chapter 6 ofdm dmt for wireline communications n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 6 OFDM/DMT for Wireline Communications PowerPoint Presentation
Download Presentation
Chapter 6 OFDM/DMT for Wireline Communications

Loading in 2 Seconds...

play fullscreen
1 / 45

Chapter 6 OFDM/DMT for Wireline Communications - PowerPoint PPT Presentation


  • 158 Views
  • Uploaded on

Chapter 6 OFDM/DMT for Wireline Communications. School of Info. Sci. & Eng. Shandong Univ. CONTENT. 6.1 Discrete MultiTone (DMT) and Wireline Channel Properties 6.2 Optical OFDM Transmission and Optical Channel Properties 6.3 Impulse-Noise Cancellation

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 6 OFDM/DMT for Wireline Communications' - zuriel


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 6 ofdm dmt for wireline communications

Chapter 6 OFDM/DMT for Wireline Communications

School of Info. Sci. & Eng.

Shandong Univ.

content
CONTENT
  • 6.1 Discrete MultiTone (DMT) and Wireline

Channel Properties

  • 6.2 Optical OFDM Transmission and Optical

Channel Properties

  • 6.3 Impulse-Noise Cancellation
  • 6.4 Dual Polarization Optical OFDM Transmission
  • 6.5 Forward Error Correction
  • 6.6 Summary
properties of the twisted pair channel
Properties of the Twisted-Pair Channel
  • Transfer Characteristic:
near end crosstalk next and far end crosstalk fext
Near-end Crosstalk (NEXT) and Far-end Crosstalk (FEXT)
  • NEXT results from coupling from other loops in the same cable from transmitters located at the same side as the own receiver. NEXT (as a power contribution) is modeled as:

where N is the number of identical disturbers and the power of 0.6 is to halfways model the distribution of disturbers in cable.

near end crosstalk next and far end crosstalk fext1
Near-end Crosstalk (NEXT) and Far-end Crosstalk (FEXT)
  • FEXT results from coupling from other lo ops in the same cable from transmitters located at the opposite side of the own receiver. FEXT (as a power contribution) is modeled as:

where N is the number of identical disturbers, l is the length of the coupling length, and the power of 0.6 is to halfways model the distribution of disturbers in the cable

near end crosstalk next and far end crosstalk fext3
Near-end Crosstalk (NEXT) and Far-end Crosstalk (FEXT)
  • The so-called Equal-Level FEXT (EL-FEXT) is defined by eliminating the length dependency and the transfer function:
near end crosstalk next and far end crosstalk fext4
Near-end Crosstalk (NEXT) and Far-end Crosstalk (FEXT)

Measured NEXT of an 0.4-mm layered cable

near end crosstalk next and far end crosstalk fext5
Near-end Crosstalk (NEXT) and Far-end Crosstalk (FEXT)
  • Measured NEXT of an 0.4-mm layered cable
radio frequency interference rfi and impulse noise
Radio-frequency Interference (RFI) and Impulse Noise
  • Non-symmetries are characterized by unbalance parameters like Longitudinal Conversion Loss (LCL), Transverse Conversion Loss (TCL), Longitudinal Conversion Transfer Loss (LCTL),and Transverse Conversion Transfer Loss (TCTL).
  • The duration of an impulse follows roughly follows a combination of two log-normal densities in the form:
radio frequency interference rfi and impulse noise1
Radio-frequency Interference (RFI) and Impulse Noise

Impulses resulting from welding and fluorescent tubes, measured at a telephone socket

discrete multitone dmt
Discrete MultiTone (DMT)

Components of DMT transmission

two sided processing for mimo based on svd
Two-Sided Processing for MIMO Based on SVD
  • The singular-value decomposition rephrases the channel matrix in DFT domain H ( n) at carrier number n as:

Λ(n) is a diagonal matrix. P (n ) and Q (n) are unitary matrices.

two sided processing for mimo based on svd1
Two-Sided Processing for MIMO Based on SVD
  • Let t (n) and r(n ) be input and output vectors, respectively. At the transmitter side, we multiply the signal t(n ) by P (n ). Whereas, the signal

at the receiver is multiplied by QH( n) to obtain the output r(n ):

two sided processing for mimo based on svd2
Two-Sided Processing for MIMO Based on SVD
  • Using the SVD,we obtain:

x (n) is the product of P ( n) and t (n )

two sided processing for mimo based on svd3
Two-Sided Processing for MIMO Based on SVD
  • OFDM and SVD as Reed-Solomon or RS-like codes RS codes are commonly defined as follows
  • the structures of OFDM and SVD:
qr decomposition for upstream processing
QR decomposition for upstream processing
  • For upstream processing we write the L × L channel matrix as (In the following, we omit the carrier index n): H=QR
  • With a unitary matrix Q and an upper triangular matrix R .Working with column vectors for information and received values, a post-processing with QH leads to:
qr decomposition for upstream processing1
QR decomposition for upstream processing

Spatial DFE structure resulting from QR decomposition

qr decomposition for downstream processing
QR decomposition for downstream processing
  • For downstream processing, the idea is to apply a QR decomposition to the transpose of the channel matrix. This enables us to do a pre-processing instead of the post-processing of the previous paragraph. We hence obtain:
  • The diagonal matrix is added to obtain a similar structure in the following formula . Equation can equivalently be rephrased as:
qr decomposition for downstream processing1
QR decomposition for downstream processing

QR decomposition for downstream processing

optical ofdm transmission and optical channel properties
Optical OFDM Transmission and Optical Channel Properties
  • Commercially available systems for high bit-rate optical data transmission utilize on-off-keying or differential phase shift keying (DPSK) and reach bit-rates up to 40 Gbit/s.
  • A straightforward approach is bit-interleaved coded modulation with iterative decoding (BICM-ID) , which can be considered as the most simple approach to achieve high spectral efficiency while providing a low decoding complexity.
common mode and differential mode
Common Mode and Differential Mode
  • Differential-Mode (DM) signals have been the conventional approach of transmission over copper cables.
  • Common-Mode (CM) signals are taken as the arithmetic mean of the two signals measured with respect to ground, which makes them prone to interference.
  • Both DM and CM signals are readily available on the receiver side:
coupling and transfer functions
Coupling and Transfer Functions
  • Transfer functions for DM and CM obtained from measurements of a 0.4 mm Swiss cable of length 100 m
coupling and transfer functions1
Coupling and Transfer Functions
  • NEXT coupling functions, obtained from measurements of different TPs in the bundle. The outlier is due to measuring the other TP in the same star quad
coupling and transfer functions2
Coupling and Transfer Functions
  • FEXT coupling functions, obtained from measurements of different TPs in the bundle. The outliers are due to measuring adjacent TPs
common mode reference based canceler
Common-Mode Reference-Based Canceler
  • Impulse noise generated from light switching, both in DM and CM
impulse noise detection and cancellation detection
Impulse Noise Detection and Cancellation—Detection
  • For the first method , in order to obtain the envelope, the CM is split into non overlapping frames of size M .Out of every frame, the maxim value is chosen and interpolation is performed among all local maxima.

Envelope of CM signal (green)

impulse noise detection and cancellation detection1
Impulse Noise Detection and Cancellation—Detection
  • A second method which can be easily implemented in the analog domain uses a rectifier and a low pass filter to detect the envelope of the CM signal :

Second method for CM envelope detection

simulation results
Simulation Results
  • The green line depicts the overall received DM signal, which is corrupted by impulsive noise, while the black waveform illustrates the same DM signal, impulse noise free.
  • The red line presents the ideal transmitted signal, with no interference, only attenuated by the loop.
dual polarization optical ofdm transmission
Dual Polarization Optical OFDMTransmission

Investigated system: Dual polarization OFDM transmission, coherent detection.

noise variance estimation
Noise Variance Estimation
  • The transmission of symbol vectors[X1(d) X2(d)]T on sub-carrier d can be written as:
  • Then the relative noise variance for both receive branches can be determined:
noise variance estimation1
Noise Variance Estimation

Estimated relative noise power

achievable spectral efficiency
Achievable Spectral Efficiency
  • According to Shannon the maximum information-rate which can be transmitted over a band-limited additive white Gaussian noise channel is:
  • The contributions of the orthogonal polarizations are added up. Furthermore we average over the OFDM sub-carriers:
achievable spectral efficiency1
Achievable Spectral Efficiency
  • The investigated transmission system is assumed to consist of equally spaced, identical optical amplifiers. The optical SNR (OSNR) after Nspans amplifiers is given by:

Here h and c denote Planck’s constant and the speed of light, respectively. G is the amplifiers’ gain which shall equal the loss of one fiber span. The noise figure is given by FN

achievable spectral efficiency2
Achievable Spectral Efficiency
  • Achievable spectral efficiency versus distance and launch power
achievable spectral efficiency3
Achievable Spectral Efficiency
  • Achievable spectral efficiency vs. distance
adc dac resolution
ADC/DAC Resolution
  • Achievable spectral efficiency versus distance considering quantization noise.
forward error correction
Forward Error Correction

Iterative demapping and decoding, BICM-ID system configuration

forward error correction1
Forward Error Correction
  • The function btst (i, h ) takes the value ‘1’if bit number h is set in the binary decomposition of i, otherwise it is ‘0’ where:
  • When the channel symbols z are corrupted by complex Gaussian noise, the conditional PDF calculates to:
forward error correction2
Forward Error Correction
  • The soft-demapping algorithm of for the complex AWGN channel as:
influence of the applied mapping
Influence of the Applied Mapping
  • For anti-Gray mapping a quite high SNR is required to reach the so called “turbo cliff”, which is the required SNR at which the decoding process starts to deliver an iteration gain.
  • The symbols within a CW are mapped to a ratio of α according to Gray and to a ratio 1 − α according to anti-Gray:
simulations on the performance of coded ofdm
Simulations on the Performance of Coded OFDM

Complete optical COFDM system

simulations on the performance of coded ofdm1
Simulations on the Performance of Coded OFDM

Simulations on systems performance; BER at BICM-ID output

simulations on the performance of coded ofdm2
Simulations on the Performance of Coded OFDM

EXIT functions of decoder and soft-demapper for different mappings at optical input power of -9 dBm

summary
Summary
  • This chapter gave an impression of some of the research issues related to the wireline use of multicarrier modulation. Many aspects are similar as in wireless, but the channels offer different possibilities or have other challenges, such as, e.g., more stationary behavior, an additional common mode in twisted-pair, or non-linearities in optical communication.
  • We adapted the principle of an iterative decoding scheme, namely BICM-ID, to our system. The obtained results for the investigated optical OFDM system promise to reach a spectral efficiency of 8 bit/s/Hz for a 960 km fiber link.