Summary: ETRI Journal, Volume 29, Number 1, February 2007 Mohd. Hasan et al. 79
This paper proposes a novel concept of adjusting the
hardware size in a multi-carrier code division multiple
access (MC-CDMA) receiver in real time as per the
channel parameters such as delay spread, signal-to-noise
ratio, transmission rate, and Doppler frequency. The fast
Fourier transform (FFT) or inverse FFT (IFFT) size in
orthogonal frequency division multiplexing (OFDM)/MC-
CDMA transceivers varies from 1024 points to 16 points.
Two low-power reconfigurable radix-4 256-point FFT
processor architectures are proposed that can also be
dynamically configured as 64-point and 16-point as per
the channel parameters to prove the concept. By tailoring
the clock of the higher FFT stages for longer FFTs and
switching to shorter FFTs from longer FFTs, significant
power saving is achieved. In addition, two 256 sub-carrier
MC-CDMA receiver architectures are proposed which
can also be configured for 64 sub-carriers in real time to
prove the feasibility of the concept over the whole receiver.
Keywords: MC-CDMA, FFT, architecture, VLSI design.