Does Wi-Fi signal strength affect bandwidth?

I have AT&T DSL. The service offers up to 12mbps. My desktop has a clear line of sight to my wireless router. from the desktop consistently gets around 11.5mbps. When I got to my bedroom, it’s exactly the same distance from the router, but there is 1 wall between my laptop and the router. From my laptop, I usually get around 5mbps. Very occasionally I will test at get 8mbps.

Could this be some type of setting on my laptop, or is that 1 wall cutting my bandwidth nearly in half?

The WiFi protocols are defined to use dynamic rate scaling. So if you have poor signal it will automatically lower your throughput to help manage lost packets and such things. So yes, by design, a low signal connection will be slower than one with a good connection.

In my experience, it’s entirely possible that the wall between is diminishing your throughput that much.

Why not put the laptop next to the desktop and find out empirically that the wall is in fact degrading the signal? (it is)

So the wall is the problem. How do I get my full bandwidth in my bedroom?

You might have a full bandwidth signal but there are going to be a significant number of packets with errors. So your computer has to re-fetch those packets instead of moving on to the next one.

It’s not that simple, though. A weak signal, in the absense of interference, can transmit just as much information as a strong one. The problem occurs because a weaker signal is easier to “lose” in the background noise, meaning dropped packets, etc.

Furthermore, you never get the full bandwidth of a connection – 100baseT might only give you 80mbps even with only two machines directly connected. Collisions, NIC speed, cpu speed, traffic shape/type, and a host of other factors all have an effect on overall bandwidth.

It is likely that the wall attenuates the signal a bit, but it also might be that the downstairs neighbor has a cordless phone under your room, or they use the microwave, or there is RF leakage from your TV, or your laptop wireless antenna is in a noisy spot, or something else.

Like others have said, move your laptop or whatever and see if the wall makes the sole difference, etc.

Also, depending on your wireless router, there is alternative firmware like Tomato that allows you to set your signal strength, so you can boost the gain on your router by about 250%.

As others have said, you can try changing the channel, adjusting your router antennas, or, (if you’re mostly in one direction from the router), add a reflector to it. this link lists all of those and more.

Get something like these. They use your powerlines in your house to extend your network.

Put one plug in a power socket close to your wireless router and connect it directly to your router using a ethernet cable. They put a plug in your bedroom and use a cable to connect that to your laptop in the bedroom.

Aternatively you can try to up the power on your wireless router. I did this by putting 3rd party firmware on it and setting it to 300% (it’s been working fine for a year now)

You can also buy a piece of kit to attch to your present wireless network and extend it, e.g. a Airport express.

Here’s a YouTube link to instructions on how to modify the basic wifi antenna on your router to a “super range extender” antenna. This will provide a benefit in all directions (on the same floor, anyway). I made the modification, and it did help.

There is a fundamantal law of information transfer. This is Shannon’s Law. The information transfer rate can be no greater than the product of the bandwidth of the signal and its signal to noise ratio. Here the signal bandwidth means the range of frequencies the signal occupies, and is expressesed as the width of that range. For 802.11 protocols that bandwidth is almost universally 20MHz. Inside that 20MHz bandwidth the WiFi system uses a range of modulation techniques to get the data through. The signal to noise ratio is just that, the ratio of the signal strength you get at the receiver relative to the noise - where noise is defined as anything that isn’t the signal you want. So noise includes all interference from other devices, microwave ovens, radios, and the ever present thermal background noise.

Between them, that ratio of signal to noise, and the bandwidth of the signal, place a hard limit to the information transfer rate. The modulation techniques used for WiFi adapt themselves to work within that limit. They do this by constantly changing the use of many narrow channels created within the allotted bandwidth. If you drop the signal strength by moving further from the base station the signal to noise ratio will be affected. In the modern world is can go all over the place because you may move closer to, or further away from another source of interference, as well as simply dropping the signal strength. In a perfect world there is a base level of noise that you cannot get rid of, so even here, your signal to noise ratio will fall. Dropping signal strength can never be good.

Note, the use of bandwidth to denote information transfer rate is simply wrong. Very common, but wrong.

Id buy a couple 10db gain antennas for the router. Cheaper than powerline networking and you can return them if the signal doesnt go up as much as you like. Its also worth changing the channel on the router. Netstumbler can help you identify which channels are the least used in your area.

Assuming that the antennas don’t help (and I am not saying they won’t), you can also buy a wireless access point and attach it to one of the ethernet ports on the router (assuming you have these). Then you can place the WAP in your bedroom and get full wireless signal there. WAPs are typically less expensive than full-on routers of similar quality.