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manual: describe LCS and Lb interface 

Change-Id: I7ba432706759433987fabbc674bfc8cd55f2ce62
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Neels Hofmeyr 2020-10-28 03:24:27 +01:00
parent c4c6ba4b07
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12
doc/manuals/chapters/running.adoc
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@ -140,3 +140,15 @@ msc 0
mgw remote-ip 10.9.8.7
mgw remote-port 2427
----
==== Configure Lb to connect to an SMLC
Enable the Lb interface. OsmoBSC will then use the default point-codes to
establish a connection to the SMLC.
----
smlc
enable
----
More detailed configuration is described in <<smlc-config>>.

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doc/manuals/chapters/smlc.adoc Normal file
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== 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>>.

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doc/manuals/message-sequences/location_services_ta.msc Normal file
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msc {
hscale="2";
ms[label="MS/BTS"],bsc[label="BSC"],smlc[label="SMLC"],__msc[label="MSC"];
||| [label="Location Services (LCS): Perform Location Request using TA"];
|||;
--- [label="MS in DEDICATED MODE (currently active)"];
ms =>> bsc [label="earlier Measurement Report provides Timing Advance"];
bsc <<= __msc [label="PERFORM LOCATION REQUEST\n3GPP TS 48.008 3.2.1.71"];
bsc =>> smlc [label="BSSMAP-LE PERFORM LOCATION REQUEST\n3GPP TS 49.031 9.1\nwith BSSLAP APDU = TA Layer3\n3GPP TS 48.071 4.2.8"];
smlc rbox smlc [label="SMLC uses TA included in TA Layer3"];
bsc <<= smlc [label="BSSMAP-LE PERFORM LOCATION RESPONSE\n3GPP TS 49.031 9.2"];
bsc =>> __msc [label="PERFORM LOCATION RESPONSE\n3GPP TS 48.008 3.2.1.72"];
...;
...;
--- [label="MS in IDLE MODE (not connected)"];
bsc <<= __msc [label="PERFORM LOCATION REQUEST\n3GPP TS 48.008 3.2.1.71"];
bsc =>> smlc [label="BSSMAP-LE PERFORM LOCATION REQUEST\n3GPP TS 49.031 9.1"];
smlc rbox smlc [label="SMLC needs TA information,\nasks BSC via BSSLAP"];
bsc <<= smlc [label="BSSMAP-LE CONNECTION ORIENTED INFORMATION\n3GPP TS 49.031 9.12\nwith BSSLAP APDU = TA Request\n3GPP TS 48.071 4.2.1"];
ms <<= bsc [label="RR Paging Request\n3GPP TS 48.018 9.1.22-24"];
ms =>> bsc [label="RSL CHANNEL REQUIRED\n3GPP TS 48.058 8.5.3\nincludes Access Delay (9.3.17) == Timing Advance"];
ms =>> bsc [label="RR Paging Response\n3GPP TS 48.018 9.1.25"];
ms <<= bsc [label="RF CHANNEL RELEASE\n3GPP TS 48.058 8.4.14"];
bsc =>> smlc [label="BSSMAP-LE CONNECTION ORIENTED INFORMATION\n3GPP TS 49.031 9.12\nwith BSSLAP APDU = TA Response\n3GPP TS 48.071 4.2.2"];
bsc <<= smlc [label="BSSMAP-LE PERFORM LOCATION RESPONSE\n3GPP TS 49.031 9.2"];
bsc =>> __msc [label="PERFORM LOCATION RESPONSE\n3GPP TS 48.008 3.2.1.72"];
}

2
doc/manuals/osmobsc-usermanual.adoc
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@ -30,6 +30,8 @@ include::{srcdir}/chapters/smscb.adoc[]
include::{srcdir}/chapters/mscpool.adoc[]
include::{srcdir}/chapters/smlc.adoc[]
include::./common/chapters/counters-overview.adoc[]
include::{srcdir}/chapters/counters.adoc[]