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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?"
..have a tendency to degrade and fail over time.
In my experience power adaptor degradation is the main culprit. Over time the adaptor will provide lower voltages and a less stable current. This translates into a lower signal output and higher noise respectably. I've seen bad adaptor turn repeaters into signal jammers - trust me, that was not an easy issue to troubleshoot...
chinese capacitors.
not kidding. newer gear uses junk parts that the vendor or builder decided to use instead of brand name trustable parts. or, they sought out real ones but got fakes. in electrolytics, its a mostly fakes world ;(
they last a year or a few years, tops. you'll see the cans bulge and burst at the expansion caps, at the top (alum creased areas).
if its on the digital side, you lose all funct.
if its on the analog side (rf, etc) then things can degrade before fully failing. I've seen this in audio gear, too, btw.
cure is to buy known good caps from known vendors (digikey, mouser, newark, etc) and install them yourself. get a hakko desoldering tool, pull out ALL electrolytics and get same LS (lead spacing size) and value caps. try to increase the voltage on them (their rated voltage) as the vendor often gets that part, wrong, in safety margins.
usually, its the power supply that goes bad. and usually its the caps. if you replace your caps, you can convert a $50 consumer throw-away into a $5000 enterprise class gear that will actually out-run most commercial gear simply by using GOOD low ESR caps instead of fakes that almost every one ships with.
panasonic, nichicon, others make good low-esr filter caps. they are a dollar or so, in price. not expensive. not hard to replace.
swap them now or wait for a failure. either way, this is almost always the cause of networking and computer gear these days.
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"Algorithms" aren't going to change because that requires a standard that must be followed by the transmitter and receiver. Unless s/he's upgrading from something like 802.11b to 802.11g, then there shouldn't be any such change. Possible exception would be a proprietary addition, but the problem remains.
It would be interesting to know if, when switching out the router, if s/he changed the frequency it's operating on. There are different bands that can be chosen even within the 802.11g spec, a newer router might have selected a less busy band automatically.
Then of course there's the fact that 802.11n completed changed frequency bands, from the 2.4 GHz region (which is extremely cluttered) to the 5 GHz region, which is relatively empty. That said, the higher frequency would be more impeded by solid barriers, e.g. walls. But it may compensate by higher transmit power, I don't know.
Hard to say if transmit power is really changing without being able to rule out other factors. But electronics do degrade. First suspect I'd think would be cheap capacitors. Poorly designed transistors could degrade, but this seems unlikely as RF band usually uses BJTs. Dust buildup could increase temperatures, which could hurt the efficiency and gain of these devices, but that's a rather long shot.
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I'd wager there are more algorithms involved than just the 802.11 protocol -- that protocol is the top layer in a stack of technology. Before you even get to the part where you are doing any kind of data handshaking, you might have a proprietary algorithm that filters your raw radio signal to weed out interference. There are also implementations of 802.11 on the market with non-standard features. Furthermore there is the inevitable forward march to ever-improving 802.11 standards. 802.11g is really old now. 802.11n is even old news. I've seen gobs of 802.11ac on sale at newegg.com and I don't even think the standard has been formalized. The "algorithms" are absolutely, definitely changing.
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Increasing your WAP broadcast power does nothing to improve signal in the other direction, so while it will make your mobile devices show more bars, it won't actually improve network performance. TCP doesn't work unless a host can both send and receive (packets need to be ACKed), so even if the client receives further away from the WAP, it'll stop getting new packets if it can't notify the sender that those packets were received.
All that really happens when you increase broadcast power is an increase in interference with neighboring WAPs, which tends to lead other people to the conclusion that they also need to increase broadcast power in order to overcome the interference that you created.
Hi. FreeBSD open source wireless developer here. I also work for a wireless company but this is all my own writing and is not endorsed or linked to my employer.
Don't do that. Let me repeat - don't increase TX power from what the card and regulatory limits say you can transmit.
Besides the regulatory limitations, the card may actually degrade if you increase the TX power. You may end up pulling more power than the card is designed or rated at. You may end up causing the output amplifiers to distort, which means you're not only breaking regulatory by spewing noise into adjacent channels, you're actually making your transmissions _worse_. It gets worse with higher transmission rates (especially 802.11n where the higher TX rates have much higher power density than the lower ones) - the Atheros driver implements per-rate TX power limits for this specific reason.
Chances are the manufacturer just has poor cooling, cheap part selection and all of that finely tuned RF front end is slowly degrading as a result. Buy an AP with better cooling or add better cooling yourself.
In fact, if you run the hardware at a _lower_ power output, you may find it lasts longer.
It's not so simple. Let's review the history:
802.11a was first (there is another but obscure predecessor), and used 5Ghz. Advanced modulation techniques blew the doors off 802.11b @2.4ghz, which at 11mbit/s (on a good day), had a very low yield.
802.11g also uses 2.4ghz, but early products had trouble going back and forth between b and g, thus slowing throughput down, despite faster yields in g via advanced modulation techniques.
Enter N, was an advanced modulation scheme with higher throughput, first largely found on 2.4ghz. At first N was really fast, and had only a bit of trouble SLOWING DOWN for b and g. You have one collision domain unless you break out the b/g radio with the n radio. So, you have to dawdle while b goes through, then the channel is free again for something faster.
Then come the dual-band radios, and the dual band, dual radio routers which can walk and chew gum-- and handle paralellizing a 2.4ghz and a 5ghz conversation simultaneously-- major thruput.
The transceivers in the older routers appear to slow down, but in fact, they stay the same compared to newer ones for three reasons: 1) better firmware design that can switch back and forth quickly between protocols (where present) 2) have dual radios for bgn and (maybe a)Highband N and 3) the more recent the device, the more likely it has faster processing power inside the router. The final reason is that your backhaul might be getting faster without you knowing it; DSL gets faster but so also do cable broadband connections. And it's likely the driver in your machine is faster; they change all the time with small improvements, sometimes in real throughput.
Summary: the router didn't change, but newer stuff is faster given the same conditions for the reasons stated.
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