| Harald Welte | 75c0e08 | 2016-02-20 10:56:10 +0100 | [diff] [blame^] | 1 | [[overview]] |
| 2 | == Overview |
| 3 | |
| 4 | This manual should help you getting started with OsmoBSC. It will cover |
| 5 | aspects of configuring and running the OsmoBSC. |
| 6 | |
| 7 | [[intro_overview]] |
| 8 | === About OsmoBSC |
| 9 | |
| 10 | OsmoBSC is one particular version of the OpenBSC software suite. |
| 11 | |
| 12 | Unlike the highly integrated OmsoNITB, OsmoBSC impleents a more classic |
| 13 | GSM Base Station Controller with A-bis interface towards BTSs and A |
| 14 | interface towards a MSC. |
| 15 | |
| 16 | |
| 17 | === Software Components |
| 18 | |
| 19 | OsmoBSC contains a variety of different software components, which |
| 20 | we'll quickly describe in this section. |
| 21 | |
| 22 | ==== A-bis Implementation |
| 23 | |
| 24 | OsmoBSC implements the ETSI/3GPP specified A-bis interface, including |
| 25 | TS 08.56 (LAPD), TS 08.58 (RSL) and TS 12.21 (OML). In addition, it |
| 26 | supports a variety of vendor-specific extensions and dialects in order |
| 27 | to communicate with BTSs from Siemens, Nokia, Ericsson, ip.access and |
| 28 | sysmocom. |
| 29 | |
| 30 | For more information, see <<bts>> and <<bts-examples>>. |
| 31 | |
| 32 | ==== A Implementation |
| 33 | |
| 34 | OsmoBSC implements a minimal sub-set of the GSM A interface as specified |
| 35 | in TS 08.08. |
| 36 | |
| 37 | Unlike classic A interface implementations for E1 interfacs, OsmoBSC |
| 38 | implements a variant of encapsulating the A interface over IP. To do |
| 39 | so, the SCCP messages are wrapped in an IPA multiplex and then |
| 40 | communicated over TCP. The audio channels are mapped to RTP streams. |
| 41 | |
| 42 | This protcol stacking is sometimes called "SCCPlite". |
| 43 | |
| 44 | For more information, see <<alink>>. |
| 45 | |
| 46 | |
| 47 | ==== BSC Implementation |
| 48 | |
| 49 | The BSC implementation covers the classic functionality of a GSM Base |
| 50 | Station Controller, i.e. |
| 51 | |
| 52 | * configuring and bringing up BTSs with their TRXs and TSs |
| 53 | * implementing the A-bis interface / protocols for signalling and actual |
| 54 | voice data (TRAU frames). |
| 55 | * processing measurement results from the mobile stations in dedicated |
| 56 | mode, performing hand-over decision and execution. |
| 57 | * Terminating the TS 04.08 RR (Radio Resource) sub-layer from the MS. |
| 58 | |
| 59 | For more information, see <<net>>, <<bts>> and <<bts-examples>>. |
| 60 | |
| 61 | |
| 62 | ==== TRAU mapper / E1 sub-channel muxer |
| 63 | |
| 64 | Unlike classic GSM networks, OsmoBSC does not perform any transcoding. |
| 65 | Rather, a compatible codec is selected for both legs of a call, and |
| 66 | codec frames are passed through transparently. In order to achieve this |
| 67 | with E1 based BTS, OsmoBSC contains a E1 sub-channel de- and |
| 68 | re-multiplexer as well as a TRAU mapper that can map uplink to downlink |
| 69 | frames and vice versa. |