Setting up a private wireless network using Doodle Labs Mesh Rider Radios means selecting the appropriate frequency band, channel, and channel width to optimize network performance.
In this post, we’ll examine how to choose the best settings for your network utilizing Mesh Rider Radios operating in unlicensed frequencies, comparing the 915 MHz and 2.4 GHz bands, and exploring the use of narrowband channels to optimize for specific applications. Note that Mesh Rider also supports frequencies outside these bands, and the same principles apply.
Understanding OFDM
At the heart of Mesh Rider’s outstanding performance is OFDM (Orthogonal Frequency Division Multiplexing), which splits the available spectrum into multiple subcarriers. This method increases throughput, improves resistance to interference, and allows for more flexible frequency and channel-width options.
When operating in the 915 MHz or 2.4 GHz ISM band, selecting the right channel width (ranging from 3 MHz to 26 MHz) and frequency band is crucial to meet your network’s unique coverage, interference, and data rate requirements.
Choosing 915 MHz or 2.4 GHz ISM Band
The 915 MHz ISM band is commonly used for long-range communication systems such as IoT, rural broadband, or industrial deployments. This band spans from 902 MHz to 928 MHz in the Americas and supports both wide and narrow channel widths.
- Range: Signals at 915 MHz travel over longer distances compared to higher frequency bands. This makes it ideal for outdoor, long-range deployments, covering large areas with fewer access points.
- Penetration: The 915 MHz band offers excellent penetration through obstacles such as walls, buildings, and trees, making it particularly useful in industrial environments or areas with dense physical barriers.
- Interference: The 915 MHz ISM band is typically less congested than 2.4 GHz, reducing interference from consumer devices. However, there may still be interference from Zigbee, LoRa, or other low-power wireless devices that also operate in this band.
The worldwide 2.4 - 2.5 GHz ISM band is widely used for consumer Wi-Fi networks and general wireless communication.
- Range: While 2.4 GHz offers shorter range compared to 915 MHz, it provides a good balance between coverage and speed, especially in smaller or indoor environments.
- Penetration: The 2.4 GHz band has decent penetration capabilities, although not as strong as 915 MHz due to weaker propagation and materials absorption.
- Interference: 2.4 GHz is a crowded band, as it is shared with many consumer electronics like microwaves, Bluetooth devices, and Wi-Fi networks. This can lead to interference and degraded performance in urban and densely populated areas.
Optimizing Channel Selection
Choosing the optimal channel within your selected band can reduce interference and enhance performance.
- Spectrum and Wi-Fi Analyzers - Mesh Rider OS has a built in spectrum scanning function that can help identify the best channels by scanning for interference and determining which channels are least congested. Access it in the GUI at Advanced Settings > Network Configuration > Wireless > Spectrum Scan
- Avoid Overlapping Channels: In the 2.4 GHz band, when using 20 MHz bandwidth, select non-overlapping channels (1, 6, or 11) to reduce interference with WIFI devices. In the 915 MHz band, narrow channels of 3 MHz help to reduce interference by taking up less spectrum.
- Adjust for Your Environment: In rural or large industrial settings, using narrow channels in the 915 MHz band can ensure better long-range coverage with less interference. In urban areas, the 2.4 GHz band may be more congested but offers higher speeds, so choosing the least congested channels is critical.
Selecting the Right Channel Width
An important aspect of configuring your network is selecting the appropriate channel width. With Mesh Rider, the available channel widths range from 3 MHz to 26 MHz. Here's some background on how to determine the best channel width for your network.
Regardless of the bandwidth used (3 MHz, 10 MHz, 26 MHz, etc.), the total radiated power is capped at 30 dBm in unlicensed frequencies. OFDM splits the available bandwidth into multiple subcarriers. The Power Spectral Density (PSD) (Watts per Hz of bandwidth) will decrease as the bandwidth increases. For example, if you're using a 10 MHz channel, the total transmit power is spread across 32 subcarriers. If you switch to a 20 MHz channel, the same 30 dBm is now spread across 64 subcarriers, halving the power per subcarrier. As the signal’s strength per Hz (or per subcarrier) decreases, the signal can be more susceptible to noise and reduce range/coverage if other factors (e.g., modulation schemes, coding rates) remain unchanged.
Thus, narrowing the channel bandwidth can increase range and improve resilience to constant co-channel interference. However, this comes at the expense of reduced data throughput and a weaker defense against occasional interference. The illustration below shows a simplified example: our original message is distorted by noise, which includes both random background fluctuations and intermittent interference spikes.
Image Credit: Doodle Labs
With a narrow bandwidth, we transmit over this noisy environment by integrating each data symbol's power over a longer period, effectively smoothing out the noise. With a wide bandwidth, we can communicate around intermittent interference, but each data symbol is integrated over a shorter time, making it more vulnerable to persistent background noise.
Example: Choosing 3 MHz or 20 MHz Channel Width
3 MHz Channel Width
- Range and Coverage: A 3 MHz channel provides excellent range, especially in the 915 MHz band. Narrow channels concentrate the energy of the signal, extending its reach, making this ideal for long-range applications.
- Low Interference: Narrow channels like 3 MHz greatly reduce the potential for interference, since they use only a small portion of the available spectrum. This makes them ideal in environments where you want to avoid overlap with other networks or devices.
- Lower Data Rates: The tradeoff with narrower channels is reduced data throughput. 3 MHz channels are suitable for applications where low data rates are acceptable, such as basic telemetry, control systems, or long-range monitoring, but they are insufficient for high-bandwidth activities like video streaming.
20 MHz Channel Width
- Range and Stability: A 20 MHz channel provides a balance between range and data throughput. It is commonly used in both the 915 MHz and 2.4 GHz bands. This width is ideal for standard Wi-Fi use in the 2.4 GHz band or for moderate-range deployments in the 915 MHz band.
- Interference: In crowded environments, 20 MHz channels can experience interference, especially in the 2.4 GHz band, where there are only 3 non-overlapping channels (1, 6, and 11). In the 915 MHz band, interference is less of a concern, but may still occur from other narrowband systems.
- Use Case: 20 MHz channels are a good choice for general network use, balancing range, stability, and data rates. They are especially useful in environments with moderate interference or for devices that need more bandwidth than narrowband channels provide.
Conclusion: Optimizing Your Mesh Rider Network
When configuring a Mesh Rider network, the choice between 915 MHz and 2.4 GHz, along with the selection of channel widths from 3 MHz to 26 MHz, will determine the performance and reliability of your network. Here's a recap:
- 915 MHz Band: Choose 915 MHz for long-range, low-data-rate applications. Utilize narrowband channels (3 MHz) for maximum range.
- 2.4 GHz Band: Use 2.4 GHz for higher data rate applications in smaller or more confined areas. 10 MHz is generally preferred, but 20 MHz can be used for higher speeds in less congested environments.
- Doodle labs Throughput Estimation tool allows you to experiment with these settings as described here. Check it out!