Medium Access Control (MAC) and Physical Layer (PHY) - CISE

4-June-07 P1901_PRO_016_r0
description of the SOT generation is always based on a 40 MHz clock, independently of the symbol type used
by the node. The number of active subcarriers in the SOT depends on the symbol type used.
The SOT is composed of OFDM symbols that may be generated with a complex 256-point IDFT as shown in
Equation 28.
Where
s
D,
i
− kD is a normalization factor
N ⎧ D 2
255
⎛ j2πk
⎞
⎛ j2πk
⎞⎫
( n)
= kDw
D ( n)
⎨∑
c(
k)
exp⎜
n⎟
+ ∑c(
k)
exp⎜
n⎟⎬
⎩ k=
1 ⎝ 256 ⎠ k=
255−N
D 2 ⎝ 256 ⎠⎭
Equation 28
− wD(n) is a windowing function, that follows Equation 22 and Equation 23. The duration of the windowing
function is between 6.4 μs and 8 μs depending on the transition duration and is depicted in Figure 18.
N W≤64 samples
N SYM=N IFFT=256 samples
Figure 18 SOT Windowing
− ND is 192 (Type I), 128 (Type II) or 64 (Type III), so that the frequencies occupied by the SOT are the same
as for the data and control symbols.
− c(k) = exp(jφk) where φk is a random phase picked from a uniform distributed random variable between
[0,2π[
Six of these symbols are concatenated to form the SOT.
Submission page 62 UPA-OPERA