CMT uses the stream control transmission protocol＇s（SCTPs） multihoming feature to distribute data across multiple end-to-end paths in a multihomed SCTP association. As the disparity of multipaths, it is facing a great challenge to solve the disorder of the received data packets. To lighten the reordering degree and then to improve the throughput performance, we need to estimate the real-time paths＇ bandwidth and round trip time（RTT） as exactly as possible. In this paper, we use the extended vector（ext-vec） Kalman filter（KF） to predict the available bandwidth and RTT of each path simultaneously. Based on this, we propose a predictive path selection algorithm for CMT in SCTP. To simulate and compare the algorithms＇ performance, two kinds of scenarios, bandwidth sensitive scenario and time and bandwidth sensitive scenario, are built and NS-2 is used. The simulation results show that the path selection algorithm can lessen the data packets disordering by correctly predicting each path＇s bandwidth and RTT in real time. Comparing the existing algorithms, the algorithm can converge more quickly and can improve the system total throughput in a certain extent in bandwidth sensitive scenario. To time and bandwidth sensitive scenario, it can greatly improve the convergence speed and total throughput.
To overcome the inter-carrier interference （ICI） of orthogonal frequency division multiplexing （OFDM） systems subject to unknown carrier frequency offset （CFO） and multipath, this paper develops a blind adaptive interference suppression scheme based on independent component analysis （ICA）. Taking into account statistical independence of subcarriers＇ signals of OFDM, the signal recovery mechanism is investigated to achieve the goal of blind equalization. The received OFDM signals can be considered as the mixed observation signals. The effect of CFO and multipath corresponds to the mixing matrix in the problem of blind source separation （BSS） framework. In this paper, the ICA- based OFDM system model is built, and the proposed ICA-based detector is exploited to extract source signals from the observation of a received mixture based on the assumption of statistical independence between the sources. The blind separation technique can increase spectral efficiency and provide robustness performance against erroneous parameter estimation problem. Theoretical analysis and simulation results show that compared with the conventional pilot-based scheme, the improved performance of OFDM systems is obtained by the proposed ICA-based detection technique.
针对载波频偏引起的子载波间干扰问题,提出一种基于独立分量分析的OFDM(orthogonal frequency division multiplexing)载波频率同步算法。本算法直接实现载波频率同步,可以避免基于导频机制的频偏估计和由频偏估计误差带来的频谱效率降低与性能损失。首先建立含频偏OFDM独立分量分析模型,然后从最大似然原则得到分离的代价函数,结合自然梯度优化得到OFDM源信号实现载波频率同步。理论分析表明,提出的算法不仅具有基于最大似然的频偏补偿性能而且提高了系统的输出信噪比。最后,仿真分析证明了算法的有效性。
