Remote Radio

cdma-radiod runs next to an SDR and serves it over the network. On another machine, a radio config of kind network points at it. The mobile station and the BTS both treat that config like a directly attached radio.

Use it when the radio is attached to a different machine from the software: a laptop at the antenna and a build host elsewhere, a radio on a Mac with the mobile in a Linux VM, or one host feeding several test setups in turn.

Run the server

cdma-radiod builds with all four SDR backends by default:

cargo build --release -p cdma-radiod
cdma-radiod --radio config/radio_uhd_b210_native.json

--radio takes any standard radio config. Device, antenna, gain and stream settings all stay on the server. Listener settings come from config/radiod_network.json:

{
  "listen": "0.0.0.0:50710",
  "data_listen": "0.0.0.0:50711",
  "tx_sample_rate_hz": 4915200
}

Key	Default	Description
`listen`	`0.0.0.0:50710`	Control connection (gRPC)
`data_listen`	`0.0.0.0:50711`	Sample stream
`tx_sample_rate_hz`	`4915200`	Transmit sample rate. The default suits the mobile station and a single-carrier 1x BTS

Trusted networks only. cdma-radiod does not authenticate clients. Anyone who can reach it can retune the radio and transmit. Run it on a private network, or set listen and data_listen to 127.0.0.1 in config/radiod_network.local.json when the client runs on the same machine.

If the client disappears (it crashes, or the network drops), radiod stops transmitting by itself once samples stop arriving.

Point a client at it

config/radio_network.json:

{
  "kind": "network",
  "addr": "radio-host:50710",
  "data_host": "radio-host",
  "samples_per_packet": 2200,
  "tx_transport": "tcp",
  "rx_enabled": true
}

Key	Default	Description
`addr`	required	radiod’s control address
`data_host`	host of `addr`	radiod’s host for the sample stream
`samples_per_packet`	`350`	Samples per network packet. The default fits a standard 1500-byte MTU. Up to `2200` (the shipped example) cuts the packet rate on networks with jumbo frames
`tx_transport`	`udp`	`udp` has the least overhead, and a lost packet becomes a short silent gap on air. `tcp` never loses transmit samples
`rx_enabled`	`true`	Stream received samples back to the client
`rx_gain_db`, `rx_antenna`	radiod’s config	Override receive settings from the client
`tx_sample_delay`	radiod’s radio config	Transmit timing compensation for the mobile station. The client uses the server’s value unless this overrides it

Then use it like any other radio:

# Mobile station
cdma-ms console --radio config/radio_network.json --prl my-network.prl

# BTS, built without any local SDR drivers
cargo run --release -p cdma-nib --no-default-features --features network-backend -- \
    --config-dir config \
    --radio-config config/radio_network.json

Network requirements

Bandwidth. Receive runs at about 160 Mbps and transmit at up to the same, so use wired gigabit Ethernet. Wi-Fi is not enough.
Reachability. radiod sends received samples back to the address the client’s sample stream comes from. A NAT between client and server can break this, so keep both on the same network.
One client at a time. A new client takes over the radio from the previous one. Sample rates, antenna and bandwidth are fixed once a client connects, so restart radiod to change them.