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: "linear precoding designs for amplify and forward multiuser two way relay systems"
  Abstract: Two-way relaying can improve spectral efficiency in two-user cooperative communications. It also has great potential in multiuser systems. A major problem of designing a multiuser two-way relay system (MU-TWRS) is transceiver or precoding design to suppress co-channel interference. This paper aims to study linear precoding designs for a cellular MU-TWRS where a multi-antenna base station (BS) conducts bi-directional communications with multiple mobile stations (MSs) via a multi-antenna relay station (RS) with amplify-and-forward relay strategy. The design goal is to optimize uplink performance, including total mean-square error (Total-MSE) and sum rate, while maintaining individual signal-to-interference-plus-noise ratio (SINR) requirement for downlink signals. We show that the BS precoding design with the RS precoder fixed can be converted to a standard second order cone programming (SOCP) and the optimal solution is obtained efficiently. The RS precoding design with the BS precoder fixed, on the other hand, is non-convex and we present an iterative algorithm to find a local optimal solution. Then, the joint BS-RS precoding is obtained by solving the BS precoding and the RS precoding alternately. Comprehensive simulation is conducted to demonstrate the effectiveness of the proposed precoding designs.

Connected through hyperedge HE-1 (induced by source paper "a survey on mimo transmission with discrete input signals technical challenges advances and future trends"):
  with members:
    - "asymptotic performance analysis of a k hop amplify and forward relay mimo channel"
    - "iterative distributed minimum total mse approach for secure communications in mimo interference channels"
    - "asymptotic analysis of su mimo channels with transmitter noise and mismatched joint decoding"
    - "secure massive mimo transmission with an active eavesdropper"
    - "interference aligned space time transmission with diversity for the 2 times 2 x network"
    - "space time encoded miso broadcast channel with outdated csit an error rate and diversity performance analysis"
    - "high snr asymptotics of mutual information for discrete constellations with applications to bicm"
    - "differential distributed space time coding with imperfect synchronization in frequency selective channels"

Connected through hyperedge HE-2 (induced by source paper "joint power allocation and beamforming for energy efficient two way multi relay communications"):
  with members:
    - "energy efficient power control a look at 5g wireless technologies"
    - "a survey of energy efficient techniques for 5g networks and challenges ahead"
    - "a survey on device to device communication in cellular networks"
    - "multiobjective signal processing optimization the way to balance conflicting metrics in 5g systems"
    - "sum rate maximization in two way af mimo relaying polynomial time solutions to a class of dc programming problems"
    - "on design of collaborative beamforming for two way relay networks"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

Connected through hyperedge HE-3 (induced by source paper "mse based precoding for mimo downlinks in heterogeneous networks"):
  with members:
    - "what will 5g be"
    - "joint source and relay precoding designs for mimo two way relaying based on mse criterion"
    - "decomposition by successive convex approximation a unifying approach for linear transceiver design in heterogeneous networks"
    - "cooperative multi cell block diagonalization with per base station power constraints"
    - "pilot contamination and precoding in multi cell tdd systems"

Connected through hyperedge HE-4 (induced by source paper "channel estimation and optimal training design for correlated mimo two way relay systems in colored environment"):
  with members:
    - "joint source and relay precoding designs for mimo two way relaying based on mse criterion"
    - "partially blind estimation of reciprocal channels for af two way relay networks employing m psk modulation"
    - "blind channel estimation for amplify and forward two way relay networks employing m psk modulation"
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

Connected through hyperedge HE-5 (induced by source paper "a modified levenberg marquardt method for the bidirectional relay channel"):
  with members:
    - "optimal beamforming for two way multi antenna relay channel with analogue network coding"

Connected through hyperedge HE-6 (induced by source paper "degrees of freedom for mimo two way x relay channel"):
  with members:
    - "the ergodic capacity of phase fading interference networks"
    - "an optimal coding strategy for the binary multi way relay channel"
    - "the multi way relay channel"
    - "physical layer network coding"
    - "interference alignment and the degrees of freedom for the k user interference channel"

Connected through hyperedge HE-7 (induced by source paper "a non alternating algorithm for joint bs rs precoding design in two way relay systems"):
  with members:
    - "transceiver design for multi user multi antenna two way relay cellular 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)