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.

What you need

Item	Notes
Ground Agent SBC	Pi 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.
Antennas	Primary 5 GHz omni on UNII-3 (channel 149 or 153) for the drone link, 2.4 GHz omni on the mesh radio (channel 1 by default). Keep 30 cm minimum between antennas on the same chassis.
OLED + 4 buttons	For the Accept window during pairing
Power, case, cabling	Same shape as a relay

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.

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. Setup webapp: Ground Station -> Role -> 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.

Verify

Open the setup webapp Ground Station page or the ground-station panel in Mission Control. The role should show receiver, mesh should be up, and the relay list should be empty until a relay joins. The mesh is up. There are no peers yet because no relay has joined.

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. Setup webapp: Ground Station -> Pair relay -> Accept for 60 seconds. 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 on the OLED, setup webapp, and the ground-station panel in Mission Control. To approve a pending relay: OLED: highlight the relay with B2/B3, press B1 to approve. Setup webapp or GCS: approve the pending relay by 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

What runs on the box

After role=receiver:

Unit	What it does
`ados-batman.service`	batman-adv on the second USB dongle. Same module as a relay uses.
`ados-wfb-receiver.service`	Runs `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.service`	Republishes 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.

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.

Cloud uplink election

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 Mesh tab in the ground-station panel, 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.

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: the Distributed RX tab renders a RelayCard for each paired relay with fragment counts, plus a CombinedStreamStats card showing FEC-repaired fragments and output kbps. The Mesh tab shows MeshHealthCard, MeshNeighborsTable, MeshGatewaysTable.
Setup webapp: Ground Station and System pages show role, mesh health, neighbors, gateways, relays, and combined stream stats.
REST API: /api/v1/ground-station/wfb/receiver/relays and /api/v1/ground-station/wfb/receiver/combined.

Decommissioning a relay

To revoke a relay so it can no longer rejoin without re-pairing: GCS: Distributed RX tab -> RelayCard -> Revoke. Type the relay’s device id to confirm. Setup webapp: Ground Station -> Relays -> Revoke. 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.

Where to next

Relay Mode - set up the relays.
Local Mesh (batman-adv) - the carrier underneath.
Field Tap-to-Pair - the pairing protocol.

Getting Started

Connecting Your Devices

Browser Dashboard

Distributed Receive & Mesh

Operations

Receiver Mode

Receiver Mode

What you need

Install

Switch the role to receiver

Verify

Open the Accept window for pairing

What runs on the box

FEC combine

Cloud uplink election

Where to monitor

Decommissioning a relay

Where to next

​Receiver Mode

​What you need

​Install

​Switch the role to receiver

​Verify

​Open the Accept window for pairing

​What runs on the box

​FEC combine

​Cloud uplink election

​Where to monitor

​Decommissioning a relay

​Where to next

Receiver Mode

What you need

Install

Switch the role to receiver

Verify

Open the Accept window for pairing

What runs on the box

FEC combine

Cloud uplink election

Where to monitor

Decommissioning a relay

Where to next