共查询到10条相似文献,搜索用时 156 毫秒
1.
In this paper, we investigate a worst-case robust power allocation scheme to improve energy efficiency (EE) for an amply-and-forward relaying uplink underlay OFDM cognitive radio system with imperfect channel situation information about the channel between primary user (PU) and secondary user (SU) and the channel between SU and corresponding relay. Specifically, a max–min problem is formulated to transform the original optimization problem into maximum EE on minimum throughout channel, and an epigraph problem is introduced to obtain analytical expressions of objective power allocation. Simulation results show that the proposed EE power allocation scheme is valid and effective in EE and robustness. 相似文献
2.
Abdul Sattar Saand Varun Jeoti Mohamad Naufal Mohamad Saad 《Wireless Personal Communications》2016,88(3):645-655
Relay beamforming is a key signal processing technique to mitigate interference in single and multiuser multiple input and multiple output (MIMO) wireless communication networks. In MIMO relay networks interference cancellation is an essential task of the study to get optimal network capacity. In this paper, the problem of interference resulted from leakage signal from desired signal for intended antenna, which causing interference to other antennas of the same user with multiple antennas is tackled. The criterion of signal to leakage plus noise ratio (SLNR) maximization is considered to design a vector by vector relay downlink precoding based on Fukunaga Koontz transform. This can control the interference among multiple antennas and maximize SLNR. However, matched filter beamforming is utilized at the relay receiving side that can increase output signal to noise ratio at the relay node. The channel state information of both the channel between source to relay and relay to destination is assumed at the relay node. The effectiveness of the proposed technique is studied and compared with conventional relay precoding techniques. Simulation is carried out in MATLAB environment using ideal channel conditions. This study demonstrates that, the proposed scheme for relay assisted MIMO networks can improve overall system performance in terms of ergodic capacity. 相似文献
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In Cognitive Radio (CR) networks, cooperative communication has been recently regarded as a key technology for improving the spectral utilization efficiency and ensuring the Quality of Service (QoS) for Primary Users (PUs). In this paper, we propose a distributed joint relay selection and power allocation scheme for cooperative secondary transmission, taking both Instantaneous Channel State Information (I-CSI) and residual energy into consideration, where secondary source and destination may have different available spectrum. Specifically, we formulate the cognitive relay network as a restless bandit system, where the channel and energy state transition is characterized by the finite-state Markov chain. The proposed policy has indexability property that dramatically reduces the compu-tation and implementation complexity. Analytical and simulation results demonstrate that our pro-posed scheme can efficiently enhance overall system reward, while guaranteeing a good tradeoff between achievable date rate and average network lifetime. 相似文献
5.
Cognitive radio technology enables Secondary Users (SUs) to access the frequency channels licensed to Primary Users. In this paper, we propose a novel dynamic multichannel access scheme for cognitive radio systems, which are based on a multichannel variation of a p-persistent Carrier Sensing Multiple Access scheme. To optimize the system-wide performance, the proposed scheme exploits different gains of frequency channels due to frequency-selective fading. With the proposed scheme, SUs share frequency channels in a fully distributed way, without any explicit control information exchange. To design the proposed scheme, we formulate the whole system as a “channel access game,” according to game-theoretic framework. In the channel access game, the utility function should reflect the system-wide performance. We derive closed-form performance measures by modelling the system as a continuous time Markov chain, and use them to construct a proper utility function. Then, each SU independently decides its own channel access strategy (i.e., the distribution of the random backoff time) which optimizes the utility function. The simulation results show that the proposed scheme promotes SUs to compete and cooperate with each other to a suitable level and, as a result, performs well in all range of SU population. 相似文献
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提出了一种基于目标的中继协作频谱感知方案,证明了SU到SR链路上的信道条件对系统性能有较大的影响;鉴于此,提出了一种优化的最佳中继协作频谱感知(optimized BRCSS)方案,通过联合考虑目标SU到SR链路上的信道条件和 SR 到 FC 链路上的信道条件选择最佳认知中继;最后,从更实际的应用场景考虑,为了节约系统开销,进一步提出了一种自适应的最佳中继协作频谱感知方案(A-BRCSS),即 SU 根据其信道条件,自适应地选择是否需要认知中继的协作传输。分析和仿真结果均表明,相比传统最佳中继协作频谱感知方案, Optimized BRCSS方案可以实现更高的感知性能;所提A-BRCSS方案可以实现几乎最佳的感知性能。 相似文献
7.
Behrad Mahboobi Ehsan Soleimani-Nasab Mehrdad Ardebilipour 《Wireless Personal Communications》2014,77(3):1629-1658
In this paper, a new robust problem is proposed for relay beamforming in relay system with stochastic perturbation on channels of multi user and relay network. The robust problem aims to minimize the transmission power of relay nodes while the imperfect channel information (CSI) injects stochastic channel uncertainties to the parameters of optimization problem. In the power minimization framework, the relays amplification weights and phases are optimized assuming the availability of Gaussian channel distribution. The power sum of all relays is minimized while the outage probability of the instantaneous capacity (or SINR) at each link is above the outage capacity (or SINR) for each user. The robust problem is a nonconvex SDP problem with Rank constraint. Due to the nonconvexity of the original problem, three suboptimal problems are proposed. Simulation and numerical results are presented to compare the performance of the three proposed solutions with the existing worst case robust method. 相似文献
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Robust Cognitive Beamforming With Bounded Channel Uncertainties 总被引:1,自引:0,他引:1
《Signal Processing, IEEE Transactions on》2009,57(12):4871-4881
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Meiling LI Ying LI Muhaidat SAMI Zengshou DONG Anhong WANG Jie LIANG Liping DING 《通信学报》2018,39(9):57-66
The non-orthogonal multiple access (NOMA) technology was studied in a downlink cognitive relay cooperation network.A cognitive multiuser relay cooperation based NOMA scheme was proposed (CM-RC-NOMA),in which,the outage performance of PU and SU were given under different cognitive relay cooperation schemes and the corresponding outage expressions were also derived.At the same time,the AF based relay cooperation method and the DF based relay cooperation method were compared.The simulation results show that the lower outage of PU can be achieved by AF method compared with DF method,when the channel condition of BS to PU is no more than that of SU to PU.It is also revealed that the optimal outage performance of PU can be achieved by the proposed best cognitive relay cooperation scheme in contrast to the traditional best cognitive relay cooperation scheme. 相似文献
10.
In this paper, a space division multiplexing (SDM) based joint adaptive beamforming downlink transmission scheme for infrastructured cognitive radio multi-input multi-output system is proposed. When spectrum holes exist traditional opportunistic spectrum access is employed. While there is no idle spectrum available, cognitive base station and cognitive user firstly evaluate spatial correlation between cognitive transmission and inter-system interference based on the preprocessed channel information. Incorporated with transmission gain, authorized frequency channel and eigenmode are jointly selected. Then on the premise that no interference is imposed on the primary, cognitive transmission is carried out adopting SDM. The proposed scheme exploits selection diversity of both authorized channel and cognitive eigenmode, thus achieves better spatio-frequency resource management and near-optimal cognitive throughput performance. 相似文献