if you are using systems in the same house then there are few ways
1) Go for a wifi modem and use where ever in 30 mts(by BSNL modem, private up 100 mts) if you dont have wifi in system then can install wifi cards
2) use the current modem itself if it has 2 ethernet ports and connect through the RJ45 cable (approx cat6 cable 15 rs/mtr) maximum distance of cat6 cable is 300mts without hub
3) if you dont have 2 ethernet port on current modem then buy a hub which i think it will have minimum 8 ports which may cost around 2k (or even less dont know)
choose which ever you feel good, try using cables i trust cable more than wireless...
