In the previous blog post on VoLTE I discussed how speech codecs are negotiated during connection establishment. VoLTE uses the AMR and WB-AMR codecs that are adaptive and can encode the voice stream in several data rates and qualities. In the case of WB-AMR, voice streams can be sent with data rates between 6.6 and … Continue reading VoLTE – Some Thoughts On Bandwidth Negotiation
In the good old fixed line SIP world, the originator of a speech call told the other side which speech codecs it supported. The other side then picked a suitable codec and informed the originator about the choice. That was it and things were ready to go. In VoLTE, you might have guessed, it’s not … Continue reading VoLTE – Some Thoughts On Codec Negotiation
Most services on the Internet make use of a single TCP or UDP connection. The client opens a TCP connection from a random port to a well known port on the server (e.g. port 443 for HTTPS) and performs authentication and establishment of an encrypted session in that connection. Simple! In VoLTE, however, things are … Continue reading VoLTE – Some Thoughts On Port Usage
When I first came across the VoLTE service registration process I was a bit baffled why it is split in two procedures. The reason for my confusion was that in the circuit switched world there is only one process, a “location update”. Once done that’s it and the mobile can go back to sleep. In … Continue reading VoLTE – Some Thoughts About Register vs. Subscribe
In the good old fixed line SIP world things are straight forward when a SIP user wants to call someone: INVITE, TRYING, RINGING, OK and you are there. In the VoLTE world things are a bit more complicated as the service tries to replicate the circuit switched telephony service. Here, a media stream can already … Continue reading VoLTE – Some Thoughts On Early-Media
In Ocotober 2015, NTT Docomo was the first network operator who has started VoLTE Roaming based on a pre-standard implementation of the S8 Home Routing (S8HR) concept. I wrote about it at the time and speculated how they might have implemented the service as there was little official technical documentation available. In the meantime, 3GPP … Continue reading VoLTE Roaming – S8HR in 3GPP S8HR TR 23.749
Back in July this year I had a post on a GSMA and 3GPP initiative to think about a simpler VoLTE roaming approach. Instead of the quite complicated VoLTE roaming with local breakout, some members of the two fora openly pushed for for a much simpler solution called S8 Home Routing (S8HR). For the details … Continue reading Docomo Doesn’t Want To Wait And Launches S8HR VoLTE Roaming On Its Own
Many network operators these days are trying to get their VoLTE system off the ground in their home countries so perhaps by 2016 we'll finally see a significant number of networks using the system beyond the few that are silently up and running today. While VoLTE at the beginning will only work in the subscriber's … Continue reading VoLTE Roaming – From RAVEL to REVOLVER
VoLTE certainly is an 'interesting' beast and continues to occupy the minds of thousands of engineers to make it work in networks around the globe. I wonder how this monumental effort stacks up against other VoIP services such as Facetime, Skype and others that are centrally managed!? That probably costs a lot less money and … Continue reading VoLTE: The Locality Advantage
Do you want to learn about VoLTE but you are not sure where to start? If so, here's a tip for you: Learning how VoLTE works in a reasonable amount of time is not an easy task, there's just so many things to learn. Reading the 3GPP specifications to get up to speed as a … Continue reading Book Review: Voice over LTE (VoLTE)