T. Ekman, M. Sternad and A. Ahl en, "Unbiased power prediction on broadband channels," IEEE VTC, Fall 2002.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....of the bit (thus smaller values are not used) of P (e j ) f(x) where f(x) can be one of the following functions f 1 (x) const, f 2 (x) 1 x , f 3 (x) 1 x , f4 ( x) 5.5556 x 5.2146 x 0.1897 x 1. 0052, where f4 was calculated by interpolating a curve taken from Figure 9 in [6]. Any other analytic or lookup function can be easily implemented. The packet, after going through the channel, carries the information about how many bits suffered errors. This information can be used to decide whether the packet was correctly received or not. This interface allows the ....

T. Ekman, M. Sternad, and A. Ahln. Unbiased power prediction on broadband channels. In Proceedings of IEEE Vehicular Technology Conference 2002.

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T. Ekman, M. Sternad and A. Ahl en, "Unbiased power prediction on broadband channels," IEEE VTC, Fall 2002.

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T. Ekman, M. Sternad, and A. Ahl en, "Unbiased power prediction on broadband channels," Proceedings IEEE Vehicular Technology Conference Fall, Vancouver, Canada, Sep. 2002.

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T. Ekman, M. Sternad and A. Ahlen, "Unbiased power prediction on broadband channels," RVK02, Stockholm, June 2002.

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T. Ekman, M. Sternad and A. Ahlen, "Unbiased power prediction on broadband channels," RVK 02, Stockholm.

....to accumulated gains in efficiency: improved spectral efficiency as well as increased efficiency at higher layers. Sections 2 4 below provide an overview of the research conducted within the project and of our present results. The most recent results are presented in more detail in the papers [2, 3, 4, 5, 6] at this conference. See also our webpage [1] and the Licentiate Theses [7] 8] and [9] 2 Prediction of Fading Channels A main difficulty in data transmission over wireless links to mobile users is the fading, which introduces variations in the channel quality on all time scales. At the lowest ....

....predictors that use channel tap estimates as regressors to predict the power of all significant channel taps. The predictors have been validated on an extensive set of broadband channel measurements [10, 11] see Figure 1 for an illustration. A recently developed unbiased quadratic predictor [3] provides the so far best performance, see Figure 2. We have also obtained a good theoretical understanding of the limits of attainable performance in different propagation environments. 3 The Link and MAC Levels Channel prediction can be used to adapt the data rate to the channel properties, ....

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T. Ekman, M. Sternad and A. Ahlen, "Unbiased power prediction on broadband channels," RVK 02, Stockholm.

....design an optimum adaptive modulation system for a given channel prediction error variance with a corresponding statistical model, which maximizes the spectral efficiency while satisfying a BER requirement. The proposed system utilizes a linear filter to predict the channel quality at the receiver [4], 5] Moreover a statistical model which reasonably well describes the properties of prediction errors is investigated. The model gives a good estimate of the mean, variance and probability density function of the errors. Then, the statistical model is taken into account for performance analysis ....

....as a correlated complex Gaussian stochastic process. The absolute square, i.e. the power, of the time series is predicted based on linear regression of the observations of the complex time series. The unbiased quadratic predictor that is opti mal in the Mean Square Error (MSE) sense is derived in [4] where it is shown that the same prediction coeffi cients that are optimal for the linear prediction of the complex tap, are optimal for the quadratic unbiased predictor. The complex channel gain is observed in noise as yn=gn en (S) where es is assumed to be a complex Gaussian random variable ....

T. Ekman, M. Sternad, and A. Ahl6n, "Unbiased Power Prediction on Broadband Channel," in Proc. Radio Vetenskap och Kommunikation, Sweden, Stockholm, June 2002.

....of the channel should be taken into account. In [9] adaptive modulation schemes based on very accurate long rang CSI prediction are investigated. The system proposed here utilizes an unbiased quadratic regression of historic noisy channel estimates to predict the signal power at the receiver [10], 11] For this type of predictor, there exists a statistical model for the prediction error for Rayleigh fading channels which enables an analytical optimization of the rate adaptation scheme. This statistical model will also be used for analyzing the resulting BER and spectral efficiency for ....

....quadratic power predictor which eliminates this bias. It is given by ### # # ## ## ## (5) Here, ## # ####### ### # is the # # correlation matrix for the regressors. Note that #### ##### #### for all #. The unbiased quadratic predictor that minimizes the power MSE is derived in [10], where it is shown that the predictor coefficient vector # that provides an MSE optimal the channel predictor (3) will also result in an MSE optimal power predictor, when used in (5) The optimal adjustment for both of these problems is thus given by # ### # (6) ### #### ##### # ## #### ## ....

T. Ekman, M. Sternad, and A. Ahlen, "Unbiased Power Prediction on Broadband Channel," in Proc. IEEE Vehicular Technology Conference, Vancouver, Canada, Sept. 2002.

.... obtained by averaging 4aFb the instantaneous BER as a function of both on an Additive White Gaussian Noise (AWGN) channel, over all values of , i.e. d ] 9 3 S d q9D :9 3 : 9 3 9 en e (3) 9 3 is the pdf of conditioned on unbiased power predictor used here [4], provides the pdfs V q9 : 983 T for a given prediction MSE variance, denoted by and average SNR, denoted by [5] Given that, what remains is to find an expression for 4acb d q9 :983 . Tight approximations for the TCM BER performance on AWGN channels at high SNR, based on ....

T. Ekman, M. Sternad, and A. Ahlen, "Unbiased Power Prediction on Broadband Channel," in Proc. IEEE Vehicular Technology Conference, Vancouver, Canada, Sept. 2002.

....a single outdated fading estimate is proposed. In [19 21] adaptive modulation schemes based on accurate long rang CSI prediction is investigated. Here, the proposed system utilizes an unbiased quadratic regression of historic noisy channel estimates to predict the signal power at the receiver [22, 23]. For this type of predictor, there exists a statistical model for the prediction error for Rayleigh fading channels. The model provides the mean, variance and probability density function of the errors. This statistical model enables an analytical optimization of the rate adaptation scheme. It ....

....zons. However, since only noisy observations of the channel are available, predictability will decrease with an increasing horizon. The predictor performance will depend on the use of good channel estimates and the application of noise reducing smoothing, which improve the SNR E[g, 2 E[e, 2 in (6)[22,24]. Based on a finite number of past and present observations y, the complex channel at time n L, could be predicted with a linear FIR filter (8) is the regressor, 0 is a column vector containing K complex valued predictor coefficients and H represents a Hermitian transpose. A Wiener ....

[Article contains additional citation context not shown here]

T. Ekman, M. Sternad, and A. Ahln, "Unbiased Power Prediction on Broadband Channel," in Proc. IEEE Vehicular Technology Conference, Canada, Vancouver, Sept. 2002.

....complexity [5] Channel prediction over such horizons is difficult, and has only recently begun to be investigated. We have developed predictors that use channel tap estimates as regressors to predict the power of all significant channel taps. A recently developed unbiased quadratic predictor [10] provides the so far best performance, see Figure 2. We have also obtained a good theoretical understanding of the limits of attainable performance in different propagation environments. From extensive investigations on broadband measurement data, we have found that the received signal power can ....

....of attainable performance in different propagation environments. From extensive investigations on broadband measurement data, we have found that the received signal power can be predicted with reasonable accuracy for time intervals corresponding to a movement of up to half a carrier wavelength [9, 10]. Half a wavelength at 1900MHz would at vehicular speeds of about ## km h correspond to 5ms, or about 7 of our proposed 0.667ms slots. 0.2 0.4 0.6 0.8 Average power prediction perfomance Prediction range [wavelengths] NMSE Unbiased pred. Biased pred. Last samp. Average pred. ....

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T. Ekman, M. Sternad and A. Ahlen, "Unbiased power prediction on broadband channels," RVK02, Stockholm, June 2002.

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