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Mar 20, 2014

Bootstrapping server function (BSF) in LTE

Recently I faced question about role of Bootstrapping Server Function (BSF) function in the LTE network, this made me thinking and digging. On the end I decided to share this woit you in case anyone has ever wondered about that. So what is the role of BSF in LTE?

The BSF queries the Subscriber Locator Function (SLF) over Dz interface, which is Diameter based,  to get the name of the HSS containing the required subscriber specific data.

It's similar to Zh or Zh' (Z-h-prim), dont remember it right now, interface used by BSF to connect to HLR to fetch authentication information.

Check the 3GPP 33.220 for more details http://www.3gpp.org/ftp/specs/archive/33_series/33.220/

Jan 15, 2014

Resource: SIM Card Forensics - Introduction

Just few moments ago I have found quite interesting article that covers in details how the SIM card is build and works. Maybe for Terminal-side guys this is obvious but myself I found few new things for myself.
As the title says this is just introduction, more information could be coming.

SIM Structure and File Systems

A SIM card contains a processor and operating system with between 16 and 256 KB of persistent, electronically erasable, programmable read-only memory (EEPROM). It also contains RAM (random access memory) and ROM (read-only memory). RAM controls the program execution flow and the ROM controls the operating system work flow, user authentication, data encryption algorithm, and other applications. The hierarchically organized file system of a SIM resides in persistent memory and stores data as names and phone number entries, text messages, and network service settings. Depending on the phone used, some information on the SIM may coexist in the memory of the phone. Alternatively, information may reside entirely in the memory of the phone instead of available memory on the SIM.
Fig. 1. SIM Card File System

follow the link to get more - resource.


Jan 14, 2014

Combined Attach in LTE/4G

Some time ago I'v covere the Attach Procedure, from then many times I saw questions about the Combined Attach.
So here it is, the Combined Attach himself.

First it has to be addressed what is the Combined Attach and why it's so different from Attach procedure already covered.

What Combined Attach is?

It's attach for both EPS and non-EPS services, or both EPS services and "SMS only".
The combined attach procedure is also used by a UE in CS/PS to attach for EPS services if it is already IMSI attached for non-EPS services.

How Combined Attach is triggered?

When the UE initiates a combined attach procedure, the UE shall indicate "combined EPS/IMSI attach" in the EPS attach type IE.

If the UE is in EMM state EMM-DEREGISTERED, the UE initiates the combined attach procedure by sending an ATTACH REQUEST message to the network, starting timer T3410 (More about EMM timers? Check the EMM timers or ESM timers article) and entering state EMM-REGISTERED-INITIATED.

If timer T3402 is currently running, the UE shall stop timer T3402. If timer T3411 is currently running, the UE shall stop timer T3411.

Jan 2, 2014

New year, another year online!

Hi everyone!,
It has been 2 years since the blog is up and running, or it will be in exactly 4 days from now. ;-)

Few things has changed during this time in my private life, I have definitely moved forward with what I'm doing for living, and definitely running this blog helped me to evolve.

Your comments and inputs to whatever I'm posting keeps me up to speed and motivated. Anyone of them is important to me, thanks for everything. With few of you I'm having conversations on telecom topics on monthly basis. Thanks for your trust in me.
Thanks for all your questions and for the opportunities to help in problems you had. Solving those also pushed me forward.

If you have any questions or propositions I could take into consideration to write about simply let me know.

Hope you will stick with me next 2 years or even longer.

Wish you all great 2014, success at work and ample of energy to self improve.

Regards, Cheers!,
Bart Barton