Abstract: A link adaptive orthogonal frequency-division multiplexed (OFDM) ultrasonic physical layer is provided that is capable of high data rate communication through metallic structures. The use of an adaptive OFDM subcarrier-based modulation technique mitigates the effects of severe frequency selective fading of the through-metal communication link and improves spectral efficiency by exploiting the slow-varying nature of the channel. To address the potential ill effects of peak-to-average power ratio (PAPR) and to make more efficient use of the power amplifiers in the system, the invention modifies and implements a symbol rotation and inversion-based PAPR reduction algorithm in the adaptive OFDM framework. This joint adaptive physical layer is capable of increasing data rates by roughly 220% in comparison to conventional narrowband techniques at average transmit powers of roughly 7 mW while constrained to a desired BER.

Abstract: The problems of high peak to average power ratio (PAPR) in multi-carrier systems and throughput improvement in multi-carrier systems by PAPR-aware rate adaptive bit loading are addressed by implementing two symbol rotation-inversion algorithms that reduce the peak to average power ratio in multi carrier OFDM systems jointly with rate adaptation. The method combines the benefits of bit allocation and symbol rotation to reduce the PAPR in OFDM communication systems and thus improve system range and robustness to noise. When coupled with adaptive bit loading techniques, these PAPR remediation strategies can substantially increase link throughput. Symbol rotation results in more than one order of magnitude BER reduction for SISO OFDM and one order of magnitude reduction in MIMO OFDM.

Abstract: A link adaptive orthogonal frequency-division multiplexed (OFDM) ultrasonic physical layer is provided that is capable of high data rate communication through metallic structures. The use of an adaptive OFDM subcarrier-based modulation technique mitigates the effects of severe frequency selective fading of the through-metal communication link and improves spectral efficiency by exploiting the slow-varying nature of the channel. To address the potential ill effects of peak-to-average power ratio (PAPR) and to make more efficient use of the power amplifiers in the system, the invention modifies and implements a symbol rotation and inversion-based PAPR reduction algorithm in the adaptive OFDM framework. This joint adaptive physical layer is capable of increasing data rates by roughly 220% in comparison to conventional narrowband techniques at average transmit powers of roughly 7 mW while constrained to a desired BER.