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

Abstract

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...

Incremental gradient algorithm for multiuser detection in multi-carrier DS-CDMA system under modulation schemes

“…The proposed IGD MMSE MUD has 33.3% improvement for detecting [23] In fig. 7, the BER for different detection techniques has been compared with the proposed with the number of users.…”

“…The enhanced harmony search [23] algorithm is used for MUD in DS-CDMA system. The updating of harmony memory depends on the operation random and mean, and it reduced the complexity, bit error rate and user interference.…”