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