|Fig. (a) Illustration describing the differences between the considered systems. For a typical user of operator 1, the figure shows all accessible networks this user can connect to, all interfering networks, and the available spectrum after license sharing.||Fig. (b) Rate coverage in a two-network mmWave system with Rayleigh fading and BS antenna with 20o beamwidth. Shared licenses (Systems 3 and 4) perform better than exclusive licenses (System 1).|
Modeling Multi-operator mmWave cellular system and Analyzing gains of spectrum sharing
It is worth noting that communication at mmWave frequencies has non-trivial differences when compared to communication at conventional cellular frequencies (CCF). This leads to possibility of uncoordinated sharing among operators. The independent cellular operators who own licenses for separate frequency bands may agree to share the complete rights of operation in each other’s bands without any explicit coordination. Sharing licenses may allow all networks to use the full spectrum simultaneously without impacting the individual achieved rates and help operators to reduce their expenses by sharing the license costs.
In [1,2], we established the theoretical feasibility of spectrum license sharing among mmWave cellular operators. We presented a tractable model for a multi-operator system containing multiple independent cellular networks, each owned by an operator. We computed the performance in terms of the SINR and rate distribution for downlink mobile users of each network. Using the analysis, we compared systems with fully shared licenses and exclusive licenses for different access rules and explore the trade-offs between system performance and spectrum cost and showed that sharing spectrum licenses increases the per-user rate when antennas have narrow beams and is favored when there is a low density of users. We also consider a multi-operator system where BSs of all the networks are co-located to show that the simultaneous sharing of spectrum and infrastructure is also feasible.
In [3,4], we analyze secondary licensing for mmWave cellular systems. We consider a two-operator system where the first operator that primarily owns an exclusive-use license of a certain band can sell a restricted secondary license of the same band to the second operator. This secondary network has a restriction on the maximum interference it can cause to the original network. Using stochastic geometry, we derive expressions for the coverage and rate of both networks, and establish the feasibility of secondary licensing in licensed mmWave bands. To explain economic trade-offs, we consider a revenue-pricing model for both operators in the presence of a central licensing authority. Our results show that the original operator and central network authority can benefit from secondary licensing when the maximum interference threshold is properly adjusted.
 A. K. Gupta, J. G. Andrews, and R. W. Heath Jr, “On the feasibility of sharing spectrum licenses in mmWave cellular systems,” to appear in IEEE Trans. Commun., 2016 (ArXiv preprint).
 A. K. Gupta, J. G. Andrews, and R. W. Heath Jr, “Can operators simply share millimeter wave spectrum licenses?” in Proc. ITA, San Diego, CA, Feb. 2016 (Available here).
 A. K. Gupta, A. Alkhateeb, J. G. Andrews, and R. W. Heath Jr, “Gains of restricted secondary licensing in millimeter wave cellular systems,” submitted to IEEE J. Sel. Areas Commun., 2016 (ArXiv preprint).
 A. K. Gupta, A. Alkhateeb, J. G. Andrews, and R. W. Heath Jr, “Restricted Secondary Licensing for mmWave Cellular: How Much Gain Can be Obtained?,” in Proc. GLOBECOM, Washington DC, Dec. 2016