A suboptimal LQ power control algorithm for a CDMA wireless system
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abstract
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In today%27s wireless systems, power control is an important problem which is related to the Quality-of-Service (QoS) and battery utilization at the mobile units. This problem is studied in this work for the uplink of a direct-sequence codedivision multiple-access communication (DS-CDMA) system. By a proper selection of the error function, the resulting linear decoupled feedback loops can be controlled efficiently following a distributed power control approach, and these closed-loops are independent of the user%27s channel variations. A suboptimal LQ strategy is suggested and derived for power update. This control law has a variable structure that depends on the transmission roundtrip delay in the feedback system, which is a key parameter to establish closed-loop stability. It is demonstrated that in the limit of some synthesis parameters, the LQ-controller tends to a Dead-Beat response, improving the time response but sacrificing robustness. Meanwhile, the LQ-controller can be adjusted to increase its robustness. Simulation results are presented to compare the control algorithms using a standard single-step power correction approach. © 2008 IEEE.
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In today's wireless systems, power control is an important problem which is related to the Quality-of-Service (QoS) and battery utilization at the mobile units. This problem is studied in this work for the uplink of a direct-sequence codedivision multiple-access communication (DS-CDMA) system. By a proper selection of the error function, the resulting linear decoupled feedback loops can be controlled efficiently following a distributed power control approach, and these closed-loops are independent of the user's channel variations. A suboptimal LQ strategy is suggested and derived for power update. This control law has a variable structure that depends on the transmission roundtrip delay in the feedback system, which is a key parameter to establish closed-loop stability. It is demonstrated that in the limit of some synthesis parameters, the LQ-controller tends to a Dead-Beat response, improving the time response but sacrificing robustness. Meanwhile, the LQ-controller can be adjusted to increase its robustness. Simulation results are presented to compare the control algorithms using a standard single-step power correction approach. © 2008 IEEE.
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Research
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Code division multiple access; Controllers; Feedback; Quality control; Quality of service; Robustness (control systems); Channel variations; Closed loop stability; Correction approaches; Distributed power control; Feedback systems; Synthesis parameters; Variable structures; Wireless systems; Power control
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