Getting to know the GSMA’s TAP files, what’s in them, and how they’re used to bill roaming traffic.
Category Archives: GSM
Sending SMS with an alphanumeric String as the Source
If you’ve ever received an SMS from your operator, and the sender was the Operator name for example, you may be left wondering how it’s done. In IMS you’d think this could be quite simple – You’d set the From header to be the name rather than the MSISDN, but for most SMSoIP deployments, the … Continue reading Sending SMS with an alphanumeric String as the Source
USSD Gateway with Osmocom
Unstructured Supplementary Service Data or “USSD” is the stack used in Cellular Networks to offer interactive text based menus and systems to Subscribers. If you remember topping up your mobile phone credit via a text menu on your flip phone, there’s a good chance that was USSD*. For a period, USSD Services provided Sporting Scores, … Continue reading USSD Gateway with Osmocom
Demystifying SS7 & Sigtran – Part 4 – Routing with Point Codes
Getting from Point Code A to Point Code Z.
The Surprisingly Complicated World of SMS: Special Characters
A look at how characters are encoded in an SMS.
The Surprisingly Complicated World of SMS: Concatenated / Multipart SMS
Another deep dive into deceptively simple seeming functions to do with SMS.
Looking inside the MMS Exchange (With call flow and PCAP)
A look at Multimedia Messaging (MMS) in 3GPP Networks and how it actually works.
Pre-5G Network Slicing
5G introduces Network Slicing, or does it? A look at slicing mechanisms widely used in pre-5G networks.
The Surprisingly Complicated world of MO SMS in IMS/VoLTE
Short messaging can be anything but simple…
And the call was coming from… INSIDE THE HOUSE. A look at finding UE Locations in LTE
How to find a subscriber location within the network.
Confidentiality Algorithms in 3GPP Networks: MILENAGE, XOR & Comp128
A look at the Confidentiality Algorithms used in 3GPP Networks, MILENAGE, XOR & Comp128
SIM / Smart Card Deep Dive – Part 3 – APDUs and Hello Card
A look at APDUs and Interacting with Cards
SIM / Smart Card Deep Dive – Part 2 – Meet & Greet
The basics of Smart Cards & their File System
SIM / Smart Card Deep Dive – Part 1 – Introduction to Smart Cards
Getting up close and personal with Smart Card / SIM Cards
GSM with Osmocom: OsmoSGSN for Packet Data
Configuring the Osmocom Serving Gateway Support Node (SGSN) for 2G/3G networks.
Using a NanoVNA to analyse SDR Base Station Antennas
Using a NanoVNA to analyse antenna performance for SDR driven Base Stations for GSM / LTE.
Twenty years of the Nokia 3310
1 September 2000 was when the 3310 was released…
Android Carrier Privileges
Unlocking Carrier Privileges through certificate on a UICC
Getting TEID up with GTP Tunnels
What’s the deal with Tunnel Endpoint Identifiers and what do they do?
GSM with Osmocom: Handovers
A look at the Handover process between Cells / BTSs in GSM using the Osmocom stack.
Random Posts on GSM
Dumb Lesson in RF Connectors
Kamailio Bytes – DMQ
Under the Hood with NBN FTTC Hardware (DPUs)
HOMER API in Python
Viewing the SIB – The LTE System Information Block with SDRs
GSM with Osmocom Part 2: BTS Basics
Control + R in Bash = Life Changed
srsLTE Install for BladeRF & LimeSDR on Debian / Ubuntu
Kamailio Bytes – Extracting SDP Parameters with Kamailio