Dynamic wordlength calibration to reduce power dissipation in wireless OFDM systems

Abstract

Abstract-This paper describes low power architecture by using a dynamic wordlength technique in wireless orthogonal frequency division multiplexing (OFDM) system. The number of wordlength in digital signal processing (DSP) has to be carefully determined because wordlength affects system performance and hardware cost. Dynamic wordlength technique is applied to a fast Fourier transform (FFT) processor and a Viterbi decoder in OFDM receiver. The proposed method searches an optimum wordlength combination of FFT processor and Viterbi decoder by comparing output binary data while changing wordlengths. This operation is done by use of intervals in packet waiting. This approach leads to achieve the power reduction up to 23.9% with a desirable packet error rate (PER) in multipath channel environment.

Energy-Aware Computing via Adaptive Precision under Performance Constraints in OFDM Wireless Receivers

“…In [5], modifications are introduced in the OFDM frame to save up to 30.2% of the energy. In [6], multiple calculations are needed to estimate the channel conditions, reducing the amount of energy saved (23.9%). Our savings are higher without modifying the OFDM frame.…”

“…LTE, DVB, DAB, 802.11a/g/n). Prior literature [3][4] [5] [6] focused on the use of adaptive bit-width in OFDM receivers. In [4], intensive simulations have been used to optimize the Fast Fourier Transform (FFT), the most consuming block in an OFDM system.…”

“…This method has the drawback of modifying the OFDM frame specified in the standards, because a search symbol is inserted in order to estimate the quality of the received signal. Some improvements are made in [6] with the addition of a Viterbi decoder. Yet, a high number of iterative operations is needed to find the correct wordlength, decreasing the amount of energy saved by the adaptive method.…”

Power Reduction of Variable Wordlength OFDM Receiver in Time-Varying Fading Channels by Monitoring Subcarrier SNRs

“…Nisar presented the supply voltage control where the power reduction is performed for short wordlength as well as clock gating [9]. The auto rate fallback (ARF) method that gradually decreases/increases the wordlength according to successful/failed packet receptions has been evaluated in [6], [10].…”

“…Those communication systems request very low bit error rate (BER) and packet error rate (PER) as much as possible. The conventional variable wordlength methods [6]- [10] target certain BERs and PERs (e.g., 2×10 −4 in BER [7] and 10 −2 in PER [6]) and induce communication performance degradation when compared with a floating-point representation.…”