Closed Loop Space-Time Block Coding for Wireless Downlink Transmission

In order to improve the poor performance of Space-Time Block Coding (STBC) in a downlink correlated fading environment, a closed loop scheme is proposed. With the known channel fading statistics fed from the receiver, eigenbeamforming is utilized to improve the performance of STBC at the transmitter. The new system achieves the array and diversity gain simultaneously. Because reduced dimension processing is adopted, the proposed system has a relative simple structure compared with the traditional beamforming system. The validity of the scheme is verified in several situations by simulation experiments.

Comparison of downlink transmission strategies for distributed antenna systems with multi-antenna arrays

In multi-user distributed antenna systems （DAS）, the scenario where each distributed antenna port is a multi-antenna array has not been comprehensively studied. In this article, four simple extended methods for downlink transmission are analyzed and compared in this scenario, two of which are based on the block diagonalization （BD） algorithm, namely joint BD and intra BD method. The other two methods are joint time division multiplexing （TDM） method and central antenna system （CAS） method. These four methods are evaluated through both theoretic analysis and insightful simulations. The theoretic analysis includes the receiving signal combination, post-processing signal to interference plus noise ratio （SINR） calculation. It shows that the intra BD method requires less channel state information at the transmitter （CSIT） and has lower computational complexity and process latency. Simulation results show that the joint BD method provides the best performance, and the intra BD method suffers little performance loss. Overall, the intra BD method is proved to be an optimal tradeoff which achieves high capacity, especially for the cell edge users, with relatively low complexity when power constraints are considered.

OFDMA-PON with MQAM downlink for flexible allocation

In this paper, the 40-Gbps orthogonal frequency division multiple access(OFDMA) technology enabled by subcarrier allocation in the form of integrated architecture for the intra-cell is proposed in the downlink transmission passive broadband optical access system. The data-carrying subcarriers in the inverse fast Fourier transform/fast Fourier transform(IFFT/FFT) size of1 024 points are successfully divided into three sub-channels,in which each sub-channel has 256 useful subcarriers, by using adaptive dynamic bandwidth allocation(DBA). Taking the inherent advantages of M-ary quadrature amplitude modulation(MQAM)modulation mechanism into account, the performance of the absolutely identical MQAM format over the different sub-channels for the downstream OFDMA-passive optical network(PON) is investigated based on the intensity modulation direct detection(IMDD) system by simulations. The results show that three parallel4 QAM or 16 QAM or 64 QAM OFDMA data, which are transmitted over three sub-channels, is more suitable for different sub-channel allocations, respectively. In addition, comparing with single port4/16/64 QAM OFDM over the same access system, the receiver sensitivity economizes – 0.6 d Bm, 0.6 d Bm, 4.6 d Bm at the bit error rate(BER) value of 10-3 respectively.

Multi-Resources Management in 6G-Oriented Terrestrial-Satellite Network

The six-generation(6G)wireless network is expected to satisfy the requirements of ubiquitous connectivity and intelligent endogenous.Terrestrialsatellite networks(TSN)enable seamless coverage for terrestrial users in a wide area,making it very promising in 6G.As data traffic in TSNs surges,the integrated management for caching,computing,and communication(3C)has attracted much research attention.In this paper,we investigate the multi-resource management in the uplink and downlink transmission of TSN,respectively.In particularly,we aim to guarantee both throughput fairness and data security in the uplink transmission of TSN.Considering the intermittent communication of the satellite,we introduce two kinds of relays,i.e.,terrestrial relays(TRs)and aerial relays(ARs)to improve the system throughput performance in the downlink transmission of TSN.Finally,we study a specific case of TSN with the uplink and downlink transmission,and the corresponding simulation results validate the effectiveness of our proposed schemes.

Novel scheduling strategy for downlink multiuser MIMO system: Particle swarm optimization

In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization （PSO） algorithm is introduced to address such problem. Two PSO scheduling methods with different objective functions applicable to different requirements on capacity and complexity are investigated. One is the capacity based PSO（C-PSO） scheduling method aiming at achieving the near optimal capacity; and the other is the lower bound of eigenvalue based PSO （LBE-PSO） scheduling method with the purpose of reducing computational complexity and at the same time achieving as large as possible capacity gain. Furthermore, convergence analysis of PSO from both the particle and the velocity aspects is also presented to derive the convergent condition, which is validated by several examples of different parameter values. Simulation results reveal that the C-PSO can obtain nearly the same capacity as the exhaustive search method with lower complexity, while the LBE-PSO provides a viable approach by striking a better tradeoff between capacity and computational complexity.