Wideband Code Division Multiple Accesses: Comparative Performance Analysis of digital Modulation Techniques for Enhanced Data Capacity
Kebiru Abu1 and Imonigie Arnold O.2
1Department of Electrical Engineering, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria
2Department of Electrical/Electronic Engineering Technology, Auchi Polytechnic, Auchi, Edo State, Nigeria
Abstract: This research focused on the comparative performance analysis of Quadrature Amplitude Modulation (QAM) and Quadrature Phase Shift Keying (QPSK) modulation techniques employed in W-CDMA system. Site investigation was conducted and the Received Signal Strength (RSS) measurement taken. From the RSS measurement, the path loss was evaluated and was used to estimate two Quality of Service (QoS) parameters – Signal-to-Noise Ratio (SNR) and the Bit Error Rate (BER) of the modulation techniques under study. These parameters were used to characterize the modulation techniques upon which a comparative analysis was obtained to achieve maximum data throughput consideration. The result of the analysis revealed that as SNR decreases, errors increase. The average estimated SNR of QPSK was slightly greater showing 15.89dB (50.4%) against 15.64dB (49.6%) for QAM, giving rise to why the bit error rate of QAM technique was higher than QPSK. In all, the research revealed that QAM offered higher coding rate which helps to sustain better data capacity and throughput. QPSK on the other hand gave an improved BER performance. From these developments, network designers usually make a tradeoff between spectral efficiency which QAM offers and improved BER performance by QPSK. Modulation scheme implemented therefore in any form of wireless network affects the BER performance which in turn affects the data rate as well as the throughput of the communicating devices.
Keywords: QPSK, QAM, throughput, Modulation, BER, WCDMA
I. INTRODUCTION
Wideband Code Division Multiple Access (W-CDMA) has been chosen as a basic radio access technology for Universal Mobile Telecommunications System/International Mobile Telecommunication 2000 (UMTS/IMT-2000) to support multimedia services. In the second generation (2G) networks where Gaussian Minimum Shift Keying (GMSK) modulation scheme is widely used in Global System for Mobile communication (GSM), it has been observed that such modulation scheme could only transmit data rate of 1 bit per symbol and so not suitable for the next generation communication system. Also while voice-services have dominated the 2G cellular traffic, data services are predicted to become a major part of global