Showing posts from July, 2011


From two-way radios to the latest iPhone

How GPS Works with Presentation

G lobal Positioning System satellites transmit signals to equipment on the ground. GPS receivers passively receive satellite signals; they do not transmit. GPS receivers require an unobstructed view of the sky, so they are used only outdoors and they often do not perform well within forested areas or near tall buildings. GPS operations depend on a very accurate time reference, which is provided by atomic clocks at the U.S. Naval Observatory. Each GPS satellite has atomic clocks on board. E ach GPS satellite transmits data that indicates its location and the current time. All GPS satellites synchronize operations so that these repeating signals are transmitted at the same instant. The signals, moving at the speed of light, arrive at a GPS receiver at slightly different times because some satellites are farther away than others. The distance to the GPS satellites can be determined by estimating the amount of t

Distributed Optical Fiber Sensors and Their Applications

This presentation contains the theory behind optical fiber sensing measurement and the latest trends in optical fiber sensing measurement and its applications.Smart structures and materials in which an optical fiber acts as a sensor to measure distributed strain and/or temperature along the fiber have applications in health monitoring functions, such as preventive maintenance, product efficiency improvement, and maintenance cost reduction. Furthermore, optical fiber has the advantage that it is essentially explosion-proof, needs no electric power supply, and is not affected by outside noise, such as lightening or high-voltage electrical power lines. This makes optical fiber suitable for plant and civil applications.

Future Cooperative Wireless Networks

The density of nodes in mobile communication networks as well as the requirement for data throughput has increased steadily in the last decades. Since the available frequency spectrum is limited and bandwidth is a scarce resource, future communication systems are expected to utilize it as efficient as possible. In future systems, increased spectral efficiency (more bits per second per Hertz of bandwidth) as well as improved link reliability become even more important. In order to meet the continuously growing demands, extensive efforts are made to develop new standards for the evolution of existing third generation (3G) technologies. The next steps in the development of future cellular networks are the implementation of 3GPP long term evolution (LTE) technology and its upcoming fourth generation (4G) successor LTE-Advanced. The aim of next generation technologies is to provide mobile users with high data rates that meet the requirements for future cellular networks. LTE-Advanced of