Directional antennas in ad hoc networks offer many benefits compared with classical omnidirectional antennas. The most important include significant increase of spatial reuse, coverage range and subsequently network capacity as a whole. On the other hand, the use of directional antennas requires new approach in the design of a MAC protocol to fully exploit these benefits. Unfortunately, directional transmissions increase the hidden terminal problem, the problem of deafness and the problem of ...

This paper presents a real-time utility based procedure for antenna tilt control in cellular networks. The method’s convergence to Nash equilibrium is guaranteed by the concave dependence between utility function and tilt angle. The solution was verified using a CDMA motion simulator with real path-loss data collected in downtown Delhi. The simulations show a significant reduction in dropped calls when the tilt is adapted to changes in traffic. This solution can be realized on systems that ...

One of the most important components of any mobile system is the antenna; antenna design can overcome or cause a number of problems that then must be addressed at other technology layers. Modern mobile platforms are beginning to include novel antenna technology such as MIMO and beam steering; these technologies increase the complexity of evaluating the effectiveness of topology formation algorithms,
routing and overall performance due to the large number of configuration states the system ...

Energy conservation is a critical issue in wireless ad hoc networks since batteries are the only energy source to power the nodes. One major metric for energy conservation is to route a communication session along the routes which require the lowest total energy consumption when all nodes are equipped with a finite and nonrenewable amount of energy. To explore advantages offered by the use of directional antennas, we consider the case of source initiated multicast traffic in wireless ad hoc ...

The communications subsystem is perhaps the most vital aspect of the operation of a spacecraft. The communications system provides the only link between an operational vehicle and the ground control station or other satellites. Examples of communicated data can include scientific research, telemetry, payload results, or relayed information from other spacecraft. This subsystem plays a crucial role in the proper functioning of the space system.