This forum includes tips for maintaining the best audio quality possible with the Ooma System. If your Ooma system is having issues with dropped calls, static audio or echo, look here for assistance.
#53400 by dcandmc
Mon Apr 19, 2010 5:58 pm
murphy wrote:No, I meant the signal levels are not the cause of the problem. The modem may or may not be the cause of the problem. The only way to know for sure is to swap it out. You didn't say if you are renting the modem. If you are, you can ask for a new one any time that you want one, within reason.


The modem belongs to me. Before Comcast took over my local cableco, there was an option to buy or rent from the cableco. Comcast discontinued the buy option, so I guess I'll look to Best Buy or Newegg or another retailer. If I see no improvement with a new modem, I can always return it, I guess. Or, maybe I can lease a newer modem from Comcast for a month for $5 and see if that fixes the problem. If it does, I can turn the leased modem back in and then purchase my own.
#53433 by Tiger5353
Tue Apr 20, 2010 12:46 pm
dcandmc there are several problems on the forums were older cable modems were replaced with newer ones and it fixed the jitter problems. I would say as old as your cable modem is the chances are good that this will fix your jitter problems. It could be something else causing this but i would at least try a new modem first before going to something else. ;)
#53438 by Aveamantium
Tue Apr 20, 2010 2:59 pm
If you do purchase a new Cable Modem, get yourself a SB6120 as it is Docsis 3.0. They're a little more than the Docsis 2.0 modems but you'll likely address the jitter problem and will also probably get better speeds as a Docsis 3.0 modem is capable of bonding several channels in both the upstream and downstream direction (Comcast's system only does bonding in the Downstream direction at the current time).
#53444 by tommies
Tue Apr 20, 2010 4:35 pm
One poster had reported that cable lowest tier speed has high jitter rate and packets lost, and after he upgraded to the standard speed tier, the problem is gone.

Yea, it'a dirty trick to lure new customers and then force us to buying up.

PS.
I switched to Comcast recently, and the modem is from Thomson model DHG535. Anyone hear any thing about this modem? It has voip telophony support too, and I see two RJ-11 jacks on it, which I assume it's support two line phone services.
#53450 by dcandmc
Tue Apr 20, 2010 5:45 pm
Tiger5353 wrote:dcandmc there are several problems on the forums were older cable modems were replaced with newer ones and it fixed the jitter problems. I would say as old as your cable modem is the chances are good that this will fix your jitter problems. It could be something else causing this but i would at least try a new modem first before going to something else. ;)


I went out and purchased a Motorola SB6120 from Best Buy this morning, and the jitter problem is gone. Jitter went from 68+ ms (tested with the old modem just before the swap out) to consistently under 5 ms. However, the speed has gone down if anything, and my QOS figure as reported by myvoipspeed is now usually in the single digits whereas with the old modem I was getting 90%. I can pay $8/month more for the next faster broadband tier, but that means that it will take me that much longer to pay off my investment in the Telo and an updated modem.

Why would both my downstream and upstream speed, and the QOS figure, get worse after upgrading to a faster modem?
#53455 by Aveamantium
Tue Apr 20, 2010 6:28 pm
Is your area Docsis 3.0 ready? Check your modem page and see if it has bonded to more than one channel in the downstream direction (or see if the download light is blue).

Also does the cable company know you have a SB6120? They need to send the right config file to the modem...
#53458 by dcandmc
Tue Apr 20, 2010 6:37 pm
Aveamantium wrote:Is your area Docsis 3.0 ready? Check your modem page and see if it has bonded to more than one channel in the downstream direction (or see if the download light is blue).

Also does the cable company know you have a SB6120? They need to send the right config file to the modem...


I don't know if my area is Docsis 3.0 ready, but even if it's not, my speed and QOS shouldn't have decreased, right?

The receive light is not turning blue.

I called the cableco to provide the new MAC address for the modem. I can't remember if I was asked for the model #.
#53459 by Aveamantium
Tue Apr 20, 2010 6:43 pm
dcandmc wrote:
Aveamantium wrote:Is your area Docsis 3.0 ready? Check your modem page and see if it has bonded to more than one channel in the downstream direction (or see if the download light is blue).

Also does the cable company know you have a SB6120? They need to send the right config file to the modem...


I don't know if my area is Docsis 3.0 ready, but even if it's not, my speed and QOS shouldn't have decreased, right?

The receive light is not turning blue.

I called the cableco to provide the new MAC address for the modem. I can't remember if I was asked for the model #.

No, the speed should not have decreased! Go to your modem page then help screen and see what firmware it is running. It should have pulled the latest version (Firmware Name: SB6120-1.0.2.4). Also, go to your signal page and makes sure your stats are good (see my previous post). Lastely, go to speedtest.net and run a speed test (better than the VoIP testing site for speed).
#53462 by dcandmc
Tue Apr 20, 2010 7:20 pm
Aveamantium wrote:No, the speed should not have decreased! Go to your modem page then help screen and see what firmware it is running. It should have pulled the latest version (Firmware Name: SB6120-1.0.2.4). Also, go to your signal page and makes sure your stats are good (see my previous post). Lastely, go to speedtest.net and run a speed test (better than the VoIP testing site for speed).


OK, I called Comcast and spoke with a tech who sounded pretty squared away. He also recommended that I use speedtest.net, and that I make a direct connection between the modem and the PC (router and Telo out of the loop). At speedtest.net, I test consistently at 2.9 Mbps download and .24 Mbps upload. I was also told that my local system is not yet Docsis 3.0 compliant. After getting off the phone, I put the router and the Telo back in the mix, and the speed numbers from speedtest.net remained the same. I went to the help screen at the modem page and the firmware is SB6120-1.0.1.8-SCM02-NOSH. If this is not the latest and greatest, how critical is it to get an update?

What exactly does "QOS" at the VoIP test page measure? This is what concerns me- that my old modem had QOS numbers in the 90s (acceptable for VoIP use), and the QOS numbers for the new modem are consistently in the single digits (unaccaptable for VoIP).
#53464 by Aveamantium
Tue Apr 20, 2010 7:40 pm
Not sure about how important it is to get the newest Firmware but yours is running a pretty old version. QOS at the VoIP site is measuring how consistent your speed is. In other words if it fluxuates then you'll get a bad score. I occasionally get a bad score but it has never caused me voice issues. Jitter is a much bigger problem to solve and it looks like you did that. If you call quality is good don't worry about Qos. As for speeds is the 2.9 down and 0.24 up what you're paying for? If not, and you're not getting help through comcast go here http://www.dslreports.com/forum/comcastdirect and post your problem, "ComcastSteve" will take care of you. If you have the wrong speeds then your modem has the wrong config file (by the way you can't check your config file with a SB6120, only Comcast will know what you have unless it is listed in your logs).

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