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: "spectral and energy spectral efficiency optimization of joint transmit and receive beamforming based multi relay mimo ofdma cellular networks"
  Abstract: We first conceive a novel transmission protocol for a multi-relay multiple-input–multiple-output orthogonal frequency-division multiple-access (MIMO-OFDMA) cellular network based on joint transmit and receive beamforming. We then address the associated network-wide spectral efficiency (SE) and energy spectral efficiency (ESE) optimization problems. More specifically, the network's MIMO channels are mathematically decomposed into several effective multiple-input–single-output (MISO) channels, which are essentially spatially multiplexed for transmission. Hence, these effective MISO channels are referred to as spatial multiplexing components (SMCs). For the sake of improving the SE/ESE performance attained, the SMCs are grouped using a pair of proposed grouping algorithms. The first is optimal in the sense that it exhaustively evaluates all the possible combinations of SMCs satisfying both the semi-orthogonality criterion and other relevant system constraints, whereas the second is a lower-complexity alternative. Corresponding to each of the two grouping algorithms, the pair of SE and ESE maximization problems are formulated, thus the optimal SMC groups and optimal power control variables can be obtained for each subcarrier block. These optimization problems are proven to be concave, and the dual decomposition approach is employed for obtaining their solutions. Relying on these optimization solutions, the impact of various system parameters on both the attainable SE and ESE is characterized. In particular, we demonstrate that under certain conditions the lower-complexity SMC grouping algorithm achieves 90% of the SE/ESE attained by the exhaustive-search based optimal grouping algorithm, while imposing as little as 3.5% of the latter scheme's computational complexity.

Connected through hyperedge HE-1 (induced by source paper "low complexity downlink user selection for massive mimo systems"):
  with members:
    - "a novel scheme for downlink opportunistic interference alignment"
    - "an esprit based approach for 2 d localization of incoherently distributed sources in massive mimo systems"
    - "optimal design of energy efficient multi user mimo systems is massive mimo the answer"
    - "resource allocation for cost minimization in limited feedback mu mimo systems with delay guarantee"
    - "scaling up mimo opportunities and challenges with very large arrays"
    - "on capacity of large scale mimo multiple access channels with distributed sets of correlated antennas"
    - "large system analysis of linear precoding in correlated miso broadcast channels under limited feedback"
    - "training and feedback optimization for multiuser mimo downlink"

Connected through hyperedge HE-2 (induced by source paper "a survey of multi objective optimization in wireless sensor networks metrics algorithms and open problems"):
  with members:
    - "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"
    - "energy efficient ofdma networks maintaining statistical qos guarantees for delay sensitive traffic"
    - "wireless sensor network virtualization a survey"
    - "markov decision processes with applications in wireless sensor networks a survey"
    - "accuracy of homology based coverage hole detection for wireless sensor networks on sphere"
    - "end to end reliability aware scheduling for wireless sensor networks"
    - "multiband spectrum access great promises for future cognitive radio networks"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"

Connected through hyperedge HE-3 (induced by source paper "energy efficient resource allocation for hybrid bursty services in multi relay ofdm networks"):
  with members:
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "relay selection with network coding in two way relay channels"
    - "physical network coding in two way wireless relay channels"

Connected through hyperedge HE-4 (induced by source paper "energy efficient joint congestion control and resource optimization in heterogeneous cloud radio access networks"):
  with members:
    - "energy efficient resource allocation optimization for multimedia heterogeneous cloud radio access networks"
    - "queue aware energy efficient joint remote radio head activation and beamforming in cloud radio access networks"
    - "inter tier interference suppression in heterogeneous cloud radio access networks"
    - "contract based interference coordination in heterogeneous cloud radio access networks"
    - "energy efficient resource assignment and power allocation in heterogeneous cloud radio access networks"
    - "fronthaul constrained cloud radio access networks insights and challenges"
    - "system architecture and key technologies for 5g heterogeneous cloud radio access networks"
    - "heterogeneous cloud radio access networks a new perspective for enhancing spectral and energy efficiencies"

Connected through hyperedge HE-5 (induced by source paper "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"):
  with members:
    - "limited feedback based interference alignment for interfering multi access channels"
    - "performance analysis and optimization for interference alignment over mimo interference channels with limited feedback"
    - "opportunistic downlink interference alignment"
    - "maximizing energy efficiency in multi relay ofdma cellular networks"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "a reconfigurable distributed algorithm for k user mimo interference networks"
    - "exploiting interference alignment in multi cell cooperative ofdma resource allocation"
    - "framework for link level energy efficiency optimization with informed transmitter"

Connected through hyperedge HE-6 (induced by source paper "energy efficient ofdma networks maintaining statistical qos guarantees for delay sensitive traffic"):
  with members:
    - "distributed energy spectral efficiency optimization for partial full interference alignment in multi user multi relay multi cell mimo systems"
    - "large scale mimo is capable of eliminating power thirsty channel coding for wireless transmission of hevc h 265 video"
    - "maximizing energy efficiency in multi relay ofdma cellular networks"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "qos aware base station selections for distributed mimo links in broadband wireless networks"
    - "statistical delay control and qos driven power allocation over two hop wireless relay links"
    - "the impact of qos constraints on the energy efficiency of fixed rate wireless transmissions"

Connected through hyperedge HE-7 (induced by source paper "joint transmit and receive beamforming for multi relay mimo ofdma cellular networks"):
  with members:
    - "energy efficiency optimization in relay assisted mimo systems with perfect and statistical csi"

Connected through hyperedge HE-8 (induced by source paper "secrecy transmit beamforming for heterogeneous networks"):
  with members:
    - "joint power control in wiretap interference channels"
    - "base station activation and linear transceiver design for optimal resource management in heterogeneous networks"
    - "five disruptive technology directions for 5g"
    - "achieving maximum energy efficiency in multi relay ofdma cellular networks a fractional programming approach"
    - "modeling heterogeneous network interference using poisson point processes"
    - "improving macrocell small cell coexistence through adaptive interference draining"
    - "enhanced intercell interference coordination challenges in heterogeneous networks"
    - "secure transmission with multiple antennas ii the mimome wiretap channel"

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)