About

Why 1xBTS?

CDMA2000 was a major cellular technology — Verizon and Sprint in the United States, SK Telecom in South Korea, KDDI (au) in Japan, China Telecom, and Reliance in India — but it never spread as widely as GSM. As carriers shut their networks down, the phones that ran on them were left with nowhere to connect.

1xBTS exists to change that. It's a CDMA2000 1x and EV-DO Rev 0/Rev A network — base station, radio access, HRPD access network, and core — that runs on a software-defined radio and commodity hardware, so a CDMA handset can register, call, text, and move data again.


It's built in the open and still moving. Voice, SMS, 1x packet data, and EV-DO data work today on real devices; there's plenty left to do on production hardening, but it already does what it set out to do.

What can it do?

✓Voice — QCELP and EVRC calls, with a SIP gateway to the PSTN
✓Messaging — mobile-to-mobile and network SMS
✓1x packet data — IP over SO7/SO33, PPP/RLP, and F-SCH downlink
✓EV-DO (HRPD) — Rev 0/Rev A UATI sessions and dedicated high-rate data
✓Provisioning — over-the-air *228 (NAM, PRL, MMS)
✓Air interface — SR1, RC1/RC2/RC3, 800 Hz power control
✓Architecture — the full 1x node split over standard reference points
✓Management — a web dashboard over gRPC

Common questions

Do I need a SIM card?
Often not. On many CDMA2000 phones, identity lives in the NAM (MIN/IMSI, ESN/MEID) on the device, set over the air with *228 or in the service menu — no SIM involved. Newer handsets, though, use a SIM (R-UIM/CSIM) and may require one for proper operation.
Can two phones call and text each other?
Yes. Two handsets registered on the network place voice calls and exchange SMS directly, mobile to mobile.
Can it reach real phone numbers?
With the SIP voice gateway it bridges to a PSTN/SIP trunk in both directions — outbound from a handset and inbound to it. Without a trunk, it's a self-contained network.
Will my phone work?
Many CDMA2000 1x handsets do. We've tested a range of them (see Hardware), and most 1x phones should work — behavior varies by model.
What's the range?
It runs a single low-power cell — short range, for a bench or a room, not wide-area coverage. Reach depends on your SDR, gain, and antenna.
Does it do 3G, EV-DO, or LTE?
EV-DO, yes — also written 1xEV-DO, and called HRPD in the 3GPP2 specifications. Alongside 1x (voice, SMS, packet data), 1xBTS runs it as a dedicated data carrier with Rev 0 and Rev A support. Rev A has tested at about 2.6 Mbps downlink and 1.4 Mbps uplink as data throughput after protocol overhead. See the EV-DO guide. UMTS and LTE aren't supported.
How is it different from OpenBTS or Osmocom?
Those target GSM and UMTS. 1xBTS is CDMA2000 1x specifically — the full radio access network and core, in Rust, driven by an SDR.
Is it production-ready?
Not yet. The core works on real handsets — voice, SMS, 1x packet data, and EV-DO data — but it's actively developed, with work left on production hardening.
Is it open source? How do I help?
Yes — Apache-2.0. The code, issues, and discussions are on GitHub, and there's #1xbts on Libera.Chat IRC.