2021-12-01
557The full name of NB-IoT is the narrowband Internet of Things, which can be directly deployed in existing GSM, UMTS or LTE networks, and occupies a very low bandwidth to connect a large number of low-power devices to achieve the goal of reducing costs and smooth transition. An important branch in the concept of Internet of Everything. According to the planning roadmap, 5G will be officially commercialized in 2020, and this article will discuss the future of NB-IoT and the important impact of related technical specifications on the Internet of Things.
NB-IoT, also known as LTE Cat NB1, can connect billions of devices in a smarter way. It has a very high cost performance, supports low-cost devices and low-power connections, and provides a wider coverage. As an effective and feasible theory of economies of scale in the Internet of Things industry, low-power wide area network (LPWA) technology can cover almost all places and can operate compatible with existing mobile networks.
The main requirement of the new MTC (Machine Type Communication) application is to deploy low-power consumption, wider coverage, high-efficiency power supply for low-cost equipment, and match the radio access networks of different operators in different frequency bands. Under normal circumstances, these MTC applications include smart metering, property monitoring, agriculture, fleet and logistics management and other fields. Although the data generated by these devices is often very small, they are usually installed in blind areas of signal coverage, such as forests, farms or basements. The existing short-range communication networks and mobile cellular networks cannot cover these areas, and NB-IoT is Come out to solve this problem.
Working under authorized spectrum can better ensure coverage and performance, but operating under unlicensed spectrum is prone to various uncontrollable risks, which will affect the overall performance of many devices operating in the network.
Battery and coverage performance
Network density and link budget are the two main factors that affect mobile network coverage. Compared with technologies such as GPRS, WCDMA and LTE, the link budget of NB-IoT is 20dB more, and it can operate with lower data coverage.
Link budget comparison of communication technology:
The 20dB improvement also means making sacrifices in certain aspects, such as reducing the requirements for MTC applications, but it also brings many advantages. NB-IoT can meet the requirements of rate delay and battery life. The life span depends on how high-efficiency equipment switches into "sleep mode", which turns off some components of the battery when it is not in use.
Like LTE, NB-IoT uses two main RRC protocol states:
● RRC_idle: save power and resources for sending measurement reports
● RRC_connected: The device sends and receives data directly
NB-IoT design flexibility
In particular, it should be pointed out that NB-IoT technology can provide a certain range of data transmission rates. This depends on the channel quality, or the signal-to-noise ratio and the number of resources in the designated area (bandwidth). In addition, each device also has its own power budget, and several devices can integrate power.
In addition to the influencing factors of bandwidth, NB-IoT devices are more susceptible to signal strength in some scenarios. These devices can gather transmission energy to form a narrower bandwidth without losing performance, thereby saving more bandwidth resources for other devices. Moreover, what NB-IoT transmits is not a resource block, but a multi-frequency transmission or sub-carrier. The bandwidth of NB-IoT is 15kHz, while the effective bandwidth of the resource block is 180kHz. It is composed of 12 subcarriers with a bandwidth of 15kHz. There is a significant difference between the two.
Regardless of the signal strength, we can increase the data transmission speed by increasing the bandwidth for different situations within the signal coverage. By assigning multiple frequencies or sub-carriers to the device, the data transmission speed can be increased by up to 12 times. In this ideal state, the equipment is in the coverage area of strong signals, and the data transmission rate is also very fast. In the real environment, the best condition is that there are dense base stations around NB-IoT devices, or most of the devices are located within the original LTE coverage.
It is worth noting that when designing NB-IoT, good reusability is required and can be adapted to various transmission rates. The design target capacity proposed by 3GPP (standards organization) is 40 devices per household, or 52,200 devices per cell (in the city of London as an example); in the simulation operation, each cell can connect 200,000 devices, which is the original 4 times the target. Obviously, NB-IoT will meet the data transmission rate requirements when it is officially released.
About the equipment
Communication modules are obviously indispensable to deploy large-scale sensors. The monitoring and feedback process of different parameters (such as temperature and humidity) must be optimized. For scene applications that rely heavily on sensors, the data transmission rate and latency should be lower, and NB-IoT can meet these needs. NB-IoT devices have proven to be able to work in lower peak physical layer data transmission (100-200kbps range), and even support single-frequency transmission. In addition, NB-IoT devices have other advantages. For example, LTE MBB requires two antennas, while NB-IoT only requires one receiving antenna.
Another advantage of narrowband (NB-IoT is 200kHz, while other technologies range from 1.4MHZ to 20MHZ) is the complexity of digital-to-analog conversion, channel estimation, and lower buffering.
NB-IoT needs to connect everything
● Smart City:
Spend less money to track the needs of all aspects of the city. NB-IoT and LTE make it possible to control street lights, free parking spaces, and environmental conditions. As mentioned above, the NB-IoT communication module has a very competitive price advantage. The price of these modules is estimated to be around US$5.
● Intelligent building:
NB-IoT can provide support for broadband connections in buildings. Use the LPWA network to directly connect the sensors to the monitoring system to enhance security.
● Measurement:
The main requirement of smart metering is network coverage. Sometimes, meters need to be installed in remote rural areas or underground. Through regular and small data transmission, NB-IoT can monitor gas and water meters well.
● Consumer market:
Cat M1 is sometimes referred to as a replacement for NB-IoT. Both technologies can support large-scale sensors and support data connections at various levels of activity. For consumers, wearable devices are the cornerstone of the Internet of Things. One of the main challenges of the Internet of Things is how to explore a sustainable business development model. Compared to re-production, the maintenance cost of sensors and equipment may be more expensive.
