Tunable Wordlength Architecture for a Low Power Wireless OFDM Demodulator

Shingo YOSHIZAWA  Yoshikazu MIYANAGA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A   No.10   pp.2866-2873
Publication Date: 2006/10/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.10.2866
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: VLSI Design Technology and CAD
wireless communication,  variable wordlength,  VLSI architecture,  OFDM,  

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We present a low power architecture that dynamically controls wordlengths in a wireless OFDM demodulator. Finding the optimum wordlength for digital circuit systems is difficult because the trade-off between the hardware cost and system performance is not conclusive. Actual circuit systems have large wordlengths at the circuit design level to avoid calculation errors caused by a lack of dynamic range. This indicates that power dissipation can still be reduced under better conditions. We propose a tunable wordlength architecture that dynamically changes its own wordlength according to the communication environment. The proposed OFDM demodulator measures error vector magnitudes (EVMs) from de-modulated signals and tunes the wordlength to satisfy the required quality of communication by monitoring the EVM performance. The demodulator can reduce dissipated energy by a maximum of 32 and 24% in AWGN and multipath fading channels.