chapter 9. high-speed digital access: dsl, cable modems, and sonet
DESCRIPTION
9.1 Digital Subscriber Line (DSL) uses a newer technology that used the existing telecommunications networks such as the local loop telephone line. is an asymmetric communication technology designed for residential users; it is not suitable for business. xDSL: where x can be replaced by A, V, H, or S The existing local loops can handle bandwidths up to 1.1 MHz by removing the filter at the end of line of telephone company but, limitation because of distance between the residence and the switching office, size of cable ADSL is an adaptive technology. The system uses a date rate based on the condition of the local loop lineTRANSCRIPT
11Kyung Hee Universit
y
Chapter 9.Chapter 9.High-Speed Digital Access: High-Speed Digital Access:
DSL, Cable Modems, and DSL, Cable Modems, and SONETSONET
22Kyung Hee Universit
y
9.1 Digital Subscriber Line (DSL)9.1 Digital Subscriber Line (DSL) uses a newer technology that used the existing telecommunication
s networks such as the local loop telephone line.
is an asymmetric communication technology designed for residential users; it is not suitable for business.
xDSL: where x can be replaced by A, V, H, or S
The existing local loops can handle bandwidths up to 1.1 MHz
by removing the filter at the end of line of telephone company but, limitation because of distance between the residence and
the switching office, size of cable
ADSL is an adaptive technology. The system uses a date rate based on the condition of the local loop line
33Kyung Hee Universit
y
DSLDSLDMT
Modulation technique that has become standard for ADSL is called the discrete multitone technique (DMT) which combines QAM and FDM.
44Kyung Hee Universit
y
DSLDSL
voice : channel 0 is reserved for voice
Idle : channel 1 to 5 are not used; gap between voice and data communication
Upstream data and control : channels 6 to 30 (25channels); one channel for control
Downstream data and control : channels 31 to 255(225 channels); 13.4 Mbps; one channel for control
55Kyung Hee Universit
y
DSLDSL
Actual Bit Rate Upstream : 64 Kbps to 1 Mbps Downstream : 500 Kbps to 8 Mbps
* Because of the high signal/noise ratio
66Kyung Hee Universit
y
ADSL Frequency SpectrumADSL Frequency Spectrum
77Kyung Hee Universit
y
ADSLADSL
88Kyung Hee Universit
y
DSLDSL
Customer site : ADSL modem
99Kyung Hee Universit
y
DSLDSL
Telephone Company Site : DSLAM
1010Kyung Hee Universit
y
DSLDSL
Other DSL Technologies SDSL: Symmetric Digital Subscriber Line HDSL: High-bit-rate digital subscriber line
an alternative to the T-line (1.544 Mbps) using 2B1Q encoding up to 3.6 Km using 2 twisted-pair wires for full-duplex transmission
VDSL : Very-high-rate digital subscriber using coaxial cable, fiber-optic, or twisted pair cable for
short distances (300 to 1800 m) using DMT with a bit rate of 50 to 55 Mbps downstream and
1.5 to 2.5 Mbps upstream
1111Kyung Hee Universit
y
9.2 Cable Modem9.2 Cable Modem Traditional cable Networks
community antenna TV (CATV)
Communication in the traditional cable TV network is unidirectional.
1212Kyung Hee Universit
y
Cable ModemCable Modem HFC Network
RCH : Regional cable head; serving 400,000 subscribers; Distribution hub: serving 40,000 subscribersCoaxial cable : serving 1,000 subscribers Communication in HFC cable TV network can be bidirectional.
1313Kyung Hee Universit
y
Cable ModemCable Modem
Bandwidth
video band 54 to 550 MHz TV channels : 6 Mhz x 80 channels
Data downstream band : dividing into 6Mhz channels
1414Kyung Hee Universit
y
Cable ModemCable Modem Modulation
Downstream data are modulated using 64-QAM Data rate
6 bits for each baud in 64-QAM (1bit : control bit) Theoretically, 5bits/Hz x 6 Mhz = 30 Mbps
Upstream data band Modulation
upstream data band uses lower frequencies that are more susceptible to noise and interference
for this reason, using QPSK instead of QAM Data rate : 2 bits/hz x 6 Mhz = 12 Mbps
1515Kyung Hee Universit
y
Cable ModemCable Modem
CM is installed inside the distribution hub by the cable company.
1616Kyung Hee Universit
y
Cable ModeCable Mode
Cable modem transmission system (CMTS)
1717Kyung Hee Universit
y
9.3 SONET9.3 SONET
Synchronous Optical Network : ANSI standard
Synchronous Digital Hierarchy :SDH
SONET is a synchronous TDM system controlled by a master clock
1818Kyung Hee Universit
y
SONETSONET
SONET Frame
* SPE : synchronous payload envelope
1919Kyung Hee Universit
y
SONETSONET SONET rates
STS
OC Rate (Mbps) SPE (Mbps) User (Mbps)
STS-1STS-1 OC-1 51.84 50.12 49.536
STS-3STS-3 OC-3 155.52 150.336 148.608
STS-9STS-9 OC-9 466.56 451.008 445.824
STS-12STS-12 OC-12 622.08 601.344 594.432
STS-18STS-18 OC-18 933.12 902.016 891.648
STS-24STS-24 OC-24 1244.16 1202.688 1188.864
STS-36STS-36 OC-36 1866.23 1804.032 1783.296
STS-48STS-48 OC-48 2488.32 2405.376 2377.728
STS-192STS-192 OC-192 9953.28 9621.604 9510.912
2020Kyung Hee Universit
y
SONETSONET
Date Rates
2121Kyung Hee Universit
y
SONETSONET
STS Multiplexing