Abstract
Orthogonal Frequency Division Multiplexing (OFDM) is the one of the most preferred multiplexing technique for realizing high-speed wireless communication, like Long Term Evolution (LTE) and LTE-Adv. In the era of digital wireless communication, applications of wavelet theory have been favorably applied in many areas of signal processing. Orthogonality, flexible time-frequency analysis, and the ability to characterize signals accurately have attracted the attention of the telecommunication community to use wavelet as a basis function for OFDM. In this paper, discrete wavelet transform (DWT) has been proposed as an alternative signal analysis with multiple merits such as support high-speed applications, immune to distortion, wavelet diversity, better error performance, and efficient bandwidth utilization. A simulative analysis of various wavelets, at different modulation techniques, over OFDM has been presented to demonstrate the improvement in BER performance. Further, in accordance with the LTE parameterization over 1.25 MHz band, the performance of wavelet-based OFDM (WOFDM) is found significantly higher in terms of maximum achievable data rate and system spectral efficiency.
Highlights
Orthogonal Frequency Division Multiplexing (OFDM) distributes the offered spectrum among multiple subcarriers where each subcarrier gets modulated by information signal stream to efficiently utilize available bandwidth [1, 2]
One radio frame is divided into two equal portions of Time Division Duplex (TDD) frames (5 ms each) where each half portion of the frame is structured with 8 slots of duration 0.5 m, and one subframe consists of three special fields related to the guard period (GP), downlink pilot time slot (DwPTS), and uplink pilot time slot (UpPTS)
BER performance of the standard OFDM system is evaluated against the wavelet-based OFDM (WOFDM) system to analyze the performance improvement
Summary
OFDM distributes the offered spectrum among multiple subcarriers where each subcarrier gets modulated by information signal stream to efficiently utilize available bandwidth [1, 2]. DWT can be the best alternative to the Discrete Fourier Transform (DFT) based signal analysis for OFDM system, with multiple advantages such as high energy consumption, compact support, multiresolution analysis in frequency-time domain, interference immunity, better phase linearity, no CP requirement, flexibility to choose suitable wavelet, and wavelet diversity [5]. High-speed data transmission support, and MIMO compatibility make OFDM a preferred access. Wavelet-based OFDM systems are spectrum efficient as they do not seek CP to restrict ISI. A quantitative analysis of maximum achievable data rate and spectral efficiency for WOFDM is performed with different modulation levels at 1.25 MHz LTE spectrum band. The high PAPR and related loss allied with OFDM leads to a search for an alternative low power consumption technique for LTE uplink transmission. The Home Subscriber Server (HSS) retains the user data and MME identification with which it is registered
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