A Control Mechanism of Stream Media Based on 3G Network

In this paper, we use RTP/RTCP over unreliable UDP to realize the transportation of real time streaming. Meanwhile, according to the transmission feedback and network parameters, we analyze and calculate the network delay, packet loss and RTT (round trip time) to determine the network state. Finally, we propose a streaming media transmission ??control scheme which could sense the network state and quickly adjust the rate of the sending side. It takes congestion, packet loss rate into comprehensive consideration and improves the overall performance of 3G network stream media.

FBMC系统中的SR-NYQ原型滤波器设计

FBMC (filter bank multicarrier)作为新一代移动通信中的候选方案,相对于OFDM (orthog onal frequency division multiplexing)具有旁瓣衰减大、无需严格正交同步等多个方面的优势,在实现子载成形的原型滤波器上起到了重要作用.目前,常用FBMC原型滤波器包括PHYDYAS滤波器和IOTA滤波器,但在两者的相应设计中,可控参数较少而灵活性欠佳.因此,本文提出了一种约束优化方法来直接设计FBMC滤波器.在该方法中,将滤波器的阻带误差能量作为优化目标,目的在于减小FBMC波形的旁瓣泄漏.同时,通过近似方法在频域对NYQ (Nyquist)条件进行约束,实现对符号间干扰的控制.该NYQ约束包含线性矩阵不等式和针对截止频点的线性不等式,避免了原始约束中由卷积计算引起的非凸问题.通过半定规划算法可对约束优化问题进行求解,所得线性相位FIR (finite impulse response)滤波器能够在适当放宽NYQ条件的同时有效改善阻带衰减特性,从而提升FBMC波形的频率选择特性.误码率仿真结果表明优化所得滤波器相对于PHYDYAS滤波器和IOTA滤波器具有一定优势.此外,在本文设计方法下,可采用长度更短的滤波器,其BER(bit error rate)与采用PHYDYAS滤波器时的BER结果近似可比,而其乘法复杂度比PHYDYAS滤波器低.