Showing papers on "Frequency-division multiplexing published in 2004"

Frequency division multiplexing of multiple data streams in a wireless multi-carrier communication system

Abstract: Techniques for multiplexing multiple data streams using frequency division multiplexing (FDM) in an OFDM system are described. M disjoint “interlaces” are formed with U usable subbands. Each interlace is a different set of S subbands, where U=M·S. The subbands for each interlace are interlaced with the subbands for each of the other M−1 interlaces. M slots may be defined for each symbol period and assigned slot indices 1 through M. The slot indices may be mapped to interlaces such that (1) frequency diversity is achieved for each slot index and (2) the interlaces used for pilot transmission have varying distances to the interlaces used for each slot index, which improves channel estimation performance. Each data stream may be processed as data packets of a fixed size, and different numbers of slots may be used for each data packet depending on the coding and modulation scheme used for the data packet.

Optimal training signals for MIMO OFDM channel estimation

Abstract: This work presents general classes of optimal training signals for estimation of frequency-selective channels in MIMO OFDM systems. Basic properties of the discrete Fourier transform are used to derive the optimal training signals which minimize the channel estimation mean square error. Both single and multiple OFDM training symbols are considered. Several optimal pilot tone allocations among the transmit antennas are presented and classified as frequency division multiplexing, time division multiplexing, code division multiplexing in frequency-domain, code division multiplexing in time-domain, and combinations thereof. All existing optimal training signals in the literature are special cases of the presented optimal training signals and our designs can be applied to pilot-only schemes as well as pilot-data multiplexed schemes.

Space-time communication for OFDM with implicit channel feedback

Abstract: We consider wideband communication (e.g., using orthogonal frequency-division multiplexed (OFDM) systems) over a typical cellular "downlink," in which both the base station and the mobile may have multiple antennas, but the number of antennas at the mobile is assumed to be small. Implicit channel feedback can play a powerful role in such systems, especially for outdoor channels, which typically exhibit narrow spatial spreads. A summary of our findings is as follows: a) Implicit channel feedback regarding the covariance matrix for the downlink space-time channel can be obtained, without any power or bandwidth overhead, by suitably averaging uplink channel measurements across frequency. Since this approach relies on statistical reciprocity, it applies to both time-division duplex (TDD) and frequency-division duplex (FDD) systems. Using such covariance feedback yields significantly better performance at lower complexity than conventional space-time or space-frequency codes, which do not employ feedback; b) We provide guidelines for optimizing antenna spacing in systems with covariance feedback. Theoretical investigation of a hypothetical system with completely controllable channel eigenvalues shows that the optimal number of channel eigenmodes is roughly matched to the (small) number of receive antenna elements. Thus, while antenna elements in conventional systems without feedback should be spaced far apart in order to ensure uncorrelated responses, the optimal antenna spacing with covariance feedback is much smaller, thereby concentrating the channel energy into a small number of eigenmodes.

Multi-sensor system using plastic optical fibers for intrinsically safe level measurements

Abstract: A system for measuring liquid level in multiple tanks using optical fiber technology has been developed. Oil field service industry or any sector requiring liquid level measurements in flammable atmospheres can be benefited from this intrinsically safe technology. The device used a single lens for the emitting and receiving fiber and it is based on amplitude variations as a function of the liquid distance and not in time of flight or phase detection. Being the first fiber-optic liquid level sensor with those characteristics for long ranges (>200 cm). A simple model to describe their behavior has been derived and tested on two prototypes. A Monte-Carlo method is used to fit the experimental data and obtain the model parameters. High accuracy between experimental data and fitted curve is obtained. The prototypes have a good linearity, better than 1.5% FS (full scale). Sensor heads are made of plastic optical fibers (POF) that are easy to handle, flexible and economical. They are excited by 650 nm lasers, housed in ST-connectors to obtain compact and rough prototypes. Optical multiplexing is used to increase the measuring safety area. Frequency division multiplexing is used to address each sensor head. A discussion about the influence of tilts and aberrations is also included.

An energy adaptive demodulation for high data rates with impulse radio

Abstract: The purpose of This work is to provide an operative way of achieving high data rates for impulse radio (IR) transmission based systems Because applications targeted for ultra wide band (UWB) are low-cost, we especially focus on simple transceiver design To that effect, we present an original demodulation scheme adapted to a multi-band on-off keying (OOK) modulation The receiver's novelty consists of considering only the benefit from approximative delay spread and energy level to relax channel estimation constraints The optimum demodulation turns out to be a non-trivial energetic threshold comparison whose precise theoretical computation admits an original analytical solution proving its feasibility The knowledge of the available energy as well as the noise level required to set the threshold is easily obtained by appropriate estimators Finally, in addition to simple hardware architectures, numerical results show the efficiency of these techniques

Frequency-domain interpolation-based channel estimation in pilot-aided OFDM systems

Abstract: We propose a novel frequency-domain interpolation algorithm for channel estimation in comb-type pilot-aided orthogonal frequency-division multiplexing (OFDM) systems. There exist two major types of pilot-aided OFDM channel estimation methods: time-domain and frequency-domain. We show that these two estimation methods have mathematical equivalence. The performance of these channel estimators mainly depends on how the channel impulse response (CIR) is reconstructed from the frequency-domain channel response sample at the pilot sub-carriers. By closely examining time-domain CIR characteristics, we propose a new frequency-domain interpolation-based algorithm that can overcome the limitation of conventional frequency-domain algorithms. Meanwhile, this new algorithm has the advantages of less latency and computation complexity when compared to time-domain approaches. Simulation results show that the proposed algorithm outperforms frequency-domain interpolation-based and time-domain algorithms in most cases.

Network for telephony and data communication

Abstract: A service outlet for coupling a data unit to a wired digital data signal and for coupling a service unit to an analog service signal, for use with a service wire pair installed in walls of a building, the service wire pair concurrently carrying a wired bi-directional digital data signal and an analog service signal carried over a service signal frequency band, using frequency division multiplexing, wherein the wired digital data signal is carried over a frequency band distinct from the service signal frequency band. The outlet has a single enclosure and, within the enclosure: a wiring connector; first and second filters coupled to the wiring connector; a service connector coupled to the first filter and connectable to the service unit for coupling the service unit to the analog service signal; a service wiring modem coupled to the second filter; and a power supply coupled to the service wiring modem.

Low-complexity nonlinear least squares carrier offset estimator for OFDM: identifiability, diversity and performance

Abstract: Orthogonal frequency division multiplexing (OFDM) transforms frequency-selective channels into multiple low-rate flat-fading subchannels. Carrier frequency offset between transmitter and receiver local oscillators must be estimated and compensated at the receiver to maintain orthogonality of these subchannels. In this paper, we derive the nonlinear least squares (NLS) estimator for carrier frequency synchronization that exploits receiver diversity and known OFDM signal subspace structure due to the placement of unmodulated (virtual) subcarriers. The resulting estimator benefits from the high-resolution subspace method without the computational overhead associated with subspace decomposition. Fundamental estimator performance relationships against parameters such as signal-to-noise ratio (SNR), frequency-selective fading, and diversity branch correlation are derived. In particular, we derive the Cramer-Rao bound (CRB) for the mean square error (MSE) of the carrier frequency offset estimator. Numerical studies are presented to verify the results.

Seamless handover method in an FH-OFDM-based mobile communication system

Abstract: A handoff method in a mobile communication system using frequency hopping-orthogonal frequency division multiplexing (FH-OFDM). A mobile host predicts a handoff according to strength of transmission power of a currently serving base station, reserves a physical channel required for the handoff associated with at least one candidate base station, selects a handoff target base station from the at least one candidate base station, releases a channel with the serving base station, and performs data communication with the target base station through the reserved physical channel.

A novel multicarrier signal transmission system over multipath channel of low-voltage power line

Abstract: As the technique of orthogonal frequency-division multiplexing (OFDM) has the ability to overcome the effect of multipath and to obtain high spectral efficiency of the communication channel, it is generally considered as one of the most effective methods to realize the high-speed digital communication system over the low-voltage powerline. This paper proposes a novel OFDM method, in which the cosine carriers of the conventional OFDM system are replaced with the orthonormal wavelets. A quantitative index used to measure the multipath interference, including the intersymbol interference (ISI) and the interchannel interference (ICI), is induced with a filter bank-based multicarrier transmission system model. The effectiveness of the proposed OFDM over the conventional OFDM in reducing both the ISI and the ICI is verified on a model obtained from the measurements of a practical low-voltage powerline communication channel.

Wavelength division multiplexing optical transmission system

Abstract: A WDM optical transmission system of the invention has a configuration where WDM light generated at a wavelength multiplexing station is transmitted via a plurality of stations such as optical add-drop stations, arranged on an optical transmission line, and control of the power of the optical signals of respective wavelengths included in the WDM light is performed in the wavelength multiplexing station and the optical add-drop stations. A device is provided which communicates between stations, optical signals including information related to the control state of the optical signal power in each station, so that after control of the optical signal power at an upstream station is complete, control of the optical signal power at the downstream station is executed. As a result, stable control in respective stations can be performed even at the time of increasing or decreasing the number of wavelengths.

Analysis of power ramping schemes for UTRA-FDD random access channel

Abstract: The random access channel (RACH) in a universal terrestrial radio access frequency division duplex (UTRA-FDD) system is a contention-based channel mainly used to carry control information from mobile stations to base stations. The transmission of a random access request contains two steps, preamble transmission and message transmission. In preamble transmission, a power ramping technique is used to favor the delayed preambles by stepping up the transmission power after each unsuccessful access. In doing so, the success of transmitting a long-delayed preamble is increased due to the power capture effect. We analyze the blocking and throughput performance of preamble transmission under three power ramping schemes with fixed, linear and geometric step sizes. Also, we compare the interference caused by different power ramping schemes.

Interleaved orthogonal frequency division multiplexing (IOFDM) system

Abstract: In orthogonal frequency division multiplexing (OFDM) systems, for every block of K data samples, an overhead of L samples of cyclic prefix (CP) or zero padding (ZP) is added to combat frequency selective channels. The code rate, which is defined as the ratio K/(K+L), is a measure of the efficiency of transmitting user information. In this paper, a new system is proposed to increase the code rate without increasing the number of subcarriers and without increasing the bandwidth. The proposed system considers appending the L zeros (ZP) once for every P blocks of data samples, which would increase the code rate to PK/(PK+L). It is assumed that the channel is not varying over the transmission of P consecutive data blocks. In order to recover the P data blocks in a computationally efficient manner, an interleaving scheme is proposed, and the proposed system is called the interleaved OFDM (IOFDM) system. Various issues such as computational complexity, peak-to-average power ratio (PAPR), and the effect of synchronization errors on the performance of the IOFDM system are also presented. Based on a numerical simulation study, the average bit-error-rate (BER) performance of the IOFDM system is shown to be very close to that of the OFDM system for a moderate increase in computational complexity and delay.

70-GHz-band MMIC transceiver with integrated antenna diversity system: application of receiver-module-arrayed self-heterodyne technique

Abstract: Our proposed millimeter-wave self-heterodyne transmission technique is a simple and cost-effective solution to frequency stability problems in millimeter-wave access systems. In addition, this technique enables integration of a high-sensitivity receiver with a combining antenna diversity system that is approximately as effective as a maximal-ratio-combining antenna diversity system for all directions of signal arrival. We explain how our newly developed 70-GHz-band transceiver using the millimeter-wave self-heterodyne transmission technique with a receiver-module array can greatly improve receiver sensitivity for all directions of signal arrival i.e., without affecting the signal reception beam pattern and how this can solve the signal-fading problem in a multipath signal propagation environment. We also theoretically demonstrate that receiver sensitivity improves in proportion to the number of elements in a receiver-module array, and experimentally confirm this using an experimental 70-GHz-band monolithic microwave integrated circuit transceiver with a 4/spl times/2 receiver-module array. We show that millimeter-wave signal propagation can be modeled using a two-path model, and that serious signal fading depends on the transceiver height and transmission distance. Carrier and modulated signal transmission experiments using our developed transceiver have revealed that use of a receiver-module array greatly reduces the signal-fading problem in a multipath signal propagation environment. In the signal transmission experiment, we succeeded in transmitting an orthogonal frequency-division multiplexing signal over a 4-m transmission distance with bit-error-free performance.

Throughput study for a dynamic OFDM-FDMA system with inband signaling

Abstract: OFDM-FDMA systems provide the flexibility to support simultaneous downlink data transmissions to different terminals. By dynamically assigning different sets of subcarriers to different terminals they also have the potential to react to fast changing attenuation states of wireless channels. It has been shown that hence dynamic OFDM-FDMA systems can improve various transmission metrics such as throughput or required power. However, these dynamic systems require a signaling mechanism informing each terminal prior to the data transmission itself which subcarriers they have been assigned. We study the dependency between overhead caused by the signaling system and number of subcarriers used in the system for a varying number of terminals in the cell. We find that in terms of resulting throughput per terminal there exists an optimal number of subcarriers into which the bandwidth should be split. This optimal number depends on the setting (especially, terminal number) and provides, if used, a significant performance increase compared to using a fixed number of subcarriers.

Method and apparatus for frequency division multiplexing

Abstract: A radio transmitter and receiver arrangement includes a transmitter and a receiver. The transmitter generates an electromagnetic carrier that varies in frequency throughout a channel interval, and modulates the carrier with an information signal during the channel interval, whereby the carrier is modulated both in frequency and in accordance with the information signal during the channel interval. The receiver receives the carrier that is modulated both in frequency and in accordance with the information signal, generates a detection signal that varies in frequency throughout the channel interval, and mixes the carrier and the detection signal to recover the information signal.

Wavelength multiplexing of frequency-based self-referenced fiber optic intensity sensors

Abstract: A new wavelength multiplexing configuration for self-referenced fiber optic intensity sensors using fiber Bragg gratings and wavelength division multiplexing (WDM) couplers is investigated. First, the network multiplexing concept is characterized, and then the self-referenced intensity sensor is presented, which is the basis of each individual sensor in the network. The implemented experimental setup of the multiplexing network is described, and results are presented considering the crosstalk, resolution, and power budget of the sensing multiplexing network. The characteristics and features of the configuration proposed are addressed.

System and method for 2D partial beamforming arrays with configurable sub-array elements

Abstract: Methods and systems for electronically scanning within a three dimensional volume while minimizing the number of system channels and associated cables connecting a two-dimensional array of elements to an ultrasound system are provided. Larger apertures can be utilized with existing 2D transducer electronics, whose purpose is to reduce the number of conductors in the transducer cable, by having the partially beam formed sub-arrays consist of a sub-array(s) of configurable elements. Exemplary 2D transducer electronics include electronics for the entire beam forming process, partial beam forming, e.g. delaying in time and summing of signals, walking aperture multiplexing, e.g. sequential sub-array actuation, sub-aperture mixing, e.g. delaying in phase and summing, time division multiplexing, e.g. sub-dividing and allocating available bandwidth as a function of time, and frequency division multiplexing, e.g. sub-dividing and allocating available bandwidth as a function of frequency.

Measurement of Demmel condition number for 2/spl times/2 MIMO-OFDM broadband channels

Abstract: The suitability of a complex multiple-input multiple-output (MIMO) channel matrix for spatial multiplexing (SM) is verified experimentally in terms of the Demmel condition number of the instantaneous MIMO channel matrix. Instantaneous 2/spl times/2 MIMO-orthogonal frequency division multiplexing (OFDM) channel measurements in several indoor environments indicate a location dependency of the Demmel condition number. Wideband frequency characteristics of the Demmel condition number in terms of OFDM sub-carriers are also analyzed to evaluate the applicability of SM in a wideband situation.

A novel uplink channel estimation in OFDM-CDMA systems

Abstract: Orthogonal frequency division multiplexing-code division multiplex access (OFDM-CDMA) is one of the best candidates for the future broadband wireless multimedia communication systems. This paper proposes a novel channel estimation algorithm for OFDM-CDMA systems on the uplink. With reasonable constraint and well-designed preambles for each user, the DFT-based uplink channel estimation algorithm can achieve good estimation accuracy without sacrificing much system overhead. Computer simulation demonstrates effectiveness of this method and conclusion is followed.

Frequency estimation method of MB-OFDM UWB system using time frequency hopping strategy

Abstract: There is provided a frequency estimation method of multiband (MB)-orthogonal frequency division multiplexing (OFDM) ultra wide band (UWB) system using an Alt-PHY time frequency (TF) hopping strategy based on IEEE 802. 15. 3a. The frequency estimation method includes the steps of: a) selecting a predetermined number of frequencies among a plurality of center frequencies based on a predetermined number of OFDM symbols and estimating relative frequency offsets for selected frequencies; b) obtaining an average relative frequency offset by averaging the estimated relative frequency offsets when two or more frequencies are selected at the step a); and c) obtaining real frequency offsets for each of the center frequencies by transforming the obtained average relative frequency offset to the real frequency offsets and compensating a frequency offset caused by a transmitting/receiving local oscillators based on the obtained real frequency offsets.

SiGe HBT serial transmitter architecture for high speed variable bit rate intercomputer networking

Abstract: A monolithic transmitter architecture that addresses difficulties in data retiming at high bit rates has been designed and fabricated. It utilises a quarter-frequency multiplexing scheme, a fully symmetric multiplexer and a feedforward interpolated ring voltage controlled oscillator (VCO), to transmit data in excess of 20 Gbit/s. The symmetric multiplexer has full input and output symmetry designed to have the same delay from any input to the output. Each stage in the VCO controls its delay by linearly interpolating the signals from the previous two stages, yielding a VCO tuning range of 3.7 to 5.5 GHz with a phase noise of -90.2 dBc/Hz at 1 MHz. SiGe heterojunction bipolar technology (HBT) technology with an f T of 50GHz was used in this design.

Multicarrier orthogonal spread-spectrum (moss) data communications

Abstract: Systems and methods are described for multicarrier orthogonal spread-spectrum (MOSS) data communication. A method includes individually spread-spectrum modulating at least two of a set of orthogonal frequency division multiplexed carriers, wherein the resulting individually spread-spectrum modulated at least two of a set of orthogonal frequency division multiplexed carriers are substantially mutually orthogonal with respect to both frequency division multiplexing and spread- spectrum modulation.

An adaptive learning approach to adaptive OFDM

Abstract: Orthogonal frequency division multiplex (OFDM) technique has been successfully deployed in indoor wireless LAN and outdoor broadcasting applications. It is well-known that under a frequency-selective fading channel the resultant sub-channel frequency functions are frequency-variant and may also be time-variant, i.e. the channel magnitude may be highly fluctuating across the sub-carriers and varies from symbol to symbol. Hence adaptive modulation may be appropriately applied to improve the error performance and data throughput in an OFDM modem by assigning different modulation and coding schemes to different sub-carriers. One fundamental issue in deploying adaptive modulation is to determine what modulation and coding scheme to use. Virtually all past investigations were either based on heuristic methods or analytical means. This paper proposes a novel adaptive learning control approach that is capable of dynamically adjusting the switching thresholds to improve or maximize the data throughput.

Wireless communication system, and transmitter, receiver and transmitter-receiver used in this system

Abstract: PROBLEM TO BE SOLVED: To provide a wireless communication system for enabling low power consumption at the use of a control channel and the efficient utilization of frequency band resources, and to provide a transmitter, a receiver, and a transmitter-receiver. SOLUTION: In the case of using a data channel, a modulation signal is subjected to serial parallel conversion (402) and Fourier inverse transform (403) to generate a quadrature frequency multiplexing signal and the signal is transmitted by the multicarrier system. In the case of using the control channel, switches (418, 419) are changed over and the modulation signal is transmitted by the single carrier system without applying the Fourier inverse transform to the modulation signal. Thus, the power consumption in the case of using the control channel is lowered and in the case of communicating a voice signal and a data signal or the like, the frequency utilizing efficiency can be improved. COPYRIGHT: (C)2006,JPO&NCIPI

Performance Analysis of Adaptive Transmission Aided by Long Range Channel Prediction for Realistic Single- and Multi-Carrier Mobile Radio Channels

Abstract: Yang, Tung-Sheng. Performance Analysis of Adaptive Transmission Aided by Long Range Channel Prediction for Realistic Singleand Multi-Carrier Mobile Radio Channels. (Under the direction of Dr. Alexandra DuelHallen) Reliable adaptive transmission for frequency selective mobile radio systems is addressed. In particular, we investigate adaptive channel loading for wireless Orthogonal Frequency Division Multiplexing (OFDM) systems and adaptive modulation aided by observations of another carrier (e.g, Frequency Division Duplex (FDD) channels). Adaptive transmission techniques, where the modulation size, coding rate, or other signal transmission parameters are dynamically adapted to the changing channel conditions, have recently emerged as powerful tools for increasing the data rate and spectral efficiency for wireless system. However, reliable adaptive transmission requires long-range prediction (LRP) of future channel state information (CSI) due to the variation of the wireless channel, which results in different channel conditions between the time of data transmission and the time of the channel estimation. We derive the minimum mean-square-error (MMSE) long range channel prediction method that utilizes the time and frequency domain correlation function of the Rayleigh fading channel. Since the channel statistics are usually unknown, reduced complexity robust prediction methods that can converge rapidly to the theoretical MMSE and do not require the knowledge of correlation functions are developed for OFDM channels and systems aided by observations of another carrier. Statistical model of the prediction error that depends on the frequency and time correlation is developed and is used in the design of reliable adaptive modulation methods. A standard sum-of-sinusoids Rayleigh fading channel model and a novel physical model based on the method of images augmented with diffraction are employed to test the prediction algorithm. This physical model can generate non-stationary datasets to test both the LRP and its application in adaptive transmission schemes. It is demonstrated that this physical model generates realistic datasets that closely resemble measured data, and the results of the LRP for the physical model and measured data are similar, and differ significantly from those produced for the Jakes model. We use this model to produce different scenarios to classify typical and challenging cases to test the performance of the proposed prediction algorithm. These cases are more difficult to identify with the measured data. Moreover, we examine the dependency of the correlation between two different carrier frequencies on the variation of the root mean square (rms) delay spread and investigate the limits on the adaptation rate in adaptive transmission systems aided by observations of another carrier. Thus, the physical model allows to test robustness and to determine practical constraints of the proposed adaptive transmission methods. Performance Analysis of Adaptive Transmission Aided by Long Range Channel Prediction for Realistic Singleand Multi-Carrier Mobile Radio Channels

System and method for multiplexed frequency and time data transmission

Abstract: Wireless communications devices ( 102, 104, 106 ) that communicate via an adaptive bandwidth communications protocol ( 300 ). Wireless devices ( 102, 104, 106 ) utilize a multiple carrier time division/frequency division multiplexing format where time slots ( 330, 332 ) are adaptively assigned across multiple RF carriers. Preferred embodiments assign time coincident time slots ( 330, 340, 350, 360 ) on multiple RF carriers so as to allow shorter transmission and reception times and therefore shorter transmitter and receiver activation times in order to conserve power in portable devices ( 104, 106 ). Time slots are adaptively assigned and deallocated in response to events that alter communications bandwidth requirements.

Design of transmit FIR filters for FDM data transmission systems

Abstract: The design of transmit finite-impulse response (FIR) filters with few coefficients in frequency division multiplexing data transmission systems is considered. In these systems, quality objectives are imposed for transmission over channels affected by additive white Gaussian noise (AWGN) and over channels affected by AWGN plus adjacent channel interference (ACI). The goal of this letter is: given that an adaptive receive filter, possibly cooperating with an adaptive decision feedback equalizer, is used for the AWGN channel and for the AWGN plus ACI channel, what is the best fixed FIR transmit filter to use for both channel cases? This goal is achieved by optimizing the compromise between the performance of the system on the two mentioned channels. Also, the advantages of the proposed design over a rival method based on a fixed receive filter are demonstrated.

Impact of RF impairments on a DS-CDMA receiver

Abstract: This letter provides an analysis of the impact of classical radio frequency (RF) front-end impairments (RF mismatch and direct current (dc) offset) on the performance of direct-sequence code-division multiple-access (DS-CDMA) receivers; such issues are of particular importance in the case of zero intermediate-frequency (Zero-IF) receivers. Using a standard expression of the baseband signals as well as basic properties of spreading codes used in DS-CDMA communications, we show that the consequence of such RF mismatch and dc offset is essentially a degradation of the wanted signal's level and an increase of the noise power. We give closed-form expressions (in E/sub b//N/sub 0/ form) for both. The results are then shown to be in accordance with numerical simulations utilizing the codes of the universal terrestrial radio access in the frequency-division duplex mode downlink standard.

Predictability of uplink channels from downlink channels in frequency division duplex systems: a power control application

Abstract: A novel method for performing predictive closed-loop power control is used to illustrate the predictability of uplink channels from downlink channels in a frequency division duplex (FDD) wireless link. In an uplink power control scenario, the proposed scheme performs uplink prediction using downlink-derived (linear) predictor coefficients. Essentially, the lack of correlation between the fading processes on uplink and downlink (due to FDD and frequency selective fading) is circumvented by using the uplink fading history, together with a set of link-independent, autoregressive (AR) coefficients. An AR model is used to formally describe the frequency selective fading process on either link, regardless of the number of Rayleigh paths. It is also proven that the relevant AR coefficients are common to both links, up to a proper normalization, irrespective of whether the number of paths on the uplink differs from that on the downlink. Both an uncoded and a coded system are simulated, and their performance results are compared, on equal grounds, with those of the corresponding nonpredictive systems.