Small cells

Call Quality Complaints Plague AT&T Femto

Some customers of AT&T Inc. (NYSE: T)'s 3G Microcell have reported problems with poor voice quality and dropped calls on their new home base stations, which will be a setback for the devices that are intended to improve indoor voice service.

The voice quality issues are the latest indication that AT&T's Microcell service is off to a bumpy start. The user complaints follow a recent problem with service activations as well as the controversy over the data pricing policy for the Microcell, which is supplied by Cisco Systems Inc. (Nasdaq: CSCO) and uses femtocell technology from ip.access Ltd. (See AT&T Suffers Femto Activation 'Issues', AT&T Defends Data Caps on Femtos , AT&T Enforces Data Cap on Femtos , and AT&T's 3G Femtocells Now in More US Cities.)

But even though users have documented their service problems on AT&T's online user support forum, the operator is not offering an explanation for the latency troubles. In response to Light Reading Mobile's questions about the service quality issues, an AT&T spokeswoman said the operator would not be providing information.

There are recent user discussion threads covering problems with voice latency, dropped calls, and even service outages. Some examples of discussion subjects include "3G Microcell calls rapidly 'skip'" and "microcell dropping calls like its [sic] possessed."

Here's a sampling of the recent user complaints about voice latency:

    The lag is just so bad that I want to return the thing since it's useless to carry on a conversation… That and garbled voice as well at times… Someone suggested we get new sims [sic] on both our iPhones so I am going to try that next week and if it doesn't work... back goes the Microcell.

Others have similar problems:

    I have the exact the same issue with the voice latency, as well as having calls dropped and some static hiss… The latency issue as many have said is extremely annoying especially as my husband was trying to conduct job interviews. We're still within the 30 day return policy and unless this can be resolved soon, it's not reliable enough to keep it.

Some users have gone to the trouble of measuring the latency themselves:

    Roughly between 500ms and 1000ms latency during calls. There seem to be instances, where it is getting less obviously [sic] but the delay is always there… I have been using Vonage for the last 6 years and never had a latency issue, ever (and I run all possible VOIP connection tests that are out there, all came indicate [sic] a good/excellent connection).

There are other users in the discussion groups that report no problems with voice lag or latency, so it is not clear how widespread these problems are or what is causing them.

— Michelle Donegan, European Editor, Light Reading Mobile

joset01 12/5/2012 | 4:30:33 PM
re: Call Quality Complaints Plague AT&T Femto

They mention on the forums that the Microcell uses a new codec. Wonder if that has anything to do with it?

shygye75 12/5/2012 | 4:30:33 PM
re: Call Quality Complaints Plague AT&T Femto

Sounds like the issue of data caps on femtos will resolve of its own accord.

krishanguru143 12/5/2012 | 4:30:30 PM
re: Call Quality Complaints Plague AT&T Femto

The codec could explain the voice quality issue, but when looking at the transfer rate while on a call, it is a high rate.  So they are not using a low bandwidth codec.  It also has to be a codec that is part of the WCDMA standard.  AT&T cannot use a codec that is outside of that.


As for latency, many people do not understand networking at all.  Just because a test is run and it says that it is good for VoIP doesn't mean all that much; the true test would be end-to-end.  Also, some ISP's only have a few peering points and that means a very inefficient path gets used; this adds to the latency due to distance portion.  You also have queue delay, switching delay and serialization delay.  a 1500 byte packet would take 214ms to transmit over a 56kbps link.  A 768Kbps link it would take 15ms.  As you can see, that is a huge difference.  Queue delay is how long it sits in a queue before it gets sent.  Switching delay is how long it takes the switch/router to determine what interface the packet needs to go out of.


Latency due to distance can be a very good chunk of the end-to-end transmission time.  1ms is the equivalent of 160km over copper or 100km over fiber; yes, copper is faster as in the same amount of time it can travel farther.  So 500ms is the same as traveling as 50,000km.


The real question that these people have with high latency is how fast of a broadband line they have and what the end-to-end path distance.


Garbles conversations can also be caused by high utilization.  This can be on the customers side as they are uploading something and using a high percentage of the upstream bandwidth and their router doesn't perform QoS and thus all traffic is created equal.

Michelle Donegan 12/5/2012 | 4:30:22 PM
re: Call Quality Complaints Plague AT&T Femto

The thing that struck me about the Forum user comments is just how technical many of them are, which is a far cry from the "zero touch" provisioning -- where a user just plugs the box in and, presto! it works -- that AT&T and any operator aspires to achieve.


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