# A Node Density Control Learning Method for the Internet of Things
## 3 Characteristics of Wireless Sensor Networks  
The sensory factors used by WSNs to sense the real world under IoT are composed of a large number of low-cost nodes with a certain organizational structure [9]. It collects, processes, communicates and identifies environmental sensing variables through inter-working. To improve the effect of density control of mobile wireless sensor node, one needs to first analyze the characteristics of the WSN, with its unique characteristics of WSN node structure is analyzed, which uses the geometric model for road use attenuation node density and node connection probability and so on, in order to realize the control of node density. Specific characteristics of WSNs include:  
* autonomous networking
* large-scale applications
* short-range communication
* multi-hop routing
* node free distribution
* multi-point sensing of data
* network adaptive topology
* low power consumption
* low cost
* limited communication and processing capabilities
* diversified application scenarios
* self-healing compensation
* remote monitoring and control  
The line sensor network is a peer-to-peer autonomous network with strong applicable background. The network structure and communication protocol have great differences according to different application scenarios. The node topology control process changes according to specific needs. WSNs used in IoT environments have some common features due to their many limitations. 1. Limited hardware resources  
WSNs generally require low cost and low power consumption of nodes. Therefore, no matter the distance and bandwidth of communication, the collection, and processing of information, or the security and reliability of data, the hardware resources of nodes are quite limited. Making the most of limited resources based on specific applications is a priority for every wireless sensor design. In particular, for a large number of multi-node applications, the resource allocation of nodes not only causes a huge difference in cost but also has a significant impact on the communication quality of the entire network. Limited resource allocation needs to integrate the influence of various aspects of the whole network, including network topology, data collection rate, routing communication protocol, data security assurance mechanism to fully analyze the optimal allocation scheme of nodes. 2. Adaptive network topology In the application of WSNs, each node in a large number of nodes may have position changes, node damage, online networking failure, communication link quality deterioration, and error data packet delivery. When the topology of a wireless communication network has a small range or a very low probability of a large-scale change, the reliability of communication can be greatly affected. The WSN itself should have the ability to adapt or reorganize the network, restore the network topology and multi-hop mechanism within a certain period of time, and ensure that the network jumps back to a normal working state. The adaptive capability of the WSNs has high requirements on the data link layer protocol, the medium access layer protocol and the routing protocol used by the network, and the networking function of the network is completed with a low network overhead. 3. Multi-hop routing protocol The information collected by the network node needs to be transmitted through the relay of the surrounding nodes and selectively transmitted to the aggregation node in multiple ways so that the data can complete the final summary, display, and networking. The routing protocol between nodes determines the communication quality and service life of the network. Different network applications use different routing protocols and the multi-hop routing mechanism is also very different. However, finally, the data of the collection node needs to be transmitted to the aggregation node through the multi-hop route. 4. Self-awareness and ability to repair The nodes of WSNs are composed in various forms, the distribution is freely dispersed, and the life and use of nodes can be different.