Use of a Variable Wordlength Technique in an OFDM Receiver to Reduce Energy Dissipation

Abstract

Wordlength determination is an indispensable task in digital hardware implementations of signal processing algorithms because the wordlength affects power consumption and system performance. There is a tradeoff between power consumption and system performance when searching for the optimum wordlength. We have developed a technique of dynamically controlling the wordlength used in the signal processing algorithms of wireless orthogonal frequency-division multiplexing (OFDM) receivers. The receiver dynamically changes the wordlength on the basis of the conditions in the propagation environment while satisfying the user-required communication quality. That is, the system optimizes the wordlength while operating by sensing its own performance and gradually adjusting this wordlength to improve performance. Testing revealed that, for a packet error rate (PER) of 10 2 , the application of this technique to an OFDM receiver reduces energy dissipation by 18.1%-30.2%.

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

“…However, a selector to choose the right implementation is described in our work. 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%).…”

“…These parameters are related with the link quality, which is evaluated using metrics like the BER, the Packet Error Rate (PER), and the Error Vector Magnitude (EVM). Indeed, these metrics are linked [5]. In our work, the BER is used for measuring the link quality.…”

“…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.…”

“…Indeed, a fixed-point implementation selector will decrease the announced energy savings. In [5], an adaptive wordlength OFDM receiver is developed without the need of an off-line simulation step. 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.…”

Dynamic wordlength calibration to reduce power dissipation in wireless OFDM systems

“…This technique system is an efficient approach for reducing power dissipation in wireless communication because a dynamic range in wireless systems is sensitive to multipath fading conditions. Variable wordlength has been applied into an OFDM demodulator [1], [2], an equalizer [3] and to a soft-decision Viterbi decoder [4] for reducing power dissipation in various wireless environments. However, their techniques have considered a single wordlength condition.…”