What Ultrasound Can and Cannot Do in Implantable Medical Device Communications

Jaafar, Banafsaj; Neasham, Jeffrey; Degenaar, Patrick

doi:10.1109/rbme.2021.3080087

Cited by 10 publications

(6 citation statements)

References 76 publications

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“…The system represented in Figure 1 is an illustrative description of the US-powered integrated circuit to be implanted in the human brain. It is worth noting that the same IC could be used for any specific biomedical application, such as heart-beat stimulations, gastrointestinal activities manipulation, and other kinds of controls and actuations applied to patients affected by chronic diseases [7][8][9][10]. The IMDs are powered-up, exploiting US-acoustic waves generated from external piezo-transducers (TX-PIEZO, in Figure 1) kept under the electrical resonance condition and placed in contact with the skin.…”

Section: Us-powered Imds: a System Overviewmentioning

confidence: 99%

“…In particular, the feature of collecting data and communicating them to the external world, namely Data Up-Link, has revealed a promising solution for bioelectronic medicine that exploits these devices [7]. Furthermore, the ability to act on neurons, nerves, the heart-beat, and gastrointestinal activities, made up through the manipulation of electrical transducers, could optimise therapeutic protocols and help relieve patients' pain [10]. These kinds of stimulations come from the modulation of a powering signal generated from an externally placed unit coupled to the implanted receivers for power/data exchanging.…”

Section: Starvedmentioning

confidence: 99%

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A 28 nm Bulk CMOS Fully Digital BPSK Demodulator for US-Powered IMDs Downlink Communications

2022

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Low-invasive and battery-less implantable medical devices (IMDs) have been increasingly emerging in recent years. The developed solutions in the literature often concentrate on the Bidirectional Data-Link for long-term monitoring devices. Indeed, their ability to collect data and communicate them to the external world, namely Data Up-Link, has revealed a promising solution for bioelectronic medicine. Furthermore, the capacity to control organs such as the brain, nerves, heart-beat and gastrointestinal activities, made up through the manipulation of electrical transducers, could optimise therapeutic protocols and help patients’ pain relief. These kinds of stimulations come from the modulation of a powering signal generated from an externally placed unit coupled to the implanted receivers for power/data exchanging. The established communication is also defined as a Data Down-Link. In this framework, a new solution of the Binary Phase-Shift Keying (BPSK) demodulator is presented in this paper in order to design a robust, low-area, and low-power Down-Link for ultrasound (US)-powered IMDs. The implemented system is fully digital and PLL-free, thus reducing area occupation and making it fully synthesizable. Post-layout simulation results are reported using a 28 nm Bulk CMOS technology provided by TSMC. Using a 2 MHz carrier input signal and an implant depth of 1 cm, the data rate is up to 1.33 Mbit/s with a 50% duty cycle, while the minimum average power consumption is cut-down to 3.3 μW in the typical corner.

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Section: Us-powered Imds: a System Overviewmentioning

confidence: 99%

Section: Starvedmentioning

confidence: 99%

A 28 nm Bulk CMOS Fully Digital BPSK Demodulator for US-Powered IMDs Downlink Communications

2022

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“…sending a reference burst to remove the interference [19], or subtracting the constant interference during continuous power delivery. The above techniques can only be used if the channel is static, but this is unfortunately not the case within the human body [13]. In contrast, for BFSK such bit errors can be avoided even in non-static channels, as only the amplitudes of the superimposed modulation pulses with frequencies f 0 and f 1 are compared to each other, while the changing offset due to the secondary scattering is ignored.…”

Section: Proposed Modulation Scheme and Implementation Considerationsmentioning

confidence: 99%

“…For power-aware or battery-less miniaturized implants, custom wireless electromagnetic or ultrasonic communication links are state-of-the-art. A comprehensive overview of existing methodologies for mm-sized networked implants can be found in [11], [12] and [13].…”

Section: Introductionmentioning

confidence: 99%

A Robust Backscatter Modulation Scheme for Uninterrupted Ultrasonic Powering and Back-Communication of Deep Implants

Holzapfel

Giagka

2022

Preprint

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Traditionally, active implants are powered by batteries, which, when discharged, have to be either replaced or recharged by an inductive power link. In the recent years, ultrasonic power links are also being investigated, as they promise more available power for deeply implanted miniaturized devices. Such devices often need to transfer information back, for example sensor data or some status information of the implant. For ultrasonically powered implants, this data transfer is usually achieved with On- Off Keying (OOK) based on load or backscatter modulation, or active driving of a secondary transducer. In this paper, we propose to superimpose OOK with subcarriers, effectively leveraging Frequency-Shift Keying, which increases the robustness of the link against interference from other nearby scatterers and fading, due to patient movements, for example. This approach also allows for simultaneous powering and communication, and inherently provides the possibility of frequency domain multiplexing to address individual nodes in implant networks. The proposed modulation scheme can be implemented in miniaturized application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and microcontrollers, with little additional complexity. We have validated this communication scheme in a water tank setup during continuous ultrasound powering. In these experiments we achieved symbol rates of up to 100 kBd (limited in this implementation by the selected microcontroller), were able to detect the modulated signal when placing the implant transducer about 4 cm away from the focal axis and showed that this modulation scheme is more robust than OOK. This approach could provide a more stable uplink communication, particularly for miniaturized implanted devices that are located deep inside the body and need continuous ultrasonic powering.

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“…IBC can be deployed using a number of different techniques, such as galvanic coupling, capacitive coupling, ultrasound, and resonant coupling [8]. Most of these IBC techniques suffer from low bandwidth and short transmission distances although ultrasound can reach tens of Mb/s over very short distances [9], and capacitive coupling up to 150 Mb/s [10] using custom CMOS transceiver circuit designs. However, for capacitive coupling, a path through external ground is needed, thus the modification of the surroundings becomes essential.…”

Section: Introductionmentioning

confidence: 99%

92 Mb/s Fat-Intrabody Communication (Fat-IBC) With Low-Cost WLAN Hardware

Rangaiah

Engstrand

Johansson

et al. 2024

IEEE Trans. Biomed. Eng.

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The human subcutaneous fat layer, skin and muscle together act as a waveguide for microwave transmissions and provide a low-loss communication medium for implantable and wearable body area networks (BAN).In this work, fat-intrabody communication (Fat-IBC) as a human body-centric wireless communication link is explored. To reach a target 64 Mb/s inbody communication, wireless LAN in the 2.4 GHz band was tested using lowcost Raspberry Pi single-board computers. The link was characterized using scattering parameters, bit error rate (BER) for different modulation schemes, and IEEE 802.11n wireless communication using inbody (implanted) and onbody (on the skin) antenna combinations. The human body was emulated by phantoms of different lengths. All measurements were done in a shielded chamber to isolate the phantoms from external interference and to suppress unwanted transmission paths.The BER measurements show that, except when using dual on-body antennas with longer phantoms, the Fat-IBC link is very linear and can handle modulations as complex as 512-QAM without any significant degradation of the BER.For all antenna combinations and phantoms lengths, link speeds of 92 Mb/s were achieved using 40 MHz bandwidth provided by the IEEE 802.11n standard in the 2.4 GHz band. This speed is most likely limited by the used radio circuits, not the Fat-IBC link.The results show that Fat-IBC, using low-cost off-theshelf hardware and established IEEE 802.11 wireless communication, can achieve high-speed data communication within the body. The obtained data rate is among the fastest measured with intrabody communication.

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What Ultrasound Can and Cannot Do in Implantable Medical Device Communications

Cited by 10 publications

References 76 publications

A 28 nm Bulk CMOS Fully Digital BPSK Demodulator for US-Powered IMDs Downlink Communications

A 28 nm Bulk CMOS Fully Digital BPSK Demodulator for US-Powered IMDs Downlink Communications

A Robust Backscatter Modulation Scheme for Uninterrupted Ultrasonic Powering and Back-Communication of Deep Implants

92 Mb/s Fat-Intrabody Communication (Fat-IBC) With Low-Cost WLAN Hardware

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