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What is LORA?
What is LORA?
Whenever someone asks me "what is LORA", if I don't know why he asked me this question, it is difficult for me to know how to answer his question, because LORA does not only refer to a thing, So I will let the editor of Chengdu Yibyte Electronic Technology Co., Ltd. answer this question for everyone. Technically speaking, LORA is a radio modulation scheme - a multi-symbol modulation radio signal using Chirp method; LORA technology also refers to systems that support modulation, including LORA chips and gateways; sometimes it refers to LORA communication networks in IoT applications. In essence, LORA chips are very cheap, but they have high acceptance sensitivity And low bit error rate (BER).
This means that in low-speed application scenarios, using LORA can get LoRaWAN farther than using other radio technologies of the same price. LoRaWAN is a media access control ( MAC) layer protocol, built using Semtech's LoRa modulation scheme (LoRa is just a physical layer protocol). However, LoRaWAN is rarely used in industrial (private network) application scenarios, it is more suitable for LoRa Wireless module public wide area networks because all channels are modulated to the same frequency ;For a private network, in order to avoid conflicts, it is best to have only one network running. The above picture is a network architecture diagram of LoRaWAN, all gateways in the network are bound to the same server, and the server decides which gateway should respond to the transmission. In a large In the network, any given transmission is usually detected by multiple receivers; then the server notifies a gateway to respond, and other gateways ignore the transmission.
This process helps to avoid conflicts between uplink and downlink, because only one gateway is transmitting, and overlapping A gateway can simply listen for other transmissions. What many people don't realize is that there is a way to use LoRaWAN's underlying technology (aka LoRa) without using LoRaWAN. LoRa module For example, Link Labs' Symphony Link in Semtech's A proprietary MAC layer is used on the chip, making it more suitable for enterprise and industrial customers who need to securely connect IoT devices to the cloud. In addition, there are many companies using LoRa chips in other protocols. From Answer "What is LoRa" at the technical level From a technical point of view, bluetooth Wireless Module is a unique modulation method. Semtech RF components (SX1272, SX1276/7/8 transceiver chips) integrate LoRa modulation technology (this technology is a proprietary modulation technology, currently Technical details have not been disclosed), the technology is called frequency modulation (FM) Chirp.
The core technology of LoRa is to use fractional phase-locked loop (PLL) to generate a stable Chirp signal. Other modulation formats include frequency shift keying (FSK), phase shift Keying (PSK), etc. It is important to note that LoRa itself does not describe system functionality above the physical (RF medium) layer. Let's first look at the Chirp signal (this word comes from the signal characteristics of the bird's call of the same name, and it can also be called frequency sweep for signal processing). The characteristic of Chirp is that the frequency of the signal changes with a certain rule, while the signal of FSK will only switch between two frequency points. The following figure is a linear Chirp signal time domain diagram. LoRa Internet of Things Protocol Semtech acquired the French Cycleo SAS for $5 million in 2012, thus obtaining LoRa wireless technology. The modem can filter the Chirp signal when processing the LoRa message, so it can obtain additional processing gain and improve the receiving sensitivity. In order to "lock" the LoRa signal, a long "constant Chirp" preamble needs to be transmitted (see Figure 1). This is the uniqueness of Lora - very high receiving sensitivity can be obtained using cheap chips and crystals.
This leading signal can be set to a variable number of "symbols", that is, the number of Chirps. It is conceivable that there is no selectivity between the preamble signals of different LoRa transmitters, but the LoRa demodulator can listen to a constant Chirp signal at the appropriate frequency and Chirp change rate (regardless of whether it comes from the intended system or not). The anti-interference performance of a LoRa receiving system in the face of conventional power interference and LoRa interference is very important, which is also the key technology of Symphony Link. Once the LoRa modem "locks" to the preamble, the end of the preamble is signaled by the "Reverse Chirp" shown in Figure 1. Data transmission then begins, which has a series of "symbols" that function much like M-ARY FSK symbols, but occur on Chirps, see Figure 2. Another powerful feature of LoRa is the ability to demodulate several "orthogonal" or simultaneous signals of the same frequency, as long as they have different chirp change rates. In the data sheet, the LoRa Chirp change rate is called the spread factor (Spread Factor). The higher the spread factor, the slower the Chirp change. Semtech's SX1301 chip supports this feature and has the ability to decode many LoRa Chirps simultaneously, a feature that makes it possible to create large networks. Building such a LoRa network or system requires a lot of development. Going from LoRa to a wireless system is like going from a BPSK wireless chip to a WiFi network. OSI Layer 2 and above functions for large networks include gateways, repeaters, addressing, adaptive data rates, message retries, message acknowledgments, and high-capacity OFDM downlink signaling, which are functions of systems such as LoRaWAN and Symphony Link. LoRa Alliance The LoRa Alliance was founded in 2015 to standardize the MAC function of the LoRa network. The LoRa Alliance developed the LoRaWAN protocol to facilitate mobile network operators using unlicensed spectrum to communicate with IoT devices on their networks. Some details about LoRaWAN are listed below: LoRaWAN is a server-side implementation of a multi-access protocol designed to reduce collisions for a large number of endpoints. It requires a server application to run the MAC function on the network connection; LoRaWAN network architecture usually adopts a star topology, where the gateway is a transparent bridge that relays messages between the end device and the backend central network server; the client logic is built into the network in a server; it is primarily designed for uplink-only applications with multiple endpoints, or applications that only require a small number of downlink messages (limited by the number of applications or endpoints); gateways in the same network need to be synchronized; end-devices and Communication between gateways is distributed over different frequencies and data rates. There is a trade-off between transmission distance and data rate (that is, the longer the transmission distance, the lower the data rate); Different data rates do not interfere with each other and create a set of "virtual" channels to increase the capacity of the gateway; LoRaWAN network server Data rate and RF output per end device managed through an Adaptive Data Rate (ADR) scheme, which is typically updated every 24 hours; Multi-layered security/encryption (EUI64 at network level and application level and EUI128 keys specific to the device ); AES CCM (128 bits) is used for encryption and authentication; The working range is within the range of 1% and 10% of the transmission time duty cycle ETSI, working in the 868 band; According to the draft, the B-type downlink node can be Polling a beacon from 1 second to 128 seconds (now using the engineering prototype provided by IBM's LMiC), the beacon period is 128 seconds (2^n), where n is 0 to 7; antenna diversity, because all gateways listen to the same uplink channel. LoRa Technology Applications Some companies are using all LoRa technology and LoRaWAN technology in interesting ways.
Chinese bike-sharing company OfO, which has equipped its bikes with LoRa devices and radio-frequency technology to determine the location of bikes, operates in more than 180 cities in China. Another example of LoRa network utilization comes from PNI Sensors in Santa Rosa, California. PNI uses LoRaWAN-based wireless connectivity to provide real-time city parking data, making it easier for drivers to find available parking spaces for on-street and off-street public and private parking management. The ultimate goal is to reduce traffic congestion and carbon emissions, which are caused by drivers repeatedly turning back and forth to find a parking space. Many industries are utilizing the open LoRaWAN IoT device standard, including agriculture (for irrigation/water level monitoring and pest control), utilities (for smart meters, lighting and energy management scenarios) and building construction (for building door and window sensors and Building Structural Health Applications).
There are also many companies that do LoRa networks that are not based on LoRaWAN. Deploying IoT devices with LoRa modules If you want to build on a public network owned and operated by an operator, LORAWAN is a very good choice, there are a lot of hardware and network servers providing services in this field, so there are many options is also a Very big advantage. However, the process of developing and deploying a system around LORAWAN is quite complicated. If you do not have much professional knowledge or experience in radio frequency protocols or wireless systems and planning, this will be a challenge. You also need to consider whether deploying a LORAWAN network can meet need. In some cases it may be better to use a custom protocol, where all you have to do is send the data to a node already written to link to the cloud. That's all for today's sharing. EBYTE people are committed to better assisting the development of IoT, intelligence, and automation every day, improving resource utilization, more products and more information. Interested partners can log in to us Visit the official website of Ebyte to understand, and there is also online customer service to answer questions!
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