Global optimal bandwidth reservation and CAC of randomly distributed HCNs sharing same spectra

For heterogeneous cellular networks (HCNs) sharing the same spectra, the connection of high-mobility user equipment (UE) is a problem due to its short residence time in micro cell. In this paper, we try to reduce the handovers brought by high-mobility UEs through bandwidth reservation and connection admission control (CAC). We propose three modes of joint bandwidth reservation and CAC, from the points of increasing the residence time and providing large bandwidth for the high-mobility UE. Some high-mobility UEs in the micro cell can be connected to the macro BSs for larger residence time and the rest high-mobility UEs in the micro cell are connected to micro access points (APs) for much larger bandwidth. To deal with the tradeoff between network capacity and handover rate, a global network utility function is formulated based on stochastic geometry modeling for bandwidth reservation and CAC. A gradient descent method is given to obtain the optimal solutions of reserved bandwidths in macro BS and micro AP and the admission probability of high-mobility UE. It is observed from extensive simulation that these modes can significantly improve the global network performance and the third mode has the best performance.