Installing Adaptive Link

How Adaptive-Link Works

Wireless communication can transmit data at high speeds over short distances with a strong signal, or slowly but over longer distances with a weaker signal.

OpenIPC allows you to choose one fixed link speed and video bitrate. Default:

• Bitrate: 4 Mbps
• Channel Width: 20 MHz
• MCS: 1
• FEC: 8/12
• Guard Interval: long

This is a “universal” profile — moderate quality and average range.

Adaptive-Link solves this by automatically selecting the best link and video profile based on signal quality (RSSI and SNR).

Strong signal = high speed and quality
Weak signal = long-range profile and lower bitrate

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How It Works

• On the Ground Station, alink_gs monitors RSSI and SNR, calculates a final “score” (1000–2000), and sends it to the drone.
• On the drone, alink_drone receives the score and selects the appropriate profile from /etc/txprofiles.conf.
• Profile transitions are controlled via /etc/alink.conf.

Example:

rssi_min = -80
rssi_max = -40
snr_min = 12
snr_max = 36

If RSSI = -60 and SNR = 20:

• RSSI score = 1500
• SNR score = 1333
• Final score (with 0.5/0.5 weights) ≈ 1416
• alink selects profile: 1051 - 1500

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Installation

Tip

An internet connection is required.

On Drone (OpenIPC)

cd /etc
curl -L -o alink_install.sh https://raw.githubusercontent.com/OpenIPC/adaptive-link/refs/heads/main/alink_install.sh
chmod +x alink_install.sh
./alink_install.sh drone install
reboot

Add to autostart:

/etc/rc.local >>  alink_drone &

On Ground Station (Radxa / Android / PC)

sudo curl -L -o alink_install.sh https://raw.githubusercontent.com/OpenIPC/adaptive-link/refs/heads/main/alink_install.sh
sudo chmod +x alink_install.sh
sudo ./alink_install.sh gs install

Config will be located at:

• /config/alink_gs.conf, or
• /home/radxa/alink_gs.conf, or
• /etc/alink_gs.conf

Tip

Alternative installation method using SCP to install Adaptive Link - here

Configuration Files

Profile Configuration: /etc/txprofiles.conf

Example configuration:

999 - 999 long 0 8 12 1999 10 30 0,0,0,0 20 -12
1000 - 1050 long 0 8 12 2000 10 30 0,0,0,0 20 -12
1051 - 1500 long 1 8 12 4000 10 25 0,0,0,0 20 -12
1501 - 1950 long 2 8 12 8000 10 20 12,6,6,12 20 -12
1951 - 2001 short 2 8 12 9000 10 20 12,6,6,12 20 -12

Tip

Safe TX profiles can be found here

Caution

Set the transmission power levels in /etc/txprofiles.conf carefully. The default is 30, which is safe for most adapters but may be too low for some. Adjust the power accordingly to ensure optimal performance.

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Parameter TX profile

Parameter	Description
Range	Score range where this profile applies
GI (Guard Interval)	short: higher speed, less protection long: more reliable at long range
MCS (Modulation and Coding Scheme)	Lower value = lower speed, better stability Higher value = higher throughput, requires stronger signal
FEC (Forward Error Correction)	Example: 8/12 means 8 bits data, 4 bits for error correction Lower ratio = faster speed, less error protection
Bitrate	Video stream speed in bits per second Higher value = better quality, more bandwidth usage
GOP (Group of Pictures)	Determines how often keyframes appear Lower value = more I-frames, better recovery from packet loss
Pwr (Transmit Power)	Transmission power of the radio signal Higher power = longer range, more interference
roiQP (Region of Interest QP)	Prioritizes video quality in important parts of the frame Lower value = better quality in the ROI area
Bandwidth	Width of the radio channel in MHz Wider = higher speed, narrower = better range
qpDelta	Global video compression tuning Lower value = higher quality, less compression

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Behavior Configuration: /etc/alink.conf

Example configuration:

rssi_weight=0.3
snr_weight=0.7
fallback_ms=1000
hold_fallback_mode_s=3
min_between_changes_ms=150
hold_modes_down_s=4
hysteresis_percent=15

Parameter	Description
rssi_weight	Weight given to RSSI (Received Signal Strength Indicator) in link quality calculations. Value of 0.3 means RSSI contributes 30% to the overall link quality assessment.
snr_weight	Weight given to SNR (Signal-to-Noise Ratio) in link quality calculations. Value of 0.7 means SNR contributes 70% to the overall link quality assessment.
fallback_ms	Time in milliseconds (1000ms = 1 second) the system waits before activating fallback mode when signal deteriorates.
hold_fallback_mode_s	Duration in seconds (3s) the system remains in fallback mode even if signal improves, ensuring stability before switching back.
min_between_changes_ms	Minimum time in milliseconds (150ms) between transmission mode changes, preventing rapid fluctuations.
hold_modes_down_s	Time in seconds (4s) the system maintains lower transmission modes before attempting to increase quality/speed again.
hysteresis_percent	Percentage buffer (15%) required for a mode change, preventing minor signal fluctuations from causing unnecessary mode switches.

Troubleshooting

If the drone stays in long-range mode (profile 999):

• Check ground station transmitter power
• Verify antenna connections
• Review /etc/txprofiles.conf settings

If video quality is poor despite strong signal:

• Check bitrate settings in /etc/txprofiles.conf
• Ensure RSSI and SNR weights in /etc/alink.conf are set correctly

If the system frequently changes settings:

• Increase min_between_changes_ms value in /etc/alink.conf
• Increase hysteresis_percent value in /etc/alink.conf

Recommendations

• Don’t choose profiles with high bitrate if your system can’t handle the traffic
• Always tailor txprofiles.conf to your adapter — especially power levels
• Consider your specific use case when configuring profiles