Joint Adaptive Transmission and Switched Diversity Reception - Adaptive Signal Processing in Wireless Communications - page 170

10 0

L = 2
L = 4
L = 8
L = 16
Option 1
Option 2

10 −1

10 −2

10 − 3

10 −4

10 −5

10 −6

0 5 10 15 20 25 30 35

Average channel SNR [dB]

FIgure 6.9 Average error rate of SECps-based bandwidth-efficient schemes for both options.

scheme can use a larger constellation than the SEC-based scheme since the best path is
used in this case. Comparing Figures 6.2 and 6.8 , we can conclude that the SECps-based
bandwidth-efficient scheme achieves nearly the same spectral efficiency as the SC-based
scheme. From Figure 6.9, we observe that similar to the SEC-based scheme, the BER per-
formance of the SECps-based bandwidth-efficient scheme with option 1 shows a more
significant improvement than with option 2 when the number of antennas increases.
But the difference is that now the BER improvement manifests over all the SNR region.
In fact, the average BER performance of the SECps-based bandwidth-efficient scheme
with option 1 is very similar to that of the SC-based scheme shown in Figure 6.3 .
We now compare the performances and spectral efficiencies of different schemes in
Figures 6.10 and 6.11 , respectively, for a fixed number of receive antennas ( L = 4). he
target BER is set to 10 -4 in these figures. In particular, the average BER performance of
different schemes with option 1 is shown in Figure 6.10. Note that we use subscript 1 to
denote the minimum estimation schemes based on SEC or SECps, and subscript N to
denote the bandwidth-efficient schemes. It can be seen that the SECps-based bandwidth-
efficient scheme offers nearly the same error performance as the SC-based scheme. The
complexity advantage of the SEC-based scheme comes at the cost of certain error per-
formance degradation. It is worth pointing out that for the high-SNR region, the aver-
age BER of the SEC-based bandwidth-efficient scheme becomes better than that of the
SECps-based minimum estimation scheme. Figure 6.11 compares the average spectral
efficiencies of different schemes with option 2. Again, the SECps-based bandwidth-
efficient scheme offers the same high spectral efficiency as the SC-based scheme. The
SEC-based minimum estimation scheme shows a certain spectral advantage over the
no-diversity case in the low-SNR region, whereas this advantage is more pronounced for