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Receiver Mode

A receiver is the hub of a distributed-receive deployment. It listens to the drone with its own RTL8812EU, accepts forwarded fragments from every paired relay over the local mesh, runs WFB-ng’s native FEC combine across the merged stream, and republishes the clean video to the same downstream pipeline a single-node Ground Agent uses. There is exactly one receiver per deployment. Every other mesh node is a relay.

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What you need

ItemNotes
Ground Agent SBCPi 4B is the bench reference
RTL8812EU USB WiFi adapter (primary)Drone-facing radio. Same as a single-node setup.
Second RTL8812EU USB adapter (default mesh carrier)Same chip as the primary for inventory simplicity and matched 29 dBm TX power. Any 802.11s-capable USB WiFi dongle also works; MT7612U and MT7921AU are common alternatives when mainline kernel coverage is preferred on the mesh side.
Antennas5 GHz omni on each radio. Primary on UNII-3 (channel 149 or 153), mesh on UNII-1 (channel 36 or 40). Keep 30 cm minimum between antennas on the same chassis.
OLED + 4 buttonsFor the Accept window during pairing
Power, case, cablingSame shape as a relay

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Install

Same as any ground-station install. Mesh dependencies are always pulled on this profile; no flag is required. 
sudo ./install.sh
This installs batctl, avahi-daemon, wpasupplicant, creates /etc/ados/mesh/, and lays down the three role-gated systemd units. profile_detect scans for the second USB WiFi adapter at boot and sets mesh_capable: true in /etc/ados/profile.conf when present.

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Switch the role to receiver

Unlike relay, receiver does not require prior pairing. A fresh receiver can come up cold; it generates its own mesh identity (mesh_id and psk.key) on first boot of mesh_manager. OLED: Mesh menu -> Set role -> select receiver with B1/B2 -> confirm with B3. CLI: 
ados gs role set receiver
REST: 
curl -X PUT http://localhost:8080/api/v1/ground-station/role \
  -H "Content-Type: application/json" \
  -d '{"role": "receiver"}'
The transition masks the direct-mode ados-wfb-rx.service, masks ados-wfb-relay.service, unmasks ados-batman.service and ados-wfb-receiver.service, writes receiver to /etc/ados/mesh/role, and starts the mesh + aggregator units.

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Verify

ados gs role show
# current: receiver, configured: receiver, mesh_capable: true

ados gs mesh health
# up: true, peer_count: 0 (no relays paired yet)

curl http://localhost:8080/api/v1/ground-station/wfb/receiver/relays
# {"relays": []}
The mesh is up. There are no peers yet because no relay has joined.

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Open the Accept window for pairing

To accept a relay, the receiver must open a 60 second Accept window: OLED: Mesh menu -> Accept relay. The screen shows a countdown and an empty pending-relay list. CLI: 
ados gs mesh accept --window 60
REST: 
curl -X POST http://localhost:8080/api/v1/ground-station/pair/accept \
  -H "Content-Type: application/json" \
  -d '{"duration_s": 60}'
The receiver binds a UDP listener on bat0:5801. When a relay sends a join request over the mesh, it appears in the pending list (visible on the OLED, in ados gs mesh pending, and in the GCS Hardware tab’s PairingStatusCard). To approve a pending relay: OLED: highlight the relay with B2/B3, press B1 to approve. CLI: 
ados gs mesh approve <device_id>
REST: 
curl -X POST http://localhost:8080/api/v1/ground-station/pair/approve/<device_id>
The receiver assembles an invite bundle (mesh ID, mesh PSK, drone WFB key, receiver mDNS name + port), encrypts it with Curve25519 ECDH + ChaCha20-Poly1305 keyed off the relay’s ephemeral public key, and sends it back over UDP. The blob is sent twice 100 ms apart to survive a single dropped packet on the lossy mesh. Full pairing protocol details

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What runs on the box

After role=receiver:
UnitWhat it does
ados-batman.servicebatman-adv on the second USB dongle. Same module as a relay uses.
ados-wfb-receiver.serviceRuns wfb_rx -a <listen_port> (default port 5800). Accepts UDP forwards from relays. With accept_local_nic: true (default), also reads the local RTL8812EU directly.
ados-mediamtx-gs.serviceRepublishes the clean stream as WHEP. Unchanged from a single-node setup.
The receiver also publishes _ados-receiver._tcp on the mesh interface via mDNS so relays can resolve it without manual configuration.

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FEC combine

WFB-ng’s native Reed-Solomon FEC runs at the receiver. The WfbConfig defaults are fec_k = 8 (data fragments per block) and fec_n = 12 (total fragments per block, so 4 parity). This means the receiver can recover the original block as long as it has any 8 of the 12 fragments, regardless of which radio (local or any relay) saw which fragment. The combine stats land in /run/ados/wfb-receiver.json. Surface them via: 
curl http://localhost:8080/api/v1/ground-station/wfb/receiver/combined
Fields: fragments_after_dedup, fec_repaired, output_kbps, up. The receiver runs batman-adv in gw client mode by default. If any node on the mesh (a relay or the receiver itself) advertises a cloud gateway via gw server (because it has 4G, Ethernet, or a WiFi client connection), the receiver picks the best one by TQ and routes cloud-bound traffic over it. When a gateway dies, batman-adv evicts it and the receiver picks the next best automatically. No operator action needed. You can pin a specific gateway from the GCS Hardware tab’s Mesh sub-view, or: 
curl -X PUT http://localhost:8080/api/v1/ground-station/mesh/gateway_preference \
  -H "Content-Type: application/json" \
  -d '{"mode": "pinned", "pinned_mac": "AA:BB:CC:DD:EE:01"}'
Set mode: auto to release the pin.

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Where to monitor

  • OLED: the status header shows Rx<id> as the role badge. Mesh -> Neighbors lists every paired relay with TQ. The Accept window screen shows pending relays during pairing.
  • GCS Mission Control: Hardware tab -> Distributed RX renders a RelayCard for each paired relay with fragment counts, plus a CombinedStreamStats card showing FEC-repaired fragments and output kbps. Mesh tab shows MeshHealthCard, MeshNeighborsTable, MeshGatewaysTable.
  • CLI:
    • ados gs mesh health
    • ados gs mesh neighbors
    • ados gs mesh gateways
    • curl /api/v1/ground-station/wfb/receiver/relays
    • curl /api/v1/ground-station/wfb/receiver/combined

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Decommissioning a relay

To revoke a relay so it can no longer rejoin without re-pairing: GCS: Hardware tab -> Distributed RX -> RelayCard -> Revoke. Type the relay’s device id to confirm. CLI: 
ados gs mesh revoke <device_id>
The device id goes into /etc/ados/mesh/revocations.json (mode 0600). On any future pair attempt from this device, the receiver drops the join request silently and the GCS surfaces a relay_revoked toast.

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Where to next