TAILIEUCHUNG - Adaptive WCDMA (P6)

Power control ALGORITHMS In Chapter 8, we will show that the Code Division Multiple Access (CDMA) network capacity depends significantly on the so-called near–far effect. From the very beginning, theory and practice of CDMA were aware of this fact. All practical systems use Power control (PC) to reduce this effect. PC is more efficient in the system optimized for speech, such as IS-95. In a multimedia network such as Universal Mobile Telecommunication System (UMTS) in which different signals levels are used for different data rates, additional solutions like multiuser detectors are used. In IS-95, every mobile station attempts to adjust its. | Adaptive WCDMA Theory And Practice. Savo G. Glisic Copyright 2003 John Wiley Sons Ltd. ISBN 0-470-84825-1 6 Power control ALGORITHMS In Chapter 8 we will show that the Code Division Multiple Access CDMA network capacity depends significantly on the so-called near-far effect. From the very beginning theory and practice of CDMA were aware of this fact. All practical systems use Power control PC to reduce this effect. PC is more efficient in the system optimized for speech such as IS-95. In a multimedia network such as Universal Mobile Telecommunication System UMTS in which different signals levels are used for different data rates additional solutions like multiuser detectors are used. In IS-95 every mobile station attempts to adjust its transmission power so that signals received at a base station are at the same minimum level at which good quality communication can still be provided. Both the closed and open loop methods are used. The closed-loop includes two different loops that is a relatively fast inner and a slow outer loop. In addition to the data signals every base station transmits a so-called pilot signal which is an unmodulated signal 1 used at the mobile stations for PC synchronization and demodulation as a power level phase frequency and time reference. In the open loop method a mobile station measures the average received total power and adjusts its transmission power to be inversely proportional to the received power. In the initial phase of the call the average received pilot signal power is measured. The open loop algorithm is presented in Reference 2 . The mobile station transmission power is a certain constant divided by the received total power. The constant value used depends on several base station parameters such as antenna gain the number of active users transmission power required signal-to-interference ratio SIR and interference caused by other base stations. The base station informs the mobile stations before transmission about the .

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