Are problems with putting more than one wireless router in an apartment?

1. No, generally they are set to automatic and find the channel with the least noise, I believe in the USA we can use channels 1-12 on the 2.4 ghz frequency. Also the 5ghz (N or A standard) have ALOT more channels they can use (I don't know them off the top of my head). Some older routers may just have their default channel set to 1. Keep in mind generally there is channel bleed over with these so if you set channel one it may also interfere on channel 2 and 3 so set them far apart (IE: 1 and 11).

2. Yes I have not seen any wireless routers that don't have this capability however they may exist so don't buy a cheap knockoff, any linksys, netgear, D-link ect should have this functionality.

3. They search all the frequency's for any broadcasted SSID (wireless network name).

4. Yes, wireless networks operate in half duplex. Meaning if one channel is sending data OR receiving data nothing else can use that channel simultaneously not even the same device.

5. Yes and no. They may not be actively transferring data and may leave the channel clear for a few fractions of a second but as long as it is connected it will be replying and sending ARP info as well as responding to other requests over the broadcast. Networks are busy even if you aren't using them.

Additional info:

Make sure only one device is providing DHCP and NAT. The second wireless router should only be acting in layer 2 mode or access point mode. Double NATing may work for a bit but you will run into problems with network traffic that relies on UPNP (games, bit torrent, skype ect) it may also cause random issues on your network.

1. There are 11/13/14 Wi-Fi channels on the 2.4GHz band and some more on 5GHz (See wiki). Some routers can automatically avoid congested channels, but many will only use the one set by the user in their configuration.

2. Most if not all routers allow the channels to be changed. Make sure you only use the non-overlapping ones. (See wiki above.)

3. Computer search all known channels.

4. Yes. There are severe interference if there are two transmissions on the same or nearby channel. If you have two busy 802.11 networks on the same channel, the effective bandwidth is normally reduced by over 50% each.

5. This depends. 802.11 is a CSMA/CA variant protocol which means it will do its best to avoid multiple stations transmitting at the same time. However due to the properties of EM waves, it is impossible to prevent collisions completely so there will be great waste in bandwidth if the channel becomes crowded.

Almost all WLAN routers do allow you to set which channel (frequency) they use. If a couple of routers are close together, it's likely that their signal will interfere with that of other routers. This mean you will get less bandwidth or no connection at all.

1. Not necessarily. If their SW is clever they look for a channel with no or minimal traffic.
2. See above.
3. They list all WLAN routers they "see".
4. Yes.
5. No.