JPL's Wireless Communication Reference Website

Chapter: Analog and Digital Transmission
Section: Multi-Carrier Modulation, OFDM, Effect of Doppler

Effect of Doppler for OFDM and Synchronous MC-CDMA

Contributed by Jean-Paul Linnartz

The OFDM receiver structure allows relatively straightforward signal processing to combat channel delay spreads. However, mobile reception leads to disadvantageous channel conditions, with both (frequency) dispersion and rapid variations of the channel with time. Doppler spread and the corresponding time variations are known to corrupt the orthogonality of the OFDM subcarrier waveforms. In such case, Intercarrier Interference (ICI) occurs because signal components from one subcarrier cause interference to neighboring subcarriers.

This spreadsheet allows you to interactively experiment with the effect of mobility. The channel model is Rayleigh fading with a U-shaped spectrum.

InterCarrier Interference for
OFDM in a Rayleigh fading channel

Input parameters:
Carrier frequency
MHz
Speed
m/s
Frame size
(excluding guard time) 		subcarriers
Symbol rate
Number of QAM symbols per second 		ksymbol/sec
Symbol rate
Es/N0
Energy per subcarrier over spectral power density of the AWGN. Used for BER calculation. 		dB
 
 
fsub
Subcarrier spacing. 		Hz
fDoppler
Doppler spread. 		Hz

Results for Intercarrier Interference
P0
Local mean of wanted signal component. 		dB = ()
P1
Variance of first-order ICI, i.e., from neighboring subcarriers. 		dB = ()
P2
Variance of second-order ICI. 		dB = ()
P3
Variance of third-order ICI. 		dB = ()
P0 / SUM Pi
Signal-to-ICI ratio 		dB = ()

Results for BER

BER for BPSK uncoded OFDM  
BER for BPSK MC-CDMA  

 

See also the spreadsheet for QPSK and QAM.



JPL's Wireless Communication Reference Website © 2000.

 

Publication for scientific reference:

PDF J.P.M.G. Linnartz, "Performance Analysis of Synchronous MC-CDMA in mobile Rayleigh channels with both Delay and Doppler spreads", IEEE VT, Vol. 50, No. 6, Nov. 2001, pp 1375-1387.