How the capacity for WiMAX had been calculated ?

Can somebody enlighten me as to how the capacity has been calculted for WiMAX when it is said that
" A maximum of 35 Mbps is achievable for a 64 QAM over 7 MHz bandwidth.

2. How the coverage distance can be increased by lowering the frequency used.
As an example if we use 700 MHz, the coverage would be more than if we use some 3.5GHz freuency in WiMAX.

3. Can there be any significant difference in the capacity also in the lower frequency use.

I would require these technical inputs to write a paper. Please help me forum....

Thanks
Sidd

wimax range

for the coverage , it will increase because the free space loss depends on frequency as this equation explain :

Free space loss( dB) = 32.44+20*LOG10D+20*LOG10f
where f in MHz & D in Km

thats mean when frequency decrease losses decrease and so coverage increase

Added after 5 minutes:

for the coverage , it will increase because the free space loss depends on frequency as this equation explain :

Free space loss( dB) = 32.44+20*LOG10D+20*LOG10f
where f in MHz & D in Km

thats mean when frequency decrease losses decrease and so coverage increase

wimax free space loss

7MHz ; 64QAM let say rate 1/2
I dont know abt 7Mhz but i can tell u for 10 Mhz
For Downlink
We have to calculate the
Theoretical Thruput = 1/2* ( #Carriers (for pusc) / OFDMA symbol time(in usec))*6(in bits/subcarrier)

1/2 --> 1/2 CC rate
6 --> for 64 QAM the bit loading is 6 bits per subcarrier
Symbol time/ duration with CP =102.86 usec
#Carriers (for pusc) for BS tx = 840 sub carriers

THROUGHPUT = 24.49 Mbits/sec

WiMAX Range

aparnash2813 coment is quit correct. Let me just explain it to make it easily underestandable. If you go through my comment you will understand why aparnash2813 gave you that formula.
1/2 is channel coding rate. it means half of trasnmitted bits are redundant and have no extra information.
since your bandwidth is 10 MHZ so you sould transmit data in periods of 100usec length. but due to OFDM edge effect we have to increase the time interval (decrease in OFDM bandwidth). so you should send data in periods of 102.86 usec.
in each period 840 OFDM symbol is transmitted (they are orthogonal subcarriers). it means in each second 840/102.86usec OFDM sybmols are transmitted.
each symbol has 6 bit information (2^6 = 64) so the transmitted information should be calculaated as:

6*840/102.56usec*1/2