Ask Slashdot: Why Does Wireless Gear Degrade Over Time?

acer123 writes "Lately I have replaced several home wireless routers because the signal strength has been found to be degraded. These devices, when new (2+ years ago) would cover an entire house. Over the years, the strength seems to decrease to a point where it might only cover one or two rooms. Of the three that I have replaced for friends, I have not found a common brand, age, etc. It just seems that after time, the signal strength decreases. I know that routers are cheap and easy to replace but I'm curious what actually causes this. I would have assumed that the components would either work or not work; we would either have a full signal or have no signal. I am not an electrical engineer and I can't find the answer online so I'm reaching out to you. Can someone explain how a transmitter can slowly go bad?"

Comments

Signal isn't chaning, the noise floor is

[Anonymous Coward]

As all of your neighbors add wireless routers, the noise floor goes up, and the usable signal goes down, even though the signal strength is the same.

Re:Signal isn't chaning, the noise floor is

[blackicye]

That wouldn't explain why replacing the router fixes the problem, unless he just happens to be replacing the old router with one that just happens to have a stronger transmitter or better antenna. The pessimist in me says that the chances of that happening can't be 100% of the time.

From my experience with all the major manufacturers of consumer routers and switches, the problem is capacitor quality primarily.
Transmission range and stability will suffer over time because of unstable or insufficient voltage.

Also these devices get really hot these days. Most if not all are passively cooled, and don't even have much real ventilation in their casings.
They're designed to be cheap, and to last for at least 12 months generally.

I've replaced all the capacitors on several Linksys "Business class" Gigabit switch, they all started failing after about 14 months.
I did this to my own switch about 4 years ago, and it's still going strong today. I've also done this on an old Linksys WRT54G.

Re:Signal isn't chaning, the noise floor is

[needsomemoola]

There are 14 channels (frequencies) in 802.11b/g/n (2.4 GHz). There are only 3 that do not overlap though (1,6,11). The best thing to do if you plan to use the 2.4 GHz range is to run something like inSSIDer and see which of those 3 channels are least congested, then set your router to use that range. The problem with 2.4 is the lack of non-overlapping channels, and the fact that most routers have a default setting to pick the "least congested channel" but not conform to the 1,6,11 standard. So therefore you have all your neighbors congesting multiple channels by overlapping 1 and 6 or 6 and 11, using a channel in between. This is a nightmare for high-density areas (I do wireless for large conferences. It's a huge challenge).

In 802.11a/n (5 GHz), there are 23 channels you can use (depending on if you bond for N or not). This is like comparing a 3 lane highway to a 23 lane highway. Your density capacity is FAR higher than 2.4. The downside is that most mobile devices do not have 5 GHz radios, and 5 GHz, because of the nature of the higher frequency, does not penetrate (giggidy) as far as 2.4 (as you said). From a management point of view this is a benefit, but when you are trying to cover a large house it leads to weak signals at the edges of the house, if you center it. This is a good point to use multiple access points though (routers without the routing in lay terms).

So, the near future for wireless is 5 GHz (or, "Wireless A and N"). 5 GHz is catching on (iPhone 5 and a few Androids and Tablets have it now) and will start to get much busier, but the great thing about that is it's designed for it. The downside to the less-near future is that 802.11ac will add larger bonding in the 5 GHz range, which will lead to less available channels/capacity. We'll see how that goes...

One correction to your comment I have is that N is not 5 GHz specific, and it has not at all changed people from 2.4 to 5. It's only allowed more throughput than G or A did on those frequencies. It's caused more problems than not because of the fact it can use the 40 MHz window, taking up 1 of the 3 non-overlapping channels, pissing off your neighbors.

Did the signal degrade, or the noise increase?

[SClitheroe]

Over 3 years I'd imagine a greater density of wifi devices all sharing the same spectrum to have appeared. Perhaps the signal level is the same, but the noise floor has increased substantially, degrading performance.

Re:Did the signal degrade, or the noise increase?

[pepsikid]

NO. If you use channel 2, then you're straddling channel 1 and 6, so you actually have to compete with more interference. Unless you live somewhere with no other wifi neighbors, like out in a desert or 3rd world country, never use anything but channels 1, 6, 11 or 14!

analog transistors age

[jfb2252]

This is a hypothesis based on peripheral involvement with analog and digital RF at 0.5 and 1.5 GHz for twenty years.

AFAIK, the output stage of anything broadcasting above about 2 GHz has to be analog, with the lower frequency signal mixed into a carrier at the higher frequency. Digital synthesizers and chips which can deal with 1.5 GHz directly are still very expensive and are unlikely to be used in the consumer routers. So the final output stage is likely an analog RF transistor.

Analog transistors change characteristics with age at elevated temperature, where elevated is anything over 20C. Implanted ions diffuse with time and temperature, changing junction characteristics. The small structures required by high frequencies are more sensitive to such things.