Technical Good article: an article to show you a quick and comprehensive understanding of lora!

The rapid development of the Internet of things has put forward higher requirements for wireless communication technology, and the Lpwan (Low-power wide-area Network and low Power WAN), designed for low bandwidth, low power consumption, long distance, and heavily connected IoT applications, is also booming. Nb-iot and Lora are the typical representatives and the two low power WAN communication technologies with the most development prospects.

These two kinds of Lpwan technology have wide coverage, many connections, low speed, low cost, less power consumption and so on, are suitable for the low power of Internet applications, are actively expanding their own ecosystems. However, there is a difference between the two. What are the overlapping or different areas of application. Between the two is a life-and-death alternative relationship or you have my complementary relationship.

This is also the issue that the smart product circle is trying to figure out, and then we will be launching a wide area IoT communication Technology feature article to introduce Lora and Nb-iot and the two technologies, their ecology, and their comparisons.

LoRa: Low-Power wide-area object-linked technology for easy construction and deployment

Lora was born earlier than Nb-iot, in August 2013, Semtech company released a new type of chip based on 1GHz of ultra long distance low-power data transfer technology (long Range, short Lora). Its acceptance sensitivity has reached astonishing -148dbm, and the highest reception sensitivity has improved by more than 20db compared to other advanced level Sub-ghz chips in the industry, ensuring network connectivity reliability.

It uses linear FM spread spectrum modulation technology, that is, such as FSK (frequency shift keying) modulation of the same low-power characteristics, but also significantly increase the communication distance, while improving the network efficiency and eliminate interference, that is, different spread spectrum sequence terminals, even if the same frequency of simultaneous transmission will not interfere with each other, Therefore, the Concentrator/Gateway (Concentrator/gateway) developed on this basis can receive and process data of multiple nodes in parallel, greatly expanding the system capacity.

Figure 1:lora Technical Features

Linear spread spectrum has been used in the military and space communications for decades, because it can achieve long communication distance and interference robustness, while Lora is the first commercial use of low-cost implementation. With the introduction of Lora, the situation in the field of embedded wireless communication has changed completely. This technology has changed the previous compromise on transmission distance and power consumption, providing a simple communication system that can achieve long-distance, long battery life, large capacity and low cost.

Lora is mainly run in the global Free frequency band (that is, not authorized frequency band), including 433, 868, 915 MHz, etc. Lora Network mainly consists of terminal (built-in Lora module), Gateway (or base station), server and cloud four parts, application data can be transmitted in two directions, as shown in Figure 2.

Figure 2:lora Network Architecture

The advantages of Lora are mainly embodied in the following aspects:

1, greatly improved the sensitivity of the receiver, reducing the power consumption.

Up to 157db of the link budget makes its communication distance of up to 15 km (environment-related). Its receiving current is only 10mA and the sleep current is 200nA, which greatly delays the battery's service life.

2. The gateway/Concentrator based on this technology supports the parallel processing of multi-channel multi data rate, and the system capacity is large.

As shown in Figure 2, a gateway is a bridge between a node and an IP network (via 2G/3G/4G or Ethernet). Each gateway can handle communication between nodes 5 million times per day (assuming 10Bytes per send, network occupancy rate 10%). If the gateway is installed in the existing mobile communication base station, transmit power 20dBm (100mW), then in the construction-intensive urban environment can cover about 2 km, while in the lower density of the suburbs, the coverage can reach 10 km.

3, based on terminals and concentrator/gateway system can support ranging and positioning.

Lora measurement of distance is based on the signal air transmission time rather than the traditional rssi (Received Signal sterngth ind-ication), while the positioning is based on the multi point (Gateway) to a point (node) of the air transmission difference measurement. Its positioning accuracy is up to 5m (assuming 10km range).

These key features make Lora technology very suitable for applications such as intelligent meter reading, intelligent parking, vehicle tracking, pet tracking, smart agriculture, intelligent industry, Intelligent City, intelligent community and so on, which require low power consumption, long distance, large connectivity and positioning tracking.

At present, compared to Nb-iot,lora is currently the most mature and stable narrowband communication technology, its free network of private networks is far superior to the continuous charge of NB network operators, and Lora a network for a lifetime without payment. However, the application of Lora to the development of Internet communication is difficult, long cycle and high entry threshold. It is understood that in order to reduce the Internet industry entrepreneurs to enter the threshold, the association Chengzhihui provides a complete set of mature LoRaWAN source code +lora Gateway customization program, greatly reduced the entrepreneur in the network of things linked to the cost of the six-year cycle and the huge development costs, facilitate the rapid access to specific applications, To build their own independent networking operation brand.