Spectrum sharing in the gray space

Abstract

There has been considerable effort to let more wireless devices operate in "white space" spectrum, i.e. within frequency bands and geographic areas where no wireless devices are active. Making white space available is certainly useful, but there are other sharing opportunities as well, some of which have been obscured by dangerous misconceptions about the concept of "unused spectrum." This paper discusses allowing more devices to operate safely in "gray space" spectrum, i.e. spectrum that is actively being used in that transmissions are underway -something many economic models assume is impossible. The paper focuses on primary-secondary sharing, so devices gaining access to spectrum operate on a secondary basis in a way that never causes harmful interference to primary systems. Examples of primary-secondary gray-space sharing mechanisms are described in which devices are allowed to share spectrum with broadcasting, radar, and cellular systems. Quantitative analysis shows that it is technically possible to support significant communications among secondary devices in spectrum that is already heavily used by cellular or radar. However, gray-space sharing generally causes primary and secondary systems to be more technically interdependent than white-space sharing, so different policy and governance structures are needed. Secondary market rules can support gray-space sharing in cases where there is a single primary spectrum user, such as a cellular carrier. In cases where technology is static, the regulator may be able to control access for secondary devices. However, in cases with multiple primary users and multiple secondary users of spectrum, as might be seen in bands with radar for example, a new kind of governance body will be needed to facilitate spectrum sharing.

On the sharing opportunities for ultra-dense networks in the radar bands

“…Moreover, results in [11], [12] showed that a predictable rotation pattern can further enhance the sharing opportunities for the secondary users. Some of these results were employed to identify initial policy reforms needed to facilitate the implementation of vertical spectrum sharing in the radar bands [29]. These previous investigations mainly targeted technical challenges while the regulatory policies to enable large-scale secondary access in the radar bands remains still underdeveloped.…”

Opportunistic Sharing Between Rotating Radar and Cellular

“…Even with an adequate margin, gray space sharing inherently introduces some risks that are not presented with white-space sharing, e.g., the power control mechanisms in a secondary system might be hacked and made to interfere with the primary system, or some system bug might cause a secondary transmitter to inaccurately calculate ˜ , . To mitigate the effects of interference in such cases, a new approach to regulation and governance is required, which is beyond the scope of this paper, but discussed in [6], [16].…”

“…For sensitivity analysis, the ranges of parameters considered -7] dB, adapted from [14]; d) radar rotating period ˠ in [4,6] s [13]. Fig.…”

“…Both of these are white space approaches to primarysecondary sharing, where secondary wireless systems are allowed to operate in frequency bands and geographic regions that are found to be entirely "unused" by any primary system. In contrast, with the gray space sharing [6] considered in this paper, a secondary device is allowed to transmit near a radar, but only when and with a transmit power that will not cause harmful interference. The maximum transmit power of secondary devices changes over time, based on the behavior of the primary system.…”

“…Even with an adequate margin, gray space sharing inherently introduces some risks that are not presented with white-space sharing, e.g., the power control mechanisms in a secondary system might be hacked and made to interfere with the primary system, or some system bug might cause a secondary transmitter to inaccurately calculate ˜ , . To mitigate the effects of interference in such cases, a new approach to regulation and governance is required, which is beyond the scope of this paper, but discussed in [6], [16].From (1), it is possible to calculate SDs' SINR, , which will in turn determine achievable data rates. This calculation is based on the conservative assumption that the time between radar pulses during which the secondary will not experience interference from the radar (which is typically less than 1 ms [13]) can be neglected.…”