The document compares multi-carrier (DMT) and single carrier modulation techniques. DMT divides the available spectrum into multiple sub-carriers, each with a low symbol rate, allowing different modulation schemes per sub-carrier. Single carrier modulation uses a single carrier to transmit all data simultaneously. DMT offers higher bandwidth efficiency and throughput through bit loading and simpler equalization, while single carrier modulation provides simpler implementation through a single equalizer but lower spectrum utilization. The author is Fernando Ramirez-Mireles, a professor specializing in digital signal processing and communications engineering.

1. MultiCarrier
vs
Single Carrier
Fernando Ramirez-Mireles, Ph.D.
ramirezm@ieee.org, framirez@itam.mx
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
1
framirez@itam.mx

2. MultiCarrier (Discrete Multi Tone DMT) and Single Carrier Modulation (SCM)
Mr. FEC
DISCRETE MULTI TONE (Divide and Conquer) SINGLE CARRIER MODULATION
Signal PSD (dBm/Hz)
Signal PSD (dBm/Hz)
US1 DS1 US2 DS2 US3 US1 DS1 US2 DS2 US3
Frequenc Frequenc
freq. freq. freq. freq. freq. freq. freq. freq. freq. freq.
y y
1 2 3 4 5 1 2 3 4 5
(MHZ) (MHZ)
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
2
framirez@itam.mx

3. Multicarrier (DMT)
Processing
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
3
framirez@itam.mx

4. SCM Processing
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
4
framirez@itam.mx

5. Comparing Multicarrier (DMT) and SCM
Issues Deleterious DMT solution SCM solution Advantages of
effects DMT over
SCM
Channel Signal Equalization: Two simple Equalization: Simplicity in
Time Smearing equalizers, one in time One complicated design and
Dispersion domain and one in equalizer in time implementation
frequency domain domain
Frequency Frequency Bit loading: Transmit No bit loading: Bandwidth
dependent dependent more bits in frequency Transmit the efficiency and
Noise signal-to- bands where there is less same average higher throughput
noise ratio noise and less bits in number of bits in
(SNR) frequency bands where every frequency
there is more noise band regardless
of amount of
noise in each
frequency band
FDD full Interference Signal separation: Use no Signal Higher spectrum
duplex between filtering, utilize Fourier separation: Use utilization, higher
operation in upstream Transform orthogonality one complicated throughput and
multi-band and properties filter per flexible
spectrum downstream transmission implementation of
plans signals band different band
plans
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
5
framirez@itam.mx

6. FERNANDO RAMIREZ-MIRELES
ramirezm@ieee.org
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
6
framirez@itam.mx

7. About the author
Fernando has over 10 years of experience in
R&D in VDSL, UWB and speech processing.
He has worked in the DSL field as a systems
and algorithms engineer. He is currently a
professor in the engineering division at ITAM in
Mexico City. He has authored more than
twenty technical articles and has one patent
granted and two more pending. He is a senior
member of the IEEE. He can be reached at
ramirezm@ieee.org.
Multi Carrier vs. Single Carrier
Copyright 2012 Fernando
Ramirez-Mireles ramirezm@ieee.org,
7
framirez@itam.mx