三状态LMS信道能以3种可能的阴影状态描述窄带传播信道，可作为DVB-SH物理层仿真的基础，但因每一状态的传播参数固定不变和状态类别的问题，影响DVB-SH标准物理层参数的选择，因此提出改进的两状态LMS信道模型。该模型利用状态序列生成器实现两状态之间的转移，并结合传播参数生成器获得新状态的传播参数，从而使Loo生成器生成复时间序列。利用功率控制减少衰减、缩小信号的动态范围。仿真结果表明，该模型能有效地代表阴影环境，且功率控制体制在一定的终端速度下可获得最大的控制增益。%Three-state land mobile satellite (LMS) channel model that describes the narrowband propagation channel in three possible shadowing states can serve as a baseline for physical layer simulation of the digital video broadcasting-satellite services to handhelds (DVB-SH) standard. But the fixed propagation parameters for each state and the state classification impact the parameters selection of physical layer in the DVB-SH standard. For this, an improved two-state LMS channel model is proposed in this paper. The transitions between two states are modeled by employing state sequence generator (SSN). When the state is changed, new propagation parameters are obtained by propagation parameter generator (PPG) and then are used to generate the complex time series by Loo generator. Power control (PC) is used to reduce fading and gets much smaller dynamic rang in the controlled signal. Simulation results show that the proposed model is effective for representation of shadowing conditions and the PC scheme could achieve maximum control gain at some termination speed.
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