Spring 2006Data Communications, Kwangwoon University9-1 Chapter 9. High-Speed Digital Access 1.DSL Technology 2.Cable Modem 3.SONET

Spring 2006Data Communications, Kwangwoon University9-2 ADSL Asymmetrical Digital Subscriber Line ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses The existing local loop can handle bandwidths up to 1.1 MHz ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line.

Spring 2006Data Communications, Kwangwoon University9-3 DMT (Discrete Multitone Technique)

Spring 2006Data Communications, Kwangwoon University9-4 DMT: Bandwidth Division There is no set way that the bandwidth is divided Upstream –24 channels * 4 Kbaud/sec * 15 bits/baud = 1.44 Mbps Downstream –224 channels * 4 Kbaud/sec * 15 bits/baud = 13.4 Mbps

Spring 2006Data Communications, Kwangwoon University9-5 DSL: Actual Bit Rate Because of the high signal/noise ratio Upstream –64 Kbps to 1 Mbps Downstream –500 Kbps to 8 Mbps

Spring 2006Data Communications, Kwangwoon University9-6 Customer Site: ADSL Modem

Spring 2006Data Communications, Kwangwoon University9-7 Telco Site: DSLAM

Spring 2006Data Communications, Kwangwoon University9-8 Other DSL Technologies: xDSL SDSL (Symmectric DSL) –For businesses that send and receive data in large volues in both directions HDSL (High-bit-rate DSL) –Designed as an alternative to the T-1 line VDSL (Very-high-bit-rate DSL) –Alternative to ADSL –Uses coaxial, fiber-optic, twisted-pair cable for short distances ( m) –Uses DMT with a bit rate of Mbps (downstream) and Mbps (upstream)

Spring 2006Data Communications, Kwangwoon University9-9 Traditional Cable TV Network Started to distribute video signals to locations with poor or no reception in the late 1940s: Unidirectional It was called Community Antenna TV

Spring 2006Data Communications, Kwangwoon University9-10 HFC (Hybrid Fiber Coaxial) Network RCH (Regional Cable Head) feeds the distribution hubs Fiber node splits the signal to each coaxial cable Communication in an HFC network can be bidirectional

Spring 2006Data Communications, Kwangwoon University9-11 Coaxial Cable Bands Video band: 6 MHz per TV channel Downstream data band: 64-QAM with TCM –Theoretical rate is 30 Mbps (6 Mbaud/sec * 5 bits/baud) Upstream data band: QPSK –Theoretical rate is 12 Mbps (6 Mbaud/sec * 2 bits/baud)

Spring 2006Data Communications, Kwangwoon University9-12 CM (Cable Modem)

Spring 2006Data Communications, Kwangwoon University9-13 CMTS (Cable Modem Transmission System)

Spring 2006Data Communications, Kwangwoon University9-14 SONET/SDH Digital transmission standards for fiber-optic cable Independently developed in USA & Europe –SONET(Synchronous Optical Network) by ANSI –SDH(Synchronous Digital Hierarchy) by ITU-T Multiplexed transport mechanism Carrier for ATM and B-ISDN

Spring 2006Data Communications, Kwangwoon University9-15 Interesting Features of SONET/SDH SONET/SDH is a synchronous network –A single clock is used across the entire network It contains the standards for fiber-optic equipments Very flexible to carry other transmission systems (DS-0, DS-1, etc)

Spring 2006Data Communications, Kwangwoon University9-16 SONET/SDH Rates SONET defines a signal hierarchy –STS (Synchronous Transport Signals) A hierarchy of signaling levels –OC (Optical Carriers) Physical links defined for optical signals –STS(OC)-1 (51Mbps)  STS(OC)-192 (10Gbps) SDH specifies a similar hierarchy –STM (Synchronous Transport Module) –STM-1 (155Mbps)  STM-64 (10Gbps) OC-1, OC-3, OC-12, OC-48, OC-192

Spring 2006Data Communications, Kwangwoon University9-17 SONET

Spring 2006Data Communications, Kwangwoon University9-18 Frame Format: STS-1

Spring 2006Data Communications, Kwangwoon University9-19 SONET Frames: STS-1

Spring 2006Data Communications, Kwangwoon University9-20 SONET Rates STSOCRate (Mbps)SPE (Mbps)User (Mbps) STS-1OC STS-3OC STS-9OC STS-12OC STS-18OC STS-24OC STS-36OC STS-48OC STS-192OC

Spring 2006Data Communications, Kwangwoon University9-21 Virtual Tributaries Partial payload that is inserted into an STS-1 frame Each component of subdivided SPE Provides backward compatibility Four types of VTs –VT1.5 : For DS-1(T-1: 1.544Mbps) –VT2: For CEPT-1(E-1: 2.048Mbps)

Spring 2006Data Communications, Kwangwoon University9-22 VT Types

Spring 2006Data Communications, Kwangwoon University9-23 STS Multiplexing

Spring 2006Data Communications, Kwangwoon University9-24 STS-n