Configuration

1xBTS uses a per-node config directory plus an optional radio-config override:

cargo run --release -p cdma-nib -- --config-dir config --radio-config config/radio_bladerf_micro2.json

The default config directory contains bts.json, bsc.json, msc.json, pcf.json, pdsn.json, hlr.json, smsc.json, and management.json.

Node Configuration

1xbts-web uses MANAGEMENT_GRPC_ADDRESS for the facade endpoint and falls back to BSC_GRPC_ADDRESS for older local setups. MSC-owned call actions and SMS submission are served by the MSC management endpoint from msc.json; SMS coordination flows from MSC to BSC over A1 ADDS messages.

Local Overrides

The configs in config/ are shared defaults. To customize one for your own setup without touching the checked-in file, drop a sibling <name>.local.json next to it:

config/bts.json          # shared default (in git)
config/bts.local.json    # your overrides (gitignored)

At load time the BTS reads the base file, merges your local file on top, and validates the result. Your local file only needs the fields you’re changing — anything you omit keeps the value from the base.

For example, to switch to a different CDMA channel and bump TX gain without touching anything else in bts.json:

{
  "channel": {
    "band_class": "bc0",
    "band_subclass": 0,
    "cdma_channel": 283
  },
  "radio": {
    "tx_gain_db": 60
  }
}

The BTS derives both TX and RX center frequencies from channel (via C.S0057-F band-class formulas). To force a non-standard tune for lab/loopback work, set runtime.tx_freq_hz_override and/or the radio backend’s rx_freq_hz_override.

The same convention works for every config in config/: bts.json, bsc.json, msc.json, pcf.json, pdsn.json, hlr.json, smsc.json, management.json, voice-gw.json, and the radio profiles (e.g. radio_bladerf_micro2.local.json).

Merge behavior

• Nested objects are merged field by field; fields you don’t set keep the base value.
• Arrays in your local file replace the base array (they’re not appended).
• Setting a field to null removes it, falling back to the struct default.

BTS Runtime

{
  "channel": {
    "band_class": "bc0",
    "band_subclass": 0,
    "cdma_channel": 384
  },
  "runtime": {
    "spreading_rate": "sr1",
    "chip_rate_hz": 1228800,
    "tx_sample_rate_hz": 4915200,
    "tx_digital_backoff": 0.5
  }
}

channel is the single source of truth for RF tuning. The BTS supports all 23 band classes defined in C.S0057-F (bc0–bc22, except bc17 and bc22 which are “Not specified” in the spec). The band_subclass selects which spectrum-allocation profile is broadcast in handoff messages. The default (BC0 / subclass 0 / N=384) maps to 881.520 MHz TX / 836.520 MHz RX. See the Configuration Reference for the full per-band formula table.

Downlink Channels

Extended System Parameters in bts.json carry the advertised MCC and IMSI_11_12 defaults as decimal digit strings, for example "mcc": "310" and "imsi_11_12": "55". The BTS encodes those strings into the C.S0005-E bit fields, and the BSC uses the same overhead values to reconstruct a complete class-0 registration IMSI when the mobile only sends the short IMSI fields on the access channel.

BSC / MSC / Packet Parameters

For SO33 packet-data downlink, bsc.traffic_assignment.enable_f_sch enables F-SCH and f_sch_rate_bps selects 19200, 38400, 76800, or 153600.

Access Channel

Radio Configuration

Hardware-specific SDR parameters.

UHD (USRP B200/B210)

{
  "kind": "uhd",
  "device": "type=b200,num_recv_frames=1024,num_send_frames=1024",
  "channel": 0,
  "antenna": "TX/RX",
  "tx_gain_db": 65.0,
  "rx_antenna": "RX2",
  "rx_gain_db": 50.0,
  "rx_sample_rate_hz": 4915200,
  "rx_bandwidth_hz": 5000000,
  "rx_sample_delay": 50
}

LimeSDR (Native)

{
  "kind": "lime",
  "device": "",
  "channel": 0,
  "tx_antenna": "BAND1",
  "tx_gain_db": 60,
  "rx_antenna": "LNAW",
  "rx_gain_db": 20,
  "rx_sample_rate_hz": 4915200,
  "rx_bandwidth_hz": 5000000,
  "rx_sample_delay": 97
}

rx_sample_delay compensates for LimeSDR-specific timing offsets in the receive path.

bladeRF (Native)

{
  "kind": "blade_rf",
  "device": "",
  "channel": 0,
  "fpga_path": null,
  "tx_antenna": "TXA",
  "rx_antenna": "B_BALANCED",
  "tx_gain_db": 50,
  "rx_gain_db": 40,
  "rx_sample_rate_hz": 4915200,
  "rx_bandwidth_hz": 2500000,
  "rx_reference_dbm": null,
  "rx_sample_delay": 0,
  "rx_batch_pcgs": 2,
  "num_buffers": 16,
  "buffer_size": 8192,
  "num_transfers": 8,
  "stream_timeout_ms": 3500
}

fpga_path: null uses libbladeRF’s host auto-load path, typically ~/.config/Nuand/bladeRF/hostedxA4.rbf. Set fpga_path to an explicit .rbf file if you do not want host auto-load. tx_antenna and rx_antenna select bladeRF RF ports; the current Micro 2.0 example uses TXA and B_BALANCED.

Environment Variables

Next Steps

• First Registration — Start the BTS and register a handset
• Configuration Reference — Full parameter reference