一种适用于密集车辆V2X网络的中继节点选择和功率分配优化方法简

密集车辆的V2X网络中由于车辆相对位置快速变动,需要低复杂度的快速中继节点选择算法和功率分配优化算法。本文利用V2X网络节点定期广播的心跳信息,提出了一种基于信道容量运算的中继节点选择和功率分配优化方法,避免了大量的循环迭代,满足V2X网络的要求。     

Resource allocation for OFDM relay systems with statistical QoS guarantees

By integrating the concept of effective capacity, we propose the resource allocation schemes for subcarrier‐pair based OFDM decode‐and‐forward and amplify‐and‐forward relay systems for quality‐of‐service (QoS) guarantees. The objective is to maximize the system throughput subject to a given statistical delay QoS constraint. First, we pair the subcarriers over the source‐relay channel and the relay‐destination channel by the descending order of the subcarriers' channel gains. Second, by making use of the derived equivalent end‐to‐end channel gains of the subcarrier pairs, we apply joint water‐filling power allocation over the subcarrier pairs and then partition the power of the subcarrier pairs between the source and the relay. We prove that as the equivalent end‐to‐end channel gains of the subcarrier pairs are given, the combination of sorted subcarrier pairing and joint water‐filling power allocation is jointly optimal to maximize the effective capacity. The simulation results show that our proposed schemes achieve the highest effective capacity for OFDM decode‐and‐forward and amplify‐and‐forward relay systems as compared with other existing schemes. The results also verify that our proposed schemes can efficiently provide different levels of delay QoS guarantees, even if under the stringent delay QoS constraints. Copyright © 2012 John Wiley & Sons, Ltd.     

Design of Distributed Beamforming for Dual‐Hop Multiple‐Access Relay Networks

This paper studies a dual‐hop multiple‐access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single‐antenna amplify‐and‐forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low‐complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches.     

Nakagami衰落信道下合作分集的无线家庭网络性能分析

提出在未来无线家庭网中采用合作分集的思想,通信时利用处于空闲状态的终端用户对所发送信息进行中继发送,保证整个网络误码率性能、中断概率以及发送功率达到最佳折衷.在Nakagami平衰落信道条件下研究了再生中继和非再生中继两种合作方式下的中断概率和误码率性能,给出误码率和中断概率的解析表达式,并用matlaab进行仿真,仿真结果表明,在低信噪比条件下再生中继大大优于非再生中继方式,但高信噪比条件下两者性能接近.     

在帧中继骨干网上传送话音的技术

在帧中继网上传送话音（ＶｏＦＲ）是帧中继网上的一项增值业务。本文提出该业务的主要障碍是话音分组的时延和丢弃；接着又介绍了克服这些障碍的技术，包括话音压缩、采用回波消除器和抖动缓冲器以及优先级技术等；最后又探讨了ＶｏＦＲ的兼容性和标准化问题。     

The nature of the bufferness phenomenon in weakly dissipative systems

We propose a mechanism for accumulating attractors in finite-dimensional weakly dissipative systems. The essence of this mechanism is that if a Hamiltonian or a conservative system with one and a half or more degrees of freedom is perturbed by small additional terms ensuring that it is dissipative, then under certain conditions, the number of its attractors appearing in small neighborhoods of different elliptic equilibriums or cycles of the nonperturbed system can increase without bound as the perturbations tend to zero. We consider meaningful examples from mechanics and radio physics: models of the bouncing ball dynamics, Fermi accelerations, the linear oscillator with impacts, and the self-excited oscillator with a discrete sequence of RLC circuits in the feedback circuit. __________ Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 146, No. 3, pp. 447–466, March, 2006.     

Comparison between relay propagation and direct propagation of Gaussian-Schell-model beam in turbulent atmosphere along a slant path

The relay propagation of Gaussian-Schell-model in turbulent atmosphere along a slant path is studied in this paper. Based on the extended Huygens-Fresnel principle and a quadratic approximation, an analytical formula of average intensity for Gaussian-Schell-model beams in turbulent atmosphere along a slant path is derived, and some special cases are discussed. From the study and the comparison with the direct propagation, we can see that the relay propagation has an advantage over the direct propagation. When the altitude of the target is low, the peak intensity of relay propagation is much larger than that of direct propagation. However, because of the limitation of the relay system aperture for relay propagation and the variation of coherence length for direct propagation, the difference in peak intensity between the two propagations decreases with the increase of the target altitude.     

电容投切开关动态响应分析与实验

电容器投切开关的动态响应时间是动态无功补偿装置的一个重要性能指标,对补偿的效果有很大影响。文中对基于固态继电器的电容投切开关的动态响应时间进行了理论分析,并通过实验证明其正确性,为无功补偿装置的选型提供参考,有实际应用意义。     

Cooperative HARQ protocol and diversity analysis of systems with multiple incremental relays

Wireless networks contain an inherent distributed spatial diversity that can be exploited by relays. Relay networks can take advantage of the broadcast-oriented nature of wireless transmission, but require more radio resource to transmit data for their multi-hop traits. Fortunately, incremental relaying technique, which can choose direct or multi-hop transmission adaptively, can efficiently utilize resource. In this article, the incremental transmission with amplify-and-forward (AF) relays is focused on. A practical hybrid-automatic retransmission request (HARQ) protocol is designed, and the related optimal relay selection strategy is proposed. To analyze the cooperative diversity of system with the proposed protocol, the capacity lower bound is deduced. Simulation and analytical results indicate that by adopting the optimal relay selection strategy, the system with the proposed HARQ protocol can achieve an order of cooperative diversity that equals the aggregated number of the relay and source nodes.     

基于湿簧继电器的外加电信号对激光光波控制的新方案

设计了一种利用湿簧继电器和外加信号源对光波控制的新方案,可以通过信号源控制激光光波输出的波形,波形周期等参数,提出了一种湿簧继电器的新的应用。实现了一种利用交流信号源对光路进行控制的新方法,并且具有驱动电压较低,稳定性较高,普遍适用等优点。