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With the continuous increase of the number of Internet of things devices, the communication or connection between these devices has become an important thinking topic. According to Gartner's research, the number of IOT devices will reach 20.4 billion by 2020. There are several available Internet of things communication protocols, which have different performance, data rate, coverage, power and memory, and each protocol has its own advantages and more or less disadvantages. Some of these communication protocols are only suitable for small household appliances, while others can be used for large smart city projects.

Common Internet of things communication protocols

As the Internet of things has become a hot topic for IT professionals, we will briefly introduce the most commonly used communication protocols in Internet of things devices.

1、 Bluetooth low power (ble)

Bluetooth low power consumption (ble) is an enhanced version of Bluetooth. It is also one of the earliest and most widely used wireless technologies. It can communicate effectively in a short distance of about 10 meters. The concept of Bluetooth was proposed by Nils Rydbeck of Ericsson in 1989. Between 2001 and 2004, it was further optimized for lower power consumption and lower cost versions, such as Bluetooth low power (ble) protocol or Nokia's intelligent Bluetooth. It aims to maintain communication range while significantly reducing energy consumption. Because of this attribute, Bluetooth has become the main protocol of Internet of things devices. At present, it is used in all mainstream operating systems, including IOS, Android, Microsoft mobile phone, strawberry, OS X, Linux and windows. The latest version of Bluetooth technology is 5.0, which adds an innovative network protocol support profile (IPSP). At present, it has carried out comprehensive development and Optimization for Internet of things devices.

2、 WiFi

WiFi is another protocol widely used for communication between Internet of things devices. Nowadays, WiFi has become an indispensable part of our life, because it uses a large number of infrastructure, can transmit data quickly (up to hundreds of megabytes per second), and has the ability to handle a large amount of data transmission. For many designers of electronic devices, WiFi is the best choice because of its infrastructure. The communication distance between two devices using WiFi is about 50 meters, which is much higher than that using Bluetooth technology.

WiFi is based on IEEE 802.11 series standards, and its first version was released in 1997. This version can provide link speed up to 2Mbit / s. At present, the most commonly used standard for WiFi is 802.11n based on IEEE 802.11, but the use of 802.11ac is also growing rapidly. The latest version provides faster communication speed than 802.11n. (from IOT home network) although WiFi is very suitable for communication between IOT devices, its operation energy consumption is relatively high. However, in any case, it is the most powerful protocol for file transfer between most Internet of things devices.

3、 ZigBee

ZigBee is a short-range wireless communication protocol based on IEEE 802.15.4 standard. Its working frequency is 2.4GHz and the data rate is 250kbps. ZigBee is suitable for effective communication between IOT devices because it has the properties of low energy consumption, high scalability, security, persistence and high node points. Not only can the maximum number of nodes reach 1024 and the maximum distance reach 200m, but ZigBee can even use 128 bit AES encryption algorithm.

ZigBee specification (IEEE 802.15.4-2003) was first approved on December 14, 2004 and released in 2005. The ideal design of ZigBee protocol is for home automation and large industrial sites, because these places require low power consumption, and the data exchange between homes or buildings is not frequent at low data rate. ZigBee has a large user base as the preferred mode of communication between IOT devices.

The latest version of ZigBee is ZigBee 3.0, which can be considered as a collection of all functions of several ZigBee wireless standards. Electronic systems that require low energy consumption, such as street lighting and electricity meters in urban areas, use ZigBee protocol as the preferred mode of communication between Internet of things devices. ZigBee protocol can also be used in security systems and smart homes.

4、 Z-Wave

Similar to ZigBee, Z-Wave is a low-power RF communication protocol, which is mainly used in home automation systems and electronic devices, such as lamp controllers and sensors. The frequency of Z-Wave communication protocol is 900MHz and the range is 30-100m. Therefore, the interference between the protocol and other wireless protocols (such as WiFi, Bluetooth, ZigBee with operating frequency of 2.4GHz, etc.) can be ignored. Its data rate ranges from about 40kbps to 100kbps.

Compared with other protocols, Z-Wave protocol is simpler, so it can be easily developed at a faster speed. The radio frequency band used in Z-Wave is the specific frequency band of the host country. For example, 868.42 MHz SRD band (Europe), 900 MHz ism or 908.42 MHz band (USA), 916 MHz band (Israel), 919.82 MHz band (Hong Kong), 921.42 MHz band (Australia / New Zealand), 865.2 MHz band (India).

5、 Remote wide area network (lorawan)

Long range wide area network (lorawan) is a communication protocol, which is mainly used for regional, national or global battery powered remote wireless Internet of things devices. It is known for its ability to communicate over long distances with the lowest power consumption and to detect signals at noise levels. (source: IOT home network) this protocol is mainly used in smart cities, where large networks have millions of connected devices that operate on smaller batteries and memory. The data rate of lorawan is 0.3kbps to 50kbps.

Intelligent street lighting is a practical example of using lorawan protocol, in which street lamps are connected to Lora gateway using lorawan protocol. The gateway is then connected to the cloud application, which fully controls the brightness of the light bulb and adjusts it according to the natural light in the environment.

6、 Near field communication (NFC)

Near field communication (NFC) is a simple and secure protocol, which can simplify the two-way communication between Internet of things devices. It mainly uses the near-field electromagnetic induction of two ring antennas. It is designed for smart phones and allows users to conduct contactless payment transactions. It also helps users access electronic content and connect electronic devices. Basically, it expands the function of contactless card technology, so that Internet of things devices can share information in a short distance of less than 4 cm.

The data rate of NFC protocol is 106kbps to 424kbps. Because NFC protocol is a short-range communication protocol, the power consumption is lower. It takes less setup time and does not require device pairing. Also due to short-distance communication, the possibility of harmful interference to other networks in the environment is greatly reduced.

Internet of things communication protocol: "the best choice" vs. "the most suitable choice"

Today, the most widely used Internet of things communication protocols are Bluetooth and WiFi, but NFC is developing rapidly. It is difficult to determine which of the communication protocols discussed above is most suitable for IOT devices, but the winner must be the one that can be easily used and at the appropriate rate on most newly manufactured IOT devices and mobile phones. However, based on the current variety of use cases, the key to the problem is not to find the "best" choice, but to find the "most suitable" choice according to the requirements. For example, if you need to transfer a large amount of data and files over the network, WiFi will be the ideal choice, and if you want to use contactless card technology for instant payment, NFC will be the first choice. In short, a successful communication protocol depends entirely on what you want to achieve.