OFDM FOR WSNS USING CONTINUOUS PHASE MODULATION WITH FRS INTERLEAVER

Fatma H. El-Fouly, Rabie A. Ramadan, and Salah A. Aly

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Keywords

WSN, CPMOFDM, FRS interleaver, PAPR

Abstract

Since wireless sensor networks (WSNs) are characterized by a multipath fading environment, which causes a significant degradation in terms of both network reliability and data rate, the use of orthogonal frequency division multiplexing (OFDM) as a modulation technique is highly needed which is the newest contender against other modulation schemes that provides high quality of service and data rate. The real problem for OFDM implementation in WSNs is the peak to average power ratio (PAPR) of the OFDM signal, which requires highly linear power amplifiers to avoid excessive intermodulation distortion. This is not compatible with the energy conservation which is the major constraint for the design of WSNs. By utilizing continuous phase modulation (CPM) in OFDM system, the PAPR can be effectively reduced to 0 dB. In this paper, we propose to utilize helical interleaving scheme for continuous phase modulation–based orthogonal frequency-division multiplexing (CPM-OFDM) systems. In addition, based on our study to many of the interleavers, we proposed a new interleaver, FRS, that can break the burst channel errors and take the benefits of the previously proposed interleavers, and hence a better bit error rate (BER) performance can be achieved. The proposed system combines the advantages of frequency diversity and power efficiency from CPM-OFDM and performance improvement from new interleaving. Through simulation, the BER performance of the CPM-OFDM system with and without new interleaving is evaluated. In addition, the overall complexity of FRS interleaver compared to helical and 2D-prime interleavers in terms of hardware requirements is evaluated.

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