首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
文章提出一种基于移动代理和光突发交换(OBS)的光链路信令建立方法和协议方案.将主动包的结构应用于移动代理,使信令消息和数据流概括到一个突发包头(BHP)中,以此来缩短一个光路的建立时间.该方案可以实现分布式处理链路,以减轻网络中一个节点的工作量和加强每个网络节点的并行运算能力.  相似文献   

2.
In emerging wireless networks, cooperative retransmission is employed to replace packet retransmission between a pair of sender and receiver with poor channel condition. A cooperative MAC protocol which utilizes such benefit is proposed in this paper to improve the network performance in mobile ad hoc networks. In the proposed protocol, relay nodes between sender and receiver are used if the sender cannot communicate with the receiver reliably. Furthermore, the receiver may also stop forwarding the received data frame if the frame is received by the next‐hop receiver on the route to the final destination node. Simulation results show that the proposed protocol outperforms previous works in terms of increased transmission reliability and reduced delay time. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

3.
Transmission-scheduling protocols can support contention-free link-level broadcast transmissions and delay sensitive traffic in mobile, multiple-hop packet radio networks. Use of transmission-scheduling protocols, however, can be very inefficient in mobile environments due to the difficulty in adapting transmission schedules. The paper defines a new adaptive and distributed protocol that permits a terminal to adapt transmission assignments to changes in topology using information it collects from its local neighborhood only. Because global coordination among all the terminals is not required and changes to transmission assignments are distributed to nearby terminals only, the protocol can adapt quickly to changes in the network connectivity. The two key parameters that affect the ability of the protocol to adapt to changes in connectivity are the rate of connectivity changes and the number of terminals near the connectivity changes. Using simulation, we determine the ranges for these parameters for which our adaptive protocol can maintain collision-free schedules with an acceptable level of overhead. The stability of the protocol is also characterized by showing that the protocol can quickly return to a collision-free transmission schedule after a period of very rapid changes in connectivity. Our channel-access protocol does not require a contention-based random-access phase to adapt the transmission schedules, and thus its ability to adapt quickly does not deteriorate with an increase in the traffic load.  相似文献   

4.
Reliable data distribution within multiple-hop spread-spectrum packet radio networks requires high performance from the network protocols. The high variability in quality among the links and the unique characteristics of frequency-hop spread-spectrum signaling impose special requirements for network protocols that are to be employed in frequency-hop packet radio networks. These features can be exploited in the forwarding protocols by allowing multiple packets to be included in each forwarding attempt. The use of multiple-packet transmissions exploits the capture property of frequency-hop signaling, and it reduces the overhead required for acknowledgments. A potential trade-off arises because the use of multiple-packet transmissions increases the throughput, but in some situations it can also increase the delay. Two new transmission protocols that employ multiple-packet transmissions are described, and their performance is evaluated.  相似文献   

5.
A predictive model‐based mobility tracking method, called dead reckoning, is developed for mobile ad hoc networks. It disseminates both location and movement models of mobile nodes in the network so that every node is able to predict or track the movement of every other node with a very low overhead. The basic technique is optimized to use ‘distance effect’, where distant nodes maintain less accurate tracking information to save overheads. The dead reckoning‐based location service mechanism is evaluated against three known location dissemination service protocols: simple, distance routing effect algorithm for mobility (DREAM) and geographic region summary service (GRSS). The evaluation is done with geographic routing as an application. It is observed that dead reckoning significantly outperforms the other protocols in terms of packet delivery fraction. It also maintains low‐control overhead. Its packet delivery performance is only marginally impacted by increasing speed or noise in the mobility model, that affects its predictive ability. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

6.
基于宽带多媒体卫星网络的MAC协议   总被引:1,自引:0,他引:1  
林建优  郭庆  刘功亮 《通信学报》2006,27(8):134-138
提出了一种基于MF-TDMA的宽带卫星MAC协议联合随机预约接入协议(CRRAP)。协议采用随机预约和捎带预约结合,按需分配和自由分配结合来实现的。仿真结果表明,相对于现有的方法,CRRAP减少了高信道负荷下的时延,提高了吞吐性能,并具有较高的信道利用率。  相似文献   

7.
低开销的MANET网络按需路由协议   总被引:1,自引:0,他引:1  
江国星  易明 《通信学报》2009,30(7):27-35
针对简单泛洪效率低的问题,提出了一个限制洪泛的高效的路由广播算法,通过Euclidean距离来限制路由发现过程中请求分组被转发的次数;研究了减少路由维护开销,并降低路由发现的频率的方法,提出了一个基于节点高度的路由修复与优化算法,该算法使用节点监听来对链路断裂的路由进行修复与优化.基于限制泛洪的高效的路由广播算法和路由修复优化算法,提出了一种新的低开销的MANET网络按需路由协议LOOR(low overhead on-demand routing).仿真结果表明,新协议增强了路由的顽健性,减少了路由跳数,降低了路由发现的频率,提高了数据分组递送率,并显著地降低了路由控制开销.  相似文献   

8.
Using directional antennas in wireless mobile ad hoc networks can greatly improve the transmission range as well as the spatial reuse. However, it will also cause some problems such as deafness problem and hidden terminal problem, which greatly impair the network performance. This paper first proposes a MAC protocol called Selectively Directional MAC (SDMAC) that can effectively address these problems and significantly improve the network throughput. Then two improvements on SDMAC are proposed. The first one is to improve the network throughput by scheduling the packets in the queue (a scheme called Q-SDMAC), thus the head-of-line (HOL) blocking problem can be addressed. The second one is to relax the assumption that each node knows the relative directions of its neighboring nodes and use caches to buffer those relative directions (a scheme named Q-SDMAC using cache). Extensive simulations show that: (1) SDMAC can achieve much better performance than the existing MAC protocols using directional antennas; (2) The network throughput can be significantly improved by scheduling the packets in the queue; (3) Using caches can still achieve high network throughput when nodes are moving; and (4) Network throughput decreases when directional antennas have side lobe gain.
Yuguang Fang (Corresponding author)Email:
  相似文献   

9.
In this paper, we present a literature review on the topological planning problem of third generation (3G) cellular networks based on the universal mobile telecommunications system (UMTS) standard. After describing the UMTS architecture, we introduce each subproblem and present major works that have been done. The cell, the access and the core network planning problems have all been considered as well as a more global approach (when more than one subproblems are considered simultaneously). Both planning and expansion algorithms are also included in this review. The goal of this paper is to present and classify the different research works that have been done so that it can be used as a starting point for future research on topological design of UMTS networks. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

10.
自组网路由协议综述   总被引:63,自引:0,他引:63  
史美林  英春 《通信学报》2001,22(11):93-103
自组网路由协议用于监控网络拓扑结构变化,交换路由信息,定位目的节点位置,产生、维护和选择路由,并根据选择的路由转发数据。本文综述了自组网路由协议研究方面的一些最新工作,描述了设计自组网路由协议所面临的问题,并着重对该研究开展以来所提出的各种主要协议进行了对比、分析和分类阐述,为进一步的研究提出了新的课题。  相似文献   

11.
To provide a multicasting service, several multicast protocols for mobile hosts (MHs) have been proposed. However, all of these protocols have faults, such as non‐optimal delivery routes and data loss when hosts move to another network, resulting in insecure multicast data transmissions. Thus, this paper presents a new reliable and efficient multicast routing protocol for mobile IP networks. The proposed protocol provides a reliable multicast transmission by compensating the data loss from the previous mobile agent when a MH moves to another network. In addition, an additional function allows for direct connection to the multicast tree according to the status of agents, thereby providing a more efficient and optimal multicast path. The performance of the proposed protocol is confirmed based on simulations under various conditions. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

12.
嵌套移动网络在扩大通信范围的同时会带来严重的路由优化问题。针对已有优化方案在可部署性和性能等方面的不足提出了一种新的嵌套移动网络路由优化方案(NMNRO),通过扩展邻居发现协议,在嵌套移动网络内通告相同的外地前缀,并更新接入路由器的邻居缓存和移动路由器的路由表,然后通过向对端发送绑定更新来实现路由优化。性能分析表明,该方案为嵌套移动网络提供了较为完整的路由优化方案,在降低优化开销的同时,具有较好的可部署性和兼容性。仿真实验结果表明该方案具有较低的切换时延和较高的有效吞吐量,且这些性能优势会随嵌套层数的增加而更加明显。  相似文献   

13.
The basic philosophy of personal communication services is to provide user‐to‐user, location independent communication services. The emerging group communication wireless applications, such as multipoint data dissemination and multiparty conferencing tools have made the design and development of efficient multicast techniques in mobile ad‐hoc networking environments a necessity and not just a desire. Multicast protocols in mobile ad‐hoc networks have been an area of active research for the past couple of years. This paper summarizes the activities and recent advances in this work‐in‐progress area by identifying the main issues and challenges that multicast protocols are facing in mobile ad‐hoc networking environments, and by surveying several existing multicasting protocols. This article presents a classification of the current multicast protocols, discusses the functionality of the individual existing protocols, and provides a qualitative comparison of their characteristics according to several distinct features and performance parameters. Furthermore, since many of the additional issues and constraints associated with the mobile ad‐hoc networks are due, to a large extent, to the attribute of user mobility, we also present an overview of research and development efforts in the area of group mobility modeling in mobile ad‐hoc networks. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

14.
15.
余斌霄  王新梅 《电子学报》2004,32(3):384-387
移动通信网络应用范围的不断扩展和新型业务的涌现需要有更多的特殊安全协议来保障其安全性.Yi Mu和Vijay Varadharajan提出了两种分别应用于同一服务区和不同服务区的端端保密通信协议 .本文首先分析了其不足之处,然后设计了同时适用于同一归属局和不同归属局移动用户之间进行保密通信的安全协议(分别称为域内和域间保密通信协议),最后,分析了上述协议的各项性能.与原有协议相比,本文所提出的协议不仅在安全性和其他性能上有较大改进,而且更具普遍性和统一性.  相似文献   

16.
In ad hoc wireless networks, the high mobility of hosts is usually a major reason for link failures. The general ‘shortest path’ based routing protocols may not lead to stable routes. In this paper, we propose a mobility assessment on‐demand (MAOD) routing protocol to select a stable route in order to enhance system throughput and performance. An error count parameter is used to judge whether a host is highly mobile. The proposed MAOD routing protocol is an on‐demand routing protocol similar to dynamic source routing (DSR). The difference between MAOD and DSR is in the path selection method. Because MAOD takes the mobility of hosts into consideration, it will select a more stable and reliable path than DSR. In comparison, DSR only considers whether this route is a shortest path or not. Finally, the system performance is analyzed by using the global mobile simulation (GloMoSim) simulator. We can observe that MAOD routing protocol outperforms DSR routing protocol especially in the high mobility environment. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

17.
提出了移动自组网中的基于分簇的一致性协议(Clustering-Based Consensus Protocol,CBCP),CBCP协议分为分簇检测层和决策层。分簇检测层在对移动自组网分簇的同时,不可靠故障检测器(Unreliable Failure Detectors,FD)向决策层提供网络的当前状态,分簇可以合并消息,减少网络中的消息数量,节省网络资源。性能分析表明,与现有的协议相比,该协议能够显著地节省时间代价和消息代价。  相似文献   

18.
We design a transport protocol that uses artificial neural networks (ANNs) to adapt the audio transmission rate to changing conditions in a mobile ad hoc network. The response variables of throughput, end-to-end delay, and jitter are examined. For each, statistically significant factors and interactions are identified and used in the ANN design. The efficacy of different ANN topologies are evaluated for their predictive accuracy. The Audio Rate Cognition (ARC) protocol incorporates the ANN topology that appears to be the most effective into the end-points of a (multi-hop) flow, using it to adapt its transmission rate. Compared to competing protocols for media streaming, ARC achieves a significant reduction in packet loss and increased goodput while satisfying the requirements of end-to-end delay and jitter. While the average throughput of ARC is less than that of TFRC, its average goodput is much higher. As a result, ARC transmits higher quality audio, minimizing root mean square and Itakura–Saito spectral distances, as well as several parametric distance measures. In particular, ARC minimizes linear predictive coding cepstral (sic) distance, which closely correlates to subjective audio measures.  相似文献   

19.
针对水下无线传感器网络(UWSN,underwater sensor networks)提出以发送端为中心以连续时间为计量单位的冲突状态模型——局部冲突状态图及其分布式构建算法,并在此基础上设计了基于启发式规则的水下传感器网络TDMA协议(CT-TDMA,continuous time based TDMA)。CT-TDMA利用UWSN中同一接收节点与不同发送节点之间链路时延的差异性,减少在目的端的接收帧之间的空闲时间,从而提高网络流量;基于启发式规则的分配算法,能有效缩短连续时间轴上的时刻分配所花费的时间。模拟实验证明:CT-TDMA与以ST-MAC为代表的按时隙分配的TDMA方案相比,网络流量提高了20%,数据分组的端到端时延降低了18%;与由全局知识所计算出的最优分配策略相比,网络流量达到了80%,端到端时延仅延长了12%。  相似文献   

20.
In this paper, we propose a Load‐Balancing and Coding‐Aware Multicast (LCM) protocol for mobile ad hoc networks. In LCM protocol, a new route metric named Expected Transmission Time with Coding and Load Balancing (ETTCL) is presented at first, aiming at effectively selecting the path not only that has the possible coding opportunity but also where overflow due to network overload can be prevented. Then, we describe the route discovery phase by constructing the node‐disjoint multicast tree on the basis of ETTCL and employ network coding to encode the data flows for route maintenance. The effectiveness of LCM protocol is simulated and analyzed by NS‐2, which shows that this protocol has good performance in reducing average end‐to‐end delay and control overhead and can improve packet delivery ratio compared with the existing protocol. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号