CiteULike: dcastro's fast

Rapid acquisition of PN sequences with a new decision logic

Jung Lee — 2008-05-15T18:51:28-00:00

Vehicular Technology, IEEE Transactions on, Vol. 53, No. 1. (2004), pp. 49-60.

In this paper, a fast acquisition scheme of pseudonoise (PN) sequences for direct-sequence spread-spectrum systems is proposed. The scheme exploits a new decision logic not only to estimate chip values, but also to check the reliability of the chip estimates. As a result, the internal state of a PN sequence generator is estimated more accurately. We derive the probability of finding a correct state estimate and show that the proposed scheme can reduce the average number of chips for acquisition when compared with the conventional scheme. It is also shown that the performance improvement is more noticeable in the moderate signal-to-noise-ratio range.

An FFT-Based Approach for Fast Acquisition in Spread Spectrum Communication Systems

Sascha Spangenberg — 2008-05-15T18:51:07-00:00

Wireless Personal Communications, Vol. 13, No. 1. (1 May 2000), pp. 27-55.

This paper describes a non-coherent technique forfast acquisition of direct sequence spread spectrum(DS/SS) signals in low earth orbit (LEO) satellitecommunication scenarios. Large Doppler offsets areinherent to such environments and are likely to causemajor problems during the code acquisition phase dueto the introduced frequency ambiguity. In the presentpaper we discuss the use of a set of partialcorrelators for code phase acquisition, combined witha fast Fourier transform (FFT) for the purpose of simultaneous Doppler estimation. We will show that theuse of this architecture largely accelerates thesynchronisation process compared to conventionaltechniques over a wide range of Doppler offsets.Furthermore we discuss the implementation of azero-padded FFT that increases the frequencyresolution to such an extent, that acquisition timesidentical to scenarios without existing Doppler offsetcan be achieved.

Doppler estimation for fast acquisition in spread spectrum communication systems

PM Grant — 2008-05-15T18:49:47-00:00

Spread Spectrum Techniques and Applications, 1998. Proceedings., 1998 IEEE 5th International Symposium on, Vol. 1 (1998), pp. 106-110 vol.1.

This paper describes a non-coherent technique which employs a fast Fourier transform (FFT) for the fast acquisition of direct sequence spread spectrum signals in the presence of large Doppler shifts. The application of an FFT to code acquisition results in decreased acquisition time and can improve the probability of detection. The technique discussed in this paper uses a set of partial correlators and a zero-padded FFT to reduce the search region for code acquisition whilst maintaining good frequency resolution for Doppler offset. This approach will prove most pertinent in future re-configurable terminals

A transmit/receive active antenna with fast low-power optical switching

J Vian — 2008-05-09T06:44:38-00:00

Microwave Theory and Techniques, IEEE Transactions on, Vol. 48, No. 12. (2000), pp. 2686-2691.

This paper presents an optically switched X-band active antenna element for half-duplex transmit/receive (T/R) applications. The antenna element is designed to be a unit cell of a quasioptical array with fast switching between T and R and with built-in phase-shifterless beamforming. The measured performance of the active element is 14 dB gain contributed by the power amplifier (PA) in transmission and 16 dB gain contributed by the low-noise amplifier in reception, with 30 dB isolation between T and R. The switching is accomplished with only 1 μW of optical power for 1.7 μs switching time (1.7 pJ of optical energy) and a rise time of 2 ns at 10 GHz with 7 mW of optical power (14 pJ of optical energy). The design, implementation, and measured performance of the optically controlled transmit/receive circuit are presented

Novel fast GPS/GLONASS code-acquisition technique using low update rate FFT

AJRM Coenen — 2008-05-07T06:45:02-00:00

Electronics Letters, Vol. 28, No. 9. (1992), pp. 863-865.

A novel `differential' decoding technique is proposed which enables pre-averaging instead of postintegration for a substantially low update rate `FFT-IFT' correlation in spread-spectrum (navigational) receivers. <e1>N</e1>-channel code acquisition can be performed to monitor the time dispersion with FFT time left to analyse frequency dispersion in highly reflective areas (e.g. an urban environment)

Rapid code acquisition algorithm employing PN matched filters

YT Su — 2008-05-07T06:43:17-00:00

Communications, IEEE Transactions on, Vol. 36, No. 6. (1988), pp. 724-733.

The performance of four algorithms using pseudonoise matched filters (PNMFs), for direct-sequence spread-spectrum systems, is analyzed. They are: parallel search with fix dwell detector (PL-FDD), parallel search with sequential detector (PL-SD), parallel-serial search with fix dwell detector (PS-FDD), and parallel-serial search with sequential detector (PS-SD). The operation characteristic for each detector and the mean acquisition time for each algorithm are derived. All the algorithms are studied in conjunction with the noncoherent integration technique, which enables the system to operate in the presence of data modulation. Several previous proposal using PNMF are seen as special cases of the present algorithms

New Fast GPS code-acquisition technique using FFT

DJR Van Nee — 2008-05-07T06:42:16-00:00

Electronics Letters, Vol. 27, No. 2. (1991), pp. 158-160.

A new spread-spectrum code-acquisition technique for the navigation systems Navstar/GPS and Glonass is introduced. This technique uses the FFT to compute the correlation function, thereby eliminating the time-consuming code phase shift process. Comparisons with existing systems show a theoretical reduction in acquisition time of about 2000 times

Fast burst synchronisation technique for OFDM-WLAN systems

BY Prasetyo — 2008-04-22T10:51:55-00:00

Communications, IEE Proceedings-, Vol. 147, No. 5. (2000), pp. 292-298.

An MMSE (minimum mean square error) based joint timing and frequency synchronisation algorithm utilising a simplified frame structure is proposed for fast burst synchronisation in orthogonal frequency division multiplexing (OFDM) systems. A single synchronisation symbol is exploited in the time domain to give, first, an estimate of coarse frame starting position and fine frequency offset, and later, in the frequency domain, the multiple of subcarrier spacing frequency offset using a reference symbol power adjustment (RPA) technique. The power of the start symbol, which also acts as a reference symbol in differential modulation, is varied linearly to determine the multiple subcarrier frequency offset. The performance of the proposed frame is confirmed by simulation for a differential quaternary phase shift keying (DQPSK) system in a multipath fading environment

On channel estimation and detection for multicarrier signals in fast and selective Rayleigh fading channels

Yang-Seok Choi — 2007-11-28T10:19:55-00:00

Communications, IEEE Transactions on, Vol. 49, No. 8. (2001), pp. 1375-1387.

Time-domain channel estimation and detection techniques are presented for multicarrier signals in a fast and frequency-selective Rayleigh fading channel. As a consequence of the time-varying channel, the orthogonality between subcarriers is destroyed in conventional frequency-domain approaches, resulting in interchannel interference, which increases an irreducible error floor in proportion to the normalized Doppler frequency. An important feature of the proposed technique is the ability to exploit the time-selective channel as a provider of time diversity. This enables us to achieve performance superior to any other structure without increasing bandwidth or incorporating redundancy, in order to reduce the complexity of the estimator, we apply the theory of optimal low rank approximation to a minimum mean squared error channel estimator and present a theoretical calculation of mean squared error and simulations to confirm that the estimator is robust to changes in channel characteristics

Frequency offset estimation with fast acquisition in OFDM system

Zhongshan Zhang — 2007-11-11T15:43:57-00:00

Communications Letters, IEEE, Vol. 8, No. 3. (2004), pp. 171-173.

A new carrier frequency offset estimation scheme in orthogonal frequency-division multiplexing (OFDM) system is proposed. The carrier frequency offset estimation includes acquisition and tracking, and the acquisition range is as large as one half of overall signal bandwidth. The proposed tracking estimator is a maximum-likelihood estimator, and in AWGN channel, the Cramer-Rao lower bound is met at high signal-to-noise ratio (SNR); in multipath channel, the tracking algorithm works well at moderate SNR. Timing synchronization can be also performed during the course of acquisition.