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Performance Evaluation of WiMAX/IEEE 802.16 OFDM Physical Layer - page 65 / 107

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Mod.

BPSK

QPSK

QPSK

16­QAM

16­QAM

64­QAM

64­QAM

Code rate

1/2

1/2

3/4

1/2

3/4

2/3

3/4

SNR (dB) at BER level 10­3

12.3

15.7

19.4

21.3

16.25

19.5

23.3

25.4

22.7

28.3

30

32.7

SUI­1

4.3

6.6

10

SUI­2

7.5

10.4

14.1

SUI­3

12.7

17.2

22.7

Table 5.1: SNR required at BER level 10 ­3 for different modulation and coding profile

Channel

Having observed the performance of different profiles under same channel models, let us observe the variations with the change in channel conditions. Figure 5.13 shows the performance of 16­QAM ½ on SUI­1, 2 and 3 channel models. It can be seen from the figure that the severity of corruption is highest on SUI­3 and lowest in SUI­1 channel model. The order of the severity of corruption can be easily understood by analyzing the tap power and delays of the channel models, since the doppler effect is reasonably small for fixed deployment. All the three models have same amount of corresponding tap except tap 3 of SUI­2 models has 0.2 µs larger than the corresponding tap of the other two models. But, in this case tap power dominates in determining the order of severity of corruption. SUI­3 has highest tap power value and SUI­1 has lowest value. delays

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