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What's the maximum transfer speed you get, (or I can get) for files transfer between two wifi-connected computers ?

Im on computer A trying to copy a big file from computer B, they are side by side (on adhoc network) and I can't get more than 800 KB transfer rate.

Both adapters have relatively the same configuration:

  • Wireless mode set to IEE 802.11g
  • QoS (Quality of Service) enabled
  • Power output set to 100%
  • Rate set to 54
  • some enhancements like Xpress mode, Optimize brandwith are enabled (and they don't make changes)
  • Other settings set to defaults

Is that normal ? if so, what does 54 Mb/s mean ? I should ask : how to get my ~7Mb ?

PS: the computer B Wifi adapter is a USB RTL8187 Wifi adapter.

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2  
The speed rolls off rather fast as signal diminishes, remember this bit. –  Sathya Dec 8 '09 at 14:50

7 Answers 7

up vote 11 down vote accepted

Unless the computers are connected by an ad-hoc wireless network, it is the distance between the computer and the access point that is important.

54 Mbps is a theorical throughput, which is roughly equivalent to 6,75MB/s. So you can expect up to 6,75MB/s as network bandwidth.

But when your are transfering files, the bandwidth is not fully used for transfer because of: - Wireless control frames - Network overhead (IP headers) - File Transfer Protocol overhead - Packet loss - Interference and retransmission

At the end, the best you can expect is around 4MB/s in real transfer rate with light protocol (like HTTP).

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Mb/s means megabits per second. To convert to megabytes, you simply divide by 8, since there are 8 bits in a byte.

So 54Mb/s = 54Mb/s * 1Mb/8MB = 6.75MB/s

So you can theoretically cap out at just under 7 megabytes per second on 802.11g. :)

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+1 for bolding theoretically :) –  Phoshi Dec 8 '09 at 19:46

When working with one router (and this router has only one radio), then the two computers will have to share the bandwidth between each other.

For example, you have 6 MB/s bandwidth. Computer A is using half and computer B is using the other half or can drop to 3 or 2 MB/s.

If you have a multi radio (MIMO) router then the transfer rates can increase. The best scenario for transferring would be Ethernet-router-Ethernet between computers, allowing for either 100Mbit transfers or Gigbit networks with 1000Mbit transfers.

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Slow network file copying in Windows 7 can be caused by Remote Differential Compression.

Remote Differential Compression (RDC) allows data to be synchronized with a remote source using compression techniques to minimize the amount of data sent across the network.

[…]

There seems to be a problem with this Windows 7 and disabling this feature resolves the problem with slow file copy performance.

To disable Remote Differential Compression:

  • Click Start – Control Panel – Programs – Trun Windows features on or off
  • Uncheck “Remote Differential Compression” and click OK.
  • Restart the computer and you should see an improved performance with copying files.
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This source is very handy in comparing the various throughput's of different networking media. As they note, depending on the technology there can be a large difference between the stated raw physical layer speed, and the actual payload throughput.

For 802.11g they list a maximum throughput of 3.1 MB/s

Also, note that 802.11g connections can actually get worse if you place the peers too close to each other. Not all manuals list this, but try keeping both machine at least 20 centimeters apart.

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You describe the transfer between two computers, but please be aware that the data has to travel from computer A to the router first and then is send from router to computer B. If you want to avoid this, than you have to set up a network on the first computer and then join the network with the second computer or use peer networking. And we did not get into details of disk and computer and router speed here...

Also, 54Mbit is the "Marketing Speed", the speed of protocol frames send out, not the speed of the data bits. Rule of thumb is, that the fastest over-air transfer you can get is half the speed, e.g. - where the disk is connected to the router itself is 20-25 Mbit/s - where you have computer - router - computer divide again by two, e.g. 10-12 Mbit.

(File copy on from my USB drive connected to a 300n router yields 5.4 MB/s (43.2Mbit/s))

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I think your router is the limit, I have an old asus 54G (I think it is WL-520) and the max speed is 1MB/s, I tried other router and get 2MB/s. With 54g I doubt you will reach 2+MB/s

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