Mobile Networks

EPC
EUTRAN
LTE
Mobile Networks
RFCs & Standards

LTE UE Attach Procedures in Evolved Packet Core (EPC)

A look into the signalling messages between Network elements in an Evolved Packet Core exchanged during the Attach Procedure

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EUTRAN
LTE
Mobile Networks
RFCs & Standards
Voice over IP

Diameter and SIP: Registration-Termination-Request / Answer

These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Registration-Termination Request / Answer allow a Diameter Client (S-CSCF) to indicate to the HSS (Diameter Server) that it is no longer serving that user and the registration has […]

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Diameter-User-Authorization-Request-Command-Code-300-Packet-Capture
EPC
LTE
Mobile Networks
RFCs & Standards
Voice over IP

Diameter and SIP: User-Authorization-Request/Answer

The Diameter User-Authorization-Request and User-Authorization-Answer commands are used as the first line of authorization of a user and to determine which Serving-CSCF to forward a request to.

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Diameter - Server Assignment Answer - All
EPC
LTE
Mobile Networks
RFCs & Standards
Voice over IP

Diameter and SIP: Server-Assignment-Request/Answer

These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Server-Assignment-Request/Answer commands are used so a SIP Server can indicate to a Diameter server that it is serving a subscriber and pull the profile information of the subscriber. […]

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EPC
LTE
Mobile Networks
RFCs & Standards
Voice over IP

Diameter and SIP: Location-Info-Request / Answer

These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Location-Information-Request/Answer commands are used so a SIP Server query a Diameter to find which P-CSCF a Subscriber is being served by Basics: The RFC’s definition is actually pretty […]

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Screenshot of packet capture of Diameter Multimedia-Auth-Request (Diameter Command Code 303) used for IMS authentication
EPC
LTE
Mobile Networks
RFCs & Standards

Diameter and SIP: Multimedia-Authentication-Request/Answer

These posts focus on the use of Diameter and SIP in an IMS / VoLTE context, however these practices can be equally applied to other networks. The Multimedia-Authentication-Request/Answer commands are used to Authenticate subscribers / UAs using a variety of mechanisms such as straight MD5 and AKAv1-MD5. Basics: When a SIP Server (S-CSCF) receives a […]

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GSM
Mobile Networks

GSM with Osmocom: NanoBTS

Setting up ipaccess NanoBTS on Osmocom’s OsmoBSC

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iPhone connecting to SRS LTE eNodeB SDR
EUTRAN
LTE
Mobile Networks

srsLTE Install for BladeRF & LimeSDR on Debian / Ubuntu

Note: I’m running 19.12.0 which I installed from the repos due to issues with 20.4.0 (latest when I wrote this) and stability on LimeSDR. I wrote the other day about installing SRS LTE stack, But installing it is one thing, meeting all the requirements to use it with your SDR hardware turns out to be […]

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EPC
EUTRAN
GSM
LTE
Mobile Networks

OsmoMSC and Open5GS MME – SGs Interface for CSCF / InterRAT Handover

Looking into the SGi interface for Circuit Switched Fallback in LTE to use GSM/UMTS networks for Calls & SMS

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GSM
Mobile Networks
Voice over IP

GSM with Osmocom: Call routing in GSM

How call routing in GSM works and it’s application in the Osmocom suite

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GSM
Mobile Networks
RF

GSM with Osmocom Part 9: Calls & SMS at last!

So now we’ve covered the basics of what’s involved let’s get some traffic on our network. For starters we’ll need to start each of our network elements and bring up whichever BTS hardware we’re using. In order for our calls to have audio, we’ll need to set a parameter on the Media Gateway. We’ll cover […]

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GSM MSC Architecture
GSM
Mobile Networks

GSM with Osmocom Part 8: The Mobile Switching Center

Setting up the Mobile Switching Centre for a GSM network using OsmoMSC.

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OsmoHLR - Update Location Request
GSM
Mobile Networks

GSM with Osmocom Part 7: The HLR – Home Location Register (and Friends)

The Home Location Register serves the AAA functions in a GSM / UMTS (2G/3G) network as well as locating which Mobile Switching Center (MSC) a subscriber is being served by. The HLR is the equivalent of the Home Subscriber Server in LTE (I’ve written a fair bit about the role of the HSS in LTE […]

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GSM
Mobile Networks

GSM with Osmocom Part 6: Integrating our LimeSDR BTS with OsmoBSC

In the last post we covered the config required to provision a new BTS in our BSC. We’re going to do roughly the same thing this time around, as we connect our SDR based BTS to our BSC. Before we fire up the BTS side of things make sure you’ve stopped the virtual BTS and […]

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GSM
Mobile Networks

GSM with Osmocom Part 5: Software BTS with LimeSDR & osmo-bts-trx

Osmo-BSC accepts Abis over IP connections from a number of different sources, There’s a list of supported BTS hardware that can talk out of the box to the Osmo-BSC, such as the Ericsson RBS series, ip.access nanoBTS, Nokia and Siemens units and even a virtual BTS so you can simulate the connections. If you’re using […]

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GSM
Mobile Networks

GSM with Osmocom Part 4: The Base Station Controller (BSC)

So in our last post we finished setting up a Base Transceiver Station (BTS) but it’s no use unless it can home itself to a Base Station Controller (BSC). So what does a BSC do? The BSC acts as a central controller for one or more BTS. In practice this means the BSC configures most […]

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Basic GSM Architecture
GSM
Mobile Networks

GSM with Osmocom Part 3: Introduction to Osmo Software & Virtual BTS

So this series of posts will focus on using Osmocom software to create a GSM network, so let’s get some Osmocom software installed, and talk about how we run and configure each network element / node. Osmocom Packages For this tutorial series I’ll be using Ubuntu 18.04 and trying where possible to use packages from […]

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