Research On High-Rate Transmission In Massive MIMO Systems With Limited System Resources

Massive Multiple Input Multiple Output(MIMO)can efficiently exploit spatial degree of freedom by deploying large number of antennas at the base station.It has advantages in improving system wireless transmission rate.Massive MIMO is taken as one of the key physical layer technologies in the future mobile communications,and has been included in the fifth generation mobile communication standard.However,massive base station antennas result in excessive system overhead,leading to conflict between limited system resources and increasing rate requirements.To achieve good performance mobile communications under limited overhead,this thesis focuses on high-rate transmission scheme design under different limited resources conditions.The main achievements are as follows:1.In order to overcome the challenges of high-cost hardware making massive MIMO systems difficult to deploy,we study the high-rate transmission under limited hardware.We propose a limited beamspace transmission scheme under a discrete lens array-based transceiver.This guarantees system sum rate while controlling system hardware cost using a mixed reduced-dimension channel in digital domain and spatial beams in analog domain.Then,we propose a joint beam selection scheme for analog domain precoding.By fully considering channel correlation among users,this scheme is able to avoid inter-user interference and maximize system sum rate.Moreover,a bio-inspired ant colony optimization-based algorithm is proposed by using positive feedback mechanism resulting in a near-optimal solution obtained with dramatically reduced computational complexity.Finally,simulations show the advantages of the proposed scheme in improving system sum rate,reducing system hardware cost and computational complexity.2.In order to overcome the challenge in massive MIMO systems being instantaneous channel state information difficult to estimate with high accuracy and highly associated with uplink pilot overhead,we study the high-rate transmission under limited pilot sequences in massive MIMO systems.A mixed imperfect instantaneous-statistical channel information transmission scheme is proposed by directly exploiting statistical channel information of users.This idea can avoid estimation for instantaneous channel information.To prove the feasibility of desired transmission scheme,we first propose a heuristic statistical precoding method and derive closed-form expressions of users' achievable rate.Then,we reveal the impact of the mutual interference between users on their achievable rate.Furthermore,the problem of downlink precoding design with mutual interference suppression is tackled as we propose an extended zero-forcing and an extended maximum ratio transmission precoding methods to minimize the total transmit power of base station and to maximize the received signal power of users,respectively.At last,the simulations are performed to validate the advantages of the proposed transmission scheme in improving achievable rate,system sum rate and spectrum efficiency.3.In order to overcome the challenge in massive MIMO systems resulting in highdimension channel feedback taking excessive time-frequency resources and impacting the data transmission,we study the high-rate transmission under limited feedback overhead.A covariance-based channel feedback mechanism is investigated in massive MIMO systems by introducing user statistical separability.Under the proposed feedback framework,the users are separated into two classes of feedback design,which achieves dynamic feedback overhead allocation among users.The key challenge lies in the design of a covariance-aware classification algorithm.First,a precoding method is devised and we build a prediction model for quantized instantaneous channel Then,we derive a system sum rate bound under single-cell and multiple-cell settings.Finally,the classifier is proposed with the purpose of maximizing the rate bound.Simulations are performed to validate the advantages of the proposed feedback scheme in sum rate under a global feedback overhead constraint compared to the traditional schemes.Our research achieves high-rate transmission of massive MIMO systems under limited hardware conditions,pilot sequences and feedback overhead,which provides theory and method support for high performance and low overhead mobile communications.