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Improved Iterative Parallel Interference Cancellation Receiver for Future Wireless DS-CDMA Systems  [cached]
Simone Morosi,Romano Fantacci,Andrea Bernacchioni
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.626
Abstract: We present a new turbo multiuser detector for turbo-coded direct sequence code division multiple access (DS-CDMA) systems. The proposed detector is based on the utilization of a parallel interference cancellation (PIC) and a bank of turbo decoders. The PIC is broken up in order to perform interference cancellation after each constituent decoder of the turbo decoding scheme. Moreover, in the paper we propose a new enhanced algorithm that provides a more accurate estimation of the signal-to-noise-plus-interference-ratio used in the tentative decision device and in the MAP decoding algorithm. The performance of the proposed receiver is evaluated by means of computer simulations for medium to very high system loads, in AWGN and multipath fading channel, and compared to recently proposed interference cancellation-based iterative MUD, by taking into account the number of iterations and the complexity involved. We will see that the proposed receiver outperforms the others especially for highly loaded systems.
Blind Adaptive Successive Interference Cancellation for Multicarrier DS-CDMA  [PDF]
Indu Shakya,Falah H. Ali,Elias Stipidis
Mathematics , 2011,
Abstract: A new adaptive receiver design for the Multicarrier (MC) DS-CDMA is proposed employing successive interference cancellation (SIC) architecture. One of the main problems limiting the performance of SIC in MC DS-CDMA is the imperfect estimation of multiple access interference (MAI), and hence, the limited frequency diversity gain achieved in multipath fading channels. In this paper, we design a blind adaptive SIC with new multiple access interference suppression capability implemented within despreading process to improve both detection and cancellation processes. Furthermore, dynamic scaling factors derived from the despreader weights are used for interference cancellation process. This method applied on each subcarrier is followed by maximum ratio or equal gain combining to fully exploit the frequency diversity inherent in the multicarrier CDMA systems. It is shown that this way of MAI estimation on individual subcarrier provides significantly improved performance for a MC DS-CDMA system compared to that with conventional matched filter (MF) and SIC techniques at a little added complexity. Performance evaluation under severe nearfar, fading correlation and system loading conditions are carried out to affirm the gain of the proposed adaptive receiver design approach.
A Robust Adaptive MMSE Rake Receiver for DS-CDMA System in a Fast Multipath Fading Channel
K. Jeong,M. Yokoyama,H. Uehara
Radioengineering , 2006,
Abstract: In this paper, we propose a robust adaptive minimum mean square error (MMSE) Rake receiver for asynchronous DS-CDMA systems. The receiver uses the modified MMSE criterion that incorporates the differential detection and the amplitude compensation for interference cancellation in a time-varying multipath fading channel. We investigate that the proposed Rake receiver can achieve the higher output signal to interference plus noise ratio (SINR) than the conventional adaptive Rake receiver, since the modified MMSE criterion does not attempt to track the time-varying MMSE solution. Computer simulations verify that the performance of the proposed Rake receiver is better than those of the conventional and the adaptive Rake receiver.
REVIEW ON DS SS-CDMA TRANSMITTER AND RECEIVER FOR AD HOC NETWORK USING VHDL IMPLEMENTATION
Bramha Swaroop Tripathi,Monika Kapoor
International Journal of Advances in Engineering and Technology , 2013,
Abstract: In telecommunications, direct-sequence spread spectrum (DSSS) is a modulation technique. As with other spread spectrum technologies, the transmitted signal takes up more bandwidth than the information signal that modulates the carrier or broadcast frequency. DS-CDMA is advantageous for ad hoc networks because it eliminates the need for any frequency or time-slot coordination, directly benefits from inactive terminals in the network. Ad-hoc network is a decentralized type of wireless network. The network is ad hoc because it does not rely on a pre-existing infrastructure, such as routers in wired networks or access points in managed wireless network. This paper investigates the benefit of Medium access Protocol based on direct-sequence code-division multiple-access (DS/CDMA) Ad-hoc network. This article give a review of MAC protocol that have been proposed for Direct sequence spread spectrum code Division Multiple Access(DS-SS CDMA) for ad-hoc network using VHDL implementation. We first describe the problem of DS CDMA used for ad-hoc network, and then describe the How to remove problem of DS CDMA using our proposed protocol.The main issue in DS-CDMA ad hoc networks is the prevention of a near-far problem in packet communication and low throughput, collision & cross correlation. We know that the two solutions to reduce the near far effect are power control and medium access. So we are focusing the medium access problem and we are designing multiple access interference (MAI) at the protocol level using VHDL implementation. Our Goal is to Using VHDL Implementation for design a DS SS CDMA-based Transmitter with MAC protocol & receiver for ad-hoc network that increases the throughput and avoided the collision & cross correlation, and improve overall performance in ad- hoc network.
Performance of Turbo Interference Cancellation Receivers in Space-Time Block Coded DS-CDMA Systems  [cached]
Mashwama DerrickB,Bejide EmmanuelOluremi
EURASIP Journal on Wireless Communications and Networking , 2008,
Abstract: We investigate the performance of turbo interference cancellation receivers in the space time block coded (STBC) direct-sequence code division multiple access (DS-CDMA) system. Depending on the concatenation scheme used, we divide these receivers into the partitioned approach (PA) and the iterative approach (IA) receivers. The performance of both the PA and IA receivers is evaluated in Rayleigh fading channels for the uplink scenario. Numerical results show that the MMSE front-end turbo space-time iterative approach receiver (IA) effectively combats the mixture of MAI and intersymbol interference (ISI). To further investigate the possible achievable data rates in the turbo interference cancellation receivers, we introduce the puncturing of the turbo code through the use of rate compatible punctured turbo codes (RCPTCs). Simulation results suggest that combining interference cancellation, turbo decoding, STBC, and RCPTC can significantly improve the achievable data rates for a synchronous DS-CDMA system for the uplink in Rayleigh flat fading channels.
Iterative Soft Decision Interference Cancellation for DS-CDMA Employing the Distribution of Interference  [cached]
Jürgen F. Rößler,Wolfgang H. Gerstacker,Johannes B. Huber
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/214393
Abstract: A well-known receiver strategy for direct-sequence code-division multiple-access (DS-CDMA) transmission is iterative soft decision interference cancellation. For calculation of soft estimates used for cancellation, the distribution of residual interference is commonly assumed to be Gaussian. In this paper, we analyze matched filter-based iterative soft decision interference cancellation (MF ISDIC) when utilizing an approximation of the actual probability density function (pdf) of residual interference. In addition, a hybrid scheme is proposed, which reduces computational complexity by considering the strongest residual interferers according to their pdf while the Gaussian assumption is applied to the weak residual interferers. It turns out that the bit error ratio decreases already noticeably when only a small number of residual interferers is regarded according to their pdf. For the considered DS-CDMA transmission the bit error ratio decreases by 80% for high signal-to-noise ratios when modeling all residual interferers but the strongest three to be Gaussian distributed.
Iterative Soft Decision Interference Cancellation for DS-CDMA Employing the Distribution of Interference  [cached]
R??ler JürgenF,Gerstacker WolfgangH,Huber JohannesB
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract: A well-known receiver strategy for direct-sequence code-division multiple-access (DS-CDMA) transmission is iterative soft decision interference cancellation. For calculation of soft estimates used for cancellation, the distribution of residual interference is commonly assumed to be Gaussian. In this paper, we analyze matched filter-based iterative soft decision interference cancellation (MF ISDIC) when utilizing an approximation of the actual probability density function (pdf) of residual interference. In addition, a hybrid scheme is proposed, which reduces computational complexity by considering the strongest residual interferers according to their pdf while the Gaussian assumption is applied to the weak residual interferers. It turns out that the bit error ratio decreases already noticeably when only a small number of residual interferers is regarded according to their pdf. For the considered DS-CDMA transmission the bit error ratio decreases by 80% for high signal-to-noise ratios when modeling all residual interferers but the strongest three to be Gaussian distributed.
Performance of Turbo Interference Cancellation Receivers in Space-Time Block Coded DS-CDMA Systems  [cached]
Derrick B. Mashwama,Emmanuel Oluremi Bejide
EURASIP Journal on Wireless Communications and Networking , 2008, DOI: 10.1155/2008/473796
Abstract: We investigate the performance of turbo interference cancellation receivers in the space time block coded (STBC) direct-sequence code division multiple access (DS-CDMA) system. Depending on the concatenation scheme used, we divide these receivers into the partitioned approach (PA) and the iterative approach (IA) receivers. The performance of both the PA and IA receivers is evaluated in Rayleigh fading channels for the uplink scenario. Numerical results show that the MMSE front-end turbo space-time iterative approach receiver (IA) effectively combats the mixture of MAI and intersymbol interference (ISI). To further investigate the possible achievable data rates in the turbo interference cancellation receivers, we introduce the puncturing of the turbo code through the use of rate compatible punctured turbo codes (RCPTCs). Simulation results suggest that combining interference cancellation, turbo decoding, STBC, and RCPTC can significantly improve the achievable data rates for a synchronous DS-CDMA system for the uplink in Rayleigh flat fading channels.
Research of optimal detection order in DS-CDMA systems with nonlinear successive interference cancellation
采用非线性串行干扰消除的DS-CDMA系统中最优检测顺序的研究*

ZHOU Zhao-rong,LI Le-min,ZHANG Yi-de,FENG Gang,
周朝荣
,李乐民,张翼德,冯钢

计算机应用研究 , 2009,
Abstract: In DS-CDMA systems with successive interference cancellation(SIC),different detection orders result in different system performance.This paper studied how to adjust the detection order to minimize the total transmission power in this kind of systems.Unlike existing work,considered the receiver of imperfect nonlinear SIC and supposed that the other cell interference was no longer independent of users' transmission(received) power.Under these presuppositions,derived the optimal detection order to minimize the...
Successive Interference Cancellation for DS-CDMA Systems with Transmit Diversity  [cached]
Li Wei,Gulliver T Aaron
EURASIP Journal on Wireless Communications and Networking , 2004,
Abstract: We introduce a new successive interference cancellation (SIC) technique for direct sequence code division multiple access (DS-CDMA) systems with transmit diversity. The transmit diversity is achieved with a space-time block code (STBC). In our work we first consider hard decision SIC with an STBC, and then investigate the performance of soft decision SIC with an STBC. System performance over a Rayleigh fading channel is investigated and the analysis is confirmed by simulation.
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