多信道无线Mesh网络的多播信道分配算法

无线Mesh网络可用信道和节点接口的缺乏限制了多播树链路的可用带宽,致使网络吞吐量下降。针对该问题,提出支持多播的多信道多接口信道分配算法——LAMCA。该算法能最小化无线Mesh网络的干扰程度,并最大化网络吞吐量。仿真结果表明,与层次信道分配算法LCA相比,该算法在吞吐量性能方面较优。     

无线传输中Raptor译码算法研究

研究了在加性高斯白噪声(AWGN)信道中采用最小频移键控(MSK)调制的Raptor码的译码算法设计问题。基于Raptor码和MSK调制的特点,提出了一种改进的Raptor码置信传播译码算法。仿真结果证明该译码算法具有更好的译码性能。     

Raptor码在卫星通信中抗干扰性能研究

为了提高卫星通信抗干扰性能,在对卫星通信的信道特性分析基础上,提出一种将Raptor码作为纠删码应用于卫星通信系统的方案.文中采用了LDPC码+LT码串行级联编码来实现一个码率为0.95的Raptor码,并对在载波噪声干扰信道中传输的Raptor码的译码算法进行了研究,通过系统仿真,搭建一种基于最优化度分布Raptor码的卫星通信系统模型,并对其抗干扰的性能进行分析及研究.     

无线多跳网络中吞吐量优化的多播路由算法研究

现有网络中提高多播吞吐量的算法通常是以提高链路速率为目的,但单纯地提高链路速率而忽略多播树的度也限制了多播吞吐量的提高。主要研究了多跳无线网络中多播吞吐量最优化问题,深入分析了无线多跳网络特点,并在综合考虑链路速率和多播树度对多播吞吐量影响的基础上,提出了应用于节点发射功率相同环境下的UUP_MTOA算法和应用于节点发射功率不同环境下的UNP_MTOA算法。通过仿真实验与同类近似最优化算法相比,UUP_MTOA算法和UNP_MTOA算法能够获得更高的吞吐量,更适应于多跳无线网络环境。     

支持多速率多播的Ad hoc网络资源分配算法

多播流是无线Ad hoc网络中的一种常见和有效的通信形式,尤其是对多媒体业务而言。提出了一种支持多速率多播传输的Ad hoc网络资源分配算法,它通过引入基于价格的流量分配方案来解决多速率多播传输问题,从而能够自适应地分配网络流量,并且最大化网络流的总效用。仿真结果表明,该算法不仅具有良好的收敛性,而且它的多速率多播传输特性使得不同信道条件的用户能获得最佳的网络性能,从而提高了网络吞吐量。     

无线网络中的链路自适应算法

针对无线链路固定传输模式吞吐量低,而基于单参数的链路自适应可能误判的问题,提出了一种可有效提高无线网络吞吐量的基于多信道参数信息融合的链路自适应算法。算法根据信道参数的特点,分别采用神经网络在线预测和模糊逻辑推理算法实现载干比(CIR)、包错误率(PER)和信噪比(SNR)对信道质量的局部评估,经过融合中心的合成运算和决策规则,获取信道质量的全局判决,以此进行最适应信道状态的物理层传输模式选择。仿真结果表明,当信道状态恶化时,平均吞吐量比固定传输模式和基于单参数的链路自适应算法提高了42.9%和28.4%。     

基于广义地址码的RFID防碰撞算法

提出了一种基于CDMA的广义地址码(GLS码)的防碰撞算法即CA-ALOHA算法,推导出了算法在信道传输中稳定的条件,并构造了相应的数学模型;这种新型算法选用新型扩频码即广义地址码(GLS),成功地屏蔽了信道中的多址干扰,将原有的ALOHA一维多址划分拓展为时频上的二维划分,用逻辑信道代替了实际信道,突破了以往信道划分的局限;仿真结果表明在同等条件下,采用GLS码的信道误码性能优于传统的Walsh码(扩频码),且CA-ALOHA算法的系统吞吐量明显优于ALOHA算法和二进制算法.     

MIMO系统中的H.264/SVC数据流抽取和重组算法

为了使H.264可分级视频编码(SVC)生成的数据流分割为多个子数据流,便于在多输入多输出(MIMO)无线网络的不同子信道上传输以提高视频传输速率,提出了一个SVC数据流抽取和重组算法.在发送端,该算法利用SVC数据流的分层结构,将其中的基本层和增强层抽取为多个子数据流,并保持基本层子数据流能够独立解码.在接收端,该算法将接收到的子数据流重组成可解码的SVC数据流.实验证明该算法能充分利用MIMO系统提供的高带宽,并具有较低的冗余度和较好的灵活性.     

一种基于最小生成树的无线多跳网络信道分配算法

在无线多跳网络环境下,提出了一种信道分配算法,该算法可优先考虑最小生成树上的可用信道,为每个节点分配信道资源,然后考虑利用生成树外其他可用链路为节点提供信道资源,以提高吞吐量。该算法通过考虑每个用户的通信需求,可充分利用空闲信道资源。仿真结果显示,相比于不考虑最小生成树外链路时,本算法可有效地提高网络整体的吞吐量。     

一种联合多信道分配决策的认知Mesh系统数据传输优化算法

在认知Mesh系统进行数据传输的过程中,为了提高数据包投递成功率及网络的吞吐量,减少网络延迟时间,提出一种联合多信道分配决策的认知Mesh系统数据传输优化算法(JCWN)。针对信道的干扰问题,建立了认知Mesh系统的干扰无向图,分析节点链路的网络干扰电平。在节点的路由请求阶段通过提出基于信道干扰电平的路由指标函数,并通过权重阈值来为节点链路分配干扰较小的信道。在路由选择上,联合多路由算法计算每条路由路径的信道干扰程度,为了保障节点传输数据的成功率而选择干扰程度更小的路由。实验仿真结果表明,在数据包投递成功率上,该算法相比POC算法以及基于RL的算法提高了20%以上,在提高网络吞吐量,减少延迟时间上也表现出了更好地效果。     

Spectrum efficient cross-layer adaptation of Raptor codes for video multicasting over mobile broadband networks

This paper explores the use of rateless application layer Forward Error Correction (AL-FEC) based on Raptor codes in a spectrally efficient way for real-time video multicasting over mobile broadband networks. The link between channel errors at the PHY, MAC and application layers and the required Raptor code parameters for quasi-error free video transmission is investigated. Low Raptor code rates are shown to place high demands on the limited bandwidth of a wireless channel. The selection of Modulation and Coding Scheme (MCS) is extended to take into account the channel resources required to accommodate the additional Raptor overheads. A cross-layer optimization approach and a novel metric are proposed to select the Raptor code parameters and the MCS mode jointly to maximize wireless transmission efficiency. Simulation results show that 166% more bandwidth is required by a non-Raptor enabled multicast WiMAX system, assuming a Mobile Station (MS) speed of 10 km/h, in comparison to the optimized Raptor AL-FEC multicast WiMAX system. Results show that more bandwidth is required at lower MS speeds. Furthermore, the optimized Raptor AL-FEC system is shown to eliminate packet loss, to enhance the link budget by up to 6 dB, which quadruples multicast coverage in LoS locations, and to increase the total goodput by 67%, in comparison to a non-Raptor enabled multicast WiMAX system.     

Fast and low-complexity encoding of Raptor codes based on operation lists for known source block lengths

Raptor codes can provide good error correction capability and efficient encoding and decoding rate. Its fountain code property is effective in avoiding packet retransmission for both unicast and multicast service delivery. Hence, there are many mobile, vehicular and broadband applications adopting it such as mobile multimedia broadcasting, multimedia communications for high-speed rails and broadband IPTV systems. In this paper, we present an efficient systematic Raptor codes encoder based on operation lists for known source block lengths. For a Raptor codes application that can frequently use one or several fixed source block lengths (i.e., the number of source symbols in a source block), we could produce the corresponding operation lists in advance and use them to generate the encoding symbols more efficiently. We first introduce the basic architecture of the proposed Raptor encoder, and then describe the details about how to generate operation lists and Raptor intermediate symbols. The simulation results show that our encoder is at least two times faster than the conventional Raptor codes encoder which is adopted by 3GPP and DVB-H. Besides, the reduction on CPU utilization for a real Raptor-based streaming server is described, which is from 11.59 % to 53.41 %, depending on the employed source block length and symbol size.     

A weight-aware channel assignment algorithm for mobile multicast in wireless mesh networks

Wireless mesh networks (WMNs) are one of key technologies for next generation wireless networks. In this paper, we propose a heuristic channel assignment algorithm with weight awareness to support mobile multicast in WMNs. To enhance network throughput, our algorithm is based on the path forwarding weight to perform channel assignment. In addition to non-overlapping channels, partially-overlapping channels are also used in channel assignment. To fully exploit all available channels in channel assignment, we devise a new channel selection metric to consider the channel separation and the distance between nodes. In mobile multicast, the multicast tree structure cannot be fixed due to receiver (multicast member) mobility. The change of the multicast tree structure will result in channel re-assignment. The proposed algorithm is based on a critical-event driven manner to reduce the times of channel re-assignment as much as possible. Finally, we perform simulation experiments to show the effectiveness of the proposed channel assignment algorithm.     

Recommender system for mobile users

As predicted, trillions of devices and billions of services will be integrated into Internet of Things (IoT), where most value added applications rely on wireless physical links. In this paper, we develop a recommender system to overcome the challenges of large-scale mobile IoT. The proposed recommender system socially matches wireless devices to communicate and share their contents based on similarities, distance, velocity, wireless channel quality and remaining energy. The physical layer connections are realized by device-to-device spectrum sharing techniques, and we accordingly designed a cooperative multicast service case to make full use of the wireless broadcasting nature. A “green communication” orientated algorithm is proposed to allocate power resources, adaptively adjust data rate and recommend partners as mobile relays. Simulation results show that the proposed system can efficiently utilize the wireless resource of mobile IoT and appropriately recommend partners to assist more users into IoT services.     

Subcarrier and power allocation for OFDMA-based multicast cellular networks using a coalitional game

The subcarrier and power allocation problem for orthogonal frequency-division multiple access (OFDMA)-based multicast cellular networks is investigated in this paper. Due to the intrinsic heterogeneity of the channel gains experienced by different multicast users, the conventional multicast schemes are highly conservative and spectrally inefficient. To address this issue, a novel multicast formulation is proposed where multiuser diversity inherent in OFDMA can be adaptively exploited by clustering users within a multicast group into smaller subgroups based on their channel gains. Subcarriers and power are then dynamically allocated to these subgroups to maximize the total multicast rate of the system. Coalitional game theory is adopted to model the group formation in which users can autonomously form coalitions with other users to compete for network resources. A low-complexity algorithm is proposed for the multicast coalitional game to reach multicoalitional equilibrium in which a sub-optimal performance can be obtained. Simulation results demonstrate that the proposed scheme outperforms the conventional unicast and multicast schemes while achieving a sub-optimal performance comparable to the exhaustive search scheme.     

基于邻居信息交换的组播快速切换算法

切换延迟和丢包率是决定移动组播算法是否能够满足实时性组播应用要求的重要指标.提出了一种基于邻居信息交换的组播快速切换算法M-FMIPv6/NIE.在二层触发器事件发生之前,通过邻居接入路由器之间定时的信息交换,可以提前进行新转交地址的配置和请求加入组播树等操作.性能分析和仿真结果表明,M-FMIPv6/NIE的组播服务中断时间小于现有的组播快速切换算法,并且在缓存数量和丢包率等方面也具有较佳的性能.     

基于调度集合的多播单播数据联合调度算法

首先定义和分析了IEEE802.16e无线城域网中的一个新问题,即如何在保证移动终端服务质量的前提下,通过合理地调度终端的单播业务和多播业务来降低终端能耗.针对该问题,提出一种基于调度集合的联合调度算法(scheduling set based integrated scheduling,简称SSBIS).SSBIS算法将所有移动终端划分到多播调度集合或单播调度集合中,并利用多播数据的传输特点,在多播数据传输的相邻时隙内发送多播调度集合中所有终端的单播数据,而对于单播调度集合中的终端,则通过凸优化方法求得使终端休眠时间最长的单播业务调度方案,以达到降低终端能耗的目的.仿真实验显示,SSBIS算法在满足移动终端的最小数据速率要求的同时,可以明显地降低终端能耗.     

Personal video delivery with rapid Raptor code decoder

Due to the growing popularity of Internet of People (IoP) and its impacts on human activity, it has quickly become an important research field and hot subject. Since one purpose of IoP is to connect people to people, personal live video delivery that has been popular recently can also be regarded as an important application of IoP. For improving the video quality of video communication services, Raptor code has been adopted in various broadband communication systems. In this paper, we propose a systematic Raptor code decoder based on the group parameters for a group of encoding symbols. For a Raptor code application that can frequently use one or several fixed source block lengths (i.e., the number of source symbols in a source block), we could produce the corresponding group parameters in advance and use them to decode the received encoding symbols more efficiently. For personal live video delivery scenario based on the IPTV delivery, the simulation results show that our decoder is faster than the conventional Raptor code decoder which is adopted by the DVB and 3GPP specifications.     

IP多播在IEEE1394等时通道中的传输

利用1394等时通道传输IP多播信息,关键是解决IP多播地址和1394等时通道的映射问题。MCAP(Multicast Chan-nel Allocation Protocol)采用集中控制管理的方法实现,通道利用率比较高,但算法复杂,实现难度大。为此提出一种基于哈希算法的多播通道分配方法(Hash Multicast Channel Allocation Protocol,HMCAP),利用哈希函数实现IP多播地址和1394等时通道的映射。HMCAP是一种自动确定性的方法,减小了通道分配时间,算法简单易于实现。通过对HMCAP和MCAP两种方式下的碰撞概率进行分析比较,随着加入通讯的多播组数量增加,HMCAP和MCAP之间的差距在减小,HMCAP可以作为一种多播通道分配实现方式。     

基于OP通道的交互协作系统中的全排序多播

全排序(Total Ordering)是组播的重要特性之一。结合基于OP通道的交互协作系统中命令信息的特点，提出了一种动态的全排序多播(Total Ordering Multieast)算法，该算法通过建立最小延迟多播树来保证信息的全排序多播，并通过动态调整多播树来改善算法性能。