This topic provides information on how to set up the downlink ratio and other system parameters to get the correct values for TTG and RTG as described in the WiMAX Forum system profiles and the 802.16 standards. The downlink ratio for each profile is derived through simple calculation.
|
Basic Parameters (see 8.4.2.4 in the 802.16 standard): Frame duration = 5 ms |
|||||
|
System BW (MHz) |
10 |
8.75 |
7 |
5 |
3.5 |
|
FFT Size |
1024 |
1024 |
1024 |
512 |
512 |
|
Sampling factor (n) |
1.12 |
1.142857143 |
1.142857143 |
1.12 |
1.142857143 |
|
Sampling frequency (Fs) |
11200000 |
10000000 |
8000000 |
5600000 |
4000000 |
|
Subcarrier spacing |
10937.5 |
9765.625 |
7812.5 |
10937.5 |
7812.5 |
|
Useful symbol time Tb (us) |
91.429 |
102.400 |
128.000 |
91.429 |
128.000 |
|
Cyclic prefix (G) |
0.125 |
0.125 |
0.125 |
0.125 |
0.125 |
|
Symbol time Ts = (1+G)Tb (us) |
102.8571429 |
115.2 |
144 |
102.8571429 |
144 |
|
PS = 4/Fs (us) |
0.357142857 |
0.4 |
0.5 |
0.714285714 |
1 |
Using the basic parameters given above, the DL ratio can be calculated using these equations:
DL subframe time = (Number of DL symbols) x Ts
DL ratio = (DL subframe time + TTG) / (Frame duration)
|
10 MHz |
296 |
168 |
35 |
12 |
74.1143% |
|
296 |
168 |
34 |
13 |
72.0571% |
|
|
296 |
168 |
33 |
14 |
70.0000% |
|
|
296 |
168 |
32 |
15 |
67.9429% |
|
|
296 |
168 |
31 |
16 |
65.8857% |
|
|
296 |
168 |
30 |
17 |
63.8286% |
|
|
296 |
168 |
29 |
18 |
61.7714% |
|
|
296 |
168 |
28 |
19 |
59.7143% |
|
|
296 |
168 |
27 |
20 |
57.6571% |
|
|
296 |
168 |
26 |
21 |
55.6000% |
|
|
8.75 MHz |
218 |
186 |
30 |
12 |
70.8640% |
|
218 |
186 |
29 |
13 |
68.5600% |
|
|
218 |
186 |
28 |
14 |
66.2560% |
|
|
218 |
186 |
27 |
15 |
63.9520% |
|
|
218 |
186 |
26 |
16 |
61.6480% |
|
|
218 |
186 |
25 |
17 |
59.3440% |
|
|
218 |
186 |
24 |
18 |
57.0400% |
|
|
7 MHz |
376 |
120 |
24 |
9 |
72.8800% |
|
376 |
120 |
23 |
10 |
70.0000% |
|
|
376 |
120 |
22 |
11 |
67.1200% |
|
|
376 |
120 |
21 |
12 |
64.2400% |
|
|
376 |
120 |
20 |
13 |
61.3600% |
|
|
376 |
120 |
19 |
14 |
58.4800% |
|
|
376 |
120 |
18 |
15 |
55.6000% |
|
|
5 MHz |
148 |
84 |
35 |
12 |
74.1143% |
|
148 |
84 |
34 |
13 |
72.0571% |
|
|
148 |
84 |
33 |
14 |
70.0000% |
|
|
148 |
84 |
32 |
15 |
67.9429% |
|
|
148 |
84 |
31 |
16 |
65.8857% |
|
|
148 |
84 |
30 |
17 |
63.8286% |
|
|
148 |
84 |
29 |
18 |
61.7714% |
|
|
148 |
84 |
28 |
19 |
59.7143% |
|
|
148 |
84 |
27 |
20 |
57.6571% |
|
|
148 |
84 |
26 |
21 |
55.6000% |
|
|
3.5 MHz |
188 |
60 |
24 |
9 |
72.8800% |
|
188 |
60 |
23 |
10 |
70.0000% |
|
|
188 |
60 |
22 |
11 |
67.1200% |
|
|
188 |
60 |
21 |
12 |
64.2400% |
|
|
188 |
60 |
20 |
13 |
61.3600% |
|
|
188 |
60 |
19 |
14 |
58.4800% |
|
|
188 |
60 |
18 |
15 |
55.6000% |
DL symbols in the table include 1 symbol for the preamble.