Have posted something along this line to 24support, however, I've given things more thought so perhaps someone here can advise. I need to boost a wireless signal as the belkin modem/router won't reach the top of my house. Is there something I can install wirelessly in the middle to boost the signal. I have been reading the manual on (say) the DWL-G700AP and it looks like it needs to be hardwired (or am I mistaken). Help appreciated.
Thanks for that, more research following from your suggestion leads me to this - it looks like exactly what I need, a comprimise between wireless & powerline (as I have 2 wireless laptops needing a stronger connection). (if anyone thinks I am mistaken, please tell me).
NetGear 54 Mbps Wall-Plugged Wireless Range Extender Kit
This idea of powerline networking looks very interesting, but I noticed that both companies and the op are from the UK. I'm not sure but I think their powerlines are different from those in the US. Do these devices work in the US also?
Powerline IS a great solutoin, but if your question is "how do I get the signal to reach the top of my house", then consider the antenna side of things first.
Consider that your antenna probably has a donut- shaped pattern and depending on location and position your upstairs may be in the "hole", not the donut. Turn the antenna toward the horizontal to send the signal upward and see if that helps.
See if you can move your router/AP upstairs or to the middle of the house and again, experiment with different positions for the antenna.
Consider a higher gain omni antenna. Radio Shack has 'em. It's stronger, but the donut gets flatter, more like a disc as the gain goes up.
Or you could use a panel antenna from one end of the house and point it to cover the rest of the house.
The signal coming from your stock antenna is shaped like a donut slipped onto the antenna. You want it broadside to the target, not pointing end-on, like might be typical if the downstairs antenna were pointing straight up.
You might try a simple reflector.
EZ-12, printed on photo paper for thick stock, with aluminum foil glued to the sail, provides a substantial boost in signal.
The signal with the reflector is not only 13dB stronger, it's more stable.
With 54g connections, I find that watching the "current bandwidth" in the Windows perfmon.msc is a pretty good signal indicator. start-run-perfmon.msc + Performance Object = Network Numbers agree with dslreports. + Performance Object = TCP "current bandwidth"
If you run Remote Desktop or VNC, you can monitor the remote signal strength from a PC near the router while repositioning the antenna at the router. Monitoring the remote screen moves enough data that the performance monitor will show reasonable data.
It may be that the signal with the reflector is at the upper limit of what Netstumbler will display, but the signal reading provided is steady. without the reflector, there are fluctuations in the signal level.
I don't bother installing manufacturer client software, if that's what you mean. I think perfmon is adequate, and it's already there on WinXP, not something that has to be added, learned, or preferred.
Close, methinks I have a better guess. I've also noticed that directional antennas are more stable (less variations in signal pickup versus time). My guess(tm) is that an omnidirectinal antenna picks up far more reflections with longer delays than a unidirectional antenna pointed directly at the signal source. Less reflections means less reinforcements and less cancellations, which means it's more stable.
No opinion, but I have an alternative. At a given signal strength, thruput and speed are inversely proportional. If I lock down one, signal strength becomes proportional to the other. Instead of measuring signal strength, which tends to be rather erratic, I like to measure thruput. I lock the speed to 54Mbits/sec, ignore the signal strength, and measure megabits/sec thruput using Iperf.
I don't really know if this is the superior method, but it does have 2 advantages:
It does the measurement with traffic. Measuring signal strength without any traffic moving results in some bizarre numbers. For example, I know one wireless client (name withheld due to internal politics), that always resets its indicated speed to 54Mbits/sec when traffic stops even momentarily.
It takes into consideration any interference and reflection effects. Interference has no effect on signal strength. However, it has a huge effect on data thruput.
On the down side, it's kinda hard to make pretty looking antenna patterns using data rate instead of signal strength. Oh well.
Back to working on taxes. Don't post anything interesting or I'll never get this [deleted expletive] done.
On Sat, 24 Mar 2007 17:47:47 -0700, Jeff Liebermann wrote in :
Another downside is that it doesn't tell you much that's useful, much like diagnosing a car problem just by seeing how fast it will/won't go. If you find the car won't go over 35 MPH, you still have no clue as to why. That's part of why I'd rather look at the actual data, just as I would with a car, instead of just measuring data throughput. Another part is that throughput can be adversely affected by things other than the wireless connection; i.e., there is no real test control.
I beg to differ. The conventional method of measuring signal strength and SNR are usually done with NO traffic moving on the networks. All that will tell you is if the link is capable of delivering the expected data rate, not whether it actually does. For example, the presence of interference might affect the SNR, does not affect the signal strength, and will seriously affect the thruput. The measure of thruput (at a fixed connection speed) as compared to what might be expected, is a great indication of how well and how reliable the system will be. For example, if I lock the wireless data rate to
54Mbits/sec, and my IPerf benchmark yields 25Mbits/sec, I can safely say that everything is working. However, if I get considerably less than 25Mbits/sec, I would go looking for retransmissions, interference, or a sick computah. You don't get such clues from just the signal strength and SNR.
In addition, today's modern all digital chipsets do not really measure the IF (intermediate frequency) analog signal strength as they did in the daze of Prism 1 chipsets. There's simply no analog signal available to measure. So, they fake it using the error rate for SNR and the thruput for signal strength. It's actually a fairly good way to do it if the manufacturer adheres to the reference design. If not, the conversion factors need to be calculated for the specific implementation.
Nice article on "Understanding WLAN Signal Strength":
She doesn't cover the conversion problem, but does cover the basics and supplies a good list of WLAN tools.
Oh, like a dynamometer? That's exactly how it works. Floor the pedal almost to the metal, and supply some frictional resistance on the rear wheel rollers. The amount of resistance is a measure of delivered horsepower at a given RPM. The lack of wind resistance makes extrapolations such as gas mileage a problem (which is why the sticker MPG is always higher than reality). However, it's really good for troubleshooting engine and drive train problems.
Sure I do. If I limit myself to only using speed as a criteria for performance, I certainly will have no clue. However, the instrumentation offers considerable other useful input. For example, acceleration, gas mileage, weird noises, smoke out the exhaust, operating temperature, etc.
Using performance parameters to troubleshoot automobiles and wireless systems are very similar. The only real difference is that with an automobile, you can usually see, hear, smell, and otherwise sense performance parameters. With WLAN, you can't see RF, so you gotta use test equipment. WLAN is kinda like auto repair for the blind, but it works.
True. If I were preparing results for a data sheet that proclaims the merits of my technology, I would use an RF anechoic chamber, perfect antennas, and properly calibrated test equipment. Nothing but perfect is good enough. The idea is to make it reproducible as well as yielding the best possible numbers.
However, I don't know anyone that lives in an RF anechoic chamber or that cannot detect at least one neighbor with a 2.4Ghz wireless emitter (cordless phone, microwave oven, wireless video, etc). The ability of the system to function (and survive) in such an environment is probably as important as the maximum theoretical thruput. I'll concede that it's probably not reproducible, but neither is reality.
Which would you prefer:
I set the speed to automatic and take a walk measuring the signal strength and SNR. I inform the customer that 6dB signal strength is good for a 2x increase in range.
I lock the speed to 54Mbits/sec and take a walk while downloading some giant file and measuring either thruput or PER (packet error rate). I draw a curve of the thruput versus distance at 54Mbits/sec. The drop off should be quite abrupt. I repeat the test for other wireless speeds.
The first is what you recommend and the way it's done today by most of the wireless industry. The 2nd is the way I think it should be done. Which do you think is more useful?
On Sun, 25 Mar 2007 13:38:29 -0700, Jeff Liebermann wrote in :
No, it's like taking it out for a drive to see how fast it will go. Dynamometer isn't a valid analogy, and isn't terribly useful either for that matter -- much more useful is the output of a diagnostic computer connected to the smart engine control. We use a dynamometer to tune a racing engine, not for basic diagnostics.
Then you're way smarter than I am. ;)
Data on signal strength, quality, and noise. Just as on the car I would want the output of a diagnostic computer connected to the smart engine control.
I wasn't taking a walk. I was sitting at the router, adjusting the antenna, and watching the indicated speed at the other end of the link using VNC or RDC. The data moved by watching the far screen is sufficient to see the perfmon indication fluctuate.
Is the locked-to-54 a go/no-go? I'm not following the need for a locked speed, as opposed to watching the "current bandwidth" change as an indicator. I agree that some data needs to be moving for the reading to be of value.
Yep. The transition between working well, and useless is quite sharp. Try it and see for thyself. However, I wouldn't leave it that way. The error rate will climb very rapidly if the speed is fixed. The default mode is to have the speed decrease with increasing error rate. That gives more range at the expense of speed.
It's not really a requirement. However, locking the speed makes the transition between sufficient SNR and insuficient (lots of errors) rather abrupt. It's a really sharp indication of the maximum range at a given speed.
If I lock the speed, but monitor the "current bandwidth", what happens is quite different. The speed (thruput) might go from the normal
25Mbits/sec to perhaps 12Mbits/sec (about half). That means that every packet is getting retransmitted at least once. It also means that only half the packets transmitted are getting through.
However, if I don't lock the wireless speed, the transition is much slower and difficult to quantify. I've had several system that worked just fine locked at 12Mbits/sec. However, I couldn't leave it like that because there are a substantial number of users with 802.11b only hardware. Anyways, these speed locked systems were fun to test. I would walk away with a laptop running streaming video across the parking lot. At some point, the thruput would abruptly drop to zilch. The difference between working and dead was about 3-6ft at a range of about 30ft.
This might help:
Fig 1 is the chart of Eb/No (signal to noise ratio) versus the BER (bit error rate) for various modulation schemes. I have other such charts of family of curves for other modulation schemes and speeds. Most are much sharper than this chart. What happens is that above about 1E-05 BER (1 error in 10^5 packets), communications and thruput are quite good. 10dB below this value, and the radios start retransmitting packets due to errors. Note that a small change in Eb/No (SNR) results in a huge change in BER (due to demodulator threshold effects). That's what causes the abrupt transition.
Incidentally, I have some much better charts and curves at home and can post them when I get around to fixing my broken bed scanner.