Generally speaking, they are applicable to just about any digital communication
system. These techniques will comprise both coherent detection and noncoherent detection
principles. For illustrative purposes, we have chosen to provide detectors for Differential Quaternary
Phase Shift Keying (DQPSK) and Minimum Shift Keying (MSK) modulation schemes. These techniques
can also be extended to work for the higher order modulation schemes presented earlier in
Chap. 2. Each technique will be described by mathematical terms and accompanied with block diagrams.
Whenever possible, theoretical and/or simulation performance results will be provided. Lastly,
a comparison of some of the present techniques will be provided and several conclusions will be
drawn based on not only performance but also implementation complexity.
4.1 DIFFERENCE BETWEEN PRACTICE AND THEORY
When a signal is transmitted it will encounter the wireless multipath channel discussed in Chap. 3.
The received signal will have the following sources of degradation: sample timing offset, carrier frequency
offset, and carrier phase offset. The timing offset will be taken care of by the timing recovery
mechanism to be discussed in the latter chapters. The frequency offset will be taken care of by the
automatic frequency control (AFC) mechanism to be discussed in later chapters as well.
Pages:
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293