Voice channels (FTTH, DOCSIS, VoLTE)

joel jaeggli joelja at bogus.com
Tue Nov 22 02:56:38 UTC 2016

On 11/21/16 3:12 PM, Jean-Francois Mezei wrote:
> On 2016-11-21 15:18, joel jaeggli wrote:
>> SRB and URB are the l2 presentation of the tunnels established for user
>> and signaling traffic.
> OK, so wth LTE, if carrier has 10mhz up and down, this represents a
> single chunk of spectrum providing one pipe ? (in fibre terms: a single
> light colour through one strand)
Not really the air interface uses OFDMA coding scheme, so it is both
divided into sub-carriers from 1.4 to 20mhz wide which are then also
scheduled accordingly.
> The "smoke and mirrors" is accomplished by having different tunnels
> inside that one pipe, with some tunnels granted QoS or other
> preferential treatment between the IMS/VoiP servers and the RAN ?
you kinda want you qos policy to apply end-to-end in the carrier
network, not just on the ran.
> When a handset sends a VolTE packet to the "IMS" APN, is there any
> preferential treatment given between the handset and the antenna ?
sure, hence the qos policy template on the radio bearer.
differing numbers of subcarriers and slots can be assigned to UE based
on the services they are using.

>  Or
> does preferential treatment begin at the RAN where the packet is
> recognized as going to "IMS" APN and going on the fast track to it ?
> or put another way. If everyone uploads a HD selfie movie at the same
> time, are handset uploads slowled with normal TCP flow control (drop a
> packet, no ack received, handset halves the TCP window size)?
Those flows going to have the best effort policy. but yes it is
reasonable to presume that in the event of congestion the best effort
queue will be preferentially dropped. likewise if you have voice and
data going at the same time they are not strictly speaking competing for
resources, because the volte radio bearer has a resource assigned to it
and the and the ip data bearer has a resource assigned to it.
> In other words, some router near antenna, to prioriotize packets to the
> IMS/VoLTE server, will flow control normal IP traffic to maintain
> sufficient upload capacity for VolTE traffic ?
> Or are the tunnels fixed in capacity such that unused capacity in one is
> never used by the other ?
> From a policy point of view, if I propose a net neutrality policy, I
> have to make sure it doesn't prevent normal VoLTE functioning, while
> preventing abuse of the ability for an incumbent to prioritize/zero-rate
> its own services.
> For instance:
> AT&T in USA zero rates voice but not video calls over VoLTE.
> Rogers in Canada zero rates both voice and video calls over VoLTE.
> So if VoLTE video travels to the same IMS as voice, and not through the
> normal IP APN, that means AT&T has to count the video traffic separately
> and add it. But if Video goes through the normal IP traffic APN, it gets
> counted fairly, like Skype packets, but Rogers then captures that
> netflow and later deducts it from the total usage.
> The issue here is that VoLTE is the new kid on the block with video
> capability and incumbents can use their power to displace competitors
> such as Skype/Facetime and that may constitute undue preference, unless
> the standards are such that they have no choice because that it how it
> has to work. (But AT&T shows that it can still count video and treat
> video calls fairly compared o skype video calls).

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