Jeff, do you mean that operator may impair packets on edge and leave
intact switching to umts?
Dmitry.
On 5/10/10, Jeff Brower <jbrower at signalogic.com> wrote:
> Dmitry-
>
>> As far as I could understand, I was able to configure and
>> compile symbian_ua_gui with TLS, VAS and G729 protocol to work with local
>> Kamailio based server, all communications go through media-proxy, SRTP (on
>> the same local server).
>>
>> In 3G mobile networks, everything works just fine and quality is superb.
>>
>> Now what I see when connecting two entities (Nokia E51) WHEN CONNECTED
>> THROUGH EDGE (the place where both entities were located has *no* 3G
>> access
>> and this was simulated by switching the phones) there is a very bad
>> quality
>> of audio.
>>
>> Either the packets are too big for such a slow connection (you can mostly
>> here about a half of each packet then overlapped by the next one) or my
>> configuration lacks some other vital parameters. It is not like the
>> behavior
>> we hear in GSM connection ("robotizing", "bubbling") - just packets are
>> overlapped.
>>
>> In general, the main problem with mobile networking is that you have a
>> rather wide Inbound channel and very narrow Outbound channel.
>
> And the other main problem is that many carriers block (or impair) voice
> transport over non-voice channels. In that
> case you have to encrypt or otherwise "hide" RTP (and sometimes SIP) packets
> on data channels. Also when you say you
> can "hear a packet" that's impossible because you're talking about 10 or 20
> msec length of time -- less than 1/50th of
> a second.
>
> My suggestion would be to put Wireshark on either side of Kamailio and find
> out what is actually happening to your
> packets. If it's a deliberate impairment you should be able to tell.
>
> -Jeff
>
>> Thus, if at
>> least one entity has wide narrowband (3G, WiFi connected), the other side
>> have clean incoming audio. The tests of the mobile network are the
>> following:
>> 1st entity: 0,22Mbps incoming, 0,07Mbps outgoing.
>> 2nd entity: 0,15Mbps incoming, 0,02Mbps outgoing.
>>
>> According to at least this table (
>> http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml)
>> the link has enough bandwidth to serve one connection. Even 9Kbps each
>> direction should be enough.
>>
>> The questions are:
>> 1. Whether anyone tested symbian_ua_gui or symbian_ua in EDGE phone mode,
>> not 3G or WiFi?
>> 2. What could I check in configuration of pjmedia, pjsip in general and
>> symbian_ua/_gui in particular to make it work on EDGE?
>>
>> Thanks in advance,
>> Dmitry.
>
>
--
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