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Thread: VOIP over GPRS

  1. #1
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    VOIP over GPRS

    I am looking at developing a VOIP application for the S60 mobile phones which uses GPRS to send the voice data to a server. I would like to know about the
    1) feasibility of this project
    2) what kind of API s and SDK s( i have the s60 3 rd edition sdk, carrbide j1.5) are needed - are they available for free/open source or do we require any membership
    3) can a SIP server be implemented on a standalone machine without any other infrastructure
    4) How good is GPRS for a VoIP application or do we need to use some other technology such as EDGE

    Pls help me out with regard to the issues I m facing ... Thanks

  2. #2
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    Re: VOIP over GPRS

    Hi niranjancsc,

    I think the main problem with VoIP over GPRS is latency. In my experience GPRS networks often have something like 2 seconds latency. That's a lot of lag on a voice call.

    EDGE is not really an improvement, you could just run higher bitrates.

    3G is better but not brilliant without proper QoS support on the network (not generally available I think), there is still more latency than you'd like - like a really long distance phone call.

    To develop a standalone demo you shouldn't need any APIs that are not public and free. You might need FN Pro membership to get access to APIs to integrate it properly with other phone functionality. In some cases I think the necessary APIs (something to do with audio priority IIRC) may actually restrict the vendor ID to Nokia or Symbian, preventing you from using them all together.

    Hope that helps,
    Sorcery

    P.S. In most cases isn't GPRS data more expensive than a voice call?

  3. #3
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    Re: VOIP over GPRS

    Thanks for your prompt response!
    Apart from GPRS/EDGE what are the other media people use for transferring VOIP data from the mobile phone . One thing I have read about is using bluetooth - but i felt that it is limited to a certain range whereas GPRS would solve that problem .

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    Re: VOIP over GPRS

    Hi,

    At the moment most people are interested in VoIP over WLAN, which is also limited in range but less so than Bluetooth and is more widely available. Nokia already have some solutions for this on some of their latest phones.

    VoIP over 3G (UMTS) is of interest to some but I don't think anyone has it working well yet. The 3GPP standards will have all voice traffic transitioning to VoIP in the not too distant future. Unless you have a specific need or a new business model then I don't see much point in developing a VoIP client for mobile networks, commercially at least. The networks have no reason to give up their voice revenues to anyone else and will do everything they can to protect them.

    In the future there will be a number of other access technologies (such as WiMax mobile) which could be used.

    Sorcery

    P.S. Why would you want to send VoIP data to a server rather than making a direct connection to another user via SIP?

  5. #5
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    Re: VOIP over GPRS

    > 3G is better but not brilliant without proper QoS support on the network

    GPRS gives ping-times from 1 to 2 s here in Germany. So you will think
    that the person at the other side of your VoIP call is a little bit tired
    But it will work using compressed speech. UTMS gives ping-times from
    150 to 300 ms for me. This looks very good to me.

    > To develop a standalone demo you shouldn't need any APIs that are not
    > public and free. You might need FN Pro membership to get access to APIs
    > to integrate it properly with other phone functionality.

    I am confused about that. In older treads in this forum I found at different
    places that I need FN Pro membership and "at least you would need the
    Audio Proxy Server (delivered as SIS file) and Multimedia Media DD in your
    DevCert which is manufacturer grantable capability (APS requires it)".
    Otherwise I have no chance to use full duplex audio and register my
    application to handle RTP/AVP. Is this statement not true anymore ?
    Is there a public way to write my own VoIP client now ?

    Additionally I have read confusing reports about using the build-in SIP
    client over GPRS:

    1. On http://www.newlc.com/Using-SIP-with-...ies60-and.html
    I read that the client on the E61 will connect over GPRS, but that the
    client on the N80ie will not connect over GPRS but only over WLAN. Is
    this true ?

    2. There is a report also on this site and in this forum that the Nokia
    G.729a has a very bad quality. Can somebody confirm this ? Is there a
    solution for that problem available ?

    Further questions:

    What bitrate uses Nokia's AMR-NB codec, if it is used by the build-in
    SIP-client ?

    Is there a way to use the GSM-fullrate/halfrate/enhanced fullrate/
    enhanced halfrate codec inside a S60 device from any VoIP client ?
    I guess GSM codecs are implemented flawlessly in any Nokia device.

    Best regards,
    Andreas

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    Re: VOIP over GPRS

    Hi Andreas,

    I think the ping times are somewhat network dependent. If I remember right the Skype people were seeing about 1 sec ping times on some UMTS networks with their early versions - they still don't have a working public client, except that horrible thing on '3' that uses circuit switched voice call and converts to the skype user ID via a proprietary server.

    I could be very wrong about the standalone demo. I thought the only real problem was that there was already a VoIP client registered on the latest phones, but if you wanted to use GPRS then you could develop on one of the phones that doesn't have VoIP. The APS issue for full duplex audio is still there whatever though. So it would have to be half-duplex VoIP...

    Last time I tried one the N80ie would only do VoIP over WLAN. I don't know about the E61 client though. I thought the E-series devices had a different flavour (different standards implemented) of VoIP client than N80ie??

    I can't really comment on your other questions. All voice codecs sound a bit poor to me, but much the same.

    Sorcery

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    Thumbs up Re: VOIP over GPRS

    Quote Originally Posted by Sorcery-ltd View Post
    Hi,

    At the moment most people are interested in VoIP over WLAN, which is also limited in range but less so than Bluetooth and is more widely available. Nokia already have some solutions for this on some of their latest phones.

    VoIP over 3G (UMTS) is of interest to some but I don't think anyone has it working well yet. The 3GPP standards will have all voice traffic transitioning to Voip Phone in the not too distant future. Unless you have a specific need or a new business model then I don't see much point in developing a VoIP client for mobile networks, Business Telephone System, commercially at least. The networks have no reason to give up their voice revenues to anyone else and will do everything they can to protect them.

    In the future there will be a number of other access technologies (such as WiMax mobile) which could be used.

    Sorcery

    P.S. Why would you want to send VoIP data to a server rather than making a direct connection to another user via SIP?


    This Cheap Voip makes sense to me. I am new to all of this Voip stuff and am very interested in it. Thank you for posting this useful info!

    Eric
    Last edited by ericram; 2009-08-06 at 03:26.

  8. #8
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    Re: VOIP over GPRS

    Quote Originally Posted by ericram View Post
    This makes sense to me. I am new to all of this Business Voip stuff and am very interested in Hosted Voip PBX. Thank you for posting this useful info!

    Eric

    I hope by now you have made the switch to voip because you're crazy if you don't. Huge savings, which is what we all need at times like these!
    Last edited by errirea; 2009-08-06 at 03:24.

  9. #9
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    Re: VOIP over GPRS

    Hi ericram,

    I would add that people/companies are shifting from a WLAN only interest to 3G interest as data bearer for VoIP calls.

    The main advantages for each are:
    WLAN:
    -It saves money (as it is usually free in the office, at home or at the local coffee shop)
    -The network link is good and doesn't introduce too much latency and there is no bandwidth issue enabling you to use the G.711 codec (64kbps) that is of very good quality (better than GSM).

    3G:
    -the ping times are network dependent but for most network I tested, it did not affect the quality of the call.
    -with the new tariff on data plan, it is becoming (will be soon) cheaper to use 3G data for VoIP that make a regular Voice call over GSM with a regular talk plan. If you have an unlimited plan you can use the G.711 codec.
    -the main advantage here is its availability nearly everywhere --> I always use our MobileVoIP client while driving so I keep in touch with colleagues and customers while on the move (they can reach me on my work extension - no need for them to call me on my mobile number and they are sure of reaching me first time)

    The main problem I see with 3G is that for now most operators in Europe forbid the use of VoIP on their 3G data networks (protecting their main revenue stream before they change their business model to data providers from voice provider).

    Regarding VoIP over GPRS, it is possible but needs a codec that consumes a smaller amount of bandwidth such as the G.711 (8kps) and you should expect some delay during the call of 1-2 seconds.

    Benoit Mazuyer
    benoit+forumnokia@pragmaticomm.com
    Pragmaticomm Limited

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