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ttsou, 02/19/2016 10:47 PM

= OsmoTRX =

OsmoTRX is a software-defined radio transceiver that implements the Layer 1 physical layer of a BTS comprising the following 3GPP specifications: * TS 05.01 "Physical layer on the radio path" * TS 05.02 "Multiplexing and Multiple Access on the Radio Path" * TS 05.04 "Modulation" * TS 05.10 "Radio subsystem synchronization"

OsmoTRX is based on the OpenBTS transceiver, but setup to operate independently with the purpose of using with non-OpenBTS software and projects. Currently there are numerous features contained in OsmoTRX that extend the functionality of the OpenBTS transceiver. These features include enhanced support for embedded platforms - notably ARM - and dual channel diversity support for the Fairwaves UmTRX. Most of these features will eventually be merged into mainline OpenBTS, but primary development will occur on OsmoTRX.

Features =Intel SSE Support=
  • SSE3
  • SSE4.1

On Intel processors, OsmoTRX makes heavy use of the Streaming SIMD Extensions (SSE) instruction set. Accelerated operations include pulse shape filtering, resampling, sequence correlation, and many other signal processing operations. SSE3 is the minimum requirement for accelerated use. SSE3 is present in the majority of Intel processors since later versions of the Pentium 4 architecture and is also present on low power Atom processors.

ARM NEON Support
  • NEON
  • NEON-VFPv4

Dual Channel (UmTRX only)

Two dual channel modes are available: standard dual channel mode and diversity. In standard dual channel mode, each RF
path of the dual channel device - currently only UmTRX - supports a different ARFCN. Each path operates independently a
nd operates similarly to two separate devices. GSM channel capacity in this mode is doubled.

Dual Channel Diversity (UmTRX only)

Diversity mode is similar to the standard dual channel mode except each antenna supports both ARFCN channels. In this case, the receiver sample bandwidth is widened to handle both ARFCN's and subsequently converted and demultiplexed into separate sample streams. Each GSM receive path is fed dual signals, where antenna selection diversity is performed by t
aking the stronger signal on a burst-by-burst basis. The limitations are that ARFCN spacing is restricted by the receiv
e sampling bandwith (currently 400 kHz) and increased CPU utilization.

Low Phase Error Modulator

Hardware support Ettus Research
Embedded Platform Support

OsmoTRX has been tested on the following embedded platforms.

Platform Processor FPU
BeagleBoard-xM ARM Cortex-A8 NEON
ArndaleBoard ARM Cortex-A15 NEON-VFPv4
RaspberryPi ARMv6k VFP
Shuttle PC Intel Atom D2550 SSE3
Ettus E100 ARM Cortex-A8 NEON
Status GPRS support Source code

The source code is available from (module osmo-trx).

Public read-only access is available via
git clone git://
You can browse it via cgit:

Configuration and Build

The only package dependency is the Universal Hardware Driver (UHD).

$ ./configure
$ make
$ sudo make install


$ osmo-trx -h
linux; GNU C++ version 4.8.1 20130603 (Red Hat 4.8.1-1); Boost_105300; UHD_003.005.004-140-gfb32ed16

-h This text
-a UHD device args
-i IP address of GSM core
-p Base port number
-d Enable dual channel diversity receiver
-x Enable external 10 MHz reference
-s Samples-per-symbol (1 or 4)
-c Number of ARFCN channels (default=1)

$ osmo-trx -a "addr="
linux; GNU C++ version 4.8.1 20130603 (Red Hat 4.8.1-1); Boost_105300; UHD_003.004.000-b14cde5

Config Settings
Log Level............... INFO
Device args............. addr=
TRX Base Port........... 5700
TRX Address.............
Channels................ 1
Samples-per-Symbol...... 4
External Reference...... Disabled
Diversity............... Disabled

-- Opening a UmTRX device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
-- Setting UmTRX 4 SPS
-- Transceiver active with 1 channel(s)


OsmoTRX is currently developed and maintained by Thomas Tsou. The original code is derived from the OpenBTS project, which was developed by David Burgess and Harvind Samra at Range Networks.

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