spectral and error analysis of the DPPM is the same as that of the DPIM; the details can be found in Section 4.5.
Although every DPPM symbol ends with a pulse, thus displaying an inherent symbol synchronization capability at the receiver, a single slot error not only affects the corresponding symbol but also subsequent symbols, thus resulting in multiple symbol errors. There are two scenarios: (i) false alarm error—a pulse is detected in an empty slot following the pulse at the end of a symbol, thus resulting in the next symbol being demodulated in error, and (ii) erasure error—noise causing a pulse to be received as an empty slot, thus resulting in two symbols becoming one with the transmitted symbol being deleted and the next symbol being demodulated in error. Note that if error slots result in a run of empty slots longer than (L − 1) slots, then the error is detected, otherwise it is not detected.
For the AWGN channel, for any given L, DPPM has a slightly higher power requirement but a much lower bandwidth requirement compared with PPM. A MAP detector scheme to overcome the ISI due to multipath propagation is suggested in Ref. [38] with significant performance improvement and more than 10 dB less power requirement than the hard decision. The performance of DPPM with concatenated coding in a diffuse channel is reported in Ref. [39] in which a combination of marker and Reed–Solomon codes is used to correct insertion/deletion errors.
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