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- Leanderson, Carl Fredrik, et al.
(författare)
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On the performance of turbo codes and convolutional codes of low rate
- 1999
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Ingår i: Proc. IEEE Vehicular Technology Conference. - 0780354354 ; 3, s. 1560-1564
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Konferensbidrag (refereegranskat)abstract
- Recently two new classes of low-rate codes have been presented. The first class is the super-orthogonal turbo codes (SOTCs) and the second is the maximum free distance (MFD) convolutional codes. In this paper we present an evaluation of the performance vs. arithmetic decoding complexity for these codes and compare them with the previously reported super-orthogonal convolutional codes (SOCCs). For all classes of codes, the arithmetic decoding complexity is estimated, and the error performance on the additive white Gaussian noise channel is simulated. The SOCCs offer performance comparable to that of the MFD codes. However, the existence of good SOCCs is restricted to a small number of rates while the MFD codes give high performance for a multitude of rates. For the parameters used in this investigation the SOTCs yield higher performance at lower arithmetic decoding complexity than the MFD codes
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| 5. |
- Tufvesson, Fredrik, et al.
(författare)
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OFDM Time and Frequency Synchronization by Spread Spectrum Pilot Technique
- 1999
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Ingår i: Proc. 8th IEEE Communication Theory Mini Conference in conjunction to ICC'99, Vancouver, Canada, June 7-10, 1999. - 0780356535 ; , s. 115-119
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Konferensbidrag (refereegranskat)abstract
- Correct time and frequency synchronization is important for the performance of orthogonal frequency division multiplex (OFDM) systems. We evaluate a system where a pseudonoise sequence (PN-sequence) is used for estimation of these synchronization parameters. The PN-sequence is superimposed on the OFDM signal. The system is evaluated by means of the variance of the frequency estimation error and the probability for correct timing synchronization. Both theoretical and simulated results are presented. The proposed technique is very flexible and works also at low signal to noise ratios. The frequency offset range has been significantly increased compared to conventional OFDM synchronizer schemes
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| 7. |
- Tufvesson, Fredrik, et al.
(författare)
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Time and frequency synchronization for OFDM using PN-sequence preambles
- 1999
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Ingår i: Proceedings of IEEE Vehicular Technology Conference, Amsterdam, The Netherlands, September 19-22, 1999. - 0780354354 ; 4, s. 2203-2207
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Konferensbidrag (refereegranskat)abstract
- Fast and reliable time and frequency synchronization is crucial for packet-based orthogonal frequency division multiplex (OFDM) systems. In this paper we compare and analyze preambles for OFDM systems based on repeated OFDM data symbols or repeated short pseudonoise sequences (PN-sequences). We make an analytical evaluation for AWGN channels and simulate the performance in oneand two-tap Rayleigh fading channels. The PN-based preamble gives better detection properties in terms of lower false detection probability and lower probability of missing the synchronization signal. The PN-based preamble has low peak-to-average power ratio and it makes it possible to use an ADC with one-bit quantization in stand-by mode. For frequency offset estimation both preambles give similar performance, but the PN-based preamble allows for a greater reduction in stand-by mode power consumption
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