System Performance of Transmit Diversity Methods and a Two Fixed-Beam System in WCDMA (original) (raw)
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Performance of Speech Services in WCDMA using Fixed-Beams and Transmit Diversity Systems
2005 IEEE 61st Vehicular Technology Conference, 2005
The system capacity of speech users in WCDMA system is investigated using a number of different downlink transmit modes. A single antenna sectorized system, a two fixed-beam antenna array, a closed-loop (mode I) and an open-loop space time transmit diversity methods are compared in a dynamic radio network simulator. Frequency selective and flat fading channels are considered. The results show that the diversity gain in flat fading channels is substantial. In frequency selective fading, the benefits of fixed-beam systems are encouraging, whereas the performance of transmit diversity methods (especially the openloop scheme) are rather unsatisfactory.
Joint beamforming and transmit diversity for wireless communications
2004 International Conference on Communications, Circuits and Systems (IEEE Cat. No.04EX914)
The current work develops an efficient scheme to be used for the downlink of a WCDMA network, using transmitter diversity and b eamforming. The performances of space-time transmit diversity (STTD) in combination with selective transmit diversity (STD), beamforming (BF) and beam sele ctive transmit diversity (BSTD) which is a composite scheme of STD and BF, have been studied at the system level using the capacity as performance index. Both fading and interference are jointly considered in the multipath propagation environment. The main constraint was the implementation problem. It considers the use of an array with eight antenna elements spaced half wavelength per 120 o sector to implement dynamically the several proposed techniques based on the environment. It was found that the comparison is strongly related to the availability of path diversity. The system capacity is maximized by the BF in the presence of multipath diversity and high multiple access interference. Otherwise it is the BSTD that achieves the best overall capacity performance. For higher data rates and small number of users the system that gives the best capacity performance is STTD+STD.
Capacity study for fixed multi beam antenna systems in a mixed service WCDMA system
Antenna arrays at the base stations allow capacity enhancement in cellular WCDMA networks. In this contribution we compare the relative downlink capacity between a system employing standard three sector site configurations with a system employing four fixed beam antenna systems. Since different packet services are expected to contribute largely to the traffic demand within a few years after initial deployment, this comparison is made in a mixed traffic environment. By realistic computer simulations it is found that a substantial gain can be expected by the introduction of adaptive (smart) antenna base stations. In this contribution a fixed multi beam system is considered, which is a fairly low complex adaptive antenna implementation. The simulations show that generally, a threefold capacity increase can be gained by employing a 4 beam antenna system. For some scenarios even higher gains can be achieved
Transmit diversity in the WCDMA system
1999
This document presents the transmit diversity concept adopted for the FDD mode of the thirdgeneration WCDMA system in ETSI in 1998. The open-loop mode is based on the space-time block code attaining full diversity order with two transmit antennas. Different feedback modes are speci® ed. They all utilize terminal measurements in controlling the transmit weighting in the transmit antennas. The concept is described in detail for two transmit antennas. It is shown that very limited feedback from the terminal to the base, as de® ned for the FDD mode, can increase downlink performance signi® cantly when compared to single-antenna transmission.
Transmit diversity schemes for WCDMA
Wireless Personal Communications, 2003
Previous work on transmitter antenna diversity has shown that the use of multiple transmitter antennas at the base station results in improved performance due to increase of diversity (path diversity). This happens with no bandwidth cost, even when the signal quality along several paths is poor, but the receiver estimates the channel with accuracy. This paper evaluates the effects of channel estimation errors in the performance of the schemes designated as Space-Time Transmitter Diversity (STTD) and Selective Transmitter Diversity (STD). We consider low to medium signal to noise ratios characteristic of Wideband Code Division Multiple Access (WCDMA) networks. Different fading channel models are considered for comparison between the two schemes. The improvement due to convolutional coding associated with these techniques is also evaluated.
This paper focuses on the use of antenna diversity technique in enhancing the performance of Wideband Code Division Multiple Access network. Several field measurements of received signal strength were obtained from a WCDMA network with the help of spectrum analyzer and global positioning system. In this paper also, the characterization of the propagation environment was done using the pathloss exponent and empirical pathloss model. Results show that the pathloss exponent of the field environment where the network is situated resulted in 3.63.The use of antenna diversity on the same network gave a pathloss exponent of 2.51.
On the Downlink Capacity of WCDMA Systems with Transmit Diversity
2005
Abstract—Transmitter diversity at the base station has been included in WCDMA standard for third generation mobile systems as a means of increasing the downlink system capacity. In previous works, it has been shown that open loop transmitter diversity can significantly increase the downlink capacity. However, the performance in multipath environment is not known. In our study, we present the simulation results for downlink system capacity taking into account the effect of Doppler frequency and multipath fading.
A Method for Designing Fixed Multibeam Antenna Arrays in WCDMA Systems
Antennas and Wireless Propagation Letters, 2000
In this paper, Simulated Annealing is used for designing a fixed multi-beam antenna array (AA) in a multi-user radio WCDMA system. The method can be used dynamically in a real system and/or in a radio planning tool. The proposed method is applied on a linear array by designing the Antenna Element (AE) pattern, the number of fixed beams, the AE spacing, and the AA transmit weights. The proposed method leads to a substantial BS power reduction which can be used to increase the system capacity or data throughput in a WCDMA system.
System performance of multibeam antennas HS-DSCH WCDMA system
2004 IEEE 15th International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE Cat. No.04TH8754), 2004
Fixed multi-beam base stations can significantly increase the capacity of WCDMA systems. Previous capacity studies have not included important Radio Network Algorithms (RNA) such as Admission Control (AC) which are essential to guarantee an acceptable Quality Of Service (QoS). Some of these RNA may have to be changed to secure the full gains of fixed multi-beam antennas. In this paper two downlink AC strategies, beam AC and cell AC, are investigated by means of dynamic system simulations. Beam AC takes the spatial dimension into account by considering the load in each beam, whereas cell AC does not. The performance of the two AC strategies is compared in different user scenarios for a fixed multi beam smart antenna concept. It is shown that beam AC ensures system stability and gives up to 30% more capacity than cell AC, when the traffic distribution is non uniform.
Fading Mitigation with Diversity Schemes in WCDMA : Technical Review
2015
Wide Code Division Multiple Access (WCDMA)a third generation wireless communication system that has high bandwidth and offers multimedia communication capabilities for global mobile communications but the performance of WCDMA is degraded with various factors such as interference, fading and scattering. Diversity is a technique which is used to mitigate the fading problem in wireless channel at a relatively low cost .This paper gives the review of different diversity techniques to mitigate the fading problem and for improving the overall performance of the communication system. In different diversity techniques, space diversity technique is an important technique and maximum ratio combining (MRC) is the most effective technique which is a part of space diversity technique.MRC produces an output signal to noise ratio (SNR) equal to the sum of the individual SNRs.