This is from the Nexus 4 forums, and this is how i get connected to 5ghz wifi on my nexus 5
Just a few facts about 802.11a/802/11n 5GHz. I have simplified things a bit since the detail is not important.
In many countries/areas of the world some of the channels in the 5GHz band used by 802.11a/802.11n are designated as
Dynamic Frequency Selection or "DFS". This means that these channels are shared with military/civilian radar and
perhaps other transmissions. As such any wireless 802.11a/802.11n device using those freqiencies is required to
detect a radar transmission on a channel it is using and switch channels in order to avoid interfering with ("stepping on")
the radar signal. The device may not return to the channel for 30 minutes. Most routers and wireless "cards" in
laptops/desktop computers implement this functionality. Many mobile devices do not implement such functionality so are
not allowed to use the DFS channels.
This creates problems if your router chooses to use a DFS channel and you have a device which is not allowed to use
those channels. The Nexus 4 and Nexus 10 devices fall into the category of devices which are not allowed to use DFS
channels. So if your router chooses to use a DFS channel the N4 and N10 will not see the router at all.
In the US (you can google to see the channel list throughout the world)
Non-DFS channels: 36, 40, 44, 48, 149, 153, 157, 161, 165
DFS channels: 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140
My router "likes" channel 132. I force it channel 44 so I can see it from my N10.
The N10 also implements 40 MHz bandwidth. That is what the 40 in MiMO HT40 specification means. It works very well
using 40MHz *if* your router handles it properly. I have seen some which do not. I do not know if the N4 supports 40 MHz
bandwidth or not. However if the router implements 40MHz properly then it can support both 20MHz and 40MHz bandwidth
devices at the same time. I have both on my router.
Hope this helps.