Author: Martin

One reason for referring to 3GPP Release 13 as ‘LTE-Advanced Pro” is that this version of the specification finally has everything in place for Mission Critical Communication, the LTE based successor to 2G TETRA networks designed in the 1990’s and used by public safety organizations in many countries today. One of the first countries that will use LTE-Advanced Pro’s Mission Critical Communication is the UK and a contract has already been awarded to Everything Everywhere. Time to have a look at the specs for Mission Critical Push to Talk (MCPTT), the central feature for public safety organizations.

Continue reading The Specs Behind LTE-Advanced Pro’s Mission Critical Communication

I like going on vacation to Austria. One of the reasons is that I have a SIM card from local operator “Drei” (Hutchison Three) that gives me unlimited Internet access over 3G (sadly not LTE) for 18 Euros per month. In other countries, I had to be bit more careful with my daily data usage while traveling. But at least for Europe things have changed to the better in the past months once again.

Continue reading I Don’t Even Bother With Hotel Wifi Anymore (in Europe)

While I got my first mobile phone at the end of the 1990’s, mobile devices and networks have been around for a bit longer than that. In their book ‘30 Years of Mobile Phones in the UK‘, Nigel Linge and Andy Sutton take a look at the developments over the past 30 years. An interesting title and I obviously couldn’t resist to pick up a copy.

Continue reading Book Review – 30 Years of Mobile Phones in the UK

Most trains these days come with specially coated windows to keep the heat out. Unfortunately these windows also block the RF waves of wireless networks. While most high speed trains in Germany these days compensate for the loss with RF repeaters many regional and inter-city trains don’t come with the luxury. Thus, without really strong network coverage outside, passengers are pretty much sitting in a moving coverage hole. But there seems to be a fix for this now.

Continue reading New Train Windows Against Moving Coverage Holes

3GPP Release 13 finally brings all bits and pieces together for Mission Critical Push To Talk (MCPTT) services, i.e. the cornerstone for Public Safety Communication. I’m going through 3GPP TS 23.179 which contains Stage 2 of the functional architecture description of the service. MCPTT services can be implemented over traditional IP unicast, i.e. a copy of the speech data is sent to each subscriber of a push to talk group call or via eMBMS, i.e. over a single IP multicast transmission to all group participants in a cell. But is eMBMS really needed?

Continue reading MCPTT: Is eMBMS Really Needed For Public Safety Communication?

Just a quick note today about this video over at the Raspberry Pi blog in which Eben Upton talks about the history of the Raspberry Pi. Yes, we are at this stage with the Raspberry Pi now, it’s iconic and it has a story for the history books.

An amazing project and I have stopped counting how many Pis I’m using myself (8 when I stopped counting in 2014), have configured for other people or given away as a present to get others hooked on computing.

It’s a bit sad but unfortunately still true, in some places there is still better GSM coverage than LTE. Network operators using VoLTE thus need to be able to hand-over an ongoing VoLTE call to a GSM circuit switched channel when the user leaves the LTE coverage area. The method to do this is referred to as Single Radio Voice Call Continuity (SR-VCC) and the basic flavor of it has probably been deployed by all VoLTE operators that have a legacy radio network out there. When taking a closer look one notices that there is a surprising variety of states a voice call can be in and the basic flavor can’t handle all of them. Let’s have a closer look.

Continue reading VoLTE – Some Thoughts on SR-VCC

A few weeks ago I updated from Ubuntu 14.04 to Ubuntu 16.04 on my notebook. Was it worth the effort?

Continue reading Upgrading to Ubuntu 16.04 – Is It Worth The Effort?

Continuing my mini-series on how VoLTE works in practice I’ve recently taken a closer look at how DTMF tones are transported over IMS. You might argue that DTMF tones are old technology but they are still used a lot today. Examples are entering the PIN to your voicemail system from the phone or sending a conference bridge ID and password over an established connection. In ‘good old’ analog telephone networks DTMF tones were generated by the phone itself and sent as an audible tone over the speech channel. In GSM and UMTS networks things changed and DTMF start and stop indications were transmitted as signaling messages to be interpreted and converted into a real tone in the network. In VoLTE, things have again been implemented differently.

Continue reading VoLTE – Some Thoughts on DTMF

If you are often dialing into conference call bridges I’m sure you have also more than once wished the ID and participant code would dial themselves automatically. I’ve done this by hand for years and have only recently found out that there’s actually a simple way to fully automate the process.

Continue reading Auto-Dial Conference Call IDs and Participant Codes