Lora is a physical layer or wireless modulation used to establish a long-distance communication link. Many traditional wireless systems use frequency shift keying (FSK) modulation as the physical layer because it is a very effective modulation to achieve low power consumption. Lora is based on LFM spread spectrum modulation, which maintains the same low power consumption characteristics as FSK modulation, but significantly increases the communication distance. Linear spread spectrum has been used in the military and space communication fields for decades. Because it can achieve long communication distance and robustness to interference, it was first commercialized.
Lora and lorawan
Lora's advantage lies in its long-distance capability in technology. A single gateway or base station can cover the whole city or hundreds of square kilometers. At a given location, the distance depends largely on the environment or obstacles, but Lora and lorawan have a link budget better than any other standardized communication technology. The link budget, usually expressed in decibels (DB), is the main factor that determines the distance in a given environment.
Lorawan defines the communication protocol and system architecture of the network, and Lora physical layer enables long-distance communication links. Lorawan is designed from the bottom up to optimize lpwan (low power wide area network) for battery life, capacity, distance and cost. For different regions, a lorawan specification summary and a high-level comparison of different technologies competing in the lpwan space are given.
Nodes in lorawan network communicate asynchronously, and communicate when the data they want to send is ready, whether it is event driven or time scheduling. In mesh networks or synchronous networks, such as cells, nodes must wake up frequently to synchronize the network and check messages. This synchronization obviously consumes energy and is the first push to reduce battery life. In a recent study, GSMA compared different technologies to solve lpwan space. Lorawan has 3 to 5 times advantages over other technologies.
Lora alliance dedicated to ultra long distance wireless communication solutions
Characteristics of Lora
Lora, as a wireless technology, is based on the sub GHz frequency band, which makes it easier to communicate with low power consumption for long distance. It can be powered by batteries or other energy collection methods. The lower data rate also extends the battery life and increases the capacity of the network. Lora signal also has strong penetration to buildings. These technical features of Lora are more suitable for low-cost large-scale IOT deployment.
The key data in the figure is its receiving sensitivity. The receiving distance can reach 15km, the receiving current is 10mA, and the sleep current is < 200m.
Key characteristics of Lora technology for IOT application deployment
Lora's network capacity
In order to realize the long-distance star network, the gateway must have very high capacity or performance, and receive messages from a large number of nodes. The high network capacity is realized by the adaptive data rate and the multi-channel multi modulation transceiver in the gateway, so the messages can be accepted on multiple channels at the same time. The key factors affecting capacity are the number of concurrent channels, data rate (over the air time), load length, and how often nodes send data. Because Lora is based on spread spectrum modulation, when different spreading factors are used, the signals are actually orthogonal to each other. When the spreading factor changes, the effective data rate also changes. The gateway takes advantage of this feature and can accept multiple different data rates on the same channel at the same time.
If a node has a good connection and is close to the gateway, it has no reason to always use the lowest data rate, and it takes longer to fill the available spectrum than it does. The higher the data transmission rate, the shorter the time in the air, which can open more potential space for other nodes to transmit data. The adaptive data rate also optimizes the battery life of the node.
For the adaptive data rate to work, the symmetric uplink and downlink require sufficient downlink capacity. These characteristics make lorawan have very high capacity and the network is more scalable. The network can be deployed with the minimum amount of infrastructure. When capacity is required, more gateways can be added to change the data rate, reduce the number of crosstalk, and expand the network capacity by 6-8 times. Other lpwan technologies do not have the scalability of lorawan. Due to technical tradeoffs, it limits the capacity of the downlink and makes the downlink distance and the uplink distance asymmetric.
Landing of Lora
Lpwa can be divided into two categories: one is Lora, sigfox and other technologies working in unlicensed spectrum; The other is the 2 / 3 / 4G cellular communication technology supported by 3GPP, such as ec-gsm, LTE cat-m, Nb IOT, etc. working in the authorized spectrum.
South Korea has achieved Lora deployment covering 99% of the population, while China is still in the initial stage, and there is no mature network. Many giants such as China Mobile and ZTE are promoting Lora. However, there is also a voice of Wan communication technology in China, that is, Nb IOT promoted by China Mobile and Huawei. However, both technologies are in the strategic layout stage, and most other technologies are in the wait-and-see stage. Enterprises using Lora technology to make smart homes and smart communities are still in the experimental stage. However, Lora's test reputation is good, low power consumption and high stability. Therefore, Lora is worth studying and promoting, and it is not a "blind trick".
Lora architecture
LoRa 、Wi-Fi 、BLE
From the perspective of Lora replacing Wi Fi or 3 / 4G, the technology itself has too little bearing on individual traffic bandwidth. Compared with ble, it is difficult to compete in the civil market of near-field communication control, so it is almost impossible to replace ble in many aspects of smart home.
Lora wants to enter the smart home field. It needs to face the advantages of ZigBee, Bluetooth and Wi Fi as access interfaces. Lora needs to devour the existing wireless market share of smart home. If there is no strong smart home manufacturer behind it, it will be difficult to layout successfully. Moreover, no smart home enterprise can say that it has done a lot. However, from the internal information, Some advanced smart home enterprises in China have started to study Lora wireless system. If the opportunity is ripe, there is also the possibility of a big push in China.
Lora's chip supplier Semtech
"Encirclement and suppression" and "breakthrough" faced by Lora
In fact, the Internet of things is not lack of technology, including Wi Fi, 3G / 4G and ble, which are all expanding the Internet of things solutions for large-scale networking. Lora is a very difficult enterprise to popularize and enter the civil market. It needs a lot of resources to be integrated, and large operators need to layout and promote it. For example, China Mobile, ZTE and Huawei, although they have already deployed, many giants use a variety of Internet of things technologies to separate the market, It may not be able to land Lora or other advanced technologies.
Although many technologies have occupied the Internet of things market one after another, the place and scenario of application and the difficulty of development determine the market share in the future, which will be divided more and more carefully in the future. At present, the RF wireless modules used in remote wireless control, telemetry, automatic meter reading system, wireless sensor system, building community automation and security, container information management, modern agricultural irrigation, etc. only have a transmission distance of 1-2km in the suburbs, so Lora has unlimited potential in this market segment.
Lora positioning technology
Since Lora uses a special spreading technology, terminals of different spreading sequences will not interfere with each other even if they transmit at the same time using the same frequency. The concentrator / gateway developed on this basis can receive and process the data of multiple nodes in parallel, greatly expanding the system capacity. The ranging and positioning function based on this technology will promote its large-scale application in the field of Internet of things.
Indoor positioning of Lora
Can it really be applied in a large area? Ibeacon, which has sprung up in the past two years, uses Bluetooth technology to make indoor positioning accurate to 1m, while large-scale positioning GPS technology has been very popular. Lora's positioning accuracy of 5 meters within 10 kilometers is not pleasing to anyone on both sides. What is the benefit to the actual commercial application operators?
Editorial Reviews
The various wireless network communication technologies required by the Internet of things are complementary. In different scenarios, the distance, power consumption, capacity, cost and other indicators are different. However, Lora (long range) technology is rapidly developing in long-distance and low-power scenarios. Lora technology has outstanding characteristics in high performance, long distance, low power consumption, supporting large-scale networking, ranging and positioning. Another reason for large-scale application of Lora is that it is free of license band. Now, it has been 11 years since the birth of IOT. The commercialization is the most difficult and most progressive success. Lora is currently a pioneer. The important reason why Lora can be commercialized is that compared with other similar technologies, Lora is more open. It remains to be seen whether the technologies of sigfox, lorawan and Nb IOT will eventually become niche technologies like WiMAX in those years.
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