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Infokommunikációs rendszerek9. előadás

ADSL

Takács György

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2004

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maximális letöltési sebesség (kbit/s)

maximális feltöltési sebesség (kbit/s)

Havidíj hűségnyilatkozattal (Ft)

ADSL Optimum 512 96 4900

ADSL Prémium 1024 128 7900

ADSL Maximum

2048 192 9900

  

                                                            

                

2006. november

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maximális letöltési sebesség (kbit/s)

maximális feltöltési sebesség (kbit/s)

Havidíj hűségnyilatkozattal (Ft)

DSL CLASSICHappy

2 Mbit/sec 192 kbit/sec

3 990 Ft

DSL CLASSIC MEDIUM

8 Mbit/sec 480 kbit/sec

6 890 Ft

DSL CLASSIC EXTRA

25 Mbit/sec

4 Mbit/sec 9 890 Ft

  

                                                            

                

2008. november

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2012. November

maximális (garantált)

letöltési sebesség (Mbit/s)

Maximális (garantált)

feltöltési sebesség (Mbit/s)

Havidíj 2 év hűségnyilatkozattal (Ft)

NetMániaS 10 (1) 0,5 (0,2) 3990

NetMániaM 20 (10) 1 (0,5) 4690

NetMániaL 30 (20) 1 (1) 5490

2015. November

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What is ADSL(VDSL) ?

• Asymmetric Digital Subscriber line,• A modem technology,• Convert existing twisted-pair telephone lines into

access paths for multimedia and high speed data communication,

• Can transmit to 30 Mbps downstream (VDSL 100 Mbps) ,

• Can transmit up to 20 Mbps upstream,• Transform the existing PSTN network to a

powerful system capable of bringing multimedia, full motion video to the subscriber’s home.

Infokom. 9. 2014. nov. 10. 8

ADSL system components

ADSL system components

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ADSL in the complete system (Application Service Provider, Internet Service Provider, ACCESS Network

Provider, Customer/User

Hálózattervezés 2014. nov. 12. 10

Infokom. 9. 2014. nov. 10. 11

ADSL components at the subscriber

Infokom. 9. 2014. nov. 10. 12

ADSL components at Central Office

Hálózattervezés 2014. nov. 12. 13

Hálózattervezés 2014. nov. 12. 14

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What is the future of the ADSL?

• Will play a crucial role over the next ten years for telephone companies and other service providers

• New broadband cabling will take decades to reach all prospective subscribers.

• EU regulation document on local loop unbundling because no competitive technology!

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dividing the spectrum to 256 subfrequencies

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       adaptive SNR discovery

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The technology being used is DMT which divides the frequency range to 256 sub-frequencies from 64Khz to 1.1Mhz Each sub-ferqency is an independent channel and has it own stream of signals . The ADSL protocol defines a basic stream of data which is known to both endpoints in advanced and enables them to find the specific SNR for each  sub-frequency , and uses this information to split the data over the sub-frequencies

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VDSL frequency plan and profiles

Hálózattervezés 2014. nov. 12. 21

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• Limiting factors:– Cable attenuation– Reflexion– Crosstalk (NEXT, FEXT)– Noises, interferences

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Infokom. 9. 2014. nov. 10. 24

key requirements (1)

• Test loops – makeup and topology (to ensure adequate penetration).

• Cross talk or steady state noise margin (to allow for interactions from other DSL in a multi-pair cable).

• Data rates (both line and payload). • Impulsive or transient noise margin (to allow for noise

spikes e.g. ringing). • Transmitter power spectral density limits (to ensure

spectral compatibility and minimise unwanted RF emissions).

• Return loss (to ensure good line matching and signal power transfer).

• Line interface balance (to prevent EMC problems).

Infokom. 9. 2014. nov. 10. 25

key requirements (2)

• Framing and data scrambling (to prevent cyclo-stationary effects e.g. line spectra).

• Latency (to minimise delay e.g. for voice traffic). • Jitter and wander (to minimise data loss). • Start up protocols (handshaking). • Warm/cold start limits (time taken to synchronise and

achieve reliable bit transport – to minimise circuit unavailability).

• Line coding (to achieve efficiency in terms of bits/s/Hz) • Duplexing (e.g. time, frequency, echo cancellation).

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key requirements (3)

• Forward error correction (to self-correct physical layer transmission errors and  not burden higher layer protocols with data re-transmission.)

• Embedded operations and maintenance (for the transfer of service related  information e.g. QoS).

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Code & Error Correction One of the most important technology breakthrough that helped the ADSL is the coding . Using a method called consellation encoding and based on Reed Solomon coding decoding the information on the line can be damaged and yet the decoder rebuild the information in a very high reliability.To improve the performance of ADSL system some companies use 16 state 4 dimensional trellis code on top of the consellation encoding. Another useful method to increase the ADSL systems reliability is Forward Error Correction (FEC).

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Framing & Scrambling   As most of the Computer communication networks the ADSL uses a specific framing method . The main frame is called Superframe and it is composed of 68 ADSL data frames , the ATU-C sends a superframe every 17 msec . Each data frame gets his information from two data buffers (interleaved buffer and fast buffer)which are scrambled at a specific sequence , this scrambling method makes the error correction and coding more efficient.

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DSLAM-s near to the PPKE-ITK Campus offered by the Hungarian Telecom (Reference Unbundling

Offer)

Hálózattervezés 2014. nov. 12. 30

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What can we learn from ADSL story?

• No ultimate technology!!• Frequency division multiplexing, time division

multiplexing, modulation, error control, flow control, scrambling, signal processing, adaptation, STM-ATM, trellis coding, in-service performance monitoring and surveillance, initialization, handshaking, channel analysis, are mixed in ADSL

• More room for further development….