Speed and Accuracy Comparison of Techniques for Multiuser Detection in Synchronous CDMA

Hasegawa, Fumihiro; Luo, Jie; Pattipati, Krishna R.; Willett, Peter; Pham, Duc-Son

doi:10.1109/tcomm.2004.826410

Cited by 32 publications

(24 citation statements)

References 27 publications

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“…Note that, the variables in the optimization problem in (6) are the bits to be estimated. This optimization problem can be rewritten as an equivalent minimization problem…”

Section: Cdma Channel Modelsmentioning

confidence: 99%

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A Low-Complexity High-Performance Preprocessing Algorithm for Multiuser Detection Using Gold Sequences

Axehill

Gunnarsson

Hansson

2008

IEEE Trans. Signal Process.

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The optimum multiuser detection problem can be formulated as a maximum likelihood problem, which yields a binary quadratic programming problem to be solved. Generally this problem is NP-hard and is therefore hard to solve in real-time. In this article, a preprocessing algorithm is presented which makes it possible to detect some or all users optimally for a low computational cost if signature sequences with low cross-correlation, e.g., Gold sequences, are used. The algorithm can be interpreted as, e.g., an adaptive trade-off between parallel interference cancellation and successive interference cancellation. Simulations show that the preprocessing algorithm is able to optimally compute more than 94 % of the bits in the problem when the users are time-synchronous, even though the system is heavily loaded and affected by noise. Any remaining bits, not computed by the preprocessing algorithm, can either be computed by a suboptimal detector or an optimal detector. Simulations of the time-synchronous case show that if a suboptimal detector is chosen, the BER rate is significantly reduced compared to using the suboptimal detector alone. Abstract-The optimum multiuser detection problem can be formulated as a maximum likelihood problem, which yields a binary quadratic programming problem to be solved. Generally this problem is NP-hard and is therefore hard to solve in real-time. In this article, a preprocessing algorithm is presented which makes it possible to detect some or all users optimally for a low computational cost if signature sequences with low cross-correlation, e.g., Gold sequences, are used. The algorithm can be interpreted as, e.g., an adaptive trade-off between parallel interference cancellation and successive interference cancellation. Simulations show that the preprocessing algorithm is able to optimally compute more than 94 % of the bits in the problem when the users are time-synchronous, even though the system is heavily loaded and affected by noise. Any remaining bits, not computed by the preprocessing algorithm, can either be computed by a suboptimal detector or an optimal detector. Simulations of the time-synchronous case show that if a suboptimal detector is chosen, the BER rate is significantly reduced compared to using the suboptimal detector alone.

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“…Note that, the variables in the optimization problem in (6) are the bits to be estimated. This optimization problem can be rewritten as an equivalent minimization problem…”

Section: Cdma Channel Modelsmentioning

confidence: 99%

“…Thorough work in the field of approximate algorithms for multiuser detection is found in [1]. Several different algorithms, optimal as well as suboptimal, are presented and evaluated in [6]. The suboptimal algorithm local search is evaluated in [7].…”

Section: Introductionmentioning

confidence: 99%

A Low-Complexity High-Performance Preprocessing Algorithm for Multiuser Detection Using Gold Sequences

Axehill

Gunnarsson

Hansson

2008

IEEE Trans. Signal Process.

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“…In recent days, the multiuser interference is treated as a part of the information rather than noise in joint multiuser detection [8] [9]. For multiuser detection, preceding research has focused on designing suboptimal receivers in synchronous CDMA model with low computational complexity and provides a better performance than a linear detector [5]. In many multiuser communication systems, multiuser detection for the symbolsynchronous Gaussian CDMA channel has established significant consideration over the past 15 years due to the problem of multiple-access interference (MAI) [6] [10].…”

Section: Introductionmentioning

confidence: 99%

Non Iterative Algorithm for Multi-user Detection in DS-CDMA System: An Enhanced Harmony Search Algorithm

Nemade¹,

Kolte²

2013

IJCA

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In this paper, a non iterative algorithm for MUD in DS-CDMA system is proposed. The proposed multiuser algorithm is performed based on harmony search algorithm. In the proposed algorithm, a new harmony memory updating is based on the random and mean operation. So, the proposed harmony search algorithm is reduced the complexity and the user information interference. Hence, the bit error rate of the transmitted code reduced. In the enhanced harmony search algorithm, the marginal distribution for each observed and unobserved node are calculated. The proposed multiuser detection algorithm is applicable in run time user identification process, so the MUD complexity and the required time are concentrated. Also, the iteration can be predefined based on the number of users, signal interference and signal to noise ratio. This improves the multiuser efficiency, reduce the information losses and power corruption in CDMA channel. The proposed technique is implemented in MATLAB and the performance is evaluated. KeywordsDS-CDMA system, multiuser detection, enhanced harmony search algorithm, bit error rate. INTRODUCTIONIn Digital cellular radio systems, the allocated bandwidth and radio cell infrastructure can be made capable with minimum cost and maximum performance by incorporating multiple access schemes [3]. The multiple access schemes are Code Division Multiple Access (CDMA) and Multi-Carrier Code Division Multiple Access (MC-CDMA). CDMA is an efficient method of bandwidth allocation and is used in many to one wireless communication channels [2] [18]. In MC-CDMA, higher system capacity is hypothetically promised by passing on multiple CDMA spreading signatures to each user at the transmitters and by applying sophisticated multiuser detection (MUD) schemes at the receivers and innate frequency diversity of wideband channels is well subjugated by scattering each symbol across multiple sub carriers [19]. Unique signature waveform is assigned for each user, which are used to modulate their information bits in CDMA [4]. For digital communication it is a spread spectrum modulation technique and for military applications it is used either to provide resistance to hostile jamming, or to hide the signal by transmitting it at low power [9]. In both the uplink and the downlink of CDMA systems power control of the transmitters is used for power allocation and interference management [20].In today's wireless communication CDMA is a core technology, it employs data transmission between multiple terminals and a single base station [11]. For future high-rate mobile communication systems, CDMA technique has great prospective for serving as the air-interface [12] which has the challenge of accepting many users in a small area. In recent days, the multiuser interference is treated as a part of the information rather than noise in joint multiuser detection [8] [9]. For multiuser detection, preceding research has focused on designing suboptimal receivers in synchronous CDMA model with low computational complexity and provides a better...

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“…In general, the suboptimum MUDs towards the optimum MUD problems can be divided into two classes. The first class aim at designing efficient search or non-search algorithms, such as those summarized in [4] and [5], in order to find approximate solutions for the optimum MUDs. Despite significant complexity reduction, however, these suboptimum algorithms either are still too complex to be implemented or achieve much worse BER performance than the optimum MUDs [5].…”

Section: Introductionmentioning

confidence: 99%

“…The first class aim at designing efficient search or non-search algorithms, such as those summarized in [4] and [5], in order to find approximate solutions for the optimum MUDs. Despite significant complexity reduction, however, these suboptimum algorithms either are still too complex to be implemented or achieve much worse BER performance than the optimum MUDs [5].The second class of suboptimum MUDs do not solve directly the optimum MUD problems. Instead, they approximate the optimum MUD problems by some suboptimum MUD problems that can be solved with lower complexity.…”

mentioning

confidence: 99%

Receiver Multiuser Diversity Aided Multi-Stage MMSE Multiuser Detection: A Low-Complexity Detector Fast-Converging to the Optimum

Yang

2010

2010 IEEE 71st Vehicular Technology Conference

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Abstract-Design of low-complexity detection schemes that can approach near-optimum bit error rate (BER) performance in multiuser or other multiple-input multiple-output (MIMO) systems has always been highly challenging. In this paper we propose and investigate a so-called receiver multiuser diversity aided multi-stage minimum mean-square error multiuser detection (RMD/MS-MMSE MUD) scheme operated in the principles of successive interference cancellation (SIC). The BER performance of the RMD/MS-MMSE MUD is investigated in association with both the direct-sequence code-division multiple-access (DS-CDMA) communicating over both Gaussian and Rayleigh fading channels, and the spacedivision multiple-access (SDMA) communicating over Rayleigh fading channels. Furthermore, we assume that the DS-CDMA and SDMA systems are either full-load or overload. Our studies show that the RMD/MS-MMSE MUD in full-load cases is capable of converging to the optimum BER performance of the maximum likelihood (ML) multiuser detector (MUD). For the overload systems, the RMD/MS-MMSE MUD can make a DS-CDMA or SDMA system support K = 2N users, but still achieve much better BER performance than a corresponding DS-CDMA or SDMA system using the conventional MMSE-MUD to support K = N users, where N denotes the spreading factor of DS-CDMA or the number of receive antennas of SDMA. I. INTRODUCTIONIn multiuser detection the optimum maximum a-posteriori (MAP) and ML MUDs [1][2][3] are capable of achieving the optimum BER performance that is close to the single-user BER bound. However, the complexity of these optimum MUDs is exponentially proportional to the number of users supported, which becomes extreme even when a moderate number of users are considered. Consequently, the application of the optimum MUDs in practice is limited. For this sake, research efforts have been put on finding the suboptimum solutions with practical complexity for the MAP or ML MUD problems, since the invention of the optimum MUDs [1,2]. In general, the suboptimum MUDs towards the optimum MUD problems can be divided into two classes. The first class aim at designing efficient search or non-search algorithms, such as those summarized in [4] and [5], in order to find approximate solutions for the optimum MUDs. Despite significant complexity reduction, however, these suboptimum algorithms either are still too complex to be implemented or achieve much worse BER performance than the optimum MUDs [5].The second class of suboptimum MUDs do not solve directly the optimum MUD problems. Instead, they approximate the optimum MUD problems by some suboptimum MUD problems that can be solved with lower complexity. This second class of suboptimum MUDs include typically the various types of decision feedback or interference cancellation (IC) assisted MUDs, such as those studied in [4,[6][7][8][9]. The BER performance of the conventional IC-aided MUDs is usually much worse than that of the optimum MUDs, as shown, e.g., in [3,4,6], due to the severe error propagation. In comparison with the conv...

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Speed and Accuracy Comparison of Techniques for Multiuser Detection in Synchronous CDMA

Cited by 32 publications

References 27 publications

A Low-Complexity High-Performance Preprocessing Algorithm for Multiuser Detection Using Gold Sequences

A Low-Complexity High-Performance Preprocessing Algorithm for Multiuser Detection Using Gold Sequences

Non Iterative Algorithm for Multi-user Detection in DS-CDMA System: An Enhanced Harmony Search Algorithm

Receiver Multiuser Diversity Aided Multi-Stage MMSE Multiuser Detection: A Low-Complexity Detector Fast-Converging to the Optimum

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