Aiming at the problem of spectrum sharing in multiuser multi-input multi-output cognitive radio networks

a spectrum sharing method based on Frobenius norm is proposed

which is designed to maximize the throughput of cognitive radio (CR) users as well as guarantee the quality of service of primary (PR) users.Multiuser diversity of the cognitive radio network is obtained by user selection

which is according to the Frobenius norm of channel matrices

while twice selection is adopted to reduce the complexity of our method

and then the interference from CR users to PR users is canceled by null-space projection.At last

the singular value decomposition method is employed to derive the parallel spatial sub-channels for each user while the waterfilling power allocation method is used to enhance system capacity.Compared with the existing spectrum sharing strategies

the proposed method can acquire larger ergordic capacity of CR system and reduce the outage probability of PR users.Simulation results show that when the total transmitting power of the CR system is 100w

the proposed method has 13% ergordic capacity gain of the cognitive network over the existing methods.