This thesis is a study of harmonized continuous phase modulation (H-CPM)
coupled with receive diversity as applied to mobile radio communication applications.
H-CPM is the modulation technique specified by the American Public Safety
Communication Official Project 25 (APCO P25) Phase 2 standards, which is focused on public safety applications. Practical implementation of an H-CPM maximum likelihood sequence estimator (MLSE) receiver requires complex reduction techniques to ensure a cost effective form. In addition, it must be able to handle a fast fading environment, which is often encountered in public safety applications. Here, the reduction of receiver complexity and the combating of fast fading situations are
investigated via MATLAB simulation.
By using tilted phase and frequency pulse truncation techniques, the
complexity of an H-CPM MLSE receiver is successfully reduced. In particular, the original 384-state receiver is first reduced to a 192-state receiver through the use of
tilted phase. Then it is further reduced to 48-states and finally to 12-states by applying frequency pulse truncation. Simulation, assuming static channels, shows that the bit
error rate (BER) performance of a 12-state receiver is essentially identical to that of a 384-state receiver, despite a 97% reduction in computational complexity.
To take into account the effects of fading, channel gain estimation via persurvivor processing (PSP) is incorporated into the reduced complexity MLSE receiver. Using a weighted-sum approach to the PSP gain estimates, it was found that
at Doppler shifts of 5 Hz, 40 Hz and 80 Hz, the receiver performance was comparable to that obtainable by rival techniques. To further reduce the effect of fading, receive diversity combining was investigated, where a three-antenna diversity scheme
is applied to the reduced state PSP-based MLSE receiver. Three different combining techniques, namely selective combining (SC), equal gain combining (EGC) and maximum ratio combining (MRC) were compared. It was found via simulation that the best performance is achieved using MRC, with as much as 14dB improvement achieved by applying triple diversity MRC.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/4455 |
| Date | January 2009 |
| Creators | Zhou, Li |
| Publisher | University of Canterbury. Department of Electrical and Computer Engineering |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Li Zhou, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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