This paper considers opportunistic primary-secondary spectrum sharing when the primary is a rotating radar. A secondary device is allowed to transmit when its resulting interference will not exceed the radar’s tolerable level, perhaps because the radar’s directional antenna is currently pointing elsewhere, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. We consider the case where a secondary system provides point-to-multipoint communications utilizing OFDMA technology in non-contiguous cells, as might occur with a broadband hotspot service, or a cellular system that uses spectrum shared with radar to supplement its dedicated spectrum. We show that even at a fairly small distance to a radar, extensive secondary transmissions are possible, although with some interruptions as the radar rotates. For example, at 35% of the distance at which secondary transmissions will not affect radar, on average, the achievable secondary data rates in down-and upstream are around 100% and 46% of the rate that will be achieved in dedicated spectrum, respectively. By evaluating quality of service, we find that spectrum shared with radar could be used efficiently for applications such as non-interactive video on demand, peer-to-peer file sharing, large file transfers, automatic meter reading, and web browsing, but not for applications such as real-time transfers of small files and VoIP.
