终端直通(device-to-device,D2D)通信通过共享蜂窝资源可以提升频谱效率,但会产生同频干扰,导致系统吞吐量和用户的服务质量降低。针对在部分频率复用(fractional frequency reuse,FFR)蜂窝网络中多小区间的D2D链路和蜂窝链路的同频干扰问题,提出了基于优先级的资源分配方案。该方案通过对频率资源赋予不同的优先级对小区间干扰进行协调,尽量避免小区间的D2D链路和蜂窝链路间、以及D2D链路间的干扰,从而提升系统性能。仿真结果表明,基于优先级的资源分配方案改善了小区边缘用户的服务质量,提高了系统容量。
To lower the cross-tier intercell interference(ICI) between macrocell and microcell,three user selection algorithms for the heterogeneous network were proposed in this paper, assuming full knowledge of channelstate information at the transmitter. Algorithm 1 chooses microcell users whose interference channel matrix is parallel to that of a known user and targets at increasing user SINR. Algorithm 2 takes effect of chordal distance-channel norm balance on the system into account and predetermines the available user set from which it can choose service users. With comprehensive considerations to effect of interference signal and useful signal on system, Algorithm 3 set a weighting function as the objective function of user selection. Simulation results demonstrated that all three proposed algorithms could achieve user diversity gain while lowering cross-tier interference.
随着移动多媒体业务的日益发展,蜂窝通信的频带日趋紧张,开辟新的频带资源是解决问题的关键技术之一。毫米波频段丰富的频率资源已经成为关注的焦点,它将是下一代蜂窝网络发展的希望所在。提出一种基于随机几何理论的毫米波蜂窝网络基站建模方法,用线段模型对城市中的建筑物进行建模,根据概率理论推导了毫米波蜂窝网络中建筑物的阻挡数量;分析了建筑物阻挡对覆盖产生的影响,研究了毫米波蜂窝网络的覆盖概率与信干比(Signal To Interference Ratio,SIR)之间的关系,最后通过系统仿真对前面的理论进行了验证,仿真结果与毫米波的传输理论一致。
位置图压缩是空间域水印嵌入算法中的关键问题。为此,以提高嵌入容量为目标,提出一种基于差值位置图调整的差分扩展优化算法。考虑可扩展差值的位置分布,通过修改短连续零组提高无损压缩率,从而扩大水印净荷嵌入空间,减少嵌入总量,提高峰值信噪比。仿真实验结果表明,该算法可通过选择最佳或优选调整强度增强差分扩展算法的水印嵌入性能,水印净荷嵌入容量可提升2.48倍~5.26倍,峰值信噪比可提升4.4 d B^8 d B。
