9.3.3 Multiple Access Techniques for Signal Transmission

Prosthetic devices contain a somatosensory system in which large sensor arrays are in­

tegrated into the electronic skin. The origin of the signal and information that it contains

are provided to the sensing systems.

9.3.3.1 Time-Divisional Access

The electronic skin sensor is structured in a crossbar of rows and columns. A 2D map is

formed periodically as the sensors are sampled with divisional multiple access. These

kinds of sensors measure the signals in a very short time. Time divisional multiple

acess (TDMA) transmissions are organized in a frame structure and are used for

measuring the performance of the device in electronic skin sensors. TDMA method is

suitable for small-scale sensors. However, this approach is limited for a large number of

the sensors; as the sensor increases, they are closer to the skin receptors and increases

overall sampling time. This increase in sampling time creates challenges to achieving

real-time feedback.

9.3.3.2 Event-Based Access

The central nervous system can receive multiple stimuli from different parts of the

body simultaneously. Several studies can demonstrate the concept of the nervous

system, including a data acquisition system for skin applications. The framework used

in these studies triggers the readout at a constant rate. The frame attains the data from a

sensor and collects this data instead of pixel by pixel. It provides the results of the real-

time sampling in a short time. However, it requires a large network of wires and high

power consumption. Another promising strategy is event-based signaling. It transmits

the signal when the output of the sensor changes, thus saving power and bandwidth.

The coded electronic skin system provides information on the transmission of real-time

tactile. A tiny microcontroller, present in the asynchronously coded electronic skin

system, is connected with a sensor that generates the signature signal for each sensor.

The signals transmitted by a single wire are decoded and recorded as temporal skin

patterns.

9.3.3.3 Biomimetic Synaptic Access

The central nervous system uses the synapses for addressing the stimuli. The potential of

the system is decided by bionic synapses based on distance recognition and spatial or­

ientation [32]. The distribution of multi-gates at different distances and directions is

adopted around the channel in the in-plane gate ion-gate transistor. The postsynaptic

current will be smaller as the distance between the gate and channel is increased.

Postsynaptic current from different directions is provided by different gates present in

that area. Gate position in transistors is decided based on the magnitude of the post­

synaptic current. Synaptic transistors provide the features of pattern in combination with

pressure sensors. A neuromorphic tactile processing system is made up of an ionic

conductor, ion-gated transistor, and piezoelectric sensor. The sensor is attached to the

fingertip; motion of the finger on different patterns of groups produces waveforms of the

different currents. These patterns are identified by machine learning tools and informa­

tion is indirectly used to measure tactile functions.

Bioinspired Prosthetic Interfaces

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