Transmission and medium access control techniques for ultrasonic communications in the body

A method for transmitting data through biological tissue using ultrasonic pulses comprising:

• setting, at a transmitter, an initial time-hopping frame length and an initial spreading code length for data transmission;
• sending, from the transmitter, a request-to-transmit packet to a receiver over a control channel at the initial time-hopping frame length and the initial spreading code length;
• receiving, at the transmitter, a clear-to-transmit packet from the receiver over the control channel, the clear-to-transmit packet comprising feedback information;
• calculating a private time-hopping sequence and private spreading code based on a pseudo-random sequence generator and an ID of the transmitter;
• establishing a connection with the receiver using the private time-hopping sequence and private spreading code;
• setting, at the transmitter, a forward time-hopping frame length and a forward spreading code length based on the feedback data in the clear-to-transmit packet;
• sending, from the transmitter, a data packet using the private time-hopping sequence, private spreading code, forward time-hopping frame length, and forward spreading code length;
• receiving, at the transmitter, an acknowledgement packet having updated feedback data;
• and
• setting, at the transmitter, the forward time-hopping frame length and the forward spreading code length based on the updated feedback information.