| [[overview]] |
| == Overview |
| |
| This manual should help you getting started with OsmoSMLC. It will cover |
| aspects of configuring and running the OsmoSMLC. |
| |
| [[intro_overview]] |
| === About OsmoSMLC |
| |
| OsmoSMLC is the Osmocom implementation of a Serving Mobile Location Center. |
| |
| A Perform Location Request is initiated by the MSC via BSSMAP on the |
| A-interface, for a specific subscriber. The request is typically passed on via |
| BSSMAP-LE on the Lb-interface to the SMLC. If required, the SMLC may request the |
| subscriber's Timing Advance (a.k.a. Access Delay) from the BSC via BSSLAP |
| (encapsulated BSSLAP APDU in a BSSMAP-LE Connection Oriented Information |
| message). The SMLC may combine several location and velocity estimate methods to |
| form a GAD PDU containing the resulting geographic location information. |
| |
| So far, OsmoSMLC implements only Timing Advance based positioning. In TA-based |
| positioning, the Timing-Advance information received from the BSC is combined |
| with the preconfigured latitude and longitude of the serving cell to form a |
| location estimate. This is returned to the BSC via the Lb-interface, and in |
| turn to the MSC via the A-interface. |
| |
| Location Services (LCS) are described in 3GPP TS 43.059 <<3gpp-ts-43-059>>. |
| Messages for LCS on the A-interface (BSSMAP, between BSC and MSC) are described |
| in 3GPP TS 48.008 <<3gpp-ts-48-008>>, on the Lb-interface (BSSMAP-LE between BSC |
| and SMLC) in 3GPP TS 49.031 <<3gpp-ts-49-031>>. The resulting geographic |
| location and possibly velocity information is encoded in GAD, described in 3GPP |
| TS 23.032 <<3gpp-ts-23-032>>. |
| |
| == Lb Interface |
| |
| The Lb interface connects BSC to SMLC and consists of BSSMAP-LE/SCCP/M3UA. It |
| is routed via an STP instance, as is typical for SCCP. The BSSMAP-LE messages |
| may encapsulate BSSLAP and GAD PDUs. |
| |
| OsmoSMLC by default connects to an STP at 127.0.0.1:2905, and registers with |
| its own point-code, default is 0.23.6, on SSN "SMLC (BSSMAP-LE)" (SSN code |
| 252). |
| |
| A BSC on an Lb link typically uses SSN "BSC (BSSMAP-LE)" (SSN code 250). Each |
| BSC connecting to the SMLC must have a distinct own point-code. OsmoBSC's own |
| default point-code is 0.23.3, but when more than one BSC is in use, BSC point |
| codes should be configured explicitly. |
| |
| OsmoSMLC waits for BSC instances to establish Lb interface connections. It does |
| not require knowledge of individual BSCs' point-codes (OsmoSMLC does require |
| preconfigured cell location information, see <<cell-locations>>). |
| |
| On establishing the Lb link, a BSC should send a BSSMAP-LE RESET; the Lb link |
| is usable for per-subscriber connections as soon as OsmoSMLC responds with a |
| BSSMAP-LE RESET ACKNOWLEDGE. |