Nomad on Wireless Cameras Range Issue

I recently purchased and installed wireless IP cameras (IPOB-EL3IREW 3MP Elite Network IP WIFI Wireless IR Bullet Security Camera).

I have a good Netgear wireless router and using a regular NVR to access the cameras. The picture from a nearby camera is fine but from cameras 60 feet away freeze.

I purchased a installed a Netgear WIFI extender. Question to experts:

1- Is the freeze related to power or the wifi?

2- If I switch the cameras to wifi extender, then how a non-wireless NVR can detect that?

3- I am using the wireless cameras for the first time and any suggestion / recommendation  will be greatly appropriated.  

Thanks

AZ