70 lines
2.3 KiB
Plaintext
70 lines
2.3 KiB
Plaintext
[[overview]]
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== Overview
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This manual should help you getting started with OsmoBSC. It will cover
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aspects of configuring and running the OsmoBSC.
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[[intro_overview]]
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=== About OsmoBSC
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OsmoBSC is one particular version of the OpenBSC software suite.
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Unlike the highly integrated OmsoNITB, OsmoBSC impleents a more classic
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GSM Base Station Controller with A-bis interface towards BTSs and A
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interface towards a MSC.
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=== Software Components
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OsmoBSC contains a variety of different software components, which
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we'll quickly describe in this section.
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==== A-bis Implementation
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OsmoBSC implements the ETSI/3GPP specified A-bis interface, including
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TS 08.56 (LAPD), TS 08.58 (RSL) and TS 12.21 (OML). In addition, it
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supports a variety of vendor-specific extensions and dialects in order
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to communicate with BTSs from Siemens, Nokia, Ericsson, ip.access and
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sysmocom.
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For more information, see <<bts>> and <<bts-examples>>.
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==== A Implementation
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OsmoBSC implements a minimal sub-set of the GSM A interface as specified
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in TS 08.08.
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Unlike classic A interface implementations for E1 interfacs, OsmoBSC
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implements a variant of encapsulating the A interface over IP. To do
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so, the SCCP messages are wrapped in an IPA multiplex and then
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communicated over TCP. The audio channels are mapped to RTP streams.
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This protcol stacking is sometimes called "SCCPlite".
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For more information, see <<alink>>.
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==== BSC Implementation
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The BSC implementation covers the classic functionality of a GSM Base
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Station Controller, i.e.
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* configuring and bringing up BTSs with their TRXs and TSs
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* implementing the A-bis interface / protocols for signalling and actual
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voice data (TRAU frames).
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* processing measurement results from the mobile stations in dedicated
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mode, performing hand-over decision and execution.
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* Terminating the TS 04.08 RR (Radio Resource) sub-layer from the MS.
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For more information, see <<net>>, <<bts>> and <<bts-examples>>.
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==== TRAU mapper / E1 sub-channel muxer
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Unlike classic GSM networks, OsmoBSC does not perform any transcoding.
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Rather, a compatible codec is selected for both legs of a call, and
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codec frames are passed through transparently. In order to achieve this
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with E1 based BTS, OsmoBSC contains a E1 sub-channel de- and
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re-multiplexer as well as a TRAU mapper that can map uplink to downlink
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frames and vice versa.
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