74 lines
2.5 KiB
Plaintext
74 lines
2.5 KiB
Plaintext
== Location Services: Lb interface to SMLC
|
|
|
|
OsmoBSC and OsmoSMLC support positioning by Timing-Advance (TA), since October
|
|
2020.
|
|
|
|
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. In
|
|
TA-based positioning, the Timing-Advance information 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.
|
|
|
|
[mscgen]
|
|
----
|
|
include::{srcdir}/message-sequences/location_services_ta.msc[]
|
|
----
|
|
|
|
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>>.
|
|
|
|
[[smlc-config]]
|
|
=== Configure Lb-interface
|
|
|
|
All Lb-interface related configuration is found in the `smlc` section of
|
|
OsmoBSC's configuration.
|
|
|
|
By default, the Lb-interface is disabled in OsmoBSC. It is started by `enable`.
|
|
|
|
----
|
|
smlc
|
|
enable
|
|
----
|
|
|
|
On the Lb-interface, OsmoBSC always uses SSN "BSC (BSSMAP-LE)" (SSN code 250)
|
|
and contacts the remote SMLC on SSN "SMLC (BSSMAP-LE)" (SSN code 252).
|
|
|
|
The point-codes are configurable, and default to OsmoBSC's local point-code
|
|
0.23.3 (187), and remote SMLC point-code 0.23.6 (190).
|
|
|
|
To configure a different remote SMLC point-code, first configure an arbitrarily
|
|
named SCCP address in the `cs7` address book, and then apply that to the
|
|
`smlc-addr` configuration:
|
|
|
|
----
|
|
cs7 instance 0
|
|
sccp-address my-smlc
|
|
point-code 0.42.6
|
|
smlc
|
|
smlc-addr my-smlc
|
|
----
|
|
|
|
Similarly, OsmoBSC's local point-code on the Lb-interface is configured by the
|
|
`bsc-addr` configuration:
|
|
|
|
----
|
|
cs7 instance 0
|
|
sccp-address my-bsc-on-lb
|
|
point-code 0.42.3
|
|
smlc
|
|
bsc-addr my-bsc-on-lb
|
|
----
|
|
|
|
The geographic locations of individual cells are configured at the SMLC. See
|
|
for example OsmoSMLC's user manual <<userman-osmosmlc>>.
|