cordless phone solution

hi All

i have camp and i have 8 telephone lines in mobile car i need a cordless solution to cover an area with 1 KM2 the 8 lines are RJ11,

i am trying to use Aastra Business phone communication system with ericsson BPX but i afraid from complexity of Ericsson BPX and difficulties of deployment the base stations for the Aastra , i hope i can find solution to avoid using Ericsson PBX, i hope i can find something more reliable solution.

regards