Enabling Secondary Access through Robust Primary User Channel Assignment

A common concept to mitigate the effects of spectrum scarcity is to allow opportunistic dynamic spectrum access (DSA) to licensed frequency bands. In this context, the license holder may experience a decrease in the performance of its network. For cellular networks this may lead to unwanted coverage holes at locations where the secondary-induced interference is too strong. In this paper we propose a planning tool and a channel assignment mechanism for cellular OFDMA-based networks that takes the coverage requirements of the primary system into account. By keeping a dynamic reserve of channels for those nodes that experience the highest interference, we can maximize spectrum utilization while guaranteeing a predefined service reliability. Our simulations show that only a small fraction of channels will need exclusive reservation, hence large parts of the spectrum may be employed in secondary systems.