0E??“3)
0.1
1
10
??“2 2 6 10 14 18 22 26
Eb/No (dB)
C/W (Bps/Hz)
4-QAM
16-QAM
64-QAM
16-PSK
64-PSK
32-PSK
DPSK
DQPSK
8-DPSK
4-FSK
8-FSK
16-FSK
64-FSK
Bandwidth-Limited Area
Power-
Limited
Area
BFSK
BPSK
FIGURE 2.105 BW??“power efficiency plane characteristics for PSK, QAM, DPSK, and FSK
modulation schemes.
So, what can we determine by viewing this BW??“power efficiency plot? Well, given a modulation
scheme and a targeted BER, the communication system designer can then determine the BW efficiency
and the Eb/No required to maintain the average BER target.
First, there are two regions highlighted in the plot:BW-limited region and power-limited region. The
intention of these two regions is to classify the modulation schemes. For those modulation schemes
in the BW-limited regions, we notice they are highly efficient. Hence the communication system
designer should choose modulation schemes in the BW-limited region if there is a limitation of the
available BW for the wireless system. On the other hand, the modulation schemes in the power limited
region should be used when there is a limitation on the received power. More specifically the
BW??“power efficiency plot shows us if we have a BW constraint then PSK and QAM modulation
schemes look promising.
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