Wireless sensor network is a new information acquisition and processing technology, which combines the logical information world with the objective physical world. Wireless sensor networks show broad application prospects in more and more fields.
Cloud computing is a flexible way to organize and provide IT resources. Supports distributed storage and parallel processing, and its data processing framework handles most of the data in a local computing manner without the need for large amounts of remote transmission of the data.
Cloud Sensor
The cloud sensor integrates measurement awareness, network transmission, and cloud components. It is characterized by the integration of sensing components and networking components. The data collected by the sensors is directly uploaded to the cloud platform. Users can directly use data from the cloud platform to save the cost of intermediate transmission processing circuits.
Advantage 1: It is easy to use. After power on, the user can directly read the data measured by the sensor through the computer or mobile phone;
Advantage 2: cloud computing, cloud sensor real-time networking, cloud platform can use real-time sensor data for big data processing, big data processing results can also be fed back to the cloud sensor. The most direct application is to implement on-line dynamic calibration of sensors and use big data to eliminate local measurement errors;
Advantage three: to facilitate rapid secondary development of customers, eliminating the need for complex cloud construction and cost savings.
Cloud computing-based wireless sensor network
1, the architecture
The cloud-based wireless sensor network architecture is shown in the figure. A group of special nodes are distributed in the Wireless Sensor Network (WSN) area called cloud nodes. Cloud nodes have more resources than sensors and have two functions. On the one hand, these nodes make up a cloud, which is part of the cloud; on the other hand, they can also communicate with sensors and collect data from accessory sensors, also known as point sinks. Sensors send sensed data to a convergence point (in multi-hop mode), and the aggregation point stores the data in the cloud. The sensors that send the data to the same convergence contact form a group. In order to distinguish from the concept of clusters in the WSN, this group is a zone. For the sensor, the entire cloud appears as a virtual sink.
2, partition sensor organization
Sensors belong to one partition according to some rules. For example, a sensor can be added to the partition represented by the closest convergence contact. Sensors in each partition can be of the same type or different types, which form a local wireless sensor network and are independent of other partitions. All local wireless sensor networks are connected in a cloud. Sensors in the partition can be organized in a planar or hierarchical structure.
In the multi-layer WMSN structure, the same kind of sensor is organized in the same layer to form a WSN; the lower layer WSN is connected to the upper layer through the central node, and the upper layer is transferred to the lower layer by the central node. At the same time, the high-level central node can also process the forwarded data so as to schedule the activity of the sensor at the layer, such as hibernation or activation. This mode of operation reduces sensor energy consumption compared to when the sensor is always in an active state. But on the other hand, the design and maintenance of sensor software have become more complicated. In addition, the central node will process and forward large amounts of data and its energy consumption will be faster.
On the cloud-based architecture, another way of organizing partition sensors is shown in the figure. The same type of sensors each form a WSN and send their data to the convergence contact (if the same type of sensor cannot communicate directly, it can also use a different type of sensor as a gateway). Each type of sensor forms a logically independent WSN with overlapping physical areas. These WSNs are connected to the same collection contact. Data processing software is deployed in the cloud (not just the collection contacts that these WSNs are connected to). After collecting various types of awareness data and processing it, the cloud can schedule sensors in each individual WSN (via convergent contacts) to operate in a reasonable manner. Compared with the cluster-based single-layer structure, this type of organization is implemented in partitions. The size of the independent WSN is smaller, the transmission efficiency is higher, and the control information still has the perspective of the entire network.
3, cloud organization
Cloud nodes need to consider the following questions when they form a cloud: a) How cloud nodes are deployed in the WSN area; b) How cloud nodes communicate with each other; c) How nodes are organized into clouds; d) How data collected by convergence contacts is stored to the cloud In the cloud.
The location of the cloud node (convergence contact) depends on the distribution of sensors in the wireless sensor network. Ideally, convergent contact locations can minimize data transfer operations throughout the network and can use complex algorithms for location selection. However, due to the dynamic nature of the WSN (topological changes, routing changes, data generation locations and patterns, etc.), the ideal goal is difficult to achieve. In the case of a uniform sensor distribution, a simple method is to have each convergence contact responsible for data collection of a substantially equal number of sensors.
Cloud nodes must communicate with each other to form a cloud. The cloud nodes need to be properly deployed in the WSN area and work in a manageable environment, so there may be network infrastructure. If there is a wired network, nodes can use VPNs for secure communication; if there is a mobile communication network (such as 2.5G, 3G, LTE, etc.), cloud nodes can use these networks for interconnection. However, wireless sensor networks are often deployed in infrastructure-free environments. Self-organizing wireless networks are the only available means of communication. For example, you can configure IEEE 802 for cloud nodes. 11 Protocol stacks that form Ad hoc networks.
Sensor data upload cloud
The wireless standard has undergone earth-shaking changes. Sensors can synchronize large amounts of data to the cloud and can be accessed at any time when needed. People realize the benefits that the Internet of Things may bring. We will see a variety of solutions, but in the end it will be more useful and cost-effective products.
With wireless connectivity, we can access cloud space on multiple devices. Here are several ways to synchronize sensor data to the cloud.
1, through the network cable connection
This is the simplest way. It was born in the 1970s and 1980s and is also the originator of all wireless connections. A microprocessor is installed in the sensor to process the collected data and then upload it over the wired network. In addition, the processor can also modify or update some of the sensor's functions. However, this approach is more restrictive because it is not possible to have network cables everywhere.
2, through the mobile phone network connection
The mobile phone network followed the birth of the wired network, and has made initial development in the early 1980s. The network also became the first wireless network to be widely used. However, its slot is also quite a bit. First of all, if you want to connect mobile base stations, the sensor still has to be connected to the phone via a network cable or a special baseband (high cost) in the phone; secondly, the upstream wireless transmitter needs a lot of power. Support; Finally, traffic fees can be very painful.
3, through a remote wireless network connection
As early as 1947, the regulatory authorities had opened up many unlicensed wireless bands, but in those days, this stuff was unattended. Until the mobile phone appeared in the 1990s, people really realized their value. In 2003, the two frequency bands 902-928 MHz and 2400-2483 MHz became new favorites for the latest IEEE 802.15.4 wireless standard.
These frequency bands are also used by mesh networks mentioned above. The network consists of many small, low-power wireless devices that are highly connected to each other and collect sensor data from the edge areas to a collection point. The rendezvous points are all connected to the cloud. This ensures the coverage of the wireless network.
4, through the wireless router connection
The 802.11 Wi-Fi standard that we are familiar with was born in 1997, this standard uses 2400-2483 MHz and 5130-5835 MHz frequency band. These two frequency bands have a profound impact on the ordinary people's wireless life. Such routers are found everywhere at home, in companies, or in public places.
In addition, some routers are more professional. They are mainly used in the industrial and infrastructure fields. Just plug in the Internet cable, the router can connect to the cloud, in fact, in the life of the wireless router is the most important channel for people to enjoy the cloud service.
With the advent of Wi-Fi capabilities on smartphones, sensors that can connect directly to routers have also been born. This means that as long as the signal coverage of the router is within the range, the sensor can be connected to the Internet at any time, eliminating the complicated process of connecting mobile base stations.
5, connected via cell phone
In real life, there are many times when the sensor does not need to connect to a wireless router, and the phone can handle everything. In this way, users can interact directly with the sensors and obtain the information they need. In addition, in many application scenarios, there is no need to transfer data across the oceans. One example is the wireless headset.
These data transmissions can be done by Bluetooth, which is the same as Wi-Fi and operates in the 2400-2483 MHz band. The standard was born in 1998 and it became part of the 802.15.4 standard in 2003, but it continues to show its light and heat.
Recently, technicians have come up with a new low-power Bluetooth (BLE) technology, which consumes low power and is suitable for simple sensors with lower speed or lower duty cycle. This technology provides a powerful impetus for the development of small sensors. Those sensors (such as smart bracelets) that originally required a wireless network or mobile phone network can now directly interact with mobile phones.
Recently, technicians also added Bluetooth capabilities to traditional Wi-Fi routers. In this way, sensors equipped with BLE technology can be directly connected to the cloud through routers, eliminating the need to connect mobile phones.
With the constant growth of various wireless standards, we can use more ways to promote the development of the Internet of Things.
With the development of the Internet of Things, the integration of cloud computing technology in sensor networks will enable the data processing technology of sensors to keep up with the same level. The information obtained will be greatly increased, and further integration of multiple functions will result in convergence. This is an inevitable trend of development. The development of sensor technology will be promoted from the side.
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