Wi Fi Propogation and Transmission - line of sight wi fi vs cordless

Could someone please explain to me as to why Wi Fi reception seems to be line of sight dependent wheras cordless phone reception does not seem to have this limitation. My belief was that B and G are in a similar band as the cordless phone frequencies .

Reply to
Loading thread data ...

I'll assume you're talking about a 2.4Ghz cordless phone. Please note that there are many different types of cordless phones with different frequencies and modulation methods.

- Wi-fi transmits at 1Mbits/sec to perhaps 54Mbits/sec over a 26MHz signal bandwidth.

- Analog cordless phone does perhaps the equivalent of 0.005Mbits/sec over a 0.025MHz bandwidth.

- Wi-Fi is highly sensitive to data waveform distortion caused by reflections.

- Analog cordless phones are not.

- DSS (digital spread spectrum) cordless phones use the same spectrum as Wi-Fi, but at a much much much lower data rate.

What happens is that for a given power level and bandwidth, you can always trade speed for range. Wi-Fi goes quite fast, but not very far. Cordless phones go quite slow, and therefore go quite far.

True. Cordless phones constitute a major source of interference to Wi-Fi.

Reply to
Jeff Liebermann


why is it that the cordless phone propogation seems to be somewhat of a radius whereas even at a distance with lower transmission rates Wi-Fi seems to be more of a line of sight propogation than a radius pattern ?

Reply to

where is this stated?

True for some phones.

WiFi does not need line of sight. My AP is upstairs and in a cupboard.

Many offices have out of sight connections.

Cordless phones have a longer range when there is line of sight just as WiFi does,

Reply to

My me?

The previous question was slightly confusing. This variation is worse with no indication that you understood what I was previously trying to explain. Please re-read my previous answer and rephrase your question. I think you're asking about differences in coverage patterns. If so, "line of sight" has no connection with the question.

I can't answer "why is it..." type questions because your statement that follows is wrong. 2.4GHz propogation is the same no matter how it is generated and what form of modulation and bandwidth used. What is different is the ability of the system to recover from noise, interference, reflections, multipath, variations in signal level, and co-channel users. Because 802.11b/g requires a rather high S/N ratio to operate, anything the trashes the S/N ratio will appear to have an effect on reliability. However, the typical 2.4Ghz cordless phone can operate with a rather lousy S/N ratio and can survive substantial transmission imparement problems. The cordless phone is therefore more reliable, but at the price of bandwidth and speed.

If both the 802.11b/g and the cordless phone systems used roughtly identical antennas on both ends, their range and antenna patterns would be roughly the same. There is nothing inherent in 802.11b/g that would force it to be directional, which is what I'm guessing you mean by "line of sight".

Are you asking why is it that your 2.4GHz cell phone works reliably thoughout the house, while the 2.4GHz wireless router craps out as soon as it goes through a wall or two? If so, it's again the ability of the two systems to recover from S/N ratio imparements. The cordless phone can tolerate enormous fades, lots of reflections, and very low signal strengths, because of the narrow bandwidth. The

802.11b/g radios cannot, because of the wide bandwidth.
Reply to
Jeff Liebermann

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.