Slow 54Mbps G network - what are typical speeds?

Discussion in 'Wireless Networking' started by Chris, Jun 29, 2004.

  1. Chris

    Chris Guest

    Hi, i have recently purchased a D-Link DWL-2100ap access point and a
    DWL-G520+ PCI card.

    When i first setup the network the pci card kept droping the link,
    despite having 90%+ signal and 90%+ link quality. I moved the pc into
    the same room as the access point and got 100% signal, yet it still
    dropped the connection and i still had bad transfer speeds (around
    300kbps). Why does it transfer so slowly even though there is a good
    quality link? Surely speed should be relative to signal strength?

    I have changed channels, and found that i get the highest speed on
    channel 11. I read on forums to try us robotics drivers (and yes they
    work! - they are the same card with a different badge on), and are far
    more stable than the D-Link drivers.

    I have now got the speed upto around 14,000kbps peak. To do this i had
    to disable the D-Link "Super G mode". Before i disabled this mode (it
    was in Dynamic turbo mode) i only got ~6,000kbps.

    However, despite having 90%+ signal and link quality i am not
    approaching the 54Mbps limit of the g standard. I appreciate there
    will be some overhead for the network protocols which will take away
    from this theorectical maximum, but over 50% overhead i find extremely
    harsh. I am much happier with this higher speed, but anymore would be

    Can anyone give me some tips to try to increase the speed? D-Link have
    just released a new set of drivers for the card which i will try. I
    dont want to decrease the encryption length (it is currently WEP
    128bit cypher).

    What real-world speeds have people obtained with their wireless
    networks? I would be interested in both 11mpbs and 54mpbs rates. Has
    anyone got these 'proprietry' enchancements working, and do they
    actually increase the performance?

    Many thanks in advance,

    Chris, Jun 29, 2004
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  2. Chris

    Cat Guest

    Cat, Jun 29, 2004
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  3. Chris

    NoNoBadDog! Guest

    On a good day, with a clean signal with little or no interference, you can
    expect to get 22 to 25 Mbps for Super-G and 14 to 18 Mbps with regular 54G.
    In general practice, you will most likely get nowhere near that level of
    performance. the 54Mbs/108Mbs rating is for a "canned" network...two units
    in an electromagnetically sealed room, with xmitter and rcvr only 1 meter
    apart. The numbers are a marketing ply...not what you can expect to ever
    get on your LAN.

    NoNoBadDog!, Jun 29, 2004
  4. Chris

    Brian K Guest

    For SuperG at say 24Mbps (3 MB/sec), is this the speed at which you are
    actually transferring data? Or is it measured otherwise?

    Brian K, Jun 29, 2004
  5. Chris

    NoNoBadDog! Guest


    Your transfer speeds will vary dramatically from moment to moment. For
    short periods you may get a sustained transfer of 15Mbs, and in short
    periods your transfer might rise to 21-24Mbps. You must keep in mind that
    the traffic has to be monitored and controlled, and even though the LAN is
    technically asynchronous, packets must be handled so that they are moved
    efficiently. The overhead inherent in the broadcast signal also plays a
    role in how fast your true LAN speed is, as well as the hardware that is
    being used.

    I realize that you are probably concerned with getting the maximum
    transfer speed on your LAN, but please be aware that you can NEVER expect to
    use the full bandwidth all the time.

    There are so many factors that can affect signal transfer rates that it
    would in literal truth fill a nice sized book. I would not sweat over my
    network running 18Mbps and try to get 20Mbs. It is just not worth it.
    Unless you are streaming audio and/or video over the LAN, just be happy with
    what you have.

    NoNoBadDog!, Jun 29, 2004
  6. Chris

    Brian K Guest

    On my wired network I get transfers of 240 MB/min for large files like drive
    images. What can I expect (as an average) with Wireless G?

    Brian K, Jun 29, 2004
  7. Chris

    Lucas Tam Guest

    ~3 mb/s - Wired networks are still the way to go for file transfers.
    Wireless is fine for work away from the desk or causal surfing.
    Lucas Tam, Jun 29, 2004
  8. Chris

    Ron Bandes Guest

    Signal strength mainly matters relative to "noise," other signals that
    interfere with the desired signal. You don't need a lot of strength if
    there's little interference. Strength can even work against you if you're
    getting echoes or ghost signals.

    Ron Bandes, CCNP, CTT+, etc.
    Ron Bandes, Jun 30, 2004
  9. Chris

    Ron Bandes Guest

    Actually, the 54/108 Mbps rating is the maximum signaling speed, and is not
    intended to be interpreted as a throughput figure. If your wireless adapter
    reports a connection speed of 54 Mbps, then within a single frame you are
    truly sending one bit every 1/54,000,000 seconds. However, not all the bits
    in the frame are your data; some are overhead. Some whole frames are
    overhead. And there is dead time between frames that's more overhead.
    There's also retransmissions due to corrupted frames, and there's frames
    from competing connections. All those things must be subtracted from the
    signaling speed to get the throughput speed.

    Ron Bandes, CCNP, CTT+, etc.
    Ron Bandes, Jun 30, 2004
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