Since the emergence of the Low Power Wide Area Internet of Things (LPWAN), after just a few years of development, it has become the focus of attention in the industry. Tencent Cloud has accumulated a lot of experience and lessons in LPWAN. This article will introduce our technical exploration and application practice in LPWAN access network and terminal solutions in detail. LPWAN, a new generation of IOT underlying communication technology Back in 2000 or so, the underlying technical support for the Internet of Things was still "ZigBee," although at the time, the terminal power consumption of ZigBee was not very large, but "the complexity of the topology led to the difficulty of engineering implementation" and "the overall size of the network led to the overall "Inefficiency" has become the main factor limiting its development. The appearance of LPWAN technology solved several problems above, and thus officially appeared as a new generation of IOT underlying communication technology in the public's view. However, the key to determining whether a technology can be used on a large scale is the input-output ratio of the technology, and whether there is an order-of-magnitude advantage over the previous generation. In both areas, LPWAN has obvious advantages. For example, in terms of low power consumption, the LPWAN achieves the landmark milestone of being able to work in a battery-powered environment for several years while still being able to communicate over the wireless network. Second, on the scale of the network, the LPWAN pursues a 1,000-fold or even 10,000-fold ratio. Cover radius of 2 to 10 kilometers. This means that a large number of terminal equipments can be supported with fewer base stations. The currently available domestic LPWAN technologies mainly include NB-IoT (licensed band) and LoRa (open band). It is worth noting that unlike ZigBee and Bluetooth Mesh technologies, LPWAN technology uses a simpler star topology design. Tencent Cloud independently developed the Alpha protocol, which has undergone long-term evolution and large-scale application. The emergence of Tencent Cloud LPWAN has provided new ideas for low-power wide-area Internet of Things. The design of this protocol has nothing to do with physical layer selection. That is, the same protocol architecture can be built on various physical layers such as 433M, UNB, OFSK, and so on. Among them, Tencent Cloud first built a LPWAN access solution based on the LoRa physical layer. In fact, evaluating the capabilities of a technology network must start with coverage and capacity. Among these, "coverage", that is, communication distance, mainly depends on the technical selection of radio modulation schemes at the physical layer. "Capacity" is the scale of the network, which mainly depends on the design idea of ​​the communication protocol itself. After a large number of tests, Tencent Cloud LPWAN in the open environment, the communication distance can reach 10Km or more. In a typical urban environment, the communication distance can also reach 3 ~ 5Km. This achievement is enough to prove LoRa's excellent performance in communication distance. On the other hand, since the over-the-air wireless channel is essentially a resource shared by all terminals and base stations in the area, the most important consideration in terms of capacity is the use efficiency of communication interaction over the air channel. In this regard, Tencent Cloud LPWAN network protocol as the design goal of "the most lightweight communications." After completing a communication interaction, at least a few radio transmissions are required? Under various typical scenarios, is it possible to optimize the interaction timing and save a few launches? In special circumstances, will there be self-excitation and group panic effects? Channel occupancy? These are the concerns of the protocol design perspective. Based on these considerations, Tencent Cloud's LPWAN network technology team creatively reverses the optimization of the protocol itself, accumulating many exclusive optimization strategies. As a fully independent independent research and development intellectual property right communication protocol, in the long-term evolution and large-scale application, according to the needs of specific applications, continue to boldly iterate, constantly introducing features. However, this does not mean that there is a problem with Tencent Cloud LPWAN compatibility. In fact, the network technology team of Tencent Cloud LPWAN, through additional technical means, still maintains compatibility with the standard LoRaWan communication behavior. The Alpha protocol design of Tencent Cloud LPWAN is independent of the spectrum, and the same protocol architecture can be applied to any frequency band. However, involving specific equipment production and network construction, it is not allowed to have any uncertainty variable, and the frequency band must be determined when landing. The Alpha protocol, chip, and base station of Tencent Cloud's LPWAN network currently operate in the 470MHz to 510MHz frequency band in mainland China. Basic network services first Tencent cloud LPWAN to create the best network side equipment Core Network: Tencent Cloud Alpha mainly consists of three closely coupled parts. Among them, part of the logic runs in the firmware of the terminal chip, and part of the logic runs in the firmware of the base station chip. The most complicated part of the logic runs in a cloud system called the "core network." All the base station's communication data are all collected in this cloud, cooperate, and route the data to the corresponding application server according to the attribution. Especially after experiencing large-scale deployment of city-level networks, functional maturity is only one aspect of the Alpha core network. At the same time, the horizontally scalable system load acceptance architecture also makes it reliable. In addition, the core network has demonstrated its strength in monitoring, monitoring, operation, operation and maintenance, and production. Base station: Tencent Cloud LPWAN (LoRa) base stations are mainly developed to meet the needs of large-scale urban network construction. The base station relies on the functional support of the core network and accepts its centralized management. In a large number of actual deployments, the base station products have many unique designs due to severe operating conditions and complex practical applications. Networking services: The implementation of the city-level IoT network is still a complex project. In the process, it not only needs strong organization and coordination capabilities, complete tool chain support, ground team's control ability and construction quality control process, but the specific network construction steps will not be repeated here. Taking Beijing's network construction as an example, Beijing's network is a typical case of one-time planning for one-time coverage. The main urban area within the Fifth Ring Road, which includes a total of more than 500 base stations, is installed on the site of the China Tower. In the first month of preparation for exploration, the installation process lasted for two months. The highest peak was connected to 13 tower construction teams at the same time. Through strict training and acceptance procedures, the implementation quality was controlled. In the actual testing process, the results were significant. Build the best solution for hard terminal hardware products in the era of IOT After the basic network services are set up, the next major event will fall on the terminal hardware products. l Chip: The product is mainly developed to satisfy the integration requirements of a large number of terminal devices. The chip has built-in logic on the terminal side of the Alpha protocol and outputs a standard hardware serial port externally. l Communication Module: The Tencent LPWAN (LoRa) module is a very simple building block consisting of a chip and six external components. It is mainly designed to meet the needs of external partners to quickly verify technology interconnection. l Self-research terminals: mainly focus on "firefighting" and "air purification". Conclusion This article details Tencent Cloud's technological exploration and practice in the low-power wide area Internet of Things (IoP) LPWAN. Tencent Cloud's LPWAN (LoRa) access network & terminal solutions are already in the field of smart fire services, smart park solutions, and digital factories. Successfully applied. In the follow-up, Tencent Cloud will continue to increase its R&D and investment in the Internet of Things, and accelerate the landing of the Internet of Things. Lifting Hopper Concrete Drum Mixer
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