human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "practical implementation of spatial modulation"
  Abstract: In this paper, we seek to characterize the performance of spatial modulation (SM) and spatial multiplexing (SMX) with an experimental testbed. Two National Instruments (NI) PXIe devices are used for the system testing: one for the transmitter and one for the receiver. The digital signal processing (DSP) that formats the information data in preparation for transmission is described, along with the DSP that recovers the information data. In addition, the hardware limitations of the system are also analyzed. The average bit-error ratio (ABER) of the system is validated through both theoretical analysis and simulation results for SM and SMX under the line-of-sight (LoS) channel conditions.

Connected through hyperedge HE-1 (induced by source paper "a survey on spatial modulation in emerging wireless systems research progresses and applications"):
  with members:
    - "spatial modulation assisted multi antenna non orthogonal multiple access"
    - "adaptive spatial modulation based visible light communications ser analysis and optimization"
    - "two high performance schemes of transmit antenna selection for secure spatial modulation"
    - "receive spatial modulation for massive mimo systems"
    - "polarization shift keying polarsk system scheme and performance analysis"
    - "space time channel modulation"
    - "on the achievable spectral efficiency of spatial modulation aided downlink non orthogonal multiple access"
    - "spectral efficient analog precoding for generalized spatial modulation aided mmwave mimo"

Connected through hyperedge HE-2 (induced by source paper "polarization shift keying polarsk system scheme and performance analysis"):
  with members:
    - "performance of spatial modulation using measured real world channels"
    - "space shift keying ssk mimo with practical channel estimates"

Connected through hyperedge HE-3 (induced by source paper "adaptive ofdm index modulation for two hop relay assisted networks"):
  with members:
    - "index modulation techniques for 5g wireless networks"
    - "multiple input multiple output ofdm with index modulation"

Connected through hyperedge HE-4 (induced by source paper "compressive sensing based multiuser detector for the large scale sm mimo uplink"):
  with members:
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "generalised sphere decoding for spatial modulation"
    - "structured compressed sensing from theory to applications"
    - "subspace pursuit for compressive sensing signal reconstruction"

Connected through hyperedge HE-5 (induced by source paper "on multiple input multiple output ofdm with index modulation for next generation wireless networks"):
  with members:
    - "multiple input multiple output ofdm with index modulation"
    - "a tight upper bound on bit error rate of joint ofdm and multi carrier index keying"
    - "what will 5g be"

Connected through hyperedge HE-6 (induced by source paper "millimeter wave communications with oam sm scheme for future mobile networks"):
  with members:
    - "millimeter wave channel modeling and cellular capacity evaluation"
    - "energy efficiency evaluation of cellular networks based on spatial distributions of traffic load and power consumption"

Connected through hyperedge HE-7 (induced by source paper "generalized spatial modulation in large scale multiuser mimo systems"):
  with members:
    - "massive mimo for next generation wireless systems"
    - "performance of spatial modulation using measured real world channels"
    - "channel hardening exploiting message passing chemp receiver in large scale mimo systems"
    - "massive mimo systems signal processing challenges and research trends"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "generalised sphere decoding for spatial modulation"

Connected through hyperedge HE-8 (induced by source paper "generalised sphere decoding for spatial modulation"):
  with members:
    - "performance of spatial modulation using measured real world channels"
    - "sphere decoding for spatial modulation systems with arbitrary nt"
    - "space shift keying ssk mimo with practical channel estimates"
    - "low complexity maximum likelihood detection in spatial modulation systems"
    - "massive mimo how many antennas do we need"
    - "high rate space time coded large mimo systems low complexity detection and channel estimation"

Question: Please tell me which class the center node 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)