1,881,837 research outputs found
Spectral characterisation of the dicode PPM format
No full textDicode pulse position modulation (PPM) is a new modulation format that offers improved sensitivity over digital PPM but at a reduced line-rate. This Letter considers, for the first time, the spectral characterisation of the dicode PPM modulation format and presents original expressions for predicting both the continuous and discrete spectrum
Implementation & Performance Investigation of Dicode PPM over Dispersive Optical Channels
No full textThis work is concerned with the development and investigation of a Dicode PPM (DiPPM) system.
A DiPPM coder was developed to code any input PCM signal into DiPPM format. A further investigation took place on the DiPPM spectrum and associated output. Software simulation and mathematical analysis of this PPM code was considered and comparison with previous theoretical results presented. Results show that DiPPM is an advantageous PPM code for optic communication; DiPPM spectrum is not concentrated near to DC and
it is possible to extract the DiPPM framerate
component directly from the pulse stream.
A timing extraction circuit that recovers the clock from a DiPPM sequence and synchronises the slots within the frames, was constructed successfully. This enabled transmission through fibre optics and Free Space Optics (FSO). The technique used for the timing extraction circuit of the DiPPM scheme gives an advantage over many of the PPM formats.
An optical transmitter/receiver system was developed and the DiPPM scheme was investigated through optical channels. Results show that the DiPPM sequence transferred through the optic system was not changed and the clock had been recovered. A DiPPM decoder was constructed and the received DiPPM signal returned to its original PCM form without errors.
Both DiPPM coder and decoder were developed in VHDL and measurements were taken. The timing extraction was programmed in VHDLAMS with the use of digital, analogue and mathematical equations.
DiPPM MLSD was also constructed in VHDL. Simulation results proved the theoretical
expectations
Spectral characterisation of nk pulse position modulation format
Get PDFnk pulse position modulation (PPM) is a new modulation format that has recently been proposed for the optical wireless channel. This Letter considers, for the first time, a full spectral characterisation of -PPM and presents original expressions, which are validated numerically, for predicting both the continuous and discrete spectrum
pmcharrison/ppm: ppm v0.1.1
No full textppm (R package) - Implements variants of the PPM statistical learning algorith
Optical wireless communications utilizing a dicode PPM PIN-BJT receiver
Get PDFOriginal results are presented for an optical wireless system employing dicode pulse position modulation (DiPPM) and a PIN-BJT receiver. When operating at and a bit rate of 10 Mb/s a sensitivity of –51 dBm (Pe=10-9) is achieved and this represents a 10.3 dB over an equivalent PCM system. The work also demonstrates that DiPPM achieves comparable sensitivities as that for the digital PPM format but at a significantly reduced line rates making it a credible candidate for mobile devices using optical wireless technology
nk-pulse position modulation for optical wireless communication
Get PDFAn original analysis is presented for nk-PPM in which the information is conveyed by the position of k pulses, each within their own frame of n-slots, giving nk-PPM symbols. Comparisons are made with multiple PPM (MPPM) and it is demonstrated that nk-PPM offers improved orthogonality; a simplified circuit implementation and comparable receiver sensitivity
PWM-based PPM format for dimming control in visible light communication system
Get PDFWe report simulation results of pulse width modulation (PWM)-based pulse position modulation (PPM) signal format for visible light communication systems. For simultaneous operation of data transmission and dimming control, PPM data format is added to PWM dimming control signal. To show dimming control, the PWM duty ratio is changed from 40 % to 80 % during PPM data transmission. The PWM frame rate is set to 1 kHz to avoid flickering in human eyes. The PPM data rate is set to 20 kb/s. The waveforms, eye diagrams and BER of this system are calculated. The simulation shows the BER of 1×10-5 is achievable
Manajemen rapat : kiat-kiat ampuh untuk menyelenggarakan rapat yang efektif dan produktif/ Penerbit PPM
No full textxi, 234 hal.: ill.; 23 cm
Program korban PPM di Kemboja
Get PDFPersatuan Pustakawan Malaysia (PPM) telah melaksanakan tanggungjawab sosial sambil beramal melalui program ibadah korban dan aqiqah di Kemboja sempena Hari Raya Aidildha 1434H. Negara Kemboja dipilih memandangkan minoriti saudara Islam yang sebahagian besarnya terdiri daripada etnik Melayu Champa yang menetap di sana hidup di paras kemiskinan. Kebanyakan mereka berasal dari Jawa berhijrah lebih 600 tahun dahulu yang mana bahasa yang digunakan ialah Khemer dan Champa serta menulis dalam jawi
Ultra-fast searching assists in evaluating sub-ppm mass accuracy enhancement in U-HPLC/Orbitrap MS data
Get PDFA strategy, detailed methodology description and software are given with which the mass accuracy of U-HPLC-Orbitrap data (resolving power 50,000 FWHM) can be enhanced by an order of magnitude to sub-ppm levels. After mass accuracy enhancement all 211 reference masses have mass errors within 0.5 ppm; only 14 of these are outside the 0.2 ppm error margin. Further demonstration of mass accuracy enhancement is shown on a pre-concentrated urine sample in which evidence for 89 (342 ions) potential hydroxylated and glucuronated DHEA-metabolites is found. Although most DHEA metabolites have low-intensity mass signals, only 11 out of 342 are outside the ±1 ppm error envelop; 272 mass signals have errors below 0.5 ppm (142 below 0.2 ppm). The methodology consists of: (a) a multiple internal lock correction (here ten masses; no identity of internal lock masses is required) to avoid suppression problems of a single internal lock mass as well as to increase lock precision, (b) a multiple external mass correction (here 211 masses) to correct for calibration errors, (c) intensity dependant mass correction, (d) file averaging. The strategy is supported by ultra-fast file searching of baseline corrected, noise-reduced metAlign output. The output and efficiency of ultra-fast searching is essential in obtaining the required information to visualize the distribution of mass errors and isotope ratio deviations as a function of mass and intensit
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