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LoRa

The idea behind this test is to measure the output power of a single frequency carrier and measure the potential spurs around this frequency.This test is required for the EN300.220 ETSI validation.

On most of the Semtech FSK transmitters, the simplest way to perform this test is to set the Frequency Deviation of a standard modulated FSK signal to 0 Hz.

The first step is to set the frequency of the continuous wave, as a second step, you will need to set the PA Output (RFO or PA Boost depending on your chipset and implementation). The third step is to set the frequency deviation to 0 .To finish, you need to set the radio in continuous transmit mode. Using a spectrum analyser, you should observe a clean carrier at the frequency entered.

Alternatively, for the SX127x, it is also possible to digitally create a continuous waveform using the internal radio modulator.This method is slightly more obscure as it is using some undocumented registers of the radio.To simplify the work, we have implemented example code for the SX1272 and the SX1276 which are given with the software release for the chipsets.

The examples are located here

There are changes required at the host interface and specifications for transmitting data in a LoRa system that require changes to the host system software, but with fully integrated modems available in the eco-system, and their well-defined host controller interface, it is actually quite seamless.

This is possible, but there would be a need to convert an existing 802.15.4 or other mesh protocol to use the modulation format. Because of some of LoRa's features such as longer transmission time which increases link budget, single-hop is usually the best choice.

The SX1301 device is the baseband signal processor for LoRa gateways. It takes 32 MHz, 1-bit I/Q digital baseband samples as an input. It is generally paired with two SX1257 front end digitizers, though it can be used with other forms of digital RF. This is often done with the 8 x SX1301 gateway architecture Senet uses in its network deployment.

It is possible to transmit and receive the LoRa modulation at many frequencies between 150 MHz and 1 GHz, such as 169 MHz, 433 MHz, etc. even in the licensed spectrum. However, most of the LoRa devices from Semtech have gaps in the sub-GHz band where they can’t transmit or receive. The Semtech gateway architecture is designed to operate only at 850 MHz to 1 GHz, although it could be easily adapted for other frequencies.

SX1272 has three programmable LoRa bandwidth settings: 500 kHz, 250 kHz and 125 kHz. It covers bands from 850-1 GHz.

SX1276 has bandwidths from 500 kHz to 7.8 kHz, and covers 150 MHz bands, 433 MHz, and 850-1 GHZ.

LoRa is a modulation format and the associated family of chips are from Semtech.

SIGFOX is a company that uses narrowband D-BPSK modulation to do wide area IoT networking.

NWave is a company that does some very similar things to SIGFOX using the Weightless standard.

Other ultra-narrowband companies work with a broader family of transceiver chips, but LoRa is available mostly from Semtech, and more recently from ST Microelectronics.

Semtech’s spread-spectrum modulation is well adapted for mobile applications, being insensitive to Doppler shift, and it also enables GPS-less geo-location, two areas where any narrow-band technology would struggle.

  • A device's uplink can be received by two networks simultaneously
  • The device doesn't even know that it is roaming

  • For passive roaming we need to use different network session keys for uplinks and downlinks:
    • LoRa V 1.1 implements a new dual NettSkey key derivation.
    • The scheme reverts back to 1.0 if the server does not support it.

Version 1 of Semtech’s solver requires approximately 1.2kB of storage per device. 

Yes. The core function is not reliant on storage and is architected to be able to scale within a cloud or on-site computing platform.

LoRa transmissions are almost unaffected by vehicle speeds due to the type of modulation used.

LoRa is one of the most robust low power transmissions with respect to moving objects and does not suffer the kind of Doppler issues that limit ultra-narrow-band transmissions to very slow speed. LoRa can happily accommodate normal vehicular speeds.

With respect to location, as frequency diversity (read multiple transmissions on different frequencies) is a powerful tool in reducing the uncertainty this is not so easy with high-speed moving objects. With a moving object algorithms that analyse the speed and direction of movement and other things like ‘is it tracking a road’ can be used. Semtech’s first release does not include moving sensor optimisation.

There are already GPS based sensors available in the LoRa catalog. There is currently a lot of activity within the ecosystem combining sensors with gyros, sniffers and other technology that will open up a whole range of possibilities for accurate location determination. It is currently too early to demonstrate these with Semtech’s in-house system however, it is expected that within 2016 some of these will start to appear on the market.

Yes, LoRa technology can potentially apply to any frequency band, although its spread-spectrum nature makes it more relevant when at least a few MHz of spectrum is available.Currently, the use of LoRa is limited to the bands of frequency proposed in the SX1276 device. Our next generation devices will implement continuous coverage from VHF to 1 GHz.

Antenna diversity has been tested in the field. Mathematically, one would expect a 3dB gain in link budget with two antennas vs. a single one. The important effect with antenna diversity is that when one antenna is in a deep fade, the other can sometimes been seen to report a 10-12dB gain in signal-to-noise ratio. The uncertainty of the time-stamping in the gateway is significantly improved as signal-to-noise ratio rises. The uncertainty of the time-stamping rapidly rises as the signal approaches the extent of the sensitivity. Therefore, when a gateway is close to the maximum range, or simply in a deep fade caused by strong multipath the antenna diversity can make all the difference between presenting a usable time-stamp and one that is simple thrown away. Statistically the field test data show that increasing antenna diversity form one to two reduces the average uncertainty by 20%. In this test, both antennae were vertical 5dBi omni-directional spaced 1 meter apart horizontally. See the graph below for further details: 

 

Tx Power: this should be done with a power-meter or a spectrum analyzer (SA). If using the latter, make sure that the RBW (Resolution Band Width) is made large enough (typically 1MHz for a LoRa BW of 125kHz) to integrate the whole power during CSS modulation. Ensure that the transmitter is set to Tx Continuous mode for this test.

  • Channel masks should be checked with a SA, according to the latest EN 300-220.
  • Spurious emissions and harmonics should be checked as with any other RF transmitter, also in accordance with the European norm.
  • Sensitivity measurement should be performed with a Packet Error Rate (PER) test, as opposed to Bit Error Rate (BER) test, because of the nature of the LoRa modem. At present, none of the instrumentation vendors supports LoRa modulation natively (unlike Wi-Fi or BT for instance). Therefore, we need to use an Arbitrary Waveform Generator (ARB) to perform this test. Semtech supports Rohde &Schwarz's (R&S) SMBV100A ARB, and can provide pre-calculated frame in .wv format in order to perform tests.

Out of the 50 billion predicted nodes to be connected to the Internet by 2020 fewer than 10% are predicted to use cellular technology. Telecommunications companies will need long range, high capacity systems to consolidate the fragmented battery operated wireless market for sensor networks, smart cities, smart metering, security systems, smart home, and industrial control.

With our LoRa RF platform, we have developed a 2-way wireless solution that complements M2M cellular or WiFi infrastructure, and provides a low-cost way to connect battery operated and mobile devices to either the network infrastructure or end point.

To visit Semtech's LoRa website click here.

LoRa is a wireless technology that has been developed to enable the Internet of Things using unique low data rate communication to be made over long distances by sensors and actuators. As LoRa technology is able to provide a wide area network capability, it is often referred to as LoRaWAN.

A LoRa network consists of several crucial elements to build an Internet of Things solution:

End points:  The endpoints are the elements of the LoRa network where the sensing or control is undertaken. They are normally remotely located.

LoRa gateway:  The gateway, also referred to as Base Station or concentrator, receives the communications from the LoRa endpoints and then transfers them onto the backhaul system. This part of the LoRa network can be Ethernet, cellular or any other telecommunications link wired or wireless. The gateways are connected to the network server using standard IP connections. On this way the data uses a standard protocol, but can be connected to any telecommunications network, whether public or private. In view of the similarity of a LoRa network to that of a cellular one, LoRa gateways may often be co-located with a cellular base station. In this way they are able to use spare capacity on the backhaul network.

Network server:  The LoRa network server manages the network and provides OSS, BSS and billing functions. The network server acts to eliminate duplicate packets, schedules acknowledgement, and adapts data rates. In view of the way in which it can be deployed and connected, makes it very easy to deply a LoRa network.

IoT Application:  applications connected to the network server can control the actions of the endpoints or collect /send data - the LoRa network being the transparent, secure and scalable connectivity layer.

Yes, LoRais IPv6 and 6LoWPAN compatible. Actility (a LoRa partner) and other partners enabled 6LoWPAN on top of LoRaWAN.

The LoRa modulation itself is a PHY that can be used in all network topologies. A mesh network extends the range of the network but comes at the cost of reduced network capacity, synchronization overhead, and reduced battery lifetime due to synchronization and hops. With the increased link budget and range capability of LoRa, there is no need for a mesh network architecture to extend the range so a star architecture was chosen for LoRaWAN to optimize the network capacity, battery lifetime, and easy installation.