How to limit DOWNLOADING SPEED of PC and Phones connected to my WiFi ?

Please read the Wikipedia article on "Quality of Service". QOS is implemented by a wireless router. There, you can configure various possible connections to that router such that some have different service levels and maximum download speeds from others. Most consumer grade routers DO NOT have this feature, since it is not typically needed in home environments. If you need a router with configurable QOS, you need to search for one that specifically supports that feature. They will cost more. You can also flash the ROM in certain standard routers (often Linksys) to replace the factory firmware with firmware from 'Tomato' or 'dd-wrt'. These replacement firmwares usually support QOS. Replacing the factory firmware is NOT easy and IS risky, so very few people do it, and if you are one of them, you must understand the risks.

challenging situation. research over google and yahoo. that may help!