Ultrasonic multiplexing network for implantable medical devices

• US 10,396,948 B2
• Filed: 06/14/2017
• Issued: 08/27/2019
• Est. Priority Date: 01/07/2015
• Status: Active Grant

• Current Assignee: Northeastern University
• Original Assignee: Northeastern University
• Inventors: Melodia, Tommaso, Santagati, Giuseppe Enrico
• Primary Examiner(s): Tayong, Helene E
• Application Number:
  US15/622,492
• Publication Number:
  US 20170279571A1
• Time in Patent Office: 804 Days
• Field of Search: 375260
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: H04B 13/005 Transmission systems in which the medium consists of the human body
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2053 using more than one carrier, e.g. carriers with different phases
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/362 Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence
• CPC Class Codes: H04L 5/0012 Hopping in multicarrier systems for frequency hopping in spread spectrum systems H04B1/713

Abstract

A system and method for transmitting data ultrasonically through biological tissue employs a network of a plurality of nodes, at least a portion of the nodes implantable within the biological tissue. At least one implanted node includes a transmitter having an orthogonal frequency division multiplex signal generator to encode an ultrasonic signal for transmission through the biological tissue to an ultrasonic receiver at another node.

Claims

1. A system for transmitting data ultrasonically through biological tissue comprising:

a network comprising a plurality of nodes, at least a portion of the nodes implantable within a body;

a first node implantable in the body and comprising an ultrasonic transducer and a transmitter, and a second node comprising an ultrasonic receiver;

the transmitter at the first node including an orthogonal frequency division multiplexing (OFDM) signal generator operative to encode an input information bit stream on orthogonal subcarriers for transmission as an ultrasonic signal through the body to the ultrasonic receiver at the second node, wherein OFDM packets carrying information bits are preceded by a preamble to provide a starting point of a packet to perform time synchronization; and

the ultrasonic receiver at the second node operative to decode the ultrasonic signal received from the first node to recover the information bit stream.

2. The system of claim 1, wherein the OFDM signal generator is operative to generate a baseband modulated signal as a sum over a number of subcarriers of the symbols to be transmitted as a function of a frequency spacing between the subcarriers for a time block of a given duration.

3. The system of claim 2, further comprising introducing a guard time between time blocks, wherein the guard time comprises silence or a repetition of the time block.

4. The system of claim 2, further comprising a symbol mapper to map the bit stream into a constellation of a modulation scheme.

5. The system of claim 4, wherein the modulation scheme comprises M-phase-shift-keying or M-quadrature-amplitude-modulation.

6. The system of claim 1, wherein the OFDM signal generator comprises:

a serial to parallel convertor to convert the input information bit stream into a plurality of parallel data strings,

an inverse Fourier transformer to generate a frequency domain representation of the input information bit stream,

a parallel to serial converter for converting the frequency domain representation into a serial stream, and

an up-converter to convert the signal to a carrier frequency for transmission through the biological tissue.

7. The system of claim 1, wherein the receiver comprises:

a down-converter to convert the received signal to a baseband signal,

a serial to parallel converter to convert the baseband signal into a plurality of parallel data strings,

a Fourier transformer; and

a parallel to serial converter to convert the parallel data strings into a serial data string.

8. The system of claim 1, wherein the OFDM signal generator is operative to send symbols on a set of occupied subcarriers comprising a subset of available subcarriers, wherein the occupied subcarriers are fixed or selected randomly and change in consecutive blocks within a frame.

9. The system of claim 8, wherein the occupied subcarriers are selected by a pseudo-random frequency-hopping sequence generated by seeding a random number generator with an identification unique to the transmitter.

10. The system of claim 1, wherein the OFDM signal generator is operative to send symbols in blocks at fixed or randomly selected time chips within a time frame.

11. The system of claim 1, wherein the OFDM signal generator is operative to provide forward error correction.

12. The system of claim 1, wherein the OFDM signal generator is operative to provide one or more modulation techniques at a subcarrier level, a block level, or a frame level.

13. The system of claim 12, wherein the modulation technique is selected to optimize a data rate as a function of one or more of a number of occupied subcarriers, a number of time chips per time frame, an error correction coding rate, and a modulation rate.

14. The system of claim 1, wherein the receiver is operative to detect an incoming frame from the transmitter and to identify the starting point of a packet, wherein identifying the starting point comprises correlating the received ultrasonic signal with a local copy of a preamble preceding each OFDM frame.

15. The system of claim 1, wherein the receiver is operative to determine one or more of a signal to interference-plus-noise ratio as a function of instantaneous power, time-hopping frame length, and number of occupied subcarriers.

16. The system of claim 1, wherein the receiver is operative to maximize a transmission rate between the transmitter and the receiver by selecting one or more of an instantaneous power, a number of occupied subcarriers, a time-hopping frame length, a forward error correction coding rate and a modulation rate based on a level of interference and channel quality measured at the receiver and on a level of interference generated by the receiver in communications to other nodes.

17. The system of claim 1, wherein the receiver is operative to determine one or more of an instantaneous power value, a number of occupied subcarriers, a time-hopping frame length, a forward error correction coding rate and a modulation rate that maximizes a data rate.

18. The system of claim 17, wherein the receiver is further operative to maximize the data rate subject to a signal to interference-plus-noise ratio per node being above a minimum value and a data rate per node being above a minimum value.

19. The system of claim 1, wherein the receiver is further operative to determine an energy rate, the energy rate comprising an energy per bit or an average power radiated per second.

20. The system of claim 19, wherein the receiver is further operative to minimize the energy rate subject to a signal to interference-plus-noise ratio per node being above a minimum value and a data rate per node being above a minimum value.

21. The system of claim 1, wherein the transmitter is operative to open communication to a receiver on a common control channel using a two-way hand-shake procedure, and, after receiving a clear-to-transmit signal from the receiver, to transmit on a dedicated channel to the receiver a frequency-hopping sequence and a time-hopping sequence, and the receiver is operative to transmit to the transmitter an optimal transmission strategy.

22. The system of claim 1, wherein the first implantable node further comprises one or both of a sensor operative to sense one or more biological parameters or an actuator.

23. The system of claim 1, wherein the first node and the second node are operable at a data rate of at least 28 Mbit/s.

24. A method for transmitting data ultrasonically through biological tissue comprising:

in a network comprising a plurality of nodes, at least a portion of the nodes implanted within a body, including a first node implanted in the body and comprising an ultrasonic transducer and a transmitter, and a second node comprising an ultrasonic receiver;

at the first node, encoding an information bit stream on orthogonal subcarriers using an orthogonal frequency division multiplexing (OFDM) modulation scheme, wherein OFDM packets carrying information bits are preceded by a preamble to provide a starting point of a packet to perform time synchronization;

transmitting the encoded signal through biological tissue; and

at the second node, receiving the encoded signal and decoding the signal to recover the information bit stream.

25. The method of claim 24, wherein the first node and the second node are operable at a data rate of at least 28 Mbit/s.