由于高速多径环境下频率色散现象严重破坏正交频分复用(OFDM)系统子载波正交性,为解决高速多径环境下的频率色散问题,正交时频空调制技术技术(OTFS)应运而生;而多输入多输出技术(MIMO)具有可以有效提升信道容量和系统可靠性的特点,文章采用了 MIMO技术与OTFS技术结合的方法,推导了 MIMO-OTFS系统中最大比合并信号检测算法(MRC)理论并加以仿真;针对MIMO-OTFS系统中MRC信号检测算法复杂度过高的情况,提出了一种低复杂度信号检测算法;该算法的基本思想是利用最大比合并方法对时延一多普勒网格中传输符号的接收多径分量进行提取和相干合并,以提高合并信号的信噪比,同时利用Cholesky矩阵分解理论,对信道增益矩阵进行求逆运算的优化,降低了算法复杂度,为MIMO-OTFS系统的实际应用做出贡献.
Opportunistic routing achieves high throughput in the face of lossy wireless links.The current opportunistic routing protocol,MORE,is the first opportunistic routing work to adopt network coding,but in the selection of candidate forward node set,it only considers the quality of the link between nodes,which leads to premature dead for some nodes because of energy depletion,affecting the integrity of wireless sensor networks.Aiming at this outstanding issue,an improved routing protocol based on MORE is proposed,which balances energy consumption of wireless sensor nodes.According to transmission mechanism of opportunistic routing,considering the expected transmission count (ETX) and residual energy (RE),a new routing metric expected life time (ELT) and a selection strategy of candidate forward node set based on it is proposed.Finally,simulations are performed by NS2.The results show that in the basis of taking the residual energy into account,the improved MORE protocol not only ensures the reliability of data transmission,but also balances the energy consumption of nodes,improving survival of nodes and prolonging the network life cycle.
With the extensive application of the wireless sensor network,the security problem has been more and more prominent,so it needs more attention.In wireless sensor networks,the wormhole attack is one of attacks against the WSN routing protocol and is a coordinated attack by two nodes usually.The malicious nodes establish communication through a secret high quality and wide band link which called "Tunnel".Attack nodes catch the routing packet in network and then transmit it to colluding node through "Tunnel".Thus it can destroy the network topology and the network routing.According to the features of wormhole attacks,using the existing scheme of detection with connectivity information and adding locating device,a comprehensive algorithm for detecting and locating wormhole attacks in WSN has been proposed to improve detection rate in the low density.The results of simulation with NS2-based platform show that the proposed algorithm is superior to other ones with less detection rate and position errors.
On the basis of gray clustering analysis model,this paper evaluates the scheme of radar netting quantitatively,and uses this method to solve the problem of selecting an optimum scheme for radar netting,aiming at the correlative index evaluation system,performs the validation through a practical example,the result verifies that this method is flexible in application of selecting the optimum scheme and show more in detail.
