1. Home
  2. Wireless Networking
  3. how to expand router in dead spot of house?
  4. Page 2

how to expand router in dead spot of house?

snipped-for-privacy@hotmail.com (Axel Hammerschmidt) hath wroth:

True. The Wiki/FAQ is built on user contributions. Contributions and corrections are always welcome. There are plenty of topics that have not been mentioned or are incomplete.

The issue I raised is about the characteristics of different types of interference that could possibly cause the OP's "dead spot" or "spotty reception". I suggested that this would imply continuous interference. Since interference is *YOUR* theory, and allegedly responsible for possibly causing the OP's problems, could I trouble you to suggest what manner of device could possibly cause continuous interference? Also, some remedial measures as I find it odd that you would suggest tweaking timing parameters rather than identifying the cause and either eliminating or avoiding it.

Correct. "spotty reception" implies that there is some reception in the bedroom. An increase in signal strength should improve the situation. If the house is long and narrow, redirecting some of the RF in the direction of the bedroom will be a big help. If the wireless router is at one end of the house, and the bedroom at the other, this would be ideal for an antenna reflector arrangement.

Sorry. I wasn't specific enough for you. I'm suggesting that the OP move the wireless device (laptop or desktop) to various locations in the bedroom to avoid any possible null and reflection problems. I don't think that moving walls will be cost effective.

True. But it's so much fun to speculate or guess(tm).

Usually, the OP supplies additional detail at this point, but he's apparently given up and considering power line networking. That will work and is easier if he can find a common power line segment.

So, what does one do for dead spots? In order starting with my favorite: 1. Bigger or better antennas. 2. Additional access point with CAT5 wire backhaul to main router. 3. Better technology (MIMO). 4. Powerline, phone line, or CATV bridging. 5. WDS bridge. 6. Repeater. 7. Bi-directional amplifier. 8. Dead Spot Remover:

formatting link
Out damn spot, out I say...

As I previously mentioned... I advocate playing with every single last lousy setting in the router just to see what happens. Who knows, one might find something interesting, useful, or entertaining. One might also learn something. In every router that I have owned, I make it a point of understanding and testing all the settings. No big deal on a commodity router, but a major challenge with a WRT54G and DD-WRT firmware. It's all part of Learn By Destroying(tm). In the case of the current "dead spot" problem, I predict that adding flow control will not do anything useful.

Use a shofar. ...and the walls came tumbling down.

I don't see where you get that implication, but I can guess(tm). Usually, interference reduction is measured using the signal to noise ratio. That was fairly straight forward with analog receivers. The signal strength versus the remaining noise level between packets. However, with the introduction of all digital receivers, there was a change to measuring the SNR using the error rate. 100% reception success, with no corrupted or trashed packets, was deemed perfect SNR. If corrupted packets were decoded, the SNR value was reduced. The correlation is marginal with the previous analog methods but good enough for site surveys and antenna aiming.

In this SNR case, you are correct. Increasing the probability of a packet arriving without corruption, by reducing its size (i.e. fragmentation), or preventing transmission when the channel is "noisy" (RTS/CTS flow), would improve the SNR. The only problem is that both will slow down the thruput considerably.

Incidentally, CTS/RTS is the common term for modem flow control. RTS/CTS is the common term for wireless. I guess I'll have to change over to using RTS/CTS. Sigh.

Reply to
Jeff Liebermann
Loading thread data ...

formatting link

Do you have any experience using them at a fairly long distance such as between 2 buildings where one is powered from the other?

I was over a friends the other night and they have a real hodgepodge of wireless repeaters that perform poorly. I think putting one AP at the other end of the house and another AP in his little "office" that is attached to the garage which is around 250' away from the house and using one XE102 attached to the main router and a WGX102 at each distant location.

I remember trying the original powerline stuff a few years ago and it maxed out at 150'.

Reply to
George

Spotty just means irregular. It doesn't have to be in physical "spots".

Se later on...

Might only give more reflections. Like pissing (or farting) windwards.

Yes. Getting closer to the cause is difficult in that situation.

But think of the neighbours. And remember CB Radio.

Good solution! But remember also to turn down the power.

Not so good, in this case. Reflections!

Powerline never works, or so I've heard.

Depends, amongst other things, on what's causing the interfence.

Fortunately, the one access point I have managed to destroyed was under warranty

We don't know anything about the signal to noise ratio. The implication in the link is, that flow control "improves carrier sense information".

Hmm! Not sure how this relates to carrier sense?

Reply to
Axel Hammerschmidt

formatting link
>

As a matter of fact yes... Before I sold the place and came to Baltimore, I had a 5 acre place in Northern Idaho, so far out in the sticks no cable/dsl (39 miles NE of spokane wa), so had a sat system for the house, and power from the house to both the garage (about 500 feet away), and the back guest house (about 1/4 mile away).. Used the powerline networking to send the stuff from the sat to the "out-buildings".. That was fine when for wired inside stuff, but I had several notebooks and a PDA all with wifi... So I used Linksys WRT45G (actually mean it to be plural, but afraid readers would think i meant GS rather than G's) in each location to give me wired or wireless access (same ssid/diff channel, but all made one HUGE hot area).. If it was nice I could go outside wireless, when cold and snowy I could stay inside and use either wired or wireless...

As an aside, I tried wireless at first, but after the first snowstorm (the wireless didn't work when it snowed heavy, course neither did the sat), I had metal snowroofs on stilts put over the tops of the buildings, and that blocked the wireless altogether.. I had a ditch dug for power/utils to the garage (and guest area), so since it had power from the main in from the house, tried the powerline stuff.. Interestingly enuf it not only worked great, but when the power failed and the gen kicked in, it still worked fine to the out-buildings...

As another aside, my friend down the street, used it in a metal hulled/bulkhead diesel ship used during the summer for the inland passage to alaska.. Wireless wouldn't go thru the metal bulkheads, but all rooms had power off the generator, so it was an easy way to network different areas..

As for the wap/routers, don't know (i used linksys, the G models ((NOT the gs)) were $49 each at walmart), but can't imagine why the WGX's wouldn't work also, just have no personal experience with that model....

Reply to
Peter Pan

snipped-for-privacy@hotmail.com (Axel Hammerschmidt) hath wroth:

The neighbors dog is named Spot. The kids call him Spotty. Judging by the mess he leaves behind my wood pile, he's not very regular.

No problem...

In order to detect interference, the receiver needs to know what constitutes interference and at what threshold to block transmission. It makes no sense to have any and all detected RF be declared as interference as BPSK and OFDM can extract data from rather low signal to noise ratios. For example, 54Mbits/sec requires a 17dB minimum SNR. I vaguely recall that it's about 6dB at 1Mbit/sec (not sure). The device at one end of a link sends the receive SNR to the other end to allow the sender to determine if it should be allowed to transmit. Incidentally, much of the noise is contributed by internal digital noise from other parts of the router or client radio, which is also responsible for some of the weird variations in receiver sensitivity. An ideal interference detection circuit would measure the receive SNR. If it's over 17dB SNR for 54Mbits/sec, there is sufficient margin to decode the data and transmissions are allowed. If the resultant SNR is less than 17dB, then transmission is blocked under the assumption that the interference will prevent reception. So far so good.

The problem is how to measure SNR. In the older analog devices, the SNR was simply the peak RSSI during transmission divided by the detected noise level between transmissions. This is adequate but slow. As 802.11g speeds and short preambles made it more difficult to use analog techniques, all digital methods were employed. The current method is to use the detected data error rate as a measure of SNR. If some packets arrived corrupted, it would be assumed to have been perpetrated by "noise". The more corrupted packets, the more noise, and the smaller the SNR per some conversion scheme. The effect is the same. When the interference is sufficient to seriously interfere, then transmission is blocked.

The term "carrier sense" is an analog term, that really only applies to analog chipsets. The last of these were the Prism I chipsets with it's mixers and analog front ends. Todays chips are all digital and direct conversion (no mixers).

If one implements flow control (RTS/CTS) in such a system, the SNR will improve simply because the system now has an additional method of detecting interference and measuring SNR. Instead of relying on just the SNR of the other end of the link to determine when to transmit, the system now adds flow control handshake management packets that determine when *BOTH* ends of the link have sufficient SNR to xmit. This does very well for eliminating "hidden nodes" but also improves the all digital version of SNR by simply improving the chances that a packet will arrive intact.

As always, there's no free lunch. If you use flow control to improve delivery reliability, the overhead will slow down the thruput. I don't know the exact performance hit, but my testing showed that it's substantial. It's as I hinted in a previous rant, 100% delivery at

1Mbit/sec is considerably slower than an error prone 30% delivery at perhaps 12Mbits/sec. That same thing with flow control. If you improve the delivery probability by blocking xmission during interference, the system will by necessity slow down.
Reply to
Jeff Liebermann

Jeff Liebermann hath wroth:

Argh. So much for my photographic memory.

formatting link
Mbits/sec Minimum SNR (dB) at BER=10^5

1 -3 2 1.6 5.5 6 11 7 6 6 9 7.8 12 9 18 11 24 17 36 19 48 24 54 25

Yes, at 1Mbit/sec, the detector can theoretically extract useable data buried under twice as much noise power as signal.

These are the theoretical minimum SNR numbers. Reality is always somewhat worse.

Reply to
Jeff Liebermann

Snow:

I read most of the responses. I did not see one that mentioned the simplest solution. Try moving your AP a bit. If that doesn't work, change the orientation of the antenna. Vertical to horizontal, or horizontal to vertical. Sometimes small changes and alteration in orientation fixes things. Then you can go to the reflectors, (note, do that and you will create a new dead spot behind the reflector).

Reply to
Richard Johnson

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.