Radio Configurations

1xBTS implements CDMA2000 1x RC1, RC2, and RC3 plus an EV-DO / HRPD Rev 0/Rev A data carrier. Additional 1x RCs are planned.

RC1 — IS-95A

Parameter	Value
Spreading Rate	SR1 (1.2288 Mcps)
Forward Modulation	BPSK
Reverse Modulation	64-ary Walsh (offset QPSK)
Convolutional Code	Rate 1/2, K=9
Data Rates (forward)	9600, 4800, 2400, 1200 bps
Data Rates (reverse)	9600, 4800, 2400, 1200 bps
Walsh Length	64
Frame Duration	20 ms
Interleaving	Block, 20 ms
Service Options	SO1/SO3/SO68/SO70 (voice), SO7 (data)

RC2 carries QCELP 13K calls at higher full-rate capacity than RC1. Enable RC2 in both supported_for_rcs and supported_rev_rcs in bsc.json; QCELP 13K calls select RC2 automatically when the handset supports it.

Parameter	Value
Spreading Rate	SR1 (1.2288 Mcps)
Forward Modulation	BPSK
Reverse Modulation	64-ary Walsh (offset QPSK)
Convolutional Code	Rate 1/2, K=9
Data Rates	14400, 7200, 3600, 1800 bps
Walsh Length	64
Frame Duration	20 ms
Reverse Pilot	No
Service Options	SO32768 (QCELP 13K voice)

RC3 — CDMA2000 1x

Parameter	Value
Spreading Rate	SR1 (1.2288 Mcps)
Forward Modulation	QPSK
Reverse Modulation	Pilot + data (HPSK)
Convolutional Code	Rate 1/4, K=9
Data Rates (forward)	9600, 4800, 2700, 1500 bps
Data Rates (reverse)	9600, 4800, 2700, 1500 bps
Walsh Length	Variable (up to 128)
Frame Duration	20 ms
Reverse Pilot	Yes (gated)
F-SCH	Configurable supplemental downlink: 19.2, 38.4, 76.8, or 153.6 kbps
Power Control	Per-PCG (800 Hz)
Service Options	SO3/SO68/SO70 (voice), SO33 (data)

RC Comparison

Feature	RC1	RC2	RC3
Forward modulation	BPSK	BPSK	QPSK
Code rate	1/2	1/2	1/4
Max FCH rate	9.6 kbps	14.4 kbps	9.6 kbps
Typical voice use	TIA-96 / EVRC	QCELP 13K	EVRC
Supplemental	No	No	F-SCH to 153.6 kbps downlink
Reverse pilot	No	No	Yes (gated)
Per-PCG power control	No	No	Yes

EV-DO / HRPD Rev 0/Rev A

EV-DO is a separate 1.25 MHz data carrier, not another 1x radio configuration. It uses HRPD pilot, MAC, Control, Access, Forward Traffic, and Reverse Traffic channels and is enabled by bts.json: evdo.

Parameter	Value
Carrier	Dedicated HRPD / 1xEV-DO Rev 0/Rev A carrier
Spreading Rate	SR1 (1.2288 Mcps)
Slot Duration	2048 chips, about 1.667 ms
Forward Scheduling	DRC-driven Forward Traffic packets
Session Identity	UATI assigned by the HRPD AN
Packet Path	Default Packet Application stream to A8/A9, PCF, A10/A11, and PDSN
Rev A support	Negotiates Rev A personality with capable devices
Confirmed Downlink	Rev 0 about 1.4 Mbps; Rev A about 2.6 Mbps data throughput after protocol overhead
Confirmed Uplink	Rev 0 up to 153.6 kbps; Rev A about 1.4 Mbps data throughput after protocol overhead

EV-DO is enabled from bts.json, not by selecting an HRPD-specific radio profile. Use the normal UHD, bladeRF, LimeSDR, or SoapySDR radio config for your hardware and set evdo.enabled, evdo.channel, and optionally evdo.mode in the BTS config.

The runtime derives the RF profile from the carrier mode:

Mode	Derived RF behavior
1x only	4x chip-rate sample clock, 1.5 MHz RF bandwidth
1x + HRPD composite	Smallest 4x, 8x, or 16x span that fits the configured 1x and HRPD channels
HRPD only	Supported EV-DO-only deployment with a 4x chip-rate sample clock and 1.5 MHz RF bandwidth

For EV-DO-only deployments, channels 589, 630, and 770 are good starting points.

Planned