I'm currently trying to undestand a "feature" of my single DCS-920 system that is similar to yours. The camera is only 12 feet from the router but it disconnects 3 or 4 times per day. the video stream is mostly continuous but every so often its jittery. I don't know how long the disconnects last (no info in logs that I can find) so I'm not sure how severe the impact is. There is only a single interior partition between the camera & router. No duct work, only 1 or 2 110 AC electrical wires. Nothing that should corrupt the signal. No uWaves, no fridges, no TV, video games, just the PC now connected directly to the router.
I changed the link between my Laptop & the router to Gigabit Ethernet. No improvement in the signal. I've been changing the 2.4 GHz router channels trying to change the response. No luck so far. Always get 3 or 4 disconnects per day.
The D-Link support guys claim the router is the problem but I'm beginning to suspect that the problem is the antenna or the power of the transmitter in the camera. Not finsihed with my experiments yet, but it's looking more & more like the camera. Bummer.

Currently using Netgear WNDR3700 N+ Router. (Originally used Cisco/LinkSys E-3000 N+ Router. Replaced due to thermal problems.) Disabled 5 GHz radio as experiment. Disabled SSID transmissions for 2.4 GHz radio to reduce radiated noise. Moved the router several times before connecting with ethernet. Reduced 2.4 GHz transmission rate to 54 MBps. Disabled guest radios (never set them up but disabled just in case they were radiating). No improvements.
The current camera is the CLOSEST camera in my anticipated system. The others will be roughly 30 or 40 feet from the router if I buy more. I'm planning on 930s for the 5 GHz operation. I can try & centrally locate the router but I don't have an optimal central spot (uWaves, fridges, TV, electronics, etc). Simple wood frame house, sheetrock walls, metal HVAC ducts in walls & ceilings, copper electrical wiring. Nothing special. Nothing that should reduce the effect of the wireless transmissions. The PC wireless GUI shows Exellent signal strength from the router all over the house. Including basement, attic, deck, & garage. So I don't think the router is the problem.
Don't think I can connect the router to the camera with ethernet. Position of camera/router require longer ethernet cable than I have. Not willing to make my own cables.
Can't use ethernet as a network. Not willing to remodel the house just for camera wiring. If I can make the wireless usb work effectively & reliably this is an acceptable solution. If the wireless isn't up to the task the game is over.
I'll post as I know more......