LoRaWAN Gateway Carrier-Grade Radio Coexistence Best-Practices
LoRaWAN Free license and radio performance challenges
LoRa end-devices and carrier-grade LoRaWAN gateways communicate in unlicensed Industrial Scientific and Medical (ISM) frequency bands. This is a benefit for public and private IoT network operators and customers as they do not need to buy a license to operate a network. They also do not pay any associated usage fees to government to transmit data on IoT networks running on these frequencies. They can thus benefit from an enterprise-grade reliable IoT network.
The most common LoRaWAN frequency bands used worldwide are the following:
- 433 MHz (EMEA),
- 868-870 MHz (EMEA),
- 902-915 MHz (North America), and
- 915-928 MHz (LATAM, APAC).
However, unlicensed ISM frequencies are country specific. If some geographies share similar frequency bands, some countries may have specific usage. This could be related to the locally allowed frequencies but also on among criteria like time on air, duty cycle, effective isotropic radiated power (EIRP), for example.
LoRaWAN gateway radio performance and colocalization
In a defined area, the number of available sites offering the best radio coverage and performance is obviously limited. Site sharing is often favored in urban and suburban areas where there is a shortage of available sites or complex radio planning requirements. These highly sought-after sites are, most of the time, already used by other radio systems. This can be cellular base stations (GSM/UMTS/LTE) or high-power transmitters like TV emitters, radio broadcasting equipment’s (FM radio, TV), radars, satellite stations, military applications, etc.. One of the most critical high-power transmitters for LoRaWAN gateways colocalization are Digital Terrestrial TV Transmitters.
In many use cases, if a LoRaWAN gateway is therefore colocalized with those emitters, a special care must be taken during the installation. This is key to increase interference resistance, eliminate noise and improve radio performance. When deploying LoRaWAN gateway, especially in urban areas, it is necessary to consider all the radio systems in the near environment to design a highly available and extremely reliable network.
Excellent Radio Performance combines carrier-class LoRaWAN gateway and colocalized industrial-grade installation
First, select a tier-one vendor offering truly carrier-grade equipment
When deploying a carrier-grade Low Power Wide Area Network (LPWAN), as any radiocommunications network, the choice of the LoRa gateway installation site is critical. This is a key decision to optimize radio performance and interference resistance. However, before assessing how to colocalize a LoRa gateway with other radio transmitters, the selection of an industrial-grade LoRaWAN gateway vendor also matters as equipment performance, availability and reliability are prerequisites.
The expertise for LoRa gateway radio performance design could IoT network operators help to understand the potential performance issues during deployment and later operations. This would also be very helpful to understand and anticipate the relevant installations options to prevent interferences and improve noise elimination. To grant highly reliable radio performance and network availability for LoRa gateway, the following key parameters need to be considered:
- The architecture of the LoRa gateway front-end,
- The band-pass of the RF filters,
- The minimum signal to noise (SNR) ratio required,
- The radio sensitivity performance,
- The out-of-band rejection,
- The in-band rejection,
- The receiver linearity,
- The transmit intermodulation performance, and
- The maximum input power.
Industry-leading and purpose-built LoRaWAN gateway are designed on strict requirements and optimized for the best radio performance. This industrial-grade conception ensures network reliability and security, high throughput and on-time message delivery, wherever the LoRa gateway is located on the field.
Kerlink teams have strong expertise in designing and manufacturing IP-67 rated industrial-grade outdoor and enterprise-grade indoor IoT gateway. These products offer steady performance, high reliability, high availability and ease of use, at lower cost. Our teams also have a strong knowledge and expertise in carrier-grade LoRa gateway radio coexistence and interference mitigation scenarios, for best-in-class performance. Two other key domains of expertise, LoRaWAN gateway carrier-grade lightning protection and radio coverage optiomization, will also be further detailed in later to come white papers.
Second, set-up appropriate carrier-grade protection for colocalized installations
When scrutinizing existing radio bands, we can see that some LTE bands and LoRaWAN bands are very close to each other. The guard band is sometimes very limited (few MHz) or even reduce to null. Thus, when colocalizing a carrier-grade LoRaWAN gateway with high power transmitters and / or wide area LTE (or 2G to 4G) Base Stations or Medium Range LTE Base Stations, the usage of cavity filter is highly recommended.
As massive IoT is gaining traction, more and more sensors and IoT devices are deployed for various use cases, generating an increasing amount od data. In this context, the colocalization of LPWAN gateways on a shared site will increase significantly, in already dense radio environment. The usage of a cavity filter may consequently fix a lot of potential issues and mitigate blocker effects, intermodulation effects and moreover transmit intermodulation.
Industrial-grade cavity filter devices now have very low cost compared to the expected QoS improvement and intervention costs cuts they can generate. Going on site to upgrade an installation is extremely costly compared to the limited upfront investment that would be required to start with a real carrier-class protection. This protection would then grant low ongoing operating costs and maximum network uptime and availability.
Third, take care of installation distances for carrier-grade equipment
However, cavity filters do not fix all the issues potentialy met. In particular, out-of-band spurious generated by high power transmitters and / or Wide Area LTE Base Stations or Medium Range LTE Base Stations may cause desensitization of the LoRaWAN gateway. A mitigation scenario is to grant a minimum vertical and horizontal distance between readio equipment on the installation site. This type of physical separation would concretely lower the risks of desensitization of the LoRa gateway.
A new LPWAN gateway could also be installed close to an already existing LoRaWAN gateway but also any other LPWAN gateway sharing the same unlicensed band. The issue when colocalizing LPWAN gateways on the same site or on a close site is because they use the same bands and, most of the time, the same channels. Therefore, in this case, RF filtering cannot be used to avoid interferences, unless gateways are specifically configured in receive mode only (no transmission). Issues are sometimes observed when a LoRaWAN gateway transmits on a dedicated channel, causing desensitization of the other gateways, as in-band blockers. To mitigate these potential issues, colocalization of LoRaWAN gateways imposes several constraints on the gateway installation and design described in the document.
A carrier-grade site selection and installation provides to the operator several benefits such as a better coverage area, a better QoS, and secure installation. This expertise is also part of a overall cutting-edge network strategy and grants unprecedented quality and resistance. Facing bad radio performances may jeopardize IoT use case deployment, reliability and business case to a broader extend. Thus, adopting from start best practices for a network industrial-grade design is paramount. This approach only can grant a highly available, robust and reliable network on the run. This upfront limited investement in LoRa gateway accessorization is also a good choice to control and reduce ongoing operating costs.
This first Kerlink Technical White Paper provides analysis, calculations, examples and recommendations to understand the radio interference phenomenon which could cause desensitization of a LoRaWAN gateway because of the colocalized transmitters.