Journal of China Universities of Posts and Telecommunications最新文献

In order to achieve the lateral control of the intelligent vehicle, use the bi-cognitive model based on cloud model and cloud reasoning, solve the decision problem of the qualitative and quantitative of the lateral control of the intelligent vehicle. Obtaining a number of experiment data by driving a vehicle, classify the data according to the concept of data and fix the input and output variables of the cloud controller, design the control rules of the cloud controller of intelligent vehicle, and clouded and fix the parameter of cloud controller: expectation, entropy and hyper entropy. In order to verify the effectiveness of the cloud controller, joint simulation platform based on Matlab/Simulink/CarSim is established. Experimental analysis shows that: driver's lateral controller based on cloud model is able to achieve tracking of the desired angle, and achieve good control effect, it also verifies that a series of mental activities such as feeling, cognition, calculation, decision and so on are fuzzy and uncertain.

For uniform linear antenna array (ULA) based millimeter wave communications, the maximum capacity can be achieved by the optimal antenna separation product (ASP). However, due to the practical size limitation, it is necessary to decrease the ULA length. In this paper, an optimization problem is formulated to minimize the ULA length for millimeter wave communications with maximum capacity. We decompose the problem into two subproblems: length selection optimization and orientation deployment optimization. The optimal length selection can be obtained when the transmit and receive ULAs have equal length. By using the property of trigonometric function, we derive the optimal orientation deployment and study the influence of orientation deviation on ULA length. Simulation results are presented to validate the analyses.

Packet loss cannot be avoided in wireless network due to wireless transmission medium particularity, therefore improving retransmission efficiency is meaningful to wireless transmission. The current retransmission packet selection mechanisms based on opportunistic network coding (ONC) face low retransmission efficiency and high computational complexity problems. To these problems, an optimized encoding packet selection mechanism based on ONC in wireless network retransmission (OONCR) is proposed. This mechanism is based on mutual exclusion packets and decoding gain concepts, and makes full use of ONC advantages. The main contributions of this scheme are to control the algorithm complexity of the maximum encoding packets selection effectively, avoid the redundancy encoding packets due to the overlapping among encoding packets, and take the encoding packet local and global optimization problem into consideration. Retransmission efficiency is evaluated according to the computational complexity, the throughput, the retransmission redundancy ratio, and the number of average retransmission. Under the various conditions, the number of average retransmission of OONCR is mainly lower than that of other typical retransmission packet selection schemes. The average retransmission redundancy ratios of OONCR are lower about 5%∼40% compared with other typical schemes. Simultaneously the computational complexity of OONCR is comparatively lower than that of other typical schemes.

This paper studies a multiple input multiple output (MIMO) simultaneous wireless information and power transfer (SWIPT) relay system, in which the source node (SN) send information and energy simultaneously to the relay node (RN), and the RN forward the received signal to the destination node (DN) powered by harvested energy. In particular, we consider two SWIPT receiver designs, namely power splitting (PS) and antenna switching (AS) in the relay system. For each design, iterative algorithms based on convex optimization technique are proposed to maximize the system rate. Furthermore, in order to strike a balance between computational complexity and system performance, based on the AS scheme, we propose a low complexity optimization method for PS scheme where a suboptimal PS ratio is given. Numerical results are provided to evaluate the performance of the proposed algorithm for MIMO SWIPT relay systems. It is shown that the performance of the proposed suboptimal method approaches that of the optimal PS scheme.

In this paper, channel spatial characteristics which mainly depend on the spatial correlation are selected as the significant factors in over-the-air (OTA) testing for multiple input multiple output (MIMO) devices. The multi-probe anechoic chamber method, a promising candidate of the MIMO OTA testing methods, can reproduce the multipath environments in a controllable manner. A novel physical configuration based on the variation of relative positions of probes in a MIMO OTA setup is put forward to obtain better spatial characteristics. Two physical configurations are presented to make a comparison with the typical configuration in this paper. The simulation results show that by making a proper probe configuration, good channel simulation accuracy can be achieved. Meanwhile, in order to get better performance of emulating channel spatial characteristics, probes in the first and the last probe rings should be placed symmetrically in three dimensional (3D) physical probe configuration.

As a key technology of the fifth generation (5G) wireless communications, sparse code multiple access (SCMA) system has quite high frequency utilization, but its message passing algorithm (MPA) decoder still has high time complexity. By the aid of the proposed multi-level dynamic threshold, the complexity of the MPA decoding can be greatly reduced with little error performance loss. In order to reduce a great deal of insignificant computational amounts of message update, we compare the multi-level symbols probability products with optimized multi-level thresholds step by step before they are used for message update calculation. The dynamic threshold configuration refers to the three factors: the level of input symbol probabilities, signal noise ratio (SNR) and the number of iterations. Especially, in the joint iterative MPA-Turbo decoding procedure, since most encoded bits have good convergence, the input thresholds can avoid more unnecessary computational overhead of message update and reduce the decoding time more significantly. The simulation results show that the proposed multi-level dynamic thresholds considerably reduce the decoding delay in both additive white Gaussian noise (AWGN) channel and frequency selective fading channel.

In order to take into account the computing efficiency and flexibility of calculating transcendental functions, this paper proposes one kind of reconfigurable transcendental function generator. The generator is of a reconfigurable array structure composed of 30 processing elements (PEs). The coordinate rotational digital computer (CORDIC) algorithm is implemented on this structure. Different functions, such as sine, cosine, inverse tangent, logarithmic, etc., can be calculated based on the structure by reconfiguring the functions of PEs. The functional simulation and field programmable gate array (FPGA) verification show that the proposed method obtains great flexibility with acceptable performance.

In millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems, because of the high hardware cost and high power consumption, the traditional fully digital beamforming (DBF) cannot be implemented easily. Meanwhile, analog beamforming which is implemented with phase shifters has high availability but suffers poor performance. Considering the advantages of above two, a potential solution is to design an appropriate hybrid analog and digital beamforming structure, where the available iterative optimization algorithm can get performance close to fully digital processing, but solving this sparse optimization problem faces with a high computational complexity. The key challenge of seeking out hybrid beamforming (HBF) matrices lies in leveraging the trade-off between the spectral efficiency performance and the computational complexity. In this paper, we propose an asymptotically unitary hybrid precoding (AUHP) algorithm based on antenna array response (AAR) properties to solve the HBF optimization problem. Firstly, we get the optimal orthogonal analog and digital beamforming matrices relying on the channel's path gain in absolute value by taking into account that the AAR matrices are asymptotically unitary. Then, an improved simultaneously orthogonal matching pursuit (SOMP) algorithm based on recursion is adopted to refine the hybrid combining. Numerical results demonstrate that our proposed AUHP algorithm enables a lower computational complexity with negligible spectral efficiency performance degradation.

With the popularity of variety delay-sensitive services, how to guarantee the delay requirements for mobile users (MUs) is a great challenge for downlink beamformer design in green cloud radio access networks (C-RANs). In this paper, we consider the problem of the delay-aware downlink beamforming with discrete rate adaptation to minimize the power consumption of C-RANs. We address the problem via a mixed integer nonlinear program (MINLP), and then reformulate the MINLP problem as a mixed integer second-order cone program (MI-SOCP), which is a convex program when the integer variables are relaxed as continuous ones. Based on this formulation, a deflation algorithm, whose computational complexity is polynomial, is proposed to derive the suboptimal solution. The simulation results are presented to validate the effectiveness of our proposed algorithm.

To detect uncorrectable frames and terminate the decoding procedure early, a probability stopping criterion for iterative analog decoding of low density parity check (LDPC) codes is proposed in this paper. By using probabilities of satisfied checks to detect uncorrectable frames and terminate decoding, the proposed criterion could be applied to analog decoders without much structure modifications. Simulation results show that the proposed criterion can reduce the average number of iterations and achieve a better balance in bit error ratio (BER) performance and decoding complexity than other stopping criteria using extrinsic information.