Digital Signal Processing Reference
In-Depth Information
static input symbol vector slot 1
static input symbol vector slot 2
in
1
in
2
in
n-1
in
n
in
1
in
2
in
n-1
in
n
ε
1
ε
2
ε
n-1
ε
n
ε
1
ε
2
ε
n-1
ε
n
DFT-based subband filter receive slot 1
DFT-based subband filter receive slot 2
B
1
B
1
B
1
B
1
B
2
B
2
B
2
B
2
Weight factor depends
Equalization and phase-
in the subband filter.
A
A
A
A
on signal quality slot
i.
alignment are integrated
D
D
D
D
out
1
out
2
out
n-1
out
n
Interleaved ISSR output vector
Figure 5.13.
Simplified architecture of the interleaved issr decoder, for the case
of two receive slots. The interleaved issr decoder can be easily
extended to an arbitrary number of input slots. The weight of each
receive slot
i
is adjusted by gain factors B
i
.
and the reconstructed signal becomes available at the output in the form of a
single vector. The output signal is then fed back to the individual non-shared
sections of the issr module, where the relevant portion of the baseband spec-
trum is compared with the incoming symbol vector from each of the receive
units. Before the result of this comparison is reinjected into the common part
of the issr decoder, the fft-based filter corresponding to the respective re-
ceive unit removes frequency bands that do not contain valid information. This
process is repeated for every branch separately, based on continuous signal and
interference monitoring measurements. The circle is completed by merging the
time-domain error vector of every receive branch in the multi-input integrator
block of the shared issr section.
Asymmetrical processing branches
The previous analysis was done under the assumption of a flat power distri-
bution over all receive slots in the period of time between to pulses. In a line-
of-sight (los) channel, where the direct path between transmitter and receiver
offers a much stronger signal than the indirect propagation paths, the equally
distributed power assumption is no longer valid. For this reason, allocating
equal resources to each of the parallel receive branches in a pulse-based radio
