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Ultrasound waves pose a promising alternative to the commonly used electromagnetic waves for intra-body communication. This due to the lower ultrasound wave attenuation, the reduced health risks and the reduced external interference. Current state-of-the-art ultrasound designs, however, are limited in their practical in-body deployment and reliability. This stems from their use of bulky, focused transducers, the use of simple modulation schemes or the absence of a realistic test environment and corresponding realistic channel models. Therefore, this work proposes a new, ultrasound, static emulation test bed consisting of small, omnidirectional transducers and custom gelatin phantoms with additional scattering materials. Using this test bed, we investigate different in-body communication scenarios. Multiple communication channels were extracted and mapped onto FIR channel models, which are verified and open sourced for future research. Furthermore, a basic QAM modem was built to assess the communication performance under various modulation schemes. A link was established using 4-QAM and 200kbit/s resulting in a BER <1e-4 at received Eb/No of 13dB. Identical results were obtained by computer simulations on the FIR channels, which makes the extracted FIR channels suitable for the design of future ultrasound in-body communication schemes.

No abstract

Access to the full text of the published version may require a subscription. Abstract-There are several well-developed technologies of wireless communication such as radio frequency (RF) and infrared (IR), but ultrasonic methods can be a good alternative in some situations. A multi-channel airborne ultrasonic data communication system is described in this paper. On-Off Keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system by using a pair of commercially available capacitive ultrasonic transducers in a relatively low multi-path indoor laboratory environment. Six channels were used from 50 kHz to 110 kHz with a channel spacing of 12 kHz, allowing multiple 8-bit data packets to be transmitted simultaneously. The system data transfer rate achieved was up to 60 kb/s, and ultrasonic wireless synchronization was implemented, instead of using a hard-wired link. A model developed in the work could accurately predict ultrasonic signals through the air channels. Signal root mean square (RMS) values and system bit error rates (BER) were analysed over different distances. Error-free decoding was achieved over ranges up to 5 m using a multi-channel OOK modulation scheme. To obtain the highest data transfer rate and the longest error-free transmission distance, a range-dependent multi-channel scheme with variable data rates, channel frequencies and different modulation schemes, was also studied in the work. Within 2 m, error-free transmission was achieved using 5-channel OOK with a data rate of 63 kb/s. Between 2 and 5 m, 6-channel OOK with 60 kb/s data transfer rate was error-free. Beyond 5 m, the error-free transmission range could be extended up to 10 m using 3-channel BPSK with a reduced data rate of 30 kb/s. The situation when two transducers were misaligned using 3-channel OOK and BPSK schemes was also investigated in the work. It was concluded that error-free transmission could still be achieved with a lateral displacement of less than 7% and oblique angles of less than 7 Rights• , and 3-channel BPSK proved to be more robust than 3-channel OOK with transducer misalignment.