Bit-loaded PAPR reduction for high-data-rate through-metal control network applications

Data transmission through metallic structures is commonly required in industrial control applications. In a number of these applications, mechanically penetrating the structure to pass cables and establish a wired communication link is either impossible or undesirable. Examples of such structures include metal bulkheads, pressure vessels, or pipelines. Ultrasonic signaling has been proposed as a solution for through-metal data transfer without penetrating the structure. The reverberant nature of the through-metal channel, however, can lead to significant intersymbol interference, limiting the data rate achievable by conventional single-carrier communication techniques. In this paper, we describe a through-metal communication technique that exploits the slow-varying nature of the ultrasonic channel to implement an orthogonal-frequency-division- multiplexing-based rate-adaptive peak-to-average power ratio (PAPR) reduction algorithm. Measurements of the proposed adaptive algorithm have demonstrated transmitted throughput rates of up to 14 Mbps while reducing PAPR by up to 3 dB and maintaining a bit error rate of 10^-5 at average transmit powers of roughly 6 dBm. This enhancement provides the required throughput and error rate to support high-rate network applications in otherwise data-limited environments.