Improved Predictive Power Control Algorithms to Increase CDMA System Capacity (original) (raw)
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Improved Predictive Power Control of Cdma System in Rayleigh Fading Channel
MAKARA of Technology Series, 2010
In this paper an improved prediction-based power control is proposed for code division multiple access (CDMA) systems in Rayleigh fading channel environments. One of the most serious problems which degrades the performance of power control algorithm is the effect of feedback delay. To overcome the effect of feedback delay, power control needs to employ prediction algorithm which utilises the correlation property of the past channel samples measurements to predict the future sample values. In CDMA power control, however, the correlation property of channel measurements is destroyed because the transmit power is continuously updated for each power control interval. The prediction algorithm in this paper uses the recursive least square (RLS) technique and an improved predictor algorithm is proposed to compensate for the channel correlation. The result shows that the performance of improved predictive power control proposed in this paper evaluated in terms of bit error rate (BER) as a function of bit energy-tointerference power density ratio E b /I o improved significantly from that of the conventional predictor.
A New Power Control Algorithm for Cellular CDMA Systems
2009
The conventional closed-loop power control in cellular code division multiple access systems can only achieve limited performance due to its inability to track channel variations quickly. In this paper, we present a new power control algorithm which is able to increase the speed of convergence to track the changes in radio channel efficiently. Simulation results show that it outperforms the conventional algorithms.
Performance Analysis of Downlink Power Control in CDMA Systems
IEEE Sarnoff Symposium, Princeton, 2003
Three downlink power control algorithms have been studied and evaluated in this work. Additionally, an uplink power control algorithm has been modified and adapted for downlink. An enhancement has been proposed to one of the studied algorithms based on the ...
Variable Step Closed-Loop Power Control in Cellular Wireless CDMA Systems under Multipath Fading
2007 IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, 2007
The Power control has been widely studied and shown to be crucial for the capacity and performance of directsequence code-division multiple-access (DS-CDMA) systems. Practical implementations typically employ fast closed-loop power control, where transmitters adjust their transmit powers according to commands received in a feedback channel. The loop delay resulting from the measurements, processing, and transmission of the power control commands can result in oscillations of the transmission powers and lead to degradation in the system performance. In this paper We present new variable step closed-loop power control algorithm (VSPC) and fixed-step closed loop power control with information feedback (FSPC-IF), that are able to increase speed of convergence and alleviate the effect of the loop delay. We carried out computational experiments on a DS-CDMA network using these algorithms. Fixed-step power control with decision feedback (FSPC-DF) is reference algorithm. New algorithms are compared with it. The numerical results indicate that new algorithms can significantly improve the radio network capacity without any increase in power control signaling, also increase speed of convergence and decrease loop delay.
New Approach to Closed-Loop Power Control in Cellular CDMA Systems under Multipath Fading
2008 4th International Conference on Wireless Communications, Networking and Mobile Computing, 2008
This paper proposes a new approach to the closed-loop power control algorithm with decision feedback, called NAPC-DF algorithm. In this algorithm, the step size of the transmitting power by the mobile station (MS) in uplink channel is variable and adjusted by the received command from the base station (BS) and channel conditions. This algorithm is compared with fixed-step, variable step and adaptive step closed-loop power control with decision feedback (FSPC-DF, VSPC-DF and ASPC-DF, respectively). Numerical results indicate that NAPC-DF algorithm, under fading can significantly improve the radio network capacity without any increase in power control signaling. Also the speed of convergence and stability against loop delay can be increased and it decreases the outage probability and bit error rate (BER) of uplink channel in compared with the mentioned references algorithms.
Enhanced Predictive Up/Down Power Control for CDMA Systems
2006 IEEE International Conference on Communications, 2006
In this paper we derive an enhanced power control algorithm, fitting into the up/down control scheme, as it is considered in the frequency division duplex (FDD) mode of the current 3GPP standard. Analysis of the classical up/down power control scheme unveils, that with increasing velocities the power control performance degrades, as the fixed step size power control is not able
arXiv preprint arXiv:1109.1643, 2011
Abstract: In Fixed Wireless Applications (FWA), the Code Division Multiple Access (CDMA) is the most promising candidate for wideband data access. The reason is the soft limit on the number of active mobile devices. Many Fixed Wireless Applications impose an upper bound on the BER performance which restricts the increase in number of mobile users. The number of active mobile users or Capacity is further reduced in Multipath Fading Environment (MFE). This paper presents an effective method of improving the capacity of CDMA based Fixed ...
researchpaper Modified Variable Step Size Power Control Algorithm for CDMA Systems
Power control mechanism is an important issue for Code Division Multiple Access (CDMA) systems which helps in achieving higher capacity, combating against near far effect and provides high link performance. Unless a suitable power control mechanism is developed cellular systems cannot perform better. Power control allows to minimize the transmit power while keeping the system performance above the required value. In previous research [4], variable step size for closed loop power control system has been studied and results showed an increase in convergence speed and stability by properly choosing the step size. The new algorithm presented in this paper shows that it can perform better than variable step size power control algorithm and can obtain higher stability and convergence speed for step size δ at 0.1.