Читать книгу Dynamic Spectrum Access Decisions - George F. Elmasry - Страница 42

When primary users use directional antennas such as microwave links, the locations of the primary users and the directions of their RF beam – which include the azimuth and elevation angle – can be detected by the geographically dispersed spectrum sensors and leveraged by the secondary user's DSA decision‐making process to create opportunistic spectrum use. The spectrum sensing techniques will estimate the geolocation or position of the primary users and the direction of their beam. With a directional antenna, if a primary user is transmitting in a specific direction, the secondary user can transmit in the opposite direction without creating interference, as shown in Figure 2.17.

Figure 2.17 Directional secondary user's leveraging of the primary user's beam angle to create spectral opportunity.

Obviously, the case illustrated in Figure 2.17 points out to the importance of having a centralized arbitrator or the secondary user having knowledge of peer nodes location and the primary user nodes locations and signal characteristics.