Low Complexity Codeword Search Algorithms Base on Subspace Distance

Two subspace distance calculation algorithms are proposed for codeword search of limited feedback precoding multi-user MIMO systems. The equivalence of subspace distance and chordal distance are first proved, then the complexity of chordal distance calculation and proposed two subspace distance calculation algorithms are analyzed. Simulation results verify that subspace distance calculation algorithms cost fewer operations. Further more the proper one of two proposed algorithms can be chosen based on different hardware implementations and transmitting antenna numbers.