= 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. For additional performance information, please see the benchmarks section. SSE usage is detected and configured automatically at build time.

'''ARM NEON Support'''

• NEON
• NEON-VFPv4

OsmoTRX runs on a variety of ARM processors with and without NEON coprocessors. Like SSE on Intel processors, NEON provides acceleration with SIMD vectorized instructions. Tested popular architectures include ARM11 (Raspberry Pi), Cortex-A8 (!BeagleBoard), and Cortex-A15 (!ArndaleBoard). These platforms include no NEON coprocessor, standard NEON, and NEON-VFPv4 respectively. The latter NEON variation, VFPv4, provides additional fused-multiply-accumulate (FMA) instructions useful for many DSP operations. For additional performance information, please see the benchmarks section. NEON optimization must be used enabled at built time.

'''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 taking the stronger signal on a burst-by-burst basis. The limitations are increased CPU utilization and that ARFCN spacing is restricted (currently at 400 kHz) by the receiver sampling bandwidth. Setting the ARFCN spacing beyond the sampling limit will disable the diversity path.

'''Low Phase Error Modulator'''

The default GSM downlink signal is configured for low distortion using a linearized GMSK modulator. The implementation is based on a two pulse Laurent approximation of continuous phase modulated (CPM) signals. On capable devices, the signal measures with very low phase error and passes industry spectrum mask requirements.

Phase Error (Ettus Research N200)

[[Image(http://tsou.cc/gsm/osmo-trx-phase75.gif)]]

Frequency Spectrum (Ettus Research N200)

[[Image(http://tsou.cc/gsm/osmo-trx-spectrum75.gif)]]

Hardware support Fairwaves

UmTRX

Ettus Research

	USRP1
	USRP2
	B100
	B110
	B200
	B210
	N200
	N210
	E100
	E110

Embedded Platform Support

OsmoTRX has been tested on the following embedded platforms.

	'''Platform'''		'''SoC'''		'''Processor'''		'''SIMD/FPU'''
	!ArndaleBoard		Samsung Exynos 5250		ARM Cortex-A15		NEON-VFPv4
	!BeagleBoard-xM		Texas Instruments OMAP3		ARM Cortex-A8		NEON
	Ettus E100		Texas Instruments OMAP3		ARM Cortex-A8		NEON
	Shuttle PC		NA		Intel Atom D2550		SSE3
	Raspberry Pi		Broadcom BCM2835		ARM11		VFP

Mailing List

For development purposes, OsmoTRX is discussed on both OpenBTS and OpenBSC mailing lists at openbts-discuss@lists.sourceforge.net and openbsc@lists.osmocom.org respectively. Please direct questions to the list appropriate for the GSM stack being used.

Subscription information is available at [https://lists.sourceforge.net/lists/listinfo/openbts-discuss] and [http://lists.osmocom.org/mailman/listinfo/openbsc/].

GPRS support

OsmoTRX supports GPRS through OsmoBTS. For GPRS support with OpenBTS, please use the transceiver supplied with OpenBTS.

Source code

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

Public read-only access is available via
git clone git://git.osmocom.org/osmo-trx
You can browse it via cgit: http://cgit.osmocom.org/cgit/osmo-trx/

Configuration and Build

The only package dependency is the Universal Hardware Driver (UHD), which is available from Ettus Research or Fairwaves depending on the device. Please note that the UHD implementation must match hardware (i.e. Ettus Research UHD for USRP devices and Fairwaves UHD with UmTRX). The one device that does not use the UHD driver is the USRP1, which is supported through the legacy libusrp driver provided in GNU Radio 3.4.2.

'''Intel Platforms (All)'''

Intel SSE support is automatically detected on Intel x86 platforms. No user intervention is necessary. {{{
$ ./configure
...
checking whether mmx is supported... yes
checking whether sse is supported... yes
checking whether sse2 is supported... yes
checking whether sse3 is supported... yes
checking whether ssse3 is supported... yes
checking whether sse4.1 is supported... yes
checking whether sse4.2 is supported... yes
...
}}}

'''ARM Platforms with NEON'''

Many popular ARM development boards fall under this category including PandaBoard, and Ettus E100 USRP. NEON support must be manually enabled. {{{
$ ./configure --with-neon
}}}

'''ARM Platforms with NEON-VFPv4'''

Currently very few development platforms support this instruction set, which is seen mainly in high end smartphones and tablets. Available development boards are !ArndaleBoard and ODROID-XU. NEON-VFPv4 support is manually enabled. {{{
$ ./configure --with-neon-vfpv4
}}}

'''ARM Platforms without NEON'''

This configuration mainly targets the Raspberry Pi. ARM platforms without NEON vector units are almost always very slow processors, and generally not very suitable for running OsmoTRX. Running OsmoTRX on a Raspberry Pi, however, is possible along with limited TCH (voice) channel support. Currently this configuration requires minor code changes.

Coming soon.

'''Build and Install'''

After configuration, installation is simple.

{{{
$ make
$ sudo make install
}}}

Running

OsmoTRX can be configured with a variety of options on the command line.

{{{
$ 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

Options:
-h This text
-a UHD device args
-l Logging level (EMERG, ALERT, CRT, ERR, WARNING, NOTICE, INFO, DEBUG)
-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=192.168.10.2"
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=192.168.10.2
TRX Base Port........... 5700
TRX Address............. 127.0.0.1
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)
}}}

Benchmarks

Selected benchmark results are provided below. All tests run on a single core only.

'''Intel Haswell (i7 4770K 3.5 GHz)'''

{{{
--- Floating point to integer conversions
-- Testing 40000 iterations of 3120 values
- Measuring conversion time
- Elapsed time base... 0.065508 secs
- Validating SIMD conversion results... PASS
- Measuring conversion time
- Elapsed time SIMD ... 0.011424 secs
- Speedup... 5.734244
}}}

{{{
[+] Testing: GSM TCH/AFS 7.95 (recursive, flushed, punctured)
[.] Input length : ret = 165 exp = 165 -> OK
[.] Output length : ret = 448 exp = 448 -> OK
[.] Pre computed vector checks:
[..] Encoding: OK
[..] Decoding base:
[..] Decoding SIMD:
[..] Code N 3
[..] Code K 7
OK
[.] Random vector checks:
[.] Testing baseline:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 1.435066 secs
[.] Rate................................ 3.121808 Mbps
[.] Testing SIMD:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 0.073524 secs
[.] Rate................................ 60.932485 Mbps
[.] Speedup............................. 19.518334
}}}

'''Intel Atom (D2500 1.86 GHz)''' {{{
--- Floating point to integer conversions
-- Testing 40000 iterations of 3120 values
- Measuring conversion time
- Elapsed time base... 1.147449 secs
- Validating SSE conversion results... PASS
- Measuring conversion time
- Elapsed time SSE ... 0.347838 secs
- Quotient... 3.298803
}}}

{{{
[+] Testing: GSM TCH/AFS 7.95 (recursive, flushed, punctured)
[.] Input length : ret = 165 exp = 165 -> OK
[.] Output length : ret = 448 exp = 448 -> OK
[.] Pre computed vector checks:
[..] Encoding: OK
[..] Decoding base:
[..] Decoding SIMD:
[..] Code N 3
[..] Code K 7
OK
[.] Random vector checks:
[.] Testing baseline:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 11.822688 secs
[.] Rate................................ 0.378932 Mbps
[.] Testing SIMD:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 0.550423 secs
[.] Rate................................ 8.139195 Mbps
[.] Speedup............................. 21.479277
}}}

'''!ArndaleBoard (ARM Cortex-A15 1.7 GHz)''' {{{
--- Floating point to integer conversions
-- Testing 40000 iterations of 3120 values
- Measuring conversion time
- Elapsed time base... 0.384097 secs
- Validating SSE conversion results... PASS
- Measuring conversion time
- Elapsed time SSE ... 0.100877 secs
- Quotient... 3.807578
}}}

{{{
[+] Testing: GSM TCH/AFS 7.95 (recursive, flushed, punctured)
[.] Input length : ret = 165 exp = 165 -> OK
[.] Output length : ret = 448 exp = 448 -> OK
[.] Pre computed vector checks:
[..] Encoding: OK
[..] Decoding base:
[..] Decoding SIMD:
[..] Code N 3
[..] Code K 7
OK
[.] Random vector checks:
[.] Testing baseline:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 5.371288 secs
[.] Rate................................ 0.834064 Mbps
[.] Testing SIMD:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 1.016621 secs
[.] Rate................................ 4.406755 Mbps
[.] Speedup............................. 5.283471
}}}

'''!BeagleBoard-xM (ARM Cortex-A8 800 MHz)''' {{{
--- Floating point to integer conversions
-- Testing 40000 iterations of 3120 values
- Measuring conversion time
- Elapsed time base... 6.292542 secs
- Validating SIMD conversion results... PASS
- Measuring conversion time
- Elapsed time SIMD ... 0.839081 secs
- Quotient... 7.499326
}}}

{{{
[+] Testing: GSM TCH/AFS 7.95 (recursive, flushed, punctured)
[.] Input length : ret = 165 exp = 165 -> OK
[.] Output length : ret = 448 exp = 448 -> OK
[.] Pre computed vector checks:
[..] Encoding: OK
[..] Decoding base:
[..] Decoding SIMD:
[..] Code N 3
[..] Code K 7
OK
[.] Random vector checks:
[.] Testing baseline:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 21.963257 secs
[.] Rate................................ 0.203977 Mbps
[.] Testing SIMD:
[..] Encoding / Decoding 10000 cycles:
[.] Elapsed time........................ 3.083282 secs
[.] Rate................................ 1.452997 Mbps
[.] Speedup............................. 7.123337
}}}

Authors

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