Ted 0 Posted January 13, 2009 I had a discussion a while back about setting up several wireless IP-cameras to a common access point. Has anyone here tried that? My guess is that it doesn't work because of radio interference. Each camera transmits a constant stream, so which camera will be received by the AP? The strongest. I tried to explain that it is the same thing if four guys with walkie talkies push the talkbutton at the same time and a fifth guy tries to hear what each guy is saying. But since i haven't tried it, i might be wrong. Any experiences? Share this post Link to post Share on other sites
Soundy 1 Posted January 13, 2009 I assume you're talking about WiFi? Ever used multiple computers with a single WiFi router? Same thing... no problem. The walkie-talkie analogy doesn't apply. A bigger concern with WiFi is the limited range and interference from other sources. Share this post Link to post Share on other sites
Ted 0 Posted January 14, 2009 Yes I have used multiple computers to a single wireless router. The difference between computers and a camera is that the computer transmits packages only when information is exchanged. Between those packages other sources can use the router because transmission is turned off, it doesn't have a constant flow of data. A camera transmits continously. Two portable handsets cannot use the same DECT base station simultaneously, same thing. You cannot listen to two radio-stations at the same time. The only way I can see this possible is if the cameras use different radiofrequencies. I haven't tried so I can't tell for sure. But on the other hand, for security reasons, wireless is not optimal. Maybe directed antennas as a link between buildings, connecting a cluster of cameras through a switch to a server. So I still wonder if anyone tried connecting, for exampel, four Axis 207W to a common accesspoint. Theories and reality are not always in the same league Share this post Link to post Share on other sites
Soundy 1 Posted January 14, 2009 Yes I have used multiple computers to a single wireless router. The difference between computers and a camera is that the computer transmits packages only when information is exchanged. You've never seen a bunch of gamers all running on WiFi then, or someone running a bunch of torrent uploads/downloads... where lots information is being exchanged constantly. Between those packages other sources can use the router because transmission is turned off, it doesn't have a constant flow of data. A camera transmits continously. Two portable handsets cannot use the same DECT base station simultaneously, same thing. You cannot listen to two radio-stations at the same time. Still not the same analogy. If it were, you couldn't have two households using the same type of cordless phones (be they 900Mhz, 2.4GHz, 5.8GHz, or DECT 6.0) in any proximity to each other. The only way I can see this possible is if the cameras use different radiofrequencies. Same frequencies, different channels. I haven't tried so I can't tell for sure. But on the other hand, for security reasons, wireless is not optimal. The bigger issue with wireless, or at least with WiFi, is range. It's so limited under most conditions, there's little point to it - most distances covered would be close enough to run a wire. There are exceptions, of course, like if you need to cross a large open area, but in general, wiring within those distances is probably far more efficient. Share this post Link to post Share on other sites
Ted 0 Posted January 14, 2009 You've never seen a bunch of gamers all running on WiFi then, or someone running a bunch of torrent uploads/downloads... where lots information is being exchanged constantly. I know that is working, but I know too little to draw any conclusions on how the comparison with cameras is applicable. Still not the same analogy. If it were, you couldn't have two households using the same type of cordless phones (be they 900Mhz, 2.4GHz, 5.8GHz, or DECT 6.0) in any proximity to each other.That's true, you can't. Unless they operate on different frequencies. They can operate in the same frequency range but not on the exact same frequency. Same frequencies, different channels. Different channels aren't the same frequencies. The bigger issue with wireless, or at least with WiFi, is range. It's so limited under most conditions, there's little point to it - most distances covered would be close enough to run a wire. There are exceptions, of course, like if you need to cross a large open area, but in general, wiring within those distances is probably far more efficient. Agree. Point to point linking is in many cases cheaper than wiring with fiber. Share this post Link to post Share on other sites
Trimyr 0 Posted January 18, 2009 Soundy wrote: You've never seen a bunch of gamers all running on WiFi then, or someone running a bunch of torrent uploads/downloads... where lots information is being exchanged constantly. I know that is working, but I know too little to draw any conclusions on how the comparison with cameras is applicable. It's exactly the same thing. Just as all those gamers on a LAN or wireless LAN are constantly sending and receiving data streams, so too would your cameras. The only thing to worry about is the total bandwidth those cameras would require. For instance, four 1.3 MP cameras at 30fps would use on average about 30Mbps total (a little more including ping and general inter-device network communication). If your 54Mbps wireless is set to full duplex, then it should be no problem. Half duplex, then you'd notice some slowdown in the framerate, very slight inaccuracies in time signatures, etc. You seem to be worried about all those cameras sending signals one time. The IP cameras are all sending packets rather than a constant analog signal. This is the basis of all IP communication. As long as you have the available bandwidth, a properly set up network will take care of itself. You mentioned the Axis 207W's. Even at the highest quality MPEG-4 settings (jpeg is a different story) in a complex scene, you shouldn't use more than 24 Mbps total for four of those at 30 fps each. On a 'normal' small (i.e. 5-8 computer) network, you shouldn't notice any difference. Any larger than that, and just run them on a separate wireless switch connected to the main router. You'll be ok. Share this post Link to post Share on other sites
Ted 0 Posted January 19, 2009 Ok, so even if they transmits continously, in reality they don't transmit a constant signal. The transmitters switch on and off, but quite rapidly. And in those gaps in transmissions, other transmissions occur. I guess the data is buffered in the cam and transmitted when there is a suitable moment or gap and it is all orchestrated by the switch. My background is from analog radiocommunications, that's why I was confused about several transmitters on the same frequency. Share this post Link to post Share on other sites
Soundy 1 Posted January 23, 2009 If you want more detailed technical info, you can look up the 802.11 spec at www.ieee.org. There's also some good info in this PDF: http://sss-mag.com/pdf/802_11tut.pdf Share this post Link to post Share on other sites
