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突发数传中,如何有效地建立同步是系统的重要技术问题之一。本文提出了一种用软件实现的快速捕获群同步,锁定位同步(码元相位)的方法。 相似文献
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主要分析TCDMA移动通信系统中的两种重要的快速捕获技术(并行捕获技术和匹配滤波器同步捕获技术,给出了他们的实现方案、系统框图等)。 相似文献
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现有技术在处理多通道并行接收数据的同步捕获时,通常采用全精度计算,由于计算复杂,通常需要消耗大量的片上资源,当数据为多通道并行接收数据时,其资源消耗通常是单通道资源消耗的整数倍,这导致了在资源紧张的情况下捕获过程无法正确实现。为了解决以上资源消耗问题,提出了一种基于多通道并行接收的同步捕获及速率判决方法,在利用较少硬件资源实现多通道并行捕获的同时,基于快速速率识别算法,实现速率识别。 相似文献
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介绍低码速率下的PSK遥控副载波实现快速可靠捕获并进行载波同步与位同步的数字化解调方法.给出了数字化解调原理、载波同步、位同步方法并给出仿真,结果具有一定的参考价值. 相似文献
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突发OFDM系统中的快速符号定时同步 总被引:1,自引:1,他引:0
提出了一种在突发OFDM系统中,基于改进前导序列的快速粗符号定时方法。与传统算法比较,该算法不受频率偏移的影响,适合于频偏捕获之前的符号定时同步。运算复杂度降低,适合于突发通信中的快速同步。提高了定时精度,克服了传统算法符号定时模糊的缺点,所以特别适合于突发模式下频偏捕获之前的快速粗符号定时同步。 相似文献
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Cell search in W-CDMA 总被引:9,自引:0,他引:9
In a CDMA cellular system, the process of the mobile station searching for a cell and achieving code and time synchronization to its downlink scrambling code is referred to as cell search. Cell search is performed in three scenarios: initial cell search when a mobile station is switched on, idle mode search when inactive, and active mode search during a call. The latter two are also called target cell search. This paper presents algorithms and results for both initial and target cell search scenarios for the wideband CDMA (W-CDMA) standard. In W-CDMA, the cell search itself is divided into five acquisition stages: slot synchronization, frame synchronization and scrambling code group identification, scrambling code identification, frequency acquisition, and cell identification. Initial cell search needs all five stages, while target cell search in general does not need the last two stages. A pipelined process of the first three stages that minimizes the average code and time acquisition time, while keeping the complexity at a reasonable level, is considered. The frequency error in initial cell search, which may be as large as 20 kHz, is taken care of by partial symbol despreading and noncoherent combining. Optimization of key system parameters such as the loading factors for primary synchronization channel, synchronization channel, and common pilot channel for achieving the smallest average code and time acquisition time is studied. After code and time synchronization (the first three stages), a maximum likelihood (ML)-based frequency acquisition method is used to bring down the frequency error to about 200 Hz. The gain of this method is more than 10 dB compared to an alternative scheme that obtains a frequency error estimate using differential detection 相似文献
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We describe a technique for jointly encoding the rasterscan sync and data framing information for digital TV phone systems in which synchronous sampling is employed for picture encoding. The technique yields: 1) fast acquisition and hard locking synchronization; 2) highly stable picture displays; and 3) reduced channel capacity requirements. 相似文献
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Byoung-Hoon Kim Byeong Gi Lee 《Communications Magazine, IEEE》2000,38(11):124-131
This article introduces the key concepts, organization, and operations of distributed sample-based acquisition (DSA) systems, which have previously been introduced for fast and robust synchronization of the long-period scrambling codes in DS/CDMA environments. In DSA systems, the transmitter samples and sends the state of its main sequence generator, or main shift register generator (SRG), in a distributed manner over the short-period igniter sequence, and the receiver detects and applies the state samples to correct the state of its main SRG, thereby acquiring SRG synchronization after a round of state reception. Acquisition performance of DSA techniques is extremely fast and robust compared to typical correlation-based acquisition techniques of comparable complexity. This article discusses the operation and performance of DSA techniques in the DS/CDMA communication environment as well as their applications to intercell synchronous and asynchronous cellular systems. 相似文献
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突发通信具有环境噪声大,突发帧短等特点,常规的解调器不能满足要求,文中提出了一种全数字突发信号实现方案,以并行进行位同步,载波同步等加快捕获速度.通过在Xilinx的FPGA上实现,并经工程测试表明,该接收机具有高速传输、捕获速度快等特点,适合高速突发通信场合使用. 相似文献
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Byoung-Hoon Kim Byeong Gi Lee 《Selected Areas in Communications, IEEE Journal on》2000,18(8):1455-1469
We introduce a fast fell-search scheme based on the distributed sample acquisition (DSA) technique for inter-cell asynchronous DS/CDMA systems. The proposed DSA scheme enables the long-code acquisition extremely fast even without employing any passive matched filter which used to dominate synchronization circuit complexity in asynchronous DS/CDMA systems. In the DSA-based asynchronous DS/CDMA system, each base station spreads its DQPSK-modulated long-code generator information with an assigned short-period igniter sequence, and broadcasts it as a common pilot signal. A mobile station first identifies and acquires the igniter sequence of the cell group currently located, then detects the conveyed long-code generator information by despreading the acquired igniter sequence, thereby identifying and synchronizing the long-code of the current cell. The mean acquisition time of this proposed DSA-based inter-cell asynchronous DS/CDMA system, evaluated under the assumption that each of 512 cell-specific long-codes is a 10-ms segment (38400-chips for the chip rates of 3.84 Mchips/s) of complex Gold codes of period 218-1 and the igniter sequence (or, group code) set is composed of 7 complex orthogonal Gold codes of period 256, turned out even shorter than that of the inter-cell synchronous DS/CDMA systems employing the conventional serial search method. Furthermore, simulation results showed that the DSA scheme employing a passive matched filter is much superior in terms of acquisition time and robustness, to the 3GPP W-CDMA synchronization scheme having comparable complexity 相似文献
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James Aweya Delfin Y. Montuno Michel Ouellette Kent Felske 《International Journal of Communication Systems》2007,20(6):669-694
Circuit emulation service (CES) allows time‐division multiplexing (TDM) services (T1/E1 and T3/E3 circuits) to be transparently extended across a packet network. With circuit emulation over IP, for instance, TDM data received from an external device at the edge of an IP network is converted to IP packets, sent through the IP network, passed out of the IP network to its destination, and reassembled into TDM bit stream. Clock synchronization is very important for CES. This paper presents a clock synchronization scheme based on a double exponential filtering technique and a linear process model. The linear process model is used to describe the behaviour of clock synchronization errors between a transmitter and a receiver. In the clock synchronization scheme, the transmitter periodically sends explicit time indications or timestamps to a receiver to enable the receiver to synchronize its local clock to the transmitter's clock. A phase‐locked loop (PLL) at the receiver processes the transmitted timestamps to generate timing signal for the receiver. The PLL has a simple implementation and provides both fast responsiveness (i.e. fast acquisition of transmitter frequency at a receiver) and significant jitter reduction in the locked state. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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In order to achieve fast synchronization of the modulation hopping system, a synchronization scheme called short code to guide long code is adopted, and the initial synchronization hops and service hops are designed in detail. According to the system requirements for short code in the properties of time-varying, safety and balance, an algo- rithm to design wide-gap chaos short code based on TOD is proposed. Synchronization performance analysis shows that the algorithm has good performance, the initial synchronization time and the later entering network synchronization time are short, additionally, maximum synchronization time difference and synchronization maintaining time are long, all of which meet the needs of normal communications, and further verify the synchronization scheme feasible. 相似文献