[ns] How to change the transmission range in 802.11 PHY

[Xiaolin Cheng]

Dear all,

In wireless-phy.cc, it says

    // Assume AT&T's Wavelan PCMCIA card -- Chalermek
    //    Pt_ = 8.5872e-4; // For 40m transmission range.
    //      Pt_ = 7.214e-3;  // For 100m transmission range.
    //      Pt_ = 0.2818; // For 250m transmission range.
    //    Pt_ = pow(10, 2.45) * 1e-3;         // 24.5 dbm, ~ 281.8mw

What is the formula behind these parameters? It seems Pt_ is not inversely
proportional to square of transmission range (Pt_1/Pt_2 != d2^2/d1^2). How
does it work?

If I want a 500m transmission range, what is the transmission power supposed
to be?

Thanks much for your help.