human: Given a hyperedge-centered hypergraph: <hypergraph>, where the center hyperedge is induced by one source paper and its member nodes are the cited papers.

Details of the hypergraph:
Center hyperedge (induced by source paper "low complexity downlink user selection for massive mimo systems"):
  Abstract: In this paper, we propose a pair of low-complexity user selection schemes with zero-forcing precoding for multiuser massive multiple-input–multiple-output downlink systems, in which the base station is equipped with a large-scale antenna array. First, we derive approximations of the ergodic sum rates of the systems invoking the conventional random user selection (RUS) and the location-dependent user selection (LUS). Then, the optimal number of simultaneously served user equipments (UEs),i.e.,   $K^\ast$  , is investigated to maximize the sum rate approximations. Upon exploiting   $K^\ast$  , we develop two user selection schemes, namely,   $K^\ast$  -RUS and   $K^\ast$  -LUS, where   $K^\ast$   UEs are selected either randomly or based on their locations. Both the proposed schemes are independent of the instantaneous channel state information of small-scale fading, therefore enjoying the same extremely low computational complexity as that of the conventional RUS scheme. Moreover, both of our proposed schemes achieve significant sum rate improvement over the conventional RUS. In addition, it is worth noting that, like the conventional RUS, the   $K^\ast$  -RUS achieves good fairness among UEs.

Includes members:
  Member "a novel scheme for downlink opportunistic interference alignment":
    also connected through other hyperedges:
      (none)
  Member "an esprit based approach for 2 d localization of incoherently distributed sources in massive mimo systems":
    also connected through other hyperedges:
      - Hyperedge HE-1 (induced by source paper "tracking position and orientation through millimeter wave lens mimo in 5g systems")
  Member "optimal design of energy efficient multi user mimo systems is massive mimo the answer":
    also connected through other hyperedges:
      - Hyperedge HE-2 (induced by source paper "rate splitting multiple access for multi antenna downlink communication systems spectral and energy efficiency tradeoff")
  Member "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks":
    also connected through other hyperedges:
      - Hyperedge HE-3 (induced by source paper "a survey of multi objective optimization in wireless sensor networks metrics algorithms and open problems")
  Member "resource allocation for cost minimization in limited feedback mu mimo systems with delay guarantee":
    also connected through other hyperedges:
      (none)
  Member "scaling up mimo opportunities and challenges with very large arrays":
    also connected through other hyperedges:
      - Hyperedge HE-4 (induced by source paper "downlink secrecy rate of one bit massive mimo system with active eavesdropping")
  Member "on capacity of large scale mimo multiple access channels with distributed sets of correlated antennas":
    also connected through other hyperedges:
      - Hyperedge HE-5 (induced by source paper "non bayesian activity detection large scale fading coefficient estimation and unsourced random access with a massive mimo receiver")
  Member "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback":
    also connected through other hyperedges:
      - Hyperedge HE-6 (induced by source paper "covariance aided csi acquisition with non orthogonal pilots in massive mimo a large system performance analysis")

Question: Please tell me which class the source paper belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.IT(Information Theory)