共查询到20条相似文献,搜索用时 78 毫秒
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第三代移动通信系统TD-SCDMA中,移动终端设备(简称UE)接入系统的过程与第二代GSM系统类似,但由于系统对同步性能的特殊要求,接入过程中专门增加了对上行同步的处理。移动终端从开机起,到发出第一个随机接入请求止,可分为下行同步捕获、系统信息读取、建立上行同步、随机 相似文献
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TD-SCDMA系统是时间同步系统,终端开机后首先要通过搜索下行导频时隙实现与NodeB的下行帧同步。文中首先分析了特征窗搜索算法的原理,然后详细阐述了在基于ZSP500的TD-SCDMA硬件平台下,具体的实现算法和详细设计方案。测试结果表明,该实现方案具有较理想的估计准确度和稳定性,这说明该方案适合应用于TD-SCDMA通信系统中。 相似文献
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随机接入是TD-SCDMA系统性能的一个关键性过程.UE在进行业务前,需要发起随机接入过程以建立上下行同步.在上行同步过程中,多个UE可能在同一子帧发送相同SYNC-UL(上行同步码),由此产生的碰撞会导致上行同步的失败,直接影响UE的接入成功率和系统无线资源的利用.在N频点小区中,由于所有UE都须从主载波上发起上行同步过程,多UE同步接入时发生SYNC-UL碰撞的概率会大大增加.本文在分析了N频点小区随机接入上行同步过程碰撞概率的基础上,提出了N频点小区中利用Node B辅助的上行同步的优化算法,该算法简单,容易实现,能有效地提高UE上行同步的成功率. 相似文献
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TD-SCDMA系统下行链路同步技术 总被引:1,自引:0,他引:1
首先对TD-SCDMA系统同步技术进行了系统的阐述,随后介绍了无线接口同步中下行链路初搜的几种同步方法的原理,同时给出了各自的改进方案,最后通过其算法复杂度、仿真准确性等方面的性能比较来分析各下行链路同步方法的优缺点。 相似文献
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TD-SCDMA系统是时间同步系统,终端开机之后通过搜索SYNC_DL码同基站建立下行同步,通过比较几种同步建立算法,可以发现,利用其帧结构特性的搜索法与传统方法相比具有运算简单、快速、终端功耗小等优点,是值得采用的。 相似文献
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TD-SCDMA下行小区快速搜索的关键问题研究 总被引:1,自引:0,他引:1
针对TD-SCDMA下行小区搜索中下行导频时隙(DwPTS)位置搜索、下行同步码(SYNC-DL)位置的确定以及控制复帧同步三个步骤中的关键问题提出了解决方法.第一个步骤中根据TD-SCDMA子帧结构特点采用功率模板法确定下行导频时隙的位置;第二个步骤中采用定义模板法确定下行同步码的位置;第三个步骤中通过快速的TD-SCDMA信道估计方法检测下行导频信道来控制复帧同步.以上方法简化了计算的复杂性,可实现快速高效的网络测量,满足TD-SCDMA网络规划及优化的需求,这些在仿真结果和现场测试中都得到了验证. 相似文献
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Third Generation Partnership Project (3GPP) specification TR 25.950 proposed high-speed downlink packet access for the Universal Mobile Telecommunication System (UMTS). In this mechanism, an active set of cells is defined for every user equipment (UE) communication session. The cell with the best wireless link quality (called the serving cell) in the active set is selected for communication with the UE. When the wireless link quality of the old serving cell degrades below some threshold, a new serving cell in the active set is selected to continue the communication session. Our previous work proposed a high-speed downlink packet access (HSDPA) overflow control scheme with four frame synchronization algorithms to switch the serving cell, and formally proved the correctness of the scheme. We propose an analytic model to investigate the performance of these frame synchronization algorithms, and show how the user movement patterns affect the control message delivery costs of these algorithms. 相似文献
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Module count-based overflow-control scheme for UMTS high-speed downlink packet access 总被引:1,自引:0,他引:1
In the universal mobile telecommunication system, the user equipment (UE) communicates with all cells in the active set through the air interface. Multiple radio links between the UE and the cells may reduce the transmission speed due to interference. In high-speed downlink packet access (HSDPA), only one serving cell is selected in the active set for high-speed downlink transmission. When the radio link quality between the serving cell and the UE degrades below some threshold, the best cell (in terms of the radio characteristics) in the active set is selected as the new serving cell and the UE switches from the old serving cell to the new serving cell. This action is referred to as frame synchronization. The frame-synchronization information may be delivered through more than one wireless transmission, which introduces long delay for the frame-synchronization process. In this paper, we propose an overflow-control scheme with module count for HSDPA, which guarantees that the frame-synchronization information is delivered through one wireless transmission and that when the UE switches wireless link to the new serving cell, no packet frames are lost. 相似文献
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文章讨论TDD模式下小区间的同步技术,阐述小区同步过程中的各个阶段及其所完成的功能。在小区间的同步进入稳定状态阶段后,借助处于切换状态的用户终端来检测小区间是否同步。最后介绍同步过程中所用的信令和数据包格式。 相似文献
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This paper proposes overflow control schemes to support high-speed downlink packet access (HSDPA) mechanism in the universal mobile telecommunication system (UMTS). To access the UMTS services, a user equipment (UE) communicates with all cells (base stations) in an active set. However, multiple links between the UE and the cells in the active set may reduce the transmission speed due to interference. Third-Generation Partnership Project specification TR 25.950 proposes HSDPA. In this mechanism, the UE only selects one cell (referred to as the serving cell) in the active set for high-speed downlink transmission. In HSDPA, the radio network controller sends the packet frames to the cells in the active set. For the serving cell, the packet frames are forwarded to the UE. On the other hand, every nonserving cell in the active set queues the packet frames in a buffer. If the link quality between the serving cell and the UE degrades below some threshold, the UE selects the best cell in the active set as the new serving cell. Since the nonserving cells do not send packet frames to the UE, their buffers may overflow. In this paper, we propose schemes to address the buffer overflow issue. Our schemes guarantee that when the buffer of a nonserving cell is full, the previously received packet frames in the buffer can be safely dropped, and after the UE has switched wireless link to the new serving cell, no packet frames are lost. 相似文献
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Wenqin Wang 《Geoscience and Remote Sensing, IEEE Transactions on》2007,45(9):2695-2700
The use of a novel synchronization link to compensate time, phase, and spatial synchronization errors is proposed, aiming at the development of a practical synchronization technique for bistatic synthetic aperture radar (BiSAR) real-time imaging. With the proposed technique, an amplitude-modulated signal emitting from the transmitter is received by a passive receiver and divided into two channels. One is passed through an envelope detector and then used to trigger the sampling clock, and the second is used to achieve spatial synchronization and phase synchronization. Finally, the residual time synchronization errors are compensated with a proposed high-precision range realignment method, and the residual phase synchronization errors are compensated with autofocus algorithms. This technique allows a passive receiver, which is teamed with an illuminator at a safe standoff distance, to receive the data reflected from potentially hostile areas of interest. Thus, this configuration, making real-time imaging possible, has a particular value in military applications. Simulation results show that successful adaptive synchronization for BiSAR real-time imaging is possible by using this dedicated synchronization link. 相似文献