共查询到20条相似文献,搜索用时 15 毫秒
1.
Hui Zhao Dan-yang Wang Chao-qing Tang Ya-ping Liu Gao-feng Pan Ting-ting Li Yun-fei Chen 《浙江大学学报:C卷英文版》2016,17(9):929-937
We investigate the secrecy outage performance of maximal ratio combining (MRC) in cognitive radio networks over Rayleigh fading channels. In a single-input multiple-output wiretap system, we consider a secondary user (SU-TX) that transmits confidential messages to another secondary user (SU-RX) equipped with M (M ≥ 1) antennas where the MRC technique is adopted to improve its received signal-to-noise ratio. Meanwhile, an eavesdropper equipped with N (N ≥ 1) antennas adopts the MRC scheme to overhear the information between SU-TX and SU-RX. SU-TX adopts the underlay strategy to guarantee the service quality of the primary user without spectrum sensing. We derive the closed-form expressions for an exact and asymptotic secrecy outage probability. 相似文献
2.
The outage probability (OP) performance of transmit antenna selection (TAS) in decode-and-forward (DF) relaying device-to-device (D2D) networks over N-Nakagami fading channels is investigated in this paper. Exact closed-form expressions for the OP of two TAS schemes are derived. The power allocation problem is formulated to determine how the transmit power should be divided between the broadcast and relay phases to optimize performance. The OP performance under different conditions is evaluated through numerical simulation to verify the analysis. These results show that the optimal TAS scheme provides better OP performance than the suboptimal scheme, but the performance gap is reduced as the number of antennas at the source is increased. The fading coefficient, number of cascaded components, relative geometrical gain, power allocation parameter, and number of transmit antennas are shown to have a significant influence on the OP performance. 相似文献
3.
4.
This paper investigates the secrecy outage performance of underlay cognitive radio networks, in which a source in a secondary system transmits its confidential information to a legitimate destination in the presence of an eavesdropper. Specifically, the main (the source-to-destination) and eavesdropping (the sourceto- eavesdropper) channels are assumed to be correlated. Moreover, it is also assumed that the main channel and the channel from the source to the primary user’s receiver are correlated. Tight closed-form analytical expression for secrecy outage probability and the closed-form analytical expression for the probability of non-zero secrecy capacity are derived and validated by simulation results when the interference temperature limit is comparably large. 相似文献
5.
提出了基于多天线选择分集接收的多用户分集认知无线电系统模型。该系统模型由于在认知接收端采用了多天线选择分集接收,相比传统多用户分集认知无线电系统采用的单天线接收,能够进一步提高认知用户系统信道遍历容量。推导并给出了认知接收端信噪比的概率密度函数与累积分布函数,分析了多天线数目与认知用户数对系统信道遍历容量的影响,同时给出了不考虑认知用户发送功率约束条件下的认知用户系统信道遍历容量的解析表达式。 相似文献
6.
The outage probability is a key performance measure for real-time traffic in wireless networks, often considered as even more critical than the blocking probability. The blocking and outage probabilities do not have closed-form expressions as they depend in a too complex way on the traffic characteristics (call duration, bit rate requirement), the radio conditions (fading, shadowing, noise, interference) and the considered admission and outage policies. We derive upper bounds for the blocking and outage probabilities for general traffic characteristics and radio conditions under the mild assumption that the admission and outage policies satisfy a certain monotonicity property. These conservative estimates may depend on call characteristics like the bit rate requirement and the trajectory of the mobile. The results are applied to the uplink and the downlink of CDMA networks. 相似文献
7.
认知无线电技术可以动态使用授权频段进行传输,因此如何有效利用这些频谱接入机会成为一个研究重点。本文研究在认知无线电网络中使用智能天线,使认知用户在时域上获得频谱接入能力外,还具有增强的空间复用能力。当前频段出现活跃授权用户时,认知用户可以优化天线波束模式,避免干扰授权用户同时保持在该频段上的传输。本文对波束调整的策略进行分析,并给出了使用这些策略时认知用户可以获得的空间共享概率。理论分析和仿真结果均表明,使用智能天线可以使认知用户获得更多的频谱接入机会,频段的利用率大幅提高。 相似文献
8.
This paper analyzes the performance of clustered decode-and-forward multi-hop relaying (CDFMR) wireless Rayleigh fading networks, and sheds light on their design principles for energy and spectral efficiency. The focus is on a general performance analysis (over all SNR range) of heterogeneous wireless networks with possibly different numbers of relays in clusters of various separations. For clustered multi-hop relaying systems, hop-by-hop routing is known as an efficient decentralized routing algorithm which selects the best relay node in each hop using local channel state information. In this article, we combine hop-by-hop routing and cooperative diversity in CDFMR systems, and we derive (i) a closed-form expression for the probability distribution of the end-to-end SNR at the destination node; (ii) the system symbol error rate (SER) performance for a wide class of modulation schemes; and (iii) exact analytical expressions for the system ergodic capacity, the outage probability and the achievable probability of the SNR (power) gain. We also provide simple analytical asymptotic expressions for SER and the outage probability in high SNR regime. Numerical results are provided to validate the correctness of the presented analyses. 相似文献
9.
In this paper, we consider a dual hop wireless communication system with a non-regenerative relay and study its performance over the α–μ fading channel. Specifically, we derive closed-form expressions for the moment generating function (MGF), the cumulative distribution function (CDF), and the probability density function (PDF) of the harmonic mean of the end-to-end signal-to-noise ratio (SNR) assuming the α–μ fading model. We also derive closed-form expressions for the end-to-end capacity and outage capacity of the system herein. The obtained expressions can be reduced to study the performance of dual hop communication systems over other fading channel models by using the proper values for the α and μ parameters, such as Rayleigh, Nakagami-m, and Weibull fading models. Numerical results are provided for the obtained expressions and conclusion remarks are drawn. 相似文献
10.
随着通信业务需求的不断增长,频谱资源的有限性使得卫星通信网络和地面网络都面临着严重的频谱危机。认知无线电技术的出现,使得卫星网络与地面网络共用频率资源以提升网络效用成为可能。文中对认知接入分配给地面网络作为主用户的同一频谱资源的认知卫星网络的功率控制和信道分配问题进行了研究。根据卫星网络和地面网络的特性构建了合理的系统模型,并利用中断概率门限表征了信道估计误差对系统容量的影响。为了保护主基站的通信性能,在考虑信道估计误差、信道资源约束、认知卫星用户最大发射功率和微波基站干扰约束的条件下,根据议价博弈理论设计了优化函数。其次,根据凸优化理论推导了最优发射功率和信道分配的闭式解,并在此基础上设计了一种对偶迭代算法来求解该优化问题。最后,根据卫星网络的特性设置了合理的网络参数,并根据参数利用Matlab仿真平台对提出的算法进行了仿真实验。仿真结果表明:所提方法在不同到达速率的条件下均具备良好的收敛性;信道估计误差会降低网络的总容量;所提方法在波束数多于15个时,相比比例公平性算法容量提升超过50 bps/Hz,相比最大容量法公平性能提升超过一倍,因此,相较于这两种方法,该方法能在系统容量和用户间公平性之间获得较好的折中。 相似文献
11.
12.
针对无线资源的匮乏,结合多用户分集与多用户调度技术,提出一种基于多用户调度的闭环多输入多输出跨层算法.该算法是采用跨层理论的方法,以包错误率为服务目标,利用调度技术,自适应调制,自动重传技术与MIMO技术的有机结合,提高系统的中断性能.推导了系统平均包错误率,平均传输次数与中断概率的闭合表达式,分析了天线配置,移动用户数以及重传次数对系统性能的影响;仿真结果表明,该系统的中断概率明显减小,中断性能提高. 相似文献
13.
With the continuously increasing demand for broadband applications and services, underlay cognitive satellite-terrestrial networks, enabling to accommodate better wireless services within the scarce spectrum, have attracted tremendous attentions recently. In this network, satellite communications are allowed to operate in the frequency bands allocated to terrestrial networks under the interference constraints imposed by terrestrial network, which may lead to a performance degradation of the satellite network. To guarantee the performance of the primary terrestrial network as well as the secondary satellite network, we introduce the cooperation into cognitive satellite-terrestrial networks and investigate the performance of the new framework, i.e., cognitive satellite-terrestrial cooperative network (CSTCN). Specifically, by restricting the transmit power of satellite communications with interference power constraints imposed by terrestrial communications, we firstly obtain the received signal-to-interference-plus-noise ratio (SINR) of the considered network. Moreover, by employing the moment generating function (MGF) approach, closed-form expressions for symbol error rate (SER) and outage probability (OP) of the considered cognitive network are derived. The analytical results obtained in this paper can provide theoretical support for optimizing the performance of satellite-terrestrial networks. 相似文献
14.
15.
研究了固定增益放大转发的双跳多输入和多输出(M IMO)无线传感器网络。为了降低发射和接收链路的复杂度,所有节点均利用了基于信噪比最大化的天线选择策略。提出了系统中断概率和平均误比特率的封闭表达式。理论分析了系统的分集阶数,并比较了计算机仿真和理论导出的结果,验证了固定增益放大转发在无线传感器网络中是一种可选的低复杂度的转发策略。 相似文献
16.
17.
ICRN功率分配与中继选择联合优化 总被引:1,自引:0,他引:1
针对工业认知无线电网络中出现的无线干扰和冲突严重,特别是工业现场的金属环境和移动特性造成多径与阴影衰落,从而使得传输可靠性难以保证的问题,引入感知信道概率及信道可用度概念,提出一种联合优化中继选择与功率分配的算法。该算法给出3种认知中继选择方案,分别是信道增益最大准则、最近准则及调和平均准则,并在源节点和所选中继节点之间进行最优功率分配,以最小化网络中断概率。仿真结果表明,与平均功率分配算法相比,所提算法能更好地降低系统中断概率,提高传输可靠性。 相似文献
18.
This paper discusses transmission performance and power allocation strategies in an underlay cognitive radio (CR) network that contains relay and massive multi-input multi-output (MIMO). The downlink transmission performance of a relay-aided massive MIMO network without CR is derived. By using the power distribution criteria, the kth user’s asymptotic signal to interference and noise ratio (SINR) is independent of fast fading. When the ratio between the base station (BS) antennas and the relay antennas becomes large enough, the transmission performance of the whole system is independent of BS-to-relay channel parameters and relates only to the relay-to-users stage. Then cognitive transmission performances of primary users (PUs) and secondary users (SUs) in an underlay CR network with massive MIMO are derived under perfect and imperfect channel state information (CSI), including the end-to-end SINR and achievable sum rate. When the numbers of primary base station (PBS) antennas, secondary base station (SBS) antennas, and relay antennas become infinite, the asymptotic SINR of the kth PU and SU is independent of fast fading. The interference between the primary network and secondary network can be canceled asymptotically. Transmission performance does not include the interference temperature. The secondary network can use its peak power to transmit signals without causing any interference to the primary network. Interestingly, when the antenna ratio becomes large enough, the asymptotic sum rate equals half of the rate of a single-hop single-antenna K-user system without fast fading. Next, the PUs’ utility function is defined. The optimal relay power is derived to maximize the utility function. The numerical results verify our analysis. The relationships between the transmission rate and the antenna number, relay power, and antenna ratio are simulated. We show that the massive MIMO with linear pre-coding can mitigate asymptotically the interference in a multi-user underlay CR network. The primary and secondary networks can operate independently. 相似文献
19.
In this paper, we develop and analyze an energy efficient ARQ (automatic repeat request) initialized transmit diversity protocol
for cooperative communications. Medium access control (MAC) layer packet retransmission limit (similar to aShortRetryLimit
or aLongRetryLimit [802.11–1997]) has been used as an actuator for transmit cooperative diversity initialization. We take
the channel state information (CSI) as a function of retransmission tries and the number of retransmission tries is modeled
as a random variable. Relays close to the source node are chosen for the transmit cooperation. Closed form expressions are
obtained for symbol error rate (SER), outage capacity and outage probability for the proposed scheme in shadowed fading channels.
This cooperative scheme achieves lower signal-to-noise ratio (SNR), stumpy outage probability, higher bandwidth, and transmit
energy efficiencies for desired average symbol error rate (ASER) than the preceding ARQ based cooperative protocols. Finally,
the results of computer simulations are included to demonstrate the efficacy of the proposed scheme and to verify the accuracy
of the analytical expressions.
Supported by the National Natral Science Foundation of China (Grant No. 60602058), the National High Technology Research and
Development Program of China (Grant No. 2006AA01Z257) 相似文献
20.
提出了一种基于资源认知信道的接入算法,可用于认知无线电环境下的无线资源管理。对资源认知信道上传输的每个分组——数据域部分采用了基于联合检测的扩频码,而控制域部分则分别采用了5种不同的信道接入协议。分析并仿真了认知用户在资源认知信道上的成功接入概率以及吞吐量性能。 相似文献