3 dB. Hence we can achieve approximately 3.7 dB of performance
gain in using the coherent detection-based MBO.
The noncoherent (NC) performance is shown in Fig. 4.45, where we see using either a 3-bit or
5-bit observation window dramatically improved performance over the single-bit demodulator. Also
similar comments can be made regarding the BFSK modulation index value, b 0.715.
Increasing the observation window to 3 bits provides approximately 3.25 dB of gain. Further
increasing this window to 5 bits provides another 0.9 dB of gain. Hence the total gain shown is approximately
4.2 dB. A very interesting observation, made earlier in [26], is that the MBO can improve BER
performance to be better than that of coherent detection of QPSK (or antipodal signaling).
Some public results are worthy of mention here where they show the BER performance dependency
on the cutoff frequency of the LPF [99]. Here we see that as the BT product becomes smaller,
the performance degrades more rapidly as shown in [99]. In fact, there is approximately 1 dB of loss
for BER 1E-4 for BT 0.25 (see Fig. 4.46).
MODULATION DETECTION TECHNIQUES 211
MLDD Performance for 8DPSK in AWGN
1.E??“7
1.E??“6
1.E??“5
1.E??“4
1.E??“3
1.
Pages:
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353