An access technique for secondary network in downlink channels

In this paper, we present an access scheme which exploits the duplexing structure of licensed networks. It uses uplink sensing information to transmit in a downlink channel. In essence, this scheme decouples the sensing slot (or channel) from the access slot (or channel) in the secondary network and so avoids the sensing-throughput tradeoff. Considering pathloss and shadow fading with a certain degree of correlation between the sensing and transmission paths, we develop expressions for the interference power CDF. In addition, we derive the outage probabilities of both the primary and the secondary users. The results show that for a given primary user outage constraint, the secondary network can increase its power proportionally to the degree of correlation between secondary sensing and transmission paths. However, as pathloss becomes dominant (large primary user to secondary user distances) the sensing errors increase and the primary user outage probability behaves more like independent fading. The results indicate that this scheme is applicable to applications in which the intended secondary network range is less than 100m. All the numerical results are supported by monte-carlo simulations.