Showing papers on "Orthogonal frequency-division multiplexing published in 1999"
TL;DR: The results show that the proposed algorithm outperforms multiuser OFDM systems with static time-division multiple access (TDMA) or frequency-divisionmultiple access (FDMA) techniques which employ fixed and predetermined time-slot or subcarrier allocation schemes.
Abstract: Multiuser orthogonal frequency division multiplexing (OFDM) with adaptive multiuser subcarrier allocation and adaptive modulation is considered. Assuming knowledge of the instantaneous channel gains for all users, we propose a multiuser OFDM subcarrier, bit, and power allocation algorithm to minimize the total transmit power. This is done by assigning each user a set of subcarriers and by determining the number of bits and the transmit power level for each subcarrier. We obtain the performance of our proposed algorithm in a multiuser frequency selective fading environment for various time delay spread values and various numbers of users. The results show that our proposed algorithm outperforms multiuser OFDM systems with static time-division multiple access (TDMA) or frequency-division multiple access (FDMA) techniques which employ fixed and predetermined time-slot or subcarrier allocation schemes. We have also quantified the improvement in terms of the overall required transmit power, the bit-error rate (BER), or the area of coverage for a given outage probability.
2,925 citations
TL;DR: With the proposed channel estimator, combining OPDM with transmitter diversity using space-time coding is a promising technique for highly efficient data transmission over mobile wireless channels.
Abstract: Transmitter diversity is an effective technique to improve wireless communication performance. In this paper, we investigate transmitter diversity using space-time coding for orthogonal frequency division multiplexing (OFDM) systems in high-speed wireless data applications. We develop channel parameter estimation approaches, which are crucial for the decoding of the space-time codes, and we derive the MSE bounds of the estimators. The overall receiver performance using such a transmitter diversity scheme is demonstrated by extensive computer simulations. For an OFDM system with two transmitter antennas and two receiver antennas with transmission efficiency as high as 1.475 bits/s/Hz, the required signal-to-noise ratio is only about 7 dB for a 1% bit error rate and 9 dB for a 10% word error rate assuming channels with two-ray, typical urban, and hilly terrain delay profiles, and a 40-Hz Doppler frequency. In summary, with the proposed channel estimator, combining OPDM with transmitter diversity using space-time coding is a promising technique for highly efficient data transmission over mobile wireless channels.
894 citations
TL;DR: The inner OFDM receiver and its functions necessary to demodulate the received signal and deliver soft information to the outer receiver for decoding are focused on.
Abstract: Orthogonal frequency-division multiplexing (OFDM) is the technique of choice in digital broad-band applications that must cope with highly dispersive transmission media at low receiver implementation cost. In this paper, we focus on the inner OFDM receiver and its functions necessary to demodulate the received signal and deliver soft information to the outer receiver for decoding. The effects of relevant nonideal transmission conditions are thoroughly analyzed: imperfect channel estimation, symbol frame offset, carrier and sampling clock frequency offset, time-selective fading, and critical analog components. Through an appropriate optimization criterion (signal-to-noise ratio loss), minimum requirements on each receiver synchronization function are systematically derived. An equivalent signal model encompassing the effects of all relevant imperfections is then formulated in a generalized framework. The paper concludes with an outline of synchronization strategies.
891 citations
TL;DR: Transmitter redundancy introduced using filterbank precoders generalizes existing modulations including OFDM, DMT, TDMA, and CDMA schemes encountered with single- and multiuser communications and develops jointly optimal transmitter-receiver filterbank designs based on maximum output SNR and minimum mean-square error criteria.
Abstract: Transmitter redundancy introduced using filterbank precoders generalizes existing modulations including OFDM, DMT, TDMA, and CDMA schemes encountered with single- and multiuser communications. Sufficient conditions are derived to guarantee that with FIR filterbank precoders FIR channels are equalized perfectly in the absence of noise by FIR zero-forcing equalizer filterbanks, irrespective of the channel zero locations. Multicarrier transmissions through frequency-selective channels can thus be recovered even when deep fades are present. Jointly optimal transmitter-receiver filterbank designs are also developed, based on maximum output SNR and minimum mean-square error criteria under zero-forcing and fixed transmitted power constraints. Analytical performance results are presented for the zero-forcing filterbanks and are compared with mean-square error and ideal designs using simulations.
659 citations
TL;DR: A condition for orthogonality of windowing schemes is derived in terms of the discrete Fourier transform (DFT) of the windowing function.
Abstract: Orthogonal frequency division multiplexing (OFDM) is very sensitive to frequency errors caused by frequency differences between transmitter and receiver local oscillators. This sensitivity is analyzed in terms of the complex weighting coefficients which give the contribution of each transmitter subcarrier to each demodulated subcarrier. Previously described windowing and self intercarrier interference (ICI) cancellation methods are analyzed in terms of these weighting coefficients. New ICI cancellation schemes with very much improved performance are described. A condition for orthogonality of windowing schemes is derived in terms of the discrete Fourier transform (DFT) of the windowing function.
606 citations
TL;DR: A simple frequency-domain equalization technique which can compensate for the effect of ICI in a multipath fading channel in orthogonal frequency division multiplexing systems is proposed.
Abstract: A loss of subchannel orthogonality due to time-variant multipath channels in orthogonal frequency division multiplexing (OFDM) systems leads to interchannel interference (ICI) which increases the error floor in proportion to the Doppler frequency. A simple frequency-domain equalization technique which can compensate for the effect of ICI in a multipath fading channel is proposed. In this technique, the equalization of the received OFDM signal is achieved by using the assumption that the channel impulse response (CIR) varies in a linear fashion during a block period and by compensating for the ICI terms that significantly affect the bit-error rate (BER) performance.
606 citations
TL;DR: In this article, a pseudonoise sequence is used for carrier frequency estimation in orthogonal frequency division multiplexing (OFDM) systems, and the estimation range can be widened in proportion to L without the need of a second training symbol.
Abstract: An efficient algorithm has been proposed by Schmidl and Cox (see IEEE Trans. Commun., p.1613-21, 1997) for carrier frequency estimation in orthogonal frequency division multiplexing systems. The scheme is based on the transmission of a training symbol composed of two identical halves in the time domain. Its accuracy is close to the Cramer-Rao bound and its estimation range, which is originally limited to the distance between two adjacent subcarriers, can be widened by exploiting a second training symbol containing some suitable pseudonoise sequence. In this paper we extend this algorithm by considering a training symbol composed of L>2 identical parts. This makes it possible to achieve a better accuracy at the cost of some increase in computational load. Furthermore, the estimation range can be widened in proportion to L without the need of a second training symbol.
534 citations
TL;DR: The peak-to-average power ratio of an OFDM system and the optimal companding coefficient are determined and the symbol error rate of the systems after the companding is derived.
Abstract: A companding technique is proposed to reduce the peak-to-average-power ratio of the orthogonal frequency division multiplexing (OFDM) signal in this paper. The probability density function of the amplitude of the OFDM signal is determined. Because of the Gaussian distribution of the OFDM signal, the companding technique can be quite effective, since a large OFDM signal only occurs infrequently. The peak-to-average power ratio of an OFDM system and the optimal companding coefficient are determined in this paper. The symbol error rate of the systems after the companding is derived. The performances of the system with and without the companding are also compared.
515 citations
TL;DR: Performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on the universal mobile telecommunication system (UMTS) parameters are shown.
Abstract: We present a multiuser synchronization scheme for tracking the mobile's uplink time and frequency offsets. It uses the redundancy introduced by the cyclic prefix and does not need additional pilots. We show performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on the universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coherent system employing the scheme is virtually indistinguishable from the performance of a perfectly synchronized system. In a differentially modulated system, synchronization errors decrease the system performance by about 0.7 dB compared to a perfectly synchronized system.
455 citations
16 May 1999
TL;DR: In this article, a minimum mean-square error (MWE) estimator for a 10% word error rate (WER) is derived for the typical urban channels with 40 Hz and 200 Hz Doppler frequencies.
Abstract: We investigate pilot-symbol-aided parameter estimation for OFDM systems. We first derive a minimum mean-square error pilot-symbol-aided parameter estimator. Then, we discuss a robust implementation of the pilot-symbol-aided estimator that is insensitive to channel statistics. From the simulation results, the required SNRs for a 10% word error rate (WER) are 6.8 dB and 7.3 dB for the typical urban channels with 40 Hz and 200 Hz Doppler frequencies, respectively, and are 8 dB and 8.3 dB for the hilly-terrain channels with 40 Hz and 200 Hz Doppler frequencies, respectively. Compared with the decision-directed parameter estimator, the pilot-symbol-aided estimator is highly robust to Doppler frequency for dispersive fading channels with noise impairment even though it has some performance degradation for systems with lower Doppler frequencies.
317 citations
TL;DR: The spectra of the signal and of the distortion are used to get an accurate estimate of the bit-error rate of an OFDM transmission system and to derive compensation at the receiver, which leads to performance improvement.
Abstract: The power spectral density of an orthogonal frequency-division multiplexing (OFDM) signal after a saturated high-power amplifier (HPA) is analytically derived. The distortion of the HPA-processed OFDM signal is defined, and its power spectrum is computed. The spectra of the signal and of the distortion are used to get an accurate estimate of the bit-error rate of an OFDM transmission system and to derive compensation at the receiver, which leads to performance improvement.
TL;DR: Extensive computer simulation demonstrates that the MMSE-DC using the proposed parameter estimators can effectively suppress both synchronous and asynchronous interference in OFDM systems for packet and continuous data transmission.
Abstract: Orthogonal frequency-division multiplexing (OFDM) is one of the promising techniques for future mobile wireless data systems. For OFDM systems with cochannel interference, adaptive antenna arrays can be used for interference suppression. This paper focuses on a key issue for adaptive antenna arrays, that is, parameter estimation for the minimum mean square error (MMSE) diversity combiner (DC). Using the instantaneous correlation estimation approach developed in the paper, an original parameter estimator for the MMSE-DC is derived. Based on the original estimator, we propose an enhanced parameter estimator. Extensive computer simulation demonstrates that the MMSE-DC using the proposed parameter estimators can effectively suppress both synchronous and asynchronous interference in OFDM systems for packet and continuous data transmission.
TL;DR: The investigation indicates that delay transmitter diversity with quaternary phase-shift keying (QPSK) modulation and adaptive antenna arrays provides a good quality of service (QoS) with low retransmission probability, while space-time coding transmitter diversity provides high peak data rates.
Abstract: Transmitter diversity and down-link beamforming can be used in high-rate data wireless networks with orthogonal frequency division multiplexing (OFDM) for capacity improvement. We compare the performance of delay, permutation and space-time coding transmitter diversity for high-rate packet data wireless networks using OFDM modulation. For these systems, relatively high block error rates, such as 10%, are acceptable assuming the use of effective automatic retransmission request (ARQ). As an alternative, we also consider using the same number of transmitter antennas for down-link beamforming as we consider for transmitter diversity. The investigation indicates that delay transmitter diversity with quaternary phase-shift keying (QPSK) modulation and adaptive antenna arrays provides a good quality of service (QoS) with low retransmission probability, while space-time coding transmitter diversity provides high peak data rates. Down-link beamforming together with adaptive antenna arrays, however, provides a higher capacity than transmitter diversity for typical mobile environments.
TL;DR: A novel subspace approach for blind channel identification using cyclic correlations at the OFDM receiver and Simulations of the proposed channel estimator along with its performance in OFDM systems combined with impulse response shortening and Reed-Solomon coding are presented.
Abstract: Transmitter-induced cyclostationarity has been explored previously as an alternative to fractional sampling and antenna array methods for blind identification of FIR communication channels. An interesting application of these ideas is in OFDM systems, which induce cyclostationarity due to the cyclic prefix. We develop a novel subspace approach for blind channel identification using cyclic correlations at the OFDM receiver. Even channels with equispaced unit circle zeros are identifiable in the presence of any nonzero length cyclic prefix with adequate block length. Simulations of the proposed channel estimator along with its performance in OFDM systems combined with impulse response shortening and Reed-Solomon coding are presented.
01 Jan 1999
TL;DR: This paper extends the proposed algorithm for carrier frequency estimation in orthogonal frequency division multiplexing systems by considering a training symbol composed of L>2 identical parts, which makes it possible to achieve a better accuracy at the cost of some increase in computational load.
Abstract: An efficient algorithm has been proposed by Schmidl and Cox (see IEEE Trans. Commun., p.1613-21, 1997) for carrier frequency estimation in orthogonal frequency division multiplexing systems. The scheme is based on the transmission of a training symbol composed of two identical halves in the time domain. Its accuracy is close to the Cramer-Rao bound and its estimation range, which is originally limited to the distance between two adjacent subcarriers, can be widened by exploiting a second training symbol containing some suitable pseudonoise sequence. In this paper we extend this algorithm by considering a training symbol composed of L>2 identical parts. This makes it possible to achieve a better accuracy at the cost of some increase in computational load. Furthermore, the estimation range can be widened in proportion to L without the need of a second training symbol.
TL;DR: An asynchronous multicarrier (MC) direct-sequence (DS) code-division multiple-access (CDMA) scheme for the uplink of the mobile communication system operating in a frequency selective fading channel performs better than that of the conventional DS-CDMA system and another MC-DS- CDMA system.
Abstract: An asynchronous multicarrier (MC) direct-sequence (DS) code-division multiple-access (CDMA) scheme for the uplink of the mobile communication system operating in a frequency selective fading channel is analyzed. The bit error rate performance of the system with either equal gain combining or maximum-ratio combining is obtained. Numerical results indicate that the system performs better than that of the conventional DS-CDMA system and another MC-DS-CDMA system.
TL;DR: The DAR technique can mitigate the clipping noise significantly for OFDM systems that have large block sizes and the effect of using a realistic channel estimate is examined.
Abstract: Clipping is often used to reduce the large peak-to-mean envelope power ratio of orthogonal frequency-division multiplexing (OFDM) signals. However, it introduces additional noise that degrades the system performance. A technique called decision-aided reconstruction (DAR) is proposed for mitigating the clipping noise. The performance of the proposed technique is evaluated for additive white Gaussian noise and static intersymbol interference channels. The effect of using a realistic channel estimate is also examined. Results show that the DAR technique can mitigate the clipping noise significantly for OFDM systems that have large block sizes.
01 Jan 1999
TL;DR: To extend this work to OFDM(A) mobile radio systems in the uplink case where many users' contributions to the ICI overlap, the concept of an equivalent single-user which causes the total ICI is introduced in order to use the same analytical framework.
Abstract: We analyze the effects of Doppler spread in mobile channels on orthogonal frequency division multiplex (OFDM) systems. This is important, since channel variations during one OFDM symbol cause inter sub-carrier interference (ICI) in OFDM systems, which degrades the performance, since ICI can be seen as additional near-Gaussian noise. The analysis is outlined, and closed-form results given for numerous important practical Doppler spread encountered in mobile channels. We also show that for the case of asymmetrical Doppler spreads, the frequency correction of the receiver can be adjusted so as to minimize the ICI. To extend our work to OFDM(A) mobile radio systems in the uplink case where many users' contributions to the ICI overlap, we have introduced the concept of an equivalent single-user which causes the total ICI, in order to use the same analytical framework. For some channel examples, we simulated the Doppler spread of this equivalent user. Simulation results confirm our analysis and show the importance of the analytical tool to perform realistic system analysis without having to resort to time consuming time-domain simulations.
19 Sep 1999
TL;DR: To deal with the frequently changing channel characteristic of a fast time-varying multipath fading channel, a heuristic algorithm based on constructive assignment and iterative improvement is proposed which can give out a valid solution in real time.
Abstract: In this paper, we propose sub-carrier allocation algorithms for a multiple access scheme in downlink OFDM transmission. Knowing the channel characteristics of all the users at the base station, the sub-carrier allocation algorithm assigns sub-carriers to the users in a way that the total transmit power is minimized. An optimal algorithm is presented to provide the best sub-carrier assignment. The complexity of the optimal solution renders it impractical for real-time application. To deal with the frequently changing channel characteristic of a fast time-varying multipath fading channel, a heuristic algorithm based on constructive assignment and iterative improvement is proposed which can give out a valid solution in real time. Experimental results show that the performance of this real-time algorithm is close to that of the optimal allocation.
01 Jan 1999
TL;DR: In this article, the authors compare and analyze preambles for OFDM systems based on repeated OFDM data symbols or repeated short pseudonoise sequences (PN-sequences) for AWGN channels and simulate the performance in oneand two-tap Rayleigh fading channels.
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.
TL;DR: The proposed novel subblock partition scheme for PTS OFDM shows almost same PAPR reduction performance as compared to the conventional pseudo-random SPS which has been known to have the best performance, and computational complexity can be reduced extensively.
Abstract: In general, there has been a trade-off between performance of peak-to-average power ratio (PAPR) reduction and computational complexity in partial transmit sequence (PTS) orthogonal frequency division multiplexing (OFDM). In this paper, a novel subblock partition scheme (SPS) for PTS OFDM is proposed and analyzed. In this scheme, signals assigned randomly in partial subbands are duplicated and concatenated repetitively to generate each subblock. The proposed scheme, therefore, has a form of concatenation of pseudo-random and interleaved SPS. As results of simulations, the proposed scheme shows almost same PAPR reduction performance as compared to the conventional pseudo-random SPS which has been known to have the best performance. However, computational complexity can be reduced extensively. Hence, the proposed scheme may be considered to be more suitable than the conventional ones for application in high speed transmission systems such as digital terrestrial broadcasting.
Patent•
30 Dec 1999TL;DR: In this article, the authors proposed a highly modular PACS-based system that combines the advantages of OFDM and Personal Access Communication System (PACS) with Time Division Multiple Access (TDMA) technology.
Abstract: A highly modular PACS-based system that combines the advantages of Optical Frequency Division Multiplexing (OFDM) and Personal Access Communication System (PACS) with Time Division Multiple Access (TDMA) technology. The system is arranged to support high-speed (higher than the 32 kbps of PACS) wireless access services to fixed and mobile users. For example, nominal user data rates of 32-to-356 kbps are attainable, and ever the higher speed of 768 kbps is possible for short ranges.
01 Jan 1999
TL;DR: The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time variant radio channels.
Abstract: Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, an appropriate transmission technique has to cope with frequency-selective and time-variant radio channels. The computation complexity for an equalizer increases in a frequency-selective radio channel for high data-rate applications. Furthermore, the overhead for channel estimation procedures increases in time-variant channels. To overcome these drawbacks orthogonal frequency division multiplexing (OFDM) has been considered for broad-band applications in many publications. The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time-variant radio channels. In this paper several technical aspects of OFDM transmission systems are discussed, especially the topics of differential modulation for which we compare different demodulation methods and channel coding with soft decision decoding. For higher level differential modulation, multilevel coding is taken into consideration.
TL;DR: This work investigates how various parameters, such as the number of carriers, the guard time length, and the sampling offset between receiver and transmitter, affect the system performance and determines the optimum values of the above parameters, which minimize the degradation of the signal to-noise ratio at the input of the decision device.
Abstract: In mobile radio communication, the fading channels generally exhibit both time-selectivity and frequency-selectivity. Orthogonal frequency-division multiplexing has been proposed to combat the frequency-selectivity, but its performance is also affected by the time-selectivity. We investigate how various parameters, such as the number of carriers, the guard time length, and the sampling offset between receiver and transmitter, affect the system performance. Further, we determine the optimum values of the above parameters, which minimize the degradation of the signal to-noise ratio at the input of the decision device.
01 Oct 1999
TL;DR: In this paper, the authors describe the large potential, the flexibility and adaptivity of the orthogonal frequency division multiplexing (OFDM) transmission technique in frequency-selective and time-variant radio channels.
Abstract: Future multimedia services will require the transmission of very high data rates over broad-band radio channels. In order to provide these services to mobile users, an appropriate transmission technique has to cope with frequency-selective and time-variant radio channels. The computation complexity for an equalizer increases in a frequency-selective radio channel for high data rate applications. Furthermore, the overhead for channel estimation procedures increases in time-variant channels. To overcome these drawbacks orthogonal frequency division multiplexing (OFDM) has been considered for broadband applications in many publications. The objective of this paper is to describe the large potential, the flexibility and adaptivity of the OFDM transmission technique in frequency-selective and time variant radio channels. Several technical aspects of OFDM transmission systems are discussed, especially the topics of differential modulation for which we compare different demodulation methods and channel coding with soft decision decoding. For higher level differential modulation, multilevel coding is taken into consideration.
TL;DR: In this paper, a fast low-complexity synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems over fading channels is presented. But the implementation can be simplified by only using the sign bits of the in-phase and the quadrature components of the received OFDM signal for frame synchronization and frequency offset compensation.
Abstract: This paper presents a fast low-complexity synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems over fading channels. By utilizing the guard interval in OFDM signals, the frame synchronization and the frequency offset estimation are considered simultaneously. The implementation can be simplified by only using the sign bits of the in-phase and the quadrature components of the received OFDM signal for frame synchronization and frequency offset compensation. A frequency-offset independent frame synchronization algorithm is derived, and a low-complexity frequency offset estimator based on the synchronized correlator output is presented in this paper. Due to the subcarrier ambiguity in the guard-interval-based (GIB) frequency detector, the maximum correctable frequency range is limited to /spl plusmn/1/2 of the subcarrier spacing. In this paper, we also present a new frequency acquisition scheme that can solve the subcarrier ambiguity problem and extend the frequency acquisition range to nearly a half of the useful OFDM signal bandwidth.
TL;DR: The combined influence of the interchannel and intersymbol interferences, which result from the time variation and delay spread of mobile channels, on the performance of an orthogonal frequency-division multiplexing (OFDM) system is analyzed.
Abstract: We analyze the combined influence of the interchannel and intersymbol interferences, which result from the time variation and delay spread of mobile channels, on the performance of an orthogonal frequency-division multiplexing (OFDM) system. Both analysis and simulation results are presented for uncoded 16-QAM. We also investigate the performance of a Reed-Solomon (RS) coded 16-QAM OFDM system when the number of subcarriers varies: it is observed that there is an optimum number of subcarriers that minimizes the post decoding symbol error probability of the RS code for each channel state.
01 Jan 1999
TL;DR: A frequency-offset independent frame synchronization algorithm is derived, and a low-complexity frequency offset estimator based on the synchronized correlator output is presented, which can solve the subcarrier ambiguity problem and extend the frequency acquisition range to nearly a half of the useful OFDM signal bandwidth.
Abstract: This paper presents a fast low-complexity synchronization scheme for orthogonal frequency division multiplexing (OFDM) systems over fading channels. By utilizing the guard interval in OFDM signals, the frame synchronization and the frequency offset estimation are considered simultaneously. The implementation can be simplified by only using the sign bits of the in-phase and the quadrature components of the received OFDM signal for frame synchronization and frequency offset compensation. A frequency-offset independent frame synchronization algorithm is derived, and a low-complexity frequency offset estimator based on the synchronized correlator output is presented in this paper. Due to the subcarrier ambiguity in the guard-interval-based (GIB) frequency detector, the maximum correctable frequency range is limited to /spl plusmn/1/2 of the subcarrier spacing. In this paper, we also present a new frequency acquisition scheme that can solve the subcarrier ambiguity problem and extend the frequency acquisition range to nearly a half of the useful OFDM signal bandwidth.
TL;DR: A method based on amplitude limiting and forward error correcting (AL-FEC) coding is proposed for reduction of the PAPR of the orthogonal multicarrier modulation.
Abstract: A main disadvantage of orthogonal multicarrier modulation is that it exhibits a high peak-to-average-power ratio (PAPR). Because of this, all circuits between the output of the modulator and the input of the demodulator must be linear within a large dynamic range to avoid distortions and spectral spreading. It is therefore desirable to limit the PAPR of the multicarrier signal. A method based on amplitude limiting and forward error correcting (AL-FEC) coding is proposed for reduction of the PAPR. The performance of the AL-FEC is compared to two methods, based on block coding, specially constructed to reduce the PAPR. The AL-FEC is superior as compared to the existing methods. Moreover, its practical realization is very simple for any number of carriers.
Patent•
09 Aug 1999
TL;DR: In this article, the authors proposed a combined Digital-Analog Signal Processors, Waveforms with Time Constrained Signal (TCS) response and Long Response (LR) filtered Bit Rate Agile (BRA) Modulation-Demodulation (Modem) Format Selectable (MFS) and Code Selectable(CS) system implementations for Interoperable Multiple Standard Enhanced GSM, CSMA, TDMA, OFDM, and third-generation CDMA, WCDMA and B-CDMA systems and associated methods Systems include Feher's Ga
Abstract: Combined Digital-Analog Signal Processors, Waveforms with Time Constrained Signal (TCS) response and Long Response (LR) filtered Bit Rate Agile (BRA) Modulation-Demodulation (Modem) Format Selectable (MFS) and Code Selectable (CS) system implementations for Interoperable Multiple Standard Enhanced GSM, CSMA, TDMA, OFDM, and third-generation CDMA, W-CDMA and B-CDMA systems and associated methods Systems include Feher's Gaussian Minimum Shift Keying (GMSK or FGMSK) and Feher's Quadrature Phase Shift Keying (FQPSK) systems combined with Adaptive Antenna Arrays (AAA), Pseudo-Error (PE) based Non-Redundant Error Detection (NRED) controlled IF adaptive equalizers, smart antenna and smart diversity systems which have spectral/RF power efficiency and enhanced end-to-end performance