UNIT-IV Digital Subscriber Access ISDN The telephone network
UNIT-IV Digital Subscriber Access ISDN The telephone network has evolved into a digital one with digital exchanges and links The signalling system has become a digital message-oriented common channel signalling system (SS#7) The term Integrated Digital Network is used to describe these developments 2 ISDN The Public Switched Telephone network is still
analogue from the subscriber to the local exchange The need has arisen to extend the digital network out to subscribers and to provide a single standardised interface to all different users of public networks ISDN fulfils that need 3 Integrated Services Digital Network Packet switched network Telephone Circuit
switched network Data terminal PBX Alarm LAN Customer ISDN Interface ISDN central office
Databases Digital pipe Other Networks & services 4 ISDN In Practice there are multiple networks providing the service nationally The user however, sees a single network
5 Benefits to Subscribers Single access line for all services Ability to tailor service purchased to suit needs Competition among equipment vendors due to standards Availability of competitive service providers 6 Architecture Integrated Digital Network Common physical
interface ISDN central office Digital circuitswitched backbone Packet-switched network ISDN subscriber loop Basic 2B+D Primary 30B+D Network-based processing services
7 ISDN Standards Contained in the I-series recommendations Issued by CCITT (now ITU-T) Six main groupings I.100 to I.600 series I.100 series - General Concepts
I.200 series - Service Capabilities I.300 series - Network Aspects I.400 series - User-Network Interfaces I.500 series - Internetwork Interfaces I.600 series - Maintenance Principles 8 ISDN Channels The Digital pipe is made up of channels - one of three types B channel, D channel or H channel Channels are grouped and offered as a package to users 9 B Channel
B channel-64 kbps B is basic user channel can carry digital data or PCM-encoded voice or mixture of lower rate traffic. 10 B Channel Four kinds of connection possible Circuit-switched Packet-switched - X.25
Frame mode - frame relay (LAPF) Semipermanent - equivalent to a leased line 11 D Channel D Channel - 16 or 64 kbps Carries signalling information to control circuit-switched calls on B channels Can also be used for packet switching or lowspeed telemetry 12 H Channel Carry user information at higher bit rates 384kbps or 1536kbps or 1920kbps Can be used as a high-speed trunk
Can also be subdivided as per users own TDM scheme Uses include high speed data, fast facsimile, video, high-quality audio 13 ISDN Channels and their Applications B Channel (64 kbps) Digital voice High-speed data (e.g. packet and circuit switched data) Other (e.g. fax, slow video)
D Channel (16/64 kbps) Signalling (using SS#7) Low- speed data, (e.g. packet, terminal, videotex) Other (e.g. telemetry) H Channel (384/1536 kbps) High-speed trunk Very high speed data
Other (e.g. fast fax. Video) 14 ISDN Basic Access Intended for small business and residential use A single physical interface is provided Data rate is 144kbps plus 48kbps overhead bits totalling 192 kbps Most existing subscriber loops can support basic access 15 ISDN Primary Access
Intended for users with greater capacity requirements Example would be a digital PBX Two standards exist 1.544 Mbps American 2.048 Mbps European 16 ISDN Primary Access Typically it is structured as 30 B channels plus one 64kbps D channel (Europe) Can also be structured as H channels 5H0 +D for a 2.048 Mbps interface or 1H12 +D 17
ISDN Frame Structure Basic Rate Access 48 bits in 250 usec TE to NT FL B1 L DL F L a B2
L DL B1 L DL B2 L DL FL B1 F E DA N a
B2 E DM B1 E DS B2 E DL 8 bits F= Framing bit L = dc balancing bit
E = D-echo channel bit A = Activation bit NT to TE Fa = Auxiliary Framing bit N = opposite of Fa M = multiframing bit B1 = B channel bits B2 = B channel bits D = D channel bits S = Spare bits 18 ISDN Contention Resolution Several TEs can share a single line
How is contention resolved? B-channel Traffic No contention as each channel dedicated to particular TE D - Channel used for data and control so requires a contention resolution mechanism 19 D Channel Contention Incoming Traffic LAPD protocol resolves contention Outgoing Traffic Multiple devices share D channel Contention resolution algorithm required
20 D Channel Contention Idle TEs sends binary 1s on D channel This means no signal (pseudoternery) NT echos received binary value back as echo bit When NT wishes to send on D channel, it listens to echo bits If it hears a string of 1s equal in length to a threshold value Xi, it may transmit Otherwise it must wait
21 ISDN Primary Interface Multiple channels multiplexed on single medium Only point to point configuration is allowed Typically supports a digital PBX and provides a synchronous TDM facility 22 ISDN Primary Access Frame Formats 125 micro-seconds 193 bits timeslot 1 Timeslot 24
Recommendations to support video services as well as normal ISDN services Provides user with additional data rates 155.52 Mbps full-duplex 155.52 Mbps / 622.08 Mbps 622.08 Mbps full-duplex Exploits optical fibre transmission technology Very high performance switches 25 B-ISDN Architecture TE BISDN
Narrowband Capabilities LFC Broadband Capabilities User to Network Signalling TE = Terminal equipment LFC = Local function capabilities LFC
TE Inter-exchange Signalling Capabilities 26 B-ISDN ATM is specified for Information transfer across the user-network interface Fixed size 53 octet packet with a 5 octet header Implies that internal switching will be packetbased 27
BISDN Protocol Structure Plane management function Control Plane User Plane Higher Layers: protocols and functions Higher Layers: protocols and functions Adaptation Layer ATM Layer Physical medium dependent Layer
28 Digital Subscriber Line BLOCK DIAGRAM Asymmetrical DSL (ADSL) ADSL divides up the available frequencies in a line on the assumption that most Internet users look at, or download, much more information than they send, or upload. Under this assumption, if the connection speed from the Internet to the user is three to four times faster than the connection from the user back to the Internet, then the user will see the
most benefit (most of the time). Asymmetrical DSL (ADSL) ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line. Speed: Most existing local loops can handle bandwidths up to 1.1 MHz. ADSL Modem Two standards for ADSL 1. Discrete multitone (DMT) 2. Carrierless amplitude/phase (CAP) CAP - three distinct bands:
1. Voice channel - 0 to 4 KHz 2. Upstream channel - 25 and 160 KHz 3. Downstream channel - 1.5 MHz Carrierless amplitude/phase (CAP) Advantage: Minimizes the possibility of interference between the channels on one line, or between the signals on different lines Discrete multitone (DMT) Constantly shifts signals between different channels, searching for the best channels for transmission and reception
Discrete multitone (DMT) Asymmetrical DSL (ADSL) ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses. Distance Limitations ADSL is a distance-sensitive technology The limit for ADSL service is 18,000 feet (5,460 meters) At the extremes of the distance limits, ADSL customers may see speeds far below the promised maximums customers nearer the central office have faster connections and may see extremely high speeds
OTHER TYPES OF DSL: Symmetric DSL (SDSL) High-bit-rate DSL (HDSL) Very high bit-rate DSL (VDSL) Symmetric DSL (SDSL) Used mainly by small businesses & residential areas Bit rate of downstream is higher than upstream High-bit-rate DSL (HDSL) Used as alternative of T-1 line Uses 2B1Q encoding Less susceptible to attenuation at higher frequencies Unlike T-1 line (AMI/1.544Mbps/1km), it can
reach 2Mbps @ 3.6Km Very high bit-rate DSL (VDSL) Uses DMT modulation technique Effective only for short distances(300-1800m) Speed: downstream : 50 - 55 Mbps upstream : 1.5-2.5 Mbps PSTN Review Digital Loop Carrier Pushes the digital PSTN closer to customer AT&T SLC-40, SLC-96, Nortel DMS P-phone,
TR-08 Mode 1 pair-gain: Replace 96 pairs with 5 T1s Access Network CLASS 5 pair-gain (one spare for span protection) UTP/coax/fiber Street FTTB/FTTC cabinet CPE
telephony Slide 44 Fiber in the Loop What is FTTP? Fiber To The x (FTTx, with x being the C for the Curb, or P for to the premises) is an important, emerging technology that will provide customers with new featurerich services and improved quality of current services. Why FTTP? Consumers will require additional bandwidth to the home in the near future
Competition is beginning to offer a triple-play (i.e., voice, video, and data) bundle FTTP provides SPs with the ability to provide cutting edge technology and best-in-class services Deploying a fiber optic cable to each premises will provide an extraordinary amount of bandwidth for future services An FTTP based network will result in less operational expenses Why FTTP? (Contd) 100M 12 - 50M Access Bandwidth Growth
FTTPhas hasthe the FTTP necessary necessary bandwidthto to bandwidth supportnear nearterm term support andlong longterm term
ADSL Cable Modem ADSL2(+) VDSL FTTP 2004 Today's applications are continuing to drive demand for increased bandwidth Historically, unforeseen applications have quickly consumed available bandwidth and driven the development of higher speed platforms Why Now? (Contd)
SPs are losing access lines Bundling with the triple-play should reduce the churn Competition with cable providers is forcing action Cable Modems currently have over 60% of the HSD market share and the gap is expected to increase Cable companies are beginning to offer voice over cable A number of IP telephony trials are currently underway:
Time Warner in Portland, ME Comcast in Coatesville, PA Cablevision in LI / NJ Experience suggests that cable will be very successful, absent an effective competitive response. Matching Application and Network Requirements Data Application Typical bandwidth (downstream) High Speed Internet Access (browsing, IM, Chat, FTP, VPN, access, etc) E-Mail
Up to 3 Mb/s Live TV on PC 300 to 750 kb/s Internet Video on Demand 300 to 750 kb/s Video Conferencing 300 to 750 kb/s Voice telephony 5 to 128 kb/s
Interactive Games 10 to 750 kb/s Broadcast TV (e.g., MPEG2) 2 to 6 Mb/s High definition TV HDTV 12 to 19 Mb/s Pay Per View and NVOD (e.g., MPEG2) 2 to 6 Mb/s
As above Deployment of FTTH Plan is to reach 1 Million Homes by end of 2004 in the 20Mb to 30Mb rate Double that rate as we move into 2005 Reach 100Mb by 2007 Picture Messaging
Voice Data Video Conferencing Common Protocol Common Infrastructure Video Service Voice over IP Gaming Virtual Private Network FTTP Basics Full Service Access Network (FSAN) Primary source of PON standards. Created by service providers in order to facilitate suitable standards. FSAN Standards ITU-T G.983
Passive Optical Network (PON) a point-to-multipoint local access Network. Optical Line Terminal (OLT) active component typically located in the central office. Passive Optical Splitter distributes optical signal from a single fiber to multiple fibers, merges signals from all fibers, & connects them to the OLT receiver. Optical Network Terminal (ONT) housed in a network interface device enclosure. FTTP Lingo PON Passive Optical Network OLT Optical Line Terminal ONT Optical Network Terminal FTTP Fiber to the Premises APON ATM PON BPON Broadband PON GPON Gigabit PON
FSAN PON Solution How Does an APON/BPON Work? CO, Feeder: OLT (Optical Line Termination) Outside Plant: Optical Distribution Network Customer Premise: ONT (Optical Network Termination) Downstream: 622 Mbps @ 1490nm ATM switch, PSTN, Internet Passive Passive Optical
Optical Splitter Splitter Services to user: POTS, Internet Access Upstream: 155 Mbps @ 1310nm Downstream: Time Division Multiplex T AN GR A B C + GRANT AB AB
C+ ONT A A B C + GRANT ONT B C + GR AN T ONT C
Upstream: Time Division Multiple Access ONT A A ONT B ONT C Current Standards FCC 76.605 - Multichannel Video and Cable Television Service Requirements, Technical Standards. Code of Federal Regulations, Title 47, Volume 4, Part 76, Subpart K, Section 76.605 (47CFR76.605).
ITU-T Recommendation G.983.1 - Broadband optical access systems based on Passive Optical Networks (PON). Overview Satellite technology has progressed tremendously over the last 50 years since Arthur C. Clarke first proposed its idea in 1945 in his article in Wireless World. Today, satellite systems can provide a variety of services
including broadband communications, audio/video distribution networks, maritime navigation, worldwide customer service and support as well as military command and control. Satellite systems are also expected to play an important role in the emerging 4G global infrastructure providing the wide area coverage necessary for the realization of the Optimally Connected Anywhere, Anytime vision that drives the growth of modern telecom industry. Course Objectives This course aims to: Provide a broad overview of the status of digital satellite communications. Discuss main physical, architectural and networking issues of satellite systems. Provide in-depth understanding of modern modulation,
coding and multiple access schemes. Review the state of the art in open research areas such as speech and video coding, satellite networking, internet over satellite and satellite personal communications. Highlight trends and future directions of satellite communication Section 1: The SATCOM Industry System Design Issues An Overview of Satellite Communications Examples of current military and commercial systems. Satellite orbits and transponder characteristics (LEO, MEO, GEO) Traffic Connectivity: Mesh, Hub-Spoke, Point-to-Point, Broadcast
Basic satellite transmission theory Impairments of the Satellite Channel: Weather and Doppler effects, Channel models. Communications Link Calculations: Definition of EIRP, Noise temperature and G/T ratio, Eb/No. Transponder gain and SFD. Link Budget Calculations. Down-link requirements. Design of satellite links to achieve a specified performance. Earth Station Antenna types: Pointing/Tracking. Small antennas at Ku band. FCC-Intelsat-ITU antenna requirements and EIRP density limitations. Brief introduction to implementation issues: LNA, Up/down converters, oscillator phase noise. Section 2: Elements of Transponder Design The
Baseband Physical Layer of the Transponder The Baseband System Introduction to the theory of Digital Communications: Modulation, Equalization and FEC Digital Modulation Techniques: BPSK, QPSK, Nyquist signal shaping. Overview of Bandwidth Efficient Modulation (BEM) Techniques: M-ary PSK, Trellis Coded 8PSK, QAM. PSK Receiver Implementation issues: Carrier recovery, phase slips, differential coding.
Overview of Forward Error Correction (FEC): Standard FEC types (Block and Convolution Coding schemes, Viterbi Decoding), Coding Gain, Concatenated coding, Turbo coding. Section 3: Multiple Access Issues Spread Spectrum Techniques: Military and commercial use of spread-spectrum. DirectSequence PN, Frequency-Hop and CDMA systems. Principles of Multiple Access Communications Multiplexing & Multiple Access FDD/TDD, FDMA, TDMA Concepts of Random Access: ALOHA, CSMA
Multiple Access Techniques: FDMA, TDMA, CDMA. DAMA and Bandwidth-on-Demand (BoD). TDMA Networks: Time Slots, Preambles, Suitability for DAMA and BoD. Section 4: SATCOM Networks and Services Satellite Communication Systems & Networks Characteristics of IP and TCP/UDP over satellite: Unicast and Multicast. Need for Performance
Enhancing Proxy (PEP) techniques. VSAT Networks and their system characteristics. DVB standards and MF-TDMA The Future of SATCOM SATCOMs role in the emerging 4G Information and Communications (ICT) infrastructure. Intelsat INTELSAT is the original "Inter-governmental Satellite organization". It once owned and operated most of the World's
satellites used for international communications, and still maintains a substantial fleet of satellites. INTELSAT is moving towards "privatization", with increasing competition from commercial operators (e.g. Panamsat, Loral Skynet, etc.). INTELSAT Timeline: Interim organization formed in 1964 by 11 countries Permanent structure formed in 1973 Commercial "spin-off", New Skies Satellites in 1998
Full "privatization" by April 2001 INTELSAT has 143 members and signatories listed here. Intelsat Structure Eutelsat
Permanent General Secretariat opened September 1978 Intergovernmental Conference adopted definitive statutes with 26 members on 14 May 1982 Definitive organization entered into force on 1 September 1985 General Secretariat -> Executive Organ Executive Council -> EUTELSAT Board of Signatories Secretary General -> Director General
Current DG is Giuliano Berretta Currently almost 50 members Moving towards "privatization" Limited company owning and controlling of all assets and activities Also a "residual" intergovernmental organization which will ensure that basic
principles of pan-European coverage, universal service, non-discrimination and fair competition are observed by the company Eutelsat Structure Communication Satellite A Communication Satellite can be looked upon as a large microwave repeater It contains several transponders which listens to some portion of spectrum, amplifies the incoming signal and broadcasts it in another frequency to avoid interference with incoming signals. Motivation to use Satellites
Satellite Missions Source: Union of Concerned Scientists [www.ucsusa.org] Satellite Uplink and Downlink Downlink The link from a satellite down to one or more ground stations or receivers Uplink The link from a ground station up to a satellite.
Some companies sell uplink and downlink services to television stations, corporations, and to other telecommunication carriers. A company can specialize in providing uplinks, downlinks, or both. Satellite Uplink and Downlink
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