共查询到20条相似文献,搜索用时 22 毫秒
1.
In this letter, we propose a systematic technique for optimum data-sequence design for data-aided (DA) estimation of synchronization parameters. It is assumed that the system operates in burst mode, transmitting a linearly modulated information signal over an additive white Gaussian noise channel. The method is based on the minimization of the corresponding Crameacuter-Rao lower bound subject to a power constraint and is applied in four practical receiver synchronization contexts: estimation of the symbol timing with known carrier frequency offset and either known or unknown carrier phase, joint estimation of the symbol timing and carrier phase with known carrier frequency offset, and joint estimation of the carrier phase and carrier frequency offset with known symbol timing 相似文献
2.
为在载波频率精确恢复前提高多进制数字相位调制(MPSK)信号在低信噪比下的估计精度,提出了一种数据辅助的MPSK信号频域信噪比估计算法。算法在符号定时恢复和帧同步后提取同步段符号,相关运算后在频域进行信噪比估计。仿真结果表明,算法估计均值无偏,不受载波频率误差的影响,在符号长度为512、信噪比为-10 dB时,均方误差与克拉美罗界只有0.15 dB的偏差,特别适合于接收信号包含载波频率误差且要求低信噪比下具有较高信噪比估计性能的应用。 相似文献
3.
In this paper, we present the derivation and analysis of the true Crame/spl acute/r-Rao lower bound (CRB) for the variance of unbiased, data-aided (DA) symbol-timing estimates, obtained from a block of K samples of a linearly modulated information signal, transmitted through an additive white Gaussian noise channel with random carrier phase. We consider a carrier-phase-independent time-delay estimation scenario wherein the carrier phase is viewed as an unwanted or nuisance parameter. The new bounds require only a moderate computational effort and are tighter than the CRB for the variance of unbiased time-delay estimates obtained under the assumption that the carrier phase is known. These bounds are particularly useful to assess the ultimate accuracy that can be achieved by pilot-assisted symbol synchronizers. Conversely, they may be used to evaluate data sequence suitability for the purpose of time-delay estimation. Comparison of the actual variance of a DA feedforward timing estimator with the new bounds show that these are attainable by practical synchronizers. 相似文献
4.
Joint estimation of symbol timing and carrier frequency offset of OFDM signals over fast time-varying multipath channels 总被引:2,自引:0,他引:2
In this paper, we present a novel joint algorithm to estimate the symbol timing and carrier frequency offsets of wireless orthogonal frequency division multiplexing (OFDM) signals. To jointly estimate synchronization parameters using the maximum likelihood (ML) criterion, researchers have derived conventional models only from additive white Gaussian noise (AWGN) or single-path fading channels. We develop a general ML estimation algorithm that can accurately calculate symbol timing and carrier frequency offsets over a fast time-varying multipath channel. To reduce overall estimation complexity, the proposed scheme consists of two estimation stages: coarse and fine synchronizations. A low complexity coarse synchronization based on the least-squares (LS) method can rapidly estimate the rough symbol timing and carrier frequency offsets over a fast time-varying multipath channel. The subsequent ML fine synchronization can then obtain accurate final results based on the previous coarse synchronization. Simulations demonstrate that the coarse-to-fine method provides a good tradeoff between estimation accuracy and computational complexity. 相似文献
5.
大频偏低信噪比条件下OFDM系统中的符号定时估计 总被引:1,自引:1,他引:0
符号定时估计是OFDM系统中的关键问题之一,该文就此问题提出了一种新的基于训练符号的定时估计算法。研究表明,新算法的性能基本不受载波频偏的影响,且具有很强的抗噪特性。通过采用这种算法可将定时误差缩小到只有抽样时间间隔的一半。并且,还可利用这个频域训练符号来进行载波频偏的估计,从而只需一个训练符号就能完成符号定时和载波频偏的联合捕获。 相似文献
6.
In upstream transmission of the DOCSIS (data over cable service interface specification) 1.0/1.1 and the TDMA mode of DOCSIS 2.0 standard, a packet begins with a preamble, the length and value of which are programmable by the headend. The acquisition process includes packet detection, symbol timing estimation, carrier frequency offset estimation and carrier phase estimation by means of the preamble so that the following information packet can be correctly demodulated. Methods to solve these tasks are not subject to standardization and are left to the system designer. However, they have a great impact on the system performance and thus are key elements for implementation. We present dedicated algorithms. A specific preamble is created and the corresponding scheme for packet acquisition is described in some detail. The packet detecting algorithm is independent of the carrier and symbol timing. The symbol timing estimate is obtained by using the minimum mean square algorithm regardless of the carrier frequency deviation and carrier phase. Algorithms for estimating the carrier frequency offset and carrier phase are proposed. Computer simulation results are given for all algorithms presented. 相似文献
7.
We derive new Cramer-Rao lower bounds (CRBs) for the estimation of carrier phase and frequency offset from an unmodulated carrier or from a M-PSK data signal. The new CRBs are obtained formally from the exact likelihood function for the carrier phase and frequency offset, build from a block of received phase samples, and are applicable for a general alphabet size M. The bounds are compared with other previously obtained bounds (which also take into account the effect of random phase modulation) and with the performance of some popular feedforward algorithms for carrier phase and frequency offset estimation 相似文献
8.
9.
10.
针对广义频分复用( GFDM)系统对符号定时同步要求较高的问题,提出了一种新的基于前缀码的同步算法。在接收端,在获取粗略定时信息的基础上,利用前缀码前后两部分的相位差实现载波频偏估计,并对接收序列的频率偏移进行纠正,然后通过纠正后序列与已知发射前缀的互相关函数实现精确的符号定时估计。由于该前缀码具有共轭对称的特性,使其避免了“平顶效应”的出现。结合5G中低时延高可靠场景,在频率选择性信道中对其进行仿真,并通过均方误差对其性能进行了评估。理论分析及仿真结果表明,该算法相对于原算法具有更好的定时同步性能和更低的复杂度,提升了GFDM系统的整体性能。 相似文献
11.
José Luis Hinostroza Ninahuanca Osmar Tormena Jr. Luís Geraldo Pedroso Meloni 《ETRI Journal》2021,43(6):978-990
This article presents techniques for improved estimation of symbol timing offset (STO) and carrier frequency offset (CFO) for dual-polarization (DP) orthogonal frequency division multiplex (DP-OFDM) systems. Recently, quaternion multiple-input multiple-output OFDM has been proposed for high spectral efficiency communication systems, which can flexibly explore different types of diversities such as space, time, frequency, and polarization. This article focuses on synchronization techniques for DP-OFDM systems using a cyclic prefix, where the application of quaternion algebra leads to new improved estimators. Simulations performed for DP system methods show faster reduction of STO estimator variance with a double-slope line in the log-variance line versus signal-to-noise ratio (SNR) plot compared with single-polarization (SP) counterparts, and simulations for CFO estimates show a 3-dB gain of DP over SP estimates for same SNR values defined, respectively, for quaternion-valued or complex-valued signals. Cramer–Rao bounds for STO and CFO are derived for the synchronization methods, correlating with the observed gains of DP over SP OFDM systems. 相似文献
12.
Sevillano J.F. Velez I. Leyh M. Lipp S. Irizar A. Fontan L. 《Wireless Communications, IEEE Transactions on》2007,6(9):3202-3207
In this paper we consider the problem of estimating the signal-to-noise ratio (SNR) of the received signal in a QPSK data transmission system. This estimation must be done in-service (non-data aided), without carrier phase knowledge and without symbol timing phase knowledge. New algorithms with these features are derived from the ratio of two moments. The performance of these algorithms is studied by means of simulations, and it is shown that they are robust against carrier and symbol timing frequency offsets as well. This makes them suitable for a wide range of applications. 相似文献
13.
This paper describes a microprocessor-based modem developed for use in a packet switching network over satellite channels. This digital modem can process both BPSK and QPSK packets with near optimum error rate performance over channels with marginal signal energy-to-noise density ratio. Of principal concern is the development of the discrete time algorithms which form the basis of the microinstruction program. The processing of a packet can be decomposed into two basic stages: (1) the detection of the packet preamble and the rapid estimation of signal parameters (symbol timing and carrier frequency offset) for the specific packet, and (2) the demodulation of the data portion of the packet including the tracking of both symbol timing and carrier offset phase, phase ambiguity resolution and data symbol estimation. The paper concludes with details on the performance of the modem under operational conditions and a brief discussion of implementation of the processor. 相似文献
14.
IEEE802.11a标准中OFDM系统的同步新算法 总被引:3,自引:1,他引:2
根据IEEE802.1la的数据分组结构,利用短训练序列时域响应的特点,对接收到的短训练序列进行窗口平移相关,由相关峰确定符号定时,并利用短训练序列进行粗频偏估计。仿真结果表明,该算法能有效地克服噪声及频偏的影响,定时准确,较好地消除了频偏。与其它文献提出的算法相比,具有定时准确、计算量小、频偏估计范围大的特点。 相似文献
15.
基于最大似然算法的OFDM同步技术研究 总被引:1,自引:0,他引:1
同步问题是卫星通信中的一个关键问题,直接关系到通信系统的性能。文中简要介绍了OFDM的同步技术,主要讨论了符号定时同步和载波同步。最大似然估计算法在OFDM符号定时同步和载波频率同步中得到了广泛的应用,通过最大似然估计方法,避免了基于导频符号的同步估计带来的频率和功率资源的浪费,通过仿真可以看到,能够很好地实现OFDM系统的符号同步和载波同步。 相似文献
16.
17.
It is known that the "better than" raised-cosine pulse has several advantages over the conventional raised-cosine pulse. In addition to the advantages previously reported, this letter reports that the "better than" raised-cosine pulse enables better performance of symbol timing estimation than the raised-cosine pulse. Both Cramer-Rao lower bounds and simulations of practical synchronizers show the superiority of the new pulse. The performance gain can be as much as 3.4 dB for a practical system. 相似文献
18.
19.
This paper proposes two multi-stage joint symbol timing and carrier frequency synchronization schemes for an orthogonal frequency division multiplex (OFDM) system. Simultaneous estimation of symbol timing and frequency offset is derived from the maximum likelihood (ML) principle, assuming a cyclic prefix (guard interval) is inserted in each OFDM symbol. One of the proposed algorithms derives an initial frequency estimate in the first stage that reduces the frequency uncertainty to only two or three sub-carrier spacings. The timing information and a finer frequency estimate that has a resolution of a sub-carrier spacing are obtained in the second stage. The third stage provides an estimation for the residual fractional frequency error. The other algorithm bypasses the first stage for one can use the second stage alone to search for the timing and frequency offsets. However, the computing complexity of the second stage is higher than that of the first stage, thus the three-stage algorithm is a preferred choice unless the frequency uncertainty is small. Simulation results show that both algorithms yield excellent performance not only in white Gaussian channels but also in multipath fading channels. 相似文献