Intensity modulation and direct detection (IM/DD) is used in nearly all optical communication applications, such as wireless infrared communication links, inter-satellite links, and fiber-optic communications. Pulse position-based modulation is a power efficient scheme that is used with IM/DD.; The objective of this thesis is to develop and analyze new bandwidth efficient turbo-coded modulation schemes that are well-suited to those applications that use pulse position modulation (PPM). For this purpose, the study begins with the development of a new modulation scheme that offers higher spectral efficiency than traditional PPM and multiple PPM (MPPM) schemes. The new modulation scheme is called two-level two-PPM (2L2PPM) and it is a modified version of the existing MPPM modulation. The primary modification is to allow the pulses to have more than one amplitude level. Then two different serial-concatenated trellis-coded modulation (SCTCM) schemes with iterative decoding at the receiver will be presented. The first system is a serial concatenation of two convolutional encoders and a spread-random bit-interleaver combined with 2L2PPM. The second system has a rate-one inner code and is combined with overlapping PPM. Both SCTCM systems outperform previously reported coded modulation schemes by offering up to a 57% increase in spectral efficiency for the same power efficiency and decoding complexity.; In designing of the new SCTCM codes, we started with the derivation of performance bounds of serial-concatenated convolutional codes (SCCC) developed Benedetto et al., and modified them for the case of trellis-coded modulation (TCM) inner codes and spread-random bit-interleavers. Our modified design criteria will increase the effective Euclidean distance of the SCTCM codes for very large interleaver sizes compared with original SCTCM codes. Depending on the design criteria, we used a random search to find good inner codes that suit the two SCTCM schemes. Both Monte Carlo simulation results and upper bounds on the bit-error probability were used to evaluate the proposed turbo-coded modulation techniques.
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