BSC,BTS: add diagrams of PCU-BTS-NITB-SGSN relationships
Change-Id: I0eb09706efb768fa4f6810872fb6568cbc9838cb
diff --git a/doc/manuals/chapters/overview.adoc b/doc/manuals/chapters/overview.adoc
index 580a42e..3bb22cc 100644
--- a/doc/manuals/chapters/overview.adoc
+++ b/doc/manuals/chapters/overview.adoc
@@ -13,6 +13,75 @@
GSM Base Station Controller with A-bis interface towards BTSs and A
interface towards a MSC.
+The difference between classic GSM network architecture and
+the OsmoNITB based GSM network architecture is illustrated in
+<<fig-gsm-classic>> and <<fig-gsm-nitb>>.
+
+[[fig-gsm-classic]]
+.Classic GSM network architecture (simplified)
+[graphviz]
+----
+digraph G {
+ rankdir=LR;
+ MS0 [label="MS"];
+ MS1 [label="MS"];
+ MS2 [label="MS"];
+ MS3 [label="MS"];
+ BTS0 [label="BTS"];
+ BTS1 [label="BTS"];
+ BSC;
+ MSC [label="MSC/VLR"];
+ HLR [label="HLR/AUC"];
+ EIR;
+ SMSC;
+ MS0->BTS0 [label="Um"];
+ MS1->BTS0 [label="Um"];
+ MS2->BTS1 [label="Um"];
+ MS3->BTS1 [label="Um"];
+ BTS0->BSC [label="Abis"];
+ BTS1->BSC [label="Abis"];
+ BSC->MSC [label="A"];
+ MSC->HLR [label="C"];
+ MSC->EIR [label="F"];
+ MSC->SMSC;
+}
+----
+
+[[fig-gsm-nitb]]
+.GSM system architecture using OsmoNITB
+[graphviz]
+----
+digraph G {
+ rankdir=LR;
+ MS0 [label="MS"];
+ MS1 [label="MS"];
+ MS2 [label="MS"];
+ MS3 [label="MS"];
+ BTS0 [label="BTS"];
+ BTS1 [label="BTS"];
+ EXTMNCC [label="Linux Call Router / SoftSwitch / PBX\n(optional)"];
+ MS0->BTS0 [label="Um"];
+ MS1->BTS0 [label="Um"];
+ MS2->BTS1 [label="Um"];
+ MS3->BTS1 [label="Um"];
+ BTS0->BSC [label="Abis"];
+ BTS1->BSC [label="Abis"];
+ subgraph cluster_nitb {
+ label = "OsmoNITB";
+ BSC;
+ MSC [label="MSC/VLR"];
+ SMSC;
+ EIR;
+ HLR [label="HLR/AUC"];
+ BSC->MSC;
+ MSC->HLR;
+ MSC->EIR;
+ MSC->SMSC;
+ }
+ MSC -> EXTMNCC [label="external MNCC"];
+}
+----
+
=== Software Components