Wireless file transfer speeds

[calumcousins]

This may sound like a dumb question to some, but its been annoying me a bit.

Quite often, I transfer files between my laptop and PC over the wireless network that they are connected to. However, it always takes ages, especially larger files like music or videos, despite both wireless connections reading 54Mbps on the taskbar.

When transferring files and looking under the Networking tab of the Task manager, it shows that only less than 20% of the network capacity is being used.

Is there any way of speeding this up, or changing anything that will allow this?

Calum.

[JamieBeeston]

Wifi will only ever provide about 40% of the quoted speeds.

I see 2.5MB/sec PEAK from my 54G Setups, usually around 2MB/sec sustained.

Why they bother calling them 54mbit is beyond me (past marketing to 'beat' the 11mbit ones.. which only provide 5mbit and so on..)

J

[bigdods]

JamieBeeston said:

Wifi will only ever provide about 40% of the quoted speeds. I see 2.5MB/sec PEAK from my 54G Setups, usually around 2MB/sec sustained. Why they bother calling them 54mbit is beyond me (past marketing to 'beat' the 11mbit ones.. which only provide 5mbit and so on..) J

Like he said 54 Megabits per second = 6.75 Megabytes per second - from experience I think 40%-50% is easily achievable depending on the connection quality so at 40% this gives you 2.7 Megabytes per second. if you get 2.5 megabytes per second thats about right for a sustained rate transfer. There are 'turbo' proprietary systems that run at 108 megabits out there of course...

Edited to add - make sure you are using a band that isnt also being used by someone close o you as this will slash performance (in my experience) - example my 11mbps B system suddently slowed to a crawl - my neighbours had both set up systems using the same channel (11) as me - seems to be a default on some systems. I moved to channel 6 and its back to full speed.







>> Edited by bigdods on Sunday 16th April 21:30

[aldi]

You need some of this mate: http://j-walk.com/other/wifispray/ind

>> Edited by aldi on Monday 17th April 01:27

[jaybkay]

For various reasons (but mostly because NZ Telecom aren't very helpful), I have to use a 6.5 mile wireless connection to get an internet connection of more than 56k. This wireless connection (Trango) is rated at 10 Megabits/second, Opera shows a speed of around 32/33 kilobytes per second with a 256 kilobit internet connection. Using the wireless connection only to transfer data it runs at 950 kilobytes per second which equates to around 20 minutes per gigabyte and is reasonably close to the theoretical 10megabit/1.25megabyte rating of the Trango units. If your data transfer is taking more than 15 minuts per gig it suggests something wrong - as Windows so helfully says "see your network supervisor"

[malman]

jaybkay said:

For various reasons (but mostly because NZ Telecom aren't very helpful), I have to use a 6.5 mile wireless connection to get an internet connection of more than 56k. This wireless connection (Trango) is rated at 10 Megabits/second, Opera shows a speed of around 32/33 kilobytes per second with a 256 kilobit internet connection. Using the wireless connection only to transfer data it runs at 950 kilobytes per second which equates to around 20 minutes per gigabyte and is reasonably close to the theoretical 10megabit/1.25megabyte rating of the Trango units. If your data transfer is taking more than 15 minuts per gig it suggests something wrong - as Windows so helfully says "see your network supervisor"

I would guess they aren't using WiFi for that link - more likely a point to point system. This will be using a different protocol as its not handling multiple radio clients so won't have WiFi overheads required by the multi client system. Being point to point allow the protocol to have less overhead which will improve the data throughput per packet.

[GreenV8S]

WiFi is a bit unusual because it behaves like a bus based system in many respects but traffic between clients has to go through the hub. I imagine that outgoing traffic from the source to the WAP will be in contention with 'incoming' traffic from the WAP to the destination. I don't know how the contention is managed, but if it is based on collision detection then the link could start to choke at relatively low contention levels. It may be possible to get very high throughput to a single client but I wouldn't be surprised to see this drop off sharply once you have two clients involved.

[bogie]

802.11 is basically like half duplex ethernet through a hub ....all the bandwidth is shared and yes it uses a collision detection mechanism.

Then you have the protocol overhead - take and ethernet frame and add on all the 802.11 headers + 128 bits of encryption etc and you end up with one of the most inefficient protocols for transporting data.

This is why the real throughput is only 40-50% of the data transmission rate (what all manufacturers quote.

This is nothing new - all protocols have a given overhead...but whereas ethernet may be around 5%, 802.11 is 50%

So you want to send 1000 bytes of data, but actually say 1400 is transmitted to transport it at 54Mbps (note bits not bytes - some people get confused with this) etc

so 54Mbps Wi-fi will give at best around 25Mbps which is about 2.5-3MB/s
108Mbps will give around 45-50Mbps which is 6MB/s
240Mbps Wi-fi is the first to equal 10/100 ethernet - at best you can get about 100Mbps through it (12MB/s ish)

all the above are at best, in the same room as the wi-fi access point and will drop off with obstacles and interference

thats just how it is and the limitations of the technology Im afraid

edited to add - then in Windows you have more inefficiencies added if you are running MS networking - so you copy and paste a file from one machine to another, and lose another 20% in overhead ...this is how you can start off thinking you have 54Mbps and end up transferring data at 1MB/s ....then you think you have something wrong when in reality its all working as per spec

>> Edited by bogie on Monday 17th April 16:23

[calumcousins]

Thanks for all your replies... guess im just gonna have to dust off that 10/100 switch then for when I want to do some file transferring!

malman said:

jaybkay said: For various reasons (but mostly because NZ Telecom aren't very helpful), I have to use a 6.5 mile wireless connection to get an internet connection of more than 56k. This wireless connection (Trango) is rated at 10 Megabits/second, Opera shows a speed of around 32/33 kilobytes per second with a 256 kilobit internet connection. Using the wireless connection only to transfer data it runs at 950 kilobytes per second which equates to around 20 minutes per gigabyte and is reasonably close to the theoretical 10megabit/1.25megabyte rating of the Trango units. If your data transfer is taking more than 15 minuts per gig it suggests something wrong - as Windows so helfully says "see your network supervisor" I would guess they aren't using WiFi for that link - more likely a point to point system. This will be using a different protocol as its not handling multiple radio clients so won't have WiFi overheads required by the multi client system. Being point to point allow the protocol to have less overhead which will improve the data throughput per packet.

From the bits I do know about networking, I believe a protocol called WiMAX is used in NZ in a similar guise to that of WiFi (ie: not point-to-point). I could be wrong tho, obviously - was a while ago I was taught about this stuff!

[malman]

calumcousins said:

Thanks for all your replies... guess im just gonna have to dust off that 10/100 switch then for when I want to do some file transferring! malman said: jaybkay said: For various reasons (but mostly because NZ Telecom aren't very helpful), I have to use a 6.5 mile wireless connection to get an internet connection of more than 56k. This wireless connection (Trango) is rated at 10 Megabits/second, Opera shows a speed of around 32/33 kilobytes per second with a 256 kilobit internet connection. Using the wireless connection only to transfer data it runs at 950 kilobytes per second which equates to around 20 minutes per gigabyte and is reasonably close to the theoretical 10megabit/1.25megabyte rating of the Trango units. If your data transfer is taking more than 15 minuts per gig it suggests something wrong - as Windows so helfully says "see your network supervisor" I would guess they aren't using WiFi for that link - more likely a point to point system. This will be using a different protocol as its not handling multiple radio clients so won't have WiFi overheads required by the multi client system. Being point to point allow the protocol to have less overhead which will improve the data throughput per packet. From the bits I do know about networking, I believe a protocol called WiMAX is used in NZ in a similar guise to that of WiFi (ie: not point-to-point). I could be wrong tho, obviously - was a while ago I was taught about this stuff!

Yep they use wimax but my guess is its one of these - not your average wifi access point
www.trangobroadband.com/products/trango_link_10.shtml?id=bb

[thepassenger]

As others have said 40% is pretty good due to protocol specs and such. It's a royal pain in the ass but one of the things I generally do is have a wired 'core' network for anything which is going to push a load of data around (i.e. the PVR, media server, etc.) and only use WiFi for the laptops which don't need mega speeds for day to day stuff.

Obviously I usually leave a patch cable free on the wired switch so that if I want to do a large data pull I just plug in and let rip.

[rdhawkins]

We recently tuned our software to broadcast UDP over a wireless network to laptops. Interestingly to get the best throughput we had to reduce the amount of packets we sent.

It turns out that when a laptop is running from batteries (which in a wireless situation it is likely to be doing) the wireless card/chip on the laptop switches to a sort of burst mode.

It increases the life of the battery by listening for a short period of time and then going off air. The access points know about this and buffer data up ready for the next 'slot'. If you send data too quick the access point starts throwing it away and you end up with too many retries.

Annoyingly the amount of data an access point will buffer before it starts chucking it away depends on the manufacturer. On a Cisco we found it optimal to send data at 24Mbps but on another make it would be something else.

Doesn't help you in particular but I found it surprising when we found out what was going on!