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一种用于无线自组织网络的并发传输MAC协议 总被引:1,自引:0,他引:1
本文提出一种工作在单信道、单发射器和单发射功率模式下的并发传输MAC协议.该协议在控制报文(RTS/CTS)和数据报文(DADA/ACK)之间插入附加控制时隙,以便相邻节点有机会交换自己的控制报文.为了保证并发传输的可靠性,协议在控制报文中包含了冲突避免信息,邻居节点根据这些信息判断自己的传输能否在不影响已有传输的情况下并发进行.模拟结果显示,与IEEE 802.11相比,CTMAC协议在网络中存在并发可能时,使系统吞吐量得到很大提高. 相似文献
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The cognitive radio (CR) technology is an efficient approach to share the spectrum. But how to access the idle channels effectively is a challenging problem. To solve this problem, we propose a MAC protocol for cluster-based CR ad hoc networks, with the aim of making cluster structure more robust to the primary users’ channel re-occupancy activities, so that the CR users can use the idle spectrum more efficiently. Under this framework, a cluster formation algorithm based on available channels, geographical position and experienced statistics is proposed to maximize the network throughput and maintain the cluster topology stability. The schemes for new CR user joining a cluster and cluster maintenance are also designed. An experience database is proposed to store the experienced statistics which are obtained from spectrum occupancy history. Such a database can be used to support the acts of nodes, such as neighbor discovery and cluster forming. Simulation results reveal that our proposed framework not only outperforms conventional CR MAC protocols in terms of throughput and packet delay, but also generates a smaller number of clusters and has more stable cluster structure with less reclustering time. 相似文献
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Mahassin Mohamed Sharifah Kamilah Syed Yusof NikNoordini NikAbdMalik Suleiman Zubair 《电子科技学刊:英文版》2016,14(2):145-151
The absence of network infrastructure and opportunistic spectrum access in cognitive radio ad hoc networks (CRAHNs) results in connectivity and stability problems. Clustering is known as an effective technique to overcome this problem. Clustering improves network performance by implementing a logical network backbone. Therefore, how to efficiently construct this backbone among CRAHNs is of interest. In this paper, we propose a new clustering algorithm for CRAHNs. Moreover, we model a novel cluster head selection function based on the channel heterogeneity in term of transmission ranges. To the best of our knowledge, this is the first attempt to model the channel heterogeneity into the clustering formation in cognitive radio networks. Simulation results show that the performance of clustering is significantly improved by the channel heterogeneity considerations. 相似文献
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Gyanendra Prasad Joshi Seung Yeob Nam Sung Won Kim 《Wireless Personal Communications》2014,74(2):803-821
A new problem of spectrum scarcity has emerged due to the incredible technological advances in wireless communication. The spectrum scarcity issue is a bottleneck for the next generation of wireless communications. Therefore, efficient spectrum utilization has attracted considerable attention. This paper proposes a novel method of utilizing the white spaces in the licensed spectrum while ensuring the incumbent licensees’ rights. The protocol predicts the incumbents’ arrival using a historical prediction method and protects the incumbent users from the interference of opportunistic spectrum users. Distributed sensing is used to determine the network wide spectrum opportunity. The channel access delay in the proposed protocol is evaluated by simulation and mathematical analysis. The protocol has the advantages of a decentralized system, flexibility and low computing complexity. The simulations show that the protocol outperforms the existing opportunistic spectrum-sharing, media-access-control protocols in terms of the goodput and delay. 相似文献
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考虑两个无线Ad Hoc网络(主网络与次级网络)的并存模型:主网络与次级网络节点依照不同密度的空间泊松点过程并存于同一区域并共享同一频谱,两种网络节点均采用时隙ALOHA协议,按照各自的传输概率进行通信。本文首先根据随机几何理论对来自本网络的自干扰与来自其它网络的互干扰进行建模,然后分别推导了在AWGN信道和Rayleigh衰落信道下,单网络及并存式网络时节点平均吞吐量的闭合表达式,最后采用优化准则得到最佳传输概率,使节点平均吞吐量达到目标性能上的最优。仿真结果表明:经推导的闭合表达式与仿真值相近;在比例公平准则下,传输控制策略能达到主网络与次级网络之间公平性与高效性的折中。 相似文献
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Larry N. Singh Galigekere R. Dattatreya 《International Journal of Wireless Information Networks》2007,14(1):17-31
Estimation of channel and data characteristics by the receiver is important in adaptive wireless transmission protocols and
in cognitive radio. This paper formulates the estimation problem with the help of an illustrative example from the IEEE 802.11a
OFDM standard. The problem reduces to the estimation of the common component variance and mixing probabilities in a finite
Gaussian mixture, with known values for component means. Using the known component means, μ1, ... , μ
M
, a set of non-linear transformations, and of the data (mixture random variable X) are used to develop convergent and computationally efficient estimators for both the noise variance and the vector of symbol
probabilities. The estimation equations can be implemented recursively or with a batch processing algorithm. Asymptotic variances
of the estimates and the Cramer–Rao minimum variance bounds are derived. The estimates converge to true unknowns even when
the sequences of noise and data symbols are dependent sequences. The OFDM example is simulated with parameters corresponding
to the highest acceptable error rate. For a time-varying channel model chosen from the literature, it is shown that our estimator
receives considerably more than adequate amount of data during an average time interval of unchanging channel characteristics.
Analytical results, numerical results and related issues are discussed. 相似文献
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Jipeng Zhou Liangwen Liu Guofang Liao Jianzhu Lu 《Wireless Personal Communications》2013,71(4):3115-3130
Using location information to help routing is often proposed as a means to achieve scalability in large mobile ad hoc networks (MANETs). One of the biggest challenge in geographic routing protocols is the design of efficient distributed location services that can locate the positions of mobile nodes. The accurate positioning of mobile nodes in MANETs is important to location service scheme since they are related to efficiency of routing protocols. We propose a grid-based predictive Location Service (GPLS) scheme and a hole-tolerant grid-based predictive Location Service (GPLS-H) scheme. In proposed location service scheme GPLS and GPLS-H, the network is partitioned into grids and grids are divided into groups by using a HASH function, which guarantees the uniform distribution of location servers of a node in the network. The main contribution of this paper is that the proposed location service scheme GPLS and GPLS-H provide accurate location query capability by means of location prediction of mobile nodes and GPLS-H can tolerate the “holes” in grid networks. The simulation results show that the location service scheme GPLS and GPLS-H have better performance than CRLS and SLURP in query success ratio, query delay and location availability. 相似文献
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基于Ad Hoc网络路由协议的控制开销研究 总被引:2,自引:1,他引:1
对Ad Hoc网络路由协议的控制开销进行了系统而深入的研究。在分析了路由开销机制的基础上.对几种典型的开销优化方法和策略进行了研究和总结,并通过仿真研究了MAC协议对路由开销的影响,以及节点密度、业务流量和移动性等网络环境因素对路由开销的影响。 相似文献
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在感知无线电自私ad hoc网络环境下提出一种低代销的诚实能效路由(Lowest Cost Path,LCP),将路由的开销结合对主用户的干扰和节点剩余能量,利用格罗夫斯-克拉克-威科瑞(Vickrey-Clark-Groves,VCG)定价机制给LCP上每个中继节点以一定报酬促使节点之间的合作,并证明VCG机制下节点真实的反映自身的类型是一个占优策略。仿真结果表明,该路由算法有效实现了感知无线电自私ad hoc网络的诚实能效路由,与现有最短路径路由协议比较,该协议具有更好的性能。 相似文献
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Abstract—Cognitive radio technology has drawn much attention since it is a promising candidate to efficiently utilize the scarce radio resources. However, cognitive radio introduces new challenges in the protocol stacks in wireless networks. This paper proposes a routing protocol for Cognitive Radio Ad Hoc Networks (CRAHNs), called Transmission Power Control aware AODV (TPC-AODV). TPC-AODV is based on Ad hoc On Demand Distance Vector (AODV) routing protocol. The main objectives of TPC-AODV are to avoid interruption of primary users’ communication and to support basic Quality of Service for secondary users. TPC-AODV takes inputs from both secondary users’ application requirements and the channel condition after spectrum sensing. These inputs enable secondary users’ communication with specific transmission power on the selected channel. Our simulation results show that TPC-AODV improves network performance in terms of throughput and delay compared to AODV in CRAHNs. 相似文献
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Channel handoff is a crucial function for Cognitive radio ad hoc networks (CRAHNs). The ab-sence of centralized infrastructures and the limited power make the handoff design more challenging. A learning-based interference-aware handoff scheme is proposed for distributed CRAHNs. We model the channel handoff pro-cess as a Partially observable Markov decision process (POMDP) and adopt a Q-learning algorithm to find an optimal handoff strategy in a long term. The proposed algorithm obtains an efficient transmission performance by considering the interferences among SUs and PUs. To achieve PU awareness, the handoff scheme predicts the PU activities by using the historical channel usage statistics. In addition, we also propose a refined channel selection rule to compromise between learning speed and cumulative trans-mission reward. The simulation results show that the pro-posed handoff scheme can adapt to the PU activities and achieves a better performance in terms of high throughput and low collisions. And the learning process keeps a consid-erable balance between convergence time and cumulative reward. 相似文献
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Xiaorong Zhu Juanjuan Shi Longxiang Yang Hongbo Zhu 《Wireless Personal Communications》2013,71(3):2097-2109
Dynamic spectrum access (DSA) is an important design aspect for the cognitive radio networks (CRNs). Most of the existing DSA schemes are to govern the secondary user traffic in a licensed spectrum without considering the transmissions also in the unlicensed bands. In this paper, we propose two DSA schemes (i.e., without and with buffer) for cognitive radios access in both licensed and unlicensed bands in a distributed CRN. A Markov chain analysis for each of the proposed DSA schemes is presented and forced termination probability, blocking probability and traffic throughput are derived. In addition, we discuss a number of errors in the Markov model and analysis of the blocking and forced termination probabilities in a CRN, given in Al-Mahdi et al. (IEEE Commun Lett 13(9):676–678, 2009). This paper shows the corresponding correct derivations and results, and simulation results are given to support our analyses. 相似文献
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Ad Hoc网络中的多信道多接口技术研究 总被引:1,自引:0,他引:1
无线自组织网络是一种不依赖基础设施的无线网络,网络中节点均是由移动主机构成.文中通过修改NS2中的移动节点结构引入多信道多接口,可以使得路由协议能够灵活调用多信道功能,并根据AODVPlus协议的实现机制,提出一种对应的信道分配策略.通过仿真模拟与单信道进行比较分析得出,多信道多接口在传输率与传输时延方面比单信道都有所改善,但有效的多信道分配策略显得尤为重要. 相似文献
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Currently, wireless communications are changing along the lines of three main thrusts. The first is the introduction of secondary
spectrum licensing (SSL). Regulations on the usage of licensed spectra are being loosened, encouraging unused primary spectrum
to be licensed, often in an opportunistic manner, to secondary devices. The second is the introduction of cognitive radios. These wireless devices are able to sense and adapt in a “smart” manner to their wireless environment, making them prime
candidates to becoming secondary users in SSL initiatives. Finally, as we approach the communication limits of point-to-point
channels, and as wireless devices become cheap and ubiquitous, the focus is shifting from single to multiple communication
links, or networks. In this paper, we provide an overview of the recently established theoretical limits, in the form of sum-rates, or throughput,
of two main types of networks: ad hoc networks, in which the devices are homogeneous, and cognitive networks, in which a mixture
of primary and secondary (or cognitive) devices are present. We summarize and provide intuition on how the throughput of a
network scales with its number of nodes n, as n → ∞, under different network and node capability assumptions.
相似文献
Mai VuEmail: |
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Explicit Multicasting for Mobile Ad Hoc Networks 总被引:1,自引:0,他引:1
In this paper we propose an explicit multicast routing protocol for mobile ad hoc networks (MANETs). Explicit multicasting differs from common approaches by listing destination addresses in data packet headers. Using the explicit destination information, the multicast routing protocol can avoid the overhead of employing its own route construction and maintenance mechanisms by taking advantage of unicast routing table. Our protocol – termed Differential Destination Multicast (DDM) – is an explicit multicast routing protocol specifically designed for MANET environment. Unlike other MANET multicasting protocols, instead of distributing membership control throughout the network, DDM concentrates this authority at the data sources (i.e. senders) thereby giving sources knowledge of group membership. In addition, differentially-encoded, variable-length destination headers are inserted in data packets which are used in combination with unicast routing tables to forward multicast packets towards multicast receivers. Instead of requiring that multicast forwarding state to be stored in all participating nodes, this approach also provides the option of stateless multicasting. Each node independently has the choice of caching forwarding state or having its upstream neighbor to insert this state into self-routed data packets, or some combination thereof. The protocol is best suited for use with small multicast groups operating in dynamic MANET environment. 相似文献