| Neels Hofmeyr | 88a0789 | 2020-10-28 03:24:27 +0100 | [diff] [blame] | 1 | == Location Services: Lb interface to SMLC |
| 2 | |
| 3 | OsmoBSC and OsmoSMLC support positioning by Timing-Advance (TA), since October |
| 4 | 2020. |
| 5 | |
| 6 | A Perform Location Request is initiated by the MSC via BSSMAP on the |
| 7 | A-interface, for a specific subscriber. The request is typically passed on via |
| 8 | BSSMAP-LE on the Lb-interface to the SMLC. If required, the SMLC may request the |
| 9 | subscriber's Timing Advance (a.k.a. Access Delay) from the BSC via BSSLAP |
| 10 | (encapsulated BSSLAP APDU in a BSSMAP-LE Connection Oriented Information |
| 11 | message). The SMLC may combine several location and velocity estimate methods to |
| 12 | form a GAD PDU containing the resulting geographic location information. In |
| 13 | TA-based positioning, the Timing-Advance information from the BSC is combined |
| 14 | with the preconfigured latitude and longitude of the serving cell to form a |
| 15 | location estimate. This is returned to the BSC via the Lb-interface, and in turn |
| 16 | to the MSC via the A-interface. |
| 17 | |
| 18 | [mscgen] |
| 19 | ---- |
| 20 | include::{srcdir}/message-sequences/location_services_ta.msc[] |
| 21 | ---- |
| 22 | |
| 23 | Location Services (LCS) are described in 3GPP TS 43.059 <<3gpp-ts-43-059>>. |
| 24 | Messages for LCS on the A-interface (BSSMAP, between BSC and MSC) are described |
| 25 | in 3GPP TS 48.008 <<3gpp-ts-48-008>>, on the Lb-interface (BSSMAP-LE between BSC |
| 26 | and SMLC) in 3GPP TS 49.031 <<3gpp-ts-49-031>>. The resulting geographic |
| 27 | location and possibly velocity information is encoded in GAD, described in 3GPP |
| 28 | TS 23.032 <<3gpp-ts-23-032>>. |
| 29 | |
| 30 | [[smlc-config]] |
| 31 | === Configure Lb-interface |
| 32 | |
| 33 | All Lb-interface related configuration is found in the `smlc` section of |
| 34 | OsmoBSC's configuration. |
| 35 | |
| 36 | By default, the Lb-interface is disabled in OsmoBSC. It is started by `enable`. |
| 37 | |
| 38 | ---- |
| 39 | smlc |
| 40 | enable |
| 41 | ---- |
| 42 | |
| 43 | On the Lb-interface, OsmoBSC always uses SSN "BSC (BSSMAP-LE)" (SSN code 250) |
| 44 | and contacts the remote SMLC on SSN "SMLC (BSSMAP-LE)" (SSN code 252). |
| 45 | |
| 46 | The point-codes are configurable, and default to OsmoBSC's local point-code |
| 47 | 0.23.3 (187), and remote SMLC point-code 0.23.6 (190). |
| 48 | |
| 49 | To configure a different remote SMLC point-code, first configure an arbitrarily |
| 50 | named SCCP address in the `cs7` address book, and then apply that to the |
| 51 | `smlc-addr` configuration: |
| 52 | |
| 53 | ---- |
| 54 | cs7 instance 0 |
| 55 | sccp-address my-smlc |
| 56 | point-code 0.42.6 |
| 57 | smlc |
| 58 | smlc-addr my-smlc |
| 59 | ---- |
| 60 | |
| 61 | Similarly, OsmoBSC's local point-code on the Lb-interface is configured by the |
| 62 | `bsc-addr` configuration: |
| 63 | |
| 64 | ---- |
| 65 | cs7 instance 0 |
| 66 | sccp-address my-bsc-on-lb |
| 67 | point-code 0.42.3 |
| 68 | smlc |
| 69 | bsc-addr my-bsc-on-lb |
| 70 | ---- |
| 71 | |
| 72 | The geographic locations of individual cells are configured at the SMLC. See |
| 73 | for example OsmoSMLC's user manual <<userman-osmosmlc>>. |