Analysis of direct-detection optical communication systems with multi-pulse pulse position modulation /
This dissertation investigates the issues of synchronization
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742535411&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This dissertation investigates the issues of synchronization for free space direct detection optical systems and sensitivity of direct-detection fiber optic receivers with multi-pulse pulse position modulation (MPPM) signaling. On comparing the performance of MPPM systems to the well studied PPM and on-off keying (OOK) signaling in direct detection optical communication systems, we conclude that in applications where there is a demand for higher throughput and/or receiver sensitivity under pulsewidth and peak or average power limitations, MPPM can be considered a viable alternative modulation scheme. MPPM (also referred to as combinatorial PPM) is a generalization of PPM that allows more than one pulse per modulation interval. While retaining all the advantages of PPM that make PPM desirable over OOK for power efficient direct-detection optical communications, such as low duty cycle and easily implementable receivers, MPPM offers a higher throughput for the same pulsewidth and symbol duration as PPM. MPPM also significantly reduces the required transmission bandwidth at the same transmission efficiency, compared to PPM. The performance of MPPM symbol synchronizers acting on finite length, randomly generated MPPM sequences in the presence of slot synchronization is investigated, where optimum (in a maximum likelihood sense) and suboptimum algorithms for both "soft" and "hard" decision data are derived and analyzed in terms of synchronization probability and through simulations. Synchronizable sequences that contain one or more synchronizable symbol pairs are identified, which when periodically inserted in the random data stream, remove the floor on synchronization probability. The detection of random MPPM sequences in the absence of symbol synchronization is studied, where maximum likelihood and joint synchronization and detection rules are derived, their performance analyzed through simulations and symbol detection probability. Optimum MPPM frame synchronization rules under both assumptions of prior slot synchronization and prior symbol synchronization are derived, approximations to them that are computationally easier to implement are identified and an upper bound to frame synchronization probability is obtained. Frame synchronizer performances are studied through these bounds and simulations. The problem of designing MPPM frame synchronization sequences (also referred to as markers) with good autocorrelation properties, using a maximum peak-to- sidelobe distance criterion under periodic correlation is studied for both prior slot and symbol synchronization cases. Upper bounds on the maximum peak-to-sidelobe distance are derived and some good frame synchronization sequences are generated through a computer search. Finally, we investigate the application of MPPM to extend the direct detection fiber optic receiver sensitivity over that which is offered by OOK and PPM receivers with PIN or APD photodetectors and results for the minimum average received optical power that is required by both optimum and suboptimum receivers to achieve a bit error rate of 10-' are presented. |
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| Item Description: | Vita. "Major Subject: Electrical Engineering". |
| Physical Description: | xii, 128 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |