共查询到20条相似文献,搜索用时 109 毫秒
1.
针对CPM系统的信道容量研究结果进行了综述,并推导计算了Rayleigh衰落信道下CPM的容量分析方法与计算结果。首先回顾了CPM系统的基本概念及其有限状态马尔可夫模型,并对AWGN信道下CPM的可达信息速率计算方法进行了讨论;然后将其推广到Rayleigh衰落信道,推导出在该信道下计算CPM容量的算法。考虑了接收端已知信道状态信息及未知信道状态信息2种情况。在导出容量计算的算法后,通过Monte Carlo仿真给出了在AWGN及Rayleigh衰落信道下几种典型CPM方案的容量曲线。 相似文献
2.
多址接入中继信道是含有多个接入节点、1个中继节点和1个目的接收节点的无线多用户信道,同时考虑接入节点之间能够接收彼此含噪的广义反馈信息,此种模型存在于接入节点之间协作通信能力较差的多跳无线网络和无线传感器网络。论文给出了带有此种广义反馈的离散无记忆多址接入中继信道的可达速率区域,并将这一结果推广到高斯信道。提出一个新的编码方案,主要基于速率划分和译码前传策略,并通过采用分组Markov叠加编码建立各接入源节点之间以及源节点和中继节点之间的协作通信,在可达性证明中还采用规则编码和反向译码策略。结果表明,在离散无记忆信道环境下可达速率区域相比较以往结果更具一般性,在高斯信道环境下可达速率区域被扩展。 相似文献
3.
4.
本文以IEEE802.22无线广域网标准为基础,研究了认知无线电环境下MIMO-OFDM系统中分布式无线资源管理问题.基于博弈理论分析,文中首先证明了在全局容量最大化的博弈情况下分布式多用户信道功率分配是Supermodular博弈,并给出了相应的分布式多用户信道功率分配算法,并进一步给出了在认知无线电环境下MIMO-OFDM多用户子载波功率分配问题的解决方法.仿真结果表明,本文算法通过有限的重复博弈,可以有效的提高网络容量。 相似文献
5.
6.
无线信道在实际中难以测试,但信道仿真可以解决这一问题。文中给出了一种灵活且适应性强的无线移动信道模型,并给出了该模型中的衰落信道模型及算法,运用该算法对衰落信道进行仿真,给出衰落信号的仿真结果以及输入信号经衰落信道处理后的结果。 相似文献
7.
8.
9.
10.
移动通信中无线信道特性的研究 总被引:2,自引:0,他引:2
从等效低通信道的时变冲激响应的相关函数和功率密度谱函数出发,研究了一些描述广义平稳非相关散射(WSSUS)的无线信道特性的统计参数,并对无线移动衰落信道的特性进行分类。分析了3种常见的小尺度多径衰落信道的统计模型,给出了在平坦衰落信道中系统传输比特误码率的一般分析方法。最后,利用这些模型和方法,给出了一些常见数字调制信号的传输误码率的数值结果。结果表明:衰落对无线移动通信系统传输性能的影响是很大的,在实际中应设法消除它。 相似文献
11.
通信无线资源调度系统设计 总被引:1,自引:1,他引:0
为了达到对空间无线电资源的有效管理,提高频谱资源的利用率,在认知用户可以准确获取空间频谱利用情况和无线资源特征的前提下,提出了短时和长期学习的无线资源体统调度模型。根据认知用户对空间某点的无线信号进行特征提取,得到频谱的利用情况和各个信道的特征参数,如调制方式、带宽、中心频率和功率,根据用户的发射机特性,利用层次分析法结合测量的信道参数,给出可用信道的特征参数,以供认知用户参考。长期对某一固定点进行测量记录后根据历史数据进行复合,作为认知用户机特征参数跳变的根据,以给出合理的建议。 相似文献
12.
Achievable rates in cognitive radio channels 总被引:4,自引:0,他引:4
Devroye N. Mitran P. Tarokh V. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2006,52(5):1813-1827
Cognitive radio promises a low-cost, highly flexible alternative to the classic single-frequency band, single-protocol wireless device. By sensing and adapting to its environment, such a device is able to fill voids in the wireless spectrum and can dramatically increase spectral efficiency. In this paper, the cognitive radio channel is defined as a two-sender, two-receiver interference channel in which sender 2 obtains the encoded message sender 1 plans to transmit. We consider two cases: in the genie-aided cognitive radio channel, sender 2 is noncausally presented the data to be transmitted by sender 1 while in the causal cognitive radio channel, the data is obtained causally. The cognitive radio at sender 2 may then choose to transmit simultaneously over the same channel, as opposed to waiting for an idle channel as is traditional for a cognitive radio. Our main result is the development of an achievable region which combines Gel'fand-Pinkser coding with an achievable region construction for the interference channel. In the additive Gaussian noise case, this resembles dirty-paper coding, a technique used in the computation of the capacity of the Gaussian multiple-input multiple-output (MIMO) broadcast channel. Numerical evaluation of the region in the Gaussian noise case is performed, and compared to an inner bound, the interference channel, and an outer bound, a modified Gaussian MIMO broadcast channel. Results are also extended to the case in which the message is causally obtained. 相似文献
13.
Abdallah K. Farraj 《Wireless Personal Communications》2013,71(2):975-985
This article investigates how the performance of the primary user is affected by the presence of a spectrum-sharing cognitive user. The performance under both cooperative and non-cooperative cognitive schemes is considered. Primary user’s transmission rate, average channel capacity, and average bit error rate are considered as the performance measures. Moreover, the performance is compared with that of a wireless user in a Rayleigh channel, and the gain in performance is found. In addition, a process on how the primary user can accommodate a cognitive user without sacrificing its own performance is explained. Results of this work indicate that the primary user experiences a very close performance in both non-cooperative cognitive and Rayleigh environments. However, the primary user enjoys a pronounced better performance in the cooperative cognitive mode. 相似文献
14.
A three-phase transmission scheme for the linear four-node half-duplex wireless relay network is proposed. In each of its two cooperative phases, the setting is equivalent to the broadcast channel with cognitive receiver, whose capacity region is determined. Based on that result, the three-phase scheme is shown to be capacity achieving. Its performance is compared with two suboptimal schemes. 相似文献
15.
《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(3):1197-1206
16.
17.
V. G. Gavrilenko A. Yu. El’tsov A. A. Kiryushin S. V. Lobanov A. N. Sadkov 《Journal of Communications Technology and Electronics》2009,54(4):446-455
The general architecture of a simulator of wireless sensor networks and a detailed model of a wireless communications channel that involves various models of the radio-wave propagation are presented. It is demonstrated that the model of the radio-wave propagation significantly affects the connectivity of the wireless sensor network. It is shown that the radio-wave-propagation model based on the parabolic-equation method yields more accurate results for the packet reception rate as a function of distance and the width of the transition region. The results are in good agreement with experimental data, thus indicating that the effective and reliable simulation of a wireless communications channel can be implemented in practice. 相似文献
18.
?Cognitive radio? has emerged as a new design paradigm for next-generation wireless networks that aims to increase utilization of the scarce radio spectrum (both licensed and unlicensed). Learning and adaptation are two significant features of a cognitive radio transceiver. Intelligent algorithms are used to learn the surrounding environment, and the knowledge thus obtained is utilized by the transceiver to choose the frequency band (i.e., channel) of transmission as well as transmission parameters to achieve the best performance. In this article we first provide an overview of the different components to achieve adaptability in a cognitive radio transceiver and discuss the related approaches. A survey of the cognitive radio techniques used in the different wireless systems is then presented. To this end, a dynamic opportunistic channel selection scheme based on the cognitive radio concept is presented for an IEEE 802.11-based wireless mesh network. 相似文献
19.
Sadek A.K. Ray Liu K.J. Ephremides A. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(10):3677-3696
In this paper, a novel cognitive multiple-access strategy in the presence of a cooperating relay is proposed. Exploiting an important phenomenon in wireless networks, source burstiness, the cognitive relay utilizes the periods of silence of the terminals to enable cooperation. Therefore, no extra channel resources are allocated for cooperation and the system encounters no bandwidth losses. Two protocols are developed to implement the proposed multiple-access strategy. The maximum stable throughput region and the delay performance of the proposed protocols are characterized. The results reveal that the proposed protocols provide significant performance gains over conventional relaying strategies such as selection and incremental relaying, specially at high spectral efficiency regimes. The rationale is that the lossless bandwidth property of the proposed protocols results in a graceful degradation in the maximum stable throughput with increasing the required rate of communication. On the other hand, conventional relaying strategies suffer from catastrophic performance degradation because of their inherent bandwidth inefficiency that results from allocating specific channel resources for cooperation at the relay. The analysis reveals that the throughput region of the proposed strategy is a subset of its maximum stable throughput region, which is different from random access, where both regions are conjectured to be identical. 相似文献
20.
为了研究信道编码技术对无线光通信副载波系统差错性能的影响,基于无线光通信链路噪声特性,建立了大气信道等效数学模型。采用低密度奇偶校验(LDPC)码作为信道编码方式引入无线光通信,在不同光强闪烁指数下对基于副载波相移键控调制无线光通信系统进行了差错性能仿真,比较分析了LDPC编码前后副载波调制系统的误比特率,并对二相相移键控及四相相移键控两种系统进行了对比。结果表明,副载波二相相移键控调制系统的差错性能优于四相相移键控系统,同时LDPC码在弱湍流信道具有优越的纠错能力,可以获得比未编码系统较高的编码增益,在无线光通信领域具有一定的应用价值。 相似文献