The basic architecture of the Internet of Things includes three layers: perception layer, network layer and application layer.
IoT Architecture Diagram
The perception layer collects some data (sound, light, electricity, etc.) through sensors, and the terminal module based on the network layer is connected to the base station of the network layer to realize the transmission after data collection.
The network layer is responsible for backhauling the data collected by the perception layer. It is very important to use different communication protocol technologies for backhauling based on different characteristics, which is also the focus of this article.
The application layer can be understood as the data platform and business platform of the Internet of Things. As the collection point of all IoT terminal data, the data platform is responsible for the unified storage and analysis of data. Northbound provides data calls to the business platform through standard API interfaces; the business platform implements various business logic based on the original data of the data platform, and externally Presented are services.
Among them, the communication protocol focusing on the network layer is a group of heroes competing for each other, and a hundred schools of thought contend.
At present, the most popular Wi-Fi technology has fast data transmission speed, especially the 802.11ax technology is about to be born. In theory, 8 streams is not a dream. However, with the increase in speed, the power consumption increases sharply, and the transmission distance also becomes a problem. Long-distance transmission requires an AP to be bridged at a certain distance, which will greatly increase the cost. Therefore, Wi-Fi technology is more suitable for indoor wireless Internet access scenarios for terminal applications such as PCs and PDAs.
Bluetooth technology and Wi-Fi are handed over in the 2.4G frequency band, so there will be some interference problems in the same frequency band. The power consumption of Bluetooth is slightly lower than that of Wi-Fi, and the transmission speed is far less than that of Wi-Fi. There are many applications in asset tracking, positioning tags and medical sensors, such as smart watches, Bluetooth positioning, etc.
The power consumption of Zigbee technology is relatively small, and the communication distance is relatively short. It is a short-range and low-power technology, which is mainly used in wireless sensors and medical scenarios.
UWB ultra-wideband technology has a relatively clean frequency band without interference from other frequency bands, and is more used in high-precision positioning scenarios.
Communication Protocol Comparison
The above technologies are more suitable for data transmission in close-range scenarios, so what technologies are available in long-distance scenarios?
The 4G network provided by the operator is the most widely used in people's lives, even more than Wi-Fi. It can transmit over long distances, and the speed is impressive, whether indoors or outdoors. This kind of technology looks superior, but its power consumption is high, and it can only be used in IoT scenarios where the terminal can obtain electricity by itself, such as a company's shared bicycle, which uses solar panels to obtain electricity.
In a long-distance scenario, if the terminal cannot solve the power supply problem, a technology with lower power consumption and wider coverage is required to meet the IoT communication requirements in this scenario. Therefore, driven by business and technology, some experts and enterprises have developed a new type of communication technology - LPWAN, that is, low-power wide-area network technology, in order to solve this problem.
The goal of LPWAN is a long-range wireless network communication technology optimized for M2M (device-to-device) communication scenarios in IoT applications. The advantages of LPWAN technology are mainly reflected in: low speed, ultra-low power consumption, long distance, low throughput, and strong coverage. These characteristics just show that this technology is developed for the Internet of Things in the scenario of long-distance transmission. Specific applications include: urban coverage, remote meter reading, manhole cover detection, and offshore fishing boat detection.
LPWAN technical features
As a new technology camp, LPWAN is divided into two major factions: licensed frequency bands and unlicensed frequency bands. Licensed frequency bands are further divided into EC-GSM, eMTC and NB-IoT; the "top card" of unlicensed frequency bands is LoRa.
EC-GSM
With the rise of LPWAN, the disadvantage of traditional GRPS applied to the Internet of Things becomes more and more obvious. In 2014, the 3GPP research project proposed to migrate the narrowband (200kHz) IoT technology to GSM, seeking a wider coverage 20dB higher than traditional GPRS, and proposed five goals: improving indoor coverage performance, supporting large-scale device connections, Reduce device complexity, power consumption and latency. By 2015, the TSG GERAN #67 meeting report stated that EC-GSM has met five major goals. But after the R13 NB-IoT standard was frozen, more energy was put into the redefined standard.
eMTC
The concept of eMTC was officially named in R13, and the previous R12 was called Low-Cost MTC, which is an IoT technology based on LTE evolution. eMTC is deployed on a cellular network, and user equipment can directly access the existing LTE network by supporting a 1.4MHz radio frequency and baseband bandwidth. The key capabilities of eMTC are high speed (compared to GPRS, zigbee, etc.), mobility, positioning, and support for voice. .
NB-IoT
The recently hot NB-IoT is actually a fusion of NB-CIoT and NB-LTE. NB-CIoT proposes a brand-new air interface technology, which is significantly changed compared to the traditional LTE network. It is satisfied with the five goals put forward at the TSG GERAN#67 conference. The highlight is that the cost of communication modules is lower than that of GSM and NB-LTE modules. And NB-LTE is compatible with existing LTE, the characteristic is to facilitate the deployment. After a fierce debate, the two were finally merged to form the technical standard of NB-IoT.
The full name of NB-IoT is the narrowband Internet of Things, which can be directly deployed in the LTE network, and the good compatibility reduces the cost of deployment. It has lower power consumption. It is theoretically estimated that the battery-based standby time of the terminal module carrying NB-IoT can be as long as 10 years. The reduction in module cost has also allowed more companies in the market to start applying this technology, one of which is the shared bicycle that is popular across the country. A company's third-generation smart lock uses NB-IoT modules. On the one hand, it is vigorously promoted by operators, and on the other hand, it does bring value.
LoRa
The development that goes hand in hand with NB-IoT is LoRa. The difference is that LoRa technology uses unlicensed frequency bands. It is an ultra-long-distance wireless transmission technology based on spread spectrum technology adopted and promoted by Semtech. The full name of LoRa is Long Range. As the name suggests, LoRa can support long-distance transmission. In China, LoRa can use two frequency bands: CN779-787 and CN470-CN510. Since the maximum transmit power of CN779-787 is only 10dBm (10mW), it has no "practical" value. Therefore, people prefer the frequency band CN470-CN510, and its maximum transmit power can reach 17dBm (50mW).
Similar to the Wi-Fi Alliance, LoRa also has a corresponding LoRa Alliance, which aims to jointly establish standards and specifications. LoRaWAN is such a product.
Comparison of LoRa and NB-IoT
Based on cost considerations, the unit price of LoRa's modules is around US$8-10, and the unlicensed frequency band does not need to pay additional spectrum costs. Compared with NB-IoT, it has a greater cost advantage. In terms of battery performance, since NB-IoT works on the cellular licensed spectrum, network synchronization needs to be performed regularly, which will consume corresponding power, while LoRa has no such concern, but this feature of NB-IoT is also warmly welcomed by shared bicycles , based on this, the real-time positioning of the vehicle can be done. In addition, from the business model point of view, NB-IoT belongs to the operator's network construction, and the business side does not need to consider the deployment of the base station, which is more worry-free; but at the same time, the quality and security of the network are uncontrollable risks, and The value-added of the enterprise itself will also be hindered to some extent. On the other hand, LoRa belongs to the enterprise's self-built network. The base station needs to be deployed by itself, and then it needs to be operated, maintained and optimized by itself. The coverage points, network quality and security are all responsible for it.