1 / 35

Transport Methods in Access Networks and other subsidiary information

Explore the classification and utilization of methods for digital signal transport in access networks, including link codes, modulation techniques like PSK and QAM, and DMT modulation. Understand the principles behind AMI, HDB3, PSK, QAM, and other signal transport methods, with detailed illustrations and explanations. Learn about the benefits and challenges of different link codes, modulation types, and spectral efficiency considerations for efficient data transmission.

gborja
Download Presentation

Transport Methods in Access Networks and other subsidiary information

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Transport Methods in Access Networks and other subsidiary information Access Networks lectures 2008 / 09

  2. data speed (transmission speed) = number of bits pre second - vp[bps] modulation rate = number of symbols per second - vm[Bd]  relation between them: m – number of states of given ‘alphabet’. Each of state (each ‘character’ of code) is expressed by N bits  m = 2N  N = … (?) vp = N . vm  …. band width fh= around vm

  3. ….. but: because of ingress and other disturbing the m must be less then 2N - there must be some distance (space, gap) to ensure good resolution (of states) • there must be choosen such method of transmission – - which allows as narrow frequency band as possible - which ensures at least minimal SNR

  4. Classification of Methods for Digital Signal Transport in the baseband : link codes (AMI, HDB3, 2BQ1, …) and PAM in the modulation band (passband) : modulated signals (PSK, QAM, CAP, DMT) Utilisation of available bandwidth – by means: multistate encoding or modulation numbers of parallel transport paths (so called inverse multiplexing), more carriers scrambling generation of pseudonoise sequence  equalization (or unification) of density of power spectrum Duplex transport – types... – we have it classified more long time before

  5. Link codes - - binary data in the frame of physical layer (of OSI model) – lowest level = electric signal coresponding to “0” and “1” or to binary symbols Fig. 1

  6. Link codes Fig. 2 Ilustration of link coding– voltage levels corresponding to individual binary symbols; transport in the baseband, i.e. low frequences + eventually also DC [2]

  7. Link codes Classification • by number of levels: 2-levels • 3-levels (AMI, HDB3, 4B3T) • - multilevels (2B1Q) • -unipolar • --bipolar • Return to Zero (RZ) • - Non Return to Zero (NRZ) - their specifical properties (advantages and disadvantages – power requirements, freq. spectrum requirements, synchronization problems)

  8. Link codes Fig.3 Illustration of Return-to-Zero Code (RZ)

  9. Link codes Non-return–to-Zero L code bipolar (polarity alternating) pseudoternary Fig.4 Illustration of different types of link codes[5]

  10. Link codes bipolar (Alternate Mark Inversion) - for PCM 30/32 (bipolar with 8 zeros substitution) (for PDH-E1,E2,E3) B – correct bipolar signal V – violation - ‘artificial’ (for good synchroniz. and detection) Fig .5 AMI, B8ZS and HDB3 link codes[5]

  11. Link codes - NRZ (for PDH- E4) Fig.6 - on 10 Mbps LAN interfaces Fig.7

  12. 2B1Q code Tab.1 for U interface of ISDN-BRA, and HDSL Link codes [5] Fig.8

  13. Multistate methods: for transport in baseband .... they decrease frequence bandwidth requirements... • PAM modulation original PAM time [Wikipedia] Fig.9 PAM modulation - for transport in baseband - there is utilised 8-PAM and 16-PAM – in SDSL lines and others, in Ethernet, there is 5-PAM

  14. PSK (Phase Shift Keying) • QAM (Quadrature Amplitude Modulation) Modulation types in passband Tab.2 Review of some PSK and QAM modulations

  15. QPSK - Quadrature Phase-Shift Keying φ = 0° φ = 180° b) QPSK a) BPSK (Binary PSK) Fig.10 Principle of BPSK and QAM[Wikipedia]

  16. Fig. 11 QPSK transmitter Fig. 12 QPSK receiver

  17. Fig. 13 Vector signal (I-Q) - principle

  18. QAM - a modulation scheme which conveys data by changing (modulating) the amplitude of two carrier waves. These two waves, usually sinusoids, are out of phase with each other by 90° and are thus called quadrature carriers—hence the name of the scheme.

  19. 0000 0001 0011 0010 Fig.14Constellation diagram of 16-QAM (rectangular QAM)

  20. equiphase (in-phase) trace quadrature signal data flow splitter quadrature trace Fig.15 Blockdiagramof QAM modulator

  21. CAP – modulation- (Carrierless Amplitude and Phase) Instead of modulating the amplitude of two carrier waves, CAP generates QAM signal by combining two PAM signals filtered through two filters designed so that their impulse responses form a Hilbert pair. [1]

  22. CAP – modulation- (Carrierless Amplitude and Phase) Fig. 16 CAP signal transmitter [1] Fig.17 CAP signal receiver

  23. Fig.18 [1]

  24. DMT Modulation- discrete multitone techniques - very efficient technology in comparison with older ones : ... DMT modulation: a) symbols constellation, b) time running (unreadable, isn’t it? ), c) frequence spectrum Fig.19

  25. Fig.20 DMT transmitter [1] Fig. 21DMT receiver

  26. OFDM It is the subject-matter for a long lecture, but at same time, it is an application of the known system: It deals with signal transport by means of system of FDM carriers. The neigbouring frequency carriers are orthogonal each to other  it is result of Fast Fourier Transform in practice (FFT and IFFT blocks in codecs). The particular carriers are phase- and amplitude- modulated by I-Q modulation, i.e. QAM. That is the basis of DMT technics. source: http://kupluk2.blogspot.com/2010/03/what-ofdm-means-to-wimax.html

  27. sources: http://infowimax.blogspot.com/2008/05/un-panorama-de-ofdm.html http://www.iss.rwth-aachen.de/Projekte/Theo/OFDM/OFDM_en.html http://connectedplanetonline.com/wireless/technology/mimo_ofdm_091905/

  28. Trellis modulation • In telecommunication, trellis modulation (also known as trellis coded modulation, or simply TCM) is a modulation scheme which allows highly efficient transmission of information over band-limited channels such as telephone lines. Trellis modulation was invented by Gottfried Ungerboeck in 1982. • ... • [Wikipedia]

  29. Packet andcellular transport modes • ATM Synchronous transport mode 5th channel interval (1 Byte) 5th channel interval (1 Byte) frame (32 Bytes) frame asynchronous transport mode head (5 Bytes) empty cell cell (53 Bytes) Packet transport no-data packet Fig.22

  30. ATM plane management layer management control plane user plane adaptation layer layer physical layer Fig. 23 ATM layer model

  31. Tab.3 Service classes related to ATMadaptation layers

  32. Another appendices

  33. ISDN – line – for rarely connecting to the Internet. (It is only appendix for lecture 3 presentation.) Fig.24 llustration of ISDN lines [2]

  34. Tab.4Ethernet technologies on twisted pairs [2]

  35. References [1] http://www.nextep.com.au/upload/DSL_Modulation_Techniques.pdf [2] T. Anttalainen: Introduction to Telecom. Network Engineering, Norwood (USA - MA), 2003. [3] Vaculík: Prístupové siete. ŽU v Žiline, 2000. [4] J. Vodrážka: Přenosové systémy v přístupové síti. ČVUT, 2003. [5] www.ktl.elf.stuba.sk/~oravec/folie/Linkove%20kody.pdf

More Related