Spreading Schemes Research Articles

Hybrid wavelength hopping/time spreading schemes for use in massive optical networks with increased security

Analysis of hybrid wavelength hopping/time spreading systems and their classification into symmetric and asymmetric systems (undercolored and overcolored asymmetric systems) is given. The characteristics of a hybrid system using extended quadratic congruence sequences for spreading and prime sequences and their cyclic shifts for hopping are examined. It is shown that the sequences exhibit excellent cross-correlation properties even in the case of a general asymmetric overcolored system. Analysis of the security properties of hybrid systems is presented both from the viewpoint of exhaustive search and from the viewpoint of chosen attack. Initial investigations indicate that the system can be so configured to allow high level of protection against determined attack, with this being especially true for an asymmetric system. Because of the massive number of users the system can support, the proposed scheme is suitable for large optical LAN's with increased security demands.

Integration of surface and groundwater resources for the development of Hamad Basin project

Hamad Basin (166,000 km2) is an extensive basin, inhabited by 219,000 souls. It is located in the arid region within the border of four Arab States: Syria, Jordan, Iraq, and Saudi Arabia. Average annual precipitation depth is 78 mm, falling mostly during winter. Integrated studies of the natural resources, (water, soil, range, and animal) were carried out with other complementary studies to formulate a socioeconomic development plan for the promissing areas within the basin. Modern technologies were applied such as remote sensing, isotope analysis, processing, and documenting of basic hydrogeological data within the data bank system using computer facilities. Results revealed that the output of the natural dry plant production amounts to 2.0 × 106 tons. Animal wealth comprise 2 × 106 head mainly of sheep. Average annual surface runoff is 146 × 106 m3, which could be appropriately exploited in water spreading schemes to improve range. Water lost presently through evaporation from vast flat depression (Khabra) could be conserved through deepening the Khabras, and recharging shallow perched aquifer by surface runoff, which could be mined later. Results of regional geology, partial geophysical studies, and hydrogeological, hydrochemical interpretations have concuded the existance of two main aquifer systems, the first lies within the tertiary and quaternary formations, while the second extends to the mesozoic, and paleozoic. Their yield varies quantitively and qualitively, up to 100 × 106 m3 could be safely drawn annually. One compound pilot project was selected within the sector of each of the four Arab States to test the feasibility of the proposed development program for the promissing areas of the basin.