Digital versus IP Phones

[carpetflyer]

Hello all.

We are looking in getting a new PBX system. We have 15 users in one office.

I have narrowed it down to Shoretel and Avaya's IP Office.

The problem is Shoretel's solution is a IP Phone solution, while Avaya's is a digital phone solution.

I was wondering which one would be better? I know Avaya also has an IP solution, but do you think digital is better?

Thanks!!

 

[mforrence]

Every customer's situation is different. Not knowing anything else, I'd usually go with digital for a smaller single-site location - especially if you already have the cable plant in place. However, the bigger question is - which vendor do you like better? That's the important one...
Mike

 

[carpetflyer]

Hi mforrence.

I really like the Shoretel system but I am worried about sound quality on an IP network. We currently have a hosted VoIP system and occasionally (1 out of 20 calls) we get echo feedback and choppy sound. Our provider said QoS is in full effect.

If we had IP phones in house then connect to a digital T1 trunk would we still experience feedback and choppy sound?

 

[mforrence]

That echo/feedback is an issue with many VoIP systems - most often attributed to a network deficiency. That's why with a smaller system we generally stick with digital because they seem to have less after-install headaches. And they generally cost a bit less. And they have no impact on your network.
Mike

 

[CBasicAsslember]

Echo is due to the interaction of latency and receive side leaking into the transmit side at the far end. When you talk your voice travels to the far end where it leaks into the far end transmit side. It then travels back to you as part of the far ends transmit. VOIP networks try to cancel this leakage by inserting the inverse of the leaked signal (called echo canceling). Echo canceling has it's limitations which you are now experiencing.

The time it takes to make this round trip is important. If the delay is short (less then 20 ms)your brain interprets the returning signal as correlated with the original signal and effectively ignores it. As the delay is increased articulation suffers and eventually results in the echo effect you are now hearing. The echo effect not only depends on the time delay but also on the level of the echo. The reason the problem is almost non existent with traditional TDM systems is the latency is quite short and your brain can effectively deal with it.

 

[donporter]

Managing a VOIP system could be more work then what you are doing today with the digital system. Some of the smaller key systems you can set them and leave them.
The myth is that if you don't go IP then you will not get unified communcations.

 

[carpetflyer]

Right now we have IP phones in place. If i did get IP phones it would be a lot easier to replace than installing digital phones. However I do agree that there would be less headache managing digital phones.

As for the echo and voice chopiness:

Is it bad to assume that since "VoIP" will only be done internally, that we will never experience these problems? Shoretel says we wouldnt experience those problems because "IP" is only done within the office (hence low latency) and once the voice travels through their box, it goes through the PSTN.

I know I can set QoS on our network switch. We currently have one 24 port switch that is doing QoS on our voice VLAN.

Thanks guys!