B.One Community Help
Internet of Things / LoRaWAN® in General
The term “Internet of Things” refers to a large-scale networking of various devices that can communicate with each other without human influence. The goal of the “Internet of Things” is to automatically collect relevant information from the real world and make it available to the network.
The collected status information is evaluated in order to be able to derive meaningful evaluations, for example for the energy management of a building or actions such as the opening/closing of a valve. The prerequisite for the Internet of Things is a standardised, secure transmission technology that enables cost-effective end devices with low energy consumption and a long range – all these requirements are covered by LoRaWAN®.
The abbreviation LPWAN stands for “Low Power Wide Area Network”. As the name implies, LPWANs are technologies that enable high transmission ranges and good building penetration with low energy consumption. LPWAN technologies were developed to meet the requirements of the “Internet of Things”, which cannot be realized by the classical transmission standards such as WLAN, mobile radio or Bluetooth.
In addition to the low energy consumption and the high range, LPWAN is characterized by the high scalability of the number of end devices, the low hardware costs and the security of the transmission. One limitation is the bandwidth of the transmission – only small amounts of data can be transmitted, which is, however, completely sufficient for applications in the “Internet of Things” sector.
LoRaWAN® is an LPWAN specification for battery powered wireless systems in regional, national or global networks. LoRaWAN® is up to the requirements of the Internet of Things (IoT), such as bidirectional communication, localisation of objects or living beings and mobility.
Compared to other LPWANs, LoRaWAN® is the cheapest and can be used worldwide in free radio bands. LoRaWAN® is particularly resistant to interference due to frequency spreading by the → “Spreading Factor”, so that the signals can be transmitted completely despite possible interference.
LoRaWAN® is used in the housing industry for the acquisition of measured values from heat meters, water meters, heat cost allocators as well as for the functional testing of smoke alarms. This means that the requirements for remote reading of consumption information for users during the year, as required by the amendment of the EED Directive 2012/27/EU, which came into force on 25 December 2018, are already fully met.
In addition, the low costs per terminal device open up areas of application where previously no economical recording of status information was possible. Examples include tracking the position of objects, the intelligent control of street lighting, monitoring the level of garbage or the early detection of maintenance requirements for machines.
The LPWA networks cover a larger geographical area than the classic radio standards. These belong to the Short Range Wireless (SRW) technology, more suitable for short transmission distances such as home automation. Further advantages of the LPWAN are the lower energy consumption and the scalability of the network. A small “disadvantage” is that with LPWAN you can only send telegrams with low data rate, which is not relevant for IoT.
The LoRa-Alliance is a non-profit organisation with over 500 members. Since its foundation in 2015 it is the largest and fastest growing organisation in the technology sector. The goal of the Alliance is to standardize LPWAN worldwide and thereby increase the number of IoT installations.
Members include CISCO, GOOGLE Cloud, IBM, DEKRA, we as Minol ZENNER Connect GmbH and many more.
Especially for the members there are general meetings.
To use LoRa, a membership in the LoRa-Alliance is not necessary.
LoRaWAN® Technical Details
LoRaWAN® devices use generally allocated frequencies in Germany. For this reason it is possible that other devices transmit on the same frequency as LoRaWAN® devices and that telegrams are lost. However, regulations of the German Federal Network Agency ensure that frequencies cannot be permanently disturbed by individual devices (duty cycle of maximum 1 %). In the event of a telegram not being successfully transmitted and the associated failure to acknowledge receipt, the terminal device resends the information. For this purpose, LoRaWAN® devices use different frequency channels for transmission one after the other, which means that in case of a disturbance in one frequency range the subsequently transmitted telegrams can still be transmitted successfully. In addition, a protocol based on the ALOHA access method randomly varies the time of transmission so that two or more devices do not transmit several times in succession at the same time.
Yes, LoRaWAN® is a bidirectional radio system. The sending of telegrams via the gateway to the terminal device is called downlink. In the simplest example, downlinks are used to confirm to the terminal device that it has received the information it has sent. If this confirmation is not received, the mobile device takes over further send attempts.
Downlinks can also be used to make changes to the configuration of the mobile device. For example, it is possible to change the transmission interval. It is also possible to control actuators, e.g. opening or closing a valve.
Asynchronous packets are the event-driven transmission of information.
A suitable example for clarification is the parking sensor. To ensure that the current status of the parking space is available at all times, every change of status – e.g. the change from a free to an occupied parking space – is immediately transmitted as an asynchronous packet.
In addition to the asynchronous packets, information can also be transmitted automatically at fixed times – these transmissions are called synchronous packets. Using the example of the parking space sensor, for example, the automatic daily transmission of the current status has the advantage that even in the absence of a change of status it can be ensured that the device is active and functional.
ADR is the term “Adaptive Data Rate”. This is a mechanism that optimizes data rates and energy consumption. The data rate is adjusted by the LNS depending on the received signal strength of the telegrams already received by the terminal device. Whether the LNS recommendation to change the “spreading factor” is accepted by the terminal depends on the terminal itself.
The used data rates are in a range between 0.3 and 50 kbit/s. The data rate can be adjusted during operation to save battery power and to control the total network capacity (see ADR).
Behind “chirp spread spectrum” there is a modulation method which was originally developed for radar applications. It is based on the chirp pulse, a curved frequency pulse that changes frequency over a period of time but leaves the amplitude the same. A distinction is made between up-chirp, where the frequency increases towards the end, and down-chirp, where the frequency increases towards the end. The “chirp spread spectrum” uses the entire bandwidth for signal transmission.
The LoRa devices are divided into three classes A, B and C, which describe different requirements for communication from the gateway to the devices.
Devices in this class are particularly energy efficient – for this reason most battery operated devices are class A devices. Communication from the gateway to the terminal device (downlink) can only take place immediately after the terminal device has sent a message to the gateway (uplink). Depending on the transmission interval of the terminal device, this can result in longer delays between the initiation of a downlink and the actual transmission to the terminal device. All LoRaWAN® devices must support class A functionality.
In addition to the receive windows immediately after the own transmission, Class B devices open further receive windows at fixed times. To synchronize these additional receive time windows, the gateway sends so-called beacons. The shorter response times result in higher energy consumption of the end devices.
Devices of this class are in receive mode virtually uninterrupted – only while the end devices are transmitting is it not possible to receive downlinks. This is associated with increased energy consumption and therefore only makes sense if the device requires short response times to information sent by the gateway and usually has a fixed power connection.
The frequencies that can be used by LoRaWAN® devices for communication differ from region to region. The LoRa Alliance provides an overview of the frequencies to be used for LoRa, divided by country. In Germany, the frequencies generally allocated by the Federal Network Agency in the frequency band 863 – 870 MHz are used for short-range devices (SRD). This also results in restrictions on the maximum transmission strength and frequency. In the USA, for example, the band from 902 – 928 MHz is used, in China the band from 470 – 510 MHz.
The 863 – 870 MHz frequency band used in the EU is divided into 10 channels that can be used by equipment for communication. The terminal devices change the channel used for transmission between sending individual packets in order to ensure successful transmission even in the event of interference in individual frequency ranges.
A distinction is made here between indoor and outdoor devices. Conventional outdoor devices have a range of between 2 and 15 kilometres, depending on the nature of the environment. Experience shows that the range is greater in rural areas than in the city due to the many interfering signals and houses. Indoor devices, on the other hand, have a much lower range.
The spreading factor influences the transmission time of the data and thus the battery life and network capacity. The factor is between 7 and 12, whereby factor seven represents the shortest transmission time with the highest data rate. The higher the factor, the longer the transmission time and the lower the data rate. By changing the spreading factor, a more secure radio connection is ensured and the reception sensitivity is increased.
The transmission interval can be different from device to device. It depends on the users’ requirements, how often they need their data and the size of the built-in battery. Derived from this, transmission intervals from a few minutes to monthly can be implemented.
The radiation exposure from LoRaWAN® devices can generally be considered as non-critical. The following reasons are decisive:
The transmitting unit of the LoRaWAN® devices is always very little active in percentage terms, e.g. over one month. While mobile radio devices usually send and receive around the clock, LoRa devices send only 1.5 hours per year (with daily transmission of a telegram with SF12)
Compared to other radio systems, LoRaWAN® devices transmit with significantly lower transmission power. The maximum transmission power in Europe is 25 mW, which corresponds to 14 dBm.
Due to the high energy efficiency of LoRaWAN® devices, a battery life of two to 15 years is possible, depending on the application. Among other things, the transmission interval, the length of the telegrams and the capacity of the battery have an influence.
The transmission of LoRa telegrams is encrypted. In principle, message telegrams can be received by any gateway, but in order to understand and use the information contained in them it is necessary to know the keys.
Encryption is carried out using two 128-bit AES keys, each of which is unique for each end device:
Network Session Key (NwkSKey): Encryption between the end device and the LoRa Network Server – ensures message integrity by transmitting a consecutive data packet number in encrypted form.
Application Session Key (AppSKey): Encryption of the payload between the end device and the application server.
Depending on the activation procedure, the keys are written to the devices during production (ABP) or negotiated during the join process between the application server and the device (OTAA).
Up to 59 bytes of data can be transmitted with one LoRa telegram.
How many devices can be reliably received via a gateway depends on several factors. In principle, packets can be lost if several telegrams are transmitted simultaneously on the same channel. The probability of such an overlap is influenced not only by the number of devices but also by the length of the transmitted telegrams and the spreading factor with which the devices transmit. The shorter the devices transmit (favored by the small spreading factor and short telegram), the lower the probability of a collision. It also plays a role whether an acknowledgement of receipt is requested for the transmitted telegrams or not. An acknowledgement of receipt has the advantage that lost telegrams are repeated – but at the same time leads to further traffic. The regulation of the German Federal Network Agency regarding the maximum transmission strength also means that the number of devices within range of a gateway cannot become too large and thus also prevents collisions.
Tests have shown that a single gateway can receive up to 470,000 telegrams per day.