With signal strength at -70 you won't be having a reliable connection. The 2.4Ghz is the one we need to see but this one shows the signal strength pretty well.
How many walls is this going through or how far away are you from the router?
This is a rough sketch to give you a visual, it's only a couple of meters away, just in the kitchen, which sits next to my room. You can see below.
You would think that would work but in reality wireless is not so good at going through certain types of walls. More than two plaster walls won't be good, three walls you can forget it, plus anything else in the way just makes it worse. You should try moving close to the router "same room" to determine if this is in fact just a weak signal problem. If the situation doesn't change then try updating the firmware on your DIR-655.
Wireless routers tend to work much better in a larger room with no obstacle's in the way. So the real problem is that this router is stuffed way back in a corner behind some walls so it's signal isn't really getting out. Mine has pretty much the same problem. You can try to reposition the router and then test in other areas of the house, this would be the cheapest way to fix the problem.
I have the same router so I know it's limitations, mine is in a similar position but in my case I have an older house with plaster walls, mine had to go through a big metal heater and a huge cement fire place plus three walls and if I get on the other side of the fireplace the connection cuts out completely. This router also has the best reviews of just about any router on the market today so it's not the routers fault.
Because of this I have installed an access point DAP-1522 on the other side of the house. This covers my entire backyard, other end of the house and the garage which is 30 feet away with a perfect signal. I did need to run an Ethernet wire to a switch and then to the access point, I ran this Ethernet cable under my house which made it easy. There are also A/P's that can work through your house wiring, but I'm not familiar with them. The link I posted shows one from D-Link just below the DAP-1522.
I tried to give you settings for best possible wireless N speeds. But with poor connection strength they won't help much. We get people in here all the time with the same problem, weak signal going through too many walls. Wireless is only as good as you make it.
Yes agree you have a weak signal you could buy a couple of powerline adapters plug one in the kitchen and connect the ethernet cable from one of the Lan ports on the router to the Lan port on the powerline adapter which you plug into the wall socket.
Then plug the other powerline adapter into a socket in your room where your computer is and connect an ethernet cable from computer ethernet port ot Lan port on powerline adapter and get a ggod connection to your router.
They are not that expensive and pretty easy to configure.
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