WirelessMoves

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

I recently had one of those moments again when I realized that what I was able to do just then would have been impossible just a year ago. When I was recently able to download a massive 3 GB file over LTE I needed urgently at 40 Mbit/s while roaming abroad I realized that it was just such a moment.

Continue reading The Power of 40 MBit/s LTE Roaming

I’m quite fascinated by Bitcoins and in a previous post I’ve started to tell what I have learned by taking theory into practice. In the second part I continue the story as there is still a bit to tell about Bitcoin exchanges, market volatility, limitations of the system and how bad guys might be using the system to their advantage. Read on for the details. Continue reading Bitcoin Experiences – Part 2

For me, Bitcoins are a fascinating phenomena. For one thing nobody really knows who created the Bitcoin system initially, it’s a big mystery. Regularly someone claiming to be the inventor of the system comes forward or is suggested by the media but so far nothing was ever proven. A major idea behind the Bitcoin system is to have a method of payment that is independent of state governments. The idea is great and more and more shops have started accepting Bitcoins as a method of payment. Unfortunately, Bitcoins are also used by criminals which receives quite some attention in the press as well. However, in this respect it is no different from any other currency.

While every now and then I’ve read about the theory of Bitcoins I never actually owned or used Bitcoins to pay for anything. With the time of the year coming up at which I make donations to a number of open source projects I decided to put theory into practice and donate to them using Bitcoins if it is offered as a payment method. So here’s the story of what I found out in the process, from practical payment experience to insight into how anonymous the system really is and and why and how crypto trojans can potentially misuse Bitcoins.

Continue reading Bitcoin Experiences – Part 1