Predictive Closed-loop Power Control Research Articles

Predictive Closed-Loop Power Control for Delay-Prone Burst Transmission Systems in Rayleigh Fading

We present a predictive closed-loop power control scheme for delay-prone burst transmission systems. The scheme has a sample-by-sample predictor compensating burst delay and a built-in channel encoder reducing power control command bit error.

Predictive Closed-Loop Power Control for CDMA Cellular Networks

In this paper, we present and analyze a predictive closedloop power control (CLPC) scheme which employs a comb-type sample arrangement to effectively compensate multiple power control group (PCG) delays over mobile fading channels. We consider both least squares and recursive least squares filters in our CLPC scheme. The effects of channel estimation error, prediction filter error, and power control bit transmission error on the performance of the proposed CLPC method along with competing non-predictive and predictive CLPC schemes are thoroughly investigated. Our results clearly indicate the superiority of the proposed scheme with its improved robustness under non-ideal conditions. Furthermore, we carry out a Monte-Carlo simulation study of a 5×5 square grid cellular network and evaluate the user capacity. Capacity improvements up to 90% are observed for a typical cellular network scenario.

Predictive closed-loop power control scheme with comb-type sample arrangement for code division multiple access cellular networks

The authors present and analyse a predictive closed-loop power control (CLPC) scheme, which employs a comb-type sample arrangement to effectively compensate multiple power control group delays over mobile fading channels. The authors consider both least squares and recursive least squares filters in our CLPC scheme. The effects of channel estimation error, prediction filter error and power control bit transmission error on the performance of the proposed CLPC method along with competing non-predictive and predictive CLPC schemes are thoroughly investigated. The results clearly indicate the superiority of the proposed scheme with its improved robustness under non-ideal conditions. Furthermore, the authors carry out a Monte-Carlo simulation study of a 5×5 square grid cellular network and evaluate the user capacity. Capacity improvements up to 90% are observed for a typical cellular network scenario.

Predictability of Uplink Channels From Downlink Channels in Frequency Division Duplex Systems: A Power Control Application

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.

Filter-shaped LMS algorithm-based predictive power control

A predictive closed-loop power control scheme based on a filter-shaped least-mean-square (FS-LMS) algorithm, which takes into account knowledge of the fading process time-evolution, is proposed. It is demonstrated through simulation, that an FS-LMS-based closed-loop power control scheme performs better than the standard LMS algorithm.

Achievable-SIR-based predictive closed-loop power control in a CDMA mobile system

A power control algorithm with two prediction models based on an achievable signal-to-interference power ratio (SIR) has been proposed under a multipath Rayleigh fading environment in a code-division multiple-access (CDMA) mobile system. An achievable SIR is defined as the maximum-minimum SIR among all users at a particular time step. The corresponding mobile transmission powers are denoted as the "optimum transmission powers." In the individual power predictor (IPP) model, a linear transversal filter is assigned to each user. The output of the IPP, which is a linear combination of the optimum transmission powers of the mobile during the current and previous power measurement periods, predicts the optimum transmission power of the mobile in the next time step. In the global power predictor (GPP) model, a single predictor, constructed by a linear neural network, is used to predict the optimum transmission powers of all mobiles in the next time step. In both predictor models, the weights of the predictors are updated by using the recursive least squares algorithm. To further improve the performance, a reduced power-measurement period has been studied. Simulation results show that the proposed power control algorithm can achieve a lower outage probability and a smaller dynamic range of transmission power compared with a conventional power control scheme.

Predictive closed-loop power control for frequency-division duplex wireless systems

A novel method for performing uplink closed-loop power control is proposed, namely with uplink prediction and downlink-derived predictor coefficients. The lack of correlation between the fading processes on uplink and downlink (due to frequency division duplex and frequency selective fading) is circumvented by using the uplink fading history, together with a set of link-independent, autoregressive coefficients.

Predictive closed-loop power control in CDMA mobilesystems

An achievable-SIR-based closed-loop power control scheme is proposed to maximise the minimum signal-to-interference power ratio (SIR). The proposed scheme is found to reduce the outage probability and also the dynamic range of the transmission power compared with the conventional power control scheme.