# Brain-Inspired Data Transmission in Dense Wireless Network
## 3 Ultra-Dense Wireless Networks and Their Biological Counterparts
### Fundamentals of Human Nervous System  
The human nervous system consists of nerve and glial cells. They form a very dense network of nerve connections that transmit information. This information reflects the  
Figure 1: Considered dense wireless network.  
data that control the entire human body: simple information about touch, complex data about the environment (vision and sound), muscle control, thinking, imagination, etc. The basic transmission of impulses takes place by means of neurons which, using both electrical and chemical machinery, pass the information on. Glial cells are generally designed to support the transmission that takes place between neurons. Despite the fact that neurons do not physically touch--there is a non-zero distance between them--this transmission is closer to wired transmission than wireless transmission. The neuron, after receiving enough neurotransmitters via dendrites, creates/excites an action potential in the cell body, and then, as an electrical signal, it is sent along the axon. At the end of the axon are synapses which, upon receiving a sufficiently strong electrical impulse from the axon, produce neurotransmitters. These, in turn, released from a given neuron, are designed to excite (in an analogous way) another neuron. Much of the impulse path is thus traveled in the form of an electrical impulse in the axon (which is analogous to wired data transmission). The information transmission mechanism itself, however, is very similar to wireless transmission between devices in a network, e.g., sensor or relay network. Despite being neurons, there are different types of glial cells:
* Astrocytes are the glial cells responsible for constituting the so-called blood-brain barrier (i.e., the barrier between the human nervous and blood systems) [9]. The astrocyte is able to detect the presence of some chemicals in the blood (such glucose) through dedicated receptors, and in consequence influence the transmission between neurons.
* Microglia are also highly important glial cells in HNS being the first and main form of human active immune defense in the central nervous system. In a nutshell, microglia clean the central part of HNS from unnecessary and damaged neurons or cells. Microglia cells may act in two states: observation of the surrounding and taking repairing action. It is worth emphasizing that microglia can communicate with other microglia cells, astrocytes or even nerves [9].
* Oligodendrocyte and Schwann cells are the glial cells responsible for the creation of the myelin sheath on axons, thus providing insulation for axons, and the process of creating a myelin sheath is called myelination. We can find oligodendrocytes in the central nervous system, and this cell wraps up to 50 axons with myelin. In turn, Schwann cells can be found in the peripheral nervous system, and they wrap only one axon with myelin. Myelination is an important part of human intelligence; it may be treated as a learning procedure or our nervous system development [9].  
There are other glial cells in the human body, but, in our research, we considered the application of two kinds of wireless nodes inspired directly by functionalities provided by astrocytes and microglia.