Sistem Broadband Pertemuan 13

Matakuliah : H0122 / Dasar TelekomunikasiTahun : 2008

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Mahasiswa dapat menyebutkan sistem akses broadband yang telah

digunakan.

Learning Outcomes

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• X-DSL• Modem Kabel

Outline Materi

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• The need broadband system is due to the user demand for speed on the order of Mbps for internet access and other applications.

• The bandwidth of the basic POTS analog is limited.• High Speed means Megabits at least in one

direction, always on for continuous connection to the outside world and bidirectional.

• High speed from the home as well as to the home.

Broadband

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Access Choices

• Many different approaches– Twisted pair (xDSL)– Hybrid fiber-coax cable (cable modem)– Fixed wireless– Satellite (two-way)– Fiber to the home or curb (Gigabit

Ethernet)– Power line– Digital terrestrial

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Access Choices

Determining Factors:• Population density• Existing infrastructure (e.g., twisted pair, cable, fiber)• Government policies• Competitive and regulatory dynamics• Technology evolution

Farm

Homes

MDUGigE Fiber

Cable modem

Twisted pair DSL

Satellite

High-rise multi-dwelling units

Individual single units

Isolated single units

Communication Network

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Digital Subscriber Line

• Digital Subscriber Line (DSL) technology is one of the most supporting high-speed digital communication over the existing local loops. DSL provides high speed access over local loops.

• The various types of DSL are called xDSL family = {A,S,H,V}DSL

• Twisted Pair cables used for local loops has a bandwidth of 1.1MHzTelephone companies limit the bandwidth to 4KHz using filters (sufficient for voice communication), to allow multiplexing of large number of voice channels

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Types of xDSL

• SDSL : Symmetrical DSL, the bandwidth partitioningis symmetrical, suitable for businesses

• ADSL : Asymmetric Digital Subscriber Line• HDSL : High-bit-rate DSL (repeaterless E1)• RADSL : Rate Adaptive DSL for noisy lines• VDSL : Very-high-speed DSL upstream 50-56 Mbps,

coaxial, fiber-optic, or TP for higher rates over short distances (300-1800m)

• G.Lite : Slower version of ADSL eliminatingneed for POTS Splitter (filter) at customer. Provides up to 1.5 Mbps down, 128 Kbps up

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• Asymmetric– Asymmetry in upstream and downstream

connection, higher bandwidth downstream (to subscriber), lower bandwidth upstream (to Internet)

• Frequency division multiplexing– Lowest 25kHz for voice (POTS)– Use echo cancellation or FDM to give two bands– Use FDM within bands

• The existing local loops can handle bandwidths up to 1.1 MHz. Range 5.5km

• ADSL is a link between subscriber and network and uses currently installed twisted pair cable

ADSL

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• ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line.

• Factors like the distance between the residence and switching office, line quality, and signaling used affect the data rate

• ADSL tests the condition and the bandwidth availability before deciding on a data rate

• ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses.

ADSL

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Channel Configuration

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System Configuration

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Cable TV Network

• The cable TV network is a video service provider, it can be used to provide high-speed access to the Internet.•Communication in the traditional cable TV network

is unidirectional.•Communication in an HFC cable TV network can be

bidirectional.•Downstream data are modulated using the 64-QAM

modulation technique.• The theoretical downstream data rate is 30 Mbps.•Upstream data are modulated using the QPSK

modulation technique.• The theoretical upstream data rate is 12 Mbps.

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Hybrid fiber-coaxial (HFC)

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Cable Modem Configuration

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•Downstream–Cable scheduler delivers data in small packets–If more than one subscriber active, each gets fraction of downstream capacity (may get 500kbps to 1.5Mbps)

–Also used to allocate upstream time slots to subscribers

•Upstream–User requests timeslots on shared upstream channel (dedicated slots for this).

–Headend scheduler sends back assignment of future tme slots to subscriber.

Cable Modem Operations

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• Telah dipelajari XDSL.• Telah dipelajari Modem Kabel.

Summary