1,721,047 research outputs found
Feedforward Frequency Estimation for PSK: A Tutorial Review
No full textThis paper considers feedforward carrier frequency estimation methods in burst-mode digital transmission, with tutorial objectives foremost. Assuming PSK modulation, two scenarios are envisaged in which frequency estimates are derived either from a preamble appended to the data block, or directly from the modulated signal. Several estimation algorithms are considered with different and somewhat contrasting characteristics. The characteristics we focus on are: estimation accuracy, estimation range, minimum operating signal-to-noise ratio (threshold), and implementation complexity. They provide a framework within which current estimation methods can be evaluated. The paper reviews and compares some prominent algorithms proposed in literature, trying to single out the best ones for a given application
Data-Aided Frequency Estimation for Burst Digital Transmission
No full textBurst transmission of digital data is employed in several applications such as satellite time-division multiple access (TDMA) systems and terrestrial mobile cellular radio. We propose a new algorithm for carrier frequency estimation in burst-mode phase shift keying (PSK) transmissions. The algorithm is data-aided and clock-aided and has a feedforward structure that is easy to implement in digital form. Its estimation range is large, about ±20% of the symbol rate and its accuracy is close to the Cramer-Rao bound (CRB) for a signal-to-noise ratio (SNR) as low as 0 dB. Comparisons with earlier methods are discussed
Decomposition of M-ary CPM Signals into PAM Waveforms
No full textIt is widely known that minimum shift keying (MSK) may be seen as a PAM signaling scheme and that the same is true, albeit approximately, with MSK-like modulations. It is also known (perhaps not so widely) that any binary continuous phase-modulated (CPM) signal may be exactly decomposed into the sum of a few PAM waveforms. In this paper we show that this property extends to multilevel CPM signaling. Features of a PAM decomposition are discussed as a function of the alphabet size, the modulation index, and the frequency response of the system. It is found that, especially with signaling schemes with a long memory, the decomposition has so many terms that it becomes unmanageable. For these cases an approximation is proposed with a limited number of terms
Feedforward Carrier Frequency Estimation with MSK-Type Signals
No full textWe propose a non-data-aided technique for the estimation of the carrier frequency offset in minimum-shift keying (MSK)-type modulations. The proposed algorithm has a feedforward structure and is suited for burst-mode transmissions. Computer simulations are used to assess its performance and make comparisons with other existing methods in terms of estimation accuracy and minimum operating signal-to-noise ratio (threshold). Numerical results are provided for modulation schemes of practical interest such as MSK and Gaussian MSK
Frequency Estimation for the Downlink of the UMTS-TDD Component
No full textWe propose a carrier frequency recovery scheme for the downlink of the time-division duplex (TDD) component of the Universal Mobile Telecommunications System (UMTS). The frequency estimator exploits the midamble of the common control channel and takes into account that the frequency offset allowed in the UMTS-TDD is small compared to the chip rate. Simulations are used to assess the accuracy of the proposed scheme assuming diversity reception and a frequency selective channel. It is found that good performance can be achieved with a limited computational load
Channel Estimation for the Downlink of the UMTS-TDD Component
No full textThe time division duplex (TDD) component of the Universal Mobile Telecommunications System (UMTS) employs synchronous CDMA techniques with orthogonal spreading codes to provide protection against cochannel interference. In the presence of multipath propagation, however, the code orthogonality is lost and multiaccess interference is generated at the receiver. In such conditions an estimate of the channel impulse response is required for reliable detection. In this paper we propose a method for channel estimation in the downlink of the UMTS-TDD system. In addition to the channel impulse response, the algorithm provides estimates of the users' powers, which may be needed to perform multiuser detection. Theoretical analysis and computer simulations are used to assess the performance in terms of mean squared estimation error. It is shown that the accuracy of the proposed estimator attains the Cramer-Rao bound (CRB) at signal-to-noise ratios of practical interest
Feedforward ML-Based Timing Estimation with PSK Signals
No full textWe propose a new nondata-aided clock recovery scheme for phase-shift keying (PSK) modulated signals. Its derivation is based on maximum-likelihood (ML) methods and leads to a feedforward structure that can be easily implemented in digital form. The algorithm exhibits improvements with respect to other existing circuits, especially with small excess bandwidth factors. Its performance is assessed by simulation for quaternary PSK (QPSK) and 8PSK formats
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