fontp
Joined: 19 Nov 2004
Posts: 90
Helped: 13
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 28 Jun 2008 13:21 Echo Cancellation in cell phone |
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As source of echo - digital-analog junk only (2-lines-4-lines hybrid) - you needn't consider system delay/ only delay of analog part of system. You don't need match digital delay of GSM system.
As for cell phone You need only cancell local near-end echo (as there is no echo in all-digital 4-line system). Usually 8 or 16 ms delay is used for near-end
g165 echo-cancelling standard specifies 16ms (128 taps at 8кhz) filter.
g168 considers options 16-32-48-64 ms for base-station equipment
With convensional 48 ms trans-continental delays, that should be considered only for long analog links after gateways. This is far-end echo which is never cancelled in cell phone
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