Directional Diversity of Smart Antenna in LAS CDMA Systems (original) (raw)
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Performance of LAS-CDMA System using Smart Antenna
2005 13th IEEE International Conference on Networks Jointly held with the 2005 IEEE 7th Malaysia International Conf on Communic, 2005
The choice of CDMA spreading sequences predetermines the properties of the system. The properties of large area synchronous (LAS) CDMA system have been demonstrated an interference free window (IFW) compared to traditional CDMA systems. This IFW property, however, has a limited delay-offset range. It is not always possible that all the channel-induced multipath delay spread components will arrive within IFW delay-offset range if the conventional antenna is employed. In this paper, the high directive narrow beam of smart antenna system is employed to direct all the multipath propagation components to arrive within the IFW range. Moreover, smart antenna system with its mathematical model is described. The reduction of multipath propagation in smart antenna system is also described. Finally, system performance analysis in terms of BER and maximum delay spread in both conventional and smart antennas are presented.
IMPROVED PERFORMANCE OF MC-CDMA USING SMART ANTENNA TECHNIQUE
TJPRC, 2014
To improve coverage and performance in the MC-CDMA network with the help of simulation model and an evaluation method for the smart antenna system is presented. The proposed method that can show the impact o f smart antenna system on the Ec/Io coverage area is also presented as function of antenna type and beam width. The performance improvements are remarkable in the smart antenna systems. Here the data service users as well as the voice services users are considered. The performance of the system is evaluated in terms of Ec/Io Difference. We can observe the throughput with Number of users per sector. Results are discussed based on various parameters like flat urban type morphology, Okumura Model for omni direct ional antennas air link, orthogonality factor and antenna beam width. It also reduces multipath fading, cochannel interferences, system complexity &cost, BER, and outage probability.
Smart Antennas for Multiuser DS/CDMA Communications in Multipath Fading Channels
IEICE Transactions on Communications, 2005
Smart antennas, with spatial processing, used in code division multiple access (CDMA) multiuser communications can enhance range, reliability and capacity. Moreover, the adaptive beamforming technologies can remove unwanted noise and jamming from the received signal. In this paper, we use least mean square algorithm and propose four adaptive antenna receiver structures for directsequence (DS) CDMA multiuser environment with multipath fading channels. Narrowband and wideband adaptive array receiver structures are considered in this paper. LMS algorithms are employed in both narrowband and wideband receiver structures to adjust the spreading code coe cients. We call these new schemes as Wiener code filters. The weights of the adaptive beamformer and the spreading code are updated every bit interval, so the computational complexity is very low. Simulation examples are given to compare the performances of the proposed receiver structures.
Performance Analysis of DS-Cdma System Over Awgn and Fading Channels Based on Diversity Scheme
2013
This paper investigates, a technique which uses antenna diversity to achieve full transmit diversity using an arbitrary number of transmit antennas for secure communications and to improve the system performance by mitigating interference. The work is focused on the performance of DS-CDMA systems over Rayleigh, Rician and AWGN fading channel, in the case of the channel being known at the receiver .The diversity scheme used in the analysis is Alamouti STBC scheme. Using simulation and analytical approach, we show that STBC CDMA system has increased performance in cellular networks We also compare the performance of this system with the typical DS-CDMA system and show that STBC and multiple transmit antennas for DSCDMA system provide performance gain without any need of extra processing . Evaluation and comparison of the performances of DS-CDMA system in the AWGN (Additive White Gaussian Noise) channel, Rician fading channel and the Rayleigh fading channel are provided.
Spectrum Efficiency Enhancement in Dynamic Space Coded Multiple Access (DSCMA) System
Wireless Personal Communications, 2010
In cellular mobile communication systems using coded modulations, the spectrum efficiency of the system is related to the number of available codes. Recently, large area synchronous (LAS) CDMA codes, which exhibit a region called interference free window (IFW) within some delay-spread, have been accepted as one of fourth-generation (4G) wireless communication systems. However, the number of synthesized LAS codes is very low due to the low duty ratio of the sequence. In this paper, a dynamic space coded multiple access (DSCMA) scheme which utilizes the spatial diversity from smart antenna system is proposed to overcome the low spectrum efficiency in LAS CDMA system. In the DSCMA a modified version of LAS codes called LAS even ternary (LAS-ET) codes is proposed. These codes are used together with a novel algorithm called dynamic space code (DSC), which will decrease the code length so that the spectrum efficiency can be increased. By taking advantage of dynamic code reuse assignment in spatial diversity, the spectrum efficiency of the DSCMA can be further increased significantly.
Performance of the smart antenna aided multicarrier DS-CDMA uplink
IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004, 2004
In this contribution a generalized MC DS-CDMA system invoking smart antennas for improving the achievable performance of the system is studied, which is capable of suppressing the multiuser interference, while achieving frequency, time and spatial diversity. In the considered MC DS-CDMA system the receiver employs multiple receive antennas and each of the receive antennas consists of several antenna array elements. Four types of optimum linear combining schemes are investigated. In these optimum linear combining schemes the weight vectors are derived based on the optimization criteria of Minimum Variance Distortionless Response (MVDR), of Maximum Signalto-Interference-plus-Noise Ratio (MSINR), of Minimum Mean-Square Error (MMSE) and of Minimum Power Distortionless Response (MPDR). The paper is concluded with a comparative performance study of various antenna array models employing the above optimization criteria.
Smart antenna system for wideband CDMA signals
Smart antennas have been succesfully implemented in CDMA cellular communication systems in order to increase the system capacity and improve its performance. However, it has been shown in [I] that the use of wideband CDMA signals results in a significant deterioration of the narrowband system performance. The use of adaptive array to reject wideband interferences and track wideband signals have been proven to be more efficient if frequency compensation is used [2]. This paper presents an extension of the interpolated constant modulus algorithm (ICMA) introduced in [2] to wideband CDMA signals (WCDMA). Simulation results show that the ICMA yields significantly better performance as compared to the coventional narrow-band adaptive algorithm.
2016
We propose to upgrade the performance of a class of random access protocols for wireless digital networks with smart antennas operating in the presence of Rayleigh slowly fading multipath transmission channels. The capture model assumed is a threshold model based on the signal to noise ratio, while the MAC protocol deployed isthe two-cell random access algorithm, in a network environment where nodesare equipped with adaptive array smart antennas. The deployed protocol relies on the ability of the antenna to deploy Direction of Arrival (DoA) algorithms, to identify the direction of transmitters and to subsequently beam-form accordingly for Signalto Interference and Noise Ratio (SINR) maximization. The performance of the protocol is evaluated using analytical modeling as well as Monte Carlo simulations usingMATLAB, where we demonstrate the benefits of using smart antennas.