Linksys WET54G reliable? alternatives?

I need to use this, or something very similar, to connect a location wirelessly to a nearby internet connection.

I've read some bad reviews, but I can't find much else that does the same job.

Any suggestions? Any experiences to share?

The link will include several VoIP lines and needs to be solid.

Wireless (radio) performance should not be an issue as it would be used with high gain antennas and it is no more than 30m(90ft) away with line of sight.

Thanks in advance, Alex

Reply to
Alex Bird
Loading thread data ...

This is overkill, we're in a built up area, no-one elses wi-fi or video sender should be able to break the phones - which will be used for phone in radio shows some of the time. Either 7 or 16dB yagis, more directional than gain-y.

The AP/router I'd like to use at the internet end, which has various other good qualities, doesn't do bridging. There's one I'd quite like to use at the other end - with the same problem.

Bridging and 'client mode' seem to be often names for the same proprietory and poorly supported mode, correct me if I'm wrong. This really puts me off!

ALex

Reply to
Alex Bird

Going for WRT54GS x3 instead. Far more flexible and cheaper.

Alex

Reply to
Alex Bird

How high gain? You should be able to get that working without additional antennas with line of sight.

Any access point with a client mode, or pair of AP's in bridge mode will also do what you want, I don't see why you feel you have to use the Linksys or similar. Can you give a bit more detail?

David.

Reply to
David Taylor

Possible mistake. Don't use too much gain if you have a good view.

The problem is that you will pickup any and all forms of 2.4Ghz interference along the line of sight of the antenna. Sure, you'll have a strong signal from the other end of your link. However, you'll also have a strong signal from any other device along the path.

That was one of my earliest screwups. I setup a point to point link between two buildings in an industrial area. The distance was only about 500ft, but I used a pair of 19dBi dish antennas. The initial installation was a pair of 10ft poles on the rooftops. It worked fine for about 6 months. Then the interference started. Eventually, I traced it down to another wireless user about 3 miles away that was inconveniently located along the line of sight. My solution was to move one of the antennas from the rooftop to the side of the building. This put the building at the other end of the link in the line of sight, effectively blocking the source of interference.

If you think of the gain of the antenna in terms of distance, 6dB gain is equal to twice the range. That means you will pickup interference from twice as far away. Someone with a leaky microwave oven along your line of sight could clobber your reliability.

There's another problem with too much gain too close. Most 802.11b/g radios have rather poor receiver dynamic range. The current crop of all direct digital conversion chipsets are great but sacrifice receiver overload specs to gain sensitivity and low power consumption. It's easy enough to tell if you have too much signal by just watching the error rate.

This is balanced by the need to get a sufficiently good signal to noise ratio, which implies a sufficiently high signal strength, in order to get decent performance. Playing with the numbers, I'll assume you want to get at least a 24Mbit/sec connection. The minimum fade margin is assumed to be 20dB.

The following was lifted from the DI-624 datasheet but is close enough for most similar 802.11g radios: * 54Mbps OFDM, 10% PER, -68dBm) * 48Mbps OFDM, 10% PER, -68dBm) * 36Mbps OFDM, 10% PER, -75dBm) * 24Mbps OFDM, 10% PER, -79dBm) * 18Mbps OFDM, 10% PER, -82dBm) * 12Mbps OFDM, 10% PER, -84dBm) * 11Mbps CCK, 8% PER, -82dBm) * 9Mbps OFDM, 10% PER, -87dBm) * 6Mbps OFDM, 10% PER, -88dBm) * 5.5Mbps CCK, 8% PER, -85dBm) * 2Mbps QPSK, 8% PER, -86dBm) * 1Mbps BPSK, 8% PER, -89dBm)

Run the numbers at:

formatting link
-79dBm for the receive sensitivity. Aim for a fade margin (SOM) of about 30dB. See how much antenna gain it takes. With: Distance = 0.016 miles (100ft) Tx power = 15dBm Tx ant gain = ??dBi Rx and gain = ??dBi Tx cable loss = 3dB (including connectors) RX cable loss = 3dB RX sens = -79dBm (for 54mbits/sec) Doing the trial and error routine for antenna gain values until I get

30dB fade margin, I get antenna gains of only about 5.5dBi.

That means that you'll get reasonable performance at about half the connection speed of 24Mbit/sec, with only 5.5dBi gain antennas. Anything with more antenna gain just picks up more interference along the line of sight with a possibility of overloading the receiver front end. I'm gonna *GUESS* that the receiver will start to overload at signal levels above -20dBm. (This is a guess and should not be considered accurate). Using 15dBi gain antennas at both ends and plugging back into the above URL, I find that the receive signal level is -29dBm. Good enough, this should work.

Summary: Try to control your line of sight with high gain antennas. Do the numbers first. Watch out of too much signal if you have a short path length.

Join the club. I once tried to scribble a document explaining the various terms. I gave up. There's too much muddle. I'll try again, but forgive me if I leave some holes. I didn't invent these terms so don't blame me for the muddle. I'll only cover the bridging and client modes as this can go on forever.

  1. All wireless is bridging. Note the word ALL. A bridge connects two networks by inspecting the destination MAC address and passing only those packets that are know to have a destination address on the other side of the bridge. There is no routing or IP addresses involved in bridging.
  2. An "ordinary" client radio is a bridge that is only capable of bridging exactly one MAC address. Most client adapters fall into this classification.
  3. A "workgroup adapter" is a client radio that will bridge more than one MAC address. Some (not all) game adapters fall into this classification.
  4. A "game adapter" is an ethernet to wireless bridge that may or may not bridge more than one MAC address. Some do, some don't. Good luck prying whether it does out of the support.
  5. A "transparent bridge" or "wireless bridge" will pass multiple MAC addresses usually using some form of proprietary bridging protocol. That means that both ends of the bridge must have identical hardware. Wireless clients may NOT connect to either end of the bridge.
  6. A "WDS bridge" is similar to the "transparent bridge" but does not require identical hardware. WDS allows simultaneous transparent bridging and acting as an infrastructure access point. Wireless clients may connect to either end of the bridge. WDS can be used to extend the coverage of a network by adding additional radios.
Reply to
Jeff Liebermann

Luckily one end of the link will be 10-15 metres higher than the other. Line of sight is 45* into the sky and ground.

Alex

Reply to
Alex Bird

You don't even know where in the world this will be, so that is a bit of an assumption ;o)

Probably you should read more of a thread before posting. Already ordered WRT54GS x3, mucho open source firmware...

Alex

Reply to
Alex Bird

Illegal then. Ok. :)

Really? Most of the cheapo ones do bridging so why not just get a couple of cheapies and bridge that.

Nope, bridging is between two AP in bridging mode, client mode is an AP acting as client off an AP running in AP mode.

David.

Reply to
David Taylor

Absolutely, I assumed based on your domain. Where's it going to be then? :)

Yep I saw that. I was reading inline rather than reading all the messages first. Way too much effort to go back there.

You might want to look at the Sveasoft firmware to put on those, plenty of other options that you might make use of.

David.

Reply to
David Taylor

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.