Zero-forcing beamformer design in MISO broadcast channel based on k-regularity

Abstract

In this thesis, we consider zero-forcing beamformer design in multi-input single-output (MISO) broadcast channel based on k-regularity. k-regularity (or k-regular structure) is a new beamformer design paradigm for massivemulti-inputmulti-output (MIMO) systems proposed by Lee et al. [1]. In k-regular beamforming structure, each data stream is assigned to k out of N available transmit antennas. Thus, each data stream is multiplied by only k complex gains instead of N before transmission. Two zero-forcing beam design problems under k-regular structure are considered. First, we tackle whether zero-forcing beamforming is feasible with k-regular structure in MISO broadcast channel. Then, the problem of how to determine the optimal position of k transmit antennas for each data stream is considered. The second problem can be solved by the combinational approach (bruteforce search), but it will incur intractable computational complexity. Two zero-forcing beam design algorithms under k-regularity based on successive elimination strategy are proposed to reduce the computational burden. The proposed algorithms are shown to yeild almost the same performance to that which can be obtained by the combinational approach while having much smaller computation complexity. Moreover, it is shown that proposed algorithms achieve superior performance than random selection algorithm.