tag:blogger.com,1999:blog-17500930.post7315353549854403887..comments2024-03-13T09:40:11.948+00:00Comments on Dean Bubley's Disruptive Wireless: OneVoice for LTE + IMS : Necessary but not sufficientDean Bubleyhttp://www.blogger.com/profile/05719150957239368264noreply@blogger.comBlogger16125tag:blogger.com,1999:blog-17500930.post-12440889968211928342009-12-24T15:14:15.403+00:002009-12-24T15:14:15.403+00:00Why IMS allows cost-savings in fixed domain, but n...Why IMS allows cost-savings in fixed domain, but not in mobile domain?Davidenoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-31690247906199642009-11-14T19:38:36.408+00:002009-11-14T19:38:36.408+00:00Dean,
I based my statements from the findings in 3...Dean,<br />I based my statements from the findings in 3GPP RAN WG2. They claim that fallback to GSM is 1 sec and to 3G 2 sec additional call setup delay. Fractions of a second should occur when you can do a blind handover.<br /><br />The Huawei contribution SA2 contribution you referenced has obviously a different result.<br /><br />Anyhow, my aim was not really to assert the performance of CSFB but rather to claim that a "fallback" to CS is the only rational method when you have spotty LTE coverage.<br /><br />Thus, if Huaweis data is more correct that 3GPP´s, it simply means that it needs to be fixed. One obvious way to do that is the dual receiver method that is used in CDMA. This implies additional complexity in the terminal but if it is ok for CDMA + LTE it should be possible for GSM + LTE as well.Martinnoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-31612151697338309782009-11-13T18:26:16.043+00:002009-11-13T18:26:16.043+00:00Martin
Any evidence to support your assertion of ...Martin<br /><br />Any evidence to support your assertion of fractions of a second extra latency?<br /><br />According to one of the 3GPP submissions I've read:<br /><br />"Rel-8 CSFB to GERAN/UTRAN adds several seconds compared to 2G and 3G native CS calls – between 2 to 4 additional seconds"<br /><br />(from SP-090633 by Huawei and China Unicom)<br /><br />Now obviously I can't validate that separately, so if there's anything contradictory you've seen then I'd be interested in seeing it.<br /><br />As well as user experience, you may also wish to consider the liability implications of adding 2-4 secs to setup times for emergency calls.<br /><br />DeanDean Bubleyhttps://www.blogger.com/profile/05719150957239368264noreply@blogger.comtag:blogger.com,1999:blog-17500930.post-85331707266917358822009-11-13T17:43:39.720+00:002009-11-13T17:43:39.720+00:00Dean,
If you consider the aggressive LTE deploymen...Dean,<br />If you consider the aggressive LTE deployments on 700Mhz in US, I guess that the coverage can soon become good enough such that CS handover would not be an issue. <br /><br />However, for the deployments in Europe and Asia using frequencies above 2GHz, the coverage will be spotty for a long time, in particular indoor. I do not think it makes sense to use VoIP in these scenarios, neither Volga nor IMS. The natural solution would be to use the CS telephony in this case. I.e. to use CSFB.<br /><br />I do not think that the call setup delay from CSFB will be very disturbing. In many situations it will be a fraction of a second. <br /><br />If you are rigth though that this is a major concern, there should be simpler ways to solve that than to introduce Volga and SR-VCC. E.g. to introduce dual receivers in the terminal as will be one option for CSFB in CDMA. Then you get no delay at all as the terminal can do the measurements and repond to the paging on CS as usual.Martinnoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-49224645886168830772009-11-13T13:49:49.624+00:002009-11-13T13:49:49.624+00:00Doug - Nothing to hand, but my expectation has bee...Doug - Nothing to hand, but my expectation has been that any sufficently-large operator would work collaboratively with Skype (or other VoIP players, or inhouse teams) to develop an optimised variant of the software, rather than just using the standard PC or WiFi-oriented version. <br /><br />The precedent here has been the use by 3, using a CS-based Skype client, using ordinary 3G voice, but which hooks into a VoIP gateway.<br /><br />I would expect there to be various ways to optimise codec choice, signalling patterns etc. to optimise Skype (or at least improve it) for HSPA utilisation. <br /><br />All that said, I've got to believe that quite a lot of the 50 million or so PC users with mobile broadband are using Skype - in markets where the MNOs are positioning HSPA head-to-head vs. ADSL it's generally not a realistic proposition to ban its use.<br /><br />DeanDean Bubleyhttps://www.blogger.com/profile/05719150957239368264noreply@blogger.comtag:blogger.com,1999:blog-17500930.post-67266684818015240002009-11-13T13:35:40.789+00:002009-11-13T13:35:40.789+00:00Dean - with your recommendation for operators part...Dean - with your recommendation for operators partnering with Skype, have you seen any good analysis of the resource impacts of Skype over HSPA?Dougnoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-3350434844891822342009-11-13T09:34:44.295+00:002009-11-13T09:34:44.295+00:00Dean, I would say Martin's point about the com...Dean, I would say Martin's point about the complexity of SR-VCC is fair if you are considering a full IMS deployment. In reality handover using SR-VCC for the VoLGA case is significantly less complex in comparison to the VoIMS case. In VoLGA, the procedure invokes a CS to CS handover in the core, not a full IMS to CS handover. There is no IMS domain transfer involved, no service continuity to deal with (as the call is previously anchored in the CS domain) and no new features or modifications needed at the MSC. The MSC performs a CS handover between two cells in the UTRAN/GERAN, the MME thinks it is handing over a VoIP PS bearer to the CS domain, just as in the nominal VoIMS case.<br /><br />In that sense, it enables operators to start with a simpler SR-VCC implementation for handover between the LTE and UTRAN/GERAN some time before they must implement the full network-based transfer functionality with a One Voice VoIMS deployment.Freddienoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-27216150649232021452009-11-13T00:07:24.082+00:002009-11-13T00:07:24.082+00:00Martin
The SR-VCC point is fair, but I'm not ...Martin<br /><br />The SR-VCC point is fair, but I'm not convinced that:<br /><br />(a) *That* many calls will need to fall back to CS from VoLGA. Coverage would need to be pretty patchy for it to happen regularly.<br /><br />(b) Given that much of the time, 3G-to-2G calls still often drop during handover (and they're not that common anyway)... does it really matter?<br /><br />In my view, actually the best solution is not to bother with LTE and just stick with HSPA+. But if an operator *must* move to LTE for some reason, then there needs to be a viable option. Nobody I speak to thinks that CSFB is the least bit desirable - and various have disputed the 2-3 sec worst case, which is anyway far from being the only downside.<br /><br />Personally, I'd rather have an occasional dropped call than a consistently poor call setup time.<br /><br />Anonymous - amusing. I guess that I could claim to have invented the concept behind VoLGA, so perhaps I feel more positive about it. I remember a slide I had in 2006 titled "Salvaging something from the wreckage of UMA" in which I suggested the notion of "2G over 3G"....<br /><br />I've also long advocated operators partnering with Skype or other peers to offer best-efforts VoIP on HSPA, prior to LTE deployment. <br /><br />DeanDean Bubleyhttps://www.blogger.com/profile/05719150957239368264noreply@blogger.comtag:blogger.com,1999:blog-17500930.post-83644936185385028112009-11-12T12:42:42.203+00:002009-11-12T12:42:42.203+00:00Martin, Dean's suggestion makes perfect sense,...Martin, Dean's suggestion makes perfect sense, if you <i>don't assume</i> Dean to be an impartial observer in matters related to VoLGA.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-12148555255045952802009-11-12T10:25:14.216+00:002009-11-12T10:25:14.216+00:00@madmax: I think one of the points that Dean was m...@madmax: I think one of the points that Dean was making in the OP was that there will certainly be operators who will deploy early LTE for data but who will not be ready or able to invest in a full IMS/VoIP network when they need to deliver a voice service, even if products are available at that time.<br /><br />Those operators will likely need some form of interim solution for voice over LTE.Freddienoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-118617828036864822009-11-12T09:55:44.249+00:002009-11-12T09:55:44.249+00:00@Martin: My point is that if you are going to impl...@Martin: My point is that if you are going to implement SR-VCC for VoIMS anyway, then doing it for Volga 1st is not incremental to the VoIMS plan - it is a necessary condition. Whether it is a complex implementation or not is something that must therefore be addressed by 3GPP for VoIMS mobility anyway. I suspect the same considerations were present in the GERAN to UTRAN transition too (islands of UTRAN) but somehow we managed ...<br /><br />Perhaps a more immediate issue is that of signaling load. Call setups in GERAN/UTRAN generally have no impact on the HLR. With CSFB, HLR load is directly proportional to the number of CSFB calls made in the network - every single MO or MT call attempt (whether successful or not) requires multiple HLR transactions (according to the CSFB procedures with or without PS Handover). Do you consider that operators have understood the implications of this?Freddienoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-36602002830090908252009-11-12T00:12:28.986+00:002009-11-12T00:12:28.986+00:00People seem to ignore the fact that early LTE depl...People seem to ignore the fact that early LTE deployments will be data-only in which case SMS-over-SGs will suffice for SMS delivery. Voice services will eventually follow by which time, IMS based VoIP will be ready for commercial deployment. One-Voice initiative will fast-track it.Madmaxhttps://www.blogger.com/profile/00816924392422212567noreply@blogger.comtag:blogger.com,1999:blog-17500930.post-79011619677044985952009-11-11T23:52:54.698+00:002009-11-11T23:52:54.698+00:00No, 2-3 sec additional call setup is worst case. T...No, 2-3 sec additional call setup is worst case. The expected average should be less.<br /><br />Do you think the Volga SR-VCC handover to CS should be without disturbance then? <br /><br />If the LTE coverage is spotty it makes sense to start the call on CS directly. A large portion of the calls will end up there anyhow.Martinnoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-92049201601545946962009-11-11T16:38:53.679+00:002009-11-11T16:38:53.679+00:002-3 secs looks more like the expected average, not...2-3 secs looks more like the expected average, not worst-case for CSFB. And double it for an LTE-to-LTE call, I presume?<br /><br />Making your core services worse for your best customers (ie those buying the first LTE smartphones) is hardly a good strategy for retention.<br /><br />And I'd love to be a fly on the wall when someone tells Steve Jobs that worsening the user experience of making a phone call, is an acceptable price for higher theoretical-but-unachievable data rates.<br /><br />DeanDean Bubleyhttps://www.blogger.com/profile/05719150957239368264noreply@blogger.comtag:blogger.com,1999:blog-17500930.post-24754340928272412252009-11-11T16:21:38.756+00:002009-11-11T16:21:38.756+00:00If viewed from another direction, then perhaps you...If viewed from another direction, then perhaps your point actually underlines a strength of Volga compared to CSFB: Volga has very similar requirements to VoIMS in the E-UTRAN/EPC (including RTP/IP transport <i>and</i> SR-VCC)and so closely aligns any investment with an operator's longer-term IMS planning. I'm not sure that there is any part of CSFB for which the same statement could be made.<br /><br />Also, I know 2-3 secs of extra call setup delay doesn't sound like much, but in my experience some operators would rather sell their respective grandmother's into slavery (so to speak) before adding 2-3 seconds onto call setup times compared to the current UTRAN/GERAN case (especially for mobile-to-mobile LTE calling). I think I read VoLGA call setup times should be even lower than UTRAN, which is really how it should be with 4G vs 3G, or even 2G technology, not the other way around.<br /><br />Besides, operations staff are measured on these KPI's, you know! :-)Freddienoreply@blogger.comtag:blogger.com,1999:blog-17500930.post-65161914325803810832009-11-10T22:55:43.990+00:002009-11-10T22:55:43.990+00:00I cannot understand your suggestion that Volga sho...I cannot understand your suggestion that Volga should make sense as an intermediate step. Just as IMS, Volga is VoIP on LTE but with a different control channel. <br /><br />Considering the non-homogenous LTE deployments that will be the reality for still some years, Volga needs SR-VCC to provide handover to the CS access for a substantial portion of the calls. Otherwise the call drop rate will be unacceptable.<br /><br />SR-VCC is quite complex and puts requirements on most of the LTE/EPC nodes as well as on the MSC. Admittingly, CSFB has an issue with worst case some 2-3 secs call setup delay but compared to SR-VCC it is a very simple feature.<br /><br />Also, as the combined mobility management and the SGs interface will be deployed already for SMS to data cards, the incremental step to also send the paging over that interface is very small.Martinnoreply@blogger.com