News

You are here: Home > News > Content

What Is LoRa Technology?

Edit:Aifon Technology Co.,Ltd      Date:Mar 18, 2017

LoRa is a wireless communication technology dedicated to long-distance and low-power. Its modulation method greatly increases the communication distance compared with other communication methods. It can be widely used in the field of long-distance low-rate wireless communication. Such as automatic meter reading, building automation equipment, wireless security systems, industrial surveillance and control. With a small size, low power consumption, transmission distance, anti-interference ability and other characteristics, according to the actual application of the antenna gain adjustment.

LoRaWAN network architecture is a typical star topology, in this network architecture, LoRa gateway is a transparent relay, connecting terminal equipment and servers. Gateway and server through the standard IP connection, and the terminal device with a single hop with one or more gateway communication, all nodes are two-way communication.

LoRa gateway and module to the star network between the way, and LoRa module can be theoretically point-to-point polling way network, but the point-to-point polling efficiency is much lower than the star network. Gateway can achieve multi-channel parallel reception, while dealing with multiple signals, which greatly increased the network capacity. The use of Lora can also achieve ranging and positioning. LPWAN battery life is longer, for those who need to send a small amount of data sensors and applications is really low power consumption.

According to FDMA (frequency division multiplexing) to divide the different frequency bands to establish different subnet segments. Such as: a subnet work in 469MHz, another subnet work at 470MHz, the two subnets do not interfere with each other. There may be some deviation from the channel frequency value due to the difference between the hardware circuit and the crystal. The maximum number of single-ended uploads is 256. The number of terminal nodes ranging from a few gate can access a number of terminals and data transmission cycle and response speed requirements. Layout of the network Note that some places have signal dead zone, the need to increase the repeater to ensure that the gateway and the terminal of the air rate and frequency consistent, or can not establish communication. The smaller the bandwidth, the higher the requirements for the crystal. Frequency hopping, then for the interference has improved, the communication distance has no effect. Lorawan gateway communication protocol is used in international standards, can also be used to customize the agreement.

LoRa main parameters

Select semtech RF chip, SX1276 operating frequency band is 137-1020MHz band, the maximum transfer rate is 300kbps. The SX1277 maximum transfer rate is 40kbps, it is for the 5-40kbit / s rate of data transmission applications, such as security systems, SX1278 is 137MHz ~ 525MHz operating frequency band, the maximum transfer rate is 300kbps. For the SX1276 first reading data sheet,

Summarized as follows:

Operating voltage: 1.8 - 3.6 V

Working frequency band: 137 ~ 175MHz, 410 ~ 525MHz, 860 ~ 1020MHz

Modulation: LORA \ 2-FSK \ GFSK \ OOK

Transmit power: + 20dBm-100mW

Maximum bit rate: 300kbps

Communication protocol: SPI

 

Positioning and ranging

The LoRa measurement distance is based on the airborne transmission time of the transmitted signal rather than the received signal strength RSSI, and the positioning can be measured based on the multi-point (gateway) on the airborne transmission time difference for the point (terminal). Its positioning accuracy of up to 5m.

 

LoRa Gateway

LoRa gateway at the core location of the LoRa star network, is the terminal and server (Server) between the information bridge, is a multi-channel transceiver. LoRa gateways are sometimes referred to as LoRa base stations or LoRa concentrators, although the definitions are different but are actually the same meaning.

 

LoRa gateways use different spreading factors, and different spreading factors are orthogonal to each other so that the signals of different spreading factors can be demodulated in the same channel. Gateway and network server through the standard IP connection, the terminal through a single hop with one or more gateways to communicate, all the terminal communication is two-way communication, but also support software remote upgrade.

 

Several important features of the following gateways:

(1) gateway classification: At present, the definition is different, the gateway type is also different.

E.g,

According to the application of different scenarios can be divided into indoor type gateway and outdoor gateway;

According to the different communication methods can be divided into full-duplex gateway and half-duplex gateway;

In accordance with the design criteria can be divided into fully compatible with the LoRaWAN protocol gateway and not fully meet the LoRaWAN protocol gateway.

AIFON new generation gateway for the outdoor type, full duplex, and fully in line with LoRaWAN agreement. LoRaWAN agreement with the LoRa gateway and LoRa terminal to achieve interoperability, which is of great significance.

(2) the capacity of the gateway: Gateway capacity is a certain period of time the ability of the gateway to receive data packets. In theory, a single SX1301 chip has eight channels, in full compliance with LoRaWAN protocol in the case of up to 15 million packets per day to receive. If an application packet frequency of 1 packet / hour, a single SX1301 chip composed of the gateway can access 62500 terminal nodes. Of course, this is only a theoretical value, the number of gateway access terminal eventually with the number of gateway channels, terminal packet frequency, packet bytes and spread factors are closely related.

(3) Gateway access point determinants: LoRa gateway access to the number of nodes depends on the LoRa gateway can provide the channel resources and a single LoRa terminal occupied by the channel resources. LoRa gateway if the use of Semtech standard reference design, the gateway using SX1301 chip, then the number of channels is a fixed 8 uplink channel 1 downlink channel. The number of physical channels is determined, and the channel resources that the LoRa gateway can provide are determined. (Gateway design is different, the number of channels is different, AUGTEK gateway can achieve 8 uplinks, 4 downlink.) Single LoRa terminal occupied by the channel resources and terminal occupied channel time, also with the terminal packet frequency, packet number and LoRa terminal spread factor is closely related. When the LoRa terminal's packet frequency and packet number of bytes increased, the terminal will occupy the channel to send and receive time will increase, it takes up more channel resources. When the LoRa terminal uses a larger spread factor, the signal can pass farther, but the cost is to pass the unit byte of information will take more time.

In addition to the gateway, we also need to focus on LoRa terminal: LoRa terminal is part of the LoRa network, generally by the LoRa module and sensors and other components. LoRa terminals can be battery-powered and capable of remote positioning. Each terminal that complies with the LoRaWAN protocol communicates directly with the LoRaWAN-compliant gateway for interconnection.

LoRa band selection

By theory, any frequency in the 150 MHz to 1 GHz band can be used. But Semtech's LoRa chip is not all sub-GHz band can be used in the common frequency band (such as 433MHz, 470MHz ~ 510MHz, 780MHz and Europe and the United States commonly used 868MHz and 915MHz are common frequency band) outside the frequency and not very good support. AUGTEK dominates LoRaWAN 470 ~ 510MHz protocol standard development, currently in China to provide 470-510MHz frequency band gateway.

LoRa: easy to build and deploy low-power wide-area technology

LoRa was born earlier than NB-IoT. In August 2013, Semtech released a new chip based on ultra-long-range low-power data transmission technology (LongRRR), which is based on 1GHz. Its acceptance sensitivity reached a staggering -148dbm, compared with other advanced level sub-GHz chip industry, the highest receiver sensitivity improved by more than 20db, which ensures the reliability of network connectivity.

It uses linear FM spread-spectrum modulation technology, which maintains the same low power consumption as FSK (frequency shift keying) modulation, and significantly increases the communication distance while improving network efficiency and eliminating interference, i.e., different spreading Sequence of the terminal even if the same frequency at the same time to send will not interfere with each other, so on the basis of the development of the concentrator / Gateway (Concentrator / Gateway) can receive and process multiple nodes in parallel data, greatly expanding the system capacity.

 LoRa技术特点

Figure 1: LoRa technical features

Linear spread spectrum has been used in the field of military and space communications for decades because it can achieve long communication distance and interference robustness, while LoRa is the first low-cost implementation for commercial use. With the introduction of LoRa, the field of embedded wireless communications has undergone a radical change. This technology has changed the past on the transmission distance and power consumption of the compromise approach, to provide a simple long-distance, long battery life, large capacity, low-cost communication system.

 

LoRa mainly in the global free band operation (ie, non-authorized band), including 433,868,915 MHz and so on. LoRa network mainly consists of terminal (built-in LoRa module), gateway (or base station), server and cloud four parts, application data can be two-way transmission, as shown in Figure 2.

 LoRa网络架构

Figure 2: LoRa network architecture

 

LoRa advantage

Mainly reflected in the following aspects:

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

Up to 157db of link budget to make it up to 15 km (with the environment). Its receiving current is only 10mA, sleep current 200nA, which greatly delayed the battery life.

2, based on the technology of the gateway / concentrator to support multi-channel multi-data rate parallel processing, the system capacity.

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

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

LoRa's measurement of distance is based on the airborne transmission time of the signal rather than the traditional RSSI (Received Signal Sterngth Ind -ication), while the positioning is based on the multi-point (gateway) on the point (node) of the air transmission time difference measurement. Its positioning accuracy of up to 5m (assuming 10km range).

These key features make LoRa technology ideal for applications such as intelligent meter reading, intelligent parking, vehicle tracking, pet tracking, intelligent agriculture, intelligent industry, and intelligent city applications that require low power consumption, distance, large number of connections and location tracking , Intelligent community and so on applications and fields.


Copyright © Aifon Technology Co.,Ltd  E-mail:sales@aifontech.com
TEL:+86-755-21535969  FAX:+86-755-26700593

Aifon Technology Co.,Ltd