tgibbs wrote:
FastBikeGear wrote:
Despite rumours, Microwave ovens and Blue tooth devices may slow down data throughput but they will not break the connectivity of properly designed WiFI products.
This seems a remarkably strong statement. After all, there are a lot of microwave ovens, and they are fairly low cost consumer devices, so one might reasonably suppose that they would vary quite a bit in the amount of electromagnetic leakage. And there are also a very large number of wifi products that presumably must vary in sensitivity and interference rejection. So to make such a statement, one would have had to have carried out tests of at least several dozen microwave ovens of various manufacturers, and also dozens of wifi devices of various designs and from various manufacturers. Perhaps you can direct me to a study that would justify such a blanket assertion? I should note that I have personally observed a microwave oven reproducibly breaking the connectivity of multiple wifi products that had a strong signal prior to the oven being turned on. Perhaps most consumer wifi products are not "properly designed," but in that case your assertion carries little practical value.
Yep I admit it is a pretty strong blanket statement. But it has been one that has stood the test of time for me. (Not to say that I will one day come across a situation where it may not hold true).
I have designed, installed and serviced 100's of wireless networks and used several different wireless analysers and site survey tools. It was frequent for us to hear of customers claiming that their mircrowave ovens were breaking wireless networks. On investigation and testing we always discovered another problem.
Here's some more background:
Lucent used to advise that only commercial microwave ovens would cause enough interference to cause a percentage of packets to be 'lost'. When I asked on one early in house training course they ran for us what was the definition of a commercial microwave oven, the instructor humorously stated a commercial microwave was one you could climb into!
Despite his assertion we occasionally could detect a faulty domestic microwave with our test gear including one very old one in our own cafeteria! - (which was immediately replaced on safety grounds with one that when tested did not leak). However we never ever came across a situation where they broke the connectivity. But we did discover occassions where they MARGINALLY slowed networks.
The potential issue with leakage from Micowave ovens is that wireless networks use CTR/RTS (Clear To Send and Ready to Send) signals to control which device transmits when. (Not everyone can talk in a crowded room at once and expect to be heard). Unfortunately Microwave ovens do not listen to or obey these signals and hence leaky microwaves will talk over the top of other devices resulting in poor signal to noise ratios that prevent the receiving wireless device reading the packet correctly.
Lucikily all Ethernet devices including wireless Ethernet (WiFI) devices do not assume that they are working in an error free network. Higher levels of the protocol stack re-transmitt packets when they do not get the appropriate response from the device they are communicating with. Therefore these networks will tolerate lost packets and in most situations the user will not even realise that some percentage of packets are being retransmitted.
At one stage Lucent introduced a proprietary feature called 'Microwave Robustness' that increased the spacing between packets to minimise the potential effects of leakage from microwave ovens to further improve performance. This feauture was subsequently dropped and never introduced into the wireless standards.
As initially stated no one in our team ever discovered a single instance of a ability for two wireless devices to reliably communicate.
The reality is that there is now a fairly high density of wireless devices. With 802.11b there are a maximum of 3 channels that do not overlap and interfere. These Channels are 1,6,and 11 and hence these channels are the most commonly selected channels.
Wireless anlaysers and site survey tools measure signal to noise rations, identify channels in use etc. Most sources of interference proved to be from other WiFi networks operating on different channels.
