A new performance bound for PAM-based CPM detectors

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.It is well understood that the pulse amplitude modulation (PAM) representation of continuous phase modulation (CPM) can lead to reduced-complexity detectors with near optimum performance. It has recently been shown that the PAM representation also extends to CPM schemes with multiple modulation indexes (multi-h CPM). In this paper, we present a detector for multi-h CPM which is based on the PAM representation. We also give an exact expression for the pairwise error probability for the entire class of PAM-based CPM detectors (single- and multi-h, optimal, and reduced-complexity) over the additive white Gaussian noise (AWGN) channel and show that this bound is tighter than the previously published bound for approximate PAM-based detectors. In arriving at this expression, we show that PAM-based detectors for CPM are a special case of the broad class of mismatched CPM detectors. We also show that the metrics for PAM-based detectors accumulate distance in a different manner than metrics for other CPM detectors. These distance properties are especially useful in applications with greatly reduced trellis sizes. We give thorough examples of the analysis for different single- and multi-h signaling schemes. We also apply the new bound in comparing the performance of PAM-based detectors with other reduced-complexity detectors for CPM

Leptin Affects Life History Decisions in a Passerine Bird: A Field Experiment

BACKGROUND: Organisms face trade-offs regarding their life-history strategies, such as decisions of single or multiple broods within a year. In passerines displaying facultative multiple breeding, the probability of laying a second clutch is influenced by several life-history factors. However, information about the mechanistic background of these trade-offs is largely lacking. Leptin is a protein hormone produced by white fat cells, and acts as a signal between peripheral energy depots and the central nervous system. In addition, leptin affects cells at all levels of the reproductive axis and plays a critical role in regulating the allocation of metabolic energy to reproduction. As such, it is possible that leptin levels influence the decision of whether or not to invest time and energy into a second clutch. Accordingly, we expect a treatment with exogenous leptin to result in an increased number of second broods. METHODOLOGY/PRINCIPAL FINDINGS: At a later stage during the first brood, female great tits were treated either with long-term leptin-filled cholesterol pellets (the experimental birds) or with pellets containing only cholesterol (the control birds). We found that leptin-treated females were significantly more likely to have a second brood and that the earlier females were more likely to lay a second clutch than the late females. CONCLUSIONS/SIGNIFICANCE: As both timing of first brood and treatment with leptin were important in the decision of having multiple broods, the trade-offs involved in the breeding strategy most likely depend on multiple factors. Presumably leptin has evolved as a signal of energy supply status to regulate the release of reproductive hormones so that reproduction is coordinated with periods of sufficient nutrients. This study investigated the role of leptin as a mediator between energy resources and reproductive output, providing a fundamentally new insight into how trade-offs work on a functional basis

Incompatibility of Trellis-Based Noncoherent SOQPSK Demodulators for Use in FEC Applications

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, CaliforniaInternational Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

AN ALTERNATE PROPOSAL FOR ARTM CPM

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, CaliforniaSince the Advanced Range Telemetry (ARTM) program first proposed the use of multi-h continuous phase modulation (ARTM CPM), there has been much work done to characterize the performance of this waveform. The ideal performance of ARTM CPM is well understood and has been shown to be close to that of PCM/FM and the Tier I modulations (FQPSK-B and SOQPSK). In practice, however, ARTM CPM is very sensitive to phase noise at the receiver and also requires very long synchronization times. These difficulties can be addressed with additional link margin. In this paper we propose an alternate set of modulation indexes which are approximately 2 dB superior in performance with respect to the original set (we use minimum distance concepts to characterize the performance of each set). Brief consideration is also given to frequency pulses other than the existing raised cosine (RC) pulse. We also characterize the effect these new parameters have on the signal spectrum. This 2 dB gain gives ARTM CPM some of the system flexibility currently enjoyed by PCM/FM and the Tier I modulations. One such option is to realize this 2 dB gain using low-complexity coherent detection schemes, which we demonstrate; we also show a noncoherent detection scheme that performs within 2 dB of optimum (or in other words, it has the same performance as the existing coherent detector for ARTM CPM). This is significant since noncoherent detection avoids some of the synchronization burdens that have plagued ARTM CPM thus far.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection