[STDS-802-16] choice of wimax physical layer parameters ?
Dear All,
Does any one have any idea why wimax forum have commonly chosen parameter below ? (Table 1 of http://www.wimaxforum.org/news/downloads/Mobile_WiMAX_Part1_Overview_and_Performance.pdf
)
BW : 10MHz
Sampling frequency: 11.2 MHz
FFT : 1024
cyclic prefix : 128
The set of parameter above does not work well for mandatory convolutional coding in ITU Vehicular B channel model, where ITU Veh-B happens quite often. The cyclic prefix is 11428 ns length while the channel impulse response of ITU Veh B is longer than that ! For your reference, the channel impulse response of ITU Vehicular B model is below
Relative delay (ns) | Average power (dB)
0 | -2.5
300 | 0
8900 | -12.8
12900 | -10.0
17100 | -
25.2
20000 | -16.0
As you can see, the relative delay is longer than 128 * ( 1/11.2e6 ) = 11428 ns (cyclic prefix) of the chosen parameter above ! This confuse me a lot, enlighten me please ? Many thanks.
Regards,
Arthur.