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Voice Standards -RTD

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  • #22229 Reply
    Thomas
    Guest

    I am looking for the standard that describes round trip delay in voice networks – I saw an article on this website awhile back which stated that the standard foe voice is 300ms RTD and 150ms one way can anyone please direct me to this standard, If anyone has anything on satellite delay please let me know – normally a transponder would produce a 500ms RTD across the transponder but there are allot of variables to this value, thanks

    #22230 Reply
    sat man
    Guest

    The RTD imposed by a satellite depends on a number of variables. Latitude + longitude of earth station, angular position of satellite, along with the radius of the orbit and the speed of light which are fixed, gives you the RTD, which will be approx 500ms. Other delays in VoIP are introduced in encoding, decoding, jitter buffers, router delay etc. The trick is to keep these to an absolute minimum since the satellite delay can not be reduced without breaking laws of physics. Voice quality is measured in MOS which takes into account various factors including delay. I don’t know of any standard limit for voice delay, but it starts to get noticeable if you go more than 300ms one way delay, some international carriers use this as a limiting figure. Remember international phonecalls over traditional TDM have always used satellites….

    #22231 Reply
    Tony Friar
    Guest

    Thomas,

    ITU-T recommendation G.114 advises that one way delay should be less than 150ms.

    If memory serves me correctly it
    says something like 0-150ms one way delay is adviseable. However
    150-400ms may be acceptable for
    some applications. Anything above
    400ms is unaccpetable.

    regards

    Tony

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