802.11g and max speed <3MB/s

Discussion in 'Tomato Firmware' started by lanmtl, Jun 14, 2010.

  1. lanmtl

    lanmtl Addicted to LI Member

    Just wondering, why is it that I am getting between 2.6 to 3 megabyte/sec with my Tomato router over a 54mbits connection? I know there are some overheads but that's a lot of overhead here.
    The computer is about 2 metres away from the AP, RSSI is -41 and it says speed is 54mbits.
  2. mstombs

    mstombs Network Guru Member

    You need to be careful with your units, but wireless G is half-duplex which means transmits and receives use the same data channel, only one at at time, and your numbers are to be expected.

    The maximum signalling rate of wireless-G is 54 Mbits/per second. A Byte is 8 bits but there can be a parity bit plus stop bit etc so one way max communication say 5MBytes per second.

    Add in the protocol overhead, headers/ trailers and replies you easily get below 3MBytes per second. Then think about wireless to wireless transfers, and interference and resends...

    Broadcom Afterburner/ Linksys Speedbooster used to claim 125Mbs, later changed to up to 30% improvement which was more measurable. See Toms networking guides for real-world throughput measures.

    The headline figure is only marketing, not a patch on old-fashioned 100Mbps full duplex wired Ethernet which has been able to transmit bidirectionally at up to 100Mbps for the past 10 years - should have been marketed as 250Mbps (2 * 125Mbit/s signalling rate)!

    I suspect the same hype will be true for Wireless N, and the 300Mbit/s adverts will barely overload 100Mbps wired Ethernet, nor tax the 1000Mbit/s wired ports such routers will come with.
  3. lanmtl

    lanmtl Addicted to LI Member

    Thanks very much for the clarification!
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