Wireless througput on WRT54GL

Discussion in 'Tomato Firmware' started by ymm123, Jun 26, 2009.

  1. ymm123

    ymm123 Addicted to LI Member

    Hi guys,
    When i copy a video file from one wireless pc to another wireless laptop over the wireless network i cant seem to get a higher transfer speed then 1.5MBps. When i transfer a video file from a wired pc to my wireless laptop the top speed is 2.5MBps.

    Is this normal? isn't it supposed to be higher? Isn't it supposed to be around 3 or 4 MBps?

    Ive tried several wireless channels and also other firmwares (i currently use Tomato 1.25)
    extra info: with WMM enabled with "No ACK" i get a lousy 300KBps...

    it does not matter if i have QoS or WMM enabled. the speed stays the same
    As security i use WPA2 Personal AES with MAC filtering. I tried it without security but also got same speeds.
    My router is a WRT54GL 1.1 with Tomato 1.25. The transmit power is currently set to 50 but there was no increase of speed when it was set to a higher level

    The wireless pc Has a realtek RT73 b/g wireless USB adapter
    The laptop has a Intel 3945 B/G WNIC. (both with the latest drivers).

    All computers use Windows Vista Ultimate 32bit

    Can anyone suggest me what to do to increase the transfer speed?
  2. rhester72

    rhester72 Network Guru Member

    That's about right, considering antenna affinity.

  3. mstombs

    mstombs Network Guru Member

    Wireless is half-duplex, only one transmits at one time, so it is normal for wireless to wireless via the router to be half wired to wireless I'm afraid. If everyting Broadcom you may get increase using AfterBurner/Speedbooster and forcing "Wireless G only".
  4. ymm123

    ymm123 Addicted to LI Member

    Hi guys,

    i just uploaded victek's 1.23 tomato mod and my wireless to wireless throughput went up to 1.8MBps...
    Its not really allot but its an improvement and im quite happy about it. now i can stream HD a little more fluently. its not extremely smooth but much better.
    perhaps the author of the official Tomato can implement some of the victek mod's changes...
    its just a thought.
    What do you think?
  5. Kiwi8

    Kiwi8 LI Guru Member

    This is very normal.

    When u are transferring from your wireless pc to another wireless laptop, there is a retransmission made by the access point at the router. Hence the throughput is halved.

    Transferring from wired pc to wireless laptop has no retransmission and thus the throughput is not halved.

    2.5MBps = 20mbps, is very normal for a typical wireless G network. I do get 26-27mbps occasionally but that's only when the surroundings do not have too many other networks or noises.
  6. neoufo51

    neoufo51 Network Guru Member

    Sounds normal to me.
  7. yoda

    yoda Addicted to LI Member

    I tried sftp to device just a bit a go thru wireless
    my transmission rate is between 530-600 Kbps
    using filezilla, however it looks like it kinda jumps drastically
    from 600 to 300 from 3 meters from Ap
  8. ymm123

    ymm123 Addicted to LI Member

    Do you mean 2.5MBps is normal for wireless to wireless?
    I only get this speed when i transfer from wired to wireless...
  9. Kiwi8

    Kiwi8 LI Guru Member

    For wireless to wireless, u divide by 2, which is about 1.25MBps.
  10. TVTV

    TVTV LI Guru Member

    Can anybody please explain in more detail what's the phenomenon because of which wireless B/W is halved when transferring data through an intermediary AP? Thanks in advance.
  11. bripab007

    bripab007 Network Guru Member

    It's not a phenomenon, it's just the way things have to work. Think about it: you've got an AP, the wireless hub, through which all wi-fi transfers must broadcast. This hub has only a fixed amount of bandwidth it's capable of using, and it's got to disperse this amongst the various wi-fi hosts. If one host wants to transfer data to another host, it's got to go through the router/AP, and then retransmitted out to the other host, and, in this scenario, it's only going to have a maximum, best-case figure of 27Mbps (~3.5MB/s) to do so.
  12. yoda

    yoda Addicted to LI Member

    Here is a video clip for the day

    Would this be the same for the WRT54G-TM and Wrt54G guys?
  13. TVTV

    TVTV LI Guru Member

    Thanks, bripa. To tell you the truth, i understood that much. I was really hoping for a more detailed explanation. But i thinks i've finally nailed it:

    1) The 802.11G protocol can only handle half-duplex transmissions. That means that it can either send data or receive data at one given time, it cannot do both at the same time.

    2) A repeater is a device that is used to extend the range of a signal. I am used to radio voice repeaters as i've been a radio amateur for some years. That kind of repeater uses a small ammount of on-board memory to store the voice of the person that has the DTMF code for it, then, after the communication ends, it repeats what that person said over the air. Thus, that kind of repeater can only handle one half-duplex station at a time. So, i naturally thought that a wireless AP works the same way - storing a small ammount of data, breaking the connection with the sender, connecting to the receiver, sending it the data and so on. That would translate to some lag, but it would not halve the bandwidth. But i guess that Wi-Fi APs can handle multiple half-duplex stations at a time, thus in the case of A wanting to send data to B through an AP, an AP can simultaneously receive data from A and send it to B at the same time, thus using 1/2 of the bandwidth for receiving data from A and the other 1/2 for sending data to B.

    Am i correct?
  14. Toastman

    Toastman Super Moderator Staff Member Member


    The APr cannot send and receive at the same time. i.e. while it is transmitting to A it cannot receive from B. Let's say, at full speed/throughput - that half of the AP's time, is spent receiving the data at 54Mbps, and the other half sending it on to a client at 54Mbps. The maximum throughput possible is therefore half of 54Mbps.
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