Multi-criteria user selection scheme for learning-based multiuser MIMO cognitive radio networks

For multiuser multiple-input-multiple-output (MIMO) cognitive radio (CR) networks a four-stage transmiision structure is proposed. In learning stage, the learning-based algorithm with low overhead and high flexibility is exploited to estimate the channel state information (CSI) between primary (PR) terminals and CR terminals. By using channel training in the second stage of CR frame, the channels between CR terminals can be achieved. In the third stage, a multi-criteria user selection scheme is proposed to choose the best user set for service. In data transmission stage, the total capacity maximization problem is solved with the interference constraint of PR terminals. Finally, simulation results show that the multi-criteria user selection scheme, which has the ability of changing the weights of criterions, is more flexible than the other three traditional schemes and achieves a tradeoff between user fairness and system performance.     

D2D communication in a cellular network based on link adaptation with truncated ARQ

A device-to-device （D2D） communication mode underlaying cellular network in a single- cell environment is introduced. A practical method based on link adaptation with automatic repeat request （ARQ） is presented. Link adaptation technique, which combines adaptive modulation and coding （ AMC ） with truncated ARQ, can maximize the cellular UEs＇ data rate under prescribed delay and performance constraints. The proposed method can maximize the total transmission rate when an outage probability is determined. Numerical results show that with proper power control, the in- terference between the two links can be coordinated to increase the sum rate without overwhelming the cellular service.     

Feedback-based unequal error protection fountain code over device-to-device broadcast

To enhance encoding efficiency, an unequal error protection （UEP） broadcast scheme based on one additional feedback is proposed. Different from the equal probability selection for source packets in traditional fountain encoding, the proposed scheme calculates the packet loss ratio （PLR） according to the feedback results in systematic broadcast phase （SBP） and then optimizes the selection probability for source packets to guarantee higher level error protection for those source packets with larger PLRs. Thus the amount of unnecessarily redundant encoded packets during encoding broadcast phase （EBP） is decreased significantly. Numerical results show that the proposed scheme can recover 60% more packets than the traditional non-feedback broadcast scheme at the ex- pense of tolerably only one feedback procedure.     

分布式双向AF中继网络的线性联合多天线收发信机设计

Linear transceiver designs are investigated for distributed two-way relaying networks, which aim at minimising the Weighted Mean Square Error (WMSE) of data detections. The forwarding matrices at relays and equalization matrices at destinations are joi-ntly optimised. To overcome the challenging limitations introduced by individual power constraints, a Semi-Definite Relaxation (SDR) called element-wise relaxation is proposed, which can transform the original optimization problem into a standard convex optimization problem. In this research, two-way relaying is understood from a pure signal processing per-spective which can potentially simplify the theoretical analysis. Finally, simulation results are used for assessing the performance ad-vantage of the proposed algorithm.     

Low-complexity transceiver design scheme based on channel null-space feedback

To reduce the negative impact of channel quantization errors,a low-complexity transceiver joint design scheme for both the transmit beamformers and receive combining vectors is proposed in the two-user multiple-input multiple-output(MIMO) system.In the scheme,the channel null-space quantization vector is used as the transmit beamformer of the interference user directly based on channel null-space feedback.Since the interference can be determined at the receiver,interference rejection combining(IRC) is jointly utilized to cancel the inter-user interference.Simulation results show that the proposed scheme can provide substantial sum-rate improvement especially at high SNR.     

基于FPGA快速同步算法的研究

本文提出了一种基于FPGA的快速同步捕获方案,该方案采用相关峰尖锐的巴克码组作为帧头,帧同步捕获的同时实现位同步.仿真结果表明,该算法能够迅速实现位同步的捕获,且位定时抖动小,在信噪比较低的条件下仍有较好的性能.实际中将其应用于π/4-DQPSK调制方式,流水线结构,在ALTERA公司的FPGA芯片cycloneⅡ上实现.     

认知无线电系统中OFDM多用户资源分配算法

基于认知无线电技术特点和OFDM传输特性,提出一种OFDM多用户资源分配算法．认知无线电用户根据感知的资源状况,针对用户的带宽以及QOS等要求,通过对子载波和功率的分配使得整个信道容量达到最大．本算法引入“调度因子”来体现用户子载波分配过程中“比例公平”的原则,保障每个用户都能满足一定的通信要求;引入“衰减因子”和用户设备类型,在不干扰授权用户通信的前提下进行多用户之间分配子载波和功率．算法采用“二步法”,以降低计算复杂度,满足于认知无线电实时性要求．仿真结果表明所提算法相对于FDMA方案信道容量至少提高40％．