3G MicroCell™

[#1]

I successfully installed the microcell yesterday.  The install was very clean, took about 30 minutes from the time I plugged it in to the time I was able to see the cell on my iPhone.

However, both my wife and I notice significant latency when using it for voice.  At worst, it's about 1 second (calls between mobile phones even when one isn't connected to the mcell).  When calling between the land line and the mcell, it's about a half second.

Both of us use iPhone 3G devices.  I don't experience this latency with my vonage VOIP, which is connected through the same switch as the mcell.

Has anyone experienced this?  Any troubleshooting I could do? I'd test latency between to the IP that's upstream from me, but I don't know it.  Could prolly figure it out, but I don't want to bother if anyone else has seen this issue and if there's something easy I could do.  I'm going to go modify the QOS on the mcell's switch port.  If that fixes it, I'll post back...

[#2]

Could you do a few things?

Run an internet speed test from a computer on your LAN.

Tell us about your home network.

Tell us about your broadband service.

Tell us a little about known traffic on the LAN (like xbox live traffic, etc.) when you experience the latency.

Is it constant? Or does it come and go?

[#3]

• Run an internet speed test from a computer on your LAN.

Wired, about 21.5 mbps down, 6.25 mbps up. 

pingtest gives me an A: 5 ms jitter, no packet loss.  25ms latency between here (Hartford CT) and Philly.

• Tell us about your home network.

internet>modem>linksys wrt54g2 v1>mcell

Vonage device is wired the same, but on port 3 instead of 2:

internet>modem>linksys wrt54g2 v1>vonage

• Tell us about your broadband service.

Cable (Cox Communications)

• Tell us a little about known traffic on the LAN (like xbox live traffic, etc.) when you experience the latency.

It's not affected by traffic.  And I have another VOIP box configured identically with same QOS settings on the linksys.  So I really don't think it's network related.

• Is it constant? Or does it come and go?

It's predictable.  If I'm on a call with another cell phone (even one not attached to mcell), voice delay/latency is high (1s).  If I'm on a call with a landline, I'm looking at about a half second.  Latency is present throughout the call (does not vary at all).

[#4]

thanks, this is great info.  FWIW, the MicroCell isnt doing VoIP, so I don't know what the comparison to the Vonage service may prove.

[#5]

Well, it is by definition doing VoIP from the M-Cell to AT&T.  It definitely isn't a circuit switched POTS or ISDN line.

[#6]

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dru858 wrote:

Well, it is by definition doing VoIP from the M-Cell to AT&T.  It definitely isn't a circuit switched POTS or ISDN line.

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No, it's no circuit switched.  It is IP traffic, but it's not VoIP traffic like Vonage.

Vonage uses G.711 codec for encapsulating the Voice over IP.  http://en.wikipedia.org/wiki/G.711

The microcell uses a new standard called IuH, at least until it gets to the gateway, where it is converted to IuPS or IuCS.

[#7]

Well, regardless of the underlying codec it is still VoIP traffic in the traditional definition of VoIP.  I know what you're getting at, though.  Yet it can still technically be categorized as VoIP given that when it goes out over the cloud to get to AT&T's gateway there is absolutely no QoS or prioritization (your ISP more than likely doesn't care, it's all data and will be treated as such to contend with everyone else's) so it is susceptible to the same impairments encountered on the interwebs as say, Vonage.

[#8]

It would prove that the link to the Internet has sufficient quality and and bandwidth to support voice without latency.

[#9]

I have this same problem and posted about it when i first received my microcell last month.

it's very annoying when somebody is speaking, their conversation ends, you start talking and BAM! they are starting another sentence too, so you both end up stopping for a moment and it's like you are both interuppting each other

this happens way too many times and is getting very aggrivating

i have comcast and a VERY fast download/upload speed

[#10]

I have to agree...I have the same issue.  There's just enough latency to cause the "tripping over each other" scenario whenever I'm on a MCell call.  I have a 20/2 cable Internet link, my MCell is connected to a port on my Linksys WRT610N router, and the port is set to high priority  in QoS.  I have no issue with voice "quailty", just that small bit of latency which makes for very annoying calls.  FWIW I also had the same issue when I was using Vonage for my second line so I'm not sure the issue is unique to the MCell.  Regardless, it sure would be nice to be able to elimnate the latency.  The MCell did eliminate the very annoying background hiss I got using Vonage though, so the codec the MCell is using is an improvement over Vonage VoIP.  Still, with a good high-speed broadband Internet link, there's no real excuse for this latency we've been experiencing.

[#11]

Same problem here. Never had a latency problem with Vonage. Running a speedtest.net test from my iPhone on my Microcell yields:

Wifi On: 100ms

Wifi Off (using Microcell 3g): 570ms- yep, this is just enough to make conversations extremely annoying.

I'm using WRT54G router with Microcell MAC address packets given priority.

This is definitely a Microcell problem, and AT&T better fix it pretty quick, or we're back to Vonage.

[#12]

I have a latency problem, as well.  It's even worse when I call someone on a Verizon cell phone.  Bad enough that I hang up and use the landline. 

[#13]

I have finally successfully installed the microcell at work today and there is a large latency on calls using the microcell which appears to be even greater than that using Skype over the same network.  My microcell is setup in the DMZ connected to a DS3 line so I doubt that the internet latency is the whole cause.  Is there some way to quantitatively measure the voice latency so that I can compare it to the IP RTT as measured by "ping"?

[#14]

Hello, check your router for Internet connections.  You should see a session connection using UDP port 500 (ISAKMP/IKE) and 4500 (IKE NAT/Traversal).  This is the connection used by the Microcell station.  You can really "ping" the IP address but if you do a trace route you can at least see what's the latency like in the hops.

Bigbear.

[#15]

I have been experiencing voice latency as well.  Bad enough in which both callers were tripping over each other's conversation.  Very annoying and embarrassing!

I have a D-Link DIR-655 wireless router.  I followed the instructions suggested by AT&T (AT&T troubleshooting guide) for troubleshooting my D-Link router.

I still experienced fairly bad voice latency.  I called AT&T tech support and got in touch with a competent tech.  He verified that I did not have any internet latency.  He preceded to state that in addition to the previous steps followed in the troubleshooting guide, I should also verify these settings on my router:

• Makes sure no packet fragmentation settings are enabled.
• Disable stateful packet inspection (SPI).
• Make sure the following ports are open:

123 (UDP port)
443 (TCP port)
4500 (UDP port)
500 (UDP port)

In addition to the aforementioned items, I also disabled SIP.  This setting is located in the router's Firewall settings tab and is part of the Application Level Gateway (ALG) configuration.

I rebooted the router (and phone for good measures).  I placed a couple of phone calls on my cell phone to a couple of people that experienced (and complained) about the voice latency in previous conversations and they said that I sound a lot better this time.  I am not certain if the voice latency is totally eliminated.  It might exist but at a less noticeable level.

I hope this bit of advice helps.  Best of luck.

[#16]

I'm still unsatisfied with the latency of the microcell, and I'm utterly convinced the Internet itself has precious little to do with it.

Before I explain my methodology, I'll set out the configuration here at my house.

I have AT&T DSL 6M/768K, with a /28 static IP block. My DSL router is a Netopia 3347. I've set it up so that ports 1 and 2 (which normally have the microcell and a vonage box plugged in) have priority over ports 3 and 4 (which have everything else).

With this configuration, the microcell gets a public IPv4 address from the router's DHCP server. No firewall, no NAT. Nothing in the way. And with traffic shaping.

Now, just to see what might be going on latency-wise, I temporarily moved the microcell to a 2nd Ethernet port on my server and set up a bridge. This allows me to watch the traffic go by so I can see who the microcell is talking to. When I have that figured out, I can use traceroute to get an idea where the packets go to get there.

I'll not post the actual IP addresses in question, but suffice to say that apart from a LOT of NTP traffic, really the only other thing going on is an IPSEC tunnel to one host.

Ok, then.

A traceroute from my house to that host takes 9 hops before the traceroute gets firewalled and the latency at that point is a whole 9 msec.

So whatever is causing the high latency, I'm pretty sure it isn't anywhere between the microcell and the mothership.

[#17]

We're getting slight but annoying latency. As someone else said, it's just enough to be constantly tripping over each other's sentences.

The latency seems to be constant, on every call, and does not seem to be affected one way or another by internet usage. That seems as expected since we have the MicroCell connected directly to the modem, i.e. "priority mode."

Our internet is Comcast's Performance Tier. Speed tests on a computer connected directly to the modem via Ethernet indicate 15 Mb/s down, 1.4 Mb/s up.

We do have an old DOCSIS 1.1 modem that I'm going to replace with a new DOCSIS 3.0 modem in a few days. Could the outdated modem be a factor, despite the upload/download speeds being pretty good?

I'd love to find a solution to this. The MicroCell has been a godsend in terms of getting a signal at our house. But the calls are somewhat frustrating due to the latency issue.

[#18]

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pixelmountain wrote:

We're getting slight but annoying latency. As someone else said, it's just enough to be constantly tripping over each other's sentences.

The latency seems to be constant, on every call, and does not seem to be affected one way or another by internet usage. That seems as expected since we have the MicroCell connected directly to the modem, i.e. "priority mode."

Our internet is Comcast's Performance Tier. Speed tests on a computer connected directly to the modem via Ethernet indicate 15 Mb/s down, 1.4 Mb/s up.

We do have an old DOCSIS 1.1 modem that I'm going to replace with a new DOCSIS 3.0 modem in a few days. Could the outdated modem be a factor, despite the upload/download speeds being pretty good?

I'd love to find a solution to this. The MicroCell has been a godsend in terms of getting a signal at our house. But the calls are somewhat frustrating due to the latency issue.

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Latency is based on Hops from end point to end point and is also based on distance from your Mcell to the connecting server.  Your modem and service should not make a difference in this, but the route that your ISP is choosing to get you from your Mcell to the Mcell server and what Mcell server does effect it.  It is very hard to troubleshoot the MCell except for being able to do a packet capture, which would be way more involved than you should have to do.

As for the other individual stating this is not VoIP like Vonage, yes it is.  VoIP is Voice over IP, and since we are all using our ISP to connect the call to ATT, it is VoIP.  The Codec's used may be different but we are all still subject to VoIP issues just as if we were on Vonage.  

Lets just hope that ATT doesn't try to use CoGent in the mix or we could all be screwed. : )

[#19]

I'll add my experience to the mix:

I also have annoying latency on MicroCell calls.  I use AT&T DSL Extreme for my ISP.

I have used other VOIP solutions (even over VPN to my corporate network) and don't experience such high latency.

[#20]

I performed a crude "experiment" to get a sense of the latency.

I was speaking to another person who was on an AT&T mobile phone from my MicroCell-homed mobile.  The experiment is a coordinated count to 10.  I say '1' and when the other person hears me, they say '2', then I say '3' when I hear them, etc.

It was obvious from our little experiment that we are getting over a second of round-trip latency!  I started a timer when I first said '1' and then stopped it when I heard the other party say '10'.  Took over 11 seconds to perform this coordinated count to 10.

Of course there are reaction times to subtract away from the real latency.  For comparison, we did the same experiment except we swapped out my side from MicroCell to a VOIP phone connected via VPN and then to a land-line AT&T phone.

For the VOIP phone, it took 7.7 seconds and for the land-line, 7.3 seconds to complete the count to 10.

[#21]

Does anyone have any thought about the presence of a VPN connection impacting this issue.

I have terrible latency.  I have the Microcell configured in priority mode, so it sits between the dsl modem (ATT), and my router. 

Also has anyone played around with separation of the microcell from the router / modem?

[#22]

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joe_moore wrote:

Does anyone have any thought about the presence of a VPN connection impacting this issue.

I have terrible latency.  I have the Microcell configured in priority mode, so it sits between the dsl modem (ATT), and my router. 

Also has anyone played around with separation of the microcell from the router / modem?

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A VPN connection from a computer on your network should have zero effect on the MicroCell.  

It would probably be a good idea for the MicroCell not to be right on top of a wireless router.  They are in different bands but could possibly interfere.

[#23]

I just had my first real conversation on the MicroCell -- a 15 minute chat.  To me the call quality was outstanding -- very clear.  And I did not sense any issues with latency, the conversation flowed naturally. 

I am going to try it on some work conference calls tomorrow.  If it's all good, bye bye home phone (AT&T U-verse VoIP), hello savings and simplicity (single number and phone to deal with).  

[#24]

Thanks.

I just move the microcell  15+ feet away from the modem and router, so I am going to see how that works.

My DSL ping is 22ms, so I don't think there should be any transport issues. 

[#25]

Another observation:

I notice that the latency increases during the first 15-30 seconds or so of the call.  It doesn't obviously increase much after that, but I may not be hearing it with the simple test I performed.

Test:  land-line phone in the left ear, MicroCell phone in the right ear.  Call is established.  Start saying something.  For the first 15-30 seconds, you can hear what you said in both ears almost immediately (low, acceptable latency).  After 30 seconds or so, you can hear the words in your right ear much sooner than you can hear the words in your left ear.

In other words, the latency is observed on the audio stream from the MicroCell to the public network, but not the other direction.   To my ear, it is at least a half second delay from one ear to the other.  This is very high, unacceptable latency for a VOIP call.

I suppose this could be attributed to insufficient, or throttled upstream by the ISP.  However, I mentioned in a previous post that I use VOIP from other services daily without issue, so I really think this is a buffering problem in the MicroCell service or device.

I re-arranged my network for this test.  The MicroCell is now configured in "priority mode" just to be sure that there wasn't any chance that my local network could be causing any congestion or extra network latency.

[#26]

I just wanted to throw my hat into the ring of people who have latency issues.  I called my home phone and there's clearly a half second or more of delay.  A half second doesn't seem like much but in a conversation it means 1 whole second of perceived silence which usually triggers one or more people in the conversation to talk.

[#27]

Also having this issue. It's really the only issue I've had with the MicroCell–the quality of the audio is good, I get five bars around my entire house, and so for no issues with handoff to the macro network when I leave the MicroCell's range.

I'm on Verizon FiOS and using their Actiontec router. I've tried numerous calls with no other significant network traffic going on, so there's plenty of bandwidth available for the call. Latency in general tends to be very low.

The issue is just enough to make me want to return the MicroCell, if it can't be fixed.

[#28]

I have the same problem.  Roughly between 500ms and 1000ms latency during calls.  There seem to be instances, where it is getting less obviously but the delay is always there.

I have Comcast for internet and Airport Extreme as a router.  I tried every ATT recommended setup, but the only constant is the delay.  Currently I have placed the MicroCell into the DMZ.

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 a good/excellent connection).

[#29]

I used the MicroCell for a team call at work today and I really don't think I can live with the lag time.  It's just too annoying.  I don't know if this solution is going to work for me, right now I don't think so.  

I'm going to call the tech support number and see if there's a fix coming for this issue, and open a ticket.  I'll report back what they say.  

[#30]

Update:  the good news is that there is now an option for MicroCell support in the voice menus for tech support (800-331-0500), and the people who answer seem to know what they are doing.  

The tech who answered found that there were issues already logged and being worked on the latency problem.  The ticket said that it was due to "a high volume of requests to the switch".  So AT&T is aware of the problem and is working on it.  

The open issue ticket also advised them to NOT try the normal procedures which involve sending a reset out through the network, because this would actually make the problem worse.  

I'm going to hang in there for a week or so and see if a fix is forthcoming before I consider giving up and returning the MicroCell.