I am running some problems related to the voice quality of the phones over the mikrotik wireless link. This is my setup:

1 AccessPoint: with 2 Atheros AR5213 (CM9) Sectors Ant.
3 RemoteSites: with 1 Atheros AR5213 (CM9) Directional Ant.
Frequency: 2.4 Ghz
Distance = 0.3 Miles (very close)
Average sensitivity between the sites and the AP: -50 -70 range
Software: Mikrotik 2.8.21
Speed: 54 Mbps 2.4/G-Mode

The link is used for voice and data, but all the data has been shaped to 1 Mbps, 1 phone uses 60 kbps of bandwith, right now there is only a total of 25 phones, 8 phones @ site, and for now the peak is like 5 phones at the same time, sometimes there is bad voice quality and sometimes good quality, with the data there are no problem.

The phones are 3Com 3101 Basic Phone
http://www.3com.com/products/en_US/deta ... u=3C10401A

on the traffic monitor @ AP is always on the 100 kbps - 1000 Kbps range no more than that.

I was wondering is there is some configuration optimized on the mikrotiks for voice comm over wireless links.

Regards,
Fran.

Have you tried upgrading to at least 2.8.22? The changelog states some fixes for 802.11g Atheros (not sure if only turbo mode or "normal" 802.11g, too)...

Apart from that: That your data connections don't suffer doesn't mean much - you won't notice occasional retransmissions of short timeouts with most data transmissions (if things don't get awfully bad). But for voice links every little "hick-up" is evident in degrading voice quality, stuttering, ...

Also, VoIP traffic (in theory) is "bad" traffic for 802.11 links, as you have lots of small packets from voice connections, and the protocol overhead is getting quite big (compared to traffic with "big" packets, like TCP when downloading). But that's nothing you can do anything against.
You could try to activate the MikroTik Packet Packing Protocol, which is designed to reduce protocol overhead on wireless links when transmitting lots of small packets. It does combine several small packets into one big packet before sending if over the air. You have to have MikroTiks at both ends (which you do have). This packing/unpacking at the routers will add some additional latency - I have not tested if this will produce noticable problems for VoIP links.

Just some thoughts...

The link is used for voice and data, but all the data has been shaped to 1 Mbps, 1 phone uses 60 kbps of bandwith, right now there is only a total of 25 phones, 8 phones @ site, and for now the peak is like 5 phones at the same time, sometimes there is bad voice quality and sometimes good quality, with the data there are no problem.

Poor VoIP performance can be caused by jitter, which is variation in latency. If you get ping time that is not consistent within 10ms, you will either have to increase the jitter buffer on your phones or you will have to fix the jitter problem.

Fixing the jitter problem can be as easy as setting the modulation on your radios down to 6mbps, and locking them in, so they can't automatically change on you. If your radio links are constantly changing in speed, you will definitely have variation in latency.

I am using a ZyXel WiFi VoIP phone on the end of a three-hop wireless connection w/ Mikrotik routers. Performance was shit until I prevented the links from auto-changing speed. Now my average ping time (through six routers to the SIP server) is 7ms with jitter is better than 10ms.

At home I'm using a CB3 with a Mikrotik AP on 802.11b. I have a Asterisk server at work, and use a Grandstream ATA-286. We use it all the time to make calls (incoming and outgoing) and it works great.

I'm going to try it in my car soon (we have probably a 3x8 mile area of coverage using sector panels). I've got a 6db omni, 1W amp and a CB3 in my car. Signal works great in most places, I'm excited to try VoIP, I've even contemplated using a 900mhz cordless phone so I can take my phone away from the car.

Hi all and thanks for the help, delay is not the problem, I run 19 Dbi antennas and 100mw radios CM9, and the distance is so close (400 - 600 feet) that I get stable 1 - 5ms delays and 54Mbps all the time.

I made some changes yesterday and for now its seems to work, I activate the protocol that Christian (cmit) told me to do the M3P (The MikroTik Packet Packer Protocol) now I am doing a simple packing - unpacking with an aggregate size of 1000 bytes of all those small packets of 50 - 100 bytes that the phones do.

http://www.mikrotik.com/docs/ros/2.8/ip/m3p.simple

I am not sure what is the optimal aggregate size but it seems that 1000 bytes is quite well, the thing is at the final there will be around 135 phones and peak of 25 phones at the same time.

Thanks to all for the help, really appreciated it.