TELECOMMUNICATION SYSTEMS

Transcription

1 TELECOMMUNICATION SYSTEMS IP Networking Through Telecommunication System System Engineering BSc Full-time

2 Overview Phone Line Modems Accoustic modem PSTN modem ISDN modem ADSL XDSL

3 Acoustic modems Connection management by hand (dialing, putting down the phone handset) 300 or 1200 b/s (ITU-T V.21, V.22) Curiosity: were able to work with the part of todays phone modems 1970s - early of 1980s No direct connection to the network Was enabled to connect only the post office devices Nowadays that is a forgotten history

4 Acoustic modems

5 PSTN Public Switched Telephone Network

6 Circuit - Switching 1. Real Time Voice Transmission 2. Point To Point Networks 3. Bandwidth is constant 4. Data Transmission PSTN & ISDN & TDM Circuit Switching Network Circuit - Switching telephone network Carries analog voice Constant Bandwith

7 Data Transfer Over PSTN Digital lines between santrals E1 Tranks: 32 channels X 64Kbps Users Analog 3 X E1 Trank Analog Users Digital Santral 1 Santral 2 32X3=96 calls Modem converts: Digital data to Analog voice 28 Kbps 56 Kbps

8 How to connect net over PSTN? Santr al Analog Analog Digital

9 PSTN Connection

10 PSTN Connection

11 ISDN Integrated Service Digital Network

12 Overview Define ISDN, its standards and the type of services offered Describe the two main types of services, namely BRI and PRI Give examples of ISDN links Simple SOHO line, ISDN remote bridges etc Briefly outline a few other features of ISDN

13 ISDN Defined Known as the Integrated Services Digital Network Data, audio, image and video transmission It is a switched digital telecommunication line that can be delivered over regular copper wires Possible to provide end-to-end digital communications

14 ISDN Application Examples. On/off ramp to the information super-highway to communicate at speeds of 128 Kbps for a single ISDN line Multiple ISDN lines can be combined together to achieve higher communication speeds Home use On/Off ramp to the Internet Business world Provide remote access to LANs

15 ISDN Standard and Connection There is a national ISDN standard known as the NI standard It is being implemented in phases Current implementation is termed as NI-1 to indicate that it is in phase 1 of the implementation process Can be obtained from a local telephone company in the same way an analog connection is obtained Phone companies offer different types of ISDN connections

16 ISDN Basic Characteristics B Channels 64 Kbps D Channel Kbps Data Data Data Signaling

17 Inverse Multiplexing of B Channels B (64 Kbps) 128 Kbps 128 Kbps B (64 Kbps) Inverse Multiplexers

18 ISDN Service Connections There are two different types of ISDN services that are widely available One is known as the Basic Rate Interface or BRI Used for home or SOHO connection The other is known as the Primary Rate Interface or the Used in large businesses

19 In Summary ISDN is a switched digital network Can be used for establishing a point-to-point digital connection BRI and PRI Number of B Channels vary in each case B channels can be combined together to achieve a higher communication speed

20 BRI Characteristics Basic Rate Interface 2 B Channels 1 D Channel B channels are known as bearer channels Carry information D channel is known as the Delta channel Used for signaling purposes 2B + D channel service

21 A Simple BRI Connection to a Microcomputer Network Terminator NT 1 ISDN BRI Line 2B +D ISDN Terminal Adapter Phone Computer

22 The Channels Channel B 64k bps per channel The two B channels can be inverse multiplexed or boded together Achieve a maximum aggregate communication speed of 128 Kbps Channel D 16 Kbps Entire bandwidth is not used for signaling purpose Excess of 9.6 Kbps is available for packet switched data transmission applications Excess bandwidth usage - climate control, security alarm system etc.

23 In Summary BRI is the basic ISDN service Composed of 2 B channels and a D channel B Channels are circuit switched D Channel is packet switched Excess capacity can be utilized for packet switched applications

24 PRI Service Primary Rate Interface More sophisticated service compared to BRI PRI service offers 23 B channels and 1 D channel B channel properties Each B channel operates at a speed of 64K bps The B channels are used for carrying data B channels can be combined together to increase the aggregate communication speed D channel properties Each D channel operates at a speed of 64 Kbps Considerably faster than the D channel in BRI 23 B channels share a D channel for signaling purpose

25 PRI Channel Delivery PRI channels are delivered over a T1 line T1 speed 1.544M bps Aggregate speed of PRI from all 23 B channels and the single D Channel is computed as follows: 23 * xx = Mbps

26 Sample Services (PacBell) Centrex ISDN For businesses that already have the Pac Bell s centrex phone system SDS-ISDN BRI service offered for small businesses Charges Per channel Per minute

27 Sample Services (ISDN) Home ISDN Offers a BRI connection 2B + D Charges are cheaper especially during off-peak hour Per channel Per minute SDS-56 Single channel switched 56 Kbps digital service

28 Sample Cost Comparison Service Month Inst. Usage Cen-ISDN Bus. Measured SDS-ISDN Bus. Measured Home Bus. Measured ISDN Flat Otherwise PRI Bus. Measured SDS Bus Measured * Rebates may apply to Installation

29 Use of ISDN Adapters NT1 Pub. Switched Network NT1 ISDN Adapter Analog Modem ISDN Adapter Computer Computer Computer

30 Remote ISDN Access to a LAN NT1 BRI PSN BRI NT1 Remote ISDN Bridge ISDN Adapter Computer 28.8K bps to 56K bps ISDN Router Ethernet 128K bps

31 Remote Access Over PRI BRI PSN PRI NT1 DSU/CSU ISDN Adapter ISDN Router Computer Ethernet

32 Important Features of the PRI Connection Communication links can be established between: remote computers and this LAN this LAN and remote locations this LAN and other remote LANs Link is established using a powerful router A separate DSU/CSU unit is used as opposed to the NT1 network terminator used in the case of BRI

33 Commercial Examples of ISDN Equipment ISDN adapter 3Com Impact IQ ISDN routers Ascend and Cisco are sample manufacturers Ascend Pipeline 50 and Ascend Pipeline 100 are examples of such routers For the latest information on ISDN equipment access the manufacturers web sites

34 ISDN Use in Video Conferencing Dynamic bandwidth allocation Circuit switched Symmetric bandwidth

35 ADSL Asymmetric Digital Subscriber Line

36 Introduction ADSL is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines ADSL is capable of providing up to 50 Mbps, and supports voice, video and data. ADSL is the #1 Broadband Choice in the World with over 60% market share ADSL is now available in every region of the world

37 What does ADSL mean Asymmetric - The data can flow faster in one direction than the other. Data transmission has faster downstream to the subscriber than upstream Digital - No type of communication is transferred in an analog method. All data is purely digital, and only at the end, modulated to be carried over the line. Subscriber Line - The data is carried over a single twisted pair copper loop to the subscriber premises

38 ADSL standards : Standard name Common name Downstream rate Upstream rate ITU G ADSL (G.DMT) 8 Mbit/s 1.0 Mbit/s ITU G ADSL Lite (G.Lite) 1.5 Mbit/s 0.5 Mbit/s ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s ITU G.992.3/4 Annex J ADSL2 12 Mbit/s 3.5 Mbit/s ITU G.992.3/4 Annex L RE-ADSL2 5 Mbit/s 0.8 Mbit/s ITU G ADSL2+ 24 Mbit/s 1.0 Mbit/s ITU G Annex L RE-ADSL2+ 24 Mbit/s 1.0 Mbit/s ITU G Annex M ADSL2+ 28 Mbit/s 3.5 Mbit/s

39 ADSL Speed Comparison Pure Fibre Hybrid Fibre/Copper FTTH Enhanced Copper ADSL FTTx, VDSL2, ADSL2plus Voice band Modem ISDN

40 ADSL Range In general, the maximum range for DSL without a repeater is 5.5 km As distance decreases toward the telephone company office, the data rate increases Data Rate Wire gauge Wire size Distance 1.5 or 2 Mbps 24 AWG 0.5 mm 5.5 km 1.5 or 2 Mbps 26 AWG 0.4 mm 4.6 km 6.1 Mbps 24 AWG 0.5 mm 3.7 km 1.5 or 2 Mbps 26 AWG 0.4 mm 2.7 For larger distances, you may be able to have DSL if your phone company has extended the local loop with optical fiber cable

41 ADSL Speed Factors The distance from the local exchange The type and thickness of wires used The number and type of joins in the wire The proximity of the wire to other wires carrying ADSL, ISDN and other non-voice signals The proximity of the wires to radio transmitters.

42 ADSL network components The ADSL modem at the customer premises(atu-r) The modem of the central office (ATU-C) DSL access multiplexer (DSLAM) Broadband Access Server (BAS) Splitter - an electronic low pass filter that separates the analogue voice or ISDN signal from ADSL data frequencies DSLAM.

43 ADSL Loop Architecture DSL Voice Switch ISP Central Office Subscriber premises

44 ADSL Requirements Phone-line, activated by your phone company for ADSL Filter to separate the phone signal from the Internet signal ADSL modem Subscription with an ISP supporting ADSL

45 How does ADSL work ADSL exploits the unused analogue bandwidth available in the wires PSTN Upstream Downstream 4 25, KHz ADSL works by using a frequency splitter device to split a traditional voice telephone line into two frequencies

46 ADSL Modulation Modulation is the overlaying of information (or the signal) onto an electronic or optical carrier waveform There are two competing and incompatible standards for modulating the ADSL signal: Carrierless Amplitude Phase (CAP) Discrete Multi-Tone (DMT)

47 Carrierless Amplitude Phase Carrierless Amplitude Phase (CAP) is an encoding method that divides the signals into two distinct bands: 1. The upstream data channel (to the service provider), which is carried in the band between 25 and 160kHz 1. The downstream data channel (to the user), which is carried in the band from 200kHz to 1.1MHz. These channels are widely separated in order to minimize the possibility of interference between the channels.

48 Discrete Multi-tone (DMT) Discrete Multi-Tone (DMT) separates the DSL signal so that the usable frequency range is separated into 256 channels of kHz each. DMT has 224 downstream frequency bins (or carriers) and 32 upstream frequency bins. DMT constantly shifts signals between different channels to ensure that the best channels are used for transmission and reception.

49 The DMT frequency bands Frequency Division Multiplexing (FDM) Echo Cancellation

50 Asynchronous Transfer Mode ATM is a connection-orientated technique ATM provides cell sequence integrity Cells are much smaller than standard packet-switched networks (53 bytes) The quality of transmission links has lead to the omission of overheads There is no space between cells

51 Types of ATM services Constant Bit Rate (CBR) Variable Bit Rate (VBR) Unspecified Bit Rate (UBR) Available Bit Rate (ABR)

52 ATM Layer The ATM layer transport information across the network ATM uses virtual connections for the information transport The connections are divided into two levels: The Virtual Channels The Virtual Path This mechanism is used to provide quality of service (QoS)

53 ATM Connections The connection between two endpoints is called a Virtual Channel (VC). A Virtual Path (VP) is a term for a bundle of virtual channel links that all have the same endpoints. Each VC and VP has a unique identifier Virtual paths are used to simplify the ATM addressing structure.

54 ATM Adaptation Layer (AAL) The ATM Adaptation Layer (AAL) converts information from the upper layers into ATM cells The standard used for ATM over ADSL services is AAL5 AAL5 Encapsulation Methods Virtual Channel Multiplexing (VCMux) LLC/SNAP For detailed information please refer to the RFC 1483

55 ADSL Protocol stacks Ethernet over ATM (EoA) IP over ATM (IPoA) PPP over ATM (PPPoA) PPP over Ethernet (PPPoE) Native ATM

56 Point-to-Point Protocol over Ethernet over ATM (PPPoEoA)

57 Conclusion ADSL advantages Simultaneous Internet and voice/fax capabilities over a single telephone line Uninterrupted, high-speed Internet access that's always on-line Cost-effective solution for society Data Security that exceeds other technologies Fast download speeds ADSL disadvantages: Distance-sensitive Slower upload speeds Phone line required

58 ADSL Equipments Modem Splitter Microfilter

59 ADSL DSLAM DSLAM (Digital Subscriber Line Access Multiplexer)

60 XDSL Asymmetric Digital Subscriber Line

61 xdsl Optical network expanding (getting closer to subscriber) Optical Network Unit ONU at curb or basement cabinet FTTC (curb), FTTB (building) These scenarios usually dictates low power Rates can be very high since required reach is minimal! Proposed standard has multiple rates and reaches

62 FTCC

63 xdsl Technology Type Meaning Coding/Tech. Reach/Speed/Range Application DSL Digital Subscriber Line 2B1Q line Duplex: 160 kbit/s (2B(64k)+D(16k)+mana gementt) Range: 5,5km ISDN- voice & data HDSL High-bit-rate DSL CAP researched by AT&T Duplex: 2Mbit/s, 2 or 4 wire, Range : 3-8km E1 (2 Mbit/s) networking SDSL Symmetric DSL (Single Line) Modulating Duplex: 2Mbit/s Range : 3 km Synchron user networking

64 xdsl Technology Type Meaning Coding/Tech. Reach/Speed/Range Application ADSL Asymmetrical DSL DMT coding (Discrite or Multiple modulation 4kHz channels) Asymmetric Downlink: 1,5 8 Mbit/s Uplink: kbit/s Range : 1. Mbit/s 4800m 6 Mbit/s 3600m 8 Mbit/s 2700m Fast Internet, far LAN networking, VoD, multimedia VDSL Very high bit rate DSL =ADSL / stricter requirements, smaller range Asymmetric Downlink: Mbit/s Uplink: 1,6-2,3 Mbit/s Range : 13 Mbit/s 1350m 26 Mbit/s. 900m 52 Mbit/s..300m The same like ADSL+HDTV

65 VDSL2 DMT line code (same khz spacing as ADSL) VDSL uses BW of 1.1 MHz - 12 MHz (spectrally compatible with ADSL) VDSL2 can use 20 khz - 30 MHz new band-plans (up to 12 MHz, and MHz) increased DS transmit power various algorithmic improvements borrowed improvements from ADSL2 3 user data types - STM, ATM and PTM

66 VDSL2 band plans North American bandplan US0 (if present) starts between 4 khz - 25 khz and ends between khz Europe - six band plans (2 A and 4 B) A (998) US0 from 25 DS1 from 138 or 276 US DS B (997) US0 from 25 or 120 or nonexistent DS1 from 138 or 276 US DS