Voice channels (FTTH, DOCSIS, VoLTE)
I need to verify some claims made by incumbents in Canada that VoLTE data travels on a totally separate channel between the phone and the antenna. Does anyone have links to relevant VoLTE documentation that would provide how VoLTE is provisioned ? I was under the impression that it was more of an "app" on the phone that used the same IP address given for access to Internet. Does the phone get a separate IP and possibly separate VLAN with dedicated bandwidth to ensure voice call quality? Or are all the performance tricks done on land beyond the antenna once the packets are identified as VoLTE, but the phone itself just treats them as a normal app ? I know that for FTTH, there is a separate "channel" where the "POTS" emulation can be provided with its own dedicated IP and bandwidth. Would DOCSIS be the same as FTTH, with the cableco voice service riding isnide the same DOCSIS bandwidth but with pre-allocated bandwidth, or do they allocate separate NTSC channels with a totally separate data pipe ? (in which case, in systems with only 42mhz of uplink frequencies, the voice would have its own NTSC channel on uplink?
On Mon, 21 Nov 2016, Jean-Francois Mezei wrote:
Would DOCSIS be the same as FTTH, with the cableco voice service riding isnide the same DOCSIS bandwidth but with pre-allocated bandwidth, or do they allocate separate NTSC channels with a totally separate data pipe ?
DOCSIS has a possibility to provision unidirectional data flows with certain quality of service characteristics. A pair of these is usually dedicated to a casual Internet connection, another one can be used for layer 2 telephony service, etc. Allocating a whole TV channel frequency would be a big waste. Not even sure it would be possible with standard DOCSIS. Marcin Cieślak
On Mon, 21 Nov 2016, Jean-Francois Mezei wrote:
I need to verify some claims made by incumbents in Canada that VoLTE data travels on a totally separate channel between the phone and the antenna.
Typically it travels on another "bearer" compared to Internet traffic. http://blog.3g4g.co.uk/2013/08/volte-bearers.html Think of bearers as "tunnels" between the mobile core network and the device. They have a lot in common with ATM PVCs in that they can have different QoS characteristics. So the VoLTE bearer can have scheduling priorities that means it'll always be low-latency and highest priority, meaning it might work well when the "Internet" bearer does not. -- Mikael Abrahamsson email: swmike@swm.pp.se
On 2016-11-21 02:53, Mikael Abrahamsson wrote:
Typically it travels on another "bearer" compared to Internet traffic.
http://blog.3g4g.co.uk/2013/08/volte-bearers.html
Think of bearers as "tunnels" between the mobile core network and the device.
Many thanks for the pointer. The fact that VoLTE has its own dedicated APN explains things. I am however a bit confused on the "bearer" term. Say a carrier has spectrum in 700Mhz bands A and B each 5mhz in each direction, bonded together as a single 10mhz (each way) channel. The docunment states: "R.92 requires the use of a particular set of radio bearers" Does this mean that a bearer is given specific spectrum within a block (such as a dedicated colour on a fibre) or that it is just given dedicated capacity on the single data channel formed by LTE compressing all of the spectrum into one big channel ? I though I understood the concept when the name "tunnel" had been mentioned because I understand that a handset estabishes a "hopping" tunnel with local IP which changes as you move from tower to tower, but the tunnel itself maintains a permanent IP connection that remains unchanged as you move from tower to tower. In such a concept, I could understand each tunnel (one to the data APN, one to the IMS/VoLTE APN) having bandwidth allocations. But when the text brought up "radio bearer", I got confused again sicne radio implies breaking the spectrum apart, which would reduce LTE compression efficiency.
On 11/21/16 11:13 AM, Jean-Francois Mezei wrote:
On 2016-11-21 02:53, Mikael Abrahamsson wrote:
Typically it travels on another "bearer" compared to Internet traffic.
http://blog.3g4g.co.uk/2013/08/volte-bearers.html
Think of bearers as "tunnels" between the mobile core network and the device. Many thanks for the pointer. The fact that VoLTE has its own dedicated APN explains things.
I am however a bit confused on the "bearer" term.
Say a carrier has spectrum in 700Mhz bands A and B each 5mhz in each direction, bonded together as a single 10mhz (each way) channel.
The docunment states: "R.92 requires the use of a particular set of radio bearers"
Does this mean that a bearer is given specific spectrum within a block (such as a dedicated colour on a fibre) or that it is just given dedicated capacity on the single data channel formed by LTE compressing all of the spectrum into one big channel ?
I though I understood the concept when the name "tunnel" had been mentioned because I understand that a handset estabishes a "hopping" tunnel with local IP which changes as you move from tower to tower, but the tunnel itself maintains a permanent IP connection that remains unchanged as you move from tower to tower. In such a concept, I could understand each tunnel (one to the data APN, one to the IMS/VoLTE APN) having bandwidth allocations.
the radio bearers described are are the signaling radio bearers. their existence is independent of of the link/mac layer configuration. The mac layer layer (e-utra) exists below the l2 bearers. https://en.wikipedia.org/wiki/E-UTRA these are URBs they are terminated between the UE and the P-GW
But when the text brought up "radio bearer", I got confused again sicne radio implies breaking the spectrum apart, which would reduce LTE compression efficiency. SRB and URB are the l2 presentation of the tunnels established for user and signaling traffic.
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.
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
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) 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 ? When a handset sends a VolTE packet to the "IMS" APN, is there any preferential treatment given between the handset and the antenna ? 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)? 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 ? 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).
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
On 11/21/16 3:12 PM, Jean-Francois Mezei wrote: 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).
On 2016-11-21 21:56, joel jaeggli wrote:
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.
I have read in a number of places that 1 * 20mhz yields much more capacity than 2 * 10mhz for LTE. but... On the other hand, just read something on
https://www.nxp.com/files/wireless_comm/doc/white_paper/3GPPEVOLUTIONWP.pdf
and it states: ## Unlike single carrier systems described above, OFDM communication systems do not rely on increased symbol rates in order to achieve higher data rates. This makes the task of managing ISI much simpler. ***OFDM systems break the available bandwidth into many narrower sub-carriers and transmit the data in parallel streams.*** Each subcarrier is modulated using varying levels of QAM modulation, e.g. QPSK, QAM, 64QAM or possibly higher orders depending on signal quality. Each OFDM symbol is therefore a linear combination of the instantaneous signals on each of the sub-carriers in the channel. Because data is transmitted in parallel rather than serially, OFDM symbols are generally MUCH longer than symbols on single carrier systems of equivalent data rate. ## At page 8: ## In OFDMA, users are allocated a specific number of subcarriers for a predetermined amount of time. These are referred to as physical resource blocks (PRBs) in the LTE specifications. PRBs thus have both a time and frequency dimension. ## At page 9, a table shows that a PRB is 180KHz, and that if you have 20mhz of spectrum, you have 100 PRBs. And more importantly: ## A PRB is the smallest element of resource allocation assigned by the base station scheduler. ## Intertingly, the data I have read in that document points to performance that is linear with more spectrum, no mention that 1 block of 20mhz yields more capacity than 2 blocks of 10mhz. So, if I read this right, (and please confirm if I understand correctly), an LTE system of 20mhz breaks itself into 100 180KHz chunks (a PRB) and the base station then schedules which user gets to use which PRB. So instead of giving each use a time slot, OFDMA gives it one or more PRB, a frequency slot 180KHz wide ? I assume that this is how VoLTE gets priority, with VoLTE bandwidth causing the base station to give the handset enough PRBs to handle the VoLTE connection, at the expense of normal users who will see a reduced number pf PRBs given to them for default data ? Is that how it works ? Would it be correct to assume there is some baseband signalling so the base station tells each user which PRBs it should be listening to (and sending on for the uplink) ? (One piece of text which helped me understand was stating that LTE doesn't transmit packets).
----- Original Message -----
From: "Mikael Abrahamsson" <swmike@swm.pp.se> To: "Jean-Francois Mezei" <jfmezei_nanog@vaxination.ca> Cc: Nanog@nanog.org Sent: Monday, November 21, 2016 2:53:41 AM Subject: Re: Voice channels (FTTH, DOCSIS, VoLTE)
On Mon, 21 Nov 2016, Jean-Francois Mezei wrote:
I need to verify some claims made by incumbents in Canada that VoLTE data travels on a totally separate channel between the phone and the antenna.
Typically it travels on another "bearer" compared to Internet traffic.
http://blog.3g4g.co.uk/2013/08/volte-bearers.html
Think of bearers as "tunnels" between the mobile core network and the device. They have a lot in common with ATM PVCs in that they can have different QoS characteristics. So the VoLTE bearer can have scheduling priorities that means it'll always be low-latency and highest priority, meaning it might work well when the "Internet" bearer does not.
That is congruent with my understanding of how cableco voice is provisioned; it has different rules WRT VoN -- specifically about 911 -- because the cable company segregates it and handles it differently (your cablemodem is expected to be tied to your service address -- or whatever terminal device does the voice). Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://www.bcp38.info 2000 Land Rover DII St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 1274
With MGCP we're just using DSx Qos which is just services classification within the packet cable standard. Still runs over the same docsis network as all other traffic and not separated besides qos side of things. We use a 64K reserved channel to set the call up, after that each call has its own service flow that is QOSed. We also have reserved BW in the CMTS for 911 calls so that they always get through. Where the modem resides in relation to 911 isn't really a factor as we go by services address for the account, a customer could moved the modem to another house across town and it will still work. I know Time Warner has completely separate networks for voice and data, they didn't even reside on the same CMTS from what I understand. Don't know of anyone else doing it that way. Luke Sent from my iPhone On Nov 27, 2016, at 8:49 PM, Jay R. Ashworth <jra@baylink.com<mailto:jra@baylink.com>> wrote: Luke Guillory Network Operations Manager [cid:image1f21cf.JPG@56d24e46.43b1142f] <http://www.rtconline.com> Tel: 985.536.1212 Fax: 985.536.0300 Email: lguillory@reservetele.com Web: www.rtconline.com Reserve Telecommunications 100 RTC Dr Reserve, LA 70084 Disclaimer: The information transmitted, including attachments, is intended only for the person(s) or entity to which it is addressed and may contain confidential and/or privileged material which should not disseminate, distribute or be copied. Please notify Luke Guillory immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. Luke Guillory therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e-mail transmission. ----- Original Message ----- From: "Mikael Abrahamsson" <swmike@swm.pp.se<mailto:swmike@swm.pp.se>> To: "Jean-Francois Mezei" <jfmezei_nanog@vaxination.ca<mailto:jfmezei_nanog@vaxination.ca>> Cc: Nanog@nanog.org<mailto:Nanog@nanog.org> Sent: Monday, November 21, 2016 2:53:41 AM Subject: Re: Voice channels (FTTH, DOCSIS, VoLTE) On Mon, 21 Nov 2016, Jean-Francois Mezei wrote: I need to verify some claims made by incumbents in Canada that VoLTE data travels on a totally separate channel between the phone and the antenna. Typically it travels on another "bearer" compared to Internet traffic. http://blog.3g4g.co.uk/2013/08/volte-bearers.html Think of bearers as "tunnels" between the mobile core network and the device. They have a lot in common with ATM PVCs in that they can have different QoS characteristics. So the VoLTE bearer can have scheduling priorities that means it'll always be low-latency and highest priority, meaning it might work well when the "Internet" bearer does not. That is congruent with my understanding of how cableco voice is provisioned; it has different rules WRT VoN -- specifically about 911 -- because the cable company segregates it and handles it differently (your cablemodem is expected to be tied to your service address -- or whatever terminal device does the voice). Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com<mailto:jra@baylink.com> Designer The Things I Think RFC 2100 Ashworth & Associates http://www.bcp38.info 2000 Land Rover DII St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 1274
----- Original Message -----
From: "Luke Guillory" <lguillory@reservetele.com> To: "jra" <jra@baylink.com> Cc: "North American Network Operators' Group" <nanog@nanog.org> Sent: Sunday, November 27, 2016 10:18:20 PM Subject: Re: Voice channels (FTTH, DOCSIS, VoLTE)
With MGCP we're just using DSx Qos which is just services classification within the packet cable standard. Still runs over the same docsis network as all other traffic and not separated besides qos side of things.
We use a 64K reserved channel to set the call up, after that each call has its own service flow that is QOSed.
We also have reserved BW in the CMTS for 911 calls so that they always get through.
Where the modem resides in relation to 911 isn't really a factor as we go by services address for the account, a customer could moved the modem to another house across town and it will still work.
I know Time Warner has completely separate networks for voice and data, they didn't even reside on the same CMTS from what I understand. Don't know of anyone else doing it that way.
It's my jackleg appraisal -- I'm not an attorney much less an FCC specialist attorney -- that that subjects your service to regulations and restrictions that don't pertain to people who do it the other way; you are simply a VoN carrier, competing with all the other VoN carriers like Vonage; if you *do* give your own traffic priority, then you're violating... title II? Some net neutrality provision that they don't cause they're not *moving the calls* "over the Internet". Cheers, -- jra -- Jay R. Ashworth Baylink jra@baylink.com Designer The Things I Think RFC 2100 Ashworth & Associates http://www.bcp38.info 2000 Land Rover DII St Petersburg FL USA BCP38: Ask For It By Name! +1 727 647 1274
On Sun, Nov 27, 2016 at 9:47 PM, Jay R. Ashworth <jra@baylink.com> wrote:
That is congruent with my understanding of how cableco voice is provisioned; it has different rules WRT VoN -- specifically about 911 -- because the cable company segregates it and handles it differently (your cablemodem is expected to be tied to your service address -- or whatever terminal device does the voice).
I've seen some telco types refer to this as VuIP i.e. "under IP" to differentiate from VoIP such as Skype , Vonage, etc Not sure if this applies to LTE. j -- Joly MacFie President - Internet Society New York Chapter (ISOC-NY) http://isoc-ny.org 218 565 9365
participants (7)
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Jay R. Ashworth -
Jean-Francois Mezei -
joel jaeggli -
Joly MacFie -
Luke Guillory -
Marcin Cieslak -
Mikael Abrahamsson