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Bad WDS Throughput

Discussion in 'DD-WRT Firmware' started by DevilStick, Apr 30, 2006.

  1. DevilStick

    DevilStick Network Guru Member


    I set up a WDS bridge between two WRT54G with DD-WRT 23 final (no SP1). When I made a throughput measurement using BRIX tools, I hardly got 2Mbit.

    That is pretty bad. I expected at leased sth. about 40MBit. I used WPA-PSK as encryption, G-only mode and no other wireless clients were connected.

    What reasons could have influenced my WDS bridge? There are 3 other WLANs on chan 6,11,13. My bridge runs on 14. For the test, I had the APs 3m aside from each other but in 2 rooms. Is this to near for testing? Disabling encryption did not speed up the throughput very much.

    Would be nice if somebody could give me some hints how to speed up my bridge.

    --cu DevilStick

  2. Toxic

    Toxic Administrator Staff Member

    how do you expect 40Mbit?

    in WDS mode the bandwidth is halved each time you add a WDS router to the equation.

    since you have two WDS routers the bandwidth is halved.

    (54g = 22Mbps approx)

    so in theory you would have MAX 11Mbps on a direct line of site connection. when you start to add wirless clients to this then they affect the bandwidth as well, dont forget 22Mbps is MAX bandwidth. this 22Mbps is shared between the wirless clients.

    BTW make sure Frame Burst is enabled if you have 102 wireless clients.
  3. DevilStick

    DevilStick Network Guru Member

    I thought bandwidth would only be halfed when adding clients, since the AP would have to communicate with the other WDS device and the client.

    I saw here several threads were this topic has been discussed and I think to recognize that half bandwidth is only used when adding clients to WDS.

    Everything other seems not logical for me. When one client is connected to one AP, I expect the bandwidth to be the complete netto bandwidth of 54MBit (ideal placement of AP, nothing between AP and client)

    So my dedicated WDS bridge without clients should have also complete netto throughput. Otherwise I would have to use one WRT in AP mode, the other one in client-mode (bridged).

    Am I completely wrong?

    I can hardly believe that WDS produces 50% overhead by two devices. With more devices and acting as repeater, it has to receive and retransmit what reduces bandwith. That seems ok, but with two devices there is no wireless retransmit needed, since a wireless received packet travels on wired.

    Using only two WRT router, do I have any disadvantages when replacing my WDS by one WRT as AP and other one in client-mode? (except that clients cannot use both WRT any more to connect and roam what I do not need anyway)
  4. dellsweig

    dellsweig Network Guru Member

    A WDS node is acting as both a bridge and an AP. You bandwidth halving occurs when it re-transmits the signal (AP). If you are only looking for a bridge - use client bridge mode.

    Another thing that may effect your throughput is to insure you dont have any 'B' clients in your network. Your network will drop to B speeds to accomodate.

    I use a combination of WDS nodes, Edge AP's (B and G) and client bridge (for the tivo and some other stuff). My 'backbone' is a wds link. I have 5Mbit cable and have NO problem getting the 5Mbit from my PC's.
  5. hertzsae

    hertzsae Guest

    I believe chans 11-13 all overlap with 14, so try chan 1 for less interferance.
  6. Toxic

    Toxic Administrator Staff Member

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