You posted and you answered 5ghz is your solution, do not buy 7510 buy a pair of CPE510

Need to know why are placing a 3G/4G Wireless N Router TL-MR3420 and not a 300Mbps Multi-Function Wireless N Router like TL-WR842ND AP1-AP Mode AP2-Client Mode, here you are cabling from AP2 inside...

AP-Client router mode sucks cause is a repeating mode Set Client mode it's like laying a imaginary cable between devices, for wireless on Client side just add a cheap router as AP

AP Router mode has Mac clone under Network

As Client http://www.tp-link.com/en/faq-318.html Client http://www.tp-link.com/en/faq-348.html Repeater http://www.tp-link.com/en/faq-289.html AP Client Router

coca koala wrote Draw a diagram of your topology, show us how all the devices are connected, what is the distance between the devices, what are IP addresses. @soyebhusen and please clarify if is 2...