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: "expurgated ppm using symmetric balanced incomplete block designs"
  Abstract: In this letter, we propose a new pulse position modulation (PPM) scheme, called expurgated PPM (EPPM), for application in peak power limited communication systems, such as impulse radio (IR) ultra wide band (UWB) systems and free space optical (FSO) communications. Using the proposed scheme, the constellation size and the bit-rate can be increased significantly in these systems. The symbols are obtained using symmetric balanced incomplete block designs (BIBD), forming a set of pair-wise equidistance symbols. The performance of Q-ary EPPM is better than any Q-ary pulse position-based modulation scheme with the same symbol length. Since the code is cyclic, the receiver for EPPM is simpler compared to multipulse PPM (MPPM).

Connected through hyperedge HE-1 (induced by source paper "hadamard coded modulation for visible light communications"):
  with members:
    - "hadamard coded modulation an alternative to ofdm for optical wireless communications"
    - "application of expurgated ppm to indoor visible light communications part i single user systems"
    - "high speed visible light indoor networks based on optical orthogonal codes and combinatorial designs"

Connected through hyperedge HE-2 (induced by source paper "hadamard coded modulation an alternative to ofdm for optical wireless communications"):
  with members:
    - "application of expurgated ppm to indoor visible light communications part i single user systems"
    - "the papr problem in ofdm transmission new directions for a long lasting problem"

Connected through hyperedge HE-3 (induced by source paper "self synchronizing pulse position modulation with error tolerance"):
  with members:
    - "high rate self synchronizing codes"
    - "optimal partitioned cyclic difference packings for frequency hopping and code synchronization"

Connected through hyperedge HE-4 (induced by source paper "application of expurgated ppm to indoor visible light communications part ii access networks"):
  with members:
    - "application of expurgated ppm to indoor visible light communications part i single user systems"
    - "high speed visible light indoor networks based on optical orthogonal codes and combinatorial designs"

Connected through hyperedge HE-5 (induced by source paper "high speed visible light indoor networks based on optical orthogonal codes and combinatorial designs"):
  with members:
    - "application of expurgated ppm to indoor visible light communications part i single user systems"

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)