. of nodes hits 1 Million 1995VOIP comes to market 2000No. of hosts break 300 M, voice traffic crosses over data 2002VOIP takes 13 % of long haul telephone traffic

8 Digital Divide In Africa 1 phone per 100 persons In India4 phones per 100 persons USA2 phones per persons Growth : Billion, Billion 5 Billion people in the world but Only 5 to 6 % of world population has access to internet and90 percent of them are in industrial world Africa and middle east has only 1 % of internet users

9 Technology Development (Services) Principles of wire/wireless comm., for point to point (or multi-point) developed (modulation, line, source and channel coding) First stage of switching technology (FDMA, TDMA, Time and space switch) Second stage of switching technology (packet switching, Network management, optical fibers multiple services (Multi-media - voice, data, fax, video) Selection of the appropriate technology for accessing the core network by end user for multiple services with economy and QOS becomes main issue)

10 Definitions Core Network : Combination of switching centers and transmission systems connecting switching centers. (In India core network, till now, extended up to national boundaries, now the core networks of various TELCOs will be connected by the inter-exchange networks) Access Networks : The portion of public switched network that connects access node (edge of access n/w) to the individual subscriber Access network in India is predominantly twisted copper wire (approx. 750 million of copper lines in the world)

11 Access Nodes (Access Network Interface or ANI) Concentrators of individual lines to T1/E1 Cellular antenna sites PBX Optical Network Units Cable TV

12 Various Access Options Narrow band –PSTN based access –ISDN based access –Cellular based (Cellular digital packet data) –PLCC based Broad band –xDSL –Cable modems –Fixed wireless –FTTx (PON)

13 Traditional Local Loops In 1970’s –Residence to CO by copper line carrying analog voice/data (CO interconnected by T1/E1 or microwaves) –Business Premises PABX connected to CO by number of lines for carrying analog voice/data In 1980’s –Residence to RLU by copper wire carrying analog voice/data or Digital voice (ISDN), RLU to CO by OFC –Business premises PABX to MUX on digital trunk lines like T1/E1 (Mux to CO by T3/E3) –Some business houses also use satellite links

14 Local Loops (cont.) Residence to power line company center on electric wire Fiber to the home or cabinet (FTTH/FTTC) –Residence to ONU on twisted pair/ co-axial/fiber –ONU then connects to optical MUX/DEMUX Business PABX connects to a MUX switch by trunk lines which connects to the SDH/SONET optical ring

15 Digital transmission Hierarchy

16 SDH/SONET Multiplexing Hierarchy MultiplexingData RateUSAEuropean Level (MBPS)NameName OC-1Undefined OC-3STM OC-9STM OC-12STM OC-18STM OC-24STM OC-36STM OC-48STM OC-192STM-64

17 Internet Access to Home (PSTN Modems) The Client work station connects to modem which is connected through the PSTN twisted pair to CO and finally to the modem pool at the server PSTN MODEM STANDARDS –V.21/Bell baud, FSK, 2-wire, async –V baud, QAM with trallis FEC and Echo cancellation –V baud –V.42bisISDN 64/128 Kbps With error correction and compression –V.90, V.9256 Kbps voice band modem –V Kbps leased line baseband modem 2 wire and 4 wire

18 Shannon’s theorem on channel capacity C < B log (1 + S/N). - 2 For B = 4 KHz and S/N = 30 dB C = 40 KBps approx. Assumption AWGN, Modulation Technique and Coding technique not defined Cross talk and ISI are major issues in PSTN lines

19 Issues in PSTN based access to Internet Slow connect time to server (via local switch) (Not suitable for on-line transaction processing) Low band width Cost of connect time on PSTN even when not being used for data transmission Not suitable for many high BW applications like video conferencing, Bulk file transfer etc.

20 Accessing Network using ISDN Digital Network Access –Networks are digital –Services are integrated –Two types of access (One for home and another for business (PABX)) –Considerable economy in terms of access time and ease in operation and maintenance

21 ISDN (cont.) Uses two wires (basic access) or 4 wires (primary access) for getting connected to the central office digital switc ISDN based equipment (TE!) can be directly connected to the network Terminator Non-ISDN based equipment (TE2) can be connected via Terminal Adapter (TA) Network Terminator - 2 (NT2) can connect multiple number of equipments Various ISDN reference interfaces R, S, T, U for interfacing between NT1/2, TA and TE1/2

22 ISDN Services & Access Network Interface (ANI) structure

23 ISDN Merits Simultaneous voice and data transmission 128 Kbps delivery rate Integration of multiple services on single line cost effective than PSTN Most local loops can be used without modification Lower error rate Faster connect time to server

24 Voice Over IP (VOIP) VOIP is the fastest growing area in comm. Today Carries voice traffic as data packets over packet switched data networks instead of as asynchronous stream of binary data over a circuit switched TDM voice network Address and control info of IP packet carries voice to dest. Convenient to talk with multi-media PC VOIP on LAN is convenient since no additional resources are needed (PC should be on all the time) Saves resources as against circuit switched network Economical and with reduced maintenance cost Alternatively : voice enabled cable modem, or DSL boxes

25 Steps Involved in VoIP Analog voice digitized at 8 K samples per second generating 64 Kbps bit stream, non-linear ADC, A-law (India) Digital filtering to remove line echo, remove silence period, time stamping, (add comfort noise at the rx end ) Voice frame formation and data compression 64 Kbps compressed to 8 Kbps, 10 msec frame (10 byte data) IP packet preparation, Real-time Transport Protocol (RTP) with 12 byte header, 8 byte UDP header, 20 byte IP header IP packet transmission on internet (hubs, switches, routers) Steps 1 to 5 are executed in reverse order at the rx. end

26 End-to-end VoIP packet latency (Delay) Delay sourceTypical values in msec. Recording (in PC) Encoding (codec) Compression Internet delivery Jitter buffer De-compression Decode Average delay msec

27 PSTN v/s VoIP PSTN delay is less than 30 msec across globe, VoIP delay is approx. 150 msec QOS (delay) and QOV are variable and not guaranteed PC should be on all the time Annoying echoes due to larger delays (echo suppression can not be used, complex echo cancellation need to be used) Larger overhead per packet Much lower monthly is the main motivating factor

28 Protocol Stacks Applicationftp, mail protocols sw, speech coders P, S, TTCP, UDP,RTP, RTCP, SNMP NetworkIP, ICMP, X.25 Data linkEthernetATM, V.34, 90 LLC, MACFrame relay HDLC, LAPB Physical10baseTISDNSLIC U, S, T int.codec LANISDN, WANPOTS

29 QOS in Internet networks QOS is a measure of how quickly and reliably the data is transferred from source to the destination. (data : Time sensitive financial transactions, still images, larger data files, voice, video) How to quantify and measure QOS Each service may require different types of QOS Subscriber Lease Agreement (SLA) must mention how QOS will be measured, conveyed to the customer, and what are the compensation clauses if it is not met.

30 5 Important performance of QOS Availability100 % theoretically, 99.8 (90 minutes down time per month) (2.6 secs/month) Throughput (is not maximum capacity of the network) –Sharing network lowers throughput –Overhead of extra-bits per packet reduces the effective transfer rate –The service provider must guarantee minimum rate of throughput for an application

31 QOS (cont.) Packet lossBuffered queues get overflow or errors Retransmission adds delay –Normal value of less than 1 % average delay per month Latency (Delay) –PSTN less than 30 msec, –Internet 150 msec (digitizatin, compression, queuing ) Jitter –Variation in queue length – Variation in processing time – Time to re-order segmented packets

32 Sensitivity of data types to QOS on internet Traffic TypeBandwidthLossdelayJitter VoiceVery lowMed.HighHigh E-commerceLowHighHighLow (Transactions) LowHighLowLow TelnetLowHighMed.Low Serious BrowsingMediumHighHigh LowFTPHighMed. LowLowVideo conf.High Med.HighHigh

33 Provisions for QOS IPBest effort, no guarantee on delivery or delay TCPChecks for sequence number of rx. Packet and requests for retransmission (slow) UDPRuns faster than TCP ATMExtensive provisions for QOS tags Soln :IPV-6, IP over ATM, Edge routers

34 Broadband Access Technologies xDSL Technologies (Digital subscriber line) CATV Technology Fiber To The Home/Cabinet (FTTx) Technology Wireless access Satellite Technology Power line Technology

35 Various DSL Technologies IDSLISDN based DSL (128 kbps modem banks) HDSLHigh Data rate DSL (T1/E1 speed) earlier DSL ADSLAsymmetric DSL (1.5 to 9 Mbps downstream) (16 to 800 Kbps upstream depending on dis.) UDSL, SDSLUnidirectional, Symmetric VDSL12.9 Mbps (4500 ft) (1000 ft) Uses twisted copper wire, future local loops

36 DSL Application High speed internet access, real-time access on remote LAN Distance learning (school, colleges, libraries), always on Video conferencing Combined voice and high speed data on same line Video on demand in apartment blocks using VDSL

37 Advantages of ADSL (over cable or satellite) Low infra structure investments (shares telephone line) Can adapt to varying line conditions As secure as dial-up modem or T1 connection Asymmetric matches with future internet applications High dedicated BW (unlike sharing in cable TV) ADSL switches bypass the telephone switches that are getting overloaded with data traffic 40 times faster than ISDN and 100 times than 28 K modem

38 Key features of ADSL 4 KHz is reserved for POTS The high bit rate data is line encoded using efficient and robust line coding techniques like DMT or CAP Multiplexed at CO by DSLAM (Digital Subscriber Line Access Multiplexor) Uses DSP techniques for echo-cancellation of Near-End (NEXT) and Far-End (FEXT) cross talk of multi-pair Line is properly terminated to reduce loading of loop better UTP category cable used

39 ADSL Modulation CAP - Carrierless Amplitude/phase modulation –a version of QAM in which incoming data modulates a single carrier which is them transmitted, the carrier itself is suppressed DMT - Discrete Multi-tone –a version of multi-carrier modulation in which incoming data is collected and then distributed over a large number of small individual carriers each of which uses QAM

40 Wireless Access Techniques 2G 1991GSM (Digital circuit switched) 16 Kbps 2.5G 2001 HSCSD/EDGE192 Kbps (High Speed Circuit Switched Data) 3G 2004EDGE_2, 3G_IP (ckt + packet) upto 2 Mbps Broadband wireless access –13 frequencies allocated by ITU (700 MHz to 40 GHz)

41 Broadband access in wireless Challenges –Spectral allocation and BW limitations –Noise environment and interference Techniques used – Line coding and error correction coding –Signal processing –Antenna design –TDMA/FDMA/SDMA/CDMA

42 FTTx Technology Advantages –Bandwidth for large number of users at a site –Growth potential (cost of fiber reducing) –QOS –can directly connect to SDH/SONEt –Topologies : bus, ring or star (Unidirectional) –Access : TDMA, WDMA

43 Cable Modems Set-top box interfaces TV at customer premises with cable modem connected by co-axial cable to cable operator Uses collision resolution protocol (request for mini-slots) Uses 64 or 256 QAM 6 MHz channel ( Mbps (shared), MHz 17 Million cable connections, security is an issue

44 Satellite Constallation OrbitLEOMEOGEO Altitude140010,35236,000 KM Round msec trip delay Data ratenx2 Mbps-128 Kbps

45 Conclusions The ability to access broadbase contents from internet regardless of physical location is beneficial in increasing productivity through telecommuting At global level, data comm. Is moving to a single, public networking environment environment with multi-gigabit tx. Rates, optical fiber based SDH (SONET) at physical layer with ease in mux/demux of low data rate traffic in high speed links (Core networks and transmission between exchanges are capable of carrying high bit rate user data)

46 Types of services significantly increased at user premises Access at high speed from customer premises and QOS is the main issue Many options : Dial-up, ISDN, cable, ADSL More options in future : FTTX, satellite, mobile, PLCC Availability, reliability and economy as deciding factor No unique solution Knowledge of access technologies, their QOS and cost and market trends are important in making long term investmens

47 Bibliography `The cost of quality in internet-style networks’ Amitya Dutta-Roy, IEEE spectrum, Sept `Internet Telephony : going like crazy’ Thomsen & Jani, IEEE spectrum, May 2000 Dr. Dobb’a journal, May 2000 `An engineering approach to computer networking’ S. Kesav, 1999, Addison wesley `Telecommunication Transmission systems’ R. G. Winch, 1993, McGraw Hill `Digital Communications’ Glover and Grant, 1998, prentice Hall

48 Telecommunications Network management Aidarous and Plevyak, IEEE press, 2001 Security for Telecomm. Network Manag. Rozenblit, IEEE press, 2001 Fundamentals of Digital Switching McDonald, Plenum press IP technology: History, current state and prospects Yanovsky, St. Petersburg univ, Russian fed. IT and Telecomm. Impact on developing countries W. Luther, FCC, USA Chaotic electronics in telecomm. Kennedy CRC press Digital comm. Systems with sat. and fiber optics appln Kolimbiris, Addison wesley, 2001

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