标题: 数位通讯系统同步技术之研究
Study of Synchronization Techniques for Digital Communication
作者: 刘锦勋
Ging-Shing Liu
魏哲和
Che-Ho Wei
电子研究所
关键字: 载波同步;时序回复;数位用户回路;无线数位行动通讯;适应性通道估测;carrier;timing;subscriber loop;mobile/portable communication; adaptive channel estimator
公开日期: 1993
摘要: 本论文主要探讨高速率电话线传输和数位无线电通讯系统的同步问题, 同
步的层次则包括时序回复与载波相位回复等相关技术o高速率电话线传输
由于严重的符际干扰、近端串音与残留回音增加资料还原和时序回复上的
困难o 为增加时序回复的可靠度, 我们提出一包率取样的时序回复技术o
该法乃利用适应性通道估测技术自估测得到的通道响应中拮取时序资讯o
进一步利用该通道估测器将通道等化、时序回复与微调自动增益等功能结
合以简化硬体复杂度o无线电通道会因城市密集的建筑物或其他地形障碍
而造成多重路径反射的干扰, 使得接收到的信号发生严重衰落(Fading)o
首先, 我们评估一类非线性时序回复技术在衰落通道中的效能并比较之o
由于衰落效应导致同步相位解调困难, 而差分解调虽然毋需载波相位的回
复, 但是频率漂移则会影响系统效能o 在文中, 我们提出一快速频移估测
器并分析频移量和系统效能间的数学关系, 更进一步评估该快速频移估测
器在衰落通道中的效能o 落效应与符际干扰两因素对一般LOS(Line-of-
Sight)无线电通讯系统其载波相位回复的影响, 并分析I-Q 载波相位回复
回路在该系统中的效能o
In the dissertation, we study the clock and the carrier
synchronization for the high-rate digital subscriber lines(
HDSL) and the digital wireless communication systems. In the
HDSL transmission, the severe intersymbol interfere- nce(ISI),
the residual echo and the near-end crosstalk(NEXT) from the
adjacent cables will make the timing recovery and data ion
become more difficult. In the dissertation, we propose a rate
sampling timing recovery method based on an adaptive estimator.
The timing information is extracted from the estimated channel
response rather than from the received signal itself.
Furthermore, the timing recovery, the channel equalization and
fine-tuned automatic gain control (AGC) can be unified simply
by an adaptive channel estimator such that the overall hardware
lexity can be reduced. In the radio propagation, the received
signal suffers from ipath fading due to the reflections of
buildings or terrain. we evaluate a class of nonlinear timing
recovery techniques forπ/4-DQPSK signal in the Rayleigh fading
channels. Since detection does not require carrier phase
recovery, it is more able than coherent detection in the fading
channels. However, ncy offset will degrade the performance of
the differential Thus, we propose a fast frequency offset
estimator for the signal. The relation between the frequency
offset and the symbol rate performance is developed
analytically. Its performance in Rayleigh fading channel is
also analyzed. Finally, we study the performance of I-Q carrier
recovery the line-of-sight(LOS) digital radios subject to the
impairments multipath fading and intersymbol interference(ISI).
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT820430111
http://hdl.handle.net/11536/58118
显示于类别:Thesis