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12.5.8.2
Mode 3 (Complex Correlation of 2× Oversampled Data), No
Decimation
The received training sequence is 2× oversampled (two pairs of I&Q samples per bit).
The midamble sequence consists of alternate pure real/pure imaginary values (one pure
complex value per bit). Before correlation, the midamble should be interpolated by 2.
Refer to the following table:
Sample
Bit #
(index)
0
1
2
3
4
5
6
7
Taking advantage of the "zero" components of the interpolated midamble sequence, we
get the following equations from the basic correlation equations:
FR n ( )
=
FI n ( )
=
When n is even, the filter outputs are independent of the odd input samples, and when n
is odd, the filter outputs are independent of the even input samples. As a result, even
and odd outputs can be calculated separately, requiring half of the data memory bank
size.
MOTOROLA
Table 12-9 2 × Oversampled Data Sequence
Received
Input
0
DR(0)
DR(1)
1
DR(2)
DR(3)
2
DR(4)
DR(5)
3
DR(6)
DR(7)
N 4 ⁄ 1
–
∑
(
( ) DR n
⋅
(
HR 4i
i
=
0
N 4 ⁄ 1
–
∑
(
( ) DI n
⋅
(
HR 4i
i
=
0
DSP56305 User's Manual
Received
Midamble
Quadrature
DI(0)
DI(1)
DI(2)
DI(3)
DI(4)
DI(5)
DI(6)
DI(7)
)
)
(
(
) DI n
+
4i
+
HI 4i
+
2
)
)
(
(
) DR n
⋅
+
4i
–
HI 4i
+
2
Filter Co-Processor
Operation Modes
Midamble
Input
Quadrature
HR(0)
0
0
0
0
HI(2)
0
0
HR(4)
0
0
0
0
HI(6)
0
0
⋅
(
)
)
+
4i
+
2
(
)
)
+
4i
+
2
12-37
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