Deterministic Formulization of SNR for Wireless Multiuser DS-CDMA Networks

📝 Abstract

Wireless Multiuser receivers suffer from their relatively higher computational complexity that prevents widespread use of this technique. In addition, one of the main characteristics of multi-channel communications that can severely degrade the performance is the inconsistent and low values of SNR that result in high BER and poor channel capacity. It has been shown that the computational complexity of a multiuser receiver can be reduced by using the transformation matrix (TM) algorithm [4]. In this paper, we provide quantification of SNR based on the computational complexity of TM algorithm. We show that the reduction of complexity results high and consistent values of SNR that can consequently be used to achieve a desirable BER performance. In addition, our simulation results suggest that the high and consistent values of SNR can be achieved for a desirable BER performance. The performance measure adopted in this paper is the consistent values of SNR.

💡 Analysis

Wireless Multiuser receivers suffer from their relatively higher computational complexity that prevents widespread use of this technique. In addition, one of the main characteristics of multi-channel communications that can severely degrade the performance is the inconsistent and low values of SNR that result in high BER and poor channel capacity. It has been shown that the computational complexity of a multiuser receiver can be reduced by using the transformation matrix (TM) algorithm [4]. In this paper, we provide quantification of SNR based on the computational complexity of TM algorithm. We show that the reduction of complexity results high and consistent values of SNR that can consequently be used to achieve a desirable BER performance. In addition, our simulation results suggest that the high and consistent values of SNR can be achieved for a desirable BER performance. The performance measure adopted in this paper is the consistent values of SNR.

📄 Content

Abstract—Wireless Multiuser receivers suffer from their relatively higher computational complexity that prevents widespread use of this technique. In addition, one of the main characteristics of multi-channel communications that can severely degrade the performance is the inconsistent and low values of SNR that result in high BER and poor channel capacity. It has been shown that the computational complexity of a multiuser receiver can be reduced by using the transformation matrix (TM) algorithm [4]. In this paper, we provide quantification of SNR based on the computational complexity of TM algorithm. We show that the reduction of complexity results high and consistent values of SNR that can consequently be used to achieve a desirable BER performance. In addition, our simulation results suggest that the high and consistent values of SNR can be achieved for a desirable BER performance. The performance measure adopted in this paper is the consistent values of SNR.

Keywords—Computational complexity, DS-CDMA, wireless multiuser receivers, signal to noise ratio
I. INTRODUCTION From the design standpoint, for a given modulation and the coding scheme there is a one to one correspondence between the bit error rate (BER) and the signal-to-noise ratio (SNR). From the user standpoint, SNR is not the favorite criterion for the performance evaluation of digital communication links, because the user measures the quality of a system by the number of errors in the received bits and prefers to avoid the technical detail of modulation or coding. However, using received SNR rather than BER will allow us to relate our performance criteria to the required transmitted power, which is very important for battery-operated wireless operations. Using SNR rather than BER has two advantages. First, SNR is the criterion used for accessing both digital and analog modulation techniques. Second, SNR is directly related to the transmitted power, which is an important design parameter.
A significant amount of efforts have been made in order to achieve high values of SNR [3, 5]. However, none of these methods relate the complexity of multiuser receivers for achieving high SNR values. On the other hand, the TM algorithm is a low complexity, but synchronous transmission technique that is able to reduce the number of computations performs by a multiuser receiver for signal detection [4]. The TM algorithm therefore provides fast multiuser signal detection which can be further used to achieve high SNR values. The contribution of this research work is the quantification of SNR using the TM algorithm proposed by Rizvi et. [4]. At high SNR values, the error rate for multi channel can be reduced as well the capacity of the channel can be well approximated.
Multiuser receivers can be categorized in the following two forms: optimal maximum likelihood sequence estimation (MLSE) receivers and suboptimal linear and nonlinear receivers. Non-linear multiuser receiver involves the estimation and reconstruction of MAI [6] seen by each user with the objective of canceling it from the received signal. The two well known implementations of this mechanism are SIC and PIC. In interference cancellation, MAI is first estimated and then subtracted from the received signal [1, 7]. On the other hand, linear multiuser receivers apply a linear transformation to an observation vector, which serves as soft decision for the transmitted data. Recently, Ottosson and Agrell [2] proposed a new ML receiver that uses the neighbor descent (ND) algorithm. They implemented a linear iterative approach using the ND algorithm to locate the region where the actual observations belong. The linearity of their iterative approach increases noise components at the receiving end. Due to the enhancement in the noise components, the SNR and BER of ND algorithm is more affected by the MAI. Table 1, reported from [8], highlights the assumed knowledge for the computational complexity of a CDMA based multiuser receiver. Table I shows that different receivers distinguish themselves with respect to the requirement of the desired knowledge as well as the implementation complexity.
Verdu [1] proposed the optimum multiuser detector for asynchronous systems. The complexity of multiuser Syed S. Rizvi and Khaled M. Elleithy Computer Science and Engineering Department University of Bridgeport Bridgeport, CT 06601 {srizvi, elleithy}@bridgeport.edu Aasia Riasat Department of Computer Science Institute of Business Management Karachi, Pakistan 78100 aasia.riasat@iobm.edu.pk

Deterministic Formulization of SNR for Wireless Multiuser DS-CDMA Networks (IJCSIS) International Journal of Computer Science and Information Security Vol. 3, No. 1, 2009 25

receiver grows exponentially in an order of O (2)K, where K is the number of active users. Recently, [2] proposed a ML receiver that uses the nei

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