HALO Signal Characteristics in Noise
HALO is designed specifically for noisy, interference-prone environments like urban areas or industrial sites. Here’s how signals generally fare, and what factors matter:
Signal Characteristics
- HALO uses Chirp Spread Spectrum (CSS), which spreads the signal over a wide frequency range.
- This makes it very resistant to narrowband noise and interference (for example, from Wi-Fi, Bluetooth, or machinery).
- Even with a poor Signal-to-Noise Ratio (SNR), HALO can often decode correctly. HALO receivers can demodulate signals up to –20 dB below the noise floor.
Spreading Factor (SF) Tradeoff
- Higher SF (SF7–SF12) → stronger resilience to noise, longer range, but slower data rate.
- Lower SF → faster transmission, less resilience.
- In a noisy environment, HALO often adapts upward to higher SFs to maintain reliability.
Frequency Band
- HALO typically operates in unlicensed ISM bands (e.g., 868 MHz EU, 915 MHz US).
- These bands are shared with many other devices, creating potential for congestion and collisions.
- CSS means HALO can tolerate interference better than most protocols in these bands.
Types of Noise and Their Impact
- Narrowband Interference → HALO usually ignores it because the chirps cover a much wider band.
- Wideband Noise (industrial RF noise, poorly shielded equipment) → raises the noise floor and reduces effective range.
- Other HALO devices (same frequency, same SF) → collisions can occur since HALO uses pure ALOHA (no listen-before-talk).
Practical Performance in Noisy Environments
- Urban / industrial areas: HALO still works well, though range may shrink (e.g., from 10 km rural → 1–2 km urban).
- Factories with lots of motors / VFDs: Possible reduced reliability if noise is broadband, but mitigated by good gateway placement.
- Dense HALO networks: Collisions become a bigger problem than environmental noise. Using multiple channels and gateways helps.
Mitigation Strategies
- Use multiple gateways → improves spatial diversity and reduces packet loss.
- Adaptive Data Rate (ADR) → allows each device to choose optimal SF and power.
- Antenna placement → higher, away from metal walls/machinery, improves SNR.
- Channel diversity → devices hop frequencies to avoid repeated collisions/interference.
- External filtering or shielding → in very noisy RF environments, bandpass filters or better antennas can help.