Hausdorff distance measure is one of the widely adopted feature-based image matching algorithms due to its simplicity and accuracy.However,it is considered that its robustness still needs to be improved.In this paper,various forms of original and improved Hausdorff distance(HD) and their limitations are studied.Focusing on robust Hausdorff distance(RHD),an improved RHD with an adaptive outlier point threshold selection method is proposed.Furthermore,another new form of the Hausdorff distance which possesses the merits of RHD and M-HD is prsented.Finally,a recursive algorithm is introduced to accelerate the image matching speed of Hausdorff algorithms.Extensive simulation and experiment results are presented to validate the feasibility of the proposed Hausdorff distance algorithm.
In traditional cognitive radio(CR) network,secondary users(SUs) are always assumed to obey the rule of"introducing no interference to the primary users(PUs) ".However,this assumption may be not realistic as the CR devices becoming more and more intelligent nowadays.In this paper,with the concept of lighthanded CR,which is proposed to deal with the above mentioned problem by enforcing"punishment"to illegal CR transmissions,the action decisions of primary users(PUs) are modeled as a partially observable Markov decision process(POMDP),and the optimal spectrum allocation scheme with the objective of maximizing their reward is proposed,which is defined by the utility function.Furthermore,a reduced scheme with much smaller state space has been proposed in this paper for lower computational complexity.Extensive simulation results show that the proposed schemes improve the reward significantly compared to the existing scheme.
Cooperative relaying has played an important role in rapid evolution of wireless communications.The cooperative performance strongly depends on the selected relays.In this paper,we concentrate on relay selection in amplify-and-forward(AF)cooperative communication system,and an optimal multi-relay selection scheme is put forward to minimize the average symbol error rate(SER)of the system.Firstly,for the minimum average SER,on the basis of the statistic channel information,we define a parameter named equivalent channel gain which describes the channel status of two phases in the cooperative process.Then,under the constraint of equal power allocation,an optimal relay selection scheme is proposed in ascending order of equivalent channel gain(ECG).The scheme implies that the suitable number of relay nodes should be selected under the different signal-to-noise ratio(SNR)ranges to minimize the average SER.Computer simulation results show that the average SER rate of the proposed scheme is lower than these of the other schemes.
3GPP标准组织在2004年底启动了其长期演进(LTE)技术的标准化工作。上行传输方案采用带循环前缀的单载波频分多址接入(SC-FDMA)技术。对LTE上行链路进行仿真,实现无中继节点的直接传输。引入中继节点,通过传统最大路径损耗最小(LMP,least maximum pathloss)方案选取最优中继参与协作传输。重点分析并指出了传统LMP算法的缺点和不足,在此基础上提出了一种改进的中继节点选择算法,并结合考虑了源节点和中继节点的功率分配。从系统误码率和用户消耗功率两个方面对各传输方案进行了仿真分析。仿真结果表明LTE上行链路引入中继节点实现协作传输可明显提高系统的误码率性能。协作传输还节约了功率的使用,提高了用户的待机时间和功率效率。相比传统中继选择方案,改进后的LMP算法无论是从误码率还是功率消耗都得到明显改善。
The intersubcarrier interference(ICI) degrades the performance of the pilot-aided channel estimation in fast time-varying orthogonal frequency division multiplexing(OFDM) systems.To solve the error propagation in joint channel estimation and data detection due to this ICI,a scheme of error propagation determined iterative estimation is proposed,where in the first iteration,Kalman filter based on signal to interference and noise is designed with ICI transformed to be part of the noise,and for the later iterations,a determined iterative estimation algorithm obtains an optimal output from all iterations using the iterative updating strategy.Simulation results present the significant improvement in the performance of the proposed scheme in high-mobility situation in comparison with the existing ones.
