Feedforward symbol timing recovery techniques are particularly important for initial acquisition in burst modems. However, these techniques either have large calculation burden or sensitive to frequency offsets. In th...Feedforward symbol timing recovery techniques are particularly important for initial acquisition in burst modems. However, these techniques either have large calculation burden or sensitive to frequency offsets. In this paper, we proposed an efficient symbol timing recovery algorithm of MPSK signals named OMQ(Ordered Maximum power using Quadratic approximation partially) algorithm which is based on the Quadratic Approximation(QA) algorithm. We used ordered statistic sorting method to reduce the computational complexity further, meanwhile maximum mean power principle was used to decrease frequency offset sensitivity. The proposed algorithm adopts estimation-down sampling structure which is suitable for small packet size transmission. The results show that, while comparing with the QA algorithm, the computational complexity is reduced by 75% at most when 8 samples per symbol are used. The proposed algorithm shows better performance in terms of the jitter variance and sensitivity to frequency offsets.展开更多
Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high...Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.展开更多
Kenneth Burke＇s rhetoric on language as a symbolic action offers an enlightening perspective for revealing the connection between the motivations and actions of the characters in Thomas Kyd＇s The Spanish Tragedy. Th...Kenneth Burke＇s rhetoric on language as a symbolic action offers an enlightening perspective for revealing the connection between the motivations and actions of the characters in Thomas Kyd＇s The Spanish Tragedy. This work is a Renaissance drama that features hues of rhetorical language. Linguistic obfuscation, scapegoat mechanism, and the malfunction and dysfunction of language in victimization and revenge are thrown into relief through Burke＇s elaborate system of the symbolism of language. Analyzing the discursive performances of the main characters, readers could get clues of their motives that drive their actions, which are both a representation and an illustration of how language as a symbolic action works in literature展开更多
The Bit Error Rate (BER) caused by Inter Carrier Interference (ICI) increases greatly with the increase of frequency offset in Orthogonal Frequency Division Multiplexing (OFDM) systems. According to a typical OFDM sig...The Bit Error Rate (BER) caused by Inter Carrier Interference (ICI) increases greatly with the increase of frequency offset in Orthogonal Frequency Division Multiplexing (OFDM) systems. According to a typical OFDM signal model, this letter proves that the coefficient matrix of ICI is a unitary matrix whose inverse matrix is much easier to get, and then proposes a new ICI cancellation method with less computation complexity by sending typical pilot symbols. Compared with two existing ICI cancellation methods, self-cancellation and windowing cancellation, it is shown that the proposed algorithm can cancel ICI better and overcome the limitation of the two traditional methods.展开更多
Let T ： X → X be a transformation. For any x C [0, 1） and r 〉 O, the recurrence time Tr（x） of x under T in its r-neighborhood is defined as Tr（X） = inf{k ≥ 1： d（Tk（x）,x） 〈 r}.For 0 ≤ α ≤ β ∞ co, le...Let T ： X → X be a transformation. For any x C [0, 1） and r 〉 O, the recurrence time Tr（x） of x under T in its r-neighborhood is defined as Tr（X） = inf{k ≥ 1： d（Tk（x）,x） 〈 r}.For 0 ≤ α ≤ β ∞ co, let E（α,β） be the set of points with prescribed recurrence time as follows E（α,β）={x∈X：lim inf r→0 logTr（x）/-logr=α,lim sup r→0 logTr（x）/-logr=β}.In this note, we consider the Gauss transformation T on [0, 1）, and determine the size of E（α,β）by showing that dimH E（α,β） = 1 no matter what a and/~ are. This can be compared with Feng and Wu＇s result [Nonlinearity, 14 （2001）, 81-85] on the symbolic space.展开更多
基金supported by the National Natural Science Foundation of China(NSFC.NO.61303253)
文摘Feedforward symbol timing recovery techniques are particularly important for initial acquisition in burst modems. However, these techniques either have large calculation burden or sensitive to frequency offsets. In this paper, we proposed an efficient symbol timing recovery algorithm of MPSK signals named OMQ(Ordered Maximum power using Quadratic approximation partially) algorithm which is based on the Quadratic Approximation(QA) algorithm. We used ordered statistic sorting method to reduce the computational complexity further, meanwhile maximum mean power principle was used to decrease frequency offset sensitivity. The proposed algorithm adopts estimation-down sampling structure which is suitable for small packet size transmission. The results show that, while comparing with the QA algorithm, the computational complexity is reduced by 75% at most when 8 samples per symbol are used. The proposed algorithm shows better performance in terms of the jitter variance and sensitivity to frequency offsets.
基金supported by the National Natural Science Foundation of China(No.91438114,No.61372111 and No.61601045)
文摘Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.
文摘Kenneth Burke＇s rhetoric on language as a symbolic action offers an enlightening perspective for revealing the connection between the motivations and actions of the characters in Thomas Kyd＇s The Spanish Tragedy. This work is a Renaissance drama that features hues of rhetorical language. Linguistic obfuscation, scapegoat mechanism, and the malfunction and dysfunction of language in victimization and revenge are thrown into relief through Burke＇s elaborate system of the symbolism of language. Analyzing the discursive performances of the main characters, readers could get clues of their motives that drive their actions, which are both a representation and an illustration of how language as a symbolic action works in literature
文摘The Bit Error Rate (BER) caused by Inter Carrier Interference (ICI) increases greatly with the increase of frequency offset in Orthogonal Frequency Division Multiplexing (OFDM) systems. According to a typical OFDM signal model, this letter proves that the coefficient matrix of ICI is a unitary matrix whose inverse matrix is much easier to get, and then proposes a new ICI cancellation method with less computation complexity by sending typical pilot symbols. Compared with two existing ICI cancellation methods, self-cancellation and windowing cancellation, it is shown that the proposed algorithm can cancel ICI better and overcome the limitation of the two traditional methods.
基金supported by National Natural Science Foundation of China (Grant Nos.10631040,10901066)
文摘Let T ： X → X be a transformation. For any x C [0, 1） and r 〉 O, the recurrence time Tr（x） of x under T in its r-neighborhood is defined as Tr（X） = inf{k ≥ 1： d（Tk（x）,x） 〈 r}.For 0 ≤ α ≤ β ∞ co, let E（α,β） be the set of points with prescribed recurrence time as follows E（α,β）={x∈X：lim inf r→0 logTr（x）/-logr=α,lim sup r→0 logTr（x）/-logr=β}.In this note, we consider the Gauss transformation T on [0, 1）, and determine the size of E（α,β）by showing that dimH E（α,β） = 1 no matter what a and/~ are. This can be compared with Feng and Wu＇s result [Nonlinearity, 14 （2001）, 81-85] on the symbolic space.
