A Digital Phase Locked Loop based System for Nakagami -m fading Channel Model

Abstract

The modified structure of a Digital Phase Locked Loop (DPLL) based systems for dealing with Nakagami-m fading is proposed here. The emphasis of the work is to generate input signal under various fading conditions with certain modulation transmitted through Nakagami-m channels and to evaluate the performance of the proposed DPLL in terms of Bit Error Rate (BER). Statistical characteristics of the faded input signal have been evaluated in terms of Probability Distribution Function (PDF), Level Crossing Rate (LCR) and Average Fade Duration (AFD). A sixth order Least Square Polynomial Fitting (LSPF) block and Roots Approxiator (RA) for better phase-frequency detection have been implemented as a replacement of Phase Frequency Detector (PFD) and Loop Filter (LF) of a traditional DPLL, which has helped to attain optimum performance of DPLL. The results of simulation of the proposed DPLL with Nakagami -m fading and QPSK modulation shows that the proposed method provides better performance than existing systems of similar type. Keywordsdigital phase locked loop, numerically controlled oscillator, nakagami -m fading channels, least square polynomial fitting filter, level crossing rate and average fade duration.

Carrier and symbol recovery using Digital Phase Locked Loop in severely faded Nakagami-m channels

“…The modified structure of a Digital Phase Locked Loop (DPLL) based carrier detection systems for dealing with Nakagami-m fading has already been proposed [1]. BER performance of the DPLL under varied fading conditions using Nakagami -m fading model, QPSK modulation and uncoded channel have been reported to be comparable to the performance of the existing systems of similar type.…”

“…It has two inputs, the frequency count of local reference signal and the other one is the incoming input signal. We have found that the sixth order polynomial fitting can generate a good estimate of the QPSK modulated sinusoid signal under effect of additive noise and multipath path fading channel [1,2].…”

A Parallelized Phase-Frequency Detector based Modified LSPF-DPLL for Wireless Communication – Comparative Study with Modified LSPF-DPLL

“…Rayleigh and Rician fading models provide accurate estimates of the wireless fading environment prevelant in urban, sub-urban and rural areas [5,7]. The proposed Parallel PFD based modified DPLL system is tested under degraded effects of Rayleigh and Rician fading.…”

“…where a k is the gain in the k th path, Ȧ c is the angular carrier frequency for transmission, Ȧ dk is the Doppler Frequency due to relative motion in between the transmitter and receiver for k th path and k is the random phase for the k th path [2,5].…”

“…The NCO determines the accurate phase value using the lookup information of dibit-phase mapper. The accurate phase is further mapped to the correct dibits using the phasedibit mapper to reduce the need for complicated branched QPSK demodulation as suggested in [2,3,5].…”