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This page on OFDM vs DMT describes similarity between OFDM and DMT as well as difference between OFDM and DMT technologies.

OFDM stands for Orthogonal Frequency Division Multiplexing and DMT stands for Discrete Multi-tone. ADSL system uses either OFDM or DMT.

Similarity between OFDM and DMT

Following are the similarities between OFDM and DMT.

•  OFDM and DMT both are modulation techniques.

•  Both are multicarrier communication systems implemented digitally by means of FFT(Fast Fourier Transform).

•  All the subcarriers are orthogonal in both the techniques.

•  Both uses cyclic prefix(guard interval) which helps reconstruct data at the receiver. Cyclic prefix contains samples copied from the last part of the symbol and appended at the start of the same symbol. Refer what is cyclic prefix for more information.

Difference between OFDM and DMT

Following are the differences between OFDM and DMT.

•  DMT refers to baseband wireline multicarrier communication, while OFDM is wireless multicarrier communication system. Refer OFDM physical layer used in wimax to understand the basic concepts.

•  As the channel is usually slow varying DMT allows spectral shaping by bit loading to take benefits of measured channel characteristics.

•  DMT is used in ADSL while OFDM is used in wireless communication systems such as WLAN, WiMAX etc. Variant of OFDM referred as OFDMA is widely used in upcoming next generation wireless communication technologies such as LTE and LTE-Advanced.

•  DMT is implemented by FFT is orthogonal FDM. OFDM implemented by FFT is discrete multi-tone. Refer following links to know difference between FDM and OFDM.


OFDM Frame Structure and comparison with OFDMA
Basics of OFDM and difference between FDM and OFDM

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