资料3：WCDMA基本原理.ppt

* 基站：20W，手机又业务时去分。导频：20W*15% 手机功率+天线增益-损耗-接收机灵敏度（-120dbm越低越好）-用户数 * 基站发射P=路径衰减+总干扰+UE目标信噪比 * * * * * The Spreading Factor (SF) is the ratio: number of Chips over number of bits.(in the upper diagram, 8 chips are created for 1 bit, SF =8) The Processing Gain is the ratio: Bandwidth over Bit Rate. It is equivalent to the Spreading Factor (here its value is 8) In order to support very high bit rates, the use of variable Spreading Factors and Multicode connections is supported. * * * * * * * * * * * Soft HO: UE is in the overlapping area of two adjacent sectors belonging to two different Node-Bs. The communication between UE and UTRAN takes place concurrently via two different channels from each Node-B separately.This requires the use of two separate spreading codes. In the UE the two signals are received by means of Rake Processing. In the Node-B the two signals are routed to the RNC, which selects the better frame between the two candidates. Softer HO: UE is in the overlapping area of two adjacent sectors of the same Node-B. The communication between UE and UTRAN takes place concurrently via two different channels from each sector separately. This requires the use of two separate spreading codes. In the UE and in the Node-B the two signals are received by means of Rake Processing. Other types of HO: Inter-frequency hard HO (from one CDMA carrier to another) Inter-mode hard HO (from FDD to TDD) Inter-system hard HO (e.g between UTRAN FDD and GSM) * * * * * * * * * * TSTD: Time Switched Transmit Diversity STTD: Space Time block coding based Transmit antenna Diversity * FBI bits are used to support feedback technique between UE and UTRAN * * * * * * * * * 码分多址和扩频 扩频码和扰码 多径接收 软切换 功率控制 发射分集 无线资源管理 覆盖与容量 WCDMA 基本原理 * Node B MS2 MS1 为什么要功控？ WCDMA系统是自干扰系统，存在远近效应 远近效应：离基站很近的手机上行信号可能会屏蔽其他手机的信号 上图中，若MS2不采用功控，MS1信号很难被接受到 功率控制的目的 维持高质量通信,减少无线干扰,提高系统整体容量 所有到达基站的信号功率相同(上行),减少对其他基站的干扰(下行) *  WCDMA系统是自干扰系统，远近效应 功率控制目的是维持高质量通信，又不对其他用户产生干扰 开环功率控制 移动台根据测量的结果，调整发射功率 闭环