Efficient User Subset Selection for Multiuser Space-Time Line Code Systems

doi:10.1109/ACCESS.2022.3170033

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Efficient User Subset Selection for Multiuser Space-Time Line Code Systems

2022-01-01

Sangchoon Kim *

DOI：10.1109/ACCESS.2022.3170033

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Abstract

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This paper considers the problem of user subset (US) selection for minimizing the bit error rate (BER) of multi-user space-time line code (MU-STLC) multiple-input multiple-output systems with fairness-aware per-user power allocation. The optimal selection criterion suitable for MU-STLC transmissions based on zero forcing (ZF) precoding is given and two efficient algorithms are then proposed. First, an incremental search approach is presented for US selection in the MU-STLC systems. The proposed suboptimal solution to BER minimization starts an empty US and adds users one by one, where the lowcomplexity recursive computation of the block matrix inverse is further performed. Second, by avoiding recurring matrix computations in each incremental procedure of the first algorithm, a more efficient algorithm is developed. It is observed through simulation results that the proposed incremental-based algorithms achieve most US selection gains with very low complexity. In addition, it is demonstrated that when there are N-T transmit antennas, U users (each user has 2 receive antennas), and K selected users, the achievable upper diversity order of the ZF precoding-based MU-STLC systems with optimal US selection is given as 2(N-T - K + 1)(U - K + 1). The analytical diversity order is well-matched with simulation results.

Keywords:

User selection

multiple input multiple output (MIMO)

precoding

multiuser diversity

space-time line code