无线协作网络的物理层网络编码研究进展

随着网络编码技术的发展和对干扰无线信 道的研究,提出了无线多源信息的物理层网络编码,它能够有效融合干扰并提高无线网 络的频谱效率。本文从物理层网络编码的研究背景和研究进展介绍了无线协作网络的物理层 网络编码。本文从几种中继技术入手,针对多源中继系统,介绍了典型模拟网络编码 和数字网络编码的特征和性能,同时也给出了作者的部分工作。本文对中继通信和无线 网络编码的研究有一定参考价值。     

物理层网络编码研究进展

在无线协作环境下,充分利用无线电磁波的广播特性进行物理层网络编码(PLNC)可获得更大的吞吐量和频谱利用率。在物理层网络编码基本思想的基础上,首先着重介绍三类物理层网络编码技术--有限域上的物理层网络编码、模拟网络编码和复数域上的网络编码,给出它们相关理论的研究现状,并对与此相结合的新技术进行了介绍;然后论述目前物理层网络编码应用实现的现状;最后对物理层网络编码相关理论及其应用实现的发展趋势进行了分析与展望。物理层网络编码理论的进一步完善,相关安全性的研究,以及与协作通信理论,如信道编码与调制、中继选择、调度及资源分配等进一步紧密结合等,将是其研究的重要趋势。     

速率自适应的软网络编码方案

针对双向无线中继信道链路的时变性,提出了速率自适应的软网络编码方案.构造了基于软信息的网络编码中继协作方案,并通过对网络容量的估计,实现了自适应速率网络编码.仿真结果表明:速率自适应的软网络编码方案大大降低了中继节点的计算复杂度和功耗,所能达到的信息速率优于固定速率下的网络编码策略,能够适合不同的传输质量需求,在保持较...     

双向中继网络中的物理层网络编码方案

双向中继系统中的物理层网络编码可以有效的提高无线中继网络的吞吐量,受到了普遍关注。为了提升物理层网络编码在无线信道中的性能,提出了联合网络编码与信道编码设计思想。在联合信道编码-网络编码思想基础上,提出了一种结合LDPC信道编码和网络编码的线性性质来提升网络编码在双向中继系统中的性能,并最后给出该方案的误码率仿真图。     

多源分布式协作空时网络编码系统的设计

为改善传统空时编码协作方案中节点功率消耗过高和传输效率较低的问题,在多信源、单中继协作网络中提出一种新的空时网络编码方案。该方案利用中继节点的多天线优势实现接收分集,并在中继节点设计空时网络编码,再按照编码矩阵特点转发信号到目的节点。仿真验证了信源数、中继天线数不同时的系统性能,并分析了传统空时编码协作方案与提出方案的性能差距和传输效率,得出该方案是一种易于实现,性能良好的高效无线数据传输方式的结论。     

无线中继网络中基于方向天线的MAC协议

无线中继网络是指网络中的节点互相通信成为中继节点之间,中继节点之间距离很近可以形成协作分集,该文对这种网络进行了研究,引入多天线技术(MIMO)中的波束成型技术来消除信道间干扰,实现并行传输数据,分析了协作传输策略,结合协作传输策略对中继节点的功率分配进行了优化,基于合协作传输策略设计了一种基于方向天线的MAC协议.经过分析和实验仿真,基于MIMO波束成型的协作传输方法在相同情况下比其它的方法增加15％以上的信道容量.     

网络编码在无线中继网络中的应用研究

介绍网络编码在无线中继网络中应用的研究进展,指出其2个典型应用场景是双向对传网络和组播重传网络。阐述研究中需要解决的关键问题：(1)设计具体的实现协议;(2)在实际网络条件下,采用网络编码后的网络容量及可达该容量的传输策略;(3)针对物理层网络编码,从混合信号中分离出需要的信号。此外,展望该应用的发展趋势。     

无线充电传感器网络能量效率优化研究

本文将SWIPT技术应用到无线充电传感器网络中,提出了一种基于SWIPT的协作传输协议（简称CTS）,利用无线信息和能量的协作传输来提高无线能量传输的效率。在此基础上,设计了一个以最大化网络效用为目的的资源分配策略优化问题,并提出RAPOA算法来求解问题。仿真实验表明CTS最大化了网络效用,提高了无线充电传感器网络的能量传输效率。     

通信网络中基于协作中继重传策略

针对信息包在通信网络中多播传输进行了研究,提出通信网络中基于协作中继重传策略。当信息包直传失败时,源节点协作多个中继节点对多个丢失的信息包进行编码重传。在重传阶段根据反馈机制结果采取随机接入方式优先对有机会编码的丢失信息包进行组合,然后通过牺牲之前重传过程中传输失败的节点为信息提供空间分集增益,从而减低重传次数。最后在不同信道环境下,该策略与未协作NCARQ和传统ARQ进行Monte Carlo仿真。仿真结果表明,在多中继信道条件优于源-目的信道的情况下,利用协作网络编码进行重传有效地提高网络吞吐量,且该策略利用协作空间分集降低了由于相干性而导致性能不佳的状况。     

无线Mesh网的物理层网络编码方案

无线网状网是传统组网方式的变革,网中的节点之间相互通信,构成多点到多点的网状结构,是一个大型的无线中继网络,对无线中继网络物理层的研究集中于网络编码,以及结合逼近香农极限的良好性能的低密度奇偶校验码,提出了基于物理层的结合网络编码和信道编码的方案,该方案不仅利用了双向中继的提升吞吐率的特性,而且设计了并行迭代算法来降低译码的复杂度。     

Robust power allocation algorithm for analog network coding with imperfect CSI

Power allocation promises significant benefits in wireless networks. However, these benefits depend on knowledge of the channel state information （CSI）, which is hardly perfect. Therefore, robust algorithms that take into account such CSI uncertainties play an important role in the design of practical systems. In this paper, we formulate the power allocation problem as the maximum individual outage probability minimization subject to total power consumption for analog network coding （ANC） protocol of a two-way relay system. We show that these problems can be cast as convex optimization problems. Non-robust power allocation algorithm is first developed under the ideal assumption of perfect CSI. Then we introduce robust optimization methodology that accounts for the imperfect CSI. We show that ignoring CSI uncertainties in our designs can lead to drastic performance degradation. On the other hand, the proposed robust power allocation provides significant performance gain over non-robust power allocation and uniform power allocation in terms of overall system outage probability over a wide range of channel estimation errors. This work highlights the importance of the proposed robust algorithm in realistic two-way relaying networks.     

Analysis and scheduling of practical network coding in OFDMA relay networks

Network coding has become a prominent approach to improve throughput of wireless networks. However, most of work in the literature concentrates mainly on 802.11-like random access networks. New technologies such as OFDMA (orthogonal frequency division multiple access), offer new opportunities for employing network coding. This paper considers how to apply the practical network coding scheme in OFDMA relay networks via cross-layer optimization. Specifically, we aim to explore the following questions: (1) When and how can wireless nodes select relay paths in the presence of network coding? (2) How can an OFDMA relay system assign network resource such as subcarrier and power for all the transmitting nodes? (3) What are the impacts of OFDMA system parameters on the network coding gain? To answer these questions, two efficient coding-aware relay strategies are presented to select forwarding paths with fixed and dynamic power allocation. In order to exploit the network capacity in slow frequency selective fading channels, we formulate optimization frameworks and propose channel-aware coding-aware resource allocation algorithms for an arbitrary traffic pattern. Our studies show that the network coding (i.e. XOR) gain depends on the nodes’ powers, traffic patterns etc. Especially, OFDMA relay network with dynamic power possesses both coding gain and power gain. Extensive simulations are performed to verify our analysis and demonstrate the throughput improvement of our proposals in the presence of XOR coding.     

基于协作通信技术的无线非再生中继组播网络中的功率最优分配

针对无线非再生中继网络中多播协作通信系统的节点功率最优分配问题,提出了一种新的基于多用户协作分集协议(multi-user diversity-cooperative protocol)的MDPTS(multi-user diversity-cooperative protocol transmission scheme)传输方案.在总功率一定时,利用分集复用增益的权衡对系统的性能进行了分析.在此基础上以系统误帧率最小为目标,提出了发射端和中继器间的功率优化分配方案,在信噪比足够大的条件下,以误帧率下界为目标函数,通过拉格朗日法求得系统的功率分配最优解.仿真结果表明,与采用传统传输方案的网络相比,采用MDPTS传输方案的网络具有更高的分集增益和复用增益上限,因此系统性能也更好.     

基于网络编码的无线数据流保护

网络编码是一种能显著提升网络传输性能的通信机制。而当前将网络编码应用于无线数据流保护以提高网络生存能力方面的研究还没达到如此完备的程度。本论文旨在建立基于网络编码的无线数据流保护模型,验证并实现建立进行网络编码的网络拓扑的算法。验证网络编码应用于无线数据流保护可以提高网络生存能力、减少网络资源消耗并具有远胜于传统保护的时效优势。在网络中部署和实施网络编码,必须建立适用于网络编码的传输节点拓扑并选择合适的编码模式。对于后者,许多学者出了有效的解决方法,而对于网络拓扑规划问题的研究则相对较少。鉴于此,本文论证了一种编码树拓扑结构算法,该算法与现有的编码模式一起,能够构成完整的网络编码无线数据流保护方案。通过理论论证可以证明应用网络编码方法可以在保护时节约网络资源。仿真实验表明,与传统的链路保护模式相比,使用网络编码的无线数据流保护方法具有更小的时延,也即具有传统保护方法没有的时间优势。     

基于网络编码的分布式无线光网络在线优化

最近, 一种集成骨干光传输网络、无源光网络和无线接入网的混合宽带无线光网络被提出。这种网络具有大带宽、低费用和无处不在的信息接入等特点。考虑在这种网络中的基于网络编码的多播会话的设计问题, 使得网络效用最大化, 而布网的费用最小化。这个问题被转换为一个混合的整数非线性规划问题, 精确求解极其困难。为了使得问题简化, 采用了一种两步优化方法进行求解, 交替地为多播会话选择光网络单元和网关。在每一次迭代过程中需要解决两个问题：光网络的网络编码设计问题和无线网络的用户和带宽分配问题。前者通过基于拉格朗日对偶分解的分布式方法实现; 后者通过广义Benders分解实现。通过仿真验证了所采用的方法的有效性。     

QoS and data relaying for wireless sensor networks

In this paper we study the effects of data relaying in wireless sensor networks (WSNets) under QoS constraints with two different strategies. In the first, data packets originating from the same source are sent to the base station possibly along several different paths, while in the second, exactly one path is used for this purpose. The two strategies correspond to splitting and not splitting relaying traffic, respectively. We model a sensor network architecture based on a three-tier hierarchy of nodes which generalizes to a two-tier WSNet with multiple sinks. Our results apply therefore to both types of networks. Based on the assumptions in our model, we describe several methods for computing relaying paths that are optimal with respect to energy consumption and satisfy QoS requirements expressed by the delay with which data are delivered to the base station(s). We then use our algorithms to perform an empirical analysis that quantifies the performance gains and losses of the splittable and unsplittable traffic allocation strategies for WSNets with delay-constrained traffic. Our experiments show that splitting traffic does not provide a significant advantage in energy consumption, but can afford strategies for relaying data with a lower delay penalty when using a model based on soft-delay constraints.     

异构无线网络多网资源优化管理研究

针对异构无线网络多网协同的特点,从分析多个无线网络共存的资源管理优化体制构建思想出发,建立了新的异构无线网络资源统一管理优化模型,实现了协同信息的控制和管理,同时保证了异构数据呼叫业务的服务质量,解决了多网间资源管理优化问题。首先,该模型在对呼叫服务请求做优化决策时,不仅考虑了本网络服务域的可用资源、服务请求的速率以及本系统的长期收益,同时也考虑了其他网络服务域的整体长期收益;其次,通过对所提出的基于异构无线网络多网资源优化管理模型的性能进行理论分析,得到其重要服务质量参数——新呼叫阻塞率;最后,通过仿真比较可以看出,通过该模型获得的优化决策策略能充分利用异构无线网络中各个网络域的资源,不仅提高了资源的利用率,而且在提高网络整体长期收益的同时,也保证了移动服务的服务质量。与资源完全共享算法相比,本方法降低了新呼叫阻塞率。理论分析和实验证明了异构无线网络资源域间资源优化管理方法的有效性、适应性。     

Optimization of relay selection and ergodic capacity in cognitive radio sensor networks with wireless energy harvesting

This paper addresses relay selection and resource allocation issues in cognitive radio sensor networks with wireless energy harvesting. We first consider a three-phase energy harvesting and information transmission protocol based on cooperative decode-and-forward relaying for a secondary system in coexistence with the primary system. In the first phase, the energy-constrained relay harvests energy through radio-frequency signals from the primary source. In the second phase, the destinations decode the primary signal. The relay uses the harvested energy to forward the primary signal and the secondary signal in the third phase. We derive the close-form upper bound of the ergodic capacity of the primary system and propose a relay selection algorithm. In particular, we calculate the critical region to ensure that the ergodic capacity of the primary system is equal or larger than that of the direct system. Finally, numerical results show that the proposed schemes achieve a satisfying performance.     

Energy-efficient dynamic resource allocation with opportunistic network coding in OFDMA relay networks

Network coding is significantly able to save system resources for wireless networks, and has been widely studied for the 802.11 wireless local area network and traditional cellular networks. The relay technology was introduced in 802.16j, 802.16m, and Long Term Evolution-Advanced (LTE-A) standards. Recently, the application of network coding to multi-hop wireless relay networks has been taken into consideration. Although the introduction of relay stations (RSs) may bring more energy consumption, it provides opportunities for network coding to save spectrum resources. Nevertheless, the benefits of network coding are diminished by high multiuser diversity based on orthogonal frequency division multiple access (OFDMA). For ensuring the superiority, network coding is performed opportunistically according to the channel state. Hence dynamic resource allocation (DRA) subject to rate constraints is combined with the idea of opportunistic network coding to minimize the total transmission power in a frame. A fixed set of discrete modulation levels in an OFDMA relay system is also considered. By taking the characteristic of a half-duplex decode-and-forward (DF) mode relay, a solution is proposed for the optimal problem of each subframe after separating power-aware relay selection. Simulation results show that DRA with opportunistic network coding can improve system energy efficiency. Further, it is more efficient for saving energy than DRA with static network coding compared solely to DRA.