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.