LoRa (long distance) is a technology developed by Semtech. Its typical operating frequencies are 9 15MHz in the United States, 868MHz in Europe and 433MHz in Asia. LoRa's physical layer (PHY) uses unique FM LFM spread spectrum technology and forward error correction (FEC). This spread spectrum modulation allows multiple radios to use the same frequency band as long as each device uses a different chirp and data rate. Its typical range is 2km to 5km, and the longest range is 15km, depending on the location and antenna characteristics.
LoRa chip is at the core of the whole industrial chain, and its importance is self-evident. It is worth noting that at present, Semtech Company of the United States is the core supplier of LoRa chips and holds the core patent of LoRa underlying technology. Semtech has two main customers. One is a semiconductor company authorized by Semtech LoRa chip ip. Second, manufacturers who directly use Semtech chips as SIP chips, including Microchip, etc.
Wireless fidelity
Wi-Fi is widely used in many Internet of Things applications, most commonly as a link from a gateway to a router connected to the Internet. However, it is also used for major wireless links that require high speed and medium distance.
Most Wi-Fi versions work in the 2.4GHz unlicensed frequency band, and the transmission distance is as long as 100 meters, depending on the application environment. The speed of the popular 802. 1 1n can reach 300Mb/s, while the speed of the newer 802. 1 1ac working in the 5GHz ISM band can even exceed1.3gb/s/s. ..
A new version of Wi-Fi HaLow for Internet of Things applications will be launched soon. The code name of this version is 802. 1 1ah. The United States uses the unlicensed frequency band from 902MHz to 928MHz, and other countries use similar frequency bands below 1GHz. Although most Wi-Fi devices can only reach the maximum coverage of 100 m under ideal conditions, HaLow can reach 1 km with a suitable antenna.
802. The modulation technology of11ah is OFDM, which uses 24 subcarriers in the 1MHz channel and 52 subcarriers in a wider bandwidth channel. It can be BPSK, QPSK or QAM, so it can provide various data rates. In most cases, the speed of 100kb/s to several Mb/s is enough-the real goal is low power consumption. Wi-Fi Alliance revealed that it will complete the test and certification plan of 802. 1 1ah before 20 18.
Another new Wi-Fi standard for Internet of Things applications is 802. 1 1af. It is designed to use TV blank bands or unused TV channels in the range of 54MHz to 698MHz. These channels are suitable for long distance and NLOS transmission. The modulation technology is OFDM using BPSK, QPSK or QAM. The maximum data rate of each 6MHz channel is about 24Mb/s, but it is expected to achieve a longer distance in the lower VHF TV band.
ZigBee
ZigBee, also known as ZigBee, is a wireless network protocol with low speed and short distance transmission. The bottom layer is the media access layer and the physical layer which adopt the IEEE 802. 15.4 standard specification. The main features are low speed, low power consumption, low cost, support for a large number of online nodes, support for a variety of online topologies, low complexity, fast, reliable and safe. ZigBee is one of the ideal choices for the Internet of Things.
Although ZigBee generally works in 2.4GHz ISM band, it can also be used in 902MHz to 928MHz and 868MHz bands. In 2.4GHz band, the data rate is 250 KB/s.. It can be used in point-to-point, star and grid configurations and supports up to 254 nodes. Like other technologies, security is guaranteed by AES- 128 encryption. One of the main advantages of ZigBee is that it has pre-developed software application configuration files for specific applications (including the Internet of Things). The final product must be licensed.
What is the self-organizing network adopted by ZigBee technology? A simple example can illustrate this problem. When a group of paratroopers airborne, each person holds a ZigBee network module terminal. After landing on the ground, as long as they are within the communication range of the network module, they can quickly form an interconnected ZigBee network by automatically searching for each other. And because people move, the connection between them will also change. Therefore, the module can also refresh the original network by finding the communication objects again and determine the relationship between them. This is a temporary network.
N B- internet of things
Narrowband Internet of Things (NB-IOT) has become an important branch of the Internet of Everything. NB-IoT is built in a cellular network and consumes only about 180KHz bandwidth. It can be directly deployed in GSM network, UMTS network or LTE network, reducing deployment cost and realizing smooth upgrade.
NB-IoT is a new technology in the field of Internet of Things, which supports cellular data connection of low-power devices in WAN, also known as low-power WAN (LPWAN). NB-IoT supports efficient connection of devices with long standby time and high requirements for network connection. It is said that the battery life of NB-IoT equipment can be improved by at least 10 years, and at the same time, it can provide very comprehensive indoor cellular data connection coverage.
Bluetooth 5.0
Bluetooth is a wireless transmission technology. Theoretically, the equipment can be connected within a short distance of about 100 m, but in practice, it is only about 10 m. Its biggest feature is that it can easily carry mobile communication equipment and computers, and can be networked without cables to transmit data and information. At present, it is widely used in the connection of smart phones and smart wearable devices, smart homes, vehicle-mounted Internet of Things and other fields. The newly arrived Bluetooth 5.0 can not only be the product of the old version in backwards compatibility, but also bring the advantages of higher speed and longer transmission distance.