Abstract-In this paper, we present a QoS routing protocol called GVGrid for multi-hop mobile ad hoc networks constructed by vehicles, i.e., vehicular ad hoc networks (VANETs). GVGrid constructs a route on demand from a source (a fixed node or a base station) to vehicles that reside in or drive through a specified geographic region. The goal of GVGrid is to maintain a high quality route, i.e. a robust route for the vehicles' movement. Such a route can be used for high quality communication and data transmission between roadsides and vehicles, or between vehicles. The experimental results have shown that GVGrid could provide routes with longer lifetime, compared with an existing routing protocol for VANETs.
[1] The unique concept of the modified edge representation (MER) was proposed for the surface to the line integral reduction of the physical optic (PO). The equivalence between the MER line and the PO surface integration was analytically derived by using the Stokes theorem relations as well as asymptotic treatments, for the smooth scattering surfaces without inner stationary phase points (SPP). Later on, for the planar surface, the MER line integration around the inner SPP was investigated, and it was identified as the scattering geometrical optics (SGO). In this paper, findings related with the MER line integration around the inner SPP are extended to curved surfaces. The accuracy and the applicability of the SGO extraction in terms of the MER line integration are numerically investigated for different radii of curvatures of the scattering surfaces. Authors introduce a geometrical criterion for the applicability of the method. The MER line integration provides an alternative way to the stationary phase method or the classical geometrical optics for calculating SGO. In addition, this numerical result indirectly identifies the entity of the MER line integration along the periphery of the scattering illuminated region, irrespective of the position of observer, as not other than diffraction.Citation: Rodriguez, L., K. Yukimasa, T. Shijo, and M. Ando (2007), Inner stationary phase point contribution of physical optic in terms of the modified edge representation line integrals (curved surfaces), Radio Sci., 42, RS6S24,
We propose a compact, high-power, and highdirectivity surface-emitting terahertz (THz) source based on an array of active antennas with integrated patch antennas and resonant-tunneling diodes (RTDs). An array configuration of active antennas, each with an integrated patch antenna and two RTDs and coupled by microstrip lines, enables spatial power combining and improves directivity through coherent oscillation. We confirmed a maximum radiation power of 11.8 mW in a prototype 6 × 6 array at an oscillation frequency of 0.45 THz. Parasitic oscillation at low frequencies was suppressed by use of a bias stabilization circuit consisting of series-connected resistors and capacitors, and the dc to RF efficiency of this device was estimated to be approximately 1%. The radiant intensity of 210 mW/sr and the 3-dB beamwidth of 13°for the measured 6 × 6 array confirmed that directivity was improved by coherent oscillation based on mutual injection locking. The directivity of the patch antenna capable of surface emission can be controlled only by the number of antennas, even if there is no secondary radiator, such as an Si lens. The obtained results suggest that RTDs are promising as practical THz sources for realizing applications of THz imaging and 6G communication.
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