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Lora Technologies: Long Range & Low Power
Dr. Mohamed Abdelghader Morsi Mahmoud* & Dr. Amin Babikir A.
Alnabi*
*Head of Future Trends Section, Telecommunication and Post Regulatory Authority (TPRA), Khartoum, Sudan.
**Associate Proff, Alneelain University, Khartoum, Sudan.
ABSTRACT:
LoRa™ is low power wide area wireless network (LPWAN) protocol for Internet of Things (IoTs) applications. LPWAN has been enabling technology of large scale wireless sensor networks (WSNs). Effective cost, long range and energy efficiency of LPWANs make them most suitable candidates for smart city applications. These technologies offer novel communication paradigm to address discrete IoT's applications. LoRa is a recently proposed LPWAN technology based on spread spectrum technique with a wider band. LoRa uses the entire channel bandwidth to broadcast a signal which makes it resistant to channel noise, long term relative frequency, Doppler effects and fading. This paper focuses on the Lora WAN, advantages and disadvantages, Features, LoRa Modules, Frequency Bands and Lora WAN™-RF-Modules and Sensors.
Key words: LPWAN, (WSNs), LoRaWAN
1.1 What is Lora?
LoRa technology was developed by a company called Semtech and it is a new wireless protocol designed specifically for long-range, low-power communications.
LoRa stands for Long Range Radio and is mainly targeted for M2M and IoT
Networks. This technology will enable public or multi-tenant networks to connect a number of applications running on the same network.
LoRa Alliance was formed to standardize LPWAN (Low Power Wide Area Networks) for IoT and is a non-profit association which features membership from a number of key market shareholders such as CISCO, activity, Microchip, IBM, STMicro, SEMTECH, Orange mobile and many more. This alliance is key to providing interoperability among multiple nationwide networks.
Each LoRa gateway has the ability to handle up to millions of nodes. The signals can span a significant distance, which means that there are fewer infrastructures required, making constructing a network much cheaper and faster to implement.
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1.2 Lora WAN
Introduction:
• The full form of LoRa is Long Range Radio.
• The technical specification is published by LoRa Alliance.
• It is low power wide area network which has become popular to due to low power consumption and long coverage range.
• Supports 902 to 928 MHz in US, 863 to 870 MHz in EU and 779 to 787 MHz in China.
1.3 Advantages of Lora WAN
Following are the advantages of Lora WAN:
➨It uses 868 MHz/ 915 MHz ISM bands which is available worldwide.
➨It has very wide coverage range about 5 km in urban areas and 15 km in suburban areas.
➨It consumes less power and hence battery will last for longer duration.
➨Single LoRa Gateway device is designed to take care of 1000s of end devices or nodes.
➨It is easy to deploy due to its simple architecture as shown in the figure-1.
➨It uses Adaptive Data Rate technique to vary output data rate/Rf output of end devices. This
helps in maximizing battery life as well as overall capacity of the LoRaWAN network. The data rate can be varied from 0.3 kbps to 27 Kbps for 125 KHz bandwidth.
➨It is widely used for M2M/IoT applications.
➨The physical layer uses robust CSS modulation. CSS stands for Chirp Spread Spectrum. It
uses 6 SF (spreading factors) from SF 7 to 12. This delivers orthogonal transmissions at different data rates. Moreover it provides processing gain and hence transmitter output power can be reduced with same RF link budget and hence will increase battery life.
➨It uses LoRa modulation which has constant envelope modulation similar to FSK
modulation type and hence available PA (power amplifier) stages having low cost and low power with high efficiency can be used.
1.4 Disadvantages of Lora WAN
Following are the disadvantages of Lora WAN:
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➨Lora WAN network size is limited based on parameter called as duty cycle. It is defined as
percentage of time during which the channel can be occupied. This parameter arises from the regulation as key limiting factor for traffic served in the Lora WAN network.
➨It is not ideal candidate to be used for real time applications requiring lower latency and
bounded jitter requirements.
1.5 Features
The following table showcases some of the key features of the LoRa protocol such as range, modulation and capacity.
Specification LoRa Feature
Range 2-5Km Urban (1.24-3.1 mi),
15Km suburban (9.3 mi)
Frequency ISM 868/915 MHz
Standard IEEE 802.15.4g
Modulation Spread spectrum modulation type based
on FM pulses which vary.
Capacity One LoRa gateway takes thousands of
nodes
Battery Long battery life
LoRa Physical layer Frequency, power, modulation and
signaling between nodes and gateways
1.6 LoRa Modules
Semtech Corporation is the leader in LoRa wireless technology and as such has introduced a number of LoRa RF modules for the market. In particular, the SX127x family of RF transceivers for the IoT/M2M markets.
These RF modules operated between 860-1000 MHz and 137-960MHz. Semtech also offer evaluation and testing devices at 860MHz band.
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These are +20dBm LoRa packet radios that have a special radio modulation that is not compatible with the RFM69s but can go much farther. They can easily go 2 Km (1.24 mi) line of sight using simple wire antennas, or up to 20Km (12.4 mi) with directional antennas and settings tweaking’s.
Packet radio with ready-to-go Arduino libraries
Uses the license-free ISM band: "European ISM" @ 868MHz or "American ISM" @ 915MHz
Use a simple wire antenna or spot for uFL or SMA radio connector SX1276 LoRa® based module with SPI interface
+5 to +20 dBm up to 100 mW Power Output Capability (power output selectable in software)
~100mA peak during +20dBm transmit, ~30mA during active radio listening. Range of approx. 2Km (1.24 mi), depending on obstructions, frequency, antenna
and power output
Each radio comes with some header, a 3.3V voltage regulator and level shifter that can handle 3-5V DC power and logic so you can use it with 3V or 5V devices. Some soldering is required to attach the header. You will need to cut and solder on a small piece of wire (any solid or stranded core is fine) in order to create your antenna. Optionally you can pick up a uFL or SMA edge-mount connector and attach an external duck.
Microchip, also being a key partner in the LoRa Alliance have also introduced a number of LoRa modules for the IoT market. The module is a small form factor with up to 14 GPIO pins for connecting sensors and actuators whilst taking up very little space.
"The RN2483 module is a revolutionary end-node IoT solution for the new LoRa technology network, enabling extremely long-range, bidirectional communication with significant battery life," said Steve Caldwell, vice president of Microchip's Wireless Products Division. "As a founding member of the LoRa Alliance, we are working to ensure our modules are compatible with all partner gateways and back -end network service providers."
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With its scalability, robust communication, mobility and the ability to operate in harsh outdoor environments, the RN2483 is well suited for a broad range of low-data-rate wireless monitoring and control designs.
1.7 Frequency Bands
LoRaWAN operates in unlicensed radio spectrum. This means that anyone can use the radio frequencies without having to pay million dollar fees for transmission rights. It is similar to WiFi, which uses the 2.4GHz and 5GHz ISM bands worldwide. Anyone is allowed to set up WiFi routers and transmit WiFi signals without the need for a license or permit.
Lora WAN uses lower radio frequencies with a longer range. The fact that frequencies have a longer range also comes with more restrictions that are often country-specific. This poses a challenge for Lora WAN that tries to be as uniform as possible in all different regions of the world. As a result, Lora WAN is specified for a number of bands for these regions. These bands are similar enough to support a region-agnostic protocol, but have a number of consequences for the implementation of the backend systems.
1.7.1 European 863-870 MHz and 433 MHz bands
Of the available ISM frequency bands, Lora WAN uses the 863-870 MHz and 433 MHz bands. The former, which is usually referred to as the 868 MHz band, is currently supported by The Things Network, whereas the latter will be implemented later.
The Lora WAN specification defines 3 common 125 kHz channels for the 868 MHz band (868.10, 868.30 and 868.50 MHz) that must be supported by all devices and networks, and that all gateways should always be receiving on. These three channels form a common set of channels that all devices can use to join with a network. During this join procedure, the network can instruct the devices to add additional channels to its channel set. These channels are used for both uplink and downlink messages.
1.7.2 Duty Cycle
The European frequency regulations impose specific duty-cycles on devices for each sub-band. These apply to each device that transmits on a certain frequency, so both gateways and devices have to respect these cycles. Most channels used by Lora WAN have a duty-cycle as low as 1% or even 0.1%. As a result, the network should be smart in scheduling messages on gateways that are less busy or on channels that have a higher duty-cycle.
1.7.3 US 902-928 MHz
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1.7.4 Australia 915-928 MHz
The specification of the Australian 915-928 MHz band is practically the same as the US 902-928 MHz, except that its uplink frequencies are on higher frequencies than in the US band. Its downlink channels are the same as in the US 902-928 MHz band.
1.7.5 China 779-787 MHz and 470-510 MHz
The Chinese 779-787 MHz band behaves similar to the European bands. The 779-787 MHz band also has three common 125 kHz channels (779.5, 779.7 and 779.9 MHz). The Chinese 470-510 MHz band behaves similar to the US bands. There are 96 uplink channels and 48 downlink channels. In some regions, a subset of these channels is used by China Electric Power and can therefore not be used for Lora WAN.
1.8 Lora WAN™-RF-Modules and Sensors
This ever growing collection of frequently asked questions around our family of LoRa and Lora WAN modules and sensors shall help prospects and costumers to get a deeper understanding of the advantages and pitfalls of Lora WAN based IoT systems.
In fact did we control the two meters wing-span drone fly back exactly when
It reached 100km because there was nearly no visible analog video image at all. By the way was the drone real time remote controlled by or LoRa-based link. That is a total other category then just sending a temperature every other hour. If one data packet is lost nothing bad happens. Our LoRa-link has to be reliable and needs to
Provide real time performance 100% of the time and every millisecond over and over again. So there is still more range left for IoT applications. Link budget ouf our FMLR Lora WAN modems is high enough to get 1000 km (620 miles) line-of-sight range. For instance shows our wireless simulation tool that two high flying air planes (11000m) easily would reach each other if one is over Zürich / Switzerland and the other over Rome / Italy.
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1.8.1 Options to increase range
One option is having a high gain directional antenna at the gateway pointing into the direction of the sensor node. If the nodes are all distributed into one direction seen from the gateway then a single directional antenna is the right solution. Tested designs are Yagi, Helical, Panel or LogN. If your sensors are distributed in the full
360 degrees range around the gateway sitting in the middle then a combination of 3 sector antennas is the best solution. Every sector antenna overlooks a range of 120 degrees.
Another very important step to get ultra long ranges like 50-100km and more is to have the antennas installed at a high mast. Best locations for antenna masts are on roofs of high
buildings or even better on a nearby hill or mountain. In the end radio waves in the UHF
range are traveling comparable to visible light. That means that
They can only reach about 10-15% behind the visible horizon. One should never forget that our earths shape is spherical not flat. To get the idea just have a look at some GSM or TV-Broadcast antennas in your area. They use about the same frequencies and underlay the same physical principles.
1.9 Summary
It is clear that LoRa wireless technology is going to play a big role in the IoT market. Interconnecting devices to create smart cities, industrial and commercial solutions, whils t reducing the limitations from other wireless technologies such as power and other overheads.
References:
i. V. Atanasovski and A. Leon-Garcia, Future Access Enablers for Ubiquitous and Intelligent Infrastructures. Springer, 2015. [Online]. Available: http://link.springer.com/10.1007/978-3-319-27072-2.
ii. ―Sigfox,‖ accessed Jan 10, 2017. [Online]. Available: https://www.sigfox.com/
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iv. U. Raza, P. Kulkarni, and M. Sooriyabandara, ―Low Power Wide
Area Networks: A Survey,‖ pp. 1–15, jun 2016. [Online]. Available:http://arxiv.org/abs/1606.07360
v. Daniel Lundell ,Ad-hoc network possibilities inside LoRaWAN, June 21, 2017.
vi. Congduc PHAM1, Building low-cost gateways and devices for open LoRa IoT test-beds, LIUPPA, University of Pau, France.
