Stable distribution based analysis of transmission capacities for overlaid wireless networks

We study the transmission capacities of two coexisting wireless networks (a primary network vs. a secondary network) that operate in the same geographic region and share the same spectrum, where the primary (PR) network has a higher priority to access the spectrum without particular considerations for the secondary (SR) network, and the SR network limits its interference to the PR network by carefully controlling the density of its transmitters. Considering a general deterministic power-law channel model with a path-loss exponent ¿ > 2 and a constant transmission power, by applying the stable distribution theory and asymptotic analysis, we derive the transmission capacities for both of the two networks and quantify their tradeoff. Numerical results show that if the PR network permits a small increase of its outage probability, the sum transmission capacity across the two networks (i.e., the overall spectrum efficiency per unit area) could be boosted significantly over that of a single network, which generalizes our previous results in over a special case with a path-loss exponent ¿ = 4. By further comparing with our earlier results in, we find that Rayleigh fading can enhance the transmission capacity gain of the overlaid networks over that of a stand-alone PR network.