In the current world of connected “things”, there are a number of wired and wireless access technologies available or in development. Before reviewing these interfacing technologies, it is important to discuss the usage and corresponding standards for various use cases.
Wireless communication is currently very popular in the world of interconnected smart objects, the main purpose of which is to simplify the deployment of IoT devices and at the same time allow smart objects to move and change locations without losing connectivity. This article discusses this and also mentions the considerations for wired connections when using them.
coverage
The easiest way to solve the problems of how far the signal needs to travel, how wide the coverage is, and the difference between indoor deployment and outdoor deployment is to classify the technologies by usage, as shown in the figure below, and delimit these areas.
This article only discusses the widely used and relatively mature technologies on the market.
1. Short distance: a typical limited serial cable.
Wireless short-range communication technology is often considered a replacement for serial computers, and the communication between two devices can be up to 10 meters. Short-range wireless technologies include IEEE802.15.1 Bluetooth and IEEE 802.15.7 visible light communication. These short-range communication methods are only suitable for installation and deployment in a small space. In certain cases, they are not yet mature enough to be used for production-targeted deployments.
2. Mid-range: This range is the main category in the Internet of Things access technology.
In the range of tens of meters or even hundreds of meters, there have been many case specifications and implementation methods. The maximum distance between two devices is generally less than one kilometer, but as long as radio signals are transmitted and received within certain rules and ranges, RF technology theoretically has no limit to the maximum distance in the practical sense. Technologies used in medium-range wireless include IEEE 802.11 Wi-Fi, IEEE 802.15.4, and 802.15.4g WPAN. According to the physical medium characteristics, wired technologies such as IEEE 802.3 Ethernet and IEEE 1901.2 narrowband power communication (PLC) can also be classified as medium-range technologies.
3. Remote: Remote refers to the means of communication used when the communication between two devices exceeds 1 km.
Common examples of wireless are cellular data (2G, 3G, 4G, 5G) and some wide area (LPWA) technology applications used outdoors. LPWA communication technology can realize large-area wide-area communication without consuming a large amount of power energy. Therefore, equipped with batteries on devices using these technologies is currently the most ideal long-distance transmission solution.
For wireless deployment, the maximum coverage of the device is expressed in the form of specifications or product descriptions, and is usually obtained from the optimal limit of transmission conditions. In the actual environment, the planner should consider all the scenarios currently covered by the equipment, and then combine the site survey to understand the actual situation and obtain the planning scenarios and corresponding products. For example, signal transmission problems may occur in newly built buildings , at this time, it should be considered to use medium-range transmission with relatively strong anti-interference for communication between IoT devices.
frequency band
Many countries and organizations around the world have put forward requirements for the regulation and transmission of radio frequency bands. For example, in telecommunications where part of the frequency band is allocated to various categories and industries, such as in radio, television, military.
Frequency bands for various communication purposes are generally regarded as a key resource. Realize and understand the value of these frequencies by examining the costs paid for cellular band licenses by major operators, for example.
energy consumption
At present, the definition of IoT devices is very broad, but there is a clear boundary division in terms of power supply methods and nodes. Power supply nodes are generally directly connected to the power supply, and communication is currently not limited by power consumption standards. However, the availability of power sources limits the deployment of devices and improves deployability, making power sources a huge challenge.
The problem that the Internet of Things wireless access technology needs to solve is the efficient use of energy. The more efficient the equipment can use energy, the better it can gain an advantage in the market competition. This has also led to an evolution in the field of wireless devices – Low Power Wide Area Networks (LPWA). Obviously, energy utilization and consumption has become a new development track.
Topology
At present, there are three main topological schemes that occupy a dominant position: star, mesh, and point-to-point. A star topology is popular for long-range and short-range communications.
At present, it is a difficult task to classify IoT nodes, but with the continuous development of computers, device memory, and power schemes, RFC 7228 provides a definition standard for some restricted nodes. These definitions help distinguish between the restricted and unrestricted states of a node. Such as servers, desktop computers, smartphones, etc.