Jason, First, before you start reading, get to the latest firmware from Audiocodes (MP118_SIP_F4.80A.034.004.cmp), there have been significant echo improvements in this version. After many days of working with Audiocodes on this problem and much time spent here by multiple technicians trying to reproduce and resolve this issue; this morning, Atacomm received an email from Audiocodes with a full explanation to this now confirmed issue with all MP-11x units. Atacomm will immediately begin work on a KB article within our website that confirms this issue and outlines the manufacturer recommended steps to resolve this problem. Apparently, there have been some changes with the MP-11x's that can negatively affect line noise and echo. Below are some steps which can help to correct these problems: 1. The new design did away with the Coefficent file. Audiocodes, now instead, introduced a configurable parameter called countrycoefficient. This parameter can be adjusted to a specific country based on known configurations. For the most part this should work. 70(USA) is the default value. More can be found in the User’s manual. 2. In just about every case, an FXO is added to a Pre-existing PBX or CO line, you can expect echo. This comes from the fact that delay (IP Network) is being introduced, and what used to be Side tone is now delayed so much it is echo. Just about every difference on the line that can be heard between the pre fxo and post fxo installation can be traced to echo, or line quality issues. 3. Going forward, Audiocodes would like to suggest that when installing the product do the following: A) Make sure the Line coming from the PBX or CO is a Loop Start line. Ground start is not supported on the MP-11x series of gateways. (The M1K FXO will in 5.0) B) Check that the Line can deliver for a 600 Ohm Impedance line -52 to -24 V of Off Hook Voltage -15 to -6 V of On Hook Voltage 20 to 35 ma of loop current. If you know the line is not 600 Ohm, please gather metrics on the line, and the make and model of the PBX or switch it is attached too, plus country of origin. If it is not from the USA, please look up the country of origin and then find the CountryCoefficient to match this. Load the .ini file to the board with this setting and reset. Make sure the Gateway has a firmware version of 4.60.035 or higher or 4.80.030 or higher. C) Put the device on the network with Voice Volume set to 0 and input gain set to 0. Make calls, if there is no issue, you can stop here. However, Echo is still expected most of the time. D) The echo should be heard by the IP side participant as their voice is reflected back. If this is the case, then what needs to be done is to lower the voicevolume (IP—TEL). This way the speaker’s reflected voice will comeback low enough for the ECAN to cancel it out (-6 is usually recommended as the value to plug in here). A little experimentation is needed as the loss for all lines will vary based on length from the CO. Echo is usually taken care of in this manner. E) The incoming speaker from the PSTN’s voice seems low, set InputGainLocation =1, and then slowly increment the Input Gain Parameter(TelàIP) to adjust for this. In past releases (see the note about loads above), the input gain was always applied prior to the ECAN which had the effect of amplifying the returned echo and noise on the line causing crosstalk and clipping issues. This is no longer the case. If the above does not resolve the issues, then you need to go ahead and collect DSP, Ethereal and Syslog traces along with the board.ini, these are to be sent to your support agent, who will then send these to Audiocodes for their engineers to evaluate. This should not happen often. Jessee Holmes Atacomm / Ataractic Corporation www.atacomm.com V: 1-877-700-VOIP Looking for voice over IP products? Visit our VoIP store at http://voipstore.atacomm.com/ On Nov 3, 2006, at 12:14 AM, Jason Kim wrote: Jessee, I tried many combinations of "Voice Volume", "Input Gain" and packetization time , but it's noisy steel. I'm using G.711A-law and packetization time is 20ms. It can be impedance mismatch problem but i cannot adjust impedance of FXO port of MP-114. |
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