Spatial coding for MIMO cognitive radio networks

The existing cognitive network can´t work together with licensed (primary) users´ network at the same frequency-time domain, and secondary users (SUs) of cognitive network only wait the frequency band occupied by primary users (PUs) to be free. To solve the problem, enlighten by the recent results of interference alignment (IA), this paper proposed a spatial coding approach for MIMO cognitive network, where a MIMO base-station with six antennas provides three different spatial codes for three users such as one PU and two SUs, then the SUs can share the bandwidth of PUs. Different from the results of IA, the proposed spatial coding approach for CR networks need not to encode and decode for mobile stations (MSs) collaboratively. The design of spatial codes´ for encoding and decoding vectors is given by some theorems, and the channel estimation algorithm for CR BS is provided. Simulation results verified the proposed approach.