Error probability analysis of multicarrier direct sequence code division multiple access system under imperfect channel estimation and jamming in a Rayleigh fading channel

The performance of a multicarrier direct sequence code division multiple access (MC-DS-CDMA) system in fading environment has been extensively analysed in the literatures. The analysis that is available in the literatures did not take into account the impact of jamming and channel estimation errors on the performance of the system. In this study, closed-form expressions of the average bit error probability (BEP) of the MC-DS-CDMA system with channel estimation errors in the presence of partial band, broadband and multitone jamming are derived in a Rayleigh fading channel. The analysis shows that the magnitude of the normalised correlation between the actual and the estimated complex fading channel gain, A, greatly affects the performance of the MC-DS-CDMA system. For large signal-to-noise ratio, the average BEP with A=1 and without multiple access interference (MAI) tends to zero. When A?1, the BEP of the system exhibits an error floor even without MAI. This error floor increases as the number of users increases. It is also shown that increasing the number of the system subcarriers enhances the system performance against jamming.     

Changes in phytate and minerals during germination and cooking of fenugreek seeds

The effects of germination, cooking and roasting on the phytic acid content, total phosphorus, water soluble inorganic phosphorus and mineral content of fenugreek seeds have been estimated. After 96 h germination, the dry weight of fenugreek seeds decreased while total ash content increased. Phytase and phosphatase activity of the ungerminated and germinated seeds have been assayed. It is observed that during germination the phytic acid values diminish and the water soluble inorganic phosphorus values increase. Phytase activity which is absent in the ungerminated seeds originates after germination and the phosphatase activity is increased in the germinated seeds. Heat treatment practised in cooking and roasting fenugreek seeds has less effect on phytate elimination than does germination. Changes in calcium, magnesium, iron, manganese, copper and zinc are found to be dependent on the loss of dry weight which occurs during processing of fenugreek seeds.     

Adaptive channel estimation and equalization for rapidly mobile communication channels

This paper presents a reduced-complexity maximum-likelihood sequence estimation receiver, based on the Viterbi algorithm (VA), suitable for rapidly fading mobile communication channels. The channel impulse response is expanded onto a set of basis sequences and time-invariant (TI) expansion parameters. The proposed receiver continuously estimates the TI expansion parameters directly within the metric calculation of the VA. At every time instant of the VA, the accumulated metrics of the survivor paths are compared, and the survivors whose metrics are lower than the average value of the accumulated survivor metrics are retained. The other survivors are discarded from the trellis. Then the sequences associated with the minimum survivor of the retained survivors are used to update the estimate of the TI expansion parameters. The convergence properties of the estimation algorithm are investigated, and the steady-state value of the mean square error of estimation is derived. The performance of the proposed receiver is evaluated in terms of the symbol-error probability and compared with other receivers. The effects of time offset and frequency offset on the performance of the receiver are studied.     

Preliminary studies on the mucilages extracted from Okra fruits,Taro tubers,Jew's mellow leaves and Fenugreek seeds

Okra fruits, Taro tubers, Jew's mellow leaves and Fenugreek seeds are commonly used in Egypt to prepare popular diets with desired slimy consistency.The mucilages were extracted and preliminary studies conducted to characterise them physically. The pH values of a 1% solution of the mucilages varied from 6·9-7·5 for Okra and Taro, 7·1–7·8 for Jew's mellow, and 5·9-6 for Fenugreek, depending upon extraction conditions. The highest viscosity was observed in Okra solutions, followed by Fenugreek, Jew's mellow and Taro mucilages. Okra and Jew's mellow mucilages are acidic polysaccharides which contain higher amounts of ash than the Taro and Fenugreek mucilages which are neutral polysaccharides. All mucilages are associated with protein. Gel chromatography indicated strong interaction of protein with the polysaccharide. The acid hydrolysis of the mucilages followed by paper chromatography revealed that all mucilages contain methyl pentose, glucose, galactose, and fructose, in different proportions. Taro and Fenugreek mucilages are free of rhamnose. All mucilages are devoid of arabinose and mannose except Fenugreek which contained these two sugars.     

Trypsin inhibitor activity in vicia faba beans

Extracts of mature green, dry and germinated Vicia faba beans depressed the trypsin activity of casein. Germination of Vicia faba beans (for 60 h) lowered the trypsin inhibitor (TI) activity. 0.171M Saline was the most efficient extractant for the TI. Minimal amounts of the TI were extracted in the pH range 4 to 5. The TI of Vicia faba beans was undialysable. The inhibitor activity originated in the seeds at the beginning of pod formation and increased with development of maturity. TI was active only towards trypsin and inactive towards papain, rennin and pepsin. Chromatographing Vicia faba bean proteins, possessing antitryptic activity, on a column of DEAE-cellulose yielded six peaks, all of which possessed antitryptic activity.     

Adaptive signal detection over fast frequency-selective fading channels under class-A impulsive noise

The problem of adaptive detection of signals contaminated with Middleton's class-A impulsive noise and transmitted over a fast time-varying frequency-selective fading channel is addressed. Adaptive algorithms are derived to update the estimate of the channel parameters to the detector. A theoretical performance evaluation of the detector is provided. Computer simulations are performed to validate the theoretical developments.     

Multiple tone interference of multicarrier frequency-hopping BPSK system for a Rayleigh fading channel with channel estimation errors

In this paper, we analyze the error probability performance of an uncoded multicarrier frequency-hopping coherent binary phase-shift keying (MC-FH/BPSK) signal transmitted over a Rayleigh fading channel with multitone interference (MTI) and channel estimation errors. The channel estimation errors are modeled as Gaussian random variables. The performance in presence of worst case MTI is evaluated as a function of signal to noise ratio (SNR), signal to jamming ratio, and channel estimation errors. The effect of channel estimation errors on the error probability performance is investigated in presence and absence of MTI. It is shown, from the analytical results that when channel estimation errors are not neglected, the asymptotic error probability performance for high SNR exhibits an error floor even in the absence of MTI. Worst case MTI causes large increase in this error floor. It is also shown that increasing the subband order L enhances the system performance against multitone interference.     

Extractability and functional properties of some legume proteins isolated by three different methods

The extraction of protein from the flour of three grain legumes (faba beans, chick peas and fenugreek) was investigated using three different methods. Three protein preparations were made: by alkaline extraction and precipitation at isoelectric pH (protein isoelectric precipitate, PIP); extraction with 0.5 M sodium chloride solution and precipitation by ionic strength reduction (protein micellar mass, PMM); extraction in aqueous or saline solution in the presence of pepsin or pancreatin (partially hydrolysed protein preparation, PHP). Two of the protein isolates had higher values of water absorption and fat absorption compared to their corresponding parent flours, with fenugreek being the exception. Oil emulsification of the isolates was in the descending order: PMM, PHP and PIP. The PHP isolate had the highest nitrogen solubility index (NSI) values at pH 2.4 followed by PMM at pH 5.7–6.4 and finally PIP at pH 4.5–5.5.     

Oil-entrapped ranitidine HCl beads heal peptic ulcers via local and systemic mechanisms

Objective: Oral gastroretentive system is one of the site-specific drug delivery system, which is designed to be retained in upper GIT for a prolonged time. Ranitidine hydrochloride (RHCl), which is used frequently in treatment of peptic ulcer, is a suitable candidate for gastroretentive delivery systems. Dependently, floating oil-entrapped alginate beads of RHCl were developed and evaluated as an approach to site-specific delivery avoiding colonic degradation and enhancing both bioavailability and the proposed local effect.

Methods: Different formulations of floating beads were suggested and randomized using 2⁴ full factorial design. Optimized formulation was subjected for in vivo studies to measure the oral bioavailability and the healing effect of induced peptic ulcers.

Results: Beads size ranged from 1.32 to 2.3?mm. All beads revealed excellent floating capabilities. Optimum formulation (F12) has entrapment efficiency of 70%, drug loading of 7% and 71% RHCl released after 6?h. SEM of F12 shows a grossly spherical structure with presence of oil droplets distributed throughout structure. AUC obtained from F12 was nonsignificantly higher than that of a commercial tablet. Signs of ulcer healing appeared clearly with F12 through appearance of granulation tissue, collagen fibers and newly formed blood vessels. Healing rate and extent obtained with a commercial tablet were less than F12. Quantitative analysis confirmed histopathological findings.

Conclusion: Floating oil-entrapped beads are a promising approach for RHCl delivery to remain in stomach for a longer time ensuring site-specific delivery and consequently, enhancing local healing effect of peptic ulcers.