2.4GHz-Friendly Phones?

da3dAlus writes "When I first bought my 2.4GHz wireless phone system several years ago, it was a rather new technology, and wi-fi wasn't even on the scene. Now it appears that all wireless phones are on the 2.4 or 5.8 GHz spectrum, and I've got neighbors with wi-fi (with myself included). While checking out new phones recently, I've noticed some are carrying a "802.11 Friendly" sticker. The question is, are there any trully 802.11 friendly phones? Has anyone really ever had a problem with these types of phones interfering with their wi-fi network?"

Comments

900mhz?

[Anonymous Coward]

Mine 900mhz cordless phone even has spread spectrum. Works great, excellent range.

Why YES, I have had problems

[johncel]

So, I had a linksys wifi router and an AT&T 2.4 gHz phone... They fought like dogs! If the phone rang, wifi was out for at least 5 mins after you hung up. What a pain. I finally just bought a 5.8 gHz phone.

Re:Why YES, I have had problems

[mindriot]

Hmm weird... here in Germany (all of Europe, in fact), most wireless phones operate using the DECT standard at 1.9 GHz. At least those don't interfere with any Wi-Fi equipment (afaik)... how come your phones are using a different standard at 2.4/5.8 and not DECT? What type of standard is used on your phones? Some googling indicates that it seems to be called DCTS. What are its advantages? How come DCTS and 802.11 are allowed to operate and interfere in the same frequency range? Can someone shed some light on this please?

Not a myth.

[genixia]

My inlaws' 2.4GHz 'phone (sorry, can't recall the brand) totally screwed up their Linksys WLAN until I changed the WLAN channel (now it degrades link quality but doesn't drop it).

OTOH, My Panasonic 2.4GHz 'phone has never interfered with my Netgear WLAN.

I suspect that the 'phone brand has more of an effect than the WLAN brand.

No problems in my house

[DesertJester]

I have used my 2.4ghz phone while on my 54g wireless net with no issues. In fact my microwave messes-up my phone more than it does my wireless. I have two Linksys AP's running on a mostly wired net. They give me great coverage, sometimes too good... damn nieghobr with NetStumbler..oh well.

Adaptive 2.4ghz is probably why

[rtilghman]

I haven't looked into it too much, but from what I understand newer 2.4ghz phones use an adaptive frequency response to get around interference from other devices. In essence they detect other devices on "locked" channels and maneuver their way through the mine field without causing any real problems for everyone else.

As for actual signal strength, the phones aren't usually the problem. 2.4ghz phones have 2.4ghz transmitters in the base station, but the phone itself is often just 900mhz. That being the case positioning the phones base unit away from any WIFI equipment can help, the same way positioning WIFI gear away from a microwave does.

You can probably just find more about the newer adaptive 2.4ghz stuff by doing a search with google...

-rt

why 0.9Ghz is better

[infonick]

900Mhz phones:

1) are inexpensive;
2) do no interfere with the 5Ghz and 2.4Ghz wifi channles;
3) do no interfere with Bluetooth;
4) are inexpensive;
5) will get better range because of the lower frequency used.

Re:why 0.9Ghz is better

[bogie]

Companies went with 2.4GHz so they could sell the same products to people again. Although the latest 2.4 phones are probably ok for years 2.4GHz phones had shit reception compared to their 900MHz predecessors. There is zero doubt in my mind that most 2.4GHz phones were not equal to their 900MHz counterparts when they first came out. I used to hear echo and bad reception constantly on 2.4GHz phones while 900MHz just worked. Plus even now 2.4GHz models can have a nack of interfering with wireless which you and especially your neighbors probably won't like.

Re:why 0.9Ghz is better

[Steve Cowan]

You hit the nail right on the head. Speaking as an RF technician I can verify despite some others' opinions that 900 MHz will almost always propogate better than 2.4 GHz.

Apart from seeming more impressive numerically (after all, a 2.4 GHz phone is 1.5 GHz more than a 900 MHz phone), there is NO advantage to 2.4 GHz.

The 2.4 band has been set aside for unlicenced, low-power, public spread-spectrum use. Blutetooth uses it too.

I think it's only a matter of time before the cordless phones talk directly to WiFi routers anyway via VoIP, and then this whole thing will be moot - and phone companies will be very upset.

Interference Robustness

[mrbrown1602]

I have a PowerBook G4 which is equipped with an Airport Extreme card. The Airport Extreme (802.11b/g) has a feature called "Interference Robustness" which prevents any problems I would normally encounter using my 2.4GHz phone. Does anybody have any insight into how this works and does anybody know if any other wireless adapters include it?

Re:My microwave

[j1m 5n0w]

Interesting - that gives a window of about 8.3 milliseconds. (1/120th of a second, if I understand you correctly.) A full size packet takes about a millisecond to transmit at 11mbps, plus a few hundred microseconds for the ack. That should be well within the window.

Unfortunately, after repeatedly losing packets, most 802.11 gear will probably drop the transmission rate to its slowest rate: 1mbps. 1500*8 bits at 1 mbps is about 12 milliseconds (plus a few hundred microseconds for the header), which no longer fits in the window. In other words, by falling back on a more reliable transmission mechanism, 802.11 shoots itself in the foot.

Maybe if you can pin the rate at 11mbps and enable short headers (an option in the 802.11b standard supported by some hardware) it could work reasonably well, but fragmenting packets should help as well.

-jim

900 MHZ Interference

[OYAHHH]

Given,

All of the 900 mhz advocates on this thread seem to think there is no interference I would like to interject and say that I do have interference issues with my 900 mhz phone and my 801.11 B equipment.

More specifically, I have a Panasonic 900 mhz gigarange telephone with some sort of digital spread spectrum technology (KX-TC1891B). The phone does not seem to impact my 801.11b equipment's (Linksys WRT54G) connectivity.

But, connectivity isn't everything.

As soon as I hooked a Hawking omnidirectional attenna onto my router I suddenly started hearing a beep on my computer speakers about every 5 seconds.

It about drove me nuts one day when I took the phone handset off the base unit and placed it in another room. I didn't realize that my phone was causing my computer to beep.

I thought something was dieing on my computer or that some program/virus was playing a cruel prank on me.

I must have rebooted that computer 20 times that day trying to isolate the cause of the beep. Never did.

Next day, put the phone back on the base unit and the beep went away.

Having discovered the source of the problem, I couldn't believe it, I turned the sound off via the computer's O/S, picked up the handset and no beep.

So, nowadays I have to turn the sound off on my computer before I answer the phone. Very annoying. But I paid a bundle for the two line phone, for which my wife was sorely irritated, so I guess I'm stuck.