The effect of cell phone radiation on human health is the subject of recent interest and study, as a result of the enormous
increase in cell phone usage throughout the world. Cell phones use electromagnetic radiation in the microwave range,
which some believe may be harmful to human health. Other digital wireless systems, such as data communication
networks, produce similar radiation. The objective of this survey is to review the effects of cell phones on human health:
A large body of research exists, both epidemiological and experimental, in non-human animals and in humans, of which
the majority shows no definite causative relationship between exposure to cell phones and harmful biological effects in
humans. This is often paraphrased simply as the balance of evidence showing no harm to humans from cell phones,
although a significant number of individual studies do suggest such a relationship, or are inconclusive.
KEYWORDS: Modulation, Signal to noise ratio, Gaussian filters, Modulators, Frequency modulation, Linear filtering, Digital filtering, Fermium, Optical filters, Electronic filtering
Gaussian minimum shift keying (GMSK) is a continuous-phase frequency-shift keying modulation scheme. It is similar
to standard minimum-shift keying (MSK); however the digital data stream is first shaped with a Gaussian filter before
being applied to a frequency modulator. This has the advantage of reducing sideband power, which in turn reduces out-of-
band interference between signal carriers in adjacent frequency channels. In this paper a new method of
premodulation filtered MSK called Laplacian minimum shift keying (LMSK) is proposed. LMSK is proposed as a
method for achieving good spectral efficiency over regular MSK, and it turns out to achieve improvement in error rate
performance over the known GMSK. To compare the behavior of the system under the proposed method, bandwidth
efficiency (i.e., bps/Hz), fractional out-of-band power and error rate performance in such systems are used. Results
show that the proposed LMSK attains good improvement in spectral efficiency over MSK; and in using LMSK we have
also good improvement in power efficiency over GMSK.
Minimum Shift Keying (MSK) is considered to be a spectrally efficient modulation scheme, in comparison with other
families of constant envelope modulation. However, its main sidelobe can be of some worry in digital data transmission,
particularly over nonlinear channels. Therefore, it is practically of interest to search for efficient pulse shaping schemes,
largely proposed either through baseband pulse shaping and/or filtering processing. In this paper a new pulse shaping
method based on Walsh functions is proposed to be used in MSK-type signaling. A methodology is proposed for
designing the optimum pulse shape; and this attains improvement in spectral efficiency (i.e., bps/Hz) over straight MSK,
for the same channel bandwidth. The fractional out-of-band power is used to compare the behavior of the system under
the new proposed technique. As well, error rate performance in such system is used in the evaluation of this work.
Results reveal that good improvement can be attained in spectral efficiency at the expense of error rate performance
when these functions are used.
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