Implementation Issues of Cognitive Radio techniques for Ka-band (17.7–19.7 GHz) SatComs

Abstract

The usable satellite spectrum has become scarce due to continuously increasing demand for broadband multimedia, broadcast and interactive services. In this context, investigating efficient spectrum coexistence techniques is a crucial challenge in order to enhance the spectral efficiency of future satellite systems. Herein, we study a satellite-terrestrial coexistence scenario where a Fixed Satellite Service (FSS) downlink coexists with the Fixed Service (FS) point to point microwave links in the Ka-band (17.7-19.7 GHz). First, we identify various practical challenges and provide possible solutions in order to allow this coexistence. Then we propose four different sensing and avoidance schemes in order to protect FSS satellite terminals from the harmful FS interference. Further, we evaluate the performance of one of the proposed solutions in the considered scenario with the help of theoretical and numerical analysis. More specifically, we focus on harmful FS detection problem in order to guarantee the sufficient protection of FSS terminals. It is shown that the FS harmful interference can be reliably detected with the help of an additional dipole antenna and this solution further overcomes the noise uncertainty problem encountered while sensing with the satellite dish.

Cognitive Radio for Ka Band Satellite Communications

“…As for spectrum sensing, in this scenario the incumbent FS microwave links are protected from harmful interference of the cognitive terminals, and thus spectrum sensing techniques can be employed at the cognitive terminals within the cognitive zone in order to determine the bands where the interference received by the incumbent transmitters is below a predefined threshold. Thus, power estimation provides a valuable solution for Scenario B as well [17]. Moreover, the same observation on the activity of the BSS feeder links holds for the FS microwave transmitters, and thus a one-time sensing procedure seems to suffice, and the hidden terminal is not an issue in this scenario as well.…”

“…A one off sensing of the BSS interference at the proposed FSS terminal site e.g. by a horn scanning or dipole antenna in the azimuth plane might be sufficient [17]. However, this approach adds a high implementation cost to the system.…”

“…Target I/N=−10 dB, dipole sensing Target I/N=−10 dB, dish sensing Target I/N=−12 dB, dipole sensing Target I/N=−12 dB, dish sensing Target I/N=−6 dB, dipole sensing Target I/N=−6 dB, dish sensing Fig. 6: Required number of samples for successful harmful interference detection at the FSS terminal versus noise variance uncertainty [17].…”

“…Moreover, the same observation on the activity of the BSS feeder links holds for the FS microwave transmitters, and thus a one-time sensing procedure seems to suffice, and the hidden terminal is not an issue in this scenario as well. However, as in Scenario A, an azimuth steering horn antenna or dipole can be employed to measure the FS interference at the site of the terminal [17]. A limiting factor to measure the interference can be the noise variance uncertainty due to noise variance estimation error [18].…”

Cognitive spectrum utilization in Ka band multibeam satellite communications

“…As shown in Figure 3, in both cases, the spectrum sensing unit shares the obtained information with the database and network management units. Here again traditional sensing techniques such as energy detection and cyclostationary detection can be applied [9], [10].…”