Getting Started in the Mobile World

Got this challenge from one of my readers:

I've recently changed jobs and I am currently working for a telco. The problem is that I have no idea of what they are talking about when they mention SGSN, GGSN, Gi, Gn, etc... I only know routing and switching stuff :(.

Obviously he tried to search for information and failed.

Wikipedia articles seem to assume that you already know your stuff, and it just becomes one hell of a rabbit hole.

So he's wondering:

Is there any "unifying" book that goes from basics to more advanced topics, just to get me started?

I guess he's not alone. I tried to understand those same concepts not so long ago and also gave up after trying (unsuccessfully) to decipher LTE standards. Any pointer to reasonable entry-level material would be highly appreciated!


  1. I've never read it, but from a short look this book looks promising..
    From GSM to LTE-advanced: An Introduction to Mobile Networks and Mobile Broadband
    ISBN-13: 978-1118861950
  2. There was a presentation at DKNOG4 a few years back about this, unfortunately there is no video of the presentation but the slides are available
  3. SAE and the Evolved Packet Core was good. First book I bought when I was in the same boat.
  4. SAE and the Evolved Packet Core is a great book
  5. Had the same feelings 12 years ago when I started in a mobile company.. knew a lot about IP, nothing about fancy 3gpp world.

    It's closed as the witch world, the companies there make billions by making thing obscure even when they are simple as an IP tunnel or an interface name.

    Now things are moving forward: IP everywhere, the standards are more open and published, but still a lot of legacies..

    A simple and rather good handy reference could be an app I found a while ago: NetX (on Android)

  6. Same here, in 2011 moved from IP world of the wireline side where i was working on voip to the mobile side. Big mistake, things I took for granted and were well known practices for previous 10 years never penetrated the mobile world. Even the people managing the mobile voice switches in 2012 never heard of SIP. Like prvious commenters said its a closed obscure and archane world. Its like instead of developing a networking stack from a position and goal of openess it was developed from paranoia. Anyways for people starting out 5g points to a more conventional architecture, but that is 5 years out. For those stuck with 3.5g like HSPA and 4g LTE, best of luck. After 10 successful years in data networking I was out the door in 11 months of mobile/cellular carrier.
  7. Btw all the documentation is proprieatary and behind paywalls. The big names are Nokia and Huawei. The unifying concept is GTP generalized or generic tunnel protocol. Other important topics is real time rating and Online Charging since cellular companies meter everything and dont forget about the importance of the HLR home location register, basically the database that authorizes devices attaching to the network and enforcing policy.
  8. The 3GPP architecture is very well designed. I have also come from generic networking. And I was surprised to the positive side, that in mobile networks they did a lot of things much much better. They were not just talking about things, but they have created working solutions. 3GPP is the most successful standardization body.
    And all this stuff is easy to learn, very logical. You just have to look at with fresh eyes and open mind... :-)
    There are tons of tutorial books and presentations to learn it... :-) NOT the Wikipedia. :-)
    By the way, IMS is also a big success. VoIP done finally properly... :-) Lot of people still deny it, because they are still not able to grasp the ideas. But almost all fixed telco voice networks are moved now, and VoLTE is conquering the world. Even Apple had to surrender... :-)
    So do not give up. It is not trivial, but it is worth to learn it. Understanding TDM, PDH, SDH, SS7, IN helps a lot. In real professions you do not just go for easy recipes, but you really study the history of the trade. You analyze how the decision were done, what failed, and what succeeded and why. And then everything is so logical... :-)
    1. you've skipped the most interesting part, what heavy drugs make everything so logical?
  9. I was in the same boat and found netmanias to have an excellent starting resource.
  10. In my opinion a good point to start with is the understanding of GPRS. This technology added the packet-switched functionality to the old GSM networks. GPRS, EDGE then 3G, 4G etc brought advances to the radio access technology by improving uplink and downlink speeds. The Cisco GGSN devices, for instance support future 3GPP access technologies through simple software upgrades.
    As in the pure IP world there are certain traffic flows that require be very well understood. Knowing how a terminal attaches to GPRS and how a PDP Context Activation is done is key in the initial understanding of this telecommunication world.
    SGSN + GGSN = nodes that support GPRS - represent the core network nodes that provide data capability to different cellular networks.
    Specific telecommunication functionalities are implemented with various interconnections (mostly signaling) between SGSN and other nodes (MSC, BSC, GGSN, HLR etc) and are represented as specific and specialized logical interfaces (Gn, Gi, Gr, etc).
    Both Cisco and Ericson have nice documents that present the overall GPRS architecture (SGSN, GGSN) – as well as their interaction with specific telecommunication nodes. Also the 3GPP specifications provide solid database with specific telecomm standards.

  11. You might as well take a look at the Osmocom project - they are building/providing opensource versions of the components needed for a mobile (core) network:
  12. "IP Design For Mobile Networks" (2009) from Cisco Press is a bit dated nowadays but is a good introduction. Despite its name, is more about mobile networks than IP...
  13. The problem with Mobile or Telco industry per say is they don't have good certifications to begin with. Like if someone want to understand fundamentals of IP network, there are some good starting points like CCNA or Network+. I wish Telco industry has the same at some point.
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