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authorNeels Hofmeyr <neels@hofmeyr.de>2018-11-27 18:36:29 +0100
committerNeels Hofmeyr <neels@hofmeyr.de>2018-11-27 18:36:29 +0100
commitd9a460dce97da62ec1a48757dec4999d14685c67 (patch)
treede10666ef63ad930c58c0c80e0b333ab49de3d92 /doc/manuals/chapters
parent1e2c0105e2aab1a5ac7ad46bd427a69b54b7641c (diff)
parentf570b4af62868bb3a3acab674ceeae73e5bdbe2b (diff)
Merge history from osmo-gsm-manuals.git
Diffstat (limited to 'doc/manuals/chapters')
-rw-r--r--doc/manuals/chapters/code-architecture.adoc141
-rw-r--r--doc/manuals/chapters/configuration.adoc85
-rw-r--r--doc/manuals/chapters/control.adoc12
-rw-r--r--doc/manuals/chapters/counters.adoc4
-rw-r--r--doc/manuals/chapters/counters_generated.adoc7
-rw-r--r--doc/manuals/chapters/overview.adoc62
-rw-r--r--doc/manuals/chapters/running.adoc19
-rw-r--r--doc/manuals/chapters/trx-architectures.adoc34
-rw-r--r--doc/manuals/chapters/trx-backends.adoc46
-rw-r--r--doc/manuals/chapters/trx-devices.adoc90
10 files changed, 500 insertions, 0 deletions
diff --git a/doc/manuals/chapters/code-architecture.adoc b/doc/manuals/chapters/code-architecture.adoc
new file mode 100644
index 0000000..18d0e3a
--- /dev/null
+++ b/doc/manuals/chapters/code-architecture.adoc
@@ -0,0 +1,141 @@
+[[code_architecture]]
+== Code Architecture
+
+[[fig-code-architecture-general]]
+.General overview of main OsmoTRX components
+[graphviz]
+----
+digraph hierarchy {
+node[shape=record,style=filled,fillcolor=gray95]
+edge[dir=back, arrowtail=empty]
+
+2[label = "{Transceiver|+ constructor()\l+ destructor()\l+ init()\l+ numChans()\l+ receiveFIFO()\l+ setSignalHandler()}"]
+3[label = "{RadioInterface|...}"]
+4[label = "{RadioInterfaceResamp|...}"]
+5[label = "{RadioInterfaceMulti|...}"]
+6[label = "{RadioDevice|...}"]
+7[label = "{UHDDevice|...}"]
+8[label = "{LMSDevice|...}"]
+9[label = "{USRPDevice|...}"]
+
+2->3[arrowtail=odiamond]
+3->4[constraint=false]
+3->5[constraint=false]
+3->6[arrowtail=odiamond]
+6->7
+6->8
+6->9
+}
+----
+
+[[fig-code-architecture-threads]]
+.Example of thread architecture with OsmoTRX configured to use 2 logical RF channels (Trx=Transceiver, RI=RadioIface)
+[graphviz]
+----
+digraph hierarchy {
+node[shape=record,style=filled,fillcolor=gray95]
+
+trans [label="Transceiver"];
+radioiface [label="RadioInterface"];
+radiodev [label="RadioDevice"];
+
+trans:nw->trans:ne [label="Trx.ControlServiceLoop_0"];
+trans:nw->trans:ne [label="Trx.ControlServiceLoop_1"];
+trans:w->radioiface:w [label="Trx.TxPriorityQueueServiceLoop_0"];
+trans:w->radioiface:w [label="Trx.TxPriorityQueueServiceLoop_1"];
+radioiface:e->trans:e [label="Trx.RxServiceLoop_0"];
+radioiface:e->trans:e [label="Trx.RxServiceLoop_1"];
+radioiface->radiodev[label="RI.AlignRadioServiceLoop"];
+radioiface:sw->radiodev:nw [label="Trx.TxLowerLoop"];
+radiodev:ne->radioiface:se [label="Trx.RxLowerLoop"];
+}
+----
+
+[[code_component_transceiver]]
+=== Transceiver
+
+The Transceiver is the main component managing the other components running in
+the OsmoTRX process. There's a unique instance per process.
+
+This class is quite complex from code point of view, as it starts lots of
+different threads and hence the interaction with this class from the outside is
+quite limited. Only interaction possible is to:
+
+* `Transceiver()`: Create an instance through its constructor, at this time most
+ configuration is handed to it.
+* `init()`: Start running all the threads.
+* `receiveFIFO()`: Attach a `radioInterface` channel FIFO in order to use it.
+* `setSignalHandler()`: Used to set up a callback to receive certain events
+ asynchronously from the Transceiver. No assumptions can be made about from
+ which thread is the callback being called, which means multi-thread locking
+ precautions may be required in certain cases, similar to usual signal handler
+ processing. One important event received through this path is for instance
+ when the Transceiver detected a fatal error which requires it to stop. Since
+ it cannot stop itself (see destructor below), stopping procedure must be
+ delegated to the user who created the instance.
+* `~Transceiver()`: The destructor, which stops all running threads created at
+ `init()` time. Destroying the object is the only way to stop the `Transceiver`
+ completely, and must be called from a thread not managed by the
+ `Transceiver`, otherwise it will deadlock. Usually it is stopped from the main
+ thread, the one that called the constructor during startup.
+
+During `init()` time, `Transceiver` will create a noticeable amount of threads,
+which may vary depending on the amount of RF channels requested.
+
+Static amount of Threads (1 per `Transceiver` instance):
+
+* `RxLowerLoop`: This thread is responsible for reading bursts from the
+ `RadioInterface`, storing them into its FIFO and sending Clock Indications
+ (<<trx_if_clock_ind>>) to _osmo-bts_trx_.
+* `TxLowerLoop`: Manages pushing bursts from buffers in the FIFO into the
+ `RadioInterface` at expected correct time based on the Transceiver clock.
+
+Dynamic amount of Threads (1 per RF logical channel on the `Transceiver` instance):
+
+* `ControlServiceLoop`: Handles commands from the Per-ARFCN Control Interface
+ socket (<<trx_if_control>>). Each thread is responsible for managing one
+ socket related to one ARFCN or which is the same, to one RF logical channel.
+ These are the only threads expected to use the private `start()` and `stop()`
+ methods of the `Transceiver()` class, since those methods don't stop any of
+ the `ControlServiceLoop` threads as they must keep running to handle new
+ commands (for instance, to re-start processing samples with the _POWERON_
+ command).
+* `RxServiceLoop`: Each thread of this type pulls bursts from the
+ `RadioInterface` FIFO for one specific logical RF channel and handles it
+ according to the slot and burst correlation type, finally sending proper data
+ over the TRX Manager UDP socket (<<trx_if>>).
+* `TxPriorityQueueServiceLoop`: Blocks reading from one ARFCN specific TRX
+ Manager UDP socket (<<trx_if>>), and fills the `RadioInterface` with it
+ setting clock related information.
+
+[[code_component_radioiface]]
+=== RadioInterface
+
+The `RadioInterface` sits between the `Transceiver` and the `RadioDevice`, and
+provides extra features to the pipe like channelizers, resamplers, Tx/Rx
+synchronization on some devices, etc.
+
+If the `RadioDevice` it drives requires it (only _USRP1_ so far), the
+`RadioIntercace` will start and manage a thread internally called
+`AlignRadioServiceLoop` which will align current RX and TX timestamps.
+
+Different features are offered through different `RadioInterface` subclasses
+which are selected based on configuration and device detected at runtime. Using
+these features may impact on the amount of CPU required to run the entire pipe.
+
+==== RadioInterfaceResamp
+
+This subclass of `RadioInterface` is automatically selected when some known
+specific UHD are to be used, since they require resampling to work properly.
+Some of this devices are for instance Ettus B100, USRP2 and X3XX models.
+
+==== RadioInterfaceMulti
+
+This subclass of `RadioInterface` is used when <<multiarfcn_mode>> is requested.
+
+[[code_component_radiodev]]
+=== RadioDevice
+
+The `RadioDevice` class is responsible for driving the actual Hardware device.
+It is actually only an interface, and it is implemented in each backend which in
+turn becomes a specific OsmoTRX binary, see <<trx_backends>>.
diff --git a/doc/manuals/chapters/configuration.adoc b/doc/manuals/chapters/configuration.adoc
new file mode 100644
index 0000000..87d7903
--- /dev/null
+++ b/doc/manuals/chapters/configuration.adoc
@@ -0,0 +1,85 @@
+== Configuring OsmTRX
+
+OsmoTRX will read the configuration at startup time and configure the
+transceiver accordingly after validating the configuration.
+
+OsmoTRX can handle several TRX channels, but at least one must be configured in
+order to be able to start it successfully. Channels must be present in the
+configuration file in incremental order, starting from 0 and be consecutive.
+
+Example configuration files for different devices and setups can be found in
+`doc/examples/` in 'osmo-trx' git repository.
+
+=== Documented example
+
+.Example: Static GGSN/APN configuration (single catch-all GGSN)
+----
+trx
+ bind-ip 127.0.0.1 <1>
+ remote-ip 127.0.0.1 <2>
+ base-port 5700 <3>
+ egprs disable <4>
+ tx-sps 4 <5>
+ rx-sps 4 <6>
+ chan 0 <7>
+ tx-path BAND1 <8>
+ rx-path LNAW <9>
+----
+<1> Configure the local IP address at the TRX used for the connection against `osmo-bts-trx`.
+<2> Specify the IP address of `osmo-bts-trx` to connect to.
+<3> Specify the reference base UDP port to use for communication.
+<4> Don't enable EDGE support.
+<5> Use 4 TX samples per symbol. This is device specific.
+<6> Use 4 RX samples per symbol. This is device specific.
+<7> Configure the first channel. As no other channels are specified, `osmo-trx` assumes it is using only one channel.
+<8> Configure the device to use `BAND1` Tx antenna path from all the available ones (device specific).
+<9> Configure the device to use `LNAW` Rx antenna path from all the available ones (device specific).
+
+[[multiarfcn_mode]]
+=== Multi-ARFCN mode
+
+The Multi-ARFCN feature allows to have a multi-carrier approach multiplexed on a
+single physical RF channel, which can introduce several benefits, such as lower
+cost and higher capacity support.
+
+Multi-ARFCN support is available since osmo-trx release `0.2.0`, and it was
+added specifically in commit `76764278169d252980853251daeb9f1ba0c246e1`.
+
+This feature is useful for instance if you want to run more than 1 TRX with an
+Ettus B200 device, or 3 TRX with an Ettus B210 device, since they support only 1
+and 2 physical RF channels respectively. No device from other providers or even
+other devices than B200 and B210 from Ettus are known to support this feature.
+
+With multi-ARFCN enabled, ARFCN spacing is fixed at 800 kHz or 4 GSM channels.
+So if TRX-0 is set to ARFCN 51, TRX-1 _must_ be set to 55, and so on. Up to
+three ARFCN's is supported for multi-TRX.
+
+From BTS and BSC point of view, supporting multiple TRX through multi-ARFCN
+feature in OsmoTRX doesn't make any difference from a regular multi-TRX setup,
+leaving apart of course the mentioned ARFCN limitations explained above and as a
+consequence physical installation and operational differences.
+
+.Example: osmo-bts-trx.cfg using 2 TRX against an osmo-trx driven device
+----
+phy 0
+ osmotrx ip local 127.0.0.1
+ osmotrx ip remote 127.0.0.1
+ instance 0
+ instance 1
+bts 0
+ ...
+ band GSM-1800
+ trx 0
+ phy 0 instance 0
+ trx 1
+ phy 0 instance 1
+----
+
+.Example: osmo-trx.cfg using Multi-ARFCN mode to run 2 TRX
+----
+trx
+ ...
+ multi-arfcn enable
+ chan 0
+ chan 1
+----
diff --git a/doc/manuals/chapters/control.adoc b/doc/manuals/chapters/control.adoc
new file mode 100644
index 0000000..168769a
--- /dev/null
+++ b/doc/manuals/chapters/control.adoc
@@ -0,0 +1,12 @@
+[[control]]
+== Control interface
+
+The actual protocol is described in <<common-control-if>>, the variables
+common to all programs using it are described in <<ctrl_common_vars>>. Here we
+describe variables specific to OsmoTRX.
+
+.Variables available over control interface
+[options="header",width="100%",cols="20%,5%,5%,50%,20%"]
+|===
+|Name|Access|Trap|Value|Comment
+|===
diff --git a/doc/manuals/chapters/counters.adoc b/doc/manuals/chapters/counters.adoc
new file mode 100644
index 0000000..7fbb10c
--- /dev/null
+++ b/doc/manuals/chapters/counters.adoc
@@ -0,0 +1,4 @@
+[[counters]]
+== Counters
+
+include::./counters_generated.adoc[]
diff --git a/doc/manuals/chapters/counters_generated.adoc b/doc/manuals/chapters/counters_generated.adoc
new file mode 100644
index 0000000..b40dc37
--- /dev/null
+++ b/doc/manuals/chapters/counters_generated.adoc
@@ -0,0 +1,7 @@
+// autogenerated by show asciidoc counters
+These counters and their description based on OsmoTRX 0.2.0.61-408f (OsmoTRX).
+
+// generating tables for rate_ctr_group
+// generating tables for osmo_stat_items
+// generating tables for osmo_counters
+// there are no ungrouped osmo_counters
diff --git a/doc/manuals/chapters/overview.adoc b/doc/manuals/chapters/overview.adoc
new file mode 100644
index 0000000..785e26b
--- /dev/null
+++ b/doc/manuals/chapters/overview.adoc
@@ -0,0 +1,62 @@
+[[chapter_introduction]]
+== Overview
+
+[[intro_overview]]
+=== About OsmoTRX
+
+OsmoTRX is a C/C++ language implementation of the GSM radio modem,
+originally developed as the 'Transceiver' part of OpenBTS. This radio
+modem offers an interface based on top of UDP streams.
+
+
+The OsmoBTS bts_model code for OsmoTRX is called
+`osmo-bts-trx`. It implements the UDP stream interface of
+OsmoTRX, so both parts can be used together to implement a complete GSM
+BTS based on general-purpose computing SDR.
+
+As OsmoTRX is general-purpose software running on top of Linux, it is
+thus not tied to any specific physical hardware. At the time of this
+writing, OsmoTRX supports a variety of Lime Microsystems and Ettus USRP SDRs via
+the UHD driver, as well as the Fairwaves UmTRX and derived products.
+
+OsmoTRX is not a complete GSM PHY but 'just' the radio modem. This
+means that all of the Layer 1 functionality such as scheduling,
+convolutional coding, etc. is actually also implemented inside OsmoBTS.
+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
+
+As such, the boundary between OsmoTRX and `osmo-bts-trx` is at
+a much lower interface, which is an internal interface of other more
+traditional GSM PHY implementations.
+
+Besides OsmoTRX, there are also other implementations (both Free
+Software and proprietary) that implement the same UDP stream based radio
+modem interface.
+
+[[fig-gprs-pcubts]]
+.GSM network architecture with OsmoTRX and OsmoBTS
+[graphviz]
+----
+digraph G {
+ rankdir=LR;
+ MS0 [label="MS"];
+ MS1 [label="MS"];
+ MS0->SDR[label="Um"];
+ MS1->SDR [label="Um"];
+ SDR -> OsmoTRX [label="Raw Samples"];
+ OsmoTRX->BTS [label="bursts over UDP"];
+ BTS->BSC [label="Abis"];
+ BSC->MSC [label="A"];
+ BTS->PCU [label="pcu_sock"];
+ PCU->SGSN [label="Gb"];
+ OsmoTRX [color=red];
+}
+----
+
+For more information see
+https://osmocom.org/projects/osmotrx/wiki/OsmoTRX
diff --git a/doc/manuals/chapters/running.adoc b/doc/manuals/chapters/running.adoc
new file mode 100644
index 0000000..7ed2884
--- /dev/null
+++ b/doc/manuals/chapters/running.adoc
@@ -0,0 +1,19 @@
+== Running OsmoTRX
+
+The OsmoTRX executable (`osmo-trx`) offers the following command-line
+options:
+
+
+=== SYNOPSIS
+
+*osmo-trx* [-h] [-C 'CONFIGFILE']
+
+
+=== OPTIONS
+
+*-h*::
+ Print a short help message about the supported options
+*-C 'CONFIGFILE'*::
+ Specify the file and path name of the configuration file to be
+ used. If none is specified, use `osmo_trx.cfg` in the current
+ working directory.
diff --git a/doc/manuals/chapters/trx-architectures.adoc b/doc/manuals/chapters/trx-architectures.adoc
new file mode 100644
index 0000000..66eae5e
--- /dev/null
+++ b/doc/manuals/chapters/trx-architectures.adoc
@@ -0,0 +1,34 @@
+[[osmotrx_arch_support]]
+== OsmoTRX hardware architecture support
+
+OsmoTRX comes out-of-the-box with several algorithms and operations
+optimized for certain instruction-set architectures, as well as non-optimized
+fall-back algorithms in case required instruction sets are not supported by the
+compiler at compile time or by the executing machine at run-time. Support for
+these optimized algorithms can be enabled and disabled by means of configure
+flags. Accelerated operations include pulse shape filtering, resampling,
+sequence correlation, and many other signal processing operations.
+
+On Intel processors, OsmoTRX makes heavy use of the Streaming SIMD Extensions
+(SSE) instruction set. 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. Support
+is automatically detected at build time. SSE4.1 instruction set is supported
+too. This feature is enabled by default unless explicitly disabled by passing
+the configure flag _--with-sse=no_. When enabled, the compiler will build an
+extra version of each of the supported algorithms using each of the supported
+mentioned instruction sets. Then, at run-time, OsmoTRX will auto-detect
+capabilities of the executing machine and enable an optimized algorithm using
+the most suitable available (previously compiled) instruction set.
+
+On ARM processors, NEON and NEON FMA are supported. Different to the x86, there
+is no auto-detection in this case, nor difference between compile and runtime.
+NEON support is disabled by default and can be enabled by passing the flag
+_--with-neon=yes_ to the configure script; the used compiler must support NEON
+instruction set and the resulting binary will only run fine on an ARM board
+supporting NEON extensions. Running OsmoTRX built with flag _--with-neon_ on a
+board without NEON instruction set support, will most probably end up in the
+process being killed with a _SIGILL_ Illegal Instruction signal by the operating
+system. NEON FMA (Fused Multiply-Add) is an extension to the NEON instruction
+set, and its use in OsmoTRX can be enabled by passing the _--with_neon_vfpv4_
+flag, which will also implicitly enable NEON support (_--with_neon_).
diff --git a/doc/manuals/chapters/trx-backends.adoc b/doc/manuals/chapters/trx-backends.adoc
new file mode 100644
index 0000000..8829fa6
--- /dev/null
+++ b/doc/manuals/chapters/trx-backends.adoc
@@ -0,0 +1,46 @@
+[[trx_backends]]
+== OsmoTRX backend support
+
+[[backend_uhd]]
+=== `osmo-trx-uhd` for UHD based Transceivers
+
+This OsmoTRX model uses _libuhd_ (UHD, USRP Hardware Driver) to drive the
+device, that is configuring it and reading/writing samples from/to it.
+
+So far, this backend has been mostly used to drive devices such as the Ettus
+B200 family and Fairwaves UmTRX family, and used to be the default backend used
+for legacy @osmo-trx@ binary when per-backend binaries didn't exist yet.
+
+Any device providing generic support for UHD should theoretically be able to be
+run through this backend without much effort, but pracitcal experience showed
+that some devices don't play well with it, such as the LimeSDR family of
+devices, which showed far better results when using its native interface.
+
+Related code can be found in the _Transceiver52M/device/uhd/_ directory in
+_osmo-trx.git_.
+
+[[backend_lms]]
+=== `osmo-trx-lms` for LimeSuite based Transceivers
+
+This OsmoTRX model uses LimeSuite API and library to drive the device, that is
+configuring it and reading/writing samples from/to it.
+
+This backend was developed in order to be used together with LimeSDR-USB and
+LimeSDR-mini devices, due to to the poor results obtained with the UHD backend,
+and to simplify the stack.
+
+Related code can be found in the _Transceiver52M/device/lms/_ directory in
+_osmo-trx.git_.
+
+[[backend_usrp1]]
+=== `osmo-trx-usrp1` for libusrp based Transceivers
+
+This OsmoTRX model uses the legacy libusrp driver provided in GNU Radio 3.4.2.
+
+As this code was dropped from GNU Radio at some point and was found very
+difficult to build, some work was done to create a standalone libusrp which can
+be nowadays found as a separate git repository together with other osmocom git
+repositories, in https://git.osmocom.org/libusrp/
+
+Related code can be found in the _Transceiver52M/device/usrp1/_ directory in
+_osmo-trx.git_.
diff --git a/doc/manuals/chapters/trx-devices.adoc b/doc/manuals/chapters/trx-devices.adoc
new file mode 100644
index 0000000..10c8529
--- /dev/null
+++ b/doc/manuals/chapters/trx-devices.adoc
@@ -0,0 +1,90 @@
+[[osmotrx_device_support]]
+== OsmoTRX hardware device support
+
+OsmoTRX consists of a _common_ part that applies to all TRX devices as well as
+_hardware-specific_ parts for each TRX device. The hardware-specific parts are
+usually provided by vendor-specific or device-specific libraries that are then
+handled by some OsmoTRX glue code presenting a unified interface towards the
+rest of the code by means of a _RadioDevice_ class.
+
+The common part includes the core TRX architecture as well as code for
+implementing the external interfaces such as the TRX Manager UDP socket,
+control, and VTY interfaces.
+
+The hardware-specific parts include support for driving one particular
+implementation of a radio modem. Such a physical layer
+implementation can come in many forms. Sometimes it runs on a general
+purpose CPU, sometimes on a dedicated ARM core, a dedicated DSP, a
+combination of DSP and FPGA.
+
+Joining the common part with each of the available backends results in a
+different binary with different suffix for each backend. For instance, when
+OsmoTRX is built with UHD backend, an _osmo-trx-uhd_ binary is generated; when
+OsmoTRX is built with LimeSuite backend, an _osmo-trx-lms_ binary is generated.
+Build of different backend can be enabled and disabled by means of configure
+flags, which can be found in each subsection relative to each backend below.
+
+[[dev_ettus_usrp1]]
+=== Ettus USRP1
+
+The binary _osmo-trx-usrp1_ is used to drive this device, see <<backend_usrp1>>.
+
+[[dev_ettus_b200]]
+=== Ettus B200
+
+The binary _osmo-trx-uhd_ is used to drive this device, see <<backend_uhd>>.
+
+Comes only with 1 RF channel. It can still be used in a multi-TRX setup by using
+the <<multiarfcn_mode>> feature. By using this feature, one can drive up to 3
+TRX (with the restrictions explained there).
+
+[[dev_ettus_b200]]
+=== Ettus B210
+
+The binary _osmo-trx-uhd_ is used to drive this device, see <<backend_uhd>>.
+
+Comes with 2 RF channels, which can be used to set up a multi-TRX BTS. However,
+due to a shared local oscillator for both RF channels, ARFCN separation can be
+up about 25 MHz.
+
+This device also supports the <<multiarfcn_mode>> feature. By using this
+feature, one can drive up to 3 TRX (with the restrictions explained there).
+Please note that the above configurations cannot be combined, which means
+maximum number of TRX one can achieve is 2 by using separate physical RF
+channels, or 3 by using multi-ARFCN method. You cannot support, for example, 6
+ARFCN operation on B210 using 3 TRX on side A and another 3 TRX on side B.
+
+[[dev_limesdr_usb]]
+=== LimeSDR-USB
+
+The binary _osmo-trx-lms_ is used to drive this device, see <<backend_lms>>.
+
+This device comes with 2 RF channels, so it should theoretically be possible to
+run a multi-TRX setup with it, but there are yet no records that this kind of
+setup was tested with this device.
+
+This device has 3 different Rx paths with different antenna connectors in the
+PCB, each with a different frequency and bandwidth range. One should make sure
+the physical antenna is connected to the correct connector matching the Rx path
+you want to use. If one wants to be able to use the device in both 900 and 1800
+MHz GSM bands and easily switch between them, then Rx Path `LNAW` should be used
+,since it is the only one covering both bands, and the antenna physically plugged
+accordingly. Following example shows how to then configure _osmo-trx-lms_ to use
+that Rx path to read samples.
+
+.Example: Configure osmo-trx-lms to use LNAW as Rx path and BAND1 as Tx Path
+----
+trx
+ ...
+ chan 0
+ tx-path BAND1
+ rx-path LNAW
+----
+
+[[dev_limesdr_mini]]
+=== LimeSDR-mini
+
+The binary _osmo-trx-lms_ is used to drive this device, see <<backend_lms>>.
+
+As a smaller brother of the [[dev_limesdr_usb]], this device comes only with 1
+RF channel. As a result, it can only hold 1 TRX as of today.