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Introduction to Lora, lorawan and Lora Alliance

Source: unknown Editor: admin Time: 16:43, May 14, 2019

The full name of Lora is "long range". From its full name, Lora has reflected the characteristics of this wireless technology: wide coverage (link budget up to 168db).
 

Lora technology is a kind of spread spectrum wireless modulation patent technology (ep2763321 from 2013 and us7791415 from 2008) developed by a French company cycleo (established in 2009, an IP and design solution provider). It was acquired by Semtech company in 2012 for about US $5 million. After the acquisition, Semtech has launched a strong marketing campaign for the technology, including the establishment of the Lora alliance to promote the participation of other companies, including some mobile operators, into the Lora ecosystem.

 

 

Lorawan defines the end-to-end standards and specifications for using Lora technology, including market security, energy efficiency, roaming and on-board. Lorawan was originally called loramac, which was jointly developed by Semtech, actiity and IBM research. It was renamed lorawan at the mobile world communication conference in Barcelona in 2015 and became the specification for members of Lora alliance. The lorawan specification can be downloaded from the Lora alliance website: www.lora-alliance.org The difference between lorawan and lorawan is that lorawan is a technology and lorawan is a set of standards.

 

1. What is lorawan
 

According to the introduction of lorawan, the official white paper of Lora alliance, lorawan is a set of communication protocol and system architecture designed for Lora long-distance communication network. In addition, the government provides the protocol hierarchy diagram of slightly biased Technology (as shown in the figure below).


In the design of protocol and network architecture, lorawan fully considers several factors, such as node power consumption, network capacity, QoS, security and network application diversity. After the following contents, we will have a deeper understanding of the introduction at the beginning.

 

2. Interest group behind lorawan - Lora Alliance
 

NB IOT, which falls in love with Lora, comes from 3GPP, the global organization for standardization. It is composed of ETSI, ARIB and TTC, CCSA, TTA of Korea and ATIS of North America Yes.

Compared with the root of 3GPP, the Lora alliance behind lorawan is weaker. It can be seen from the cover of the agreement that the authors are from three board members: n. sornin (Semtech), M. Luis (Semtech), T. EIRICH (IBM), t. Kramp (IBM), and o. Hersent (activity).

Lora alliance was jointly founded by Cisco, IBM and Semtech in the first half of 2015. Up to now (April 2017), there are 400 + members and many large enterprises on the board of directors. We are working together to carve up the cake of low-power Wan in the future.

We know that the promotion of every technology is accompanied by the promotion of interests. Although organizations and alliances are non-profit organizations, the members of its enterprises are not dedicated to public welfare. From the perspective of enterprises, what we spend 50000 dollars on is destined to be done with the expectation of at least 500000 US dollars. The following table collects 19 board members who have paid $50000 in alliance dues at this stage, and you can see the ambition of these enterprises.

Telecom operators

Bouygues

One of the top three mobile network operators in France

Comcast

The largest cable TV operator in the United States

KPN

Royal Telecom Group

Orange

French telecom operators

Proximus

Belgian telecom operators

SK telecom

Korean telecom operators

Network security solution provider

Gemalto

Jin Yatuo, a network security solution provider, is a partner of China Mobile, involving network encryption design

Giesecke

Jiede, a payment security solution provider, involves network encryption design, and is a u-shield solution provider of ICBC and CCB

Cloud platform solution provider

Actility

Thingpark cloud platform, France

IBM

Platform solution provider

ZTE

ZTE, platform solution provider, base station solution provider

Base station solution provider

Cisco

Cisco

Kerlink

Base station solution provider

Sagemcom

Base station solution provider

Terminal chip solution provider

Semtech

Suntech, Lora RF chip supplier

ST

Microcontroller supplier

Renesas

Renesas, microcontroller supplier

Industry application solution provider

Flashnet

Energy management application providers, such as smart streetlights

Homerider

Smart water meter application provider

 

3. Network deployment of lorawan
 

After binding several first-class telecom operators, the network deployment situation is quite considerable. According to the official statement (April 2017) and network deployment (as shown in the figure below), 34 networks have been publicly announced to be deployed, and at least 150 cities are under pilot deployment.

 
 

4. Lorawan network architecture
 

After understanding the basic situation of lorawan, we do some brief analysis from the technical point of view. The official network structure of Ralo is shown in the figure below.

 

 

We can see that a lorawan network architecture includes four parts: terminal, base station, NS (network server) and application server. The star network topology is used between the base station and the terminal. Because of the long-distance characteristics of Lora, single hop transmission can be used between them. There are six typical applications listed in the terminal section. For details, you will find that the terminal node can send to multiple base stations at the same time. The base station forwards lorawan protocol data between ns and terminal, and carries lorawan data on Lora RF transmission and TCP / IP respectively.

 

Let's take a look at this network architecture in combination with the industry ecology. We can have a deeper understanding of lorawan.


 

5. Overview of the agreement
 

5.1 classification of terminal nodes

In the introduction at the beginning, we can see that there are class A / B / C terminal devices specified in the protocol, which basically cover all application scenarios of the Internet of things (as shown in the table below).

Class

introduce

Down time

Application scenarios

A (‘all’)

Class a terminal uses ALOHA protocol to report data on demand. After each uplink, two short downlink receiving windows are followed to realize two-way transmission. This operation is the most energy-saving.

It is necessary to wait for the terminal to report data before sending data.

Garbage can monitoring, smoke alarm, gas monitoring, etc

B (‘beacon’)

In addition to the random receiving window of class A, the terminal of class B will also open the receiving window at a specified time. In order to enable the terminal to open the receiving window at a specified time, the terminal needs to receive time synchronized beacons from the gateway.

In the fixed receiving window of the terminal, the data can be sent, and the delay of sending is improved.

Valve controlled water gas meter, etc

C (‘continuous’)

The terminal of class C is basically open to receive window all the time, and only closes temporarily when sending. Class C terminals consume more power than Class A and class B.

Since the terminal is in continuous receiving state, it can send data to the terminal at any time.

Street lamp control, etc

 

5.2 uplink and downlink transmission of terminal node

Here's a sequence diagram to give you a deeper feeling.

This is the sequence diagram of the uplink and downlink of class A. at present, rx1 generally starts at 1 second after uplink, while rx2 starts at 2 seconds after uplink.


 

Class C and a are basically the same, except that during the sleep of class A, rx2 is opened.


 

The timeslot of class B is more complicated. It has a synchronous slot beacon and a fixed period receiving window Ping slot. In this example, the beacon period is 128 seconds and the Ping cycle is 32 seconds.

 

5.3 screening of terminal nodes
 

After understanding the basic concepts, you can understand how nodes work. Before sending and receiving data, the terminal must add network first.

There are two screening methods: over the air activation (OTAA) and activation by personalization (ABP).

Commercial lorawan networks generally follow OTAA activation process, so that the security can be guaranteed. This method requires three parameters: appeui and appeui.


 

Deveui is a global unique ID similar to IEEE eui64, which identifies a unique terminal device. It is equivalent to the MAC address of the device.

Appeui is a globally unique ID similar to IEEE eui64, which identifies a unique application provider. For example, each household's garbage can monitoring application, smoke alarm application, etc., all have their own unique ID.

Appkey is assigned to the terminal by the application owner.

After initiating the join process, the terminal will issue the add network command. After the NS (network server) confirms that there is no error, it will reply to the terminal and assign the network address devaddr (32-bit ID). Both parties use the relevant information and appkey in the reply to generate session keys nwkskey and appskey to encrypt and verify the data.

If the second screening method, namely ABP activation, is adopted, it is relatively simple and crude. The final communication parameters of devoddr, nwkskey and appskey are directly configured, and the join process is no longer needed. In this case, the device can send data directly.

 

5.4 data sending and receiving
 

After that, the data is encrypted.

Lorawan specifies that there are two types of data frames, confirmed or unconfirmed, that is, the type of response required and the type of no response required. Manufacturers can choose the appropriate type according to the application needs.

In addition, it can be seen from the introduction that one of the major considerations of lorawan design is to support application diversity. In addition to using appeui to divide applications, fport application port can also be used to process data separately during transmission. The value range of fport is (1 ~ 223), which is specified by the application layer.

 

5.5 ADR mechanism
 

We know that Lora modulation has the concept of spread spectrum factor. Different spread spectrum factors have different transmission distance and transmission rate, and have no influence on data transmission.

In order to expand the capacity of lorawan network, an adaptive data rate - ADR (adaptive data rate - ADR) mechanism is designed in the protocol. Devices with different transmission distance will use the fastest data rate according to the transmission status. This also makes the overall data transmission more efficient.

 

5.6 MAC command
 

According to the needs of network management, a series of MAC commands are designed to modify the network parameters. For example, the delay of receiving window, device rate and so on. In the process of practical application, it is seldom involved and temporarily neglected.

 

6. Regional parameters
 

In addition to the agreement, the official lorawan alliance also released a supporting supplementary document "lorawan regional parameters", which describes the specific parameters of lorawan in different regions of the world. In order to avoid the change of documents caused by the addition of new regions, the chapter of region parameters is separated from the protocol specification.

The figure below shows the specific physical layer parameters of lorawan in different regions of the world, not only the frequency band is different, but also the channel division, even the data rate, transmission power, maximum data length, etc.

Shenzhen Jiexun Yilian specializes in the production and development of industrial WiFi networking module, ZigBee, mesh ad hoc network module, RF radio frequency module, low power meter reading module, Lora, lorawan, nb-iot data transmission module, data transmission radio station, 3G / 4G / GPRS industrial communication gateway and wireless industrial system scheme of Internet of things. Company provides standard TTL / 232 / 485 / SPI interface data transmission module, industrial grade, high cost performance, especially suitable for wiring inconvenient place, welcome to contact!